Anatomy and Physiology of the Autonomic Nervous System

Question 1

Subdivision of ANS

Answer 1

CNS
PNS
Somatic or Autonomic
Autonomic split into:
Parasympathetic & Sympathetic & Enteric

Question 2

Somatic nervous system

Answer 2

Conscious control of skeletal muscles

Question 3

Autonomic nervous system

Answer 3

Unconscious control of cardiac, smooth muscle and glands

Question 4

Axons of the somatic nervous system have:

Answer 4

A single myelinated axon extending from the CNS to the effector (skeletal muscle)

Question 5

Axons of the autonomic nervous system have:

Answer 5

A two neuron chain
The preganglionic (first) neuron extends to the ganglion
The postganglionic (second) neuron extends from ganglion to an effector organ

Question 6

Ganglia

Answer 6

Cell bodies of many peripheral autonomic neurones occur in clusters and form swellings on nerve trunks

Question 7

Axons that form synapses with ganglion cells are:

Answer 7

Preganglionic autonomic fibres

Question 8

Axons inner acting effector cells are:

Answer 8

Postganglionic autonomic fibres

Question 9

Neurotransmitters of the autonomic nervous system:

Answer 9

Preganglionic nerves: Acetylcholine (Cholinergic transmission)
Postganglionic nerves: Acetylcholine (Cholinergic transmission), Noradrenaline (Noradrenergic transmission)
Pre and Postganglionic nerves: Non-adrenergic non-cholinergic neurotransmission (NANC)

Question 10

Roles of autonomic nervous system

Answer 10

1. Conveys all outputs from the CNS to rest of body except motor inner action of skeletal muscle.
2. Regulates mostly non-voluntary processes in homeostasis, including: heartbeat, contraction of smooth muscle of various organs and blood vessels.
3. Sympathetic and Parasympathetic systems function separately. They have opposing effects in some states but not others.
4. Sympathetic activity increases in stress. Parasympathetic activity predominates during satiation and response.
   Influenced by sensory information via control centres in brain.

Question 11

Parasympathetic nervous system steps

Answer 11

Preganglionic axons emerge from cranial and sacral regions of CNS.
Preganglionic axons form synapses in ganglia near to/adjacent to/within effector tissues.
Sacral nerves form pelvic plexuses containing scattered ganglia and also abdominal viscera.
In general, parasympathetic preganglionic fibres are long and postganglionic fibres are short.

Question 12

Sympathetic nervous system steps

Answer 12

Preganglionic sympathetic axons entering sympathetic chains terminate in:

1. Paravertebral sympathetic chains: Both pre and postganglionic axons may run for some distance up or down the sympathetic chain before forming synapse/emerging.
2. Prevertebral ganglia/plexuses: In the abdominal cavity: 3 main: Coeliac ganglion, Superior mesenteric ganglion, hypogastric ganglion.
3. Adrenal medulla: Some preganglionic fibres emerging from 10th and 11th thoracic segments run in greater splanchnic nerve and terminate on chromaffin cells in the medulla of adrenal glands. Chromaffin cells analogous to sympathetic ganglia cells.