Download Chapter 13 Central Nervous System

LECTURE OUTLINE CHAPTER 13 Marieb
The Nervous System: The Brain and Spinal Cord
Lecture Outline
BRAIN
I. Introduction to the Organization of the Brain
This pattern can be generalized further to say that the lowest (most
inferior) parts control the bare necessities for life - regulation of
heartbeat, digestion, etc. The next levels up are the location for
primal drives and emotions - rage, fear, sex drive, hunger, etc. The
most superior level, top of the brain, is intellectual thought,
imagination, perception, interpretation, and appreciation of
sensations, and control and modulation of emotions. An infant
apparently starts out using mostly the lowest, then the next, and
finally the upper parts of its brain. (The terrible twos, threes and
beyond evidence the emotional part over which parents attempt to help the child
establish third level control - a veneer of civilization)
II. Major Regions of the Brain
A. Cerebrum (telencephalon)
1. two hemispheres separated by longitudinal fissure
2. gyrus separated by sulcus
3. gray surface with white tracts internally
a. commissure – connect corresponding gyri of the two
hemispheres
1) corpus callosum
b. projection tracts – connect more or less vertically
c. association tracts – connect one gyrus to another in the
same hemisphere
4. lobes – named for covering bones
a. frontal
b. parietal
c. temporal
d. occipital
e. insula - hidden deep to temporal lobe
B. Diencephalon
1. epithalamus ( pineal gland)
2. thalamus
3. hypothalamus
C. Cerebellum (metencephalon)
1. two hemispheres, gray surface
2. folia – ridges on surface separated by sulci
3. arbor vita – white tracts
D. Brainstem ( (myelencephalon)
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1. medulla oblongata
a. pyramids - decussation or crossing over
2. pons
3. midbrain
III. Overall Organization
A. Portions closely attached to spinal cord are white on the outside with
gray material internally. Less conscious awareness of activity occurs there
B. Ventricles – cavities
1. make / contain cerebrospinal fluid (CSF)
a. choroid plexus with
b. ependymal cells line the ventricles
2. two lateral ventricles either side of thalamus, drains by
interventricular foramen into3. third ventricle which drains by cerebral aqueduct to 4. fourth ventricle
5. CSF circulates in sub arachnoid space and is reabsorbed
6. into superior sagittal sinus by arachnoid villi (granulations)
C.. Meninges (See previous chapter)
1. dura mater - strong, "tough mother"
a. falx cerebri - between cerebral hemispheres
b. falx cerebelli - between cerebellar hemispheres
c. tentorum cerebelli - between cerebrum and cerebellum
2. arachnoid - spidery, holds blood vessels
3. pia mater - "delicate mother"
D. Cerebrospinal fluid (CSF)
1. functions
a. “floats” the brain; shock- absorbing, cushioning
b. transports nutrients, wastes, other chemicals
2. formation
a. choroid plexus - network of capillaries and
b. ependymal cells - glia which selectively take blood
components to form CSF
3. Reabsorption through arachnoid granulations
E. Cerebral cortex --Lobes named according to overlying skull bones
1. gray, final processing region for input
2. many regions - exact regions are imprecise
a. visual area
b. visual association area
c. auditory area
d. auditory association area
e. precentral ( primary motor ) cortex
f. postcentral (primary sensory) cortex
g. premotor cortex
h. prefrontal cortex
F. White tracts internally
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1. commissure – connect corresponding gyri of the two
hemispheres
a. corpus callosum
2. projection tracts – connect more or less vertically, form internal
capsule
3. association tracts – connect one gyrus to another in the same
hemisphere
G. Cerebral nuclei - gray matter internal to the cerebral cortex, part of
the extrapyramidal system
1. caudate nucleus - deep to lateral ventricles, maintains the
pattern and rhythm of a movement
2. amygdaloid nucelus - almond shaped, near tail of caudate
nucleus, part of limbic system (emotional brain)
3. claustrum - between insula and diencephalon, focuses visual
attention
4. lentiform nucleus - bean shaped made up of a. putamen - with claustrum
b. globus pallidus - with claustrum and putamen, controls
and adjusts muscle tone
5. corpus striatum -encloses both lentiform and caudate nuclei
H. Functional brain systems
1. limbic system
a. functions– emotional brain, links conscious and
unconscious functions
b. components - limbic lobe made up of - cingualte gyrus,
dentate gyrus, parahippocampal gyrus, hippocampus, fornix,
mamillary bodies, and anterior nucleus
2. RAS –reticular activating system – determines levels of
alertness, composed of mesencephalon and network of nuclei
IV. Diencephalon
A. Epithalamus
1. pineal gland - produces melatonin, sets diurnal cycles
B. Thalamus
1. structure a. two lobes - third ventricle between these
b. massa intermedia - connecting strand
2. functions
a. anterior nuclei - part of limbic system, information relay
b. medial nuclei - conscious awareness of emotional state,
integrate sensory information, relay to frontal lobes
c. ventral nuclei - relay information to and from central nuclei
and cerebral cortex
i. ventral posterior - relays sensory information
ii. ventral lateral - relays somatic information to and
from primary motor cortex
d. posterior nuclei -
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i. pulvinar - integrates sensory information to
association areas
ii. lateral geniculate - relays visual information
iii. medial geniculate - relay auditory information to
association areas
e. lateral nuclei - feedback, integrates emotional with
sensory information
C. Hypothalamus
1. structure
a. just superior to optic chiasma
b. infundibulum - connects to pituitary gland
c. tuber cinereum - between infundibulum and mamillary
bodies, gray matter, controls pituitary
d. median eminence - part of tuber cinereum
2. functions
a. control of involuntary somatic motor activites,
expressions of emotional states
b. control of autonomic nervous system
c. coordination of nervous and endocrine systems
d. secretion of hormones - ADH (from supraoptic nuclei)
and oxytocin (from paraventricular nuclei)
e. produces emotional and basic drives - hunger, thirst, sex,
anger, etc.
f. coordinates voluntary and autonomic activity
g. regulates body temperature
h. controls diurnal rhythms
V. Mesencephalon - midbrain
A. Structure and functions
1. corpora quadrigemina
a. superior colliculus - processes visual information
b. inferior colliculus - relays auditory information to thalamus
2. tectum - roof of fourth ventricle
3. red nucleus - involuntary muscle activity for posture, etc
4. substantia nigra -regulates motor output
5.cerebral peduncles - ascending and descending tracts to
thalamus
VI. Pons
A. Sensory and motor nuclei for 4 cranial nerves (V, VI, VII, and VIII)
B. Nuclei for Involuntary control of respiration
1. apneustic center
2. pneumotaxic center - together regulate lung inflation and
breathing rhythms
C. Nuclei which relay cerebellar information through cerebral peduncles
D. Tracts - ascending, descending and transverse - permits
communication between cerebellar hemispheres
VII. Cerebellum
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A. Structure
1. hemispheres, separated by vermis
2. lobes - 2 each hemisphere, separated by primary fissure
a. anterior
b. posterior
c. small flocculomotor - anterior and inferior to major lobes
3. cortex -gray surface with
a. folia - fine ridges
b. sulcus - grooves between the ridges
c. Purkinje cells , axons of which become4. arbor vitae (white matter) in center
5. cerebellar nuclei - synapsing of sensory information for motion
6. superior cerebellar peduncles - link tocerebrum, diencephalon
and mesencephalon
7. middle cerebellar peduncles - connect to motor and sensory
centers of pons
8. inferior cerebellar peduncles - link to medulla, carry ascending
and descending tracts
B. Functions
1. postural muscles control ( by way of red nucleus)
2. fine control and coordination of voluntary and involuntary
movements
VIII. Medulla Oblongata continuous with spinal cord
A. Structure
1. gray matter
a. nucleus gracilis - relay sensory information to thalamus
b. nucleus cuneatus - as above
c. olivary nuclei - relay to cerebellum from all other regions
d. nuclei of cranial nerves numbers VIII, IX, X, XI, and XII
e. reflex centers - autonomic system
i. cardiovascular center - includes cardiac and
vasomotor centers - regulate rate, pressure, etc.
ii. respiratory rhythmicity center - self explanatory
2. white matter
a. ascending tracts - sensory information
b. descending tracts - motor information
SPINAL CORD
I. Spinal cord
A. longitudinal organization
1. bilateral symmetry
2. cervical and lumbar enlargements - associated with more cell
bodies for motor control of limbs
3. anterior fissures
4. posterior sulcus
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5. central canal, containing CSF
6. superficial white (myelinated) tracts/columns
a. anterior and lateral descending
b. posterior and lateral ascending
7. interior gray horns
a. cell bodies, dendrites and synapses
8. 31 pairs of spinal nerves – named after the inferior vertebra
a. 8 cervical
b. 12 thoracic
c. 5 lumbar
d. 5 sacral
9. conus medullaris - inferior end of spinal cord proper
10. cauda equina - individual spinal nerves within spinal canal
11. filum terminale - filamentous end of meninges, "tie-down"
B. Coverings - meninges
1. dura mater - "tough mother", strong
2. sub dural space
3. arachnoid meninx - spidery looking, carries blood vessels, etc.
4. subarachnoid space
5. pia mater - "delicate mother", adheres tightly to surface of spinal
cord
C. Organization of cross section of cord
1. Gray matter - interior horns
a. posterior - somatic and visceral sensory nuclei
b. anterior gray horns - somatic motor control
c. lateral gray horns - visceral motor control
d. gray commissures - axons carrying information from side
to side
2. White matter - tracts or columns
a. positions
i. posterior white column ii. anterior white column
iii. lateral white column
iv. anterior white commissure
b. functions
i. ascending tracts - sensory toward brain
ii. descending tracts - motor from brain
E. Nerves - definition – bundles of axons , AKA tracts in CNS
F. Organization
1. coverings – similar to muscles
a epineurium - wraps entire nerve
b. perineurium - wraps fascicles of tracts
c. endoneurium - wraps individual axons
2. function
a. sensory - afferent
b. motor - efferent
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c. mixed - contains axons of both
G. Dermatomes
Sensory innervation by specific spinal nerves
H. . Organization of each spinal nerve
1. root – inside vertebral canal
a. dorsal sensory root with a ganglion
b. ventral motor
2. mixed spinal nerve
3. rami
a. dorsal mixed
b. ventral mixed “spinal nerve”
c. white ramus communicans motor ANS
d. gray ramus communicans motor ANS
I. Plexus – braid of ventral rami of cervical, thoracic, lumbar or sacral
spinal nerves
1. cervical
a. phrenic nerve - innervates diaphragm
2. brachial
a. trunks - superior, middle, and inferior
b. cords - lateral, medial, and posterior
i. musculocutaneous nerve - innervates biceps and
brachialis muscles
ii. median nerve - innervates lateral flexors
iii. ulnar nerve - innervates medial flexors
iv. axillary nerve - innervates deltoid muscle
v. radial nerve - innervates forearm extensors
3. lumbar
a. genitofemoral nerve
b. lateral femoral cutaneous nerve
c. femoral nerve
4. sacral
a. lumbosacral trunk
i. sciatic nerve
ii. pudendal nerve
iii. common peroneal nerve
iv. tibial nerve
J. Reflexes – fast, stereotypical, inborn, protective actions
1. occur at spinal cord or brainstem levels
2. do NOT require cerebral processing but can be modified by
cerebral control
3. may be either monosynaptic or polysynaptic but either is
relatively simple
4. may be either somatic or visceral
5. all require a. stimulus at receptor
b. sensory information relay
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c. processing at CNS level
d. activation of motor response
e. response of peripheral effector
6. examples
a. patellar
b. stretch reflex
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