Regulation 5 Flashcards
How does the gut thins
- what does it sense
By chemoreceptors
—) senses changes in
- nutrient concentration
- nutrient degradation products
- osmotic pressure
- pH
And by mechanoreceptors
- sense stretch
What kind of cells are involved in sensing gut stretch (chemoreceptors)
What group of cells is it a part of (what kind of cells are they close to)
What are the black dots at the bottom of the cell
What exactly happens to these when they sense stretch (black dots)
Enteroendocrine cells
It is beside absorptive columnar epithelial cells
They are secretory granules that store hormones and release them when they sense stretch
They fuse with the basolateral membrane and allow hormones to enter the blood stream
Describe how endocrine hormones control GI function
Give examples of endocrine hormones (4)
What are the three kind of cells that release endocrine hormones (4)
- they have specificity by binding to a specific receptor (to a target receptor)
1. Gastrin
2. CCK (cholocystokinin)
3. Secretin
4. Motility
Cell Types
1. Paracrine: diffuse through extracellular space 2 target tissue
2. Autocrine: released substance regulates cells own function
3. Neurocrine: sensory cells secrete neurotransmitter
4. Endocrine: hormones enter blood and bind to target tissue
How does somatostatin act as and acid secretion inhibitor
In a paracrine fashion
What are two regulatory hormones that are only found in the small intestine
- CCK
- Secretin
What activates CCK
what activates secretin
CCK: amino acids and fatty acids
Secretin: activated by acid
What does secretin act on?
What does this do?
It acts on the pancreas
Specifically the duct cells of the pancreas to neutralize acid
They release bicarbonate
What is the downstream response to fatty acids and amino acids entering into the small intestine
- CCK is activated
- Digestive enzymes are released (for amino acids)
- Gull bladder is activated and Acinar cells release bile salts
What regulatory molecule reduces emptying of the stomach and relaxation of the sphincter of odi
CCK
Where is the sphincter of odi located
By the duodenum and is where the pancreas and the bile duct connect to the duodenum
What 4 things does CCK target in the small intestine, what does it do to them??
- Stomach —) causes reduction of emptying
- Pancreas —) targets Acinar cells to produce digestive enzymes
- Sphincter of odi —) relaxes (closes)
- Gall bladder —) release of bile salts
What are incretins what do they do
Give 2 examples
They are hormones that stimulate insulin production
GIP and GLP-1
What are two ways that we preform the glucose tolerance test
What are the results of the two tests
- Consumption of glucose —) production of incretins
- Injection into small intestine —) NO production of incretins
Why are second messengers sometimes used in endocrine hormones transport
Hydrophilic hormones can’t cross lipid by layer —) when needs to pass lipid by layer it uses a second messenger that activate transmembrane proteins
give two examples of secondary messengers that were discussed in class
Cyclic AMP
IP3
What kind of response do you get with Hydrophilic vs hydrophobic hormones
Rapid: hydrophilic —) already produced and degrade quickly
Slower: hydrophobic —) need to be made on demand
How are hydrophobic hormones released (what is their transport mechanism)
Diffusion
What are the steps or the important notes in hydrophobic hormones signalling
- They are synthesized on demand
- They are released by diffusion
- They attach to intracellular receptors (a hormone receptor complex)
- They bind to a target gene
- The gene is transcribed
- This causes a biological effect
Why can’t the body only use hydrophobic hormones to respond to changes in the body
It would take too long (responses would be too slow)
Do hydrophobic hormones have specific carrier proteins in the body
Yes
What is GLP-1 produced by
Why is it special (what other hormone is similar to this)
What does GLP-1 do
What drugs use GLP-1
What is the enzyme that degrades GLP-1
It is produced by L-cells
It is an intercrine hormone (enhances insulin production)
—) inhibits gastric emptying and motility, decrease glucose levels and decrease glucagon secretion
Ozempic —) for diabetes and obesity
DPP-4
What are the effects of GLP-1 on insulin and other things (6)
- Decreases motility and inhibits gastric emptying
- Decreases glucose levels
- Decreases glucagon secretion
- Increases insulin secretion
- Causes B-cells to expand
- Increases glucose disposal
What is GLP-2
What makes it different from GLP-1, what makes it similar
What does it do
It is a hormone
It is spliced differently but it comes from the same DNA
It is important in gut replacement
- decreases motility
- decreases apoptosis (cell death)
- decreases permeability
- increases proliferation (grows gut)
What is the name of the hunger hormone
Where does it signal (go)
What inhibits it
When is it released
Ghrelin
Signals the hypothalamus
Stretch in the stomach (fullness)
Released when stomach is empty
Is secretin hydrophobic or hydrophilic
Why
It is hydrophilic
Because it creates a fast response and it can be stored in vessicles
What does CCK go to
What does this cause
It stimulates the gull bladder —) Acinar cells secrete digestive enzymes and bladder secretes bile
How does the liver regulate satiety
It has nutrient receptors in the liver which monitor blood glucose levels
What acts on the vagal afferents (nerves) to regulate hunger
PYY
Stretch (nerves or receptors)
CCK
What are the affects of leptin
- Increases blood pressure
- Increases thermogenesis (heat)
- Increases beta oxidation
- Inhibits fat synthesis
What secretes leptin
Adipose tissue
What does a less functional leptin gene cause
It causes animals to deposit more adipose tissue
Where does NPY come from
What is it similar to
The GI tract
PYY
What does AGRP do in Rodents
What is it related to
Affects coat pigmentation
It is an agouti-related protein
What specific things can lead to obesity in animals
- We can become leptin resistant (we produce too much leptin) our body doesn’t respond to it as efficiently
- There can be in-utero effects which change the accurate nucleus in the brain which changes how it responds to POMC
- Dopeamine can change how our body responds (orexogenic responses)
- Mutations in POMC (messes with satiety signals)
