fight or flight

Question 1

what is the fight or flight response?

Answer 1

• a response all mammals have
• that detects potentially threatening situation
• and causes the body to automatically trigger a set of responses
• to help mammal survive

Question 2

describe how the fight or flight response works?

Answer 2

1. the hypothalamus detects stressors which communicates with the sympathetic NS and adrenal glands
2. so it involves the NS and endocrine glands
3. the sympathetic NS sends nerve impulses to initiate a response from effectors
4. the adrenal medulla releases adrenaline (epinephrine) and noradrenaline
5. the crf causes the pituitary gland release adrenocorticotrophic hormone (ACTH)
6. which stimulates the release of hormones like cortisol from the adrenal cortex to be released

Question 3

glucocorticoids (cortisol) regulate carbohydrate metabolism and stimulate the release of glucose from glycogen. why is this useful?

Answer 3

increased cell glucose conc = increased cell resp rate = increased ATP production per sec = more energy for muscle contraction to run or face danger

Question 4

What is the benefit of using both the NS & the endocrine system in this response?

Answer 4

NS provides immediate and fast response
Endocrine provides longer lasting response if danger persists

Question 5

survival value of pupils dilating

Answer 5

more light can enter eyes, so you can see more clearly/ retina more sensitive

Question 6

survival value of increased HR and BP

Answer 6

increases rate of blood flow, so more oxygen and glucose to muscle cells

Question 7

survival value of increased blood glucose levels

Answer 7

supplies energy for muscular contraction

Question 8

survival value of vasoconstriction for arterioles in digestive system and skin and vasodilation for arterioles in muscles and liver

Answer 8

diverts blood flow away from the skin and and digestive system and towards the muscles

Question 9

survival value of increased metabolic rate

Answer 9

increased resp so glucose metabolised for atp energy

Question 10

survival value of increased ventilation rate

Answer 10

more gas exchange so more oxygen enters blood = so more resp occurs

Question 11

survival value of endorphins (natural painkillers)

Answer 11

wounds don’t prevent activity

Question 12

describe the control of the heart rate

Answer 12

• autonomic NS (involuntary control)
• controlled by cardiovascular system
• in the medulla oblongata

Question 13

describe the centre that increases heart rate?

Answer 13

• it sends more frequent nerve impulses along the sympathetic/accelerator nerve to SAN in heart
• increases frequency of waves of electrical excitation across atrial walls

Question 14

describe the centre that decreases heart rate?

Answer 14

• it sends more frequent nerve impulses along the parasympathetic/ vagus nerve to SAN in the heart
• decreases frequency of waves of electrical excitation across atrial walls

Question 15

describe chemoreceptors

Answer 15

• detect changes in chemicals
• located in aorta, carotid artery, medulla

Question 16

explain how chemoreceptors work

Answer 16

1. detect pH changes in blood
2. increased activity = increased cell resp rate = more CO2 released
3. CO2 dissolves in plasma forming carbonic acid
4. chemoreceptors detect decrease in pH
5. send nerve impulses along sympathetic nerve to SAN
6. this increases frequency at which SAN sends out electrical impulses
7. increasing HR

Question 17

describe baroreceptors

Answer 17

• pressure receptors
• detect changes in blood pressure
• located in aorta, vena cava, carotid artery

Question 18

role of hormones in regulating HR?

Answer 18

• stress causes adrenal medulla to release adrenaline/noradrenaline into blood
• they reach heart and directly effect cells in SAN
• causes more frequent electrical impulses
• increases HR

Question 18

explain how baroreceptors wok

Answer 18

1. detect increased blood pressure
2. sends nerve impulses to medulla oblongata
3. which sends more frequent nerve impulses along vagus nerve/ parasympathetic nerve to SAN
4. this reduces the frequency at which the SAN sends out electrical impulses
5. decreases HR

(fall in bp would stimulate accelerator nerve instead + do opposite)