Topic 2 - Responding To Change Flashcards
What is Homeostasis?
It is maintaining a stable internal environment
What is osmoregulation?
Is the control of the amount of water in the body. An example of homeostasis.
How is body temperature controlled?
By the hypothalamus
Osmoregulation : If there is too much water in your body what happens?
- Sweat is produced by sweat glands
- The kidneys produce more urine
Osmoregulation: If there is not enough water in your body what happens?
- Your brain makes you feel thirsy
- The kidensy produce less urine
What is thermoregulation?
- Is the control of the temperature of the body
- An example of homeostasis
- Hypothalamus in the brain monitors ksin temp. from receptor cells
Why is it important to maintain body temperature?
Enzymes work best at 37 degrees celsius. If the body temperature is dramatically above or below that then enzymes will not work and you die.
What is the hypothalamus?
It is the part of the brain that regulate body temperature
What happens when temperature receptors detect your too cold?
- Shiver muscles generate heat when they make energy
- Erector muscles contract pulling hair up, trapping a layer if air
- Very little sweat produced from glands
- Blood vessels near the surface of the skin constrict (vasoconstriction)
- Less blood less heat
What happens when we receptor cells detect you’re too hot ?
- Erector muscles relax, hairs lie flat
- Lots of sweat cools down
- Blood vessels close to the surface dialate to allow more blood to flow (vasodilation)
- Skin looks redder
What is negative feedback?
When there is a change to the conditions in your body negative feedback changes these back to normal and keeps them steady.
If the environment chnages too much then it might not be possible to counteract it.
What is a hormone?
- Chemical messengers sent in the blood to activate traget cells
- Long lasting effects
- traget cells in target organ
What is a neurone?
- Transmit information as electrical impulses around the body
- Dendrons which connect with other neurones
- electrical impulse passed along the axon
- myelin sheath prtecting the axon
- synapse whcih is the gasp between two neurones.
What are effectors ?
Muscles and glands and known as effective- they respond in different ways Muscles contract in response to a nervous impulse whereas glands secrete substances for example hormones
What are neurones and what do they do?
Neurones transmit information around the body as Electrical impulses
What is myelin sheath?
- Surrounds the axon
- a fatty layer that insulates the neurone from surrounding tissue
- allows impulses to travel faster and not get lost
What is a synapse?
- A gap between two neurones
- make sure the impulses only travel in one direction
- impulses cause neurotransmitters (chemicals) to be released at the axon endings
- neurotransmitters diffuse across the synapse
- they fit into the receptors on the next nuerone
- this triggers an impulse to start in the next synapse
What are the differences between nerves and hormones?
Nerves
- Very fast message
- act for a short time
- act on a precise area
- electrical message
Hormones
- Slower message
- act for a long time
- act in a general way
- chemical message
What is a stimulus and how is it detected?
- A change in your environment that you need to react to
- Sense organs detect stimuli
What are the three types of neurones?
- sensory neurone
- relay neurone
- motor neurone
What is a Motor neurone ?
- Recieve impulses from relay neurones and carry impulses to effectors (muslce/glands)
- causes a response e.g. muscle contracting
- No dendron but has dendrites on the cell body

What is a sensory neurone?
- Long Dendrons
- Short axons carrying nerve impulses from the receptors in the sense organs to the central nervous system
- Receptors detect changes in the environment (stimuli)

What is a relay neurone?
- short neurones which link sensory and motor neurones
- many dendrites to allow nerve impulses to pass from other neurones
What is a reflex arc?
- caused by quick reactions to pull us away from a dangerous stimuli
- They just go to the spinal cord not the brain
- Receptor cells detect stimulus
- They trigger an impulse to travel down a sensory neurone to the spinal cord
- The impulse crosses a synapse to a relay neurone
- The message travels along a motor neurone
- The message reaches the effector e.g. muscle
- This causes a response e.g. muscle contracts