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B1 Topic 2 ­ Responding to change
Homeostasis

Conditions in our body need to be maintained and controlled so cells can function properly. For example:
o Osmoregulation: This is the regulation of water content. A balance needs to be kept between water
gained and water lost.
o Thermoregulation: This is…

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Features of neurones:

Dendrons & Dendrites Fine cytoplasmic extensions They create junctions with
from the cell body. Dendrites other neurones.
extend from Dendrons.
Axon A fibre which is longer than any
These carry impulses along to
other extensions of the cell the effector organ. It does this
body. by forming…

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Muscles contract in response to a nervous impulse whereas glands secrete substances as a response.



Sensory neurones

Long Dendrons and short axons carry nerve impulses from the receptors in the sense organs to the CNS.

Motor Neurones

Many short dendrons and one long axon to carry nerve impulses from the…

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1. The neurones in the reflex arc go through the spinal cord or through an unconscious part of the brain (you
don't have to think).
2. When a stimulus (e.g. pin) is detected by the receptors, impulses are sent along a sensory neurone to the
CNS.
3. In the CNS…

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This occurs often with overweight or obesity. This condition is where the pancreas doesn't produce enough
insulin or when a person becomes resistant to insulin (their body cells don't respond properly).
In both of these cases blood sugar levels can rise to a dangerous level.
Obese people have an increased…

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Other plant hormones

Cytokinins ­ induces mitosis (causes plants to grow and flower and stimulates seed germination).
Ethylene ­ Ripening of fruit and dropping of leaves.
Abscisic Acid ­ inhibits growth during winter so plants can hibernate and not waste energy

Uses of plant hormones

Selective weedkillers

Artificial auxin is…

Comments

Isaacbam

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very useful sums up topic 2 very well thanks

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