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Homeostasis: the maintenance of a stable internal environment within an organism.

Homeostasis has 2 main categories:

Behavioural homeostasis: behaviour to aid survival

Internal homeostasis (usually referred to as just homeostasis): usually a negative feedback loop
including neurons or hormones to maintain a stable internal environment.

Examples of homeostasis include;…

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Originating from either the coordinator or the receptor an electrical impulse will travel down the
axon when the positive ions rush back across the membrane to initiate an action potential.

What happens at the receptor?

Receptors are modified dendrites and with sufficient stimulus will open Na+ channels. This causes the…

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Many drugs such as pain killing drugs affect the synapse. This is because they act like
neurotransmitters and compete with the actual neurotransmitters for the receptors, or the enzyme
of the synapse that is responsible for the breaking down of the neurotransmitters.


Temporal summation is where several action potentials…

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Neuromuscular function...

To enable muscle contraction an action potential travels along a motor neurone to the muscle; here a
synapse is crossed like at a nerve junction (at the axon terminals). These are called motor end plates.
There are many neuromuscular functions on each muscle, the more neuromuscular junctions are…

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In environments significantly colder than our body temperature we tend to wrap up warmly to
prevent radiative heat losses from our skin or by cold winds via convection.

Animals that live in extreme cold have natural insulation in the form of blubber while animals who live
in extreme heat tend…

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Cell signalling has 2 types:

1. Local Signalling which includes paracine signalling and synaptic signalling.

2. Long Distance Signalling (hormonal) includes endocrine signalling.

Antigenic Communication is where antigens on the cells are recognised as self by white blood cells.
This leads to problems with transplant patients as the white blood…

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Heart rate increase.
Conversion of glycogen to glucose to be stimulated.
Dilute the pupils.

How does it work?

1. Adrenaline binds with its specific receptor on the target cell which has enzymes attached
to it on the intracellular side.
2. This then activates the enzymes and so adrenaline is known…

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Insulin is an example of negative feedback and without these homeostatic feedback loops blood
glucose would swing between highs and lows depending on our feeding patterns.

The problems with diabetes are; that the retina can be affected and glucose changes the viscosity of
the blood.

After a meal the digestive…

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Its effects on the cell are:

It increases the cell's permeability to glucose as protein channels rise into the membrane.
Adenyl cyclise is activated.
cAMP activates enzyme controlled reactions.
Glycogenesis occurs as glucose is converted to glycogen.
Some glucose is converted into fat.
More glucose is used in respiration.


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Obesity is a risk factor for type II diabetes as the non-receptitiveness to insulin means that
injections will become pointless.
A diet high in levels of sugar.
Family history

The production of insulin:

In the past we have relied on pig insulin, this caused problems for religious ground on…


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