5.1 Communication and Homeostasis

Question 1

What is a stimulus?

Answer 1

A change in the environment of an organism that brings about a change.

Question 2

What is a response?

Answer 2

The way an organism changes it’s physiology or behaviour as a result of the stimulus.

Question 3

What does an organism need in order to conduct a response to a stimulus?

Answer 3

Good communication systems.

Question 4

What are the two communication systems that work by cell signalling.

Answer 4

Neuronal System and Hormonal System

Question 5

Describe the Neuronal System.

Answer 5

An interconnected network of neurones that signal to each other across synapses.

Question 6

Are neuronal responses rapid or longer term?

Answer 6

Rapid

Question 7

Describe the Hormonal System.

Answer 7

A system that uses blood to transport hormone signals released in the endocrine system that are only recognised by specific target cells.

Question 8

Are hormonal responses rapid or longer term?

Answer 8

Longer Term

Question 9

What is an effector?

Answer 9

The cell or tissue that brings about a response (e.g muscle)

Question 10

Define Homeostasis.

Answer 10

Maintaining a constant internal environment despite external or internal changes.

Question 11

What are sensory receptors?

Answer 11

Cells or sensory nerve endings that respond to a stimulus.

Question 12

What is the standard response pathway for homeostasis?

Answer 12

Stimulus
Receptor
Cell Signalling (neuronal or hormonal)
Effector
Response

Question 13

What is negative feedback?

Answer 13

A mechanism that reverses a change and brings the system back to optimum conditions.

Question 14

Give 2 examples of negative feedback.

Answer 14

• temperature control

- blood sugar level control

Question 15

What is positive feedback?

Answer 15

A mechanism that increases a change and takes the system further away from the optimum.

Question 16

Give 2 examples of positive feedback.

Answer 16

• blood clotting

- giving birth (cervical dilation)

Question 17

What are endotherms?

Answer 17

Organisms that have to control their temperature within a strict limit despite changes in the external temperature

Question 18

What types of organisms are endotherms?

Answer 18

Mammals and Birds

Question 19

What are ectotherms?

Answer 19

Organisms that can’t control their temperature as effectively and rely on external sources of heat. As a result their body temperature can fluctuate with the external temperature.

Question 20

What types of organisms are ectotherms?

Answer 20

Reptiles and Fish

Question 21

What are the advantages of ectothermy?

Answer 21

No energy is spent on regulating temperature internally so they can go longer without food and energy can be used for other purposes.

Question 22

What are the disadvantages of ectothermy?

Answer 22

There have to be a lot of behavioural mechanisms to regulate temperature. Ectotherms also have less energy at colder temperatures putting them at more risk to predators.

Question 23

What are the advantages of endothermy?

Answer 23

Endotherms can inhabit habitats all around the world and can remain active despite low temperatures.

Question 24

What are the disadvantages of endothermy?

Answer 24

A lot of their energy is spent on temperature control so they have less energy for growth and need more food.

Question 25

What are some behavioural temperature regulations when too hot?

Answer 25

• hide away from the sun and position body so that less surface area is exposed to the sun
• remain inactive and spread limbs for greater heat loss

Question 26

What are some behavioural temperature regulations when too cold?

Answer 26

• lie in the sun and position body so that a greater surface area is exposed to the sun
• move around to generate heat and remain dry

Question 27

Where are the two different types of temperature receptors?

Answer 27

Temperature receptors in the hypothalamus and periphery temperature receptors in the skin.

Question 28

Describe the roll of the hypothalamus.

Answer 28

When temperature receptors in the hypothalamus pick up a temperature stimulus, they send impulses to cause responses.

Question 29

Which temperature receptors give earlier warnings?

Answer 29

Periphery temperature responses.

Question 30

Describe the ways in which the skin of endotherms can respond to changes in temperature.

Answer 30

When too hot, sweat glands secrete more fluid onto the skin which evaporates using heat from the blood to help the body cool down. Hair and fur also flattens to reduce insulation. When too cold, less sweat is produced and hair/ fur stands upright.

Question 31

Describe the ways in which the liver of endotherms can respond to changes in temperature.

Answer 31

When too hot, less respiration takes place so less heat is released. When too cold, more respiration takes place.

Question 32

Describe the ways in which the gas exchange systems of endotherms can respond to changes in temperature.

Answer 32

When too hot, more panting occurs which increases evaporation from the airways and lungs using the heat from the airways and lungs. When too cold, panting decreases.

Question 33

Describe the ways in which the blood vessels of endotherms can respond to changes in temperature.

Answer 33

When too hot, vasodilation widens the blood vessels and directs the blood towards the bodies surface where the heat from the blood can be lost. When too cold, vasoconstriction narrows the blood vessels and directs blood towards the centre of the body.