animal coordination, control and homeostasis

Adrenaline

• Adrenaline binds to specific receptors in the heart

• Heart contracts more frequently with more force so heart rate and blood pressure increase

• This increases blood flow to muscles so cells receive more oxygen and glucose increasing respiration

• Adrenaline also binds to receptors in the liver, breaking down glycogen stores to release glucose

• This increases blood glucose level

Thyroxine

• When thyroxine levels are too low, it stimulates release of TRH in the hypothalamus which stimulates the release of TSH in the pituitary gland

• TSH stimulates the release of thyroxine in the thyroid glands

• When thyroxine levels are too high, it inhibits release of TRH and TSH

• Therefore, the level of thyroxine lowers