1 Organisation of the Nervous System

Question 1

Q: How is the nervous system structurally divided?

Answer 1

A: 2 parts

• central nervous system (brain and spinal cord)
• peripheral nervous system (nerves and ganglia outside the brain and spinal cord)

Question 2

Q: What are ganglions?

Answer 2

A: clusters of neuronal cell body

Question 3

Q: Draw a diagram summarising the organisation of the nervous system. Identify efferent and afferent flow.

Answer 3

A: brain and spinal cord = 1. CNS

2. PNS
3. sensory division // 4. motor division
4. autonomic motor division // 6. somatic (motor) division (spinal nerves and cranial nerves)

5 goes into

7. sympathetic division (spinal nerves only)
8. parasympathetic division (spinal nerves and cranial nerves)

go into 3

9. somatic sensory
10. autonomic sensory

1->2->4->5+6
5->7+8 (efferent)

9+10-> 3->2->1 (afferent)

Question 4

Q: What is the PNS functionally divided into? (2-1,3)

Answer 4

A: Somatic (motor) PNS
-Controls motor and sensory function of the body wall e.g. skin and skeletal muscles

Autonomic Nervous System

• Has Sympathetic and Parasympathetic arms
• Also called: Visceral NS, Vegetative NS, Involuntary NS
• controls function of viscera (internal organs)

Question 5

Q: Differentiate between efferent and afferent axons. What are interneurones?

Answer 5

A: efferent= propagate AP from brain and spinal cord to the periphery (motor neurones)

afferent= propogate AP towards brain and spinal cord from PNS (sensory neurones)

interneurones= CNS neurons that synapse with other CNS neurons within the brain and spinal cord (can be either of the top 2)

Question 6

Q: How do axons enter and leave the CNS?

Answer 6

A: through pairs of spinal nerves and cranial nerves

Question 7

Q: Name the 3 main parts of the brain.

Answer 7

A: 1. cerebral cortex (cerebrum)

2. cerebellum (hind brain)
3. brain stem

Question 8

Q: Describe the cerebrum. (2)

Answer 8

A: -made of 2 hemispheres

-each receives sensory information from and controls movement on opposite of body

Question 9

Q: What does the cerebellum control?

Answer 9

A: coordination of movement

Question 10

Q: Describe the brain stem. (2) Function? Damage?

Answer 10

A: -most primitive part
-densely packed fibres

• regulates vital functions (eg consciousness and breathing)
• damage here can be fatal

Question 11

Q: What is the spinal cord? Includes?

Answer 11

A: -string of nerve tissue from below brain to first lumbar vertebrae

• grey matter
• white matter

Question 12

Q: Where does the CNS end in terms of the spinal cord? What emerges from the spinal cord? what are they part of?

Answer 12

A: margins of spinal cord

dorsal and ventral roots (part of the PNS)

Question 13

Q: What do spinal nerves contain? (3) How? What is the whole nerve surrounded by? components?

Answer 13

A: -both afferent and efferent axons = bundled into fascicles surrounded by perineurium
-blood vessels

• tough epineurium capsule
• individual axons are also wrapped with myelin and endoneurium (though some are unmyelinated eg pain neurones)

Question 14

Q: What is a neurone function? How?

Answer 14

A: transmit and receive AP/ stimulate target tissue eg induce contraction of smooth muscle/secretion from a gland

when AP reaches a neuronal chemical synapse -> neurotransmitters released by a presynaptic terminal bind to post-synaptoc receptors of the neuron/muscle/gland it is synapsing with

Question 15

Q: Apart from neurones, name 4 other cell types essential to nervous system development, microanatomy and function.

Answer 15

A: glial cells

• oligodendroglia
• astroglia
• microglia

Question 16

Q: How does regeneration differ between PNS and CNS? (3,4)

Answer 16

A: -axons in peripheral nerves can regenerate after injury
-recovery is often compromised by non-specific target reinnervation and aberrant axon sprouting (eg can lead to neuropathic pain)

• axons in CNS are unable to regenerate over long enough distances to be useful. This is because:
• presence of inhibitory molecules in the CNS but not in the PNS (e.g. differences in myelin)
• Absence of guidance cues that stimulate axon growth during development
• Some loss of intrinsic axon growth capabilities by the neurons

Question 17

Q: Are neuronal cell bodies in grey or white matter? therefore the other?

Answer 17

A: grey

white comprises ascending and descening axon tracts to and from the brain

Question 18

Q: Is grey or white matter peripheral?

Answer 18

A: white is peripheral and grey is central

Question 19

Q: What do sensory inputs activate? where? What occurs?

Answer 19

A: sensory neurones in the spinal cord grey matter

transmit AP upwards to sensory cortex of the brain (ascending tracts)

Question 20

Q: Where do neurones in the motor cortex extend? What occurs?

Answer 20

A: -opposite direction to sensory inputs
-extend downward to synapse with spinal motor neurones

transmit AP for voluntary movement (descending tracts)

Question 21

Q: What’s required for a reflex motor response? (3) Not?

Answer 21

A: only the somatic sensory inputs to, (interneurones) and motor outputs from spinal cord

NOT communication with the sensorimotor cortex