bio homeostsis

Reflex arc

1. Stimulus

2. Receptor

3. Sensory neurone

4. Relay neurone (in the CNS/spinal cord)

5. Motor neurone

6. Effector (muscle or gland)

7. Response

Homeostasis

1. Stimulus (change in internal conditions)

2. Receptor detects change

3. Coordination centre (brain/pancreas etc.)

4. Effector

5. Response

6. Negative feedback restores normal level

Synapse

1. Electrical impulse arrives at the end of the first neurone

2. Neurotransmitter is released from the neurone

3. Neurotransmitter diffuses across the synaptic gap

4. It binds to receptors on the next neurone

5. This triggers a new electrical impulse in the next neurone

Homeostasis uses: maintain blood glucose concentration

1. You eat → blood glucose rises

2. The pancreas releases insulin

3. Insulin makes cells:

   • Take in glucose from the blood

   • Store it (especially in the liver as glycogen)

4. Causes stored glycogen → glucose

5. Releases it into the blood

6. Blood glucose goes up

Homeostasis uses: maintain body temperature

• When you’re cold → vasoconstriction

• Blood vessels constrict

• Keeps warm blood deeper in the body → helps maintain body temperature

• Cold=shiver/hair stand up to trap air as insulation

• When you’re hot →vasodilation

• Blood vessels dilate

• Blood flow to surface near skin →more heat energy loss

• Cool blood =cool body

• Hot=sweat

Homeostasis uses: maintain water level

• ADH= Produced in the brain, acts on the kidneys

• Controls how much water is reabsorbed

• Low water in blood → more ADH → more water reabsorbed → concentrated urine

• High water in blood → less ADH → less reabsorption → dilute urine