Homeostasis and Response



Homeostasis=regulation of conditions inside your body (+cells) to maintain stable internal environment, in response to changes in both internal+external conditions.

Is lots of automatic control systems in body that regulate your internal environment - these include nervous + hormonal communication systems: the conditions in your internal environment that need regulating include: body temp, blood glucose content, water content of body & sugar ions.

Negative Feedback - counteracting to maintain homeostasis=some variables triggers counteracting response=bringing it back to optimum/equilibrium

Positive Feedback - Intensifying variable instead of trying to maintain homeostasis=against

Type 1 Diabetes=negative feedback doesn't work properly.

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Negative/Positive Feedback

A change in your environment that you might need to respond to=stimulus (e.g light, sound, touch, pain/pressure, chemical)

Negative Feedback is when your body counteracts something happening in the body to maintain homeostasis. An example is when your in sun/heat & your internal temp increasing, so your body reacts by: sweating (lose heat), your veins dilate..

Positive Feedback is when your body intensifies/enhances the variable (change), is doesn;t try to keep balance & not very frequent. An example is when woman gives birth=increases pressure to increase contraction (to give birth).

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Adrenaline (hormonal) is extra burst of energy=makes muscles tense up + redistributes food to muscles (not stomach): it gives more energy so glucose+oxygen are helping us to respire more (lungs take in more oxygen), our hearts beat faster, b.p increases & this could happen before flight or fight.

Thyroxine produced in thyroid gland + regulates metabolic rate, heart + digestive function...

The hypothalamus secretes a hormone that stimulates pituitary gland, and this secretes hormone that causes thyroid gland to produce thyroxine.

Thyroxine=released with hormones & when these hormones increase=prevent release of inital hormones.

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Central Nervous System

Nervous system=communication system (humans made of trillion cells=need response) =helps to react to external stimuli

To detect things=receptors - detect stimuli (in eyes=detect line - rod/cone cells) (pressure receptors on skin - don't make up whole of skin)

Neurons - carry electrical impulses (when you touch something because of brain) 1st neuron=sensory (impulses carried receptors to CNS). 2nd neuron=other cells carried via motor neurons away from CNS. 3rd neuron=relay neuron=carries impulses to one to the other

CNS= co-ordination centre= Brain + Spinal cord --> will send electrical impulses to effector via motor neuron.

Effector=muscles=contract, allowing movement + glands=secrete chemicals (hormones)

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The connection between 2 neurones=synapse. The nerve signal transferred by chemicals which diffuse across the gap=chemicals then transfer back to electrical signal in next neurone. Neurones deliver info quickly because signal=transmitted by electrical impulses. Synapses slow down transmission of nervous impulse becuase diffusion of chemicals across gap takes time.


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Endocrine System

Hormones=chemical messengers which travel in blood to activate target cells. The speed of the message=slow + lasts for long time. Glands (pancreas, ovary, testis, pituitary, thyroid, adrenal)=release hormones. The endocrine system covers how hormones move around body. They're secreted by various glands & move through bloodstream to target organ.


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Controlling blood glucose levels

Throughout day blood glucose level varies:

  • eating foods containing carbohydrate puts glucose into blood from digestive system
  • normal metabolism of cells removes glucose from blood
  • vigorous exercise removes much more glucose from blood

Hormonal control of blood glucose - level of glucose in blood must be kept steady. Changes=monitored by pancreas=produces hormones which help to control blood glucose level.

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Controlling blood glucose levels...

Insulin=hormone produced by pancreas=decreases blood glucose level when it gets too high. Here's what happens: after meal containing carb persons blood glucose level rises=detected by pancreas. Pancreas responds by producing insulin=secreted into blood. Insulin causes body cells to take up more glucose from blood. Cells in liver + muscles can take up glucose & convert it into storage molecule called glycogen=causes glucose blood level to fall.

Glucagon another hormone produced by pancreas=increases blood glucose level when it gets too low. Here's what happens:

  • if person's blood glucose level decreases fall detected by pancreas
  • pancreas responds by producing glycogen=secreted in blood
  • glucose can be stored in muscle+liver as glycogen. Glucagon causes glycogen to be converted back to glucose=enters blood
  • causes blood glucose level to rise
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Type 1 Diabetes

Type 1 diabetes=pancreas can't make insulin (usually genetic + from childhood) & treated with injections. Controlling Type 1 diabetes:

  • Insulin therapy - involves injecting insulin into blood=several throughout day. Injections ensure glucose=removed from blood quickly once food digested=stops level of glucose in blood from getting too high=effective treatment. Amount of insulin depends on person's diet, how active=these affect blood glucose leve
  • Limit intake of foods rich in simple carbs - e.g sugars=also advised to spread intake of starchy carbs throughout day + to pick varities of foods that absorbed more slowly ( so don't cause sharp rise in blood glucose level)
  • Regular exercise - helps to lower blood glucose level as increased metabolism of cells during exercise removes more glucose from blood


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Type 2 Diabetes

Insulin used to be extracted from pancreases of pigs/cows but now human insulin made by genetic engineering=human insulin doesn't cause reactions like animal insulin did. Insulin injections help to control blood glucose levels but can't controlled as acurately as having normal working pancreas=so may still have long-term health problems.

Type 2 diabetes - body cells no longer respond to insulin produced by pancreas because so much glucose/sugar in blood (often cause by poor diet/lifestyle=being overweight can increase chance of developing=obesity major risk)=can be treated with controlled diet & exercise. = later onset diabetes. Controlling Type 2 diabetes:

  • Eating a carbohydrate-controlled diet - includes controlling person's intake of simple carbs to avoid sudden rises in glucose
  • Regular exercise - helps to lower blood glucose level
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Modern treatment options

Are new treatment options available + some currently being researched for people with Type 1 diabetes:

  • Diabetics can have pancreas transplant - successful operation=won't have to inject with insulin again. But as with any organ transplant=body can reject tissue. If this happens have to take costly immunosuppressive drugs (drugs that suppress immune system), which can have serious side-effects
  • Modern research into artificial pancreases + stem cell research may mean elimination of organ rejection but way to go yet.

Testing for diabetes - at high blood glucose level, glucose begins to move to urine=diabetes can be tested by looking for glucose in urine sample. A blood test for glucose can confirm diagnosis=blood test more reliable as gives current level of glucose in blood (urine samples can be hrs old) & can detect high level of glucose when level is not yet high enough for glucose in urine.

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