The Autonomic Nervous System

Question 1

Regarding the autonomic nervous system (true or false):

It provides conscious control of skeletal muscle contraction

Answer 1

False. The autonomic nervous system does not control skeletal muscle, it controls visceral function but this is involuntary.

Question 2

Regarding the autonomic nervous system (true or false):

It is anatomically divided into three divisions

Answer 2

False. It is anatomically divided into the sympathetic and the parasympathetic systems.

Question 3

Regarding the autonomic nervous system (true or false):

Sympathetic and parasympathetic efferent pathways each contain two neurons

Answer 3

True. The sympathetic and parasympathetic efferent pathways contain two neurons: preganglionic and postganglionic.

Question 4

Regarding the autonomic nervous system (true or false):

Postganglionic sympathetic efferent pathways tend to be short

Answer 4

False. In the sympathetic nervous system, the autonomic ganglia tend to be distant from the effector organs while in the parasympathetic nervous system, the ganglia are very close to, or in, the effector organs.

Question 5

Regarding the autonomic nervous system (true or false):

Preganglionic parasympathetic efferent pathways tend to be long

Answer 5

True.

Question 6

Regarding the autonomic nervous system (true or false):

Sympathetic ganglia are found exclusively in the sympathetic chains adjacent to the spinal cord

Answer 6

False. The coeliac and hypogastric ganglia are usually thought of as sympathetic.

Question 7

Regarding the autonomic nervous system (true or false):

Preganglionic sympathetic nerves leave the spinal cord via grey rami communicantes

Answer 7

False. Preganglionic sympathetic nerves leave the spinal cord via white rami communicantes which are myelinated.

Question 8

Regarding the autonomic nervous system (true or false):

Postganglionic parasympathetic nerves supplying the head and neck originate in the stellate ganglion

Answer 8

False. Parasympathetic ganglia are situated within or close to effector organs. The stellate ganglion contains only sympathetic ganglia.

Question 9

Regarding the autonomic nervous system (true or false):

The splanchnic nerves contain preganglionic sympathetic nerve fibres

Answer 9

True

Question 10

Regarding the autonomic nervous system (true or false):

The parasympathetic outflow from the CNS is via cranial and sacral spinal nerves

Answer 10

True

Question 11

Concerning the autonomic nervous system (true or false):

Nicotinic acetylcholine receptors are found on the post-synaptic nerve cell membranes in parasympathetic and sympathetic ganglia

Answer 11

True. Acetylcholine is the transmitter at all autonomic ganglia. It acts upon nicotinic receptors.

Question 12

Concerning the autonomic nervous system (true or false):

Adrenaline is the major transmitter at the junction between sympathetic nerve endings and effector organs

Answer 12

False. Noradrenaline is the transmitter released by postganglionic sympathetic neurons at the neuroeffector junction. Adrenaline is released from the cells of the adrenal medulla, which may be thought of as modified postganglionic sympathetic neurons.

Question 13

Concerning the autonomic nervous system (true or false):

α2 receptors are predominantly post-synaptic and inhibit the action of noradrenaline

Answer 13

False. α2 receptors are predominantly presynaptic at the neuroeffector junction. Stimulation inhibits further release of noradrenaline by the presynaptic neuron and controls its release by negative feedback.

Question 14

Concerning the autonomic nervous system (true or false):

Stimulation of β2 receptors by noradrenaline mediates an increase in heart rate

Answer 14

False. β1 receptors are found in the heart. Stimulation increases heart rate.

Question 15

Concerning the autonomic nervous system (true or false):

Postganglionic sympathetic fibres innervating sweat glands release acetylcholine at the neuroeffector junction

Answer 15

True. Sweat glands are innervated by cholinergic sympathetic fibres.

Question 16

Which of the following statements best describes the anatomical organisation of the autonomic nervous system?

A. Sympathetic outflow via the thoracolumbar spinal cord, parasympathetic outflow via cranial nerves, enteric outflow via the sacral spinal cord and autonomic ganglia in the sympathetic chain
B. Sympathetic outflow via the thoracolumbar spinal cord, parasympathetic outflow via cranial nerves and autonomic pathways consisting of one neuron linking the CNS to the effector organ
C. Sympathetic outflow via the thoracolumbar spinal cord, parasympathetic outflow via cranial and sacral spinal nerves, sympathetic ganglia in the sympathetic chain and prevertebral ganglia and parasympathetic ganglia within, or close to, effector organs
D. Sympathetic outflow via the thoracolumbar spinal cord and cranial nerves, parasympathetic outflow only from cranial nerves, sympathetic ganglia in the sympathetic chain and the enteric nervous system, which has no well-defined connection with the CNS

Answer 16

C. The anatomical organisation of the autonomic nervous system can be described as:

• Sympathetic outflow via the thoracolumbar spinal cord
• Parasympathetic outflow via cranial and sacral spinal nerves
• Sympathetic ganglia in the sympathetic chain and prevertebral ganglia
• Parasympathetic ganglia within, or close to, effector organs

A. Incorrect. There is no well-defined outflow for the enteric nervous system although it has connections with both the parasympathetic and sympathetic systems. Only the sympathetic ganglia are within the sympathetic chain. Parasympathetic ganglia are within, or close to, the effector organs.

B. Incorrect. The sympathetic and parasympathetic pathways have two neurons linking the CNS to the effector organ. The parasympathetic outflow is also via sacral spinal nerves.

D. Incorrect. There is no sympathetic outflow from the cranial nerves. It is only from the thoracolumbar spinal cord. Parasympathetic outflow is from cranial nerves and also sacral spinal nerves.

Question 17

A hypovolaemic patient develops tachycardia, increased myocardial contractility and peripheral vasoconstriction. Which statement best explains the mechanism of this response?

A. Cardiac sympathetic nerves release adrenaline which acts upon ß1 receptors. Peripheral sympathetic nerve endings release noradrenaline which acts upon vascular smooth muscle α receptors
B. Cardiac sympathetic nerves release noradrenaline which acts upon cardiac β1 receptors. Vasoconstriction is mediated by sympathetic nerves which activate α2 receptors on vascular smooth muscle
C. Sympathetic nerves release noradrenaline, which acts upon cardiac β1 receptors and vascular α1 receptors. Adrenaline from the adrenal medulla also acts upon β1 receptors and α1 receptors
D. These responses are due to the release of adrenaline into the circulation by the adrenal medulla acting on cardiac β1 receptors and vascular α receptors

Answer 17

C.

A. Incorrect. Cardiac sympathetic nerves release noradrenaline not adrenaline.

B. Incorrect. Vasoconstriction is caused by noradrenaline released from sympathetic nerve endings acting upon α1 receptors.

D. Incorrect. Adrenaline released from the adrenal medulla does contribute to the response but it is also mediated by sympathetic nerves supplying the heart and vessels.