Physiology Flashcards by Cathy Wang

Where does carbohydrate digestion start

Mouth

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What are the 3 salivary glands

Parotid
Sublingual
Submandibular

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Which salivary gland secretes the least amount of saliva

Parotid

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Which salivary gland secretes the most amount of saliva

Submandibular

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Which salivary gland secretes the most viscous saliva

Sublingual

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What other enzyme does the mouth produce

Lingual lipase

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Where is the draining of parotid gland located at

upper 2nd molar teeth

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List the layers of GI mucosa from outermost to innermost

Serosa
Muscularis externa 
submucosa
muscularis mucosae
lamina propria
epithelium

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What does muscularis externa consist of

Circular and longitudinal smooth muscles

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Which muscle is next to serosa (outermost muscle)

Longitudinal muscle

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What is between the circular and longitudinal muscle layers

Myenteric plexus

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What is between the submucosa and circular muscle layers

Submucosal plexus

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What does lamina propria contain

Capillaries
Enteric neurones
gut associated lymphoid tissue

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What is right underneath the epithelium

Lamina propria

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What does submucosa contain

Connective tissue
glands
large blood and lymph vessels

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What nervous systems control the GI tract

Enteric nervous system

Parasympathetic and sympathetic nervous systems

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Which nervous system is most important at regulating GI tract

Parasympathetic nervous system

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Which nerves are included in parasympathetic NS for GI tract

Vagus nerves

Pelvic nerves

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What are the effects of sympathetic stimuli

Decreases motility, secretion and blood flow

Causes contraction of sphincters

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What are the effects of parasympathetic stimuli

Increases motility

Increases gastric, duodenal, pancreatic secretion

Relaxes sphincters

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What are the abdominal prevertebral ganglia that innervates the abdominal, pelvic and perineal organs

Coeliac
superior mesenteric
Inferior mesenteric

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What are the neurones of enteric nervous system

sensory
Interneurones
effector

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What is the function of interneurones

alter activity of effector neurone

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What is special about enteric nervous system and what affects the ENS

Can operate by itself but it is heavily affected by hormones and extrinsic nerves (parasympathetic / sympathetic )

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What is the function of muscularis mucosae

Contraction changes the absorptive and secretory area of mucosa

What feature allows smooth muscle in GI tract to depolarise at the same time

Gap junctions

What neurotransmitters do excitatory neurones release

ACh and substance P

What neurotransmitters do inhibitory nervous system release

NO and VIP

What are the pacemaker cells in GI tract called

Interstitial cells of cajal (ICC)

Function of ICC

Continuously generate slow wave of depolarisation to control motility

Do all slow waves cause smooth muscle contraction?

No, because not all slow waves reach threshold

What does the strength of contraction depend on

how long the membrane potential has stayed above threshold

What affects the threshold for contraction

Neuronal, hormonal and mechanical stimuli

How do neuronal, hormonal and mechanical stimuli affect slow waves

Shifts the membrane potential in a depolarising manner, allowing each cell to have different starting MP

Where is the enteric nervous tissue located at

myenteric and submucosae plexus

Describe peristalsis

Rhythmic contractions ; the smooth muscle in front of food bolus relaxes while the smooth muscle behind contracts

Function of gastrin

Stimulate gastric acid secretion Stimulate pepsinogen and IF secretion Inhibit migrating motor complex

What triggers the release of gastrin

Distension of stomach

What inhibits the release of gastrin

Low pH | Somatostatin

Function of Secretin

Increase pancreatic and biliary bicarbonate secretion | Decreases gastric acid secretion

What stimulates the release of secretin

In response to presence of fatty acids and H+ in intestinal lumen

Which cells secrete gastrin

G cells in stomach

Which cells secrete secretin

S cells in duodenum

Function of CCK

Inhibit gastric emptying Stimulate release of pancreatic enzyme Stimulate relaxation of sphincter of oddi and contraction of gall bladder to release bile Potentiates action of secretin

What triggers the release of CCK

Monoglycerides, fatty acids, amino acids in intestinal lumen

Which hormone induces satiety

CCK

Resistance in which hormone causes obesity

Leptin

How does leptin resistance cause obesity

It reduces satiety and causes overconsumption of food

Function of GIP

Stimulates the release of insulin | Inhibits gastric emptying

Which cell secretes CCK

I cell in duodenum

Which cell secretes GIP

K cells in duodenum and jejunum

Function of somatostatin

Inhibit gastric acid secretion by binding to receptor on parietal cells hence inhibiting adenylyl cyclase Inhibits CCK and secretin

Which cell produces somatostatin

D cells in pyloric gland area (stomach)

Where is pyloric gland area

Antrum

Where are G cells located

Pyloric gland

Function of enterochromaffin cells

Release histamine

How does histamine stimulate production of gastric acid

1) histamine binds to H2 receptors on parietal cells 2) activates adenylyl cyclase: ATP converted to cAMP 3) PKA activated by cAMP 4) proton pump on parietal cells are stimulated

Which cell produces gastroferrin and what other hormones does this cell produce

Parietal cell; also secretes intrinsic factors and HCL

Function of gastroferrin

Allows Fe2+ to bind hence allow absorption

Function of intrinsic factors

Bind to vitamin B12, allowing absorption

Signs of vitamin B12 deficiency

Macrolytic Pernicuous anaemia Paraesthesia

What activates pepsinogen

HCL, causing pepsinogen -> pepsin

How does the activation of pepsinogen amplifies itself

Pepsinogen activated by HCL -> pepsin | Pepsin activates more pepsinogen

Which cell produces pepsinogen and gastric lipase

Chief cells

Function of GLP-1

Stimulate release of insulin Decreases appetite Decrease glucagon secretion

What stimulates the release of GLP-1

glucose and fats

Which cell releases GLP-1

L cells in distal ileum

Function of motilin

Stimulates migrating motor complex

What stimulates the release of motilin

when duodenum and jejunum are empty

Which cells produce motilin

M cells in duodenum and jejunum

What is migrating motor complex

Strong peristaltic contraction to expel small intestine debris / undigested remains through ileocaecal valve to the caceum

What triggers the migrating motor complex

Motilin

Why does Migrating motor complex only occur between meals

To avoid losing nutrients

Describe the mucosa of small intestine

Simple columnar epithelium with microvilli Villi With crypts of lieuberkuhn between villi

What cells are at the bottom of crypts of lieuberkuhn

Paneth cells

What cells are at the upper portion of crypts of lieuberkuhn

Stem cells

Function of paneth cells

Produce substances that attack bacteria

Which enzyme activates trypsinogen

Enterokinase in duodenal mucosa

What is in submucosal layer of duodenum

Brunner's glands

Function of Brunner's glands

Release alkaline mucous to neutralize the chyme

When is somatostatin released

After meal when pH is low

What are the 3 phases of gastric acid secretion

Cephalic Gastric Intestinal

What stimulates cephalic phase

smell, sight, chewing, swallowing

What does somatostatin inhibit

CCK and secretin