Hormonal Communication

Page 1

Endocrine glands: Releases hormones into blood to be transported to target organs

Exocrine glands: Releases hormones into ducts

Examples of glands:

Pituitary gland (in brain, below hypothalamus)

Adrenal gland (on top of kidneys)

Pancreas (above liver)

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The Pancreas

Exocrine gland when secretes enzymes and pancreatic juices into ducts that lead to small intestine

Endocrine gland when secreting glucagon and insulin (islets of langerhanns)

Beta cells secrete insulin

Alpha cells secrete glucagon

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Blood glucose regulation

Glycogenolysis: breaking down of glycogen into glucose

Gluconeogensis: making of glucose from non-carbohydrate molecules

glycogenesis: making of glycogen

Can also regulate glucose levels through diet, exercise and controlling respiration rate.

Beta Cells:

Detect rise in blood glucose levels

Secrete Insulin into blood

Insulin binds to receptors in most cells

It increases the rate of glycogenesis, increases the uptake of glucose, increases the rate that glucose is broken down into fatty acids etc and increases the rate of respiration.

Insulin is broken down by enzymes in the liver so must be constantly secreted to have an effect

Alpha cells:

Detect fall in glucose levels

Secrete Glucagon into the blood

Only binds to receptors in fat cells and the liver

Increases rate of Glycogenolysis and gluconeogenesis

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Insulin Secretion

Normally potassium ion channels in pancreas cells are open, potassium ions diffuse out of cells giving them a resting potential of -70mV

When glucose diffuses into the cells and is metabolised, ATP is released

ATP binds to potassium channels causing them to close

The cells then become depolarised to -30mV, causing calcium ion channels to open

Calcium ions cause vesicles containing the hormones to bind to the cell membrane and secrete the hormone into the blood.

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Diabetes

Type 1: Caused by beta cells being unable to produce insulin, from childhood

Type 2: Caused by not enough insulin being produced or by the cells not responding to insulin correctly. (linked to obesity)

Control:

regulating diet

regulating exercise

injecting insulin

pancreas implant

insulin pump

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Fight or flight response

Hypothalmus detects changes and activates sympathetic nervous system

Causes the adrenal medulla to secrete noradrenaline and adrenaline which causes a cascade of events, such as an increased breathing and heart rate

Also causes the release of ACTH which travels to the pituitary gland, causing the release of 30 other hormones which help prepare to cope with a threat.

Adrenaline

Adrenaline binds to receptor sites

causes the release of enzyme inside membrane which activates secondary messenger molecue cAMP

cAMP activates enzymes that catalyse glycogen breaking down into glucose.

Page 7

Controlling heart rate

Baroreceptors: detect changes in blood pressure in the aorta and other arteries, if pressure too low send messages to hypothalamus to increases rate of impulses in SAN

Chemoreceptors: detect changes in chemical balance of the blood in the aorta etc, if PH drops (due to less CO2) then send messages to the hypothalamus to increase heart rate.