Chapter 15: Autonomic Nervous System

Question 1

motor division of the peripheral nervous system can be divided into

Answer 1

Somatic NS and Autonomic NS (ANS).

Question 2

Autonomic NS (ANS).

Answer 2

also called the involuntary NS and is key in maintaining homeostasis.

It helps control various glands as well as smooth and cardiac muscle, usually without us being aware of it

Question 3

Somatic motor pathway:

Answer 3

• Motor neuron cell bodies are in CNS.

* Axons extend to skeletal muscles via cranial or spinal nerves.

Question 4

Autonomic motor pathway:

Answer 4

Involves 2 neurons in sequence.
•First neuron has its cell body located in brainstem or spinal cord
- It is called preganglionic.
- It terminates in a ganglion, where it synapses with the second neuron.
• Second neuron has its cell body located in a ganglion outside the CNS.
- It’s called postganglionic.
- It terminates in an effector organ.

Question 5

ANS Divisions

Answer 5

i) Sympathetic (SNS)

ii) Parasympathetic (PNS)

Question 6

The divisions of the ANS differ in:

Answer 6

1) Location of neurons/ganglia
2) Neurotransmitters used
3) Effects on target organs
4) Receptors used

Question 7

SNS v. PNS: Location of neurons/ganglia

Answer 7

• The preganglionic cell bodies originate in different regions of the spinal cord:
SNS: thoracic and lumbar regions.
PNS: brainstem & sacral regions.

• The ganglia are also found in different areas:
SNS: close to spinal cord.
PNS: in wall of target organ.

• As a result, the SNS has short preganglionic fibers, and long postganglionic fibers.
• The PNS has long preganglionic fibers, and short postganglionic fibers.

Question 8

SNS v. PNS: Neurotransmitters used

Answer 8

• The preganglionic neurons of both divisions release acetylcholine (ACh).

• The postganglionic neurons differ:
SNS: most postganglionic neurons release norepinephrine (NE).
PNS: postganglionic neurons release ACh.

Question 9

SNS v. PNS: Effects on target organs

Answer 9

• Often their actions are antagonistic. (e.g. heart)
• Occasionally their actions can be complimentary. (e.g. sexual function)

SNS

• Called the “flight or fight” division.
• Is dominant during vigorous activity.

PNS

• Called the “rest and digest” division.
• Is dominant during resting periods.

Question 10

SNS v. PNS: Receptors used

Answer 10

SNS

• Targets have “adrenergic” receptors.
• Response depends on type present: α or β-receptors.

PNS

• Targets have “cholinergic” receptors.
• Two types:
  i) Nicotinic (all postganglionic neurons)
  ii) Muscarinic (all PNS target organs)

Question 11

ANS Disorders: Hypertension

Answer 11

high blood pressure, over active vasoconstriction response, heart works harder, causes more wear and tear on walls

Question 12

ANS Disorders: Raynaud’s disease

Answer 12

intermittent attacks causing skin on fingers and toes turn blue and painful. Blood vessels being constricted more than they should so not enough blood getting to fingers, tigered by cold or emotional stress

Question 13

ANS Disorders: Autonomic dysreflexia

Answer 13

life-threatening, uncontrolled activation of autonoetic neurons. Triggered by painful stimulus to skin or overfilled organ like bladder. Arterial blood pressure skyrockets and can lead to blood vessel bursting in brain leading to stroke. Tends to happen in 1st year after spinal injury or in quadriplegics.