Introduction to the Nervous System

Question 1

What Do Nerves Do?

Answer 1

Sensory Functions: Enable us to perceive internal and external environments.

Special Senses: Vision, hearing, taste, smell, and balance

Motor Functions: Facilitate appropriate responses to stimuli.

• Voluntary: Skeletal muscle movement (locomotion)
• Involuntary: Smooth muscle, gland, and cardiac muscle actions
  Reflex Functions: Automatic, rapid responses to stimuli.

Question 2

Anatomical Subdivisions

Answer 2

Central Nervous System
Peripheral Nervous System

Question 3

Describe the CNS

Answer 3

Brain
Spinal Cord
Central controller

Question 4

Describe the PNS

Answer 4

All other nerve tissue not within the CNS
Spinal nerves
-connect with spinal cord
Cranial nerves
-connect with brain
Autonomic nerves
-organs, smooth muscle, glands
-visceral afferents
-sympathetic nerves
-parasympathetic nerves
Wiring

Question 5

Describe The Neuron

Answer 5

Basic unit of nervous system
Collection of nerve cell bodies:
in CNS = Nucleus
in PNS = Ganglion

Question 6

Describe Nerves

Answer 6

Bundles of Axons (nerve fibres): Wrapped in connective tissue, traveling to/from same regions or structures.
Can branch off as smaller bundles
Named Nerves: Larger nerves serving the body wall, cavities, and organs

Question 7

What is in a Nerve?

Answer 7

A single nerve fiber (axon) only conducts action potentials for ONE of six modalities:
1. Somatic sensory function
2. Somatic motor function
3. Special sensory function
4. Visceral afferent function
5. Sympathetic function
6. Parasympathetic function

Question 8

Motor Vs Sensory

Answer 8

Motor (efferent):
Action potential towards body wall, body cavity or organ
Sensory (afferent):
Action potential towards brain

Question 9

Describe The Brain

Answer 9

outermost layer of the cerebral hemispheres cortex
consists of gyri and sulci

4 lobes of each cerebral hemisphere
named according to cranial bone they lie deep to

Question 10

What is the Cranial Nerves

Answer 10

12 pairs - need to know name, number (Roman numerals), modality and function(s), where they connect to CNS, route through and exit from cranium

Question 11

CN I

Answer 11

-olfactory nerve
-sensory (special)

Question 12

CN II

Answer 12

optic nerve
sensory (special)

Question 13

CN III

Answer 13

oculomotor nerve
motor (somatic & parasym.)

Question 14

CN IV

Answer 14

trochlear nerve
motor

Question 15

CN V

Answer 15

trigeminal nerve
both

Question 16

CN VI

Answer 16

abducent nerve
motor

Question 17

CN VII

Answer 17

facial nerve
both (spec.sensory, somatic motor & parasym.)

Question 18

CN VIII

Answer 18

vestibulocochlear nerve
sensory (special)

Question 19

CN IX

Answer 19

glossopharyngeal nerve
both (spec.sensory, somatic motor & parasym.)

Question 20

CN X

Answer 20

vagus nerve
both (somatic sensory, somatic motor & parasym.)

Question 21

CN XI

Answer 21

spinal accessory nerve
motor

Question 22

CN XII

Answer 22

hypoglossal nerve
motor

Question 23

Where Cranial Fossae Foraminae for CNs to enter/exit cranial cavity:

Answer 23

Question 24

Course of a Cranial Nerve

Answer 24

Question 25

The Spinal Cord

Answer 25

Passes through foramen magnum

Protected by vertebral canal

Has 4 segments:
cervical
thoracic
lumbar
sacral/coccygeal

Has 2 enlargements
cervical
lumbosacral

Connects bilaterally with spinal nerves
8 cervical - C1-C8
12 thoracic - T1-T12
5 lumbar - L1-L5
5 sacral - S1-S5
1 coccygeal - Co
spinal cord ends at L1/L2 IV disc level
conus medullaris
Adult vertebral column is longer than the adult spinal cord
lumbar and sacral spinal nerve roots have to descend in the vertebral canal to their respective intervertebral foraminae
cauda equina (horse’s tail)

Question 26

How are Spinal nerves named?

Answer 26

• according to the vertebrae above it
• except in the cervical region, where
  they are named according to the
  vertebrae below it
• C8 spinal nerve exits between C7 and T1
  vertebrae

Question 27

Vertebral Column

Answer 27

33 vertebrae in total
7 cervical
12 thoracic
5 lumbar
5 sacral
fused to form 1 sacrum
4 coccygeal
fused to form 1 coccyx

Question 28

Rules of spinal nerve anatomy:

Answer 28

• spinal nerves supply the soma (body wall)
• located only within the intervertebral foramina
• from the intervertebral foramina they connect with
• structures of the soma via rami
• the spinal cord via roots and rootlets