Organisation of the Peripheral Nervous System

Question 1

Somatic nerves innervate what?

Answer 1

Skeletal muscle

Question 2

What does the autonomic nervous system regulate?

Answer 2

Cardiac muscle, smooth muscle and glands

Question 3

What cells secrete epinephrine and norepinephrine?

Answer 3

Chromaffin cells

Question 4

What neurotransmitter do somatic neurons release?

Answer 4

Acetylcholine

Question 5

Explain the anatomy of a preganglionic neuron.

Answer 5

The axon of a preganglionic neuron has a small diameter and consists of myelinated type B fibers.

Question 6

Explain the anatomy of postganglionic neurons.

Answer 6

The axon of a postganglionic neuron has a small diameter and consists of unmyelinated type C fibers.

Question 7

What do preganglionic neurons do?

Answer 7

Relay nerve impulses from the CNS to autonomic ganglia.

Question 8

What do postganglionic neurons do?

Answer 8

Relay impulses from autonomic ganglia to visceral effectors.

Question 9

Which ganglia are associated with the parasympathetic division of the nervous system?

Answer 9

Terminal ganglia

Question 10

Which ganglia are associated with the sympathetic division of the nervous system?

Answer 10

Prevertebral ganglia

Question 11

Why do sympathetic ganglions have widespread effects over the entire body?

Answer 11

A sympathetic preganglionic fiber has many axon branches that synapse with 20 or more postganglionic neurons.
The postganglionic axons terminate in several visceral effectors thus leading to widespread effects over the whole body.

Question 12

Where do the cell bodies of the preganglionic sympathetic neurons located?

Answer 12

Lateral gray horns of the thoracic segments of the spine.

Question 13

Through what pathway do preganglionic sympathetic neurons run?

Answer 13

White ramus

Question 14

Through what pathway do postganglionic sympathetic neurons run?

Answer 14

Gray ramus

Question 15

Where are the cell bodies of parasympathetic preganglionic neurons found?

Answer 15

Nuclei of the brainstem

Lateral gray matter of the second and fourth sacral segments of the spine.

Question 16

Pelvic splanchnic nerves branch from which spinal nerves?

Answer 16

Second through to fourth sacral spinal nerves

Question 17

Muscarinic receptors bind to what?

Answer 17

ACh

Question 18

What receptor does norepinephrine stimulate most strongly?

Answer 18

Norepinephrine stimulates alpha receptors more strongly than beta receptors.

Question 19

Sweat glands receive what type of innervation?

Answer 19

Sympathetic innervation only

Question 20

What are the associated ganglia of the sympathetic nervous system?

Answer 20

Sympathetic trunk ganglia and prevertebral ganglia.

Question 21

What are the associated ganglia of the parasympathetic nervous system?

Answer 21

Terminal ganglia

Question 22

Explain the anatomy of A nerve fibers.

Answer 22

Large diameter, myelinated and are the fastest nerve fiber.

Question 23

B nerve fibres are found where?

Answer 23

Preganglionic ANS neurons

Question 24

C nerve fibres are found where?

Answer 24

Postganglionic ANS neurons

Question 25

C nerve fibres detect what?

Answer 25

Sensory/Pain fibres

Question 26

What are somatic senses?

Answer 26

Tactile sensation eg touch, pressure, pain, temperature, vibration.

Question 27

What are proprioceptive sensations?

Answer 27

Sense of the position of your limbs in space

Question 28

What do nociceptors do?

Answer 28

Respond to painful stimuli

Question 29

What receptor detects vibration?

Answer 29

Lamellated aka pacinian corpuscle

Question 30

What detects skin stretching and pressure?

Answer 30

Ruffini corpuscle

Question 31

What receptor detects onset of tight and light vibration?

Answer 31

Meissner corpuscle

Question 32

What receptor detects continuous touch and pressure?

Answer 32

Tactile disc

Question 33

What does bradykinin do?

Answer 33

Vasodilator also involved in detection of pain

Question 34

What is the neurotransmitter at the neuromuscular junction?

Answer 34

ACh

Question 35

Where are the acetylcholine receptors found at the NMJ?

Answer 35

On the motor end plate

Question 36

Outline the basic steps of how a nerve action potential initiates a muscle action potential at the NMJ.

Answer 36

1. Release of acetyl choline 2. Activation of ACh receptors 3. Production of the muscle action potential 4. Termination of ACh activity

Question 37

How is acetylcholine released into the synaptic cleft?

Answer 37

Arrival of a nerve impulse stimulates the opening of Ca2+ ion channels. Influx of calcium triggers exocytosis of vesicles containing ACh.

Question 38

What happens when ACh bind to it's receptor.

Answer 38

ACh receptors are ligand gated ion channels and so the ion channels open allowing influx of sodium across the membrane.

Question 39

How does the muscle action potential cause contraction?

Answer 39

Influx of Na+ makes the inside of the muscle fibre more positively charged thus triggering an action potential. The action potential then propagates along the sarcolemma of the muscle fibre to a system of T tubules, causing the sarcoplasmic reticculum to release it's stored Ca2+. Ca2+ causes the muscle fibre to contract.

Question 40

How is ACh activity terminated?

Answer 40

ACh is rapidly broken down by acetylcholinesterase in the synaptic cleft.

Question 41

How does Ca2+ cause muscle contraction?

Answer 41

Ca2+ binds to troponin causing tropmyosin to unwind and expose the myosin-binding sites on the actin filament. Myosin heads bind to actin and undergo power strokes and release. This causes muscle contraction.

Question 42

What lie in the lateral gray horns of the thoracic segments of the spine?

Answer 42

Preganglionic sympathetic neurons