TOPIC 5: REGULATION | BIOLOGY FORM 3

BIOLOGY NOTES REGULATION

TOPIC 5: REGULATION | BIOLOGY FORM 3

The Concept of Regulation

Regulation is the maintenance of a relatively constant body internal environment.

OR is the process of controlling the internal body environment and needs.

Cells will only function properly if there is little or no fluctuation in the conditions of their immediate environment.

HOMEOSTASIS

Is the process of maintaining a constant internal environment in living organisms

IMPORTANCE OF REGULATION

Reasons that show importance of regulation:-

1. Ensuring survival of the organisms

2. Maintaining favorable condition such as pH and required ionic concentration for the functioning of cells, tissues and organs.

3. Enabling organisms to get rid of body wastes and useless materials for example excess water and salts

4. Enabling organisms to get rid of excess materials for example excess water and salts

NB: To understand the mechanism of regulation there is a great need to distinguish between two aspects of the environment to the organism these are:

1. Internal environment

2. External environment

1. INTERNAL ENVIRONMENT

Is an immediate surroundings of the cells comprising of interstitial (Intracellular), intercellular or tissue fluid.

The tissue fluid contains dissolved food, dissolved gases and chemical ions

2. EXTERNAL ENVIRONMENT

Is an immediate surroundings of the organism  It may be aquatic (water) or terrestrial (land).

FORMATION OF TISSUE FLUID

TISSUE FLUID

Is the medium from which cells obtain their requirements and through which cells discharge their waste products.

Tissue fluid is formed from the blood by the process called ultra – filtration.

The ultra – filtration occurs due to the pumping of the heart and the narrowness of the capillaries that causes the build up of pressure on the arteriole side of the capillaries that forces water and low molecular weight component of blood out of the capillaries into the intercellular spaces hence tissue fluid is formed.

Components of tissue fluid

1. Tissue fluid contains the same composition as blood but lacks cells and plasma proteins.

2. The same composition of tissue fluid and blood are:

3. Glucose

4. Amino acids

5. Fatty acids

6. Oxygen

7. Hormone e.g. nutshell fluids.     

Main function of tissue fluid

Provides the condition where cells absorb nutrients and oxygen and shed into it waste materials such as carbon dioxide and urea when flow in intercellular space.

Bathes the cells and eventually find its way back into the blood.

NB: Excess fluid is drained into the lymphatic vessels to form Lymph.

Lymph is an excess tissue fluid in lymphatic vessels that the lymph has no cells and plasma protein while the blood has cells and plasma protein.

The similarity between the lymph and blood is that both they have glucose, amino acids, oxygen and hormones.

MECHANISM OF REGULATION

Mechanism of regulation is known as Homeostatic regulatory mechanism

This mechanism enables organism to adjust fairly quickly to any slightly changes.

The process of regulation or homeostasis works on a feedback mechanism as follows:

When a factor in the body such as blood sugar level drops or rises above normal, it is detected and then corrective action is taken to bring it back to normal. Such a response is called NEGATIVE FEEDBACK.

BUT

If the change below or above the normal is not corrected but instead there is further deviation, this is called POSITIVE FEEDBACK.

Consider the figure below showing the mechanism of regulation

THE FIGURE OF GENERALIZED MECHANISM OF REGULATION

 

 

 

 

 

 

 

 

 

Deviation

Further deficiency.

NOTE: The feedback mechanism is divided into two types, namely:

1. Negative feedback mechanism.

2. Positive feedback mechanism.

1. Negative feedback mechanism: is the mechanism through which the effectors restore the normal condition.

2. Positive feedback mechanism: is the mechanism that fails or break down any deviation from the normal leads to further deviation.

TYPES OF REGULATION

There are various types of regulation in the animals’ bodies. These are:-

(i) Temperature regulation (thermoregulation)

(ii) Blood sugar regulation

(iii)Osmoregulation

THERMOREGULATION

Is the maintenance of a relatively constant body temperature.

A constant body temperature favours efficient enzymes activities.

Thermoregulation is very important because:

— The high temperature denatures or destroys the enzymes

— Low temperature inactivates the enzymes by slowing down or stopping enzyme catalyzed reactions.

The external temperature affecting the body is detected by thermo receptors in the skin.

The thermo receptors relay information to the temperature regulation centre in the hypothalamus in the brain through sensory nerves.

The internal temperature is detected by the hypothalamus as the blood flows in the brain.

HYPOTHERMIA

Is the condition that occurs when the body temperature falls than the normal

Hypothermia cause permanent damage to the brain.

Hypothermia is a risk for mountaineers since they are exposed to low temperatures and wind.

It is also risky to swimmers, since water conducts heat away from the body

Also elderly who tend to be less active thus they generate less heat from the activity of muscles.

HYPERTHERMIA

Is the condition which occurs when the body temperature increases above normal

CATEGORIES OF THERMOREGULATION

Thermoregulation can be categorized into two groups, namely:

a. Homoiothermic

b. Poikilothermic

(a) HOMOIOTHERMIC THERMOREGULATION

Is the type of thermoregulation where by animals are able to maintain constant internal body temperature even when the surrounding temperature changes.

Animals which are able to maintain constant internal body temperature even when the surrounding temperature changes are called homoiothermic animals.

Homoiothermic animals are also called warm blooded animals, homoiotherms or endotherms.

Example of homoiothermic animals

>Mammals

>Birds.

ADVANTAGES OF HOMOIOTHERMY

(i) Enables animals to exploit a wide range or geographical habitats

(ii) Homoiotherms have high metabolic rate, hence remain active throughout.

(iii) Endotherms are independent of external temperature.

(iv) Helps animals to respond faster to stimuli

(v) Homoiothermic organisms have a greater survival value.

Enzyme controlled reactions proceed without interruptions.

DISADVANTAGES OF HOMOIOTHERMY

(i) They need food with high calorific value such as fat in order to maintain their body temperature especially during cold.

(ii) Endotherms consume a lot of food to be in position to generate heat internally.

(iii) They have a problem of overheating in tropics and hot desert areas.

PAIKILOTHERMIC

Is the type of thermoregulation where some animals change their body temperature with change in the external environment temperature

Animals whose body temperatures change with change in the surrounding temperature are called Poikilothermic animals

Poikilothermic animals are also called cold blooded animals, poikilotherms or ectotherms.

Example of poikilothermic animals

> Amphibians e.g. frogs

> Reptiles e.g. lizards and snakes

> Fishes e.g. sharks, tilapia

ADVANTAGE OF POIKILOTHERMY

1. They have a lower food consumption as they do not generate heat internally i.e. consume little amount of food.

2. Poikilotherms found in tropics and hot desert do not have a problem of overheating because there is no heat generated internally.

3. Ectotherms need food with low calorific value.

DISADVANTAGES OF POIKILOTHERMY

1. They have low metabolic rate and therefore sluggish when external temperature are low and can be preyed upon easily.

2. Due to over reliance on external temperature ectotherms take time to respond to stimuli.

3. During low temperature, poikilotherms may go to hibernation and may even die.

QUESTION: 1. The graph below shows the relationship between environmental temperature and body temperature in two different animals A and B.

A

a. What happens to the body temperature of animal A as the external temperature increases.

ANSWER: The body temperature of animal A increases as the external temperature increases.

b. What term is used to describe :

Animals of type A

Animals of type B

ANSWERS

Animals of type A are poikilotherms/ectotherms

Animals of type B are Homoiotherms / endotherms

c. State, giving reasons, which type of animal you would expect to be more widely distributed.

ANSWERS: The animals of type B can be more widely distributed

d. The animals of type B can be more widely distributed due to the following sreasons:

(i) Endotherms are independent of external temperature

(ii) Endotherms can respond faster to stimuli

(iii)Endotherms have a high metabolic rate.

METHODS OF HEAT GAIN AND HEAT LOSS IN ANIMALS

Animals gain or lose heat to the environment through the following methods:

i. Conduction

ii. Radiation

iii. Evaporation

iv. Convection

Conduction

Is the transfer of heat energy from one body to another through direct contact with each other.

For example when a person takes a cold shower on a hot day, he/she loses heat to the surrounding thus cooling his/her body temperature.

The same applies when he/she sits on a cold object like a chair. He/she will feel the coldness of the chair due conduction.

Radiation

Is the transfer of heat energy from one body to another without the bodies being in contact with each other.

The transfer of heat energy is usually through infra-red waves.

Up to 60% of heat lost by a person sitting in a room at 21C may be due to radiation.

Evaporation

Is the change of a liquid to a vapour.

Evaporation is accompanied by cooling.

That is why sweating provides a cool effect and accounts for up to 25% of the total heat energy lost by a person.

Convection

Is the movement of air resulting from pockets of warm air being replaced by cooler air and vice versa.


MECHANISM FOR TEMPERATURE REGULATION

For temperature to be kept constant endotherms have developed special mechanisms that help them lose and or gain heat.

Body temperature is regulated through:-

i. Physiological means

ii. Behavioural means

PHYSIOLOGICAL MEANS

This occurs under the control of the nervous system.

In physiological means, body temperature regulation is done through the following methods:

(i) Sweating

(ii) Panting

(iii)Shivering

(iv) Vasodilation

(v) Vasoconstriction

Contraction and relaxation of hair erector Pilli muscles.

Change of metabolic rate

Sweating

This occurs when animal lose water vapour from their body surface.

Latent heat of vaporization is lost from the body as sweat evaporates.

Panting

Is the process of hanging out of tongue to allow heat loss through evaporation

Panting is mostly done by dogs and cats as a way cooling their bodies because they have no sweat glands except in the pads of the paws.

Vasodilation

Is the increase of diameter of arterioles near the surface of the skin

This enables more blood to flow near the surface of the skin and more heat is lost to the surrounding by conduction, convection and radiation.

Vasoconstriction

Is the decrease of arterioles diameter near the skin surface.

This decrease blood flow near the skin surface hence less heat is lost to the surrounding by conduction, convection

Shivering

Is an involuntary rhythmic contraction of muscles which serves to generate heat during cold weather.

Change of metabolic rate

This involves the increase of metabolic rate during cold weather and the decrease of metabolic rate during hot weather.

MECHANISM OF TEMPERATURE REGULATION THROUGH PHYSIOLOGICAL
MEANS

Through physiological means homoiotherms are able to regulate their body temperature as follows:

During hot weather condition

During hot weather condition organisms keep their body temperature constant through the following methods:

(i) Sweating

When sweat evaporates on the skin, it produces a cooling effect on the body thereby lowering the body temperature.

(ii) Panting

Dogs and cats cool their bodies through hanging out of their tongues to allow heat loss through evaporation.

(iii)Relaxation of erector Pilli muscles

During hot weather condition, erector Pilli muscles relax making the hair to lie flat on the skin surface to encourage loss of heat from the body by radiation and convection.

(iv) Vasodilation of arterioles

The diameter of arterioles near the surface of the skin becomes wider. Therefore more blood flow near the skin surface hence more heat is lost to the surrounding by conduction, convection and radiation.

(v) Decrease in metabolic rate

During hot weather condition
metabolic rate decrease therefore less heat is generated and hence the body temperature falls.

During cold weather condition

During hot weather condition organisms keep their body temperature constant through the following methods:

(i) Shivering

This is an involuntary rhythmic contraction of skeletal muscles, which serves to generate heat during cold weather.

(ii) Contraction of erector Pilli muscles

During cold weather condition, erector Pilli muscles contract making hairs on the skin surface to rise. This causes more air to be trapped between the hairs, making it an insulator thus preventing heat loss from the body to the surrounding.

In human, contraction of the erector pilli muscles causes ‘goose pimples’ since there is very few hair on the skin. When this happens, the sweat pores close up thus no sweat is lost through evaporation.

(iii) Vasoconstriction of arterioles

The diameter of arterioles near the skin surface becomes narrower. Therefore the blood supply to the skin surface is reduced and less heat is lost to the surrounding.

(iv) Increase metabolic rate

During cold weather condition
metabolic rate increase therefore more heat is generated and hence the body temperature rises.

A SUMMARY OF BODY TEMPERATURE REGULATION BY PHYSIOLOGICAL
MEANS

When the body temperature rises above normal (during hot) When the body temperature drops below normal
– Hypothalamus detects change in temperature.

– Signals are sent to the tissues which respond by

– Increasing sweating

– Vasodilation

– Relaxation of hair erector pilli muscle

– Reduced metabolism

– No shivering

– Hypothalamus detects the change.

– Signals are sent to the body tissues which responds by

– Reducing sweating

– Vasoconstriction

– Contraction of hair erector pilli muscles

– Increase metabolism
– Shivering.

BEHAVIOURAL MEANS

This occurs under the organism’s will

In behavioural means, body temperature regulation is done through the following methods:

(i) Moving to a shaded place.

(ii) Wearing of a coat

(iii) Migration

(iv) Clustering

(v) Coiling

(vi) Hibernation

(vii) Aestivation

(viii) Basking

Migration

This is the movement of animals covering a long distances in order to avoid harsh environmental temperature.

Clustering

This involves grouping together of animals to share warmth in order to raise body temperature

Example: bees cluster together

Coiling

This is the process whereby animals are rounding into a series of circle.

Hibernation

This is a behavioural pattern where an organism goes into a deep sleep to avoid cold weather conditions.

Aestivation

This is a behavioural pattern where an organism goes into a deep sleep to avoid warm weather conditions.

Basking

This is a behavioural pattern where an organism moves in the sun to raise the body temperature

Snakes, lizards and chameleons bask in the sun to raise their body temperature

MECHANISM OF TEMPERATURE REGULATION THROUGH BEHAVIOURAL MEANS

Through behavioural means homoiotherms and poikilotherms are able to regulate their body temperature as follows:

During hot weather condition During cold weather condition
– Some organisms move into the shade.

– Humans wear light clothing

– Other drinks cold water to cool down their bodies.

– Some roll in water or splash water to cool off.

– Some burrow underground

– Some organism aestivate

– Some organisms hibernate

– Humans wear more clothing

– Some organism cluster together in groups to share warmth

– Some organism spend most of the day in deep burrow

– Some organisms bask in the sun

RELATIONSHIP BETWEEN BODY SKIN AND HEAT LOSS IN ORGANISMS

Small animals have a large surface area to volume ratio. They therefore lose heat faster which makes them to eat more food to cater for their high metabolism.

Large animals have small surface area to volume ratio. They therefore lose heat at a slower rate.

TEMPERATURE REGULATION IN ANIMALS LIVING IN COLD CLIMATE

Animals living in very cold climate such as polar bears have the danger of suffering hypothermia. Therefore, they are adapted to avoid heat loss by having the following features;-

i. Thicker hair (fur) which is better in holding air around the body thus acts as an insulator to prevent heat loss to the surrounding.

ii. They have a thick layer of fat beneath the dermis that prevents heat loss.

iii. Large body shape compared to their counterpart living in hot or temperate climate. Large bodies means small surface are to volume ration thus reduced heat loss.

OSMOREGULATION

Is the maintenance of relatively constant osmotic pressure of body fluids

OR is the control of the water content and salt concentration in the body of an organism.

The osmotic pressure of the body fluids (the blood and tissue fluid) is determined by the concentration of various solutes such as sugar, salts and chemical ions.

IMPORTANCE OF OSMOREGULATION

(i) Ensures proper functioning of the cells.

NB

If there is too much water in the blood, the osmotic pressure increase, water will move from blood into the cells causing cells to swell even burst and disrupt metabolic activities.

If there is too little water in the blood, the osmotic pressure decreases, water will move from cells into the blood by osmosis causing cells to shrink and disrupt metabolic activities as well

FACTORS THAT AFFECT THE CONTENT OF SALT AND WATER IN THE BODY

Content of salt and water in the blood is affected by the following factors:

i. Amount of water taken in the body

Large intake of water causes blood to have too much water while fewer intakes causes less water in the blood. It is advised to take two liters equivalent to eight glasses of water per day for the body to function properly.

ii. Climatic condition

During hot weather there is increased sweating which cause loss of water by evaporation thus reduced amount of water in the blood. The vice versa occurs during cold weather.

iii. Amount of salt taken into the bod

Putting less salt in food causes reduced salt in the blood while putting too much salt in food causes increased amounts of salt in the blood. Moderate amounts of salt should be taken too much salt is not healthy as it may lead to high blood pressure.

iv. Hormonal Abnormalities

When less Antidiuretic hormone (ADH) is produced it leads to increased content of water in the blood and vice versa.

THE MECHANISM OF OSMOREGULATION

Osmoregulation is controlled by the hypothalamus and the pituitary gland working together with the kidneys.

When the osmotic pressure of the body fluids rises as a result of dehydration or excessive intake of salts, osmoreceptors in the hypothalamus of the brain are stimulated. These cells relay information to the pituitary gland which is stimulated to secrete a hormone known as vasopressin (Antidiuretic hormone) into the blood. Antidiuretic Hormone stimulates the kidney tubules to become more permeable to water to increase the water content in the blood hence osmotic pressure falls to normal level.

If the osmotic pressure falls below normal due to large intake of water the pituitary gland is less stimulated and less ADH is produced hence the kidney reabsorbs less water and the osmotic pressure rises to normal results to the production of large volume of dilute urine.

DIABETES INSPIDUS

This is a disease that results from the failure of the pituitary glands to produce sufficient antidiuretic hormone (ADH).

Causes of diabetes inspidus

Inability of the pituitary gland to produce ADH

Symptoms of diabetes inspidus

Diuresis

Is a condition of producing large amount of dilute urine.

Effects of diabetes inspidus
Dehydration.

A patient required to takes a lot of water.

BLOOD SUGAR REGULATION

This is the regulation of the amount of glucose in the blood.

In human beings, the normal blood sugar concentration at a steady state is about 90mg per 100ml of blood.

The maintenance of a relatively constant blood glucose level is carried out by two pancreatic hormones namely, Insulin and Glucagon

These hormones are secreted by a specialized group of pancreatic cells called islets of Langerhans.

Insulin

Is the hormone produced by beta cells in the islets of Langerhans

Roles of insulin in regulation

i. To promote the conversion of glucose to glycogen and stored in the liver and skeletal muscles.

ii. To promotes the uptake of glucose from the blood by muscles cells

iii. Increases protein synthesis in some cell.

Glucagon

Is the hormone produced by alpha cells in the islets of Langerhans

Role glucagon in regulation

(i) To promote the conversion of glycogen to glucose in the liver cell.

(ii) Glucagon stimulates absorption of glucose from the ileum.

MECHANISM OF BLOOD SUGAR REGULATION

When there is excess glucose in the blood, the beta cells in the islets of Langerhans produce more insulin and less glucagon. The insulin produced stimulates the liver cells to convert excess glucose to glycogen. Hence, the blood sugar level falls to normal level.

Insulin

Glucose Glycogen

(Excess) (Normal)

 On other hand, when there is low blood glucose in the blood. The alpha cells in the islets of Langerhans produce more glucagon and less insulin. The glucagon produced stimulates the liver cells to convert glycogen to glucose. Hence, blood sugar level is raised back to normal level.

Glucagon

Glycogen Glucose

(Excess) (Normal)

The whole process is summarized in the table below

When the blood sugar (glucose) rises above the normal. When the blood sugar (glucose) drops (falls) below the normal.
– Beta cells produce more insulin and less glucagon

– Insulin causes the liver cells to:

– Convert excess glucose to glycogen.

– Convert excess glucose to fats for storage.

– Increase oxidation of excess glucose to energy, CO2 and water.

– Normal glucose level is restored.

– Alpha cells produce more glucagon hormone and less insulin.

– Glucagon causes the liver to:-

– Convert stored glycogen to glucose.

– Convert stored fats to glucose

– Reduce oxidation of glucose.

– Normal glucose level is restored.

EFFECTS OF HIGH AND LOW SUGAR LEVEL

HYPERGLYCAEMIA

Is a condition which occurs due to failure of pancreas to produce insulin.

HYPOGLYCAEMIA

Is a condition in which glucose concentration in the blood is far much below the normal range of corrective mechanism.

DIABETES MELLITUS

This is a disease caused by a failure of pancreas to secrete insulin or produces little amounts of insulin.

Diabetes mellitus is Greek word means “sweet urine.

TYPES OF DIABETES

There are two forms of diabetes, namely:

i. Type I diabetes

ii. Type II diabetes

i. Type I diabetes

This occurs when the cells from the immune system attack beta cells in the islets of Langerhans making beta cells to produce very little or no insulin at all leading to a glucose build up in the blood.

ii. Type II diabetes

This occurs in adulthood

In this type of diabetes, either the pancreas produces too little insulin or produces adequate amounts but the cells do not respond to insulin causing glucose to build up in the blood.

SYMPTOMS OF DIABETES MELLITUS

– Passing out urine frequently

– A condition of passing urine frequently is called polyuria

– Presence of glucose in the urine

– A condition of passing urine which contain glucose is called glycosuria

– Extreme thirst and hunger

– Weight loss

– Numbness in hands and feet

– Extreme fatigue

– Dry, itchy skin

– Slow healing of wounds

– Blurred vision.

EFFECTS OF DIABETES MELLITUS

i. Coma (becoming unconscious for a long time)

ii. Death

iii. Slow healing of wounds

iv. Lowered body immunity leading to frequent infections.

CONTROL/ TREATMENT OF DIABETES MELLITUS

i. Administration of insulin

ii. Limit carbohydrate intake

iii. Physical exercise.

FACTORS INVOLVED IN THE DEVELOPMENT OF DIABETES

1. Age

Type II diabetes is more common in people aged above 40 years.

2. Obesity

Excess body fat reduces cell responsiveness to insulin. Obesity is a major risk factor for type II diabetes

3. Physical inactivity

Staying idle or doing work that does not require much energy and lack of physical exercise may lead to obesity hence diabetes.

4. Family history of diabetes

People whose family members have had diabetes can be in danger of becoming diabetic.

The Writer