Hormonal communication- coordinated responses

Question 1

How does the flight or fight response occur?

Answer 1

-threat detected by autonomic nervous system
-hypothalamus communicates with sympathetic nervous system (neurones) and the adrenal-cordial system (hormones). These combined affects create a fight or flight response.

Question 2

Role of the sympathetic nervous system in the fight or flight response?

Answer 2

send out impulses to glands and smooth muscles and tells adrenal medulla to release adrenaline and noradrenaline (stress hormones) into blood which cause severe changes in body (e.g increased heart rate)

Question 3

Describe the role of other stress hormones apart form adrenaline?

Answer 3

-longer term action from the adrenal cortex is controlled by hormones produced by pituitary gland in the brain.
-The hypothalamus stimulates pituitary gland to secrete adrenocorticotropic hormone (ACTH).
-This travels in the blood to the adrenal cortex, where it activates the release of of many hormones which prepare for the threat

Question 4

Why does heart rate increase?

Answer 4

to pump more oxygenated blood around the body

Question 5

why do pupils dilate?

Answer 5

to take in as much light as possible for better vision

Question 6

why do arterioles in the skin constrict?

Answer 6

more blood to major muscle groups, brain, heart and muscles for ventilation

Question 7

why do blood glucose levels increase?

Answer 7

increased respiration for more energy for muscle contraction

Question 8

why do smooth muscle of airways relax?

Answer 8

to allow more oxygen into the lungs

Question 9

why do non essential systems (like digestion) shut down?

Answer 9

to focus on resources on emergency functions

Question 10

why is there difficulty when focusing on small tasks?

Answer 10

brain solely focused on where threat is coming from

Question 11

what is one of adrenalines main functions?

Answer 11

to trigger liver cells to undergo glycogenolysis so glucose is released into the blood stream for respiration

Question 12

How does adrenaline trigger glycogenolysis in the liver cells?

Answer 12

as adrenaline is a hormone and hyphphilic, it cannot pass through the cell membrane so it binds with receptors on the surface, triggering a chain reaction inside the cell

Question 13

what reaction chain occurs inside a liver cell when adrenaline binds?

Answer 13

-adrenaline binds to receptor causing enzyme adenyl cyclase to be activated (adrenaline-receptor complex)
-Adenyl cyclase triggers the conversion of ATP into cyclic adenosine mono-phosphate (cAMP) on the inner surface of the cell membrane in the cytoplasm
-The increase in cAMP levels activates enzymes called protein kinases which phosphorylate and hence activate other enzymes. Enzymes are activated which trigger the conversion of glycogen into glucose.

Question 14

what is the first and second messenger?

Answer 14

first- adrenaline
second- cAMP

Question 15

what part of the brain is responsible for controlling heart rate?

Answer 15

medulla oblongata

Question 16

Describe the two centres of the the medulla oblongata which is linked to the SAN in the heart

Answer 16

-one centre increases heart rate by sending impulses through the sympathetic nervous system, these impulses are transmitted by the accelerator nerve
-one centre decreases heart rate by sending impulses through the parasympathetic nervous system, these impulses are transmitted by the vagus nerve.

Question 17

changes in heart rate are dependent on?

Answer 17

blood pressure, pH of blood and stress responses

Question 18

What are baroreceptors?

Answer 18

receptors which detect changes in blood pressure. E.g if a person’s blood pressure is low, the heart rate increases to prevent fainting. Baroreceptors are located in the aorta, vena cava and the carotid arteries.

Question 19

What are chemoreceptors?

Answer 19

receptors which detect changes in the level of particular chemicals in the blood such as carbon dioxide. Chemoreceptors are located in the aorta, the carotid artery and the medulla

Question 20

Why does the pH of blood decrease when carbon dioxide levels in the blood increase?

Answer 20

carbonic acid is formed when carbon dioxide interacts with water in the blood. If chemoreceptors detect a decrease in blood pH, a response is quickly triggered to increase heart rate- therefore blood flows more quickly to the lungs so carbon dioxide can be exhaled

Question 21

Describe the process of what happens when there is an increased muscular/ metabolic activity?

Answer 21

-more carbon dioxide produced by tissues from increased respiration
-blood pH lowered
-centre in medulla oblongata that speeds heart rate, increases frequency of impulses to SAN via the sympathetic nervous system
-SAN increases heart rate
-increased blood flow removes carbon dioxide faster
-carbon dioxide level returns to normal

Question 22

What occurs when the carbon dioxide level in blood decreases?

Answer 22

pH of the blood rises which is detected by chemoreceptors in the wall of the carotid arteries and the aorta. This results in a reduction in the frequency of the nerve impulses being sent to the SAN via the sympathetic nervous system and thus heart rate decreases back to its normal level.

Question 22

What occurs when the carbon dioxide level in blood decreases?

Answer 22

pH of the blood rises which is detected by chemoreceptors in the wall of the carotid arteries and the aorta. This results in a reduction in the frequency of the nerve impulses being sent to the SAN via the sympathetic nervous system and thus heart rate decreases back to its normal level.

Question 23

What occurs when blood pressure is too high?

Answer 23

-baroreceptors detect this change
-impulses are sent to the medulla oblongata centre which decreases heart rate
-medulla oblongata sends impulses along the parasympathetic neurones to the SAN which decreases heart rate back to normal

Question 24

What occurs if blood pressure is too low?

Answer 24

-baroreceptors detect this change
-impulses are sent to the medulla oblongata centre which increases heart rate
-the medulla oblongata sends impulses along sympathetic neurones to the SAN which increases heart rate and returns blood pressure back to normal

Question 25

How do hormones affect heart rate?

Answer 25

In times of stress, adrenaline and noradrenaline are released. These hormones affect the pacemaker region o the heart itself- they speed up heart rate by increasing frequency of impulses produced by SAN.