homeostasis and hormonal control

Define homeostasis

Maintaining a stable internal environment that is optimum for enzymes and the functioning of cells

Why must body temperature be kept stable

If it gets too hot the enzymes can denature (lose active site)

If it gets too cold the enzymes slow due to less energy

Why must blood glucose levels be kept stable

• cause cells to lose water by osmosis

• It’s needed for respiration so can cause tiredness and eventually death

Why must water levels be kept stable

• too much, cells can burst

• Too little, cells can shrink

What is the endocrine system

A system composed of glands which secrete hormones directly into the bloodstream, where it is taken to a target organ and causes an effect

Compare the nervous system to the endocrine system

• endocrine : slower response but lasts longer

• Nervous system: faster response but doens’t last very long

Name the gland A, what hormones it produces and the functioning of those hormones

• pituitary gland (master gland)

• ADH, TSH, FSH, LH etc

• Wide range of impacts depending on hormone

Name the gland B, what hormones it produces and the functioning of those hormones

• thyroid

• Thyroxine

• Basal metabolic rate

Name the gland C, what hormones it produces and the functioning of those hormones

• adrenal

• Adrenaline

• Fight or flight instinct

Name the gland D, what hormones it produces and the functioning of those hormones

• pancreas

• Insulin and glucagon

• Blood glucose control

Name the gland E, what hormones it produces and the functioning of those hormones

• ovary

• Oestrogen and progesterone

• Female sexual maturation and menstrual cycle

Name the gland F, what hormones it produces and the functioning of those hormones

• testes

• Testosterone

• Male sexual reproduction

Explain what happens if the thyroxine levels get too high or low

• too high: less TSH produced in the pituitary gland, less thyroxine is produced in thyroid gland, levels return to normal

• Too low: more TSH produced in the pituitary gland, more thyroxine produced in the thyroid gland, levels return to normal

Explain how adrenaline is used in the body

Adrenaline is produced by the adrenal gland in times of fear or stress (no nfl)

Adrenaline increases the heart rate, breathing rate, converts glycogen to glucose and diverts blood to large muscles; all of this to increase muscle contraction for either fight or flight

Where is blood glucose level monitored and controlled

Pancreas

Explain what happens if blood glucose levels get too high or low

• too high: the pancreas produces insulin which causes glucose to move from the bloodstream into the cells, excess glucose is then converted not glycogen for storage (usually in liver and muscle cells)

• Too low: the pancreas produces glucagon which breaks down the glycogen back into glucose which is absorbed into the blood stream

Explain what type 1 and type 2 diabetes is and the difference between them

• type 1 diabetes is a disorder in which the pancreas fails to produce sufficient insulin, this is usually treated with insulin injections

• type 2 diabetes is a disorder in which the body cells no longer respond to the insulin produced in the pancreas, carbohydrate controlled duet abd an exercise regime are common treatments. Obesity is a risk factor.

Type 1 doesn't produce enough insulin, whereas type 2 does but the body just doesn’t respond to it. Type 2 is much more influenced by lifestyle factors like obesity than type 1 which is caused when the body essentially attacks its own pancreas, why this happens is linked to genetics.

Name the three ways which water is lost and state which ways the amount of water lost can be controlled

• exhalation

• sweating

• urination - controllable

Explain how proteins are safely removed from the body

• proteins → amino acids during digestion

• amino acids → ammonia (toxic) during deamination in the liver

• ammonia (toxic) → urea for safe excretion

How does the kidney produce urine

By filtration and selective reabsorption

Explain the process of filtration and selective re absorption

1. Urea, ions, glucose and water are all moved out of the blood into the nephron, red blood cells and proteins are too large so stay in the blood

2. All of the glucose is re absorbed by a combination of diffusion and active transport (depending on conc in blood)

3. The mineral ions and water is reabsorbed from the filtrate depending on what is needed by the body

4. All of the urea is excreted, along with excess ions and water

Explain what happens when blood water levels get too high and too low

Too low: more adh (anti urination) is released from the pituitary gland to prevent losing water through urination by allowing more water to be reabsorbed from the kidney tubules

Too high: less adh (anti urination) is released to increase the amount of water lost through urination by absorbing less water from the kidney tubules

Explain dialysis

Dialysis

• Blood is taken from an artery out of the body into a dialysis machine

• It will then be put next to dialysis fluid across a partially permeable membrane, the fluid will cause the correct amounts of ions, water, glucose and urea to be removed. This can be described as the blood being filtered.

• The blood is then retuned to the body through a vein where it is then pumped around the body by the heart

What are the pros and cons of dialysis

Pros

• no need for immunosuppressants as no risk of rejection

• Can be used whilst waiting for transplant as is more widely available

Cons

• Extremely time consuming

• Side effects e.g muscle fatigue

• Life style restrictions e.g controlled diet

What are the pros and cons of A kidney transplant

Pros

• permanent solution

• Less lifestyle restrictions + better quality of life

• Cheaper

• Very effective

Cons

• risk of infection during surgery

• Has to take immunosuppressants

• Long waiting lists