-Module 5.1.1 - Communication and Homeostasis

Question 1

What is needed for a response to be made?

Answer 1

A stimulus.

Question 2

What are some examples of internal stimuli that can be monitored in plants and animals?

Answer 2

Build up of toxins.
Change in pH.
Blood pressure.
Changes in temp.

Question 3

What is a stimulus?

Answer 3

An environmental change.

Question 4

What is a response?

Answer 4

The change in an organism’s behaviour or physiology.

Question 5

Why do we need communication systems?

Answer 5

We need to respond to what is going on internally and externally to survive.
They ensure info is passed from one part of the organism to another part.

Question 6

Why are communication systems so important for MULTICELLULAR organisms?

Answer 6

They have different cells which perform specialised functions.
One cell monitors and another responds.
Cells have to communicate over long distances.
Organ systems must coordinate responses.

Question 7

How do plants monitor and respond to the internal and external environments?

Answer 7

They are controlled by plant hormones. (Eg auxins in phototropism)

Question 8

What are the two communication systems that we have in our body?

Answer 8

Neuronal and endocrine.

Question 9

What is the signal type, speed of signal and duration of signal in the neuronal system?

Answer 9

Electrical.
Rapid (milliseconds)
Short lasting

Question 10

What is the process of cell signalling in there hormonal system?

Answer 10

Cells in the endocrine system release their signals (hormones) into the blood. This signal is only recognised by target cells. This is a longer-term response.

Question 11

What is the process of cell signalling in the neuronal system?

Answer 11

An interconnected network of neurones signal to each other across synapse junctions - this is a rapid response to stimuli.

Question 12

What is the name for the specific shape that signalling chemicals have to receptors on the target cell?

Answer 12

Complementary shape.

Question 13

What is the definition of homeostasis?

Answer 13

The maintenance of an organism’s internal environment within set limits, despite changes in internal and external factors.

Question 14

What are 6 conditions maintained by homeostasis?

Answer 14

Body temp
Blood glucose conc
Blood salt conc
Water potential of blood
Blood pressure
C02 conc

Question 15

What are 6 conditions maintained by homeostasis?

Answer 15

Body temp
Blood glucose conc
Blood salt conc
Water potential of blood
Blood pressure
C02 conc

Question 16

What is the standard response pathway?

Answer 16

Stimulus -> receptor -> communication pathway (cell signalling) -> effector -> response

Question 17

What are the function of sensory receptors?

Answer 17

Monitor changes in internal and external environments. Eg temp in skin (external) and the brain (internal)

Question 18

What is a communication pathway?

Answer 18

It is either neuronal or hormonal, and it’s function is to transmit signals from receptor cells to effector cells, via a coordination centre (brain).

Question 19

What is input?

Answer 19

Messages/signals sent from receptors to coordination centres.

Question 20

What is output?

Answer 20

Messages/signals sent from coordination centres to effectors.

Question 21

What do effector cells do?

Answer 21

They bring about a response like a muscle cell contracting.

Question 22

What does negative feedback do?

Answer 22

It works to return conditions back to the optimum whenever they deviate from the normal.

Question 23

How does negative feedback work?

Answer 23

Receptors detect when a level is too high or too low, this info is communicated via neurons or hormones to the effectors to bring the level back to the optimum.

Question 24

What does a diagram of negative feedback look like?

Answer 24

      ----------         -------

Question 25

When may negative feedback be unable to counteract a change?

Answer 25

If the change is too big, eg if the body temp drops rapidly due to exposure to cold weather.

Question 26

What does positive feedback do?

Answer 26

It amplifies the change. The effectors respond to further increase the level away from the normal level.

For example in childbirth the hormone oxytocin stimulates uterine contractions, the contractions trigger positive feedback for more oxytocin.

Question 27

What are ectotherms?

Answer 27

They are not able to control their body temperature and they rely on external sources of heat. This means their temperature fluctuates with the external temperature, They use behavioural methods to control body temp.

Question 28

What are endotherms?

Answer 28

They use heat that is generated internally from metabolic processes to regulate their internal body temp. Mostly physiological methods; respiration and vasodilation/constriction. Also some behavioural (wrapping up warm or hibernation).

Question 29

What are the behavioural responses of an ectotherm to regulate temperature?

Answer 29

Lie directly in the sun, maximising surface area exposed.
Lying on a warm surface.
Quickly raise body temp in the morning.
Once active, muscle contractions generate heat from resp.
Use (burrows) shelter to escape extremes.

Question 30

What are the advantages of not controlling your body temperature physiologically?

Answer 30

Less food used in respiration to release energy.
More energy gained from food used for growth.
Need to find less food.
Survive longer w.out food.

Question 31

What are the disadvantages of not controlling your body temperature physiologically?

Answer 31

Less active in cooler temps.
At risk from preds at cooler temp.
Cannot take advantage of food available when they’re cold.

Question 32

Why is controlling body temp important?

Answer 32

Changes in temp can affect activity of cell processes.
When temps rise, molecules have more kinetic energy, so they collide more frequently.
Chemical reactions occur more rapidly.
Enzyme action affected, active site denatured.
Core temp most important as vital organs are at the centre.

Question 33

What is the role of the hypothalamus?

Answer 33

It responds to action potentials from the receptors, by sending out action potentials to effectors.

Question 34

Where are the effectors that the hypothalamus sends out action potentials to?

Answer 34

The skin, muscles, blood vessels and liver.

Question 35

What are receptors?

Answer 35

They monitor the external environment, aka peripheral receptors.

Question 36

How does the skin regulate temperature?

Answer 36

Sweating, when the body is too hot sweat is secreted from the sweat glands.
The sweat evaporates from the skin’s surface and carries heat away from the body.

Question 37

What are erector pili muscles?

Answer 37

They contract to make the hair stand up or relax to make them flat.

Question 38

How can capillaries be used to control body temperature?

Answer 38

Many capillaries are in the skin.
Arterioles that supply the capillaries can constrict or relax, affecting the amount of blood flowing through the capillaries.

Question 39

What are the steps in thermoregulation for an increase in peripheral temperature?

Answer 39

Thermoreceptors in the dermis detect the increase in peripheral temperature.
They initiate an action potential that travels along a sensory neurone to the hypothalamus.
The hypothalamus monitors both the peripheral and core temperatures.
The core temperature is monitored by thermoreceptors in the hypothalamus’ blood supply.
The hypothalamus sends an action potential back to the skin via a motor neurone.
The action potential causes the glands to secrete sweat, they also cause vasodilation.

Question 40

How do the skeletal muscles and the liver respond to maintain body temperature?

Answer 40

Skeletal muscles contract (shivering) to release heat.
Liver can increase or decrease it’s rate of respiration to increase or decrease the energy from food that is converted to heat.

Question 41

What is the function of panting in animals?

Answer 41

Some animals pant to increase evaporation of water from the surface of the lungs and airways.
In cold weather, they pant less and so less heat is lost.

Question 42

What are the advantages of being an endotherm?

Answer 42

Can maintain a fairly constant body temperature whatever the external temperature.
Can remain active even when temperatures are low.
Inhabit colder parts of the planet.

Question 43

What are the disadvantages of being an endotherm?

Answer 43

They use a significant part of their energy intake to maintain body temperature in the cold.
A lower proportion of the energy and nutrients gained from food is available for growth.
Need to eat more.
May overheat in summer.

Question 44

What behavioural responses can be used to increase body temperature?

Answer 44

Lie in the sun.
Orientate body so increased surface area is exposed to the sun.
Move about to generate heat in the muscles, or in extreme conditions, roll into a ball shape to reduce surface area and heat loss.
Remain dry.

Question 45

What behavioural responses can be used to decrease body temperature?

Answer 45

Hide away in a burrow or in the shade.
Orientate body to reduce surface area exposed to sun.
Remain inactive and spread limbs out to allow greater heat loss.
Wet skin.

Question 46

What is an example of cell signalling?

Answer 46

Cytokines as a part of the immune response.
Produced by mast cells in damaged tissues that attract phagocytes to the site of infection or inflammation.