Autonomic Nervous System

Question 1

Where do axons of the preganglionic neurons of the sympathetic system emerge?

Answer 1

T1 to L2 of the spinal cord.

Question 2

How would you describe the relative length of the axons of preganglionic sympathetic neurons?

Answer 2

Short, since the ganglion it synapses at is close to the spinal cord.

Question 3

What neurotransmitter is released by preganglionic sympathetic neurons, and what type of receptor does it activate?

Answer 3

Acetylcholine; nicotinic receptor.

Question 4

How would you describe the relative length of the axons of postganglionic sympathetic neurons?

Answer 4

Long, since it has to travel from the ganglion near the spinal cord.

Question 5

What neurotransmitter is released by postganglionic sympathetic neurons, and what type of receptor does it activate?

Answer 5

Norepinephrine; adrenergic receptor.

Question 6

True or false: a preganglionic sympathetic neuron typically synapses with only one postganglionic neuron.

Answer 6

False. A preganglionic sympathetic neuron can affect many postganglionic sympathetic neurons, allowing for many effector organs to be activated at the same time.

Question 7

How does the adrenal medulla react in response to sympathetic innervation?

Answer 7

The adrenal medulla received input from preganglionic sympathetic neurons. Since it cannot pass any messages on as neurons can, it releases epinephrine (adrenaline) into the blood.

Question 8

Where do axons of the preganglionic neurons of the parasympathetic system emerge?

Answer 8

CN III, CN VII, CN IX, and CN X, as well as S2 to S4.

Question 9

How would you describe the relative length of the axons of preganglionic parasympathetic neurons?

Answer 9

Long, since the ganglion it synapses at is close to or within the effector organ.

Question 10

What neurotransmitter is released by preganglionic parasympathetic neurons, and what type of receptor does it activate?

Answer 10

Acetylcholine; nicotinic receptor.

Question 11

How would you describe the relative length of the axons of postganglionic parasympathetic neurons?

Answer 11

Short, since the ganglion it comes from is already near or within the effector organ.

Question 12

What neurotransmitter is released by postganglionic parasympathetic neurons, and what type of receptor does it activate?

Answer 12

Acetylcholine; muscarinic receptor.

Question 13

True or false: a preganglionic parasympathetic neuron typically synapses with only one postganglionic neuron.

Answer 13

True. This allows discrete response of the parasympathetic system. If the parasympathetic division were highly branched (as the sympathetic division is), any stimulus for the parasympathetic division would stimulate undesirable effects such as involuntary urination.

Question 14

What organs are innervated by only the sympathetic division?

Answer 14

Adrenal medulla, kidney, pilomotor muscles, and sweat glands. Blood pressure is also controlled only by the sympathetic division.

Question 15

What are three types of chemical signalling between cells?

Answer 15

Hormones, local mediators, and neurotransmitters.

Question 16

Briefly describe how hormones exert their effect.

Answer 16

Endocrine cells secrete hormones into the bloodstream, where they are transported throughout the body and thus are able to exert effects broadly.

Question 17

Briefly describe how local mediators exert their effect.

Answer 17

Most cells are able to secrete chemicals that act only locally. These chemicals are rapidly destroyed or removed, so they do not enter the blood and their effect is limited to the local area. Histamine and prostaglandins are examples of local mediators.

Question 18

What are the six neurotransmitters most commonly involved in therapeutically useful drugs?

Answer 18

Norepinephrine/epinephrine, acetylcholine, dopamine, serotonin, histamine, and GABA.

Question 19

What is meant by the term “cholinergic?”

Answer 19

It means that the neurotransmitter acting at that location is acetylcholine.

Question 20

What is meant by the term “adrenergic?”

Answer 20

It means that the neurotransmitter acting at that location is either norepinephrine or epinephrine (adrenaline is another name for epinephrine).

Question 21

What areas does the enteric nervous system innvervate?

Answer 21

The GI tract, pancreas, and gallbladder.

Question 22

What is the function of the enteric nervous system?

Answer 22

It controls the motility, exocrine and endocrine secretions, and microcirculation of the GI tract.

Question 23

How is the CNS involved in regulation of the ANS?

Answer 23

Sensory information is sent to the hypothalamus, medulla oblongata, and spinal cord, in order to devise an appropriate response.

Question 24

Although postganglionic sympathetic innervation is usually accomplished by one particular neurotransmitter, what an example of a body response that is mediated by another?

Answer 24

Sweat; mediated by release of acetylcholine by postganglionic sympathetic neurons.