Drugs acting on the Autonomic nervous System

Question 1

3 features of the effect autonomic nerves:

Answer 1

• Transmit impulses from the central nervous system to peripheral organ systems
• Control heart, blood vessels, gut, bladder, eyes, exocrine and endocrine glands.
• Response includes smooth muscle contraction/relaxation, glandular secretion etc.

Question 2

What are the parasympathetic preganglionic fibres?

Answer 2

Myelinated fibres that leave the brainstem and sacral segments of the spinal cord, and travel long distances to synapse with postsynaptic fibres in ganglia located in efferent organs.

Question 3

What are the parasympathetic postganglionic fibres?

Answer 3

Unmyelinated much shorter than preganglionic, most located near to or within effector organs.

Question 4

How do preganglionic nerves rising from the brainstem travel?

Answer 4

Travel in cranial nerves such as oculomotor nerve (3) the facial nerve (7) the glossopharyngeal nerve (9) and the vagus nerve (10)

Question 5

What parasympathetic function does the oculomotor (3rd crainial nerve) innervate?

Answer 5

The sphincter muscles of the iris and ciliary muscles of the eye.

Question 6

What parasympathetic function does the facial (7rd cranial nerve) innervate?

Answer 6

The lacrimal, nasal, palatine, sublingual and submandibular glands.

Question 7

What parasympathetic function does the glossopharyngeal (9th cranial nerve) innervate?

Answer 7

the parotid glands

Question 8

What parasympathetic function does the vagus (10th cranial nerve) innervate?

Answer 8

travels through the thoracic and abdominal cavities to innervate the heart, lungs, much of the GI tract and kidneys.

Question 9

4 features of sympathetic preganglionic fibers:

Answer 9

• Myelinated
• Cell bodies in the lateral horns of the spinal segments T1-L2 ‘thoraco-lumbar outflow’
• sympathetic paravertebral ganglionic chains run from cervical to the sacral region.
• Synapse in ganglia with a postsynaptic fibre.

Question 10

What are 3 features of the sympathetic postganglionic fibres?

Answer 10

• unmyelinated
• much longer than preganglionic fibres
• run all the way to the effector organ.

Question 11

What do some of the sympathetic preganglionic fibers do instead of synapsing in the sympathetic chains?

Answer 11

Terminate in separate cervical or abdominal ganglia, or travel in the greater splanchnic nerve and directly synapse with chromaffin cells in the adrenal medulla.

Question 12

What is the function of chromaffin cells?

Answer 12

Adrenal medulla chromaffin cells synthesise and store catecholamines

(sympathetic postganglionic nerve endings)

Question 13

Why is most noradrenaline in chromaffin cells converted to adrenaline? P

Answer 13

Presence of an additional enzymes.

Question 14

How does the medulla Respond to nervous impulses in the sympathetic cholinergic preganglionic fibres?

Answer 14

Transforming the neural impulses into hormonal secretion into the circulation, which allows large quantities of catecholamines to be released in situations involving physical or psychological stress.

Question 15

What is the neurotransmitter and receptors for preganglionic parasympathetic nerves?

Answer 15

• Acetylcholine (ACh) is the neurotransmitter
• Acts at nicotinic receptors at the preganglionic synapse.

Question 16

What is the neurotransmitter and receptors for postganglionic parasympathetic nerves?

Answer 16

• acetylcholine (ACh) is the neurotransmitter
• Acts at muscarinic receptors at effector organs.

Question 17

How can concentration of neurotransmitter in the synaptic cleft be rapidly reduced?

Answer 17

By enzymatic degradation or reuptake of the neurotransmitter.