B1 topic 2 responding to change

B1 topic 2 responding to change

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Homeostasis means maintaing the right conditions inside your body so that evrything works properly.

osmoregulation (regulat water content)you need to keep a blaence between the waster you drink and eat and the water you pee out and sweat.

Themoregulation (regulating body temp) you need to get rid of excess body heat when you are hot but retain heat when you in a cold enviroment.

blood glucose regulation- you need to keep your glucose at a steady level.



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Body temp is controlled by hypothalamus

all enzymes wrok best in a cirten temp body enzymes work best in body temp (37*c)a thing in you brain called hypothalamus is like a personall thermostat.

it contaibn receptors that are sensitive to the temp of the blood in your brain also it recives impulses from the skin that provide info about the skin  temp when the hypothalamus detects a change it causes response in the dermis (deep layer of skin)

when it detects your to hot:

erector mucels relax so hairs lie flat. lots of sweat is produced when the sweat is evaporated it tranfers heat from you skin into the enviroment.blood vessels near the surface widen so that it more blood flows near the surface with tranfers more heat into the suroundings.


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Your to cold:

erector muscles extract witch makes hair stand up on end to trap an insulating layer of air witch helps you to keep worm, very little sweat is produced and your blood vessels near the surface constrickt this means less blood can flow near the surface of your skin witch makes less heat get transferd into the suroundings.

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Hormones and nerves

Hormones are chemical messengers sent in the blood

hormones are chemicals produces in various glands they are released directly into the blood and travel to other parts of the body. they travel all over the body but only affect some cells in particular places. the affected cells are called target cells they have the right receptors to respond to that hormone. hormones travel at the speed of blood and they have long lasting effects.

Neurones transmit info around the body

neurones transmit info as a electrical impulse around the body

neurones have branched ends called dendrones so they can connect with lots of other neurones.the electrical impulse is passed along the axon of the cell. Theres a myelin sheath along the axon cell that acts like a eletrical insulator, witch stops the impulse getting lost and it speeds it up.


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Hormones and nerves

neurones are long so it makes them faster one long nueron is faster than lots of little ones joined up. the gap between two nurones is called a synapes.

Hormones and nerves do similar jobs- but there are differences:


very fast message

act for very short time

act on a very precise area

electrical message



slower message

act for long time

act in a more genral way

chemical message

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insulin and glucagon control blood sugar level!

Insulin and glucagon control blood sugar level:

Eating foods that contain carbs put glucose into the blood from the gut. The normal metabmolism of cells remove glucose from the blood. exercise can remove much more glucose from the blood.To control the level of blood glucose there has to be a way to add or remove glucose from the blood

Blood glucose to high: Insulin added     Blood glucose to low: glucagon is added




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insulin and diabetes

Type 1 diabetes- caused by lack of insulin.

Type 1 diabetes is when the pancreas produces little or no insulin. this mean a person with type 1 diabetes had to inject insulin. the amount of insulin depends on the persons deit the amount of exsersize and the size of the person. doing regular excersize decreases the amount of insulin the person would have to inject.

Type 2 diabetes- a person is resistant to insulin

type 2 diabetes is when a person becomes resistantto insulin or they dont produce anoff. obeas people have a high risk of type 2 diabetes. type 2 diabetes can be controlled by a healthy diet, exsersize and loosing weight if need to also some people with type 2 can be gave medication or insulin injections.

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Plant growth hormones

Plants respond to different Stimuli

plants can respond to stimuli (light,gravity and moisture)

A plants growth response is called a tropism. a positive tropism is growing towards a stimulus.


Phototropism- the groth of a plant responding to light. shoots are positivly phototrophic- they grow towards the light.

Gravitropism- the growth of a plant in response to gravity roots are positivly gravitropic- then grow downwards.

 Plant growth hormones such as auxin and gibberellin, allow plants to grow in response to stimuli.

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Plant growth hormones.

Axin stimulates plant tips to grow:

auxin is a plant hormone that contorls growth at the tips of shoots and roots.

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