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 to regulate their internal body temp. Mostly physiological methods; respiration and vasodilation/constriction. Also some behavioural (wrapping up warm).

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.