7. The Automatic Nervous System

Question 1

What are the 3 divisions of the automatic nervous system?

Answer 1

Sympathetic nervous system
Parasympathetic nervous system
Enteric nervous system

Question 2

What are the functions of the ANS?

Answer 2

Motor system providing control over visceral functions essential to homeostasis
Coordinated cardiovascular resp, digestive, urinary and reproductive functions
Some metabolic functions
Visceral sensory fibres
ANS controls visceral reflexes

Question 3

What does the ANS extrinsically regulate?

Answer 3

Cardiac muscle
Smooth muscle
Glandular secretions

Question 4

What is a ganglion?

Answer 4

A congregation of synapses

Question 5

What is the anatomy of the neurones?

Answer 5

Preganglionic neurones have cell bodies within the CNS that send axons to peripheral ganglia and they synapse to postganglionic neurones where the cells then innervate various target organs

Question 6

Where are the preganglionic neurones of the sympathetic neurones found?

Answer 6

Found between T1 and L2 of spinal cord

Question 7

Where are the postganglionic sympathetic neurones found?

Answer 7

Sympathetic chain ganglia
Collateral ganglia
Adrenal medulla

Question 8

What are the features of the neuroeffector junction?

Answer 8

Postsynaptic nerve terminals different from neuromusuclar junction

No synaptic knobs

Terminal portions branch and form network over surface & may penetrate outer layer

Each branch may have many varicosities

Chains of varicosities pass near to tissue surface

No specialized postsynaptic surface membranes

Receptors all over tissue surface - intra-junctional and extra junctional receptors

Question 9

What are the general functions of PNS?

Answer 9

Pupillary constriction & eye near-focusing
↑’s secretion form digestive glands (salivary, gastric, duodenal & intestinal glands, pancreas & liver)
↑’s smooth muscle activity in GI tract
↑’s secretion of hormones that promote absorption & utilization of nutrients in peripheral tissues (eg. insulin)
Participates in defecation
Constricts bronchioles
↓’s heart rate & myocardial contractility
participates in sexual arousal & stimulation of sexual gland secretions in both genders

Question 10

What are the two major receptor subtypes?

Answer 10

Nicotinic receptors and muscarinic receptors

Question 11

What is meant by the term autonomic tone?

Answer 11

Describes resting spontaneous level of activity in autonomic nerves in absence of stimuli

Question 12

What is the relationship between blood vessels and sympathetic activity?

Answer 12

constrict with ↑’d sympathetic activity

dilate with ↓’d sympathetic activity

Question 13

What is the enteric nervous system?

Answer 13

The nervous system to control the GI tract

Question 14

Where is the enteric nervous system located?

Answer 14

Oesophagus to anus

Question 15

What are the two plexuses of the enteric nervous system?

Answer 15

Myenteric plexus between circular and longitudinal

Mainly controls GI movements

Question 16

What are the two plexuses of the enteric nervous system?

Answer 16

Myenteric plexus between circular and longitudinal
Mainly controls GI movements
Submucosal plexus in submucosa
-mainly controls mucosal secretion and local blood flow

Question 17

What nerves provide extrinsic innervation?

Answer 17

Sympathetic nerves

Parasympathetic nerves

Question 18

What do the sympathetic nerves do?

Answer 18

Slows down contractions, secretions and blood flow

Question 19

What do the parasympathetic nerves do?

Answer 19

Speeds things up

Question 20

Where do sensory nerves from the gut and and walls travel to?

Answer 20

Collateral ganglia
Spinal cord
Brain via vagus

Question 21

What does extrinsic innervation allow?

Answer 21

GI tract to function independently, modified by CNS and allows fine reflex control

Question 22

What is the fight or flight response and what mediates it?

Answer 22

A coordinated response involving parasympathetic nerves, sympathetic nerves and adrenal medullae
Hypothalmus

Question 23

What happens during the fight/flight response?

Answer 23

↑’d heart rate and contractility
↑’d vasoconstriction in skin, gut, kidney, etc
↑’d BP
↓’d vasoconstriction & ↑’d rate & depth of breathing
relaxed accommodation & pupil dilation
↑’d mental alertness (reticular formation threshold lowered)
↓’d sensitivity to pain
↑’d plasma & FFA concentrations
↑’muscle glycolysis

Question 24

What do baroreceptors do?

Answer 24

Act as short-term buffers to BP fluctuations

Question 25

What does an acute rise in BP cause?

Answer 25

Increased receptor discharge

Question 26

What does an acute rise in BP cause?

Answer 26

Increased receptor discharge
Polysynaptic pathways will alter autonomic outflow
Decreased sympathetic activity to arterial blood vessels and decreased TPR
Decreased sympathetic activity to venous blood vessels Decreased venous return to heart and cardiac output

Question 27

What is the response to a sharp BP fall?

Answer 27

A decreased receptor discharge results in
increased sympathetic activity to heart

decreased parasympathetic activity to heart

increased HR

Increasedd myocardial contractility

increased sympathetic vasoconstriction

Increased sympathetic venoconstriction