5.4.3 - 5.4.4

Question 1

exocrine glands

Answer 1

secrete substances into a duct

Question 2

exocine cells arrangement

Answer 2

in small groups called ACINI (acinus), surrounding a tubule at the centre

Question 3

role of acinus cell

Answer 3

• synthesise enzymes
• secrete into the tubule at the centre of the group

Question 4

tubules in the acini

Answer 4

• join to form INTRALOBULAR ducts that combine to form pancreatic duct

Question 5

role of pancreatic duct

Answer 5

• carries the fluid containing the enzymes into the first part of the small intestine (duodenum)
• SECRETES the fluid into the duodenum

Question 6

what is in the fluid from the pancreatic duct

Answer 6

1. pancreatic amylase (amylose to maltose)
2. trypsinogen (inactive protease that is converted to active trypsin when it enters duodenum)
3. lipase (digests lipids)
4. sodium hydrogencarbonate to neutralise the system coming from acidic stomach

Question 7

which are the endocrine glands

Answer 7

islets of langerhans

Question 8

describe arrangement of islets of langerhans

Answer 8

• alpha cells
• beta cells

Question 9

how to recognise alpha and beta cells

Answer 9

• alpha light stain
• beta dark stain

Question 10

alpha cells purpose

Answer 10

secrete glucagon

Question 11

beta cells purpose

Answer 11

secrete insulin

Question 12

how is insuliin released from beta cells

Answer 12

1. potassium ion channels in CSM usually open (and ca2+ closed), so k+ flow out of cell
2. when blood glucose conc high, glucose diffuses into cell
3. glucose metabolised to produce ATP
4. ATP closes k+ ion channel
5. accumulation of k+ inside cell alters PD; inside cell is less negative
6. change in PD opens Ca2+ chanells, so calcium ENTERS the cell
7. ca2+ cause the vesicles of insulin to fuse with the CSM, releasing insulin by exocytosis

Question 13

normal conc. blood glucose

Answer 13

4-6 mmol / dm3

Question 14

hypoglycaemia

Answer 14

low blood sugar

Question 15

hyperglycaemia

Answer 15

high blood sugar

Question 16

probelms associated with hypoglycaemia

Answer 16

• glucose too low
• tiredness
• irritiability

Question 17

what happens if blood glucose is too high (not full thing)

Answer 17

• beta cells secrete insulin
• travel in blolod to target cells (liver, muscle)

Question 18

insulin is a … (hormone)

Answer 18

peptide based hormone
so cant diffuse across cell surface membrane

Question 19

describe how insulin enters cells

Answer 19

• insulin binds to sepcific completmentary insulin receptor on CSM of target (muscle/liver) cells
• activates enzyme tyrosine kinase
• causes phosphorylation of inactive enzymes in the cell, activating them
• cascade of enzymes
• vesicles containing glucose transproter protein inserted into CSM
• extra glucose can now enter cell for 1. glycogenesis 2. respiration 3. conversion to fats

Question 20

what happens if blood glucose too low

Answer 20

• alpha cells secrete glucagon into the blood
• GLUCAGON ONLY ACTS ON HEPATOCYTES
• Binds to specific comp receptors in hepatocytes
• stimulates a g protein , which activates adenyl cyclase, which catalyses ATP-> cAMP, which actives a series of enzyme contrilled reactions
• 1. glycogenolysis (glycogen to glucose) 2. more fatty acids used in respiration (instead of glucose) 3. gluconeogenesis

Question 21

gluconeogenesis

Answer 21

formation of NEW glucose
- from amino acids and fats

Question 22

what mechanism controls the blood glucose

Answer 22

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