CH 15
The Brain and Cranial Nerves
Ventricles
I. lateral ventricles
A. within the cerebral hemispheres
B. septum pellucidum
1. a thin partition that separates lateral vents.
C. interventricular foramen
1. canal from lateral vents. to the 3rd ventricle
I.
third ventricle
A. cavity located in area called the diencephalon
B. mesencephalic aqueduct (cerebral aqueduct)
1. canal connects the third to the fourth ventricle
II. fourth ventricle
A. located posterior to pons and medulla oblongata
B. continuous with the central canal of the spinal cord
Cranial Meninges
I. Dura Mater
A. endosteal layer
1. fused to the periosteum of the skull
B. meningeal layer
1. innermost layer
2. falx cerebri
i.
fold that projects between the 2 hemispheres
ii. contains 2 venous sinuses – sup and inf.
sagittal sinuses
3. tentorium cerebelli
i.
separates the cerebrum from the cerebellum
ii. contains the transverse sinus
4. falx cerebelli
i.
divides the 2 cerebellar hemispheres
5. diaphragma sellae
i.
lines the sella turcica
ii. anchors the dura to the sphenoid bone
C. dural sinuses
1. slender gap btw the above layers
II.
Arachnoid Mater
A. subarachnoid space
1. delicate, weblike meshwork of collagen and elastic
fibers that link the arach. to the pia
2. supports BVs
3. space for CSF to flow around brain
B. arachnoid villi (granulations)
1. projections of arachnoid through the dura into the
superior sagittal sinus
2. allow CSF to enter venous circulation and be
taken away from the brain
III. Pia Mater
A. attached to the surface of the brain by astrocytes
B. supports BVs that branch over the surface of brain
Cerebrospinal Fluid
- 150 ml., replaced every eight hours
- produced by choroid plexes located in ventricles
I.
Fx:
A. cushioning delicate structures
B. supporting the brain
1. reduces weight from 1400 g in air to 50 g
C. transporting nutrients, chemical messengers, and
waste products
The Six Major Divisions of the Brain
Telencephalon, diencephalon, mesencephalon, myelencephalon,
and two areas known as the metencephalon.
I.
The Cerebrum (telencephalon)
A. Fx
1. conscious thought processes
2. intellectual functions
3. memory storage and retrieval
4. origination of complex motor patterns
B. Structures
1. cerebral hemispheres (half spheres)
A. gyri – elevated ridges, wormlike
B. sulci – shallow depressions
C. fissures – deeper grooves
2. longitudinal fissure
3. Lobes
A. frontal lobe – voluntary control of skeletal muscles
B. parietal lobe – conscious perception of touch,
pressure, vibration, pain, temp., and taste
C. temporal lobe – auditory and olfactory
D. occipital lobe – visual
E. insula – hidden deep to lateral sulcus
4. central sulcus – a deep grove that extends laterally
from the longitudinal fissure
5. precentral gyrus – gyrus anterior to central sulcus,
primary motor
6. postcentral gyrus – gyrus posterior to central sulcus,
primary sensory
7. lateral sulcus – deep groove that separates temporal
lobe from frontal lobe
8. parieto-occipital sulcus – separates occipital lobe
from parietal lobe
9. corpus callosum – connects hemispheres
10. Central white matter - myelanated bundles of
nerve fibers.
a. association fibers – interconnect portions of
cortex within same hemisphere
b. commisural fibers – permit communication
btw the two hemispheres
c. projection fibers – link cerebral cortex to the
diencephalon, brain stem, cerebellum, and
spinal cord.
11.
Cerebral nuclei – paired masses of gray matter
within the cerebral hemispheres
a. caudate nucleus – provide a general pattern
and rhythm of a movement once initiated
b. claustrum – processes visual information at
the subconscious level
c. globus pallidus – controls and adjusts muscle
tone in preparation for movement.
II.
Diencephalon
-connects the cerebral hemispheres to the brain stem
A. Thalamus
1. Fx:
a. provide the switching and relay centers for both
sensory and motor pathways
b. sensory information from spinal cord and cranial
nerves is processed in thalamus before the info is
relayed to the cerebrum or brain stem
c. anterior nuclei play a role in emotions, memory,
and learning
B. Hypothalamus
1. Fx:
a. controls involuntary somatic motor activities
associated with emotions or rage, pleasure, pain,
and sexual arousal
b. control of autonomic functions such as heart rate,
blood pressure, respiration and digestion
c. coordination of activities of the nervous and
endocrine systems
d. secretion of hormones
e. feeding, satiety and thirst centers
f. regulation of body temp
g. coordinate transition btw voluntary and
autonomic functions
h. controls circadian rhythms
III. Midbrain(mesencephalon)
A. Fx:
1. contains nuclei called corpora quadrigemina which
processes visual and auditory information and
generates reflexive responses
IV. Pons(metencephalon)
A. Fx:
1. contains apneustic and pneumotaxic areas which are
concerned with smoothing out breathing rhythms
2. acts as a bridge or relay center for other parts of the
brain
V.
Cerebellum(metencephalon)
A. Fx.
1. adjusts postural muscles to maintain balance and
equilibrium
2. fine-tuning voluntary and involuntary movements
VI. Medulla Oblongata(myelencephalon)
A. Fx:
1. contains cardiovascular center and respiratory
rhythmicity center
Cranial Nerves (XII pair)
Nerve
Associated function
I.
olfactory
smell
II.
optic
vision
III. oculomotor
innervates 4 eye muscles + pupil
constriction, opens eye lid
IV. trochlear
contract superior oblique eye muscle
V.
sensory from face and teeth
trigeminal
VI. abducens
lateral eye movement (lateral rectus)
VII. facial
facial expression, salivation, tears
and taste
VIII vestibulocochlear
sensory: balance and hearing
IX
glossopharyngeal
monitors blood gasses in carotid
artery, swallowing, salivation(P)
X
vagus
innervates visceral smooth muscle,
heart, lungs, most abdominal organs
XI
accessory
innervates sternocleidomastoid
and trapezeus muscles
XII hypoglossal
tongue movements
*Oh, Oh, Oh, To Touch And Feel Very Good Velvet A-H