14.5 Coordinated Responses

Question 1

Which part of the nervous system first detects a threat?

Answer 1

Autonomic

(responsible for regulating involuntary physiological processes, e.g heart rate)

Question 2

How does the hypothalamus bring about the “Fight or Flight” response?

Answer 2

1. threat detected by autonomic nervous system

• Hypothalamus activates SYMPATHETIC NERVOUS SYSTEM
  
  • activates glands & smooth muscles
  • activates adrenal medulla >> release of adrenaline & noradrenaline into bloodstream
• Hypothalamus releases CRF
  
  • causes pituitary gland to secrete ACTH, which causes adrenal cortex to release approx 30 hormones into bloodstream

these changes bring about “fight or flight” responses.

Question 3

What physiological changes occur during the “fight or flight” response?

Answer 3

• ￪ HEART RATE
  
  • Greater volume of blood travels to cells per unit time, more oxygen & nutrients delivered to cells for respiration
• PUPILS DILATE
  
  • Take in as much light as possible >> better vision & awareness of danger
• ARTERIOLES IN SKIN CONSTRICT
  
  • Directs blood towards major muscle groups, heart, lungs e.t.c. Other organ systems are not vital for reacting to danger
• BLOOD GLUCOSE LEVEL INCREASES
  
  • Increase respiration >> provide energy for muscle contraction
• SMOOTH MUSCLE OF AIRWAYS RELAX
  
  • Allow more oxygen into lungs & more diffusion into blood

Question 4

What is the role of adrenaline?

Answer 4

triggers glycogenolysis in hepatocytes

(to increase blood glucose concentration

for respiration & energy)

Question 5

Outline the mechanism of action for an adrenaline molecule:

Answer 5

1. Adrenaline molecule binds to complementary specific receptor on plasma membrane of target molecule, e.g hepatocyte
2. activates adenylyl cyclase enzyme.
3. adenylyl cyclase catalyses conversion of ATP ⟶ cAMP on inner surface of membrane
4. cAMP activates protein kinases,
5. Each protein kinase molecule activates a number of other enzymes involved in hydrolysis of glycogen to glucose

cascade effect, since number of molecules increases at each step.

Question 6

Mechanism of action of adrenaline:

adrenaline >> _____ >> ATP ⟶ ____ >> ____ >> activates hormones

Answer 6

adenylyl cyclase

cAMP

protein kinases