1.3 Somatic nervous system

Question 1

What are afferent nerves of the somatic nervous system involved in?

Answer 1

Reception of internal and external stimuli such as touch, heat, pain, hearing and sight

Question 2

How is incoming information coordinated?

Answer 2

By the spinal cord, somatomotor cortex (receives voluntary information/afferent fibres) and the cerebellum to achieve skilled motor programs

Question 3

What is ataxia?

Answer 3

Jerky movement

Question 4

Where do efferent nerves transmit impulses from?

Answer 4

CNS to the skeletal muscles causing contraction

Question 5

What are somatosensory fibres made up of?

Answer 5

Pseudopolar neurons

Question 6

What are somatomotor fibres made up of?

Answer 6

Unipolar neurons

Question 7

How does sensory reception occur?

Answer 7

Pain sensory inputs to SC and brain
SC sends a response to contract flexors to withdraw
SC sends information to brain to initiate voluntary motor control
- pinching of the web between toes of dog

Question 8

How does the motor response occur?

Answer 8

Somatomotor cortex always recruits the cerebellum = fine tuned response

• upper motor neurons of the somatomotor cortex and brain stem pathways make contact with spinal motor neurons
• Initiate voluntary movement and modulate muscle or reflex activity

Question 9

Name receptors in the somatic nervous system

Answer 9

Meisnners corpuscles - skin for light touch
Merkel’s disks - skin for touch and texture
Pacinian corpuscle - pain and deep pressure
Ruffini corpuscle - stretch/kinesthesia
Nerve endings in joints - position

Question 10

What is the reflex arc?

Answer 10

Neural pathway that mediates a reflex action

• sensory inputs do not pass directly into the brain but the synapse in the spinal cord
• quicker as spinal motor neurones will be activated without the delay of routing signals through the brain

Question 11

What are the neural connections through the spinal cord?

Answer 11

Sensory receptor → sensory neuron → spinal cord → interneuron (can be responsible for inhibiting contraction of antagonistic muscles) → motor neuron → effector organ

Question 12

What occurs during a patellar tendon test?

Answer 12

1. Tap/bend the patellar tendon
2. Stretch receptors in muscle stimulated
3. Sensory neuron in muscle send signal in spinal cord
4. Spinal cord detects and sends a response
5. Motor neuron carries response to muscle from spinal cord
6. Muscle contracts