B1.2 Responses To A Changing Environment Flashcards
What is homeostasis?
Keeping a constant internal environment.
What is thermoregulation?
Maintaining a constant internal body temperature.
What is osmoregulation?
The maintenance of water content in the body.
What part of the brain monitors body heat?
The hypothalamus.
What methods does the body use to cool you down?
Sweating
Relaxing the erector muscle so that body hair lies flat.
Making blood flow through blood vessels closer to the surface.
What methods does your body use to warm you up?
Moving your muscles
Making your blood flow through deeper blood vessels.
What is vasoconstriction?
When the body narrows the blood vessels closest to the surface.
What is vasodilation?
When the body narrows the blood vessels furthest from the surface.
What is negative feedback?
When one thing happens, it is made to go the opposite way eg thermoregulation.
What is a stimulus?
Something that the body can detect?
What detects a stimulus?
Receptor cells.
What is an electrical impulse?
An electrical signal sends messages around the body.
What is a hormone?
Chemical messengers which travel in the blood to activate target cells.
What features does a neurone have to help the electrical impulse travel quickly?
It is very long- the impulse travels fastest in a neurone
It has a myelin sheath- this is a fatty insulator that speeds it up.
What is a synapse?
A gap between two neurones. They impulse releases a chemical which diffuses across the gap to set off a new electrical impulse.
What are the differences between hormones and nerves?
Hormones: Slow message Act for a long time Act in a general way Chemical message
Impulses: Very fast message Act for a very short time Act on a very precise area Electrical message.
What are dendrons?
Branched endings of neurones so that they can connect to lots of other neurones.
What are the five receptor organs and what receptors do they contain?
Eyes- contains light receptors
Ears- sound and balance receptors
Nose- smell receptors- sensitive to chemical stimuli
Tongue- taste receptors
Skin- pressure and temperature change receptors.ŵ
What are sensory neurones?
Long dendrons and short axons that carry impulses from the receptor cells to the CNS.
What are relay neurones?
They carry nerve impulses from the sensory neurones to the motor neurone. They are short dendrons and axons.
What are motor neurones?
They are many short dendrons and one long axon that carry nerve impulses from the CNS to the effectors.
What are effectors?
Things that carry out the effect eg muscles or glands.
How does the CNS coordinate a response, from start to finish?
- A stimulus is detected by receptors, and the information is sent as an impulse along a sensory neurone to the CNS.
- The CNS coordinates the response (decides what to do about it and tells something what to do).
- The CNS sends information to an effectors along a motor neurone.
The effector acts accordingly.
What is a reflex?
An automatic response to certain stimuli that help reduce the chances of injury.
How does a reflex arc work, from start to finish?
- Stimulus is detected by receptor cells. The information is passed along a sensory neurone as an impulse.
- A relay neurone relays it to the motor neurone which takes it to the effector.
Why are reflexes quicker than normal responses?
They do not go through the CNS so the brain doesn’t think about it as the thinking takes time.
How are glucose, glycogen and glucagon all linked to blood glucose levels?
When blood glucose levels are too high, the pancreas secretes insulin, which causes the liver to turn glucose into glycogen.
When blood glucose levels are too low, the pancreas secretes glucagon, which causes the liver to turn glycogen into glucose.
What is type 1 diabetes and how is it treated?
Type 1 diabetes is caused by the pancreas not secreting enough insulin. Treatments include:
Limiting the intake of foods rich in simple carbohydrates
Insulin therapy where insulin is injected.
What is type 2 diabetes and how is it treated?
It is cause by the body becoming resistant to insulin and where the body doesn’t respond. Treatments include:
Eating a healthy diet
Getting regular excersise
Losing weight (if needed)
What is a tropism?
A plants response to stimuli eg light, gravity or moisture.
What is phototropism?
The growth of a plant is response to light. Shoots are positively phototropic- they grow towards light.
What is gravitropism (or geotropism)?
The growth of a plant in response to gravity. Roots are positively gravitropic- they grow downwards.
What is auxin?
A plant hormone that controls growth at the tips of shoots and roots.
How does auxin promote growth in the shoot of a plant?
When a shoot tip is exposed to light, more auxin accumulates on the shady side. This makes the cells elongate faster on the shady side, so the shoot bends towards the light.
How does auxin promote geotropic growth in a root?
When a root is growing sideways, gravity produces an unequal distribution of auxin. The auxin inhibits growth so the cells on top elongate faster, so the root bends downwards.
What is gibberellin?
A plant growth hormone that stimulates seed germination, stem growth and flowering.
What are the commercial uses of plant hormones?
Selective weedkillers
Growing from cuttings
Controlling the ripening of fruit
Producing seedless fruit
How are plant growth hormones used as selective weedkillers?
Only broad leaved plants are affected by the weedkiller (like weeds). The weedkiller disrupts their normal growth patterns, which kills them.
How is rooting powder used to grow plants from cuttings?
Rooting powder contains a plant growth hormone which makes it produce roots rapidly.
How are hormones used in controlling the ripening of fruit?
Ripening hormone is added to picked fruit, making it ripe once it reaches the supermarket.
How is seedless fruit produced?
If plant growth hormones are added to fruit, the fruit grows whilst seeds don’t.
