Module 5: Communication And Homeostasis Flashcards
Why do plants and animals need communication systems?
Plants and animals need communication systems in order to respond to both internal and external environments and coordinate the activities of organs.
What is the importance of organisms being able to respond to their internal environment?
1) Some waste products of metabolic activities are harmful- Their build up could be toxic- They act as a stimulus for their own removal.
2) Maintains constant internal conditions (homeostasis)
What is the importance of organisms being able to respond to their external environment?
1) To be able to adjust internal environment in response to external environment. E.g. temperature.
2) To adapt to changes in the environment. E.g. Weather.
3) Find resources. E.g. Tropism
Coordinating the activities of organs
Receptors and effectors may not be next to each other in the body. This means they must communicate specific messages across the whole body quickly over both short and longer term periods.
Cell signalling is how the cells communicate with one another.
What is cell signalling?
Communication between cells to help them work
together to co‐ordinate their actions.
Cell signalling is how the cells communicate with one another.
Two types of cell signalling
Neuronal systems ‐ neurones signal to each other across synapses.
Hormonal systems ‐ hormones are transported in the blood to specific target cells.
Compare the way the two cell signalling systems act
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Homeostasis
The maintenance of the internal environment in a
constant state despite internal and external changes.
Positive feedback
A process that increases any change detected by the receptors, taking the conditions further from the optimum set point. (Tends to be harmful and does not lead to homeostasis).
Negative feedback
A process that brings about a reversal of any change in conditions in order to return to an optimum set point- Essential for homeostasis.
How does homeostasis take place?
Receptor detects stimulus ‐‐> cell signalling ‐‐> effector brings about response
Explain what homeostasis is and why it is necessary and how it is maintained (5).
Homeostasis is the maintenance of the internal environment in a constant state despite internal and external changes.
It is vital to keep conditions such as body temperature, blood glucose conc. and blood pressure the same.
It is maintained through cell signalling to cause negative feedback.
For each of the examples below, state if it is an example of positive or negative feedback.
- During childbirth ‐ as the cervix stretches, oxytocin is released which increases contractions and increases cervical stretching.
- Milk production ‐ as long as baby is nursing, milk will be produced.
- High concentration of CO2 in blood leads to increase in heart rate and breathing rate.
Receptor
A cell that detects a stimulus and creates action potentials (nervous impulse).
Effector
A cell, tissue or organ that brings about a response.
Stimulus
A change in an environment that causes a response.
Response
A change in behaviour/physiology as a results of a stimulus.
Internal environment
The conditions inside an organism.
External environment
The conditions outside an organism.
Ectotherm
An organism that relies on external sources of heat to regulate body temperature.
Endotherm
An organism that can control the generation or loss of heat to maintain its body temperature using physiological or behavioural responses.
Why do organisms need to control their body temperatures? (2)
- temperature will affect rate of metabolic reactions.
- cooler temperatures ‐ reactions would slow down.
- too hot ‐ enzymes would denature ‐ stop metabolic reactions.
What are the advantages and disadvantages of being an
ectotherm?
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What are the advantages and disadvantages of being an
endotherm?
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Behavioural mechanisms in maintaining body temperature
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Thermoregulation- temperature control
The hypothalamus monitors the blood temperature and if it moves away from the optimum core temperature, it will send signals to bring about the reverse of the changes.
Peripheral thermoreceptors in the skin sense changes of temperature in the external environment. It too much change is detected this information is sent to the hypothalamus which brings about the relevant responses.
Physiological mechanisms in maintaining body temperature
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Explain how endotherms control their body temperature when they are too hot. [6]
• peripheral thermoreceptors in skin
• stimulated by change in external temp
• impulses sent to
• hypothalamus
• vasodilation of arterioles to increase heat loss
• by radiation / conduction
• decreased metabolic rate / respiration in liver
• to generate less heat
• sweating/panting ‐ evaporation to remove heat
from skin
• hair muscles (effectors) cause hairs to lie flat ‐ not
insulating air trapped ‐ heat can radiate easier
Explain how endotherms control their body temperature when they are too cold [6]
• vasoconstriction of arterioles to reduce heat loss
• by radiation / conduction
• increased , metabolic rate/ respiration in liver
• to generate heat (energy) ;
• release of adrenaline
• rapid contraction/relaxation of sketetal muscles to
shiver to generate heat (energy) ;
• hair muscles (effectors) cause hairs to cause hairs to
stand up ‐ trap a layer of insulating air to prevent heat
loss by conduction
• peripheral thermoreceptors in skin
• stimulated by change in external temp
• impulses sent to
• hypothalamus
