Biology Hacked: Homeostasis Summarised

Biology Hacked: Homeostasis

·    Homeostasis:  The process of maintaining a constant internal environment

·    Controls

o   Temperature

o   Water content

o   Energy

o   Oxygen

o   Concentration of wastes in blood

·        Involves receptors that are sensitive to a stimulus, and effectors that have an effect on the same stimulus.

Controlling Body Temperature

·        Metabolism-all the chemical reactions occurring in the cells

·        Endothermic-maintain a constant body temperature

·        Above 37 degrees=metabolism stops

·        Below 37 degrees=metabolism slows down

Control of temperature (NS and endocrine system)

Temperature is controlled by both the endocrine and NS system

·        Endocrine system control

·        Hypothalamus (receives information from temperature receptors and itself) Acts on pituitary.

·        pituitary which secretes more thyroid-stimulating hormone(TSH)(TSH-increases temperature)

·        Thyroid releases thyroxine.

·        Thyroxine causes rate of metabolism to increase=body is heated and warmed

·        Slow response

·        NS control

·        Hypothalamus detects fall in temperature

o   Shivering(increases activity of muscle cells)

o   Reduces blood flow to skin(constriction of blood vessels)

·        Hypothalamus detects increase in temperature

o   Sweat glands-sweat evaporates (depends on temperature and humidity)

o   Blood vessels-expand (blush)

Water Balance Control

·        Kidneys play an important roll

o   Microscopic filters remove wastes (e.g. urea), salts and water from the blood.

o   Kidney returns the blood the salts, glucose and water needed by the body

o   Wastes pass into bladder

·        Food, drink and cellular respiration = gain fluids

·        Breathing out, sweat, faeces and urine=loose fluids

·        Antidiuretic hormone-controls the amount of water in urine

o   Causes kidneys to reabsorb from the renal tubules.

o   Secreted by the pituitary gland under control of the hypothalamus.

§  Hypothalamus monitors concentration of water in blood.

§  Dehydration=increases ADH production