Somatic Nervous System

Question 1

Two divisions of the nervous system + definitions

Answer 1

Central nervous system- consists of the brain and spinal cord
peripheral nervous system- consists of nerves that pass to and from the CNS

Question 2

Further peripheral nerve division

Answer 2

Spinal nerves- carrying information to and from the spine

cranial nerves- carrying information to and from the brain

Question 3

Different types of peripheral nerve cells

Answer 3

afferent nerves- sensory nerves

efferent nerves - motor nerves

Question 4

Further division of efferent nerves

Answer 4

somatic- voluntary movements, impulses travel to muscles

autonomic- involuntary movements, impulses travel to cardiac muscle, skeletal muscle and glands

Question 5

How many spinal nerves in total?

Answer 5

31

Question 6

How many from each group of spinal vertebrae?

Answer 6

8 cervical C1-C8
12 thoracic T1-T12
5 lumbar- L1-L5
5 sacral S1-S5
1 coccygeal

Question 7

How many cranial nerves ?

Answer 7

12 pairs

Question 8

Dermatome definition

Answer 8

a particular region of the body that each spinal nerve innervates

Question 9

Is there overlap between dermatomes?

Answer 9

Yes, a lot of overlap between the nerves supplying adjacent segments.

Question 10

Structure of somatic efferent motor fibres

Answer 10

• cell body is located in the motor cortex, brainstorm or spinal cord
• axon fibre projects to the spinal cord or outside to directly innervate effector organs
• synapse at neuromuscular junction at end plates on muscle fibres
• single neuron monosynaptic

Question 11

What is motor neuron disease + symptoms?

Answer 11

Group of progressive neurological disorders that destroy motor neurones causing a disruption in the signals between the lower motor neurones and limb muscles

limb muscle stiffness (spasticity) movements become slower, eventual paralysis§

Question 12

Two different types of somatic motor neurone

Answer 12

Upper motor neurones- originate from brain

lower motor neurones- originate from spinal cord

Question 13

Sensory nerve fibre structures

Answer 13

Have a specialised receptor on the end of the axon

Central cell body in dorsal root ganglia

dendrites- to synapse to relay neurone in CNS

Question 14

Sensory neurone function

Answer 14

Convey information to from receptors, such as temperature, touch, pain in skin, position sense and pain in joints and reflex control of movement in muscles, to the CNS

Question 15

Structure of dorsal root ganglion

Answer 15

left and right paired spinal nerves are formed from afferent sensory dorsal axons- the dorsal root and the motor ventral efferent axons- the ventral root.

Dorsal Root Ganglion is a group of cell bodies responsible for the transmission of sensory messages to the CNS.

The dorsal root enters the grey matter and the ventral root leaves the grey matter

Question 16

How is pain felt?

Answer 16

Nociceptive nerve fibres are activated by mechanical forces or by a variety of chemical mediators in the environment, that are released by tissue damage

Question 17

What happens if sensory neurones are damaged?

Answer 17

loss of sensation

Question 18

What is a visceral afferent fibre? where are cell bodies found?

Answer 18

Neurone that conducts sensory impulses, usually pain or reflex sensations, from the internal organs, glands and blood vessels to the CNS.

Dorsal root ganglia

Question 19

What nervous system are visceral afferent fibres a part of?

Answer 19

Autonomic, but neither sympathetic nor parasympathetic

Question 20

What are mixed nerves?

Answer 20

Nerves that contain both afferent and efferent axons and thus conduct both incoming sensory information and outgoing muscle commands in the same bundle.

Question 21

Are somatic nerve fibres myelinated or unmyelinated?

Answer 21

Most are myelinated and have a fast to medium velocity

Question 22

What fibres are unmyelinated?

Answer 22

C-type pain fibres