5.5.8(coordinating responses

Describe 3 ways in which the brain coordinates responses

• Action potentials in the somatic nervous system

• Action potentials in the sympathetic and parasympathetic parts of the autonomic nervous system

• Release hormones via the hypothalamus and pituitary gland

Describe the physiological changes which occur during fight or flight

• Pupils dilate

• Heart rate and blood pressure increases

• Blood vessels are dilated at the muscle and liver tissue

• Blood glucose levels increase

• Metabolic rate increases

• Erector pili muscles in the skin contract

• Ventilation rate and depth increase

• Endorphins are released in the brain

Explain why endorphins are released during fight or flight

• Endorphins are natural pain killers

• Wounds inflicted on the mammal do not prevent activity

Explain why erector pili muscles on the skin contract

• This is because it makes hair stand up - which is a sign of aggression and to look larger

Describe what is meant by a steroid and a non-steroid hormone

• Steroid hormones:

  • Fat soluble hormones made from cholesterol

  • They can pass through the membrane and enter the cell and the nucleus

• non-steroid hormones:

  • They are protein and peptide hormones and derivatives of amino acids

  • They are not soluble in the phospholipid bilayer and cannot enter the cell via diffusion

  • They are cell signalling molecules - first messengers

  • Need to bind to cell surface membrane receptors and release a second messenger inside of the cell

Describe what hormone adrenaline is classed as

• non-steroidal hormone - peptide hormone

• Not soluble in the phospholipid bilayer and cannot enter cells

• It is known as a cell signalling molecule(first messenger)

• Needs to bind to cell surface receptors and release a second messenger inside of the cell

Describe the process of the release of adrenaline

• A threat stimulus is detected by sensory neurones and send electrical impulses to receptors in the cerebrum

• The impulses then travel to the hypothalamus and the hypothalamus is then stimulated

• The hypothalamus sends electrical signals down the sympathetic nervous system to the adrenal glands, specifically the adrenal medulla

• This causes the release of adrenaline

Describe the mechanism of adrenaline action

• Adrenaline binds to the adrenaline receptor on the plasma membrane

• This receptor is associated with a G protein on the inner surface of the plasma membrane

• The receptor activates G protein which causes the activation of adenyl cyclase

• Adenyl cyclase converts ATP to cyclic AMP(cAMP), which is the secondary messenger inside the cell

• cAMP activates an enzyme cascade within the cell

Describe the process of the release of Cortisol

• A threat stimulus is detected by sensory neurones and send electrical impulses to receptors in the cerebrum

• The impulses then travel to the hypothalamus and the hypothalamus is then stimulated

• The hypothalamus then causes the production of a peptide hormone which stimulates the production of ACTH from the pituitary gland

• ACTH then travels down the blood to the andrenal cortex of the adrenal gland

• This causes the release of cortisol

Describe the effects of cortisol

• Causes an increase in blood pressure

• Causes an increase in blood glucose concentration

Name the hormones released by the pituitary gland

• TRH is released by the pituitary gland which stimulates the thyroid gland to release more thyroxine.

• ACTH is released by the pituitary gland which stimulates the adrenal cortex to release cortisol