the pancreas

5.1.4 d

where is the pancreas

behind stomach

what are the 2 functions of the pancreas

endocrine: secrete insulin and glucagon into blood

exocrine: secrete enzymes into small intestine

describe the exocrine function of the pancreas

acini group into small lobules and surround tubules which join into the pancreatic duct. enzymes are secreted into tubules

secrete as liquid containing amylase, trypsinogen, lipase and NaHCO3

what are the islet of langerhans

alpha and beta cells clumped together in small patches in the pancreas

what are the functions of alpha and beta cells

alpha produce glucagon, beta produce insulin

negative feedback loop pt 1: glucagon

low glucose conc > detected by alpha cells > secrete glucagon > glucagon detected by receptors on liver cells > liver cells convert glycogen into glucose (glycogenolysis) > glucose is hydrolysed and more glucose is released into blood, liver creates new glucose molecules from amino acids and lipid (gluconeogenesis)

negative feedback loop pt 2: insulin

high glucose conc > detected by beta cells > secrete insulin > insulin detected by receptors on liver cells > liver cells become permeable to glucose and enzymes convert glucose into glycogen (glycogenesis) > glucose is removed from the blood and stored as glycogen in liver and muscle cells

what is hypoglycaemia

blood glucose conc drops too low

what is hyperglycaemia

blood glucose is too high

control of insulin secretion: what is the conditions of a beta cell at normal glucose conc

potassium ion channels are open and have a voltage of -70 mV

control of insulin secretion: what happens when blood glucose conc increases

glucose enter cell by glucose transporter, used in respiration to produce ATP and binds to K+ channel

control of insulin secretion: effect of ATP

causes K+ ions to close, no K+ can diffuse out so depolarisation, voltage now at -30 mV

depolarisation causes Ca2+ channel to open causing vesicles to release insulin in exocytosis

action of insulin: what happens when it binds to receptors

activate tyrosine kinase which activates enzyme in cell, causing more glucose transporter proteins in the membrane so more glucose is absorbed by facilitated diffusion

what can high levels of glucose in the cell be used for

glycogen production (glycogenesis), respiration

action of glucagon: what happens when it binds to receptors

activate adenyl cyclase which then helps form cAMP from ATP

what does cAMP do to increase blood glucose concentration

hydrolyse glycogen into glucose (glycogenolysis), form new glucose molecules from amino acids and fats (glyconeogenesis)