Negative Feedback and Homeostasis

Question 1

What is the purpose of homeostasis?

Answer 1

to maintain a stable internal environment

Question 2

What is a norm value/set point?

Answer 2

the condition that is optimal, one which attempts are made to maintain

Question 3

What is the function of a receptor?

Answer 3

to detect deviations from the norm, they send signals to effectors

Question 4

What is the funcition of effectors?

Answer 4

To restore internal conditions to the norm value/set point

Question 5

What is negative feedback?

Answer 5

a system which serves to reverse a change which has occured

Question 6

Where is the cardiovascular control centre found?

Answer 6

the medulla

Question 7

Name two receptors involved in control of the heart.

Answer 7

Stretch receptors in the muscle walls of the heart

Baroreceptors in the carotid arteries of the neck (detect pressure)

Question 8

What does the parasympathetic nervous system do?

Answer 8

slows down heart rate

Question 9

What does the sympathetic nervous system do?

Answer 9

speeds up heart rate

Question 10

What happens (to the heart rate) when excersise ends?

Answer 10

• blood pressure increases in arteries so baroreceptors and stretched
• they send nerve impulses to the cardiovascular control centre which send impulses through the parasympathetic system to slow down the heart rate and cause vasodilation.
• blood pressure lowers

Question 11

What happens (to the heart rate) when exercise starts ?

Answer 11

-blood vessels dilate in response to adrenaline
blood pressure falls
- this reduces the stretch of the baroreceptors and they almost stop responding
- the cardiovascular control centre is not stimulated so it sends signals along the sympathetic system to stimulate the heart rate.
- blood pressure increases

Question 12

Where is the ventilation/respiratory centre?

Answer 12

the medulla

Question 13

describe the process of basic breathing.

Answer 13

• impulses from the respiratory centre travel along sympathetic nerves causing the intercostal muscles an diaphram to contract
• the lungs inflate and we inhale
• stretch receptors on the walls of the bronchi send nerve impulses to the respiratory centre
• these impulses cause the breathing muscles to relax so we exhale

Question 14

Name two receptors involved in the control of breathing.

Answer 14

stretch receptors on the walls of the bronchi

chemorecpetors in the aortic bodies and carotid bodies (sensitive to levels of CO2 and pH)

Question 15

What do chemoreceptors do when CO2 levels are too high?

Answer 15

send impulses to the respiratory centre which send impulses to the breathing muscles to increase breathing rate.

Question 16

Where are the two types of temperature receptors found, and why is this an advantage to us?

Answer 16

the hypothalamus
the skin

It allows for great sensitivity not only to actual changes but to potential changes too (eg, if the skin receptors are cold the body can adjust so the core temperature doesn’t drop too)

Question 17

Describe the process of vasodialtion.

Answer 17

• sphincter muscles around the arterioles leading to the capilliaries are not stimulated to contract, so they relax
• more blood flows to capillaries close to the air and less blood flows through shunt vessels
• heat is lost by conduction and radiation

Question 18

Describe the process of vasoconstriction.

Answer 18

• sphincter muscles around the arterioles leading to the capilliaries contract
• constricts capillaries and more blood flows through the shunt vesses, further from the air
• less heat is lost by conduction and radiation