homeostasis processes

reflex arc

1. stimulus detected by receptor

2. coordination processes change

3. electrical impulses pass along sensory neuron to the CNS

4. at the end of the sensory neuron (synapse) a chemical is released

5. chemical diffuses to relay neuron in CNS

6. triggers an electrical impulse

7. passes across relay neuron to another synapse

8. chemical released triggering electrical impulse in the motor neuron to an effector

dark room

• light receptors sense change in the retina

• circular muscles relax

• radial muscles contract

• dilated pupil - more light in

bright room

• light receptors sense change in the retina

• radial muscles relax

• circular muscles contract

• contracted pupil - less light in

near object

• ciliary muscles contract

• suspensory ligaments loosen

• thicker lens - light is refracted strongly

distant object

• ciliary muscles relax

• suspensory ligaments contract

• thinner lens - light is refracted slightly

low glucose level

• pancreas does not secrete insulin into blood

• liver does not convert glucose into glycogen

• not absorbed into blood stream

• blood glucose level increases

high glucose level

• pancreases does secrete insulin into blood

• liver converts glucose into glycogen

• absorbed into blood stream

• blood glucose level decreases

kidney

1. filtration - small molecules pass through nephron including urea, glucose and water

2. selective reabsorption - reabsorb molecules that are needed including all glucose that was filtered out, as much water as the body needs to maintain a constant water level in blood, ions as the body needed

3. urine - molecules not reabsorbed continue along nephron as urine (urea, excess water and ions)

too much water in blood (low concentration/dilute)

• hypothalamus detects water level

• pituitary gland releases less ADH

• less water reabsorbed by kidneys

• more water lose in urine

• blood water level returns to normal

too little water in blood (high concentration/concentrated)

• hypothalamus detects water level

• pituitary gland releases ADH

• more water reabsorbed by kidneys

• less water lose in urine

• blood water level returns to normal

excess amino acids

• digest protein

• liver breaks down excess amino acids

• produces ammonia (deamination)

• ammonia is toxic —> converted to urea

hormones involved with menstrual cycle

• FHS - matures egg

• LH - stimulates release of egg

• oestrogen - repairing and thickening lining

• progesterone - maintains it

menstrual cycle

• day 1 - 14: FHS released by pituitary gland , FSH travels in blood to ovaries and egg matures, FSH triggers oestrogen —> thickens lining

• day 14 - 28: oestrogen stops FSH, instead LH triggers ovulation, mature egg released

• day 29: progesterone produced - stops FSH/LH prevents more then one egg from maturing, fertilisation does not take place progesterone falls - period