5.1.1 Communication and homeostasis

Question 1

Define homeostasis.

Answer 1

The maintenance of a constant internal environment despite external changes.

Question 2

Why is homeostasis important?

Answer 2

It ensures the maintenance of optimal conditions for enzyme action and cell function.

Question 3

What are the three key homeostatic mechanisms?

Answer 3

Thermoregulation
Osmoregulation
Blood glucose concentration.

Question 4

Define stimulus

Answer 4

A change in the external or internal environment

Question 5

What is the role of a receptor?

Answer 5

Detect stimuli.

Question 6

Role of effector?

Answer 6

Bring about a response to a stimulus to produce an effect.

Question 7

What is cell signalling?

Answer 7

When receptors communicate with effectors and other cells in order to produce a response.

Question 8

Where can cell signalling occur?

Answer 8

Between either adjacent or distant cells.

Question 9

Define negative feedback.

Answer 9

Self-regulatory mechanisms which return internal environment to optimum when there is a fluctuation.

Question 10

Explain negative feedback.

Answer 10

-Receptors detect when a level is too high or low and it is communicated via the nervous system.
-The effectors respond to counteract the change by bringing the level back down to normal.

Question 11

Does negative feedback always work?

Answer 11

No, if the change is too big then the body cannot counteract this.

Question 12

What should normal human body temperature be?

Answer 12

Within 0.5ºc above or below 37ºc.

Question 13

What is positive feedback?

Answer 13

Body ENHANCES original stimulus to make deviation greater.

Question 14

Give an example of positive feedback.

Answer 14

blood clotting after an injury releases a chemical which triggers more blood clotting to stop bleeding out.

Question 15

What are the two communication systems in mammals?

Answer 15

Nervous and endocrine

Question 16

What is the word for the control of body temperature.

Answer 16

Thermoregulation

Question 17

How do endotherms regulate their body temperature?

Answer 17

Homeostasis

Question 18

What is an ectotherm?

Answer 18

An organism that relies on external sources of heat to maintain body temperature.

Question 19

Give an example of an ectotherm.

Answer 19

Reptile.

Question 20

What is an endotherm?

Answer 20

An organism that uses heat from metabolic reactions to maintain body temperature.

Question 21

What does the temperature of an ectotherm depend on?

Answer 21

The external environment.

Question 22

Give some mechanisms to reduce body temperature.

Answer 22

1) sweating
2) hairs lie flat (erector pilli muscles relax)
3) vasodilation

Question 23

How does sweating help to reduce body temperature?

Answer 23

More sweat secreted from sweat glands. The water in sweat evaporates from the surface of the skin and takes heat away from the body.

Question 24

How does hairs lying flat reduce body temperature?

Answer 24

Mammals have a layer of hair that provides insulation. Erector pilli muscles relax so that the skin is less insulation and heat can be lost more easily

Question 25

How does vasodilation reduce body temperature?

Answer 25

Arterioles near surface of skin dilate meaning more blood flowed through the capillaries close to the skin so heat is lost through the skin.

Question 26

State some mechanisms to increase body temperature.

Answer 26

1) shivering
2) erector pilli muscles contract
3) less sweat
4) hormones
5) vasoconstriction

Question 27

How does shivering increase body temperature?

Answer 27

When it’s cold, muscles contract in spasms. This makes the body shiver and more heat is produced from increased respiration.

Question 28

How does producing less sweat increase body temperature?

Answer 28

Les sweat is secreted from the sweat glands when it is cold and this reduces heat loss

Question 29

How does the hairs standing up increase body temperature?

Answer 29

Erector pili muscles contract when its cold,which makes the hair stand up. This traps air as a layer of insulation and so prevents heat loss.

Question 30

How do hormones increase body temperature?

Answer 30

the body releases adrenaline and thyroxine. these increase metabolism so more heat is produced.

Question 31

How does vasoconstriction increase body temperature?

Answer 31

When it is cold, arterioles near the surface of the skin constrict so less blood flows through the capillaries and less heat is lost.

Question 32

Which part of the brain controls body temperature in mammals.

Answer 32

hypothalamus

Question 33

How does the hypothalamus reduce body temperature?

Answer 33

-Thermoreceptors detect temp too high.
-The hypothalamus sends signals to effectors.
-Vasodilation, sweating, hairs laying flat, no shivering, no adrenaline or thyroxine release all occur.
-Temperature back to normal.

Question 34

How does the hypothalamus increase body temperature?

Answer 34

Thermoreceptors detect temp too low.
-The hypothalamus sends signals to effectors.
-Vasoconstriction, shivering, hairs standing upright, no sweating, adrenaline or thyroxine release all occur.
-More heat produced and conserved by the body.

Question 35

give an example of an endotherm

Answer 35

human