ch7 notes1
TRANSCRIPT
Name________________________________Block_____Date______________________ Ch 7 The Nervous System Notes Lisa Peck
I. Organization of the Nervous System (pp 222-224)
Nervous system- the master controlling and communicating system of the body3 functions: 1. sensory receptors to monitor changes occurring inside & outside body
stimuli- changessensory input- gathered information
2. processes and interprets the sensory input integration- nervous system makes decisions about what should be done
3. effects a response by activating muscles or glands (effectors) via motor output
Regulating and Maintaining Homeostasisnervous system - fast-acting control via electrical impulsesendocrine system- slow-acting control via hormones release into the blood
Structural Classification (p 223)
2 subdivisions: Central Nervous System Peripheral Nervous System
1. Central Nervous System (CNS) consists of: brain
spinal cord
functions: integrating center.........interpret incoming sensory information command center..........issue instructions based on past experience & current conditions
2. Peripheral Nervous System (PNS) consists of: nerves 2 types: cranial nerves- carry impulses to and from the brain
spinal nerves- carry impulses to and from the spinal cord
ganglia- groups of nerve cell bodies
function: communication lines, linking all parts of the body
Functional Classification (pp 223-224) 2only deals with peripheral nervous system (PNS)
1. Sensory (Afferent) Division- nerve fibers that carry impulses to the CNS from sensoryreceptors located throughout body
sensory fibers types: 1. somatic sensory fibers- delivering impulses from the skin, skeletal muscles, & joints
2. visceral sensory fibers- transmitting impulses from the visceral organs
2. Motor (Efferent) Division- nerve fibers that carry impulses from the CNS to effector organs ossicles and glands, bringing about a motor response
2 types: 1. somatic nervous system: conscious control of skeletal muscles voluntary control
skeletal muscles
2. autonomic nervous system (ANS)- regulates activities that are automatic involuntary
cardiac muscle smooth muscle glands
2 nerve types that target same organ but yield opp. effects exception: targeted only by sympathetic: some glands,
most blood vessels, most structures of the skin
2 types: 1. sympathetic-” fight or flight”f’ns during extreme situationsex: increase heart rate rapid breathing cold, sweaty skin dilated pupils
2. parasympathetic- “resting & digesting” most active when body at rest
causing normal digestion, voiding feces & urine goal: conserving energy
Nervous Tissue: Structure and function (pp 224-235) 3
2 types of cells: 1. neuroglia- supporting cells not able to conduct impulses can undergo cell division most brain tumors are gliomas- formed by glial cells
2. neurons nerve cells that transmit impulses functional unit of nervous system
neurglia (pp 224-226) not able to conduct impulseglia (glial cells)- f’n: support, insulation, & protection ~90% cells in brain are glial cells
CNS: 4 types: astrocytes PNS: 2 types microglia schwann cells ependymal satellite cells oligodendrocytes
1. Astrocytes- star-shaped cells
account for over half of neural tissue numerous projections have swollen ends that cling to neurons f’n: 1. brace and anchor neurons to capillaries
intermediary cell b/w neuron and capillary (aids in exchange) protects neurons from harmful substances present in blood2. control chemical environment in brain by picking up excess ions & recapturing released neurotransmitters
neurglia 4
2. Microglia- spiderlike phagocytes dispose of debris (dead brain cells & bacteria)
smallest of glial cells
3. Ependymal- line cavities of the brain & spinal cord f’n- beating of cilia helps circulate cerebrospinal fluid that fills cavities & forms protective cushion around CNS
4. Oligodendrocytes- (CNS) wrap their flat extensions around axons of many nerves forms myelin sheath- fatty insulating covering
protects and cushions nervesspeeds up nerve transmission speed
gives rise to white matter of brain
fewer extensions than astrocytes
PNS: 2 types:
1. Schwann cells- cells of PNS that myelinate axons2. satellite cells- protective & cushioning cells of PNS neurons
B. Neurons (pp 226-235) 51. Anatomy (of a generalized neuron)
cell body- metabolic center contains typical cell organelles
(exception: no centrioles .....no mitosis -amitotic)
axon- one per cell, process of neuronconduct impulses away from the cell body
dendrites- many per cell, extension of neuron (often branched extensively) conduct impulses toward cell body
axon hillock- axon arises form this conelike region of cell body
axon terminals- 100’s to 1000’s branches at terminal end of axon contain vessicles of neurotransmitters
collateral branch- branch off of an axon
Nerve Anatomy 6synaptic cleft (synapse)- separation b/w axon terminal and next neuron
myelin- covering of most long neurons (axon) whitish, fatty substance protects, insulates, speeds up neural transmission
CNS:oligodendrocytes- form myelin sheath
lacks neurolemma f’n- protects and cushions nerve increases speed of nerve transmission located in CNS
PNS:schwann cell’s form myelin sheath
covering of most long neurons formed by wrapping of a Schwann cell
schwann cell- specialized supportive cells wrap tightly around axon
neurolemma- outermost part of schwann cell aids in neuron regeneration
nodes of Ranvier- gaps of myelin sheathb/ w Schwann cellsloc. @ regular intervalsaction potential jumps fromnode to node- faster
CNS white matter- dense bundles of myelinated fibers (tracts) brain- inside spinal cord- surfacegray matter- unmyelinated fibers and cell bodies brain- surface spinal cord- inside
CNS PNSnuclei ganglia groups of cell bodies
tracts nerves bundles of nerve fibers
Classification of Neurons 7functional classification- according to direction of impulse is traveling relative to CNS 1. sensory neuron- nerve impulse travels towards CNS
afferent cell bodies outside CNS in ganglion
receptors- dendrite endings that are specialized activated by specific changes nearby (stimuli)
taste, hearing, sight, equilibrium, smellcutaneous sense organs- pacinian & meissner corpusclesproprioceptors- loc. in muscles & tendons
detects amt. of stretch or tension determines location, posture, and tone
muscle spindle golgi tendon organs
pain receptors- bare dendrite endings least specialized cutaneous receptor most numerous cutaneous receptor
2. motor neuron- nerve impulse travels away from CNS efferent neuron
cell bodies inside CNS in nuclei
3. association neurons (interneurons)- connect motor and sensory neurons cell bodies in CNS
Classification of Neurons 8structural classification- based on number of processes extending from cell body
multipolar- several processes all motor neurons all association neurons most common neuron type
bipolar- 2 process on cell body axon & dendrite rare in adults (eg; eye & nose)
unipolar- one process on cell body single process is very short process divides into 2 peripheral process- (distal)
contains dendrites on end central process- (proximal)
contains axon terminals axon- both peripheral & central
processes conducts impulses in both
directions (toward & away from cell body)
sensory neurons located in PNS ganglia are all unipolar
3. Physiology nerve impulse generation (action potential)reflex arcs- neural pathways involve both CNS & PNSreflexes- rapid, predictable and involuntary responses to stimuli
once reflex begins...always goes in same direction types: somatic reflexes- stimulate the skeletal muscles
eg: pull hand away from hot stove
autonomic reflexes- regulate the activity of smooth muscles, heart, & glands eg: secretion of saliva, changes in pupil size,
regulates: digestion, elimination, blood pressure, & sweating
III. Central Nervous system (pp 235-249) 9
Functional Anatomy of the Brain (pp 235-241) 10Brain- 3 parts1. forebrain- cerebrum
diencephalon- thalamus hypothalamus
2. midbrain- small superior part of brain stem
3. hindbrain- cerebellum brain stem (part of it)- medulla oblongata
pons
Forebrain2 parts: 1. cerebrum (cerebral hemispheres)
2. diencephalon
Cerebrum: largest part of brain divided into left and right hemispheres-cerebral hemispheresseparated by corpus callosum (internally)- large fiber tract connecting hemispheres
longitudinal fissure (surface)
the spinal tracts cross over -------> left hemisphere deals w/ right side of body right hemisphere deals w/ left side of body
surface is highly convoluted- increasing surface area (increases # of neurons)
cortex- (exterior) gray matter thin surface layer (1-4 mm thick)
Interior- white matter, nerve tract relaying impulses to & from cerebral cortex
gyrus (gyri)- elevated ridges on cerebral cortexsulcus (sulci)- shallow grooves in cortex fissure- deep sulcus in cortex sulci divide hemispheres into 4 lobes
separate large areas of brain frontal lobe
parietal lobe
occipital lobe
temporal lobe
Functional Anatomy of the Brain (pp 235-241) 11
ForebrainCerebrum- cerebral cortex: 4 lobes f’n- speech, memory, logical & emotional response, consciousness, interpretation of sensation,
voluntary movement, problem solving frontal lobe primary motor area- located anterior to central sulcus
initiates voluntary movement of skeletal muscles (motor language too)
premotor area- located anterior to primary motor area process input regarding body movement, modify movements
prefrontal area- anterior frontal lobe higher level thought, decision making, planning, impulsivity control selective attention, personality, problem solving, behavior, emotions Broca’s area- inferior left frontal gyrus
controls facial neurons & speech production- articulation (works in junction with Wernicke’s Area- language comprehension)
parietal lobe somatic sensory area- located posterior to central sulcus
interprets input from sensory receptors (except specialized senses) aids in spacial orientation
sensory pathways are crossed pathways (left sensory area receives input from right side of body)
temporal lobe- auditory processing olfactory area (located deep temporal) memory: right lobe- visual memory (pictures, faces)
left lobe- verbal memory (words, names)
occipital lobe- visual center , processes visual info and visual recognition of shapes & colors
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Forebrain1. Cerebrum- “telencephalon”2. Diencephalon- located superior to brain stem & enclosed by cerebral hemispheres
3 parts- thalamus- relay station for sensory impulses passing upward to somatic sensory cortex all sensory input passes thru thalamus to cortex (except olfaction) signals from cerebellum pass thru thalamus up to motor area of cortex
encloses 3rd ventricle (spaces filled w/ cerebrospinal fluid...aids in circulation)
hypothalamus-”seat” of autonomic nervous system regulates homeostasis
both nervous & endocrine f’ns source of 8 hormones regulation of: body temp, water balance, blood chemistry, metabolism
heart rate, death results if damaged
plays imp. part in limbic system- “emotional-visceral brain” emotion, motivation
epithalamus- forms roof of 3rd ventricle choroid plexus- knots of capillaries w/ in ea. ventricle forms CSF pineal body- endocrine gland
releases melatonin- regulates daily body rhythms eg: day/ night cycle melatonin released @ night
Brain Stem- pathway for ascending & descending tracts, has gray areas- cranial nerveshelp control breathing, heart rate etc.
1. midbrain 2. pons 3. medulla oblongata reticular formation- extends length of brain stem (middle of hindbrain to midbrain)
role in consciousness & awake/ sleep cycles damaged- coma
Midbrain 13 located upper part of brain stem very small portion of brain stem evolutionarily: the oldest part of brain only used for eye reflexes reticular formation- collects input from higher brain centers & passes it on to motor neurons substantia nigra- helps “smooth” out body movements damaged-Parkinson’s Disease ventral tegmental area (VTA)- loaded w/ dopamine-releasing neurons that are activated
by nicotinic acetylcholine receptors & synapse deep w/ in forebrain VTA involved in pleasure: nicotine, amphetamines & cocaine bind to and activate its dopamine-releasing neurons- may account for their addictive qualities
Hindbrain-consists of part of brain stem: 1. pons 2. medulla oblongata
3. cerebellum
pons- rounded structure protruding below midbrain unconscious control of breathing (reflexive breathing)
reticular formation- area receives sensory input from forebrain & passes to thalamus involved in sleep, arousal & vomiting
relay center b/w cerebral cortex (impulses from eyes, ears, & touch receptors) & cerebellum
medulla oblongata- closest to spinal cord most inferior part of brain stem f’n- regulation of heart beat, breathing, vasoconstriction (blood pressure),
reflex centers for vomiting, coughing, sneezing, swallowing, & hiccups
important fiber tract area damaged- death 4th ventricle lies posterior to medulla oblongata
cerebellum- second largest part of brain 2 convoluted hemispheres surface layer is gray matter and internal area is white matter f’n- muscle coordination maintain normal muscle tone & posture balance & equilibrium
Limbic System- receives input from association areas in cortex & passes signals cerebrum 2 parts: hippocampus- essential for formation of long term memories
amygdala- center of emotions (eg fear) send signals to hypothalamus& medulla wh/ can activate “fight or flight” receives signals form olfactory system....may account for powerful effect that odor has on memory
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Protection of the Central Nervous System (pp 241-244)
1. Bones of skull and vertebral column2. Meninges
dura mater- outermostarachnoid matter- middlepia matter- innermost
Protection of the Central Nervous System (pp 241-244) 152. Meninges- 3 continuous sheets covering both spinal cord and brain
dura mater- outermost, pressed against bony surface on interior of vertebrae & craniumarachnoid mater- middle layer, weblike, threadlike extensions pass thru subarachnoid
space & attach to pia materpia mater- innermost layer, thin, attached to surface of spinal cord & brain
3. Cerebrospinal Fluid (CSF) fluid similar to blood plasma containing protein, vit. C, and ions bathes cells of CNS protecting them from physical trauma returns to blood thru veins drainging the brain choroid plexus- capillaries that secrete CSF
located hanging from roof of each ventricle ( 2 lateral, 3rd & 4th) CSF location
4. Blood-Brain Barrier
C. Brain Dysfunctions (pp 244-247) 16 1. Traumatic Brain Injuries
concussion- reversible damagecontusions- nonreversible damage
2. Cerebrovascular Accidents (CVA)- strokevisual impairmentparalysisaphasias
3. Alzheimer’s Disease 4. Huntington’s Disease 5. Parkinson’s Disease 6. Diagnosis (pp 262-263) electroencephalogram (EEG) simple reflex tests angiography CT scans PET scans MRI & Functional MRI scans
D. Spinal Cord (247-249) ~17 inches from foramen magnum to L1 or L2 cauda equina- cord ends w/ spinal nerves @ L2 31 pairs of spinal nerves (dorsal & ventral roots)
Gray Matter of Spinal Cords & Spinal Roots gray matter in middle around central canal (H shape) 2 dorsal (post.) horns- contains interneurons connected to sensory neurons from dorsal root 2 ventral (ant.) horns- cell bodies of motor neurons whose axons leave via ventral root
White Matter of the Spinal Cord 3 regions anterior column: ascending tracts only (incoming sensory) lateral column: both ascending & descending posterior column: both ascending & descending
spinal nerve- fused dorsal & ventral roots (a mixed nerve- sensory & motor neurons) dorsal root: entering sensory neurons dorsal root ganglia- sensory nerve cell bodies ventral root: motor nerve axons
Peripheral Nervous System (pp 249-263) 17 contain only nerves (no glial cells)Structure of a Nerve nerve- bundle of neuron fibers (held tog. w/ connective tissue) endoneurium- surrounds each never fiber perineurium- binds groups of fibers into fasicles epineurium- bind fascicles together
12 Pairs of Cranial Nerves numbered in order from front to back most are mixed nerves (3 sensory only)
I olfactory sensory 4 smell
II optic sensory 4 vision
III oculomotor motor fibers to eye muscles
IV trochlear motor fibers to eye muscles
V trigeminal sensory 4 face motor fibers to chewing muscles
VI abducens motor fibers to eye muscles
VII facial sensory 4 taste motor fibers to face
VIII vestibulocochlear sensory 4 hearing & balance
IX glossopharyngeal sensory 4 taste motor fibers to pharynx
X vagus sensory & motor 4 pharynx, larynx, & viscera
XI accessory motor nerve to neck & upper back
XII hypoglossal motor fibers to tongue
31 Pairs of Spinal Nerves and Nerve Plexuses 18
spinal nerves formed by combo of venrtral & dorsal roots of spinal cordspinal nerves named for region from which they arise
spinal nerves divide after leave spinal cord dorsal rami- serve skin & posterior trunk muscles ventral rami- form plexus for the anterior
plexuses- ventral rami of spinal nerves form complex networks that serve motor & sensory needs of limbs 4 plexus: cervical, brachial, lumbar, & sacral
classification of nerves by direction of impulse mixed nerve- travels to & from CNS inlcudes both sensory and motor nerve fibers sensory nerve- carry impulse towards CNS (afferent) motor nerve- carry impulse away from CNS (efferent)
Autonomic Nervous System 19
somatic & autonomic nervous systems compared Somatic NS Autonomic NS
Nerves one motor neuron preganglionic nerves postganglionic nerves
Effector Organs skeletal muscle smooth muscle cardiac muscle glands
Neurotransmitters always use acetylcholine acetylcholine epinephrine norepinephrine
Autonomic Nervous System: involuntary control 2 divisions that serve same effector (smooth or cardiac muscle or a gland)
2 divisions bring about opposite effects, coutner balance ea. other
major difference 1) location of origin in CNS parasympathetic- brain stem or S1-S4
sympathetic- T1-L2
2) location of ganglia parasympathetic- ganglia near spinal cord
sympathetic- ganglia near effector organ
Autonomic Nervous System 20 Parasympathetic division (PaNS)“housekeeping activities”conserves energymaintains daily necessary body functions“D” division: digestion, defecation, and diuresis
constricts pupilsconserve Estimulates digestive (increase saliva) stimulates urinary organs (increase urine production)inhibit cardiovascular system (slow heart rate)inhibit respiratory systems (constrict airways, slow respirations)
Sympathetic division (SyNS)“fight-or-flight” response to unusual stimulustakes over to increase activities“E” division: exercise, excitement, emergency, & embarrassment
pupils dialatestimulate respiratory organs (increase breathing rate & open airways)stimulate cardiovasculary system (increase heart rate)stimulate adrenal glands (release epinephrine and norepinephrine...stimulate liver)stimulated liver (convert glycogen into glucose....release into blood)inhibit digesitve system (decrease saliva...dry mouth)inhibit urinary system
increase glucose use....generates heat and water...increase sweat, reddened skin
polygraph- measures stress incurred when tell a lie. You know it is wrong to lie, when you do lie your sympathetic NS kicks in and your adrenal glands cause heart rate to increase.
measures changes in heart rate
Developmental Aspects of the Nervous System (pp 263-266) 21
nervous system if formed during the first month of embryonic development
any maternal infection can have extremely harmful effects
the hypothalamus is one of the last areas of the brain to develop it controls body temperature: premature babies and infants can not maintain body temp
there are no more neurons formed after birth, but growth and maturation continues for several yearsneurons will develop myelination during maturation- increases neuromuscular control
the brain reaches maximum weight as a young adult
A. Embryonic Brain Developmentcerebral palsyanencephalyhydrocephalusspina bifida
B. Premature Infantstemperature regulation via hypothalamus