Hormones: Maintaining Blood Homeostasis Flashcards
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What is homeostasis?
The regulation of the internal conditions of a cell or organism to maintain optimum conditions for function, in response to internal and external changes.
Which three internal conditions are controlled by homeostasis in the human body?
Blood glucose concentration, body temperature and water levels.
Homeostasis maintains optimum conditions for what two things?
Enzyme action and all cell functions.
What are the three parts of all automatic control systems in the body, and what does each do?
Receptors — cells that detect stimuli (changes in the environment); coordination centres (e.g. brain, spinal cord, pancreas) — receive and process information; effectors (muscles or glands) — bring about responses that restore optimum levels.
True or false? Receptors are the cells that bring about the response in a control system.
False. Receptors detect the stimulus; effectors (muscles or glands) bring about the response.
True or false? Automatic control systems in the body may involve nervous responses or chemical responses.
True. Some control systems use nerve impulses, others use hormones.
How does the endocrine system bring about an effect in the body?
Glands secrete hormones directly into the bloodstream; the blood carries the hormone to a target organ where it produces an effect.
Give three ways coordination by the endocrine system differs from coordination by the nervous system.
Slower; longer-lasting; chemical (hormones) carried in the blood instead of electrical impulses along neurones.
True or false? Hormones travel to their target organs along neurones.
False. Hormones are secreted into the bloodstream and carried to target organs in the blood.
Why is the pituitary gland called the 'master gland'?
It secretes several hormones into the blood in response to body conditions, and these hormones act on other glands to stimulate them to release other hormones.
Which six endocrine glands must you be able to identify on a diagram of the human body?
Pituitary gland, thyroid, adrenal glands, pancreas, ovaries (female) and testes (male).
Where in the body are the pituitary gland, thyroid and adrenal glands found?
Pituitary — in the brain; thyroid — in the neck; adrenal glands — one on top of each kidney.
Which organ monitors and controls blood glucose concentration?
The pancreas.
What are the steps in the response to a blood glucose concentration that is too high?
e.g. after a sugary meal
- The pancreas produces the hormone insulin.
- Insulin causes glucose to move from the blood into the cells.
- In liver and muscle cells excess glucose is converted to glycogen for storage, so blood glucose falls.
What causes Type 1 diabetes and how is it normally treated?
The pancreas fails to produce sufficient insulin, giving uncontrolled high blood glucose; it is normally treated with insulin injections.
True or false? In Type 2 diabetes the pancreas produces no insulin at all.
False. In Type 2 diabetes the body cells no longer respond to the insulin the pancreas produces; treatment is a carbohydrate controlled diet and exercise, and obesity is a risk factor.
How is water lost from the body, and which of these losses are controlled?
Water is lost via the lungs in exhaled air, and with ions and urea from the skin in sweat — neither is controlled; excess water, ions and urea are removed by the kidneys in urine, which is controlled.
What is the effect on body cells if they lose or gain too much water by osmosis?
They do not function efficiently, because osmotic changes make cells shrink or swell.
What happens to the excess amino acids produced by digesting protein?
They are deaminated in the liver to form ammonia; ammonia is toxic so it is immediately converted to urea for safe excretion.
What effect does ADH have on the kidney tubules, and when is it released?
ADH makes the kidney tubules more permeable to water, so more water is reabsorbed into the blood; it is released by the pituitary gland when the blood is too concentrated, controlled by negative feedback.
Which hormone does the pancreas produce when blood glucose concentration is too low, and what does it do?
Glucagon — it causes glycogen in the liver to be converted into glucose, which is released into the blood.
True or false? Insulin and glucagon have opposite effects and work in a negative feedback cycle to control blood glucose concentration.
True. Insulin lowers blood glucose and glucagon raises it, bringing the concentration back to normal.
On a graph of blood glucose concentration after a meal, how does a person with untreated diabetes differ from a person without diabetes?
Their blood glucose rises higher and stays high, instead of returning to the normal level.
True or false? On a graph for a person without diabetes, blood insulin concentration rises after blood glucose concentration has risen.
True. The pancreas releases insulin in response to the rise in blood glucose.
What are the steps by which the kidneys produce urine?
e.g. blood flowing through the kidney after a meal
- Filtration: water, ions, glucose and urea are filtered out of the blood.
- Selective reabsorption: all the glucose, plus some ions and water, are taken back into the blood.
- The remaining water, ions and urea leave the body as urine.
What is selective reabsorption in the kidney?
Taking useful substances — all the glucose, some ions and some water — back into the blood from the kidney tubules.
Which substance in blood plasma is not filtered out of the blood in the kidney?
Protein — its molecules are too large to be filtered out.
True or false? In a healthy person, urine contains the same concentration of glucose as the fluid just after filtration.
False. Glucose is filtered out but all of it is reabsorbed, so healthy urine contains no glucose.
What are the basic principles of kidney dialysis?
Blood flows on one side of a partially permeable membrane and dialysis fluid on the other, so urea and excess ions and water pass out of the blood.
Give one advantage and one disadvantage of a kidney transplant compared with dialysis.
Advantage: no need for regular dialysis sessions. Disadvantage: donor kidneys are in short supply and may be rejected.