Celina: April 2008

• Topic One chapters 13 and 14

• Chapter 13
• Overview of the nervous system

o There are 2 main parts to the nervous system
 Central Nervous System (CNS)
• Brain
• Spinal Cord
 Peripheral Nervous System
• Nerves outside the CNS
o There are 3 specific functions
 Receiving sensory input
 CNS performs integration
 CNS generates motor output
o Nervous Tissue
 Contains 2 types of cells

• Compendium Review Unit #3
• Neurons
o Cells that transmit nerve impulses between parts of the nervous system
• Neuroglia
o Support and nourish neurons
o Neuron Structure
 3 types of neurons
• Sensory neurons
o Takes nerve impulses (messages) from a sensory receptor to the CNS
 Sensory receptor is a special structure that detects changes in the environment.
• Interneuron
o Is completely within the CNS, they receive input from sensory neurons and from other interneurons in the CNS.
o After receiving the information they sum it all up before translating it to motor neurons
• Motor Neuron
o Takes nerve impulses away from the CNS to an effector (muscle fiber or gland)
 Effectors carry out our responses to environmental changes, external and internal.
o Myelin Sheath

 Is the protective cover over the axons.
 Is formed by neuroglia cells called Schwann Cells
• Schwann Cells contain myelin in their plasma membrane
• Develops when these cells wrap themselves around an axon many times.
• Each neuroglia cell only covers a part of the axon, the gaps where there is no cover is called nodes of Ranvier.
 Long Axons have a myelin sheath, but short axons do not.
 Myelin gives nerve fibers their white glistening appearance and is also an insulator.
 The myelin sheath is important to nerve regeneration within the PNS.
• If an axon is severed, the myelin sheath remains and serves as a passageway for new fiber growth.
o The Nerve Impulse
 Nerve impulses convey information within the nervous system.
• Nerve impulse is studied by using excised axons and a voltmeter to measure voltage.
o The voltmeter allows measurement of the potential difference between 2 sides of the axonal membrane
 Resting potential
• Is when the axon is not conducting an impulse.
• The inside of the neuron is more negative than the outside
• Resting potential correlates to a difference in ion distribution on either side of the axonal membrane
o More Na+(sodium ions) outside the axon
o More K+ (potassium ions) inside the axon
o Sodium-Potassium Pump created the unequal distribution of these ions.
 Actively transports Na+ out of the axon
 Actively transports K+ into the axon
 The membrane is permeable to K+ but not to Na+, causing there to always be more positive ions outside the membrane than inside.
 Action Potential
• Is a rapid change in polarity across an axonal membrane as the nerve impulse occurs.
• If a stimulus causes the axonal membrane to depolarize to a certain level, called threshold, an action potential occurs in an all-or-none manner.
• Action potential requires 2 types of gated channel proteins in the membrane
o Sodium Gates Open
 When action potential occurs, gates of sodium channels open first
 Na+ flows into the axon.
 This causes a depolarization because the charge inside the axon changes from negative to positive.
o Potassium Gates Open
 Second, the gates of the potassium channels open
 K+ flows to outside the axon.
 This causes a repolarization because the inside of the axon resumes a negative charge as K+ exits he axon.
 Visualizing an Action Potential
• After an action potential has passed by, the sodium-potassium pump restores the resting potential by moving the potassium back to the inside and sodium back to the outside.
o Propagation of an Action Potential
 Action potentials are self-propagating; each action potential generates another along the length of an axon.
 When an axon does not have a myelin sheath, the action potential at one locale stimulates an adjacent part of the axon’s membrane to produce an action potential.
 In axons that have a myelin sheath, an action potential at one ranvier node causes an action potential at the next node.
o The Synapse
 Every axon branches into many fine endings, each is tipped by a small swelling called an axon terminal.
 Each axon terminal lies very close to either the dendrite or the cell body of another neuron
 This region of close proximity is called a synapse
• At a synapse, a small gap called the synaptic cleft separates the sending neuron from the receiving neuron.
 Transmission across a synapse is carried out by molecules called neurotransmitters.
 These events occur:
• Nerve impulses traveling along an axon reach an axon terminal.
• Calcium ions enter the terminal, and they stimulate synaptic vesicles to merge with the sending membrane
• Neurotransmitter molecules are released into the synaptic cleft, and they diffuse across the cleft to the receiving membrane, where they bind with specific receptor proteins.
 Neurotransmitter Molecules
• More than 100 substances are known or suspected to be neurotransmitters, some common ones are:
o Acetylcholine and norepinephrine
 Active in both the CNS and PNS
 Norepinephrine excites smooth muscle in the CNS
 Acetylcholine in the PNS; excites skeletal muscle and inhibits cardiac muscle.
o GABA (gamma aminobutyric acid)
 Is an abundant inhibitory neurotransmitter in the CNS
o Serotonin
 Involved in thermoregulation, sleeping, emotions, and perception
• The Central Nervous System
o The spinal cord and the brain make up the CNS
o Sensory information is received and motor control is initiated.
o The Spinal Cord

 Extends from the base of the brain through a large opening in the skull called the foramen magnum and into the vertebral canal formed by openings in the vertebrae.
 Structure of the spinal cord
• Spinal nerves project from the cord between the vertebrae that make up the vertebral column.
• Central canal contains cerebrospinal fluid, along with the meninges that protect the spinal cord.
• The gray matter is centrally located and shaped like the letter H.
o This is where portions of the sensory neurons and motor neurons are found, interneurons that communicate with these 2 types of neurons are also found there.
• Dorsal root contains sensory fibers entering the gray matter
• Ventral roots contains motor fibers exiting the gray matter
• The dorsal and ventral roots join before the spinal nerve leaves the vertebral canal as a mixed nerve
• White matter occurs in areas around the gray matter
o It contains ascending tracts taking information to the brain and descending tracts taking info from the brain.
 Functions of the Spinal Cord
• Provides a means of communication between the brain and the peripheral nerves that leave the cord.
• Sensory receptors generate nerve impulses that pass through sensory fibers to the spinal cord and up ascending tracts to the brain.
• Gate Control Theory of Pain:
o The tracts in the spinal cord have ”gates,” and these “gates” control the flow of pain messages from the peripheral nerves to the brain.
o Depending on how the gates process a pain signal, the pain message can be allowed to pass directly to the brain or it can be prevented from reaching the brain.
o When the brain initiates voluntarily control over our limbs, motor impulses originating in the brain pass down descending tracts to the spinal cord and out to our muscles by way of motor fibers
o If the spinal cord is severed, we suffer a loss of sensation and a loss of voluntary control.
 If the cut occurs in the thoracic region, the lower body and legs are paralyzed, known as paraplegia.
 If the injury is in the neck region, all four limbs are usually affected, known as quadriplegia.
o Reflex Actions
 A stimulus causes sensory receptors to generate nerve impulses that travel in sensory axons to the spinal cord
 Interneurons integrate the incoming data and relay signals to motor neurons
 A response to the stimulus occurs when motor axons cause skeletal muscles to contract.
 Each interneuron in the spinal cord has synapses with many other neurons, they send signals to several other interneurons and motor neurons.
o The Brain

 The Cerebrum
• Also referred to as the Telencephalon
• Is the larges part of the brain.
• The last center to receive sensory input and carry out integration before commanding voluntary motor responses
• It communicates with and coordinates the activities of the other parts of the brain.
• Cerebral Hemispheres
o 2 halves
 Left Cerebral Hemisphere
 Right Cerebral Hemisphere
o A deep groove called the longitudinal fissure divides the left and right cerebral hemispheres.
o Shallow grooves called sulci divide each hemisphere into lobes
 Frontal Lobe
• Is the most ventral of the lobes
• Located directly behind the forehead
 Parietal lobe
• Dorsal to the frontal lobe
 Occipital Lobe
• Dorsal to the parietal lobe
• Located at the real of the head
 Temporal lobe
• Inferior to the front and parietal lobes
• At the temple and the ear
• The Cerebral Cortex
o Is a thin but highly convoluted outer layer of gray matter that covers the cerebral hemispheres.
o Is the region of the brain that accounts for:
 Sensation
 Voluntary movement
 All the thought processes we associate with consciousness
• Primary Motor and Sensory Areas of the Cortex
o Primary Motor Area
 Located in the frontal lobe just before the central sulcus.
 Voluntary commands to skeletal muscles begin in the primary motor area, each part of the body is controlled by a certain section
o Primary Somatosensory Area
 Is located dorsal to the central sulcus in the parietal lobe
 Sensory information from the skin and skeletal muscles arrives here, where each part of the body is sequentially represented
• Primary taste area
o Accounts for taste sensations
• Primary visual area
o In the occipital lobe receives information from our eyes
• Primary auditory area
o In the temporal lobe receives information from our ears
• Primary olfactory area
o Is for smell, located in the temporal lobe
o Association Areas
 Located in places where integration occurs
 Ventral to the primary motor area is a pre-motor area
• The pre-motor area organizes motor functions for skilled motor activities, such as walking and talking at the same time
• The primary motor area then sends signals to the cerebellum, which integrates them.
o Processing Centers
 Processing centers of the cortex receive information from the other association areas and perform higher-level analytical functions
 The prefrontal area, an association area in the frontal lobe, receives information from other association areas and uses this information to reason and plan our actions
o Central White Matter
 Most of the remaining cerebrum is composed of white matter
 The Diencephalon
• Is a region that encircles the third ventricle
• Hypothalamus and the thalamus are located here
o Hypothalamus forms the floor of the third ventricle
 Integrating center that regulates hunger, sleep, thirst, body temperature, and water balance,
 Controls the pituitary gland, is the link between the nervous and endocrine system
o Thalamus consists of 2 masses of gray matter located in the sides and roof of the third ventricle.
 Is on the receiving end for all sensory input except smell
 Visual, auditory, and somatosensory information arrives at the thalamus via the cranial nerves and tracts from the spinal cord.
 The thalamus integrates this information and sends it on to the appropriate portions of the cerebrum.
 The Cerebellum
• Lies under the occipital lobe of the cerebrum and is separated from the brain stem by the fourth ventricle
• Made up of 2 portions that are joined by a narrow median portion
• Receives sensory input from the eyes, ears, joints, and muscles about the present position of body parts, and receives motor output from the cerebral cortex about where these parts should be located.
• After integrating this information, the cerebellum sends motor impulses by way of the brain stem to the skeletal muscles.
 The Brain Stem
• Contains the midbrain, the pons, and the medulla oblongata
o Midbrain
 Acts as a relay station for tracts passing between the cerebrum and the spinal cord or cerebellum.
 Has reflex centers for visual, auditory, and tactile responses
o Pons
 Contains bundles of axons traveling between the cerebellum and the rest of the CNS.
 Functions with the medulla oblongata to regulate breathing rate and has reflex centers concerned with head movements in response to visual and auditory stimuli
o Medulla Oblongata
 Contains a number of reflex centers for regulating heartbeat, breathing, and blood pressure.
 Contains reflex centers for vomiting, coughing, sneezing, hiccupping, and swallowing.
• The Limbic System and Higher Mental Functions
o Limbic System
 An evolutionary ancient group of linked structures deep within the cerebrum that is a functional grouping rather than an anatomical one
 It blends primitive emotions and higher mental functions into a united whole.
 There are two structures within the limbic system
• The amygdala
o Can cause experiences to have emotional overtones
o Creates the sensation of fear.
• The Hippocampus
o Believed to play a crucial role in learning and memory
 Acts as an information gateway during the learning process, determining what information about the world is to be sent to memory, and how the information is to be encoded and stored by other regions in the brain
o Higher Mental Functions
 Types of memory
• Short-term memory
• Long-term memory
• Semantic memory: number, words
• Episodic memory: persons, events
• Skill Memory: involved in performing motor activities
 Long-Term Memory Storage and Retrieval
• Long-term memories are apparently stored in bits and pieces throughout the sensory association areas of the cerebral cortex.
• The Peripheral Nervous System
o Nerves that lie outside the CNS
o 2 types
 Cranial Nerves
• Attached to the brain
• 12 pairs
 Spinal Nerves
• Emerge in 31 pairs from either side of the spinal cord.
o Somatic System
 Nerves in the somatic system serve the skin, skeletal muscles, and tendons.
 Includes nerves that take sensory information from external sensory receptors to the CNS and motor commands away from the CNS to the skeletal muscles.
 Automatic responses to a stimulus in the somatic system are called reflexes
• The Reflex Arc
o The path of a reflex that involves only the spinal cord.
o Sensory receptors in the skin generate nerve impulses that move along sensory fibers through the dorsal-root ganglia toward the spinal cord.
o Sensory neurons that enter the cord dorsally pass signals on to many interneurons.
o Nerves impulses travel along motor fibers to an effector, which brings about a response to the stimulus.
o The whole series of responses occurs because some of the interneurons involved carry nerve impulses to the brain.
o Autonomic System
 Located in the PNS
 Regulates the activity of cardiac and smooth muscles and glands
 Divided into the sympathetic and parasympathetic divisions.
• Shared features are:
o They function automatically and in an involuntary manner
o They innervate all internal organs
o They utilize 2 neurons and one ganglion for each impulse
• Sympathetic division
o Important to fight or flight situations
o Accelerates the heart beat and dilates the bronchi
• Parasympathetic Division
o Promotes all the internal responses we associate with a relaxed state

• Chapter 14
• Sensory Receptors and Sensations

o Sensory Receptors
 Are dendrites that are specialized to detect certain types of stimuli
 Exteroceptors
• Sensory receptors that detect stimuli from outside the body
• Ex: those that result in taste, smell, vision, hearing, and equilibrium
• Are not directly involved in homeostasis and continually send messages to the central nervous system regarding environmental conditions
 Interoceptors
• Receive stimuli from inside the body
• Ex: pressoreceptors respond to changes in blood pressure, osmoreceptorsdetect changes in water-balance
• Are directly involved in homeostasis and are regulated by a negative feedback mechanism
o Types of Sensory Receptors
 Chemoreceptors
• Respond to chemical substances in the immediate vicinity
• Ex: taste, smell,
• Pain Receptors
o Are a type of chemoreceptor, they are naked dendrites that respond to chemicals released by damaged tissues
 Photoreceptors
• Respond to light energy
• Our eyes contain photoreceptors that are sensitive to light rays and provide us with a sense of vision.
 Mechanoreceptors
• Are stimulated by mechanical forces, which most often result in pressure of some sort.
 Thermoreceptors
• Are located in the hypothalamus and skin and are stimulated by changes in temperature.
o Warmth receptors respond when temperatures rise
o Cold receptors respond when temperatures lower
o How Sensation Occurs
 Sensory receptors respond to environmental stimuli by generating nerve impulses.
 When nerve impulses arrive at the cerebral cortex of the brain, sensation, which is the conscious perception of stimuli, occurs.
 All sensory receptors initiate nerve impulses; the sensation that results depends on the part of the brain receiving the nerve impulses
• Proprioceptors and Cutaneous Receptors
o Proprioceptors
 Are mechanoreceptors involved in reflex actions that maintain muscle tone, and thereby the body’s equilibrium and posture.
 They help us know the position of our limbs in space by detecting the degree of muscle relaxation, the stretch of tendons, and the movement of ligaments.
 Muscle spindles increase the degree of muscle contraction
 Golgi tendon organs decrease the degree of muscle contraction
o Cutaneous Receptors
 Are located in the dermis, making the skin sensitive to touch, pressure, pain, and temperature.
 There are 3 types of receptors that are sensitive to fine touch
• Meissner corpuscles
o Along with Krause end bulbs are concentrated in the fingertips, the palms, the lips, the tongue, the nipples, the penis, and the clitoris.
• Merkel disks
o Located where the epidermis meets the dermis
• Root Hair Plexus
o Is a free nerve ending that winds around the base of a hair follicle and fires if the hair is touched.
 2 types of receptors that are sensitive to pressure
• Pacinian corpuscles
o Are onion shaped receptors that lie deep inside the dermis.
• Ruffini Endings
o Are encapsulated by sheaths of connective tissue and contain lacy networks of nerve fibers.
o Pain Receptors
 Nociceptors
• Pain receptors for internal organs that are sensitive to chemicals released by damaged tissues.
• When inflammation occurs, because of mechanical, thermal, or electrical stimuli or toxic substances, cells release chemicals that stimulate pain receptors.
• Senses of Taste and Smell
o Taste and smell are chemical senses because their receptors are sensitive to molecules in the food we eat and the air we breathe.
o Chemoreceptors are plasma membrane receptors that bind to particular molecules. They are divided into 2 types:
 Those that respond to distant stimuli
• Olfactory cells act from a distance
 Those that respond to direct stimuli
• Taste cells act directly
o Sense of Taste
 Taste buds are primarily located on the tongue
 Four Primary types of taste
• Sweet
• Sour
• Salty
• Bitter
• A fifth taste called umami may exist for certain flavors of:
o Cheese
o Beef broth
o Some sea food
 Certain regions of the tongue are more sensitive to different types of taste.
 How the Brain Receives Taste Information
• Taste buds open at a taste pore.
• They have supporting cells and a number of elongated taste cells that end in microvilli.
• When molecules bind to receptor proteins of microvilli nerve impulses are generated in sensory nerve fibers that go to the brain.
• When they reach the gustatory (taste) cortex, they are interpreted as particular tastes.
o Sense of Smell
 80-90% of what we perceive as taste is actually due to the sense of smell.
 Our sense of smell depends on 10-20 million olfactory cells located within olfactory epithelium high in the roof of the nasal cavity.
 How the Brain receives Odor Information
• Each olfactory cell has one out of several hundred different types of receptor proteins.
• Nerve fibers from like olfactory cells lead to the same neuron in the olfactory bulb, an extension of the brain.
• An odor contains many odor molecules, which activate a characteristic combination of receptor proteins.
• An odor’s signature in the olfactory bulb is determined by which neurons are stimulated.
• When neurons communicate this information via the olfactory tract to the olfactory areas of the cerebral cortex.
• Sense of Vision
o Anatomy and Physiology of the Eye

 Is an elongated sphere about 2.5 cm in diameter
 Has 3 Layers
• The Sclera
o The outer layer
o Is white and fibrous
o Except for the cornea, which is made of transparent collagen fibers
• The Choroid
o The middle, thin darkly pigmented layer
o Is vascular and absorbs stray light rays that photoreceptors have not absorbed.
o Toward the front it becomes the iris.
 Regulates the size of the pupil
 Pupil is a hole in the center of the iris that lets light into the eyeball.
o Behind the iris the choroids thickens and becomes ciliary body
 Controls the shape of the lens for near and far vision
o The lens, divides the eye into 2 compartments
 The anterior compartment
• Is filled with a clear watery fluid called aqueous humor
• Located in front of the lens
 Posterior Compartment
• Located behind the lens
• Is filled with vitreous humor, a clear gelatinous material
• The Retina
o Located in the posterior compartment
o Contains photoreceptors called
 Rod Cell
• Very sensitive to light
• Do not see color
 Cone Cells
• Require bright light
• Sensitive to different wavelengths of light, giving us the ability to distinguish colors.
o Fovea centralis
 Region where cone cells are packed densely
 Light is normally focused here when we directly look at an object
o Optic Nerve
 Formed from sensory fibers in the retina
 Takes nerve impulses to the visual cortex
 Function of the Lens
• The cornea, assisted by the lens and humors, focuses images on the retina.
• Visual Accommodation
o Occurs for close vision
o The lens rounds up, in order to bring the image to focus on the retina.
o The ciliary muscle contracts, releasing tension on the suspensory ligaments, the lens rounds up due to the natural elasticity.
• Sense of Hearing
o The ear has 2 sensory functions:
 Hearing
 Balance
 The sensory receptors for both are located in the inner ear
 Each consists of hair cells with stereocilia that are sensitive to mechanical stimulation. They are mechanoreceptors
o Anatomy and Physiology of the Ear

 The ear has 3 divisions
• Outer
o Outer ear consists of the pinna and the auditory canal
• Middle
o Begins at the tympanic membrane and ends at a bony wall containing two small openings covered by membranes
 These openings are called the:
• Oval window
• Round window
o Three small bones are found between the tympanic membrane and the oval window. They are called the ossicles
 Malleus (hammer)
 Incus (anvil)
 Stapes (stirrup)
o The Eustachian Tube is an auditory tube that extends from the middle ear to the nasopharynx, it permits equalization of air pressure
• Inner
o Is filled with fluid
o Has three areas:
 Semicircular canals
• Concerned with equilibrium
 Vestibule
• Concerned with equilibrium
 Cochlea
• Concerned with hearing
o Auditory Pathway to the Brain
 Through the Auditory Canal and Middle Ear
• The process begins when sound waves enter the auditory canal.
• When a large number of waves strike the tympanic membrane, it moves back and forth ever so slightly.
• The malleus then takes the pressure from the inner surface of the tympanic membrane and passes it to the stapes.
• The stapes strikes the membrane of the oval window, causing it to vibrate; the pressure is passed to the fluid within the cochlea.
 From the Cochlea to the Auditory Cortex.
• Cochlea has 3 canals
o The cochlear canal
o The vestibular canal
o The tympanic canal
• When the stapes strikes the membrane of the oval window, pressure waves move from the vestibular canal to the tympanic canal across the basilar membrane.
• The basilar membrane moves up and down, and the stereocilia of the hair cells embedded in the tectorial membrane bend.
• Nerve impulses begin in the cochlear nerve and travel to the brain.
• When they reach the auditory cortex in the temporal lobe, they are interpreted as a sound.
• Sense of Equilibrium
o Rotational Equilibrium Pathway
 Mechanoreceptors in the semicircular canals detect rotational and angular movement of the head.
 The three semicircular canals are arranged so that there is one in each dimension of space
 The base of each of the three canals, called the ampulla, is slightly enlarged.
 Little hair cells, whose stereocilia are embedded within a gelatinous material cupula, are found within the ampullae.
 Because of the way the semicircular canals are arranged, each ampulla responds to head rotation in a different plane of space.
 As fluid within a semicircular canal flows over and displaces a cupula, the stereocilia of the hair cells bend, and the pattern of impulses carried by the vestibular nerve to the brain changes.
 The brain uses information from the hair cells within ampulla of the semicircular canals to maintain equilibrium through appropriate motor output to various skeletal muscles that can right our present position in space as need be.
o Gravitational Equilibrium Pathway
 The mechanoreceptors in the utricle and saccules detect movement of the head in the vertical or horizontal planes.
 The utricle and saccules are two membraneous sacs located in the inner ear near the semicircular canals.
 Both of these sacs contain little hair cells, whose stereocilia are embedded within a gelatinous material called an otolithic membrane. Calcium carbonate granules, otoliths, rest on this membrane.
 When the body is still, the otoliths in the utricle and the saccules rest on the otolithic membrane above the hair cells
 When the head bends or the body moves in the horizontal and vertical planes, the otoliths are displaced and the otolithic membrane sags, bending the stereocilia of the hair cells beneath.
 If the stereocilia move toward largest stereocilium, called the kinocilium, nerve impulses increase in the vestibular nerve.
 If the stereocilia move away from the kinocilium, nerve impulses decrease in the vestibular nerve.
 The frequency of nerve impulses in the vestibular nerve indicates whether you are moving up or down.
 These data reach the brain, which uses them to determine the direction of the movement of the head at the moment.
 The brain uses this information to maintain gravitational equilibrium through appropriate motor output to various skeletal muscles that can right our present position in space as need be.

• Chapter 11
• Overview of Skeletal System

o Functions of the Skeleton
 The skeleton supports the body.
• Bones of the legs support the entire body when we are standing.
• The bones of the pelvic girdle support the abdominal cavity.
 The skeleton protects soft body parts.
• Bones of the skull protect the brain
• The rib cage protects the heart and lungs.
• The vertebrae protect the spinal cord.
 The skeleton produces blood cells
• All bones in the fetus have red bone marrow that produces blood cells
• Only certain bones in adults produce blood cells.
 The skeleton stores mineral and fat
 The skeleton, along with the muscles, permits flexible body movement.
o Anatomy of a Long Bone

 The diaphysis
• The shaft, or main portion of the bone
• Has a large medullary cavity
o Walls are composed of compact bone
o Lined with a thin, vascular membrane, and is filled with yellow bone marrow that stores fat.
 The epiphyses
• Expanded region at the end of a long bone
• Composed largely of spongy bone that contains red bone marrow
• Coated with a thin layer of hyaline cartilage, called articular cartilage
 Periosteum
• A layer of fibrous connective tissue covering the long bone
• Contains blood vessels, lymphatic vessels, and nerves
• Is continuous with ligaments and tendons that are connected to a bone.
 Bone
• Compact Bone
o Highly organized and composed of tubular units called osteons.
• Spongy Bone
o Unorganized appearance
o It contains numerous thin plates called trabeculae, separated by unequal spaces
 Cartilage
• Not as strong as bone
• More flexible than bones
• Has no nerves
• Made to pad joints where the stresses of movement are intense.
• Three types of cartilage
o Hyaline Cartilage
 Firm and somewhat flexible
 The matrix is uniform and glassy
 Found at the ends of long bones, in the nose, at the end of the ribs, and in the larynx and trachea.
o Fibrocartilage
 Stronger than hyaline
 Able to withstand tension and pressure
 Found in the disks located between the vertebrae and in the cartilage of the knee.
o Elastic cartilage
 More flexible than hyaline cartilage
 Found in the ear flaps and the epiglottis
• Fibrous connective tissue
o Contains rows of cells called fibroblasts separated by bundles of collagenous fibers
o Makes up the ligaments that connect bone to bone.
o Makes up the tendons that connect muscles to a bone at joints (articulations).
• Bone Growth, Remodeling, and Repair
o Several different types of bone cells are involved in bone growth, remodeling, and repair.
 Osteoblasts
• Bone-forming cells
• They secrete the organic matrix of bone and promote the deposition of calcium salts into the matrix.
 Osteocytes
• Mature bone cells
• Derived from osteoblasts
• Maintain the structure of bone
 Osteoclasts
• Bone-absorbing cells
• They break down bone and assist in depositing calcium and phosphate in the blood.
o Bone Growth and Development
 Ossification
• The formation of bone.
 The bones of the skeleton form during embryonic development in 2 ways:
• Intramembranous Ossification
o Flat bones are examples of intramembranous Ossification.
o Bones develop between sheets of fibrous connective tissue.
o Cells derived from connective tissue cells become osteoblasts located in the ossification centers.
o Osteoblasts secrete the organic matrix of bone consisting of mucopolysaccharides and collagen fibrils.
o Calcification occurs when calcium salts are added to the organic matrix
o Osteoblasts promote calcification
o Ossification results in the trabeculae of spongy bone, spongy bone remains on the inside.
o Periosteum forms outside the spongy bone and osteoblasts, derived from the periosteum, carry out further ossification.
o Trabeculae form and fuse to become compact bone, which surrounds the spongy bone.
• Endochondral Ossification
o How most of the bones of the human skeleton are formed.
o Bone replaces cartilaginous models of the bones.
o Gradually, the cartilage is replaced by the calcified bone matrix that makes these bones capable of bearing weight.
• Epiphyseal Plates
o Have four layers
 Resting Zone
• Layer nearest the epiphysis
• Where cartilage remains
 Proliferating Zone
• Next to the resting zone
• Chondrocytes are producing new cartilage cells.
 Degenerating Zone
• The third layer
• The cartilage cells are dying off
 Ossification Zone
• Fourth layer
• Bone is forming
• Final Size of the Bones
o When epiphyseal plates close, bone length can no longer occur.
o The arms and legs of women close at about age 18.
o The arms and legs of men close at about age 20.
o Portions of other types of bones may continue until age 25.
o Hormones control the activity of the epiphyseal plate.
• Hormones Affect Bone Growth
o Several different hormones are involved in bone growth.
 Growth Hormone (GH)
• Directly stimulates growth of the epiphyseal plate, and bone growth in general.
 Thyroid Hormone
• GH would be ineffective if the metabolic activity of cells is not promoted.
• Thyroid Hormone promotes the metabolic activity of cells.
o Bone Remodeling and Its Role in Homeostasis
 Bone Remodeling
• The process of bone renewal to keep bones strong.
• Allows the body to regulate the amount of calcium in the blood.
• The blood calcium level is critical because:
o If calcium concentration is too high, neurons and muscle cells no longer function
o If calcium concentrations fall too low, convulsions occur.
• Bones absorb excess calcium if level is too high.
• Bones release calcium if level is too low.
o Bone Repair
 Is required after bone breaks or is fractured
 Fracture repair takes several months in a series of 4 steps:
• Hematoma
o After a fracture blood escapes from ruptured blood vessels and forms a hematoma in the space between the ends of the broken bone
o Happens within 6-8 hours.
• Fibrocartilaginous Callus
o Tissue repair begins
o Fibrocartilaginous callus fills the space between the ends of the broken bone for about 3 weeks.
• Bony Callus
o Osteoblasts produce trabeculae of spongy bone and convert the Fibrocartilage callus to a bony callus that joins the broken bones together.
o Lasts about 3-4 months.
• Remodeling
o Osteoblasts build new compact bone at the periphery, and osteoclasts absorb the spongy bone, creating a new medullary cavity.
• Bones of the Axial Skeleton
o Lies in the midline of the body.
o Consists of the skull, hyoid bone, vertebral column, and the rib cage.
o The Skull

 Formed by the cranium (braincase) and the facial bones.
 The Cranium
• Protects the brain
• Composed of eight bones
o Frontal bone
 Forms the forehead
o Parietal bones
 Extend to the sides
o Occipital bone
 Forms the base of the skull
o Temporal bone
 Has an opening that leads to the middle ear
o Sphenoid bone
 Extends across the floor of the cranium
 Completes the sides of the skull
 Contributes to forming the eye sockets
o Ethmoid bone
 Lies in front of the sphenoid
 Helps from the orbits and the nasal septum
 The Facial Bones
• Most prominent of the facial bones are:
o Mandible
 Lower jaw
 Only movable part of the skull
o The maxillae
 Forms the upper jaw and the anterior portion of the hard palate
o Palatine bones
 Make up the posterior portion of the hard palate and the floor of the nose.
o Zygomatic bones
 Cheekbone prominences
o Nasal bones
 Form the bridge of the nose
 The Hyoid Bone
• Only bone in the body that does not articulate with another bone.
• It is attached to the temporal bones by muscles and ligaments and to the larynx by a membrane
• Anchors the tongue and serves as the site for the attachment of muscles associated with swallowing.
 The Vertebral Column

• Consists of 33 vertebrae
• Have 4 curvatures that provide more resilience and strength for an upright posture.
• Types of vertebrae
o Cervical vertebrae
 Located in the neck
 First cervical vertebrae, called atlas, hold up the head.
 Second cervical vertebrae, called axis, allows a degree of rotation
o Thoracic Vertebrae
 Have long, thin, spinous processes and articular facets for the attachment of the ribs.
o Lumbar Vertebrae
o Sacral Vertebrae
 Five vertebrae fused together
o Coccyx (tailbone)
 Composed of four fused vertebrae
• Intervertebral Disks
o Located between the vertebrae
o Composed of fibrocartilage that acts as a kind of padding.
o They prevent the vertebrae from grinding against each other.
o They absorb shock caused by movements.
o Allows the vertebrae to move.
 The Rib Cage
• Also called the thoracic cage
• Composed of thoracic vertebrae, the ribs, and associated cartilages, and the sternum.
• Protects the heart and lungs
• The Ribs
o Flattened bone
o Originates at the thoracic vertebrae and proceeds toward the anterior thoracic wall.
o 12 pairs of ribs
 Connected directly to the thoracic vertebrae in the back.
 Upper 7 pairs connect to the sternum
• Referred to as the “true ribs”
 Next 3 ribs connect to the sternum by a common cartilage
• Referred to as the “false ribs”
 Last 2 pairs, are not attached to the sternum, they are attached to T12, the thoracic vertebrae
• Referred to as the “floating ribs”
• The Sternum
o Lies in the midline of the body
o Helps protect the heart and lungs
o Is a flat bone in the shape of a knife
o Composed of three bones
 Manubrium
• The handle
 The body
• The blade
 Xiphoid process
• The point of the blade
• Bones of the Appendicular Skeleton
o Composed of the bones within the pectoral and pelvic girdles and their attached limbs
 Pectoral girdle and upper limb are specialized for flexibility
 The pelvic girdle and lower limbs are specialized for strength
o The Pectoral Girdle and Upper Limb
 The body has a left and right pectoral girdles
• Each consists of:
o A scapula (shoulder blade)
o Clavicle (collarbone)
 Extends across the top of the thorax
 It articulates with the sternum and the acromion process of the scapula.
 The muscles of the arm and chest attach to the coracoid process of the scapula.
 The glenoid cavity of the scapula articulates with the head of the humorous.
• This allows the arm to move in almost any direction, but reduces stability.
 Components of the pectoral girdle
• Humorous
o The single long bone in the arm
o Has a smooth round head that fits into the glenoid cavity of the scapula
o On the shaft is a tuberosity that attaches the deltoid muscle
o The far end has 2 protuberances where the radius and ulna attach
• Radius
• Ulna
 The hand

• The wrist has 8 carpal bones
• 5 metacarpal bones
• The phalanges
o The bones of the fingers and the thumb
o The Pelvic Girdle and Lower Limb
 The pelvic girdle consists of 2 heavy, large coxal bones (hip bones)
 The pelvis
• Is a basin composed of the pelvic girdle, sacrum, and coccyx
• Bears the weight of the body
• Protects the organs within the pelvic cavity
• Serves as the place of attachment for the legs
 Each coaxl bone has 3 parts:
• The ilium
o The largest part
o Hips occur where it flares out
• The ischium
o Part that we sit on
o Has a posterior spine (ischial spine) for muscle attachment
• The pubis
o 2 pubic bones are joined together by a fibrocartilaginousjoint (the pubic symphysis)
o The male and female pelves differ from each other.
 The hip socket (acetabulum) occurs where these 3 bones meet
 The Femur (thighbone)
• The longest and strongest bone in the body
• The head of the femur articulates with the coxal bones at the acetabulum, and the short neck better positions the legs for walking
• Has 2 large processes
o The greater and lesser trochanters
 Places of attachment for thigh muscles, buttock muscles, and hip flexors.
• At its distal end there is a medial and lateral condyles that articulate with the tibia of the leg
o This is the region of the knee and the patella (kneecap)
• The fibula
o The more slender bone in the leg
o Has a head that articulates with the tibia and the distal lateral malleous that forms the outer bulge of the ankle.
 Each foot has an ankle, an instep, and five toes
• Has 7 tarsal bones
• A calcaneus (heel bone)
• Instep has 5 elongated metatarsal bones
• Bones of the toes are called phalanges.
• Articulations
o Bones are joined at the joints
 Classified as:
• Fibrous
o Are immovable
• Cartilaginous
o Connected by hyaline cartilage or fibrocartilage
o Slightly movable
• Synovial
o Move freely
o Filled with synovial fluid, a lubricant for the joint
o Elbow and knee joints
o Also called hinge joints

• Chapter 12
• Overview of Muscular System

o Types of muscles
 Smooth
• Muscle fibers are spindle shaped cells, with a single nucleus
• Cells are arranged in parallel lines, forming sheets
• Located in walls of hollow internal organs, it causes them to contract
• Contraction is involuntary
 Cardiac
• Forms the heart wall
• Its fibers are uninucleated, striated, tubular, and branched, which allows the fibers to interlock at intercalated disks
• Fibers relax completely between contractions, which prevents fatigue.
• Contraction is rhythmical, and involuntary
 Skeletal
• Fibers are tubular, multinucleated, and striated.
• Make up the skeletal muscles attached to the skeleton.
• Run the length of the muscles
• Muscle contractions are voluntary
o Functions of Skeletal Muscles
 Support the body
 Make bones move
 Help maintain constant body temperature
 Muscle contraction assists movement in cardiovascular and lymphatic vessels.
 Help protect internal organs and stabilize joints
o Skeletal Muscles of the Body
 Basic Structure of Skeletal Muscles
• A whole muscle contains bundles of fascicles (skeletal muscle fibers)
• Within a fascicle ach fiber is surrounded by connective tissue
• The fascicle itself is also surrounded by connective tissue
• Muscles are covered with fascia, a type of connective tissue that extends beyond the muscle and becomes its tendon
 Skeletal Muscles Work in Pairs
• The origin of a muscle is on a stationary bone
• The insertion of a muscle is on a bone that moves
• When a muscle contracts, it pulls on the tendons at its insertion, and the bone moves
• Skeletal muscles function in groups
• To make a particular movement the nervous system stimulates an appropriate group of muscles
o 1 muscle does most of the work (Prime Mover)
o Other muscles, called synergists, assist the prime mover.
o When muscles contract they shorten, they can only pull, they work in opposite pairs
• Skeletal Muscle Fiber Contraction
o Muscle Fibers and How They Slide
 Myofibrils and Sarcomeres
• Myofibrils
o Cylindrical in shape, and run the length of the muscle fiber
o The striations of skeletal muscle fibers are formed by the placement of myofilaments within units of myofibrils called sarcomeres
o A sarcomere extends between 2 dark lines called Z lines
o Sarcomere contains 2 types of protein myofilaments
 Thick filaments
• Made of myosin
 Thin filaments
• Made of actin
o The I band is light colored because it contains only actin filaments attached to a Z line. The dark regions of the A band contain overlapping actin and myosin filaments, its H zone has only myosin filaments
• Myofilaments
o Thick filaments
 Composed of several hundred molecules of myosin
 Each molecule is shaped like a golf club
o Thin Filaments
 Consists of 2 intertwining strands of actin
 2 other proteins called tropomyosin and troponin also plays a role
o Sliding Filaments
 When muscles are stimulated, impulses travel down a T tubule, and calcium is released from the sarcoplasmic Reticulum.
 The muscle fiber now contracts as the Sarcomere, within the myofibrils, shorten.
 When a sarcomere shortens, the actin filaments slide past the myosin filaments and approach one another.
 This causes the I band to shorten, the Z line to move inward, the H zone to almost or completely disappear.
 During the sliding process, the sarcomere shortens, even though the filaments themselves remain the same length.
o Control of Muscle Fiber Contraction
 Neuromuscular junction
• Muscle fibers are stimulated to contract by motor neurons whose axons are in nerves.
• The axon of one motor neuron can stimulate from a few to several muscle fibers of a muscle because each axon has several branches.
• Each branch of an axon ends in an axon terminal that lies in close proximity to the sarcolemma of a muscle fiber.
• The synaptic cleft separates the axon terminal from the sarcolemma.
 Axon terminal contain synaptic vesicles that are filled with the neurotransmitter Acetylcholine(Ach).
 When nerve impulses arrive at an axon terminal, the synaptic vesicles release Ach into the synaptic cleft.
 Botox prevents wrinkling of the brow and skin about the eyes because it blocks the release of Ach into the synaptic cleft, therefore muscle contraction never occurs.
 When ACh is released it diffuses across the cleft and binds to receptors in the sarcolemma.
 The sarcolemma generates impulses that spread over the sarcolemma and down T tubules to the sarcoplasmic Reticulum.
 The release of Ca2+ from the sarcoplasmic Reticulum leads to sarcomere contraction.
 When Ca2+ ions are released from the sarcoplasmic Reticulum, they combine with troponin, this causes tropomyosin threads to shift their position, exposing myosin-binding sites.
 Myosin can now bind to actin.
• Whole Muscle Contraction
o Muscles Have Motor Units
 A nerve fiber, together with all of the muscle fibers it innervates, is called a motor unit.
 A motor unit obeys the all-or-none law.
• All the muscle fibers in a motor unit are stimulated at once, they can either contract or they do not contract.
 When a motor unit is stimulated by infrequent electrical impulses, a single contraction occurs that lasts only a fraction of a second.
• This response is called a muscle twitch.
o 3 Stages:
 The Latent Period
• The period of time between stimulation and initiation of contraction
 The Contraction Period
• The muscle shortens
 The Relaxation Period
• The muscle returns to its former length
 A whole muscle contains many motor units
 As the intensity of nervous stimulation increases, more and more motor units in a muscle are activated.
o Muscle Tone
 Is dependent on muscle contraction
 Occurs when some motor units are always contracted but not enough to cause movement, the muscle is firm and solid
o Energy for Muscle Contraction
 Fuel Sources for Exercise
• Four possible energy sources.
o Two are stored in the muscle
 Glycogen and fat (triglycerides) are stored in muscles.
 The intensity and duration of exercise determines which one is used.
o Two are acquired from blood
 Blood glucose and plasma fatty acids are used as an energy source.
 Both are delivered by circulating blood.
 Sources of ATP for Muscle Contraction
• Muscle cells store limited amounts of ATP.
• There are 3 ways to acquire more ATP once the stored ATP has been used up:
o The CP (creatine phosphate) Pathway
 The simplest and fastest way for muscles to produce ATP, because it consists of only one reaction.
 The reaction occurs in the midst of sliding filaments.
 CP is formed only when a muscle cell is resting, and only a limited amount is stored.
 It is used at the beginning of submaximal exercise and during short-term, high intensity exercise that lasts less than 5 seconds.
o Fermentation
 Intense activities lasting longer than 5 seconds use fermentation.
 Fermentation produces 2 ATP from the breakdown of glucose to lactate anaerobically.
 Is fast-acting but results in the build up of lactate, which produces short-term muscle aches and fatigue.
o Cellular Respiration
 Is more likely to supply ATP when exercise is submaximal in intensity.
 Makes use of glucose from the breakdown of glycogen stored in muscle, glucose taken up from the blood, and fatty acids.
o Fast-Twitch and Slow-Twitch Muscle Fibers
 Fast-Twitch Fibers
• Usually anaerobic and are designed for strength because their motor fibers contain many fibers.
• They provide explosions of energy and are most helpful in sports activities.
• Light in color because they have fewer mitochondria, little or no myoglobin, and fewer blood vessels.
• Develops maximum tension more rapidly than slow-twitch fibers, maximum tension is greater.
• They fatigue quickly.
 Slow-Twitch Fibers
• Have a steadier tug and have more endurance
• They produce most of their energy aerobically; they tire only when their fuel supply is gone.
• They have many mitochondria and are dark in color because they contain myoglobin.
• They are surrounded by dense capillary beds and draw more blood and oxygen than fast-twitch fibers.
• Have a low maximum tension, which develops slowly.
• Highly resistant to fatigue.
o Delayed Onset Muscle Soreness
 Generally appears 24-48 hours after strenuous exercise.
 Is due to tissue damage that takes several days to heal
• Muscular Disorders
o Common Muscular Conditions
 Spasms
• Sudden involuntary muscular contractions often accompanied by pain.
 Cramps
• Strong, painful spasms, usually due to strenuous activity.
 Strain
• Stretching or tearing a muscle
 Sprain
• Twisting of a joint leading to injury and swelling
 Tendinitis
• The normal, smooth gliding motion of a tendon is impaired, the tendon is inflamed, movement of a joint becomes painful.
 Bursitis
• Inflammation of the bursa
o Muscular Diseases
 Myalgia
• Achy muscles
 Fibromyalgia
• Chronic condition
• Symptoms include
o Achy pain, tenderness, stiffness of muscles
 Muscular Dystrophy
• Broad term applied to a group of disorders that are characterized by a progressive degeneration and weakening of muscles
 Myasthenia Gravis
• An autoimmune disease characterized by weakness that especially affects the muscles of the eyelids, face, neck, and extremities.
 Amyotrophic Lateral Sclerosis
• Known as Lou Gehrig’s Disease
• Experience gradual loss of the ability to walk, talk, chew, and swallow.
• Homeostasis
o Both Systems Produce Movement
 The skeletal and muscular system work together to enable body movement.
o Both Systems Protect Body Parts
 The skeletal system protects the internal organs
 The muscular system pads bones
o Bones Store and Release Calcium
 The skeletal system performs tasks that are vital for calcium homeostasis.
o Blood Cells are Produced in Bones
 Red bone marrow is the site of blood cell production.
o Muscles Help Maintain Body Temperature
 When cold, smooth muscles in the blood vessels constrict, reducing amount of blood that is close to the surface of the body.

Monday, April 14, 2008

Unit 3: Self and Unit Evalution

Unit 3 Topic 2 Online Lab

Saturday, April 12, 2008

Friday, April 11, 2008

Celina

Celina

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