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Hormone Cheat Sheet by

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Definition

A hormone is a chemical substa­nce produced by endo­crine glands and secreted directly into the blood to be transp­orted to specific target organs where it exerts its effects, after which it is dest­royed by the liver.

Differ­ences between endocrine & nervous

Endocrine
Nervous
Involves hormones
Involves impulses
Transp­orted in blood
Transp­orted by neurones
Usually slow
Usually quick
Involu­ntary
Either voluntary or involu­ntary
Short-­lived or long-lived
Short-­lived
May affect more than one organ
Usually localised

Adrenaline

Stimulus: fear, anger, anxiety received by the hypoth­alamus
Secreted by adrenal medulla in the adrenal gland
Actions
Effects
Stimulates breakdown of glycogen to glucose in the liver
Increases blood glucose level
Increases heart rate and blood pressure
Transport oxygen and glucose to the muscles faster
Increases rate and depth of ventil­ation
Increases oxygen supply to the muscles
Dilates pupils of eye
Enhanced vision
Constricts arterioles in the skin and digestive system
Channel more blood to the skeletal muscles
Speeds up blood clotting
Reduces blood loss
 

Insulin

Stimulus: blood glucose concen­tration increases above normal levels
Secreted by Islets of Langerhans in the pancreas
Actions
Effects
Increases permea­bility of cell membranes to glucose
Increases glucose uptake
Stimulates conversion of excess glucose into glycogen in liver and muscles
Decreases blood glucose concen­tration

Glucagon

Secreted when blood glucose concen­tration decreases below normal levels
Secreted by Islets of Langerhans in the pancreas
Actions
Effects
Stimulates the conversion of glycogen, fats and amino acids into glucose in the liver
Increases blood glucose concen­tration

Effects of insulin on body

Lack of secretion:
Hype­rgl­yce­mia
Glucose cannot be stored and therefore lost in urine, causing diabetes mellit­us.
Muscles have no glycogen reserve, causing the person to feel weak and eventually lose weight.
Body oxidises fats instead of glucose for energy, causing pois­onous substance ketones to be produced, which at high concen­tra­tions can cause blood pH to drop.

Over-s­ecr­etion:
Hypo­gly­cemia
Results in insulin shock, leading to coma and possibly death.
 

Diabetes Mellitus

Type 1
Islets of Langerhans do not secrete sufficient insulin
Type 2
Cells of target organs are insens­itive to insulin
Signs and symptoms
1. Presence of glucose in urine after meals
2. Persis­tently high blood glucose conc.
3. Slow healing of wounds as bacteria growth is encouraged with high blood glucose, causing inflam­mation of wounds
4. Increased urinat­ion­/thirst
5. Rapid weight loss as there is low glycogen storage
6. Blurred vision leading to blindness
4: High blood glucose conc. causes a decrease in water potential. Water moves from surrou­nding tissue fluid into the blood, indicating that more water will enter the nephron during ultraf­ilt­ration, therefore causing increased volume of urine to be produced. There is thus loss of excessive amount of water, causing feelings of thirst

Treatments for diabetes

Inject insulin directly into blood
Ensure patients have a supply of sugary food as too much insulin can cause blood glucose to drop too low, leading to coma
Regulate carboh­ydrate content in diets, regular exercise

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