5.1 - Communication and homeostasis

Question 1

What is negative feedback?

Answer 1

• A response that is opposite to the stimulus, returning conditions back to the optimum.
• Brought about by an effector

Question 2

What is positive feedback?

Answer 2

• A response that increases the stimulus, taking conditions further away from the optimum
• For example child birth

Question 3

What is the difference between endotherms and ectotherms?

Answer 3

• Endotherms generate their own heat by metabolic reactions

- Ectotherms rely on the environment to control their body temperature

Question 4

What is an ectotherm? (Cold-blooded)

Answer 4

An organism that is unable to control its body temperature and is reliant on external sources of heat

Question 5

What is an endotherm? (Warm-blooded)

Answer 5

An organism that controls its body temperature in a narrow range using physiological or behavioural adaptations

Question 6

What is homeostasis?

Answer 6

Maintaining a relatively stable internal

environment/state within narrow limits even when the environment is changing

Question 7

What factors need to be kept constant?

Answer 7

• Body temperature
• Blood PH
• Blood glucose
• Water potential, to ensure cells function properly
• Levels of: salt, O2 & CO2
• Blood pressure
• Blood volume

Question 8

How do endotherms regulate their internal temperature?

Answer 8

Their body will be able to regulate the internal temperature

Question 9

How do ectotherms regulate their internal temperature?

Answer 9

Ectotherms will rely on sitting in the sun (basking) or sitting in the shade

Question 10

Why must internal temperature be maintained? (Enzymes)

Answer 10

• To ensure that enzymes have optimal temperature
• This is so they can work properly and not denature if too hot
• Or have a slower reaction rate due to colder temperatures

Question 11

Why must internal temperature be maintained? (Aerobic respiration)

Answer 11

• Ectotherms may warm themselves up is so that they can undergo aerobic respiration
• This means they will be able to produce ATP needed for the active metabolic processes in the body, such as muscle contractions or active transport

Question 12

How do endotherms regulate internal temperature?

Answer 12

• The thermoregulatory centre inside of the hypothalamus is used
• The thermoreceptors inside this centre will monitor the temperature of the blood and will send messages to parts of the body (Via the autonomic nervous system) to increase or decrease the body temperature depending upon what it is at the time

Question 13

How is vasodilation used to regulate temperature?

Answer 13

• Vasodilation is when more blood flows closer to the skin in the capillaries
• The shunt vessel narrows and prevents the blood from flowing away from the surface of the skin, so the blood is redirected to the capillaries closer to the skin
• This means more heat is lost through radiation through the skin
• This causes body temperature to decrease

Question 14

How is vasoconstriction used to regulate temperature?

Answer 14

• Vasoconstriction is when less blood flows closer to the skin in the capillaries and the blood goes through the shunt vessel further away from the skin instead
• This means less heat is lost through radiation through the skin
• This causes body temperature to increase

Question 15

How do hair erector muscles work to regulate body temperature?

Answer 15

• The hair erector muscle contracts or relaxes to cause the hairs to stand on-end or lie flat
• If the hairs stand up it traps an insulating layer of air causing an increase in body temperature

Question 16

How is the body temperature returned back to normal if it increases?

Answer 16

• Change in body temperature is detected by the peripheral temperature receptors in the skin
• The increase in body temperature would be detected by thermoreceptors in the thermoregulatory centre inside the hypothalamus
• Neuronal impact: Motor neurones will bring about a response causing either vasodilation, sweating or relaxation of the hair erector muscles
• Hormonal impact: A decrease in adrenaline production causing a decrease in metabolism which generates heat as a by product of aerobic respiration
• This will bring temperature back to normal

Question 17

How is the body temperature returned back to normal if it decreases?

Answer 17

• Change in body temperature is detected by the peripheral temperature receptors in the
• The decrease in body temperature would be detected by thermoreceptors in the thermoregulatory centre inside the hypothalamus
• Neuronal impact: Motor neurones will bring about a response causing either vasoconstriction, decrease in sweating or contraction of the hair erector muscles
• Hormonal impact: An increase in adrenaline production causing an increase in metabolism which generates heat as a by product of aerobic respiration
• This will bring temperature back to normal

Question 18

What is a receptor?

Answer 18

-Receptors detect a change in the body

Question 19

What is an effector?

Answer 19

-A muscle or gland that is responsible for bringing about a change

Question 20

What is the PH in the blood?

Answer 20

-Blood PH is 7.4 +/- 0.1, a shift of 0.4 leads to death

Question 21

Why must blood glucose concentration be regulated?

Answer 21

• Glucose is used as a respiratory substrate by cells so a constant supply of glucose is needed
• Keeping the blood glucose level constant also ensures a constant water potential

Question 22

Why must the water potential of the blood be regulated?

Answer 22

• Changes in water potential of the blood may cause cells to shrink or expand as water enters or leaves by osmosis
• The water potential must be kept constant otherwise cells cannot function properly

Question 23

How do effectors bring about negative feedback?

Answer 23

-The effector causes a change that brings the internal conditions of the body back to normal (Optimal conditions)

Question 24

How is positive feedback brought about?

Answer 24

• A stimulus causes the conditions of the body to be changed so they are further away from the normal conditions
• The stimulus causes nerve impulses to go to the brain which stimulates the release of hormones to amplify the change and bring about a response