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THE NERVOUS SYSTEM
4. Right vs. Left Hemisphere
- Hemispheres are separate brains which “talk” to each other through
commissural fibers
a. Corpus callosum
b. Anterior and posterior commissures
 Left brain (hemisphere)
- 90%
- language
- speaking
- writing
- personality: logical, realistic, analytical
THE NERVOUS SYSTEM
 Right brain (hemisphere)
- 10%
- tactile
- visual
- auditory
- personality: intuitive, nonverbal, creative
 Split brain
- congenital
- surgery—cure major motor seizures
If left hemisphere damaged in children, language center often can be
transferred to right hemisphere
THE NERVOUS SYSTEM
H. Cranial Nerves
- How the brain communicates with the body without using the spinal cord
1. 12 pairs
2. Differ from spinal nerves
- no plexuses
- no dorsal or ventral roots
3. Transmit afferent impulses
- from special senses (equilibrium, vision, hearing, taste, and smell) and
proprioceptors
4. Transmit efferent impulses
- to eyes, face, jaw, tongue, pharynx, larynx, and parasympathetic to
viscera
Plexus
Roots
THE NERVOUS SYSTEM
5. Order: Know order.
Know functions for I, II, V, VIII, X
On
I
Occasion
Our
olfactory
II
III
optic
oculomotor
Trusty
IV
trochlear
Truck
V
trigeminal
Acts
VI
Funny
Very
abducens
VII facial
VIII vestibulocochlear
Good
IX
glossopharyngeal
Vehicle
X
vagus
Any
XI
accessory
How
XII hypoglossal
THE NERVOUS SYSTEM
6. Olfactory nerve (I)
- smell
- terminates in olfactory bulb at base of frontal lobe
7. Optic nerve (II)
- vision
- afferent fibers terminate in primary visual area of occipital lobe
8. Trigeminal nerve (V)
- afferent impulses from scalp, mouth, cornea
- efferent impulses to muscles of mouth (chewing) &
soft palate (swallowing)
THE NERVOUS SYSTEM
9. Vestibulocochlear nerve (VIII)
- two separate nerves from inner ear
a. vestibular = semicircular canals
- Function: equilibrium
b. cochlear = cochlea
- Function: hearing
10. Vagus nerve (X)
- afferent = taste, abdominal & thoracic organs
- efferent = soft palate, pharynx, larynx, heart, and smooth muscles,
and glands
THE NERVOUS SYSTEM
SENSORY AND MOTOR SYSTEMS
 Transfer of information between the brain and the body
 Occurs through the spinal cord
A. Sensory pathways
- Resulting in sensory perceptions
- All ascending
- Require 3 neurons
a. receptor
medulla or spinal cord
b. medulla or spinal cord
c. thalamus
thalamus
cerebral cortex
(1st order neuron)
(2nd order neuron)
(3rd order neuron)
THE NERVOUS SYSTEM
1. Spinothalamic tracts
- two types
a. Anterior
- tickle, itch, localized touch, pressure
b. Lateral
- pain and temp
1) Adjacent sensory impulses
- Can block pain transmission
2) Enkephalins & endorphins
- brain’s own pain killers
THE NERVOUS SYSTEM
B. Motor pathways
- Resulting in response at effector organ
- All descending
- Require 2 neurons
a. cerebral cortex
b. spinal cord
spinal cord
muscle
(upper motor neuron)
(lower motor neuron)
1. Corticospinal tracts (pyramidal)
- Impulses result in voluntary skeletal muscle movement
- 90% of fibers cross over at medulla
THE NERVOUS SYSTEM
AUTONOMIC NERVOUS SYSTEM (ANS)
- Consists of motor neurons to smooth muscle, cardiac muscle, and glands.
- Depending on the type of receptor, the neurotransmitter released may either
excite or inhibit the effector.
Two neurons
1. Preganglionic
- cell body located in brain and spinal cord
2. Postganglionic
- completely outside of CNS
THE NERVOUS SYSTEM
Comparison Chart
Sympathetic
Parasympathetic
adrenergic*
thoracolumbar
cholinergic*
craniosacral
fight or flight
rest & digest
prepare for emergency
(stress)
recovery
4. Heart Rate
increase
decrease
5. Lung Bronchi
dilation
constriction
1. CNS Division
(outlet)
2. General Response
3. Function
6. Adrenal Medulla
(Adrenalin)
7. Efferent
secretion
------------------
preganglionic
preganglionic
postganglionic
postganglionic
THE NERVOUS SYSTEM
Adrenergic fibers
- Release norepinephrine
- All sympathetic postganglionic neurons (axons)
- Long-lived impulse
Cholinergic fibers
- Release acetylcholine
- All parasympathetic postganglionic neurons (axons)
- All (sympathetic and parasympathetic) preganglionic neurons (axons)
- Short-lived impulse