Chapter 15: The Autonomic Nervous System

Question 1

The autonomic nervous system

Answer 1

Responsible for involuntary processes in the body that are key in maintaining homeostasis.
Helps control smooth and cardiac muscle.

Ex. Breathing, heart rate

Question 2

Autonomic motor pathway

Answer 2

Involves 2 neurons in a sequence

Neuron 1: Preganglionic - has its cell body located in the brainstem or spinal cord. It ends in a ganglion and synapses with the second neuron.

Neuron 2: Postganglionic - has its cell body located in a ganglion outside the CNS. It ends at the effector organ

Question 3

Ganglion

Answer 3

A collection of neuron cell bodies in the PNS

Question 4

How do the sympathetic and parasympathetic nervous systems differ?

Answer 4

Differ in:
- location of neurons and ganglia
- neurotransmitters used
- effects in target organs
- receptors used

Question 5

Where is the location of neurons/ganglia in the sympathetic and parasympathetic nervous systems

Answer 5

SNS:
- neurons start in the thoracic and lumbar regions
- ganglia near the spinal cord
(Results in short preganglionic fibres and long postganglionic fibres)

PNS:
- neurons start in the brainstem and sacral regions (usually vagus nerve)
- ganglia in wall of the target organ
(Results in long preganglionic fibres and short postganglionic fibres)

Question 6

What neurotransmitters are used in the sympathetic and parasympathetic nervous systems?

Answer 6

Preganglionic neurons in both SNS and PNS release acetylcholine (ACh), but differ in what the postganglionic neurons release.

SNS:
- postganglionic neurons release norepinephrine (adenergic)

PNS:
- postganglionic neurons still release acetylcholine (cholinergic)

Question 7

What are the effects of target organs in the sympathetic and parasympathetic nervous systems?

Answer 7

SNS:
- “fight or flight” division
- it is dominant during vigorous activity
Ex. Increase heart rate, decrease digestion

PNS:
- “rest and digest” division
- it is dominant during resting periods
Ex. Increase digestion, decrease heart rate

Question 8

What receptors are used in the sympathetic and parasympathetic nervous systems?

Answer 8

SNS:
- adrenergic receptors that will only bind to norepinephrine neurotransmitters.
- response depends on type present: alpha or beta receptors

PNS:
- cholinergic receptors that will only bind to acetylcholine neurotransmitters
2 types
1. Nicotinic - in all postganglionic neurons (whenever ACh binds to nicotine, it is always stimulatory)
2. Muscarinic in all PNS target organs. (Produces either a stimulatory or inhibitory response)

Question 9

Dual innervation

Answer 9

Both the sympathetic and parasympathetic nervous systems send signals to the same organs. But most of the times they have opposite effects on the organs.

One can become more dominant based on what activity you’re going through
Ex. Sympathetic increase when riding a bike. Parasympathetic increase when digesting food

Question 10

Cholinergic fibres

Answer 10

Fibres/neurons that release acetylcholine

Such as both preganglionic neurons, and the PNS postganglionic neuron

Question 11

Adrenergic fibres

Answer 11

Fibres/neurons that release norepinephrine

Such as the SNS postganglionic neurons

Question 12

Hypertension

Answer 12

A disorder of the autonomic nervous system which produced chronic high blood pressure

Question 13

Raynaud’s disease

Answer 13

A condition of the autonomic nervous system in which the on fingers and toes get blue-white and become very cold because the blood vessels to them are constricted.

Question 14

Autonomic dysreflexia

Answer 14

A life threatening disorder of the autonomic nervous system in which involves uncontrolled activation of autonomic neurons.