Control 2

Question 1

What are rich plexuses?

Answer 1

dense local network of nerves and supporting cells

Question 2

what are ganglia?

Answer 2

nerve cells which carry signals

Question 3

What are ganglia in enteric nervous system interconnected by?

Answer 3

tracts of fine, unmyelinated nerve fibres.

Question 4

What is the enteric nervous system?

Answer 4

“second brain” capable of independence, consists of rich plexus of ganglia interconnected by unmyelinated fibres and integrates function

Question 5

What is an interesting feature of the enteric nervous system?

Answer 5

produce a coordinated response to specific stimuli independent of the central nervous system.

Question 6

What can cause dysfunction?

Answer 6

Inflammation (ulcerative colitis; Crohn’s disease)
Following invasive abdominal surgery
Irritable bowel syndrome
Ageing (constipation)

Question 7

What are the two main plexuses of the gut?

Answer 7

the myenteric plexus and the submucosal plexus.

Question 8

Where is the myenteric plexus located

Answer 8

between the circular and longitudinal smooth muscle layers, and has efferent innervation of both

Question 9

What does the myenteric plexus do?

Answer 9

allows for coordinated control of motor function, and hence, motility.

Question 10

What are the afferent functions of the submucosal plexus?

Answer 10

senses the environment within lumen using mechanoreceptors, chemoreceptors and osmoreceptors.

Question 11

What are the efferent functions of the submucosal plexus?

Answer 11

Can fine tune local blood flow, epithelial transport and secretory/paracrine/endocrine cell function.

Question 12

What are the functions of the entire enteric system?

Answer 12

SPAM
Secretion - controlling secretions of enzymes, paracrine signals, endocrine hormones to regulate local and non local gut functions
Perfusion - blood flow carfully controlled to ensure high perfusions
Absorption - of nutrients, vitamins, minerals and ions by adjusting expression of luminal transport proteins
Motility - smooth muscle cells in circular and longitudinal muscle layers can contract and relax to cause effective gut transit

Question 13

What do sensory neurones respond to?

Answer 13

Mechanical, thermal, osmotic and chemical stimuli

Question 14

What do motor neurones do?

Answer 14

Axons terminate on SMC of circular or longitudinal layers, secretatory cells of GI tract or GI blood vessels

Question 15

Interneurones dunction?

Answer 15

Neurones between neurones integrate the sensory input and effector output

Question 16

Where are SNS preganglionic cell bodies found?

Answer 16

located in the spinal cord in the lower thoracic and upper lumbar spinal cord

Question 17

Where are SNS postganglionic cell bodies found?

Answer 17

pre- and paravertebral ganglia

Question 18

Where are PNS preganglionic cell bodies found?

Answer 18

Brainstem and sacral spinal chord

Question 19

Where are PNS postganglionic cell bodies found?

Answer 19

V close to target organs

Question 20

Where are SNS pre-ganglionic nerves arising from and where do they innervate?

Answer 20

Pre-ganglionic neurons are in the splanchnic nerves arising from the thoracic and lumbar regions. Thoracic branches innervate the foregut and associated organs, and the lumbar branches innervate the hindgut.

Question 21

Where does most PNS GI tract inervation come from?

Answer 21

Most GI tract innervation in the branch of the ANS arises from the vagus nerve (CNX).

Question 22

What structures receive PNS innervation from pelvic splanchnic nerves?

Answer 22

Structures from the descending colon onwards receive innervation from the pelvic splanchnic nerves.

Question 23

What does the difference between blood supply and nervous innervation between structures before and after splenic flexure of large intestine reflect?

Answer 23

Embryological origins of the gut

Question 24

What is the major neurotransmitter of the SNS?

Answer 24

Norepinephrine

Question 25

What do synapses of the sympathetic chain of the SNS use to communicate - neurotransmitters?

Answer 25

acetylcholine (ACh), but most synapses between the SNS and the enteric nervous system use Norepinephrine

Question 26

What is the major neurotransmitter of PNS branch of the ANS

Answer 26

Acetylcholine

Question 27

What is the general impact of SNS on gut?

Answer 27

Reduce activity

Question 28

What is the general impact of PNS on gut

Answer 28

Increase activity

Question 29

How does the enteric nervous system interact with the autonomic nervous system

Answer 29

The ANS typically inputs into the enteric nervous system, allowing integration with local afferent signals to provide a coordinated response

Question 30

What is an exception of how the enteric nervous system interacts with ANS

Answer 30

Sympathetic innervation of vascular smooth muscle. This allows the ANS to rapidly shut down gut perfusion in high stress situations, allowing blood to be redirected to brain, heart and muscle (SURVIVAL response)

Question 31

What would a disruption in ANS innervation cause?

Answer 31

only a small decrease in functionality. The enteric nervous system is very INDEPENDENT!

Question 32

What do glial cells do

Answer 32

provide insulate, protective, nutritional and structural support