Homeostastis

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What is homeostasis?

This is the constant maintence of the internal body environment. This ensures that cells are in conditions best suited to their needs, and when a flacuation occurs either in the internal or external envirnoment, the changes are returned back to normal. 

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The importance of homeostasis:

Hoemostastis is essential for proper functioning organisms for 3 main reasons:

  • To allow reactions in the body to occur at a predictable, relaible and constant rate. Enzymes are very senitive to even the smallest changes in pH and tempreture, and a slight flacutaion can cause reactions to stop working (reduced enzyme activty), and enzymes can get dentared.
  • Water potentail. We need to ensure no water is lost or gained from a cell, no shriveling or shrinking of cells, by osmoises. Additionally, we need to ensure a constant realible source of glucose for respiring cels.
  • Animals who are able to control their internal envorinment are much more indepedent on the environment. This advantage allows them to seek shelter, find food and a mate easier that other organisms.
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Control mechanisms:

This is a self regulting system.

  • There is a SET POINT (the norm), where the system operates best and most effiecntly at.
  • This is mointered by the RECEPTORS any any deviation from the set point gets moinitered and informs the...
  • CONTROLLER, this anaylses the message from receptors and decides upon best course of ation to take, bringing the conditions back to the norm. The controller sends the response through the...
  • EFFECTOR.The response is brought about, and the levels return back to the set point.
  • The FEEDBACK LOOP is when the effector sends the message to the receptor, informing about the change thats been brought about.
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What is homeostasis?

This is the constant maintence of the internal body environment. This ensures that cells are in conditions best suited to their needs, and when a flacuation occurs either in the internal or external envirnoment, the changes are returned back to normal. 

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Regulation of body temperature:

Most animals are able to control their body tempreture to a greater or lesser degree. In doing so, the must be able to lose heat and gin heat.

METHODS OF GAINING HEAT:

  • Production of heat by metobolic activity
  • Gain of heat from the envirnment

METHODS OF LOSING HEAT:

  • Evaporation of heat
  • Loss of heat due to the environement
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Regulation in Ecotherms:

Ecothermic organisms, are organisms who are unable to regulate their internal body tempreture. This means that they solely rely on the envirment,and any flacuation in external tempreture, will have a great impact on them. They therefore have adaptations to control their tempreture:

  • EXPOSING THEMSELF to the sun rays, which warm them up.
  • TAKING SHELTER to prevent being over exposed to the sunlight at peak times of heat, and staying inside when external tempreture falls to prevent heat loss.
  • WARMTH FROM THE GROUND
  • GENERATIONG METOBOLIC HEAT from processes such as resperation
  • COLOUR VARIATIONS orgainsims with darker fur absorb moresun rays that orgainsms who have lighter fur colours.
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Regulation of Endotherms:

Endothermic organisms are able to control their internsl hea, despite external envirnmental flucations. They use behavioural and pyscoligal methods to maintain and regulate a constant body tempreture. For example: Curling up, huddling, take shelter etc.

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Conserving heat:

Organisms who try maintain a high body tempreture generally have a smaaler surface area to volume ratio, meaning less heat loss. 

CONSERVING HEAT METHODS INCLUDE:

  • VASOCONSTRICTION. Arteries near the surface of the skin constrict, reducing the blood flow throught the thick layer of insulated skin, so less heat is lost by radiation into the envirnemnt.
  • SHIVERING. Rapid rythmatic movemnet of muscels produces heat.
  • STOP SWEATING
  • INCREASE IN METOBOLIC REACTIONS. A hormone is produced to increase reaction rates meaning more heat produced.
  • RAISING OF HAIR. Erector muscels contarct, forming a layer of insulation between the ski and the hair.
  • BEHAVOURAL MECHANISMS, sheltering from wind, huddling and curling together.
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Losing heat:

These adaptations include:

  • INCREASE OF SWEATING, heat is lost when the water evoporates from the skin.
  • VASODIALATION
  • RELAXATION OF ERACTOR MUSCELS
  • BEHAVORAL MECHANSIMS, avoiding shelter, seeking and burrowing.
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Control of body temperature:

Themorecetors detect any devaitons from the set point and send a message to the hypthalamus. The responses include:

  • HEAT GAIN CENTER, in response to decrease in body tempreture
  • HEAT LOSS CENTER, in response to increase in bodu tempreture
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Control of body temperature:

Themorecetors detect any devaitons from the set point and send a message to the hypthalamus. The responses include:

  • HEAT GAIN CENTER, in response to decrease in body tempreture
  • HEAT LOSS CENTER, in response to increase in bodu tempreture
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Hormones:

Hormones have the following chacteristics:

  • They are produced by the endocrine glands
  • They travel in the blood plasma to target cells, where they bind to receptors
  • They are useful in small quantites, effects are widespread and are long lasting.

THE SECOND MESSENGER MODEL

Here we have two hormones involved in the regulation of blood glucose levels, glucagon and insulin. It works as follows.

  • The first hormone ADRENALINE binds to the specic receptor on the cell surface memnrane  forming a hormone-receptor-complex.
  • This activates and enzyme, which prouces a chemical inside the cell cAMP.
  • This second messenger cAMP causes a series of chemical changes to occur in the body.
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The role of the pancreas:

The pancresse is made up of many hormone producing cells called ISLETS OF LANGERHAMS, and there are two types of cells:

  • ALPHA CELLS, these are larger and produce glucagon.
  • BETA CELLS, these are smaller and produe insulin.
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Blood glucose and its sources:

The normal concentarion of glose is 90mg per 100cm3 of blood. We get bllod glucose from three sources:

  • From our DIET, the rich carbohydrate food which gets broken down into maltose.
  • From the breakdown of glycogen- GLYCOENOLYSIS
  • From GLUCONEOGENESIS, the production of glose from new sources such as amino acids and glyceral.
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Insulin and the Beta cells

The B Cells detect a rise of blood glucose concentration, this automatically secretes insulin on th body cells. Nearly all cells have glcoprotein receptors on their cell surface membranes, and when binded to insulin, causes the following few changes;

  • Change in the tertairy structer of the carrier protein, which causes the carryer protien to change shape, open and allowing glcose into the cells.
  • Inreases the amount of carryer proteins on the cell surface membranes.
  • Increases the number of enzymes which convert glucose to glycogen and fat.

This causes the following few changes:

  • Increase rate of absortpion of cell, e.g muscel cells.
  • Increases respirotary rate of cell, more glocose removed from blood.
  • Incraese the conversion of glucose to glycogen.
  • Incraese the conversion of glucose to glcerol/fat.
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Glucagon and the Alpha cells and Adrenline

The Alpha cells detect a fall of blood glucose level and secrete glucagon directly on the cells, which bind to specific receptors in the liver. This activates and enzyme to:

  • Increase conversion of glycogen to glucose.
  • Increase conversion of amino acids/glycerol to glucose.

Adrenaline is also released to increase the blood glucose level. It works by:

  • Activating enzyme to produce glucose from glycogen.
  • Deactivating enzyme which produces gylcogen from glucose.
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Diabetes

There are two types of diabites:

  • TYPE 1: This is whn there is not enough insulin being produced from the cells, as the atuoimmune system ttacks the bodys cells( the B cells). This condtiom devolpes quickly, more common in younger children.
  • TYPE 2: This is due to the glycoprotein receptors losing there responsivness, and not an adequate amount of insulin is produced. This devolopes slowly, generally in older people.

Symptons include:

  • High blood glucose levels.
  • Need to urinate very often.
  • Very tired.
  • Very hungry and thirsty.
  • Loss weight.
  • Glucose in urine.
  • Itching/thrush.
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Diabeties control

  • TYPE1: This is when we inject a person with a dose of insulin before each eal, measured by the biosenser.(It is not given orally as its a protein and would get brocken down)
  • TYPE 2: Regulating the carbohydrate intake, excersie and drugs which stimulte insulin production.
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