Endocrine System - Chp 35

What are the differences between the nervous and endocrine systems?

Nervous system

• fast-acting

• mostly electrical

• response duration is short

• location affected is localised

• eg catching a ball

Endocrine system

• slow-acting

• chemical

• response duration is long-lasting

• effect can be widespread

• eg growth

What are the 2 types of glands?

Exocrine glands - release their product into ducts eg sweat gland

Endocrine glands - ductless, release products directly into the bloodstream eg pituitary gland

What type of gland is the pancreas + why?

• both exocrine and endocrine

• exocrine because it produces digestive enzymes that enter the small intestine via the pancreatic duct

• endocrine because it produces insulin which is released straight into the blood

Hormone

a chemical messenger produced by an endocrine gland and carried by the bloodstream to another part of the body where it has a specific effect

What are hormones made from?

mainly protein but some are steroid based

Draw a diagram of the main endocrine glands

The pituitary - function

produces hormones that control all glands in the body (TSH thyroid stimulating hormone)

eg GH - growth hormone

• overproduction causes gigantism

• underproduction cases dwarfism

Hypothalamus - function

links the nervous and endocrine systems, control the pituitary gland in response to messages from the brain and other hormones

What are the 2 types of hormones?

Releasing - cause the production of hormones

Inhibiting - stop the production of hormones

Pineal gland - function

produces many hormones such as melatonin, which is involved in sleep, ovulation and activity patterns

Thyroid - function

produces the hormone thryoxine, which controls the rate of a person’s metabolism

Thyroxine deficiency - symptoms + treatment

• cretinism - thyroxine underproduction in children causing stunted growth

• goitre - thyroxine underproduction in adults causing tiredness, lack of energy, weight gain

  • goitre is an enlargement of the thyroid gland + is usually caused by a lack of Iodine in the diet

• goitre can be treated by increasing Iodine in the diet

Thyroxine excess - symptoms + treatment

• graves’ disease - metabolic rate increases causing weight loss, heat production, nervousness, anxiety and bulging eyes

• cured by removing part of the thyroid or killing part of the gland with radioactive iodine

Parathyroids - location + function

• 4 glands are embedded in the thyroid gland

• make parathormone which stimulates the release of calcium from the bones into the blood plasma

Thymus - function

• produces thymosin, causing white blood cells to mature + become active

• thymus breaks down at puberty and stops working in middle age

Adrenals - function

• produces adrenaline

Effects of adrenaline

• increases blood flow to heart, muscles and brain

• reduces blood flow to skin, causing paleness

• opens bronchioles allowing more oxygen to lungs

• increases heart rate

• muscular contractions increase in strength

• increases mental alertness

What does the pancreas contain which produces insulin?

a million groups of cells called the islets of Langerhans

Give 2 examples of hormonal support:

• insulin to treat diabetes

• anabolic steroids

Diabetes - meaning, symptoms + treatment

• low insulin production or inability of cells to take up insulin

• symptoms include - high glucose conc in blood and urine, large amounts of urine, loss of weight, tiredness

• controlled by regular injections

What are anabolic steroids and what effect do they have?

• drugs, similar to testosterone, that build up muscle

• increase muscle size, strength and speed up recovery

• damage the liver and adrenal gland

How are thyroxine levels controlled in the body?

Negative feedback loop

• if thyroxine levels are normal, it inhibits the pituitary gland from releasing TSH (thyroid stimulating hormone)

• if thyroxine levels are low, the pituitary gland releases TSH and more thyroxine is made by the thyroid until the concentration is normal again