5.1 - C - Communication And Homestasis Flashcards
Define cell signalling
The way in which cells communicate with each other
What does cell metabolism rely on?
Enzymes
List the set of conditions in cells that all living things need to maintain
A suitable temperature
A suitable pH
An aqueous environment that keeps the substrates and products in solution
Freedom from toxins and excess inhibitors
What does an external environment consist of?
Air
Water
Soil
What is the composition of the tissue fluid maintained by?
The blood
What will a good communication system do?
Cover the whole body
Enable cells to communicate with each other
Enable specific communication
Enable rapid communication
Enable both short-term and long-term responses
What are the 2 major systems of communication that work by cell signalling?
Neuronal system
Hormonal system
What is a receptor?
A cell that detects a stimulus and creates action potentials (nervous impulse)
What is an effector?
A cell, tissue or organ that brings about a response
What is a stimulus?
A change in an environment that causes a response
What is a response?
A change in behaviour/physiology as a results of a stimulus
What is an internal environment?
The conditions inside an organism
What is an external environment?
The conditions outside an organism
Why do 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?
Some products of metabolic activities are harmful ‐ their build up
could be toxic ‐ they act as a stimulus for their own removal.
Maintains constant internal conditions (homeostasis)
What is the importance of organisms being able to respond to the
external environment?
To be able to adjust internal environment in response to external
e.g. temperature
To adapt to changes in environment e.g. weather or scenery (camouflage)
Find resources e.g. tropisms
Compare the neuronal system and the hormone system
H: slower response to stimuli N: faster response to stimuli H: hormones carried in blood N: electrical impulses carried by neurones, neurotransmitters carry message across synapse H: longer term responses N: short term responses H: hormones are specific to target N: cells but can have quite a general effect
Define homeostasis
The maintenance of the internal environment in a constant state despite changes to internal and external environments
Define negative feedback
A process that brings about a reversal of any change in conditions in order to return to an optimum set point. This is essential for homeostasis.
Define 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)
List 6 aspects maintained by homeostasis
Body temperature Blood glucose concentration Blood salt concentration Water potential of the blood Blood pressure Carbon dioxide concentration
What has to happen to bring about any form of homeostasis?
Receptor detects stimulus ‐‐> cell signalling ‐‐> effector brings about response
Explain the cycle (steps) in negative feedback
Optimum conditions, Change from optimum, Receptor detects change, Communication system informs effector (cell signalling), Effector reacts to reverse change, Return to optimum condition, Repeat
Explain the cycle (steps) in positive feedback
Optimum condition, Change away from the optimum, Receptor detects change, Communication system informs effector, Effector reacts to increase change, Repeat back to step 2
What 3 processes must occur for negative feedback to work
A change to the internal environment must be detected
The change must be signalled to other cells
There must be an effective response that reverses the change in conditions
Define metabolic waste
Waste substances that may be toxic or are produced in excess by the reactions inside cells
What is an ectotherm?
An organism that relies on external sources of heat to regulate body temperature
What is an 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?
Temperature will affect rate of metabolic reactions
Cooler temperatures ‐ reactions would slow down
Too hot ‐ enzymes would denature ‐ stop metabolic reactions
Evaluate ectothermy
\+ less food used in respiration \+ need less food \+ more energy used for growth \+ they can survive for long periods without food - less active in cold - winter months
Evaluate endothermy
+ can maintain constant body temp despite external conditions
+ can be active in colder conditions
+ remain active even when external temperatures are low, which means they can take advantage of prey that may be available or escape from potential predators
- a large portion of energy intake is needed to maintain body temperature
in cold
- more food required
- less energy from food used for growth
- may overheat in hot weather
What does the hypothalamus do?
Coordinates homeostatic responses
What is the hypothalamus an example of and why?
Negative feedback
It 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.
What do peripheral thermoreceptors do?
Where are they found?
In the skin
They 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.
List 4 behavioural adaptations used by endothermic to maintain body temperature
Hide away from/ lie in the sun
Wet/lick skin/ spray water over themselves, remain dry
Remain inactive/move to generate heat
Reduce/increased body surface area exposed to the sun
How does skin respond if the organism is too hot/cold?
More/less swear
Hairs feathers lie flat when hot, stand when cold (insulation)
Vasodilation of arteriolar and precapillary sphincters directs blood to skin surface so more heat can be radiated away from the body / vasoconstriction - opposite of above - less heat lost
How do gaseous exchange systems respond if the organism is too hot/cold?
Some animals pant, increasing evaporation from lung and airways surfaces.
Less panting, less heat lost
How does the liver respond if the organism is too hot/cold?
Less respiration takes place so less heat is released.
Or
Increased respiration in the liver cells means that more energy from food is converted to heat.
How do skeletal muscles respond if the organism is too hot/cold?
Fewer contractions mean that less heat is released.
Or
Spontaneous muscle contractions (shivering) release heat.
How do blood vessels respond if the organism is too hot/cold?
Dilation to direct blood to the extremities so that more heat can be lost.
Or
Constriction to limit blood flow to the extremities, so that blood is not cooled too much - this can lead to frostbite in extreme conditions.
