Lecture 13: Autonomic nervous system 1

Question 1

What is the ANS critical for?

Answer 1

controlling bodily functions, including regulation of all organs and most tissues

Question 2

What is homeostasis?

Answer 2

maintaining internal set points critical for survival: i.e., keeps us alive

Question 3

What is allostasis?

Answer 3

maintaining homeostasis through adaptive change of the internal environment, to meet perceived and anticipated demands, e.g., acute stress, exercise

Question 4

What are the cellular targets of autonomic nerves?

Answer 4

smooth and cardiac muscle
epithelial transport of ions
hormone and mucous secretion
metabolism
immune system

Question 5

Some tissues are supplied by autonomic nerves, but…

Answer 5

no function has been identified for these nerves yet

Question 6

What can actions of the nervous system be part of?

Answer 6

simple reflexes or involve coordinated regulation of multiple sites or be associated with a more complex behavior (e.g., stress, anxiety, pain)

Question 7

What do the sympathetic and parasympathetic components of the ANS comprise?

Answer 7

neurons of the central nervous system (CNS) and the peripheral nervous system (PNS): they cannot function without the CNS

Question 8

Where are neuronal cell bodies of the ENS contained and how can they function?

Answer 8

neuronal cell bodies are entirely within the gastrointestinal tract: can function independently of CNS

Question 9

What does the ENS comprise?

Answer 9

complete reflex circuits, i.e., the ENS has its own sensory, motor and interneurons

Question 10

What can some classes of neurons in the ENS be influenced by?

Answer 10

the sympathetic and/or parasympathetic systems

Question 11

What are sympathetic and parasympathetic nervous systems defined by?

Answer 11

their anatomy, specifically the location of their preganglionic neurons

Question 12

What is the sympathetic NS described as?

Answer 12

thoraco-lumbar

Question 13

What is the parasympathetic NS described as?

Answer 13

cranio-sacral

Question 14

Where are sympathetic ganglia located?

Answer 14

generally closer to CNS

Question 15

Where are parasympathetic ganglia located?

Answer 15

generally closer to or within organs

Question 16

What is the primary NT of neurotransmission in the ganglia?

Answer 16

acetylcholine

Question 17

Which NTs are released by sympathetic ganglia and which receptors do they bind to?

Answer 17

noradrenaline

alpha or beta adrenoceptors

Question 18

Which NTs are released by parasympathetic ganglia and which receptors do they bind to?

Answer 18

acetylcholine

nicotinic or muscarinic receptors

Question 19

What is co-transmission?

Answer 19

when more than one transmitter is released from a synapse

Question 20

There are many ___ of ACh and NA receptors.

Answer 20

subtypes

Question 21

What are transcriptome analyses identifying?

Answer 21

new subclasses of autonomic ganglion neurons and preganglionic neurons

Question 22

What is the structure of the sympathetic nervous system?

Answer 22

preganglionic neurons in thoraco-lumbar cord

axons project via spinal nerves

Question 23

What are the two types of sympathetic ganglia?

Answer 23

paravertebral ganglia (sympathetic chain) and prevertebral ganglia (mesenteric ganglia)

Question 24

What do sympathetic preganglionic neurons innervate?

Answer 24

the adrenal medulla

Question 25

What happens if adrenal cells are activated?

Answer 25

adrenal cells secrete the hormones, adrenaline and noradrenaline, into the circulation, having widespread effects

Question 26

What is “fight-or-flight”? What is the purpose of this response?

Answer 26

mass activation of many sympathetic pathways at once to overcome or escape from a major threat

Question 27

How does the body change during a “fight-or-flight” response?

Answer 27

increased heart rate, increased contractile force of heart, increased blood flow to skeletal muscle, decreased blood flow to gut, decreased gut motility (can modulate enteric system)

Question 28

How is mass activation and coordination achieved?

Answer 28

catecholamine hormones can spread through the bloodstream
the CNS activates many preganglionic pathways simultaneously
some preganglionic neurons have many axon collaterals so can activate many postganglionic pathways simultaneously

Question 29

What is mass activation relevant to in comparison to the SNS?

Answer 29

mass activation is relevant to a more unusual situation, whereas the sympathetic nervous system is essential for normal living (e.g. adjustments of blood pressure, small temperature changes)

Question 30

Where are preganglionic neurons of the parasympathetic nervous system located?

Answer 30

located in the Edinger-Westphal nucleus, the salivatory nuclei and dorsal motor nucleus of vagus and nucleus ambiguus

Question 31

Where do preganglionic neurons in the Edinger-Westphal nucleus run to and control?

Answer 31

run to ciliary ganglion to control sphincter pupillae, ciliary muscle

Question 32

Where do preganglionic neurons in the salivatory nuclei run to and control?

Answer 32

to submandibular, spheno-palatine and otic ganglia to control lacrimal, salivary, sublingual, nasal and palatine glands

Question 33

Where do preganglionic neurons in the dorsal motor nucleus of vagus and nucleus ambiguus run to and control?

Answer 33

to unnamed microganglia near and on outer surface of thoracic and abdominal organs: numerous functions

Question 34

Where do sacral postganglionic neurons lie? What do pelvic ganglia contain?

Answer 34

in the pelvic plexus

contain many sympathetic neurons i.e. these are mixed ganglia = very unusual

Question 35

Why are sacral postganglionic neurons vulnerable to surgical injury?

Answer 35

many of these ganglion neurons have unusually long axons

Question 36

What is the role of parasympathetic nerves?

Answer 36

inducing “rest-and-digest” which involves decreased heart rate, decreased contractile force of heart and increased gut motility

Question 37

Is there mass activation of parasympathetic pathways? Why or why not?

Answer 37

no, because there is no equivalent of adrenal gland i.e. no release of ACh into the bloodstream to affect all organs at once

Question 38

How does most coordination of parasympathetic pathways between different regions occur?

Answer 38

by brain mechanisms

Question 39

What are the limitations of the “rest-and-digest” model?

Answer 39

parasympathetic pathways can be activated under many situations, not just rest/digest
underestimates diversity of parasympathetic
function
assumes a rather extreme situation when nothing much is happening

Question 40

Are sympathetic and parasympathetic systems antagonistic?

Answer 40

sometimes: there are very few cases where the two systems are genuinely antagonistic at the cellular level

Question 41

How does the SNS act in relation to the PNS?

Answer 41

actions on different tissues cause different types of actions (not necessarily opposite)

Question 42

What are examples of different but not opposite actions?

Answer 42

sympathetic: serous salivary secretion, sweat secretion, lipolysis
parasympathetic: mucous salivary secretion, tear secretion

Question 43

What are examples of function antagonism in tissue/organ but via different cells?

Answer 43

sympathetic: contract pupil dilator muscle, contract neck of bladder (continence)
parasympathetic: contract pupil sphincter muscle, contract body of bladder (voiding)

Question 44

What is an example of genuinely antagonistic actions at the cellular level?

Answer 44

sympathetic: increase in heart rate
parasympathetic: decrease in heart rate