Structure And Function Of The Nervous System

Question 1

Subdivisions of the nervous system:

Answer 1

CNS:
- Brain
- Spinal cord
- Central controller

PNS:
- All nerves not in CNS
- Spinal nerves
- Cranial nerves
- Autonomic nerves
- Wiring

Question 2

Neurone definition and structure:

Answer 2

Collection of nerve cell bodies:
- CNS = Nucleus
- PNS = Ganglion

Dendrites: Receive and conduct info towards cell body
Axon: Longest structure, conducts info away from cell body, surrounded by myelin sheath

Question 3

Nerve definition

Answer 3

Bundle of axons wrapped in connective tissue

Travel to/from same region or structure

Bundle of axons can leave as a branch

Question 4

Named nerve:

Answer 4

Larger nerves supplying the body wall, body cavities and organs

Question 5

Soma includes:

Answer 5

Body walls
Back
Limbs
Diaphragm

Question 6

What are sensory nerves and motor nerves

Answer 6

Motor:
Action potential towards body wall, body cavity, or organ

Sensory: Action potential towards brain

Question 7

6 functions of nerve fibre:

Answer 7

Each nerve can only have ONE function

Somatic sensory
Somatic motor
Special sensory
Visceral afferent
Sympathetic
Parasympathetic

Neurones can be mixed: Contains multiple nerves with different functions

Question 8

Anatomy of brain:

Answer 8

Outermost layer of cerebral hemispheres (cortex):
- Gyri (folds/bumps)
- Sulci (groves between gyri)

4 lobes:
- Frontal
- Paietal
- Occipital
- Temporal

Question 9

Cranial nerves:

Answer 9

I - Olfactory - Sensory (special)
II - Optic - Sensory (special)
III - Oculomotor - Motor
IV - Trochlear - Motor
V - Trigeminal - Both
VI - Abducent - Motor
VII - Facial - Both
VIII - Vestibulocochlear - Sensory (special)
IX - Glossopharyngeal - Both
X - Vagus - Both
XI - Spinal accessory - Motor
XII - Hypoglossal - Motor

Question 10

Describe cranial fossae:

Answer 10

Foraminae: Openings for CNs to enter/exit cranial cavity

Sensory nerves enter cranial cavity, motor nerves exit cranial cavity

Question 11

Describe the foraminae of the base of the skull and state which cranial nerves pass through which foraminae:

Answer 11

Anterior cranial fossae:
- Cribriform plate of the ethmoid bone: I

Middle:
- Optic canal: II
- Superior orbital fissure: III - VI

Posterior:
- Internal acoustic meatus: VII & VIII
- Jugular foramen: IX - XI
- Hypoglossal canal: XII

Question 12

Summarise the anatomy of the vertebral column and spinal cord:

Answer 12

Passes through foramen magnum

Protected by vertebral canal

4 segments:
- Cervical
- Thoracic
- Lumbar
- Sacral or coccygeal

2 enlargements:
- Cervical
- Lumbosarcal

Question 13

Describe spinal nerve roots and rootlets:

Answer 13

Rootlets that stem from grey matter, come together to form roots

Swelling only found on dorsal root

Anterior and posterioir route come together to form spinal nerve

Question 14

Spinal nerves:

Answer 14

Named according to vertebrae above it:
- Except cervical which are named according to vertebrae below it (C8 spinal nerve exists between C7 and T1 vertebrae)

Spinal nerves exit intervertebral foramen

Question 15

Spinal nerve rami and the 4 body plexuses:

Answer 15

Rami stem from spinal nerve:
- Posterior rami are smaller than anterior and supply a small posterior strip
- Anterior supplies most of body wall (anterior and lateral) and all the limbs

4 body plexus (intertwining of anterior rami nerve fibres):
- Cervical (posterior scalp, neck wall, daiphragm)
- Brachial (Upper limb)
- Lumbar (Lower limb)
- Sacral (Lower limb, gluteal region)

Question 16

Relate the spinal nerves to the dermatome map and give examples:

Answer 16

Deramatomes: Area of skin supplied by anterior and posterior rami

T4 dermatome - Nipples

T10 dermatome - Umbilicus

Question 17

List the sensory modalities the soma can perceive and name the receptor types involved:

Answer 17

Mechanoreceptors sense:
- Coarse and fine touch
- Vibration
- Proprioception

Thermoreceptors sense:
- Temperature

Nociceptors sense:
- Pain

Question 18

Explain the general route a sensory action potential or motor action potential takes

Answer 18

Sensory:
Spinal nerve > Posterior root > Posterior rootlets > posterior horn of spinal cord

Motor:
Anterior horn of spinal cord (larger than posterior) > Anterior rootlets > Anterior root > Spinal nerve

Question 19

Define a reflex arc (Example - L2):

Answer 19

1. Mechanoreceptors in L2 dermatome are stimulated
2. APs are conducted along axons in L2 anterior ramus
3. L2 axons weave their way through lumbar plexus to L2 spinal nerve
4. APs conducted via same axons that pass through the posterior root ganglion, roots and rootlets
5. APs arrive at posterior horn of L2
6. APs cross over midline and ascend towards brain
7. Somatic motor axons cross over in brain stem and descend to L2 anterior horn
8. APs conducted along axons in anterior rootlets > roots > spinal nerves
9. APs conducted along axons in named nerves of lumbar plexus
10. Synapse onto skeletal muscle of lower limb causes it to contract

Question 20

Role of visceral afferent nerve fibres

Answer 20

Carry action potentials from organs to the CNS and generally travel alongside sympathetic fibres

Question 21

Summarise the general anatomy of the sympathetic and parasympathetic systems:

Answer 21

Outflow
Sympathetic - Leaves CNS via T1- L2 spinal nerves
Parasympathetic - Leaves CNS via cranial nerves 3,7,9,10 or sacral spinal nerves

Routes
Sympathetic - Spincal cord > Sympathetic chains > Organs/Sweat glands/Arterioles
Parasympathetic - Cranial/Sacral spinal nerves > Glands/organs

Effects
Sympathetic - Fight or flight
Parasympathetic - Rest and digest

Question 22

Myelin sheath production

Answer 22

PNS: Schwann cells
CNS: Oligodendrocites