5.1.1 Communication And Homeostasis Flashcards
(43 cards)
Why do multicellular organisms need communication systems
Animals and plants need to respond to changes in their internal and external environment
Also need to coordinate the activities of different organs
Why do we need to keep our water potential constant
If our blood has lower WP than tissue fluid water moves into blood by osmosis- the tissues dehydrate
Why do we need to keep our pH constant
pH affects amount of H+ ions- causes 3D structure of enzyme to change, active site changes, fewer ESC
Define stimulus
A change in internal or external environment that causes a response
What is a response
A change in behaviour or physiology due to a stimulus
Define cell signaling
Communication between cells that allows cells to work together to trigger a response or a reaction inside the cell
What is hormone cell signaling
Involves hormone released into the blood that binds only to specific target cells with matching receptors
What is homeostasis
Maintenance of a a stable internal environment within a narrow range despite external environment changes so that enzymes can function optimally
What is negative feedback
Corrective homeostatic mechanism that works to restore any detected change in the internal environment to optimum state
Give an example of negative feedback
Vasodilation
Sweating
= cool body
What is positive feedback
A process that increase any change detected by receptor
Taking it further away from a set point
Give a positive example of positive feedback
Oxytocin- as cervix stretches during labour
Ethylene gas in fruit
Explain how hypothermia is an example of positive feedback
1) person is cold
2) enzyme slow down (less kinetic energy)
3) less metabolic reaction
4) less energy produced
5) less heat
6) person gets colder
7) enzymes slow further
…
What is an endotherm
An animal that can regulate and maintain core body temperature
They generate heat from respiration and metabolism
Evaluate the pros and cons of being an endotherm
Advantages:
- constant body temp independent of external temp
- organism can be active despite external conditions
- can live in colder environments
Disadvantages:
- large energy intake
- less food used in growth
How do we as humans loose heat
Radiation to the environment
Evaporation of water to vapour
Convection of heat into air currents
Conduction of heat through skin
What part of the brain is responsible for monitoring blood temp
Thermoregulatory centre
In the area of the hypothalamus
What are the two centres that are activated in response to a change in temp
Heat gain centre- activated by a fall in blood temp
Heat loss centre- activated by a rise in blood temp
Describe the two sets of receptors involved in detecting heat
Thermoreceptors in the hypothalamus measure blood temp
Peripheral thermorecpetors in the skin monitor external temp - send impulses to the hypothalamus
What happens if your body temperature decreases
Heat gain centre activated by a fall in blood temp
This is detected by receptors in the hypothalamus and peripheral thermoreceptors in the skin
Name three methods of conserving heat
Physiological:
- vasoconstriction
- raising of hair
Behavioural:
- shelter from wind
- animals huddle together
How does the raising of hair cause the body to conserve heat
Erector muscles in the skin contract raising hair to trap a layer of insulating air to trap heat and reduce the cooling of skin
How does vasoconstriction conserve heat
Decrease of arterioles lumen to reduce blood flow to the capillaries in the skin of the organisms- reducing heat loss by radiation
3 ways heat is lost from the skin
Conduction
Convection
Radiation
