Homeostasis and negative feedback control. Advantages of Homeostasis Homeostasis has survival value because it means an animal can adapt to a changing.

Homeostasis and negative Homeostasis and negative feedback controlfeedback control

Advantages of Homeostasis Advantages of Homeostasis Homeostasis has survival value because it Homeostasis has survival value because it means an animal can adapt to a changing means an animal can adapt to a changing environment. It can deal with the temperature environment. It can deal with the temperature difference you face when you step out your difference you face when you step out your front door.front door.The body will attempt to maintain a norm, the The body will attempt to maintain a norm, the desired level of a factor to achieve desired level of a factor to achieve homeostasis. However, it can only work within homeostasis. However, it can only work within tolerable limits, where extreme conditions can tolerable limits, where extreme conditions can disable the negative feedback mechanismdisable the negative feedback mechanismIn these instances, death can result, unless In these instances, death can result, unless medical treatment is executed to bring about medical treatment is executed to bring about the natural occurrence of these feedback the natural occurrence of these feedback mechanismsmechanisms

Negative Feedback ControlNegative Feedback Control

In animals such as ourselves, the internal In animals such as ourselves, the internal environment of our bodies must have certain environment of our bodies must have certain conditions within tolerable limits to continue the conditions within tolerable limits to continue the healthy functioning of us.healthy functioning of us.This is done by a process called negative This is done by a process called negative feedback control, where various receptors and feedback control, where various receptors and effectors bring about a reaction to ensure that effectors bring about a reaction to ensure that such conditions remain favourable. such conditions remain favourable. In this PowerPoint, we investigate the control of In this PowerPoint, we investigate the control of blood sugar concentrations, water blood sugar concentrations, water concentrations and temperatureconcentrations and temperature

The principle of negative The principle of negative feedback control is illustrated by feedback control is illustrated by

the diagram belowthe diagram below

This occurrence is known as physiological This occurrence is known as physiological homeostasis, translating in layman's terms to the homeostasis, translating in layman's terms to the physical equilibrium. It is essentially a corrective physical equilibrium. It is essentially a corrective mechanism, consider the following scenario in a personmechanism, consider the following scenario in a person

The level of glucose in the bloodstream drops The level of glucose in the bloodstream drops The person requires glucose in cells to meet the demand for The person requires glucose in cells to meet the demand for

ATP ATP The body detects this with a particular receptor designed for The body detects this with a particular receptor designed for

this function this function These receptors release hormones, chemical messages These receptors release hormones, chemical messages

that initiate the start of the feedback mechanismthat initiate the start of the feedback mechanism The hormones travel to their target tissue and initiate a The hormones travel to their target tissue and initiate a

corrective response corrective response In this case, the corrective response is the secretion of more In this case, the corrective response is the secretion of more

glucose into the bloodstreamglucose into the bloodstream

Requirement of Negative Requirement of Negative Feedback ControlFeedback Control

Because mammals are warm blooded, the Because mammals are warm blooded, the enzymes that are part of their make-up as a enzymes that are part of their make-up as a warm blooded animal require a certain warm blooded animal require a certain temperature to operate optimally. Also, the temperature to operate optimally. Also, the water concentration of a cell and its chemical water concentration of a cell and its chemical concentration must remain at a certain level to concentration must remain at a certain level to allow normal cellular processes to occur.allow normal cellular processes to occur.

In light of this, the feedback mechanism in In light of this, the feedback mechanism in such warm blooded animals is essential in such warm blooded animals is essential in regards to allowing the body to work in optimal regards to allowing the body to work in optimal conditions - so any change in from the norm in conditions - so any change in from the norm in temperature is corrected by the feedback temperature is corrected by the feedback mechanism.mechanism.

Osmoregulation Osmoregulation

Osmoregulation is the regulation of water Osmoregulation is the regulation of water concentrations in the bloodstream, concentrations in the bloodstream, effectively controlling the amount of water effectively controlling the amount of water available for cells to absorb. available for cells to absorb.

OsmoregulationOsmoregulation

The homeostatic control of water is as followsThe homeostatic control of water is as follows A change in water concentration leads to active via negative A change in water concentration leads to active via negative

feedback control feedback control Osmoreceptors that are capable of detecting water concentration Osmoreceptors that are capable of detecting water concentration

are situated on the hypothalamus next to the circulatory system are situated on the hypothalamus next to the circulatory system The hypothalamus sends chemical messages to the pituitary The hypothalamus sends chemical messages to the pituitary

gland next to it.gland next to it. The pituitary gland secretes anti-diuretic hormone (ADH), which The pituitary gland secretes anti-diuretic hormone (ADH), which

targets the kidney responsible for maintaining water levels. targets the kidney responsible for maintaining water levels. When the hormone reaches its target tissue, it alters the tubules When the hormone reaches its target tissue, it alters the tubules

of the kidney to become more / less permeable to waterof the kidney to become more / less permeable to water If more water is required in the blood stream, high concentrations If more water is required in the blood stream, high concentrations

of ADH make the tubules more permeable. of ADH make the tubules more permeable. If less water is required in the blood stream, low concentrations of If less water is required in the blood stream, low concentrations of

ADH make the tubules less permeable. ADH make the tubules less permeable.

Evolutionary Adaptations in Water Evolutionary Adaptations in Water RegulationRegulation

Evolutionary adaptations that organisms have Evolutionary adaptations that organisms have achieved through natural selection. achieved through natural selection.

Ways in which both animals and plants can be Ways in which both animals and plants can be better adapted to cope with extreme better adapted to cope with extreme environments (desert or wetlands). environments (desert or wetlands).

These changes can be These changes can be behavioural, structural behavioural, structural or physiologicalor physiological, and in some way promote , and in some way promote water regulation. water regulation.

Both plant and animal adaptations are Both plant and animal adaptations are investigatedinvestigated

Blood / Sugar Regulation Blood / Sugar Regulation

Two hormones are responsible for Two hormones are responsible for controlling the concentration of glucose in controlling the concentration of glucose in the blood. These are insulin and the blood. These are insulin and glucagon. The diagram illustrates the glucagon. The diagram illustrates the principle of negative feedback control in principle of negative feedback control in action involving blood/sugar levels. action involving blood/sugar levels.

Pancreas Receptors Pancreas Receptors

The receptors of the pancreas are responsible for The receptors of the pancreas are responsible for monitoring glucose levels in the blood, since it is monitoring glucose levels in the blood, since it is important in every cell for respiration.important in every cell for respiration.

Two types of cell release two different hormones from Two types of cell release two different hormones from the pancreas, insulin and glucagon. These hormones the pancreas, insulin and glucagon. These hormones target the liver, one or the other depending on the target the liver, one or the other depending on the glucose concentrationglucose concentration

In cases where glucose levels increase, less glucagon In cases where glucose levels increase, less glucagon and more insulin is released by the pancreas and targets and more insulin is released by the pancreas and targets the liver the liver

In cases where glucose levels decrease, less insulin and In cases where glucose levels decrease, less insulin and more glucagon is released by the pancreas and targets more glucagon is released by the pancreas and targets the liverthe liver

The Liver The Liver

The liver acts as a storehouse for glycogen, the The liver acts as a storehouse for glycogen, the storage form of glucose. When either of the above storage form of glucose. When either of the above hormones target the liver, the following occurshormones target the liver, the following occurs

InsulinInsulin - Insulin is released as a result of an increase in - Insulin is released as a result of an increase in glucose levels, and therefore promotes the conversion glucose levels, and therefore promotes the conversion of glucose into glycogen, where the excess glucose of glucose into glycogen, where the excess glucose can be stored for a later date in the liver can be stored for a later date in the liver

GlucagonGlucagon - Glucagon is released as a result of an - Glucagon is released as a result of an decrease in glucose levels, and therefore promotes the decrease in glucose levels, and therefore promotes the conversion of glycogen into glucose, where the lack conversion of glycogen into glucose, where the lack glucose can be compensated for by the new supply of glucose can be compensated for by the new supply of glucose brought about from glycogenglucose brought about from glycogen

Diabetes Diabetes

Diabetes insipidus is a condition where excess Diabetes insipidus is a condition where excess urine is excreted caused by the sufferers inability urine is excreted caused by the sufferers inability to produce ADH and promote the retention of to produce ADH and promote the retention of water.water.

Diabetes Mellitus is another form of diabetes where Diabetes Mellitus is another form of diabetes where the sufferer does not have the ability to produce the sufferer does not have the ability to produce sufficient insulin, meaning that glucose cannot be sufficient insulin, meaning that glucose cannot be converted into glycogen. Anyone who has this converted into glycogen. Anyone who has this condition usually has to take injections of insulin condition usually has to take injections of insulin after meals and snacks to maintain their storage of after meals and snacks to maintain their storage of glucose needed in emergencies.glucose needed in emergencies.

Fight or Flight Fight or Flight

In emergencies, adrenaline is released by the body In emergencies, adrenaline is released by the body to override the homeostatic control of glucose. to override the homeostatic control of glucose. This is done to promote the breakdown of This is done to promote the breakdown of glycogen into glucose to be used in the emergency. glycogen into glucose to be used in the emergency. These emergencies are often known as 'fight or These emergencies are often known as 'fight or flight reactions'.flight reactions'.

Adrenaline is secreted by the adrenal glands. The Adrenaline is secreted by the adrenal glands. The secretion of it leads to increased metabolism, secretion of it leads to increased metabolism, breathing and heart rate. Once the emergency is breathing and heart rate. Once the emergency is over, and adrenaline levels drop, the homeostatic over, and adrenaline levels drop, the homeostatic controls are once again back in placecontrols are once again back in place

Temperature in Homeotherms

Animals capable of temperature regulation within a given range are deemed homeotherms (alternatively homiotherms or homotherms). They have the ability to regulate temperature via negative feedback control.Temperature is controlled in a variety of ways in these animals.

Temperature in Homeotherms

The hypothalamus once again acts as a receptor in regulation, by detecting fluctuations in temperature. These receptors are better known as thermoreceptors.

Temperature in Homeotherms

Skin also possesses thermoreceptors which can detect the temperature of the external environment. This information is relayed to the hypothalamus which can in turn transmit nerve pulses for corrective mechanisms to occur

Corrective Mechanisms in Temperature Control

Increased sweating is a corrective response aimed to reduce the temperature of the organism.

Corrective Mechanisms in Temperature Control• Vasodilation is a corrective response

where the blood vessels close to the skin surface become more dilated, meaning there is a larger surface area for heat to be lost to the external environment from the blood vessel carrying over-heated blood.

• Vasoconstriction is the opposite of this and occurs when temperatures in an organism drop. The blood vessels become constricted so that minimal heat loss occurs.

Corrective Mechanisms in Temperature Control

The hairs on your body also play an important role in temperature regulation. A corrective response can occur where the hairs 'stand on end', and trap a layer of air between the hair and the skin. This insulation of warmer air next to the skin reduces heat lost, while a thin layer of insulation would increase heat loss.

Corrective Mechanisms in Temperature Control

Other corrective mechanisms are involved, such as a drop in metabolic rate and shivering when temperatures drop.