Endocrine System: Glucose Homeostasis

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  • Created by: Bhickling
  • Created on: 19-04-21 12:18
What are endocrine glands?
A collection of glands that secrete hormones directly into the circulatory system to be carried to a target cell
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Describe the anatomy of the pancreas
- 2 lobes: left + right
- Right lobe = within meso-duodenum
- Left lobe = within deep leaf of greater omentum
- Endocrine + exocrine gland
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Describe the exocrine cells of the pancreas
- Most exocrine cells are arranged in clusters called acini
- produce digestive enzymes that flow through a duct directly into the GI tract
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Describe the endocrine cells of the pancreas
- clusters of endocrine tissue = islets of Langerhans
- 4 cell types: alpha, beta, delta, F cells
- Alpha = secrete glucagon
- Beta = secrete insulin
- Delta = secrete somatostatin
- F cells = secretes pancreatic polypeptide
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Describe insulin
- Beta cells produce a pro-hormone called proinsulin
- converted to active insulin by removal of inactive peptide (water soluble polypeptide)
- short half-life (5-8 mins)
- binds to a specific tyrosine kinase membrane receptor
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What is the primary driver for insulin secretion?
Blood glucose
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How does glucose move in and out of cells?
Via GLUT transporters as not lipid-soluble
- insulin increases the expression of GLUT4 transporters
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Describe the process of insulin secretion due to an increase in blood glucose detected by beta cells of the pancreas
- glucose enters the beta cells via GLUT2 transporters
- increased glucose = more ATP
- Increase in ATP blocks the ATP-sensitive K channels in beta cells- K+ accumulates in cytoplasm= depolarisation of cell membrane
- voltage gated Ca channels open
- Ca f
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Do mechanisms other than blood glucose control insulin secretion?
Yes:
- GI hormones (GIP, GLP-I)- anticipatory insulin secretion to prevent sudden surge of glucose absorption after meal)
- Parasympathetic control (rest + digest- increases insulin)
- Sympathetic control (fight + flight- decreases insulin)
- Increased am
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Do all cells require insulin for uptake of glucose into cells?
No- it is independent of insulin in:
- brain (GLUT3)
- mammary glands, GI tract, kidney tubules (secondary active- Na co-transport)
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How does skeletal muscle, adipocytes + other cells respond to insulin?
- increase uptake of glucose by expression of GLUT4 transporters in cell membrane
- glucose converted to glucose-6-phosphate, glycogen or fat
- no transporters = no glucose uptake
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How does response to insulin differ in the liver?
- expression of GLUT2 transporters that allow glucose to move in both directions
- fasted state = hepatocytes make glucose + transport out of cell into bloodstream via GLUT2 transporters
- fed state = glucose enters hepatocytes via GLUT2 transporters, ins
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How does the CNS respond to insulin?
- neurones are not sensitive to insulin
- metabolism of CNS neurones relies 100% on glucose (steady state of glucose transport into cells- cannot increase/ decrease rate of transporters)
- level of glucose in CSF directly proportional to blood glucose
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What does insulin do?
- increase glycogenesis
- increase lipogenesis
- increase glucose oxidation
- increase protein synthesis
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Describe glucagon action
- secreted by alpha cells of the pancreas
- water-soluble polypeptide
- short half life (4-6 mins)
- binds to specific G protein- coupled membrane receptor
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What factors control the release of glucagon?
- increase amino acids after meal
- hypoglycaemia
- parasympathetic control
- sympathetic control
ALL stimulate secretion of glucagon
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Why does an increase in amino acid concentration stimulate secretion of both insulin + glucagon?
protective mechanism to protect carnivores from hypoglycaemia following consumption of a high protein, low carbohydrate meal
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What does glucagon do?
- increase gluconeogenesis
- increase glycogenolysis
- increase ketogenesis
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What does somatostatin hormone do?
- decreases secretion of growth hormone
- paracrine inhibition of insulin + glucagon secretion
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Compare Type 1 and Type 2 diabetes in cats and dogs
Type 1 = insufficient insulin secretion, more common in dogs then cats
Type 2 = abnormal target cell responsiveness, more common in cats then dogs
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What are the main clinical signs of diabetes mellitus in domestic species?
- hyperglycaemia
- polyuria + polydipsia
- ketoacidosis
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Other cards in this set

Card 2

Front

Describe the anatomy of the pancreas

Back

- 2 lobes: left + right
- Right lobe = within meso-duodenum
- Left lobe = within deep leaf of greater omentum
- Endocrine + exocrine gland

Card 3

Front

Describe the exocrine cells of the pancreas

Back

Preview of the front of card 3

Card 4

Front

Describe the endocrine cells of the pancreas

Back

Preview of the front of card 4

Card 5

Front

Describe insulin

Back

Preview of the front of card 5
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