V. BRAIN & CRANIAL NERVES
The brain weighs about 2% of your body weight and yet uses about 18% of your body’s energy and consists of billions of neurons.
A. Meninges
Same three layers as spinal cord.
B. Cerebrospinal Fluid (CSF)
1. Function
Cushion, transport
2. Location
Brain ventricles, Subarachnoid space, central canal of spinal cord
3. Formation of
a. Choroid plexus
Capillary network
b. Circulation
4. Lateral ventricles
Cerebrum
-Interventricular foramen
5. Third ventricle
Diencephalon
-Cerebral aqueduct=Mesencephalic Aqueduct
6. Fourth ventricle
Ventral to cerebellum
C. Brain Stem(Cranial nerves 3-12)
1. Medulla oblongata
a. Location
Most inferior, continuous with spinal cord
b. Function
1. All ascending/descending tracts between brain & spinal cord (Pyramidal motor tracts)
2. Vital reflexes
-Cardiac center
-Breathing center
-Vasomotor center
-Misc. (sneeze, hiccup, cough, vomit)
3. Reticular formation (R.A.S..)
Located in medulla, pons, mesencephalon and diencephalon
Activation of RAS leads to arousal, inactivation leads to sleep
2. Pons(“bridge””)
a. Location
Just superior to medulla oblongata
b. Function
1. Bridges cerebrum, cerebellum, Spinal cord
2. Aids in respiratory control
3. Mesencephalon (midbrain)
a. Location
Between pons & diencephalon
b. Cerebral peduncles (connect Upper/Lower Brain and spinal cord)
c. Corpora quadrigemina
1. Superior colliculi (visual reflexes)
2. Inferior colliculi (auditory reflexes)
D. Diencephalon(cranial nerve 2)
1. Thalamus
a. Location, 3rd ventricleTwo oval masses with bridge (intermediate mass) connecting the two
b. Function – sensory relay
With the exception of olfaction, all sensory tracts pass through the thalamus on the way to the cerebrum.
2. Hypothalamus
a. Location
b. Function
1. Regulates ANS
2. Regulates release & produces some hormones
3. Receives sensory information on internal environment
4. Temperature regulation
5. Regulates water balance, appetite, sexual activity
6. Mind over body, emotions, rage, panic, fear, R.A.S..
E. Cerebrum(cranial nerve 1)
1. Location
Bulk of brain anterior and dorsal
2. Fissure = deep grooves, gyri (convolutions) = folds, sulci = grooves
3. Lobes
a. Temporal
b. Frontal
c. Occipital
d. Parietal
4. Hemispheres
-Longitudinal fissure
5. Lateral ventricles
6. White matter
a. Projection fibers
Carries descending motor information from cerebral cortex, carries ascending sensory information from lower brain to cerebral cortex.
b. Association fibers
Connects ipsilateral areas of the cerebral cortex.
c. Commissural fibers
Contralateral cerebral cortex fibers.
-Corpus Callosum
7. Gray Matter
–Cerebral cortex
a. Motor area (frontal)
–Pyramidal tract
= Corticospinal tract. Monosynaptic pathway consisting of Upper motor neurons and Lower motor neurons for finely skilled movement.
–Extrapyramidal tract
Descending Polysynaptic tracts from subcortical areas
b. Premotor area (frontal)
Learned motor responses
c. Motor speech area (frontal)
“Broca’s” area
d. General sensory area (parietal)
[temp. pain, pressure, itch]
e. Taste area (parietal)
f. Visual area (occipital)
g. Olfactory area (temporal)
h. Auditory area (temporal)
[words into coherent thoughts]
i. Association area (all lobes)
[IQ, foresight, judgement, process sensory info. to formulate appropriate motor response]
8. Basal Nuclei
Controls skeletal muscles, inhibits some muscles to allow precise control of movements.
9. Limbic System
[Emotional aspects of behavior related to survival] Cerebrum and Diencephalon
a. Hippocampus – Temporal lobe of cerebrum; organizes experiences so that they can be stored as long term memory in other locations
b. Amygdala – Temporal lobe of cerebrum; mediates emotional responses based on senses – especially smell.
10. Cerebral Hemisphere lateralization
a. Left Hemisphere
-Right hand
-Math, science, analytical, sequencing
-Speech, language
b. Right Hemisphere
-Left hand
-Artistic, imagination, mental imaging, visual patterns
-Emotion
F. Cerebellum
1. Location, 4th ventricle
2. Transverse fissure
3. Function
H. Sensory pathways
I. Motor pathways
1. Pyramidal = Corticospinal Pathways
-U.M.N. monosynaptic
-L.M.N.
2. Extrapyramidal pathways polysynaptic {posture, balance}
J. Integrative functions
1. Memory
a. Reverberating Circuit
b. Electrical changes
c. Anatomy/biochemical change, synapses
-Increased dendrites
-Increased post synaptic receptors
-Increased neurotransmitter
-DNA, RNA
-Facilitate neuronal circuits