5.1

Question 1

Define cell signalling.

Answer 1

The way in which cells communicate with each other.

Question 2

What are conditions that need to be maintained in the body?

Answer 2

• pH
• Temperature
• Aqueous environment for products and substrates in solution
• Free from toxins and excess inhibitors

Question 3

Define stimulus.

Answer 3

Change in internal or external environment.

Question 4

Define response.

Answer 4

Change in behaviour and physiology as a result of stimulus.

Question 5

What makes a communication pathway good?

Answer 5

• Rapid communication
• Covers whole body
• Enables specific response
• Enables short/long term responses
• Enables cell to cell communication

Question 6

Define effector.

Answer 6

Cells, tissue or organs which bring about a response.

Question 7

Define homeostasis.

Answer 7

Maintaining constant internal environment despite changes in the internal or external environment.

Question 8

Define Negative Feedback.

Answer 8

A mechanism which reverses a change bringing the system back to the optimum.

Question 9

Define Positive Feedback.

Answer 9

A mechanism which increases a change moving a system further away from the optimum.

Question 10

Define Sensory receptor.

Answer 10

Cell/sensory nerve endings which can detect a stimulus in internal or external environment and create an action potential in response.

Question 11

What does homeostasis regulate?

Answer 11

• Body temperature
• Blood glucose concentration
• Blood salt concentration
• Blood pressure
• Carbon dioxide concentration
• Blood water potential

Question 12

Explain the standard communication pathway.

Answer 12

Stimulus -> Receptor -> Communication pathway (cell signalling) -> effector -> response

Question 13

What part of brain controls temperature?

Answer 13

Thermoregulatory centre in the hypothalamus.

Question 14

Example of useful positive feedback?

Answer 14

Cervix dilates causing posterior pituitary gland to produce oxytocin which causes uterine contractions further dilating cervix producing more oxytocin. Stops when birth complete.

Question 15

Define ectotherm?

Answer 15

An organism that relies on the external sources of heat to regulate its body temperature.

Question 16

Define endotherm?

Answer 16

An organism that relies on metabolic reaction to regulate body temperature.

Question 17

How do ectotherms react to low temperature?

Answer 17

• Move into sunny area
• Expose greater surface area to sun
• Lie on warm surface

Question 18

How do ectotherms react to high temperature?

Answer 18

• Move to shade area
• Decrease surface area exposed to sun
• Go underground

Question 19

How does a snake regulate body temperature?

Answer 19

Basks in the sun next to vegetation allow direct contact with skin increasing body temperature.

Question 20

How does a locus regulate body temperature?

Answer 20

Start of the day puts his body side on to sun allowing large surface area exposed to sun.

Mid day faces sun head on decreasing surface area.

Moves to top of plants as soil releases heat through radiation as a result of being warmed up by the sun.

Also they can change depth and rate of breathing

Question 21

How does a lizard regulate temperature?

Answer 21

Goes into burrows or crevices in the coolest and warmest points of day as crevice has constant temperature.

Question 22

How does a horned lizard regulate temperature?

Answer 22

Expands and contracts rib cage controlling surface area exposed to sun.

Question 23

What are the advantages of ectothermy?

Answer 23

• Less food used for respiration.
• Nutrient and energy from food used for growth.
• Less time/energy spent on finding food.
• Can survive longer without food.

Question 24

Disadvantage of ectothermy?

Answer 24

• In cold temperatures they are inactive therefore at threat of predation.

Question 25

What is the hypothalamus?

Answer 25

The part of the brain which controls homeostatic responses.

Question 26

What happens to your skin when body is too hot?

Answer 26

- Sweat glands produce fluids which evaporate using heat from blood as latent heat of vaporisation. - Hairs and feathers lie flat to stop insulation - Vasodilation occurs causing arterioles and pre capillary sphincters to direct blood to skin surface which leaves through radiation.

Question 27

What happens to skin when too cold?

Answer 27

- Sweat glands will stop production of fluids. - Hair and feathers erect to trap hair and insulate skin - Vasoconstriction diverts blood away from skin surface to stop heat loss through radiation.

Question 28

What happens to gaseous exchange system when too hot?

Answer 28

Animals pant which causes water in airways to evaporate using heat from blood for latent heat of vaporisation.

Question 29

What happens to gaseous exchange system when too cold?

Answer 29

Less panting to avoid heat loss.

Question 30

What happens in liver when body is too hot?

Answer 30

Liver cells stop respirating so that less heat is lost.

Question 31

What happens in liver when body is too cold?

Answer 31

Increased respiration of liver cells causing energy from food to be turned into heat.

Question 32

What happens to skeletal muscles when body is too hot?

Answer 32

Less contraction to stop release of energy via respiration.

Question 33

What happens to skeletal muscles when body is too cold?

Answer 33

More contractions occurs (shivering) generating heat through respiration.

Question 34

What happens to blood vessels when too hot?

Answer 34

Vasodilation causing blood to be diverted to extremities to cause heat loss.

Question 35

What happens to blood vessels when too cold?

Answer 35

Vasoconstriction diverts blood away from extremities to stop heat loss which can cause frostbite in extreme conditions.

Question 36

What are the advantages of endotherms?

Answer 36

- Body temperature fairly constant despite external temperature - Can take advantage of prey - Can inhabit colder places

Question 37

What are the disadvantages of endotherms?

Answer 37

- Need constant supply of food to regulate body temperature - Most nutrients and energy from food used for growth. - Can overheat in hot places