Mwl Marco

 REGULATION (HOMEOSTASIS)

Regulation is the way that constant conditions are maintained in the body,despite changes in the external environment,

Homeostasis: is the ability of organisms to maintain internal environment of an organism to be less or more constant.  This enables organs (cells) to function efficiently, hence the body functions normally.

In co-ordination we see how organisms react to internal & external stimuli in order to find optimal living conditions. Regulation deals with the control of the internal environment in organisms.

It makes animals more independent of external environment (being stable in changing environment.

Internal environment

Refers to the immediate surroundings of the cells comprising of tiny fluid spaces(interstitial intercellular or tissue fluid)

External environment

This refers to the immediate surroundings of organism. It may be aquatic (water)  or terrestrial (land)

The organs with homeostatic functions are liver, skin, lungs & kidney.

The ability to control internal environment is best developed in most mammals (humans) and birds. The organs with homeostatic functions in these animals keep the following features of blood & tissue fluid at a fairly constant level i.e. temperature, dissolved substances like Carbon dioxide, Oxygen food (glucose concentration), urea, various poisonous substances and osmotic pressure, PH & water content.

Homeostasis includes excretion: that is the removal of waste products from the body. Waste products are substances arising from metabolic processes which are not needed or which are harmful when they get accumulated in the organism.

Examples of waste products are excess of water, CO2 & nitrogenous compounds (ammonium, urea, and uric acid)

Why regulate internal environment

IMPORTANT REGULATION

i. Maintaining favourable conditions such as PH and  required ionic concentration for functioning of cells, tissues and organs

ii. Enabling organisms to get rid of the cells tissues and organs

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

iv. Ensuring survival of the organism

TYPES OF REGULATION

There are various types of regulation in the animal's bodies. These includes

i.Temperature  regulation(Thermoregulatory system)

ii. Blood sugar regulation

iii.Osmorugulation

1 TEMPERATURE REGULATION

Thermoregulatory system regulates the temperature of the body in responses to fluctuates in the external temperature

The process can be associated with homeostasis which maintained as state of equilibrium where an animal's internal environment remain constant

Hyperthemia This occur when body temperature increase significantly above the normal body temperature

Hypothermia occur when the body temperature drops below the normal body  temperature

Classification of temperature regulation in organism

i.Homeothermic( endotherms)

ii.)Poikilotherm(ectotherm)

Homeotherm animal

These are organisms that are able to maintain constant body temperature even when the surrounding temperature changes

These are birds and mammals that maintain their body temperature within certain limit independent of the external temperature (formerly known as warm-blooded). They are able to counteract fluctuating environmental temperature. They generate much internal heat and have good insulation. The terms warm-blooded & cold-blooded are very general & misleading, therefore unsuitable for scientific purposes.

Why? 

Because on very hot day a cold-blooded might have a higher body temperature than a warm-blooded animal e.g. a lizard sitting on a rock in a hot sunny day might have a higher body temperature than a man sitting on a similar spot.

Temperature regulation in homeotherms

Thermoregulation involves several body system such as nervous, circulatory, endocrine and respiratory..Animal protects themselves from environment changes by balancing heat gain and loses within their environment

When animals produce heat, it is either generated or lost to the environment through four processes which are

1.CONDUCTION.

This involves the direct transfer of the heat between molecules of the environment and the animals.

Example an animal lying on the cooler floor will lose heat on it

2.CONVECTION

Is the process whereby heat is transferred by movement of air or liquid past to the body surface. Example air currents contribute to heat loss from a lizard's dry tail.

3.EVAPORATION

This is loss of heat from the surface of liquid, where molecules escape in form of gas. Some animals and humans have sweat glands that transport watery solutions through pores to the surface of the skin

4.RADIATION.

Involves emission of electromagnetic waves produced by all objects warmer than absolute zero

MECHANISM FOR TEMPERATURE REGULATION

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

Heat loss can be by physiological means and behavioural means

1 PHYSIOLOGICAL MEANS OF BODY TEMPERATURE REGULATION

These physiological means are

i.Insulatory process

This involves regulate the amount of heat gain or loss through physical processes such as, conduction, evaporation 

,convection and radiation. These includes, sweating, hair movement, shivering and alteration of superficial blood vessels

ii. Adaptive processes

These are structural adaptations that regulate the amount of heat gain or loss on long term basis. Example possession of fur in mammal and a thick layer 

of subcutaneous fat, for animal living in the cold weather, and feathers in the birds that provides insulation

iii.Metabolic processes.

Metabolic reactions taking place in the body produce heat through the process of the thermogenesis

RESONSE TO HOT WEATHER

  1.  Sweating: is the production of water fluid containing dissolved salt from sweat glands in the skin. Evaporation of sweat is an extremely efficient cooling mechanism.

-   Sweat evaporates and its effectiveness in cooling the body depends on:

·         Humidity = amount of water vapour in the air.

·         Air movement = wind and fans.

·         Sweat evaporates and cools the body very rapidly in hot, dry, and windy conditions.

·         Temperature above 41ºC will lead to coma and convulsion. this is called heat stroke i.e. collapse & death.

·   In hot climate vigorous exercise may cause loss of up to 3 litres of water & 30 grams of salt per day. So it causes blood to be thick & concentrated (not able to circulate properly). Loss of salt causes muscle pains (heat cramp)

· So in hot climate a person must drink a lot of water and increase amount of salt in his diet.

  2. Panting: Animals of the dog family have sweat glands only in the pads of their paws. Their main method of loosing heat is to pant rapidly with the tongue hanging outside. This causes evaporation saliva from  tongue in mouth and cools the body.

Figure.panting in dog

3.      Vasodilatation of arterioles superficial capillaries below the skin become wide so that more blood flows to the skin surface. Heat is lost through the skin surface, that’s why the 

skin feels

4. Relaxation of hair erector muscles: hence hair lies more or less flat against the skin, so heat is easily lost by radiation and convection.

5.Decreased metabolic rate.When metabolic rate decrease, less heat is generated. and therefore the body temperature falls.Fr this reason homeotherms are sluggish during hot weather

RESPONSE TO COLD WEATHER

1.Increase in Metabolic rate. 

Through metabolism in the liver and muscles i.e. respiration = breakdown of food to produce energy/heat.Through vigorous exercise which also increase the rate of respiration.

 In cold weather rate of metabolism increases and hence increase appetite for food; increase food output

2.    Shivering: is heat production process in which skeletal muscles are stimulated into uncontrolled activity. These muscles use up the metabolites and produce heat.

3.    Contraction of hair erector muscles: hairs are raised to make a thick coat thus trapping more air as an insulating layer. The contracted hair muscles in naked skin appear as “goose pimples.”

-  Also the upright hairs prevent the cold winds from reaching the skin.

- Birds achieve a similar effect by means of muscles, which makes their hair fluff out.

4.. Vasoconstriction: capillaries below the skin become narrow so that less blood flows through the skin and less heat gets lost through radiation. The skin looks pale.

 Air is trapped between the hair, forming an insulating layer between the skin and the surrounding

2 BEHAVIOURAL MECHANISM OF TEMPERATURE REGULATION IN HUMANS

During hot weather	During cold weather
Moving to shaded places	Moving to wamer places
Wearing light clothes	Wearing warmer clothe
Taking cold beverages	Taking hot beverages
Swimming or taking cold shower	Baking in the sun or seating near a fire
Fanning using manual or electric fan	Using warming systems in the house
Using air conditioners	Exercising
Building houses with large window	Building houses with air spaces

Advantages of homoiotherms:

-Allow animals to exploit wide range of geographical habitats.

-Independent of external temperature.

-Enzyme- controlled reaction proceeds efficiently at optimum body temperature.

-Have high metabolic rate.

-Are active throughout.

-Can respond to faster and move faster.

-Have great survival value.

Disadvantages of homoiotherms:

-High food consumption for generation of internal temperature: - metabolically expensive.

-Animals use food of high calorific valopue such as fat to keep warm especially in the cold season.

-There is a danger of overheating in tropical and desert areas: hence need of efficient means of controlling heat loss/gain by the body.

Aquatic poikilotherms: water temperature does not fluctuate rapidly and water has a high specific heat capacity. So aquatic poikilotherms have little problems compared to those on the land.

Terrestrial poikilotherms: on the land the air temperature can change rapidly over a wide range.So terrestrial poikilotherms achieve some measure of temperature control by means of their behaviour.

E.g.: Some borrow the land and live there.

Some expose themselves to the sun according to their needs (nocturnal)

These help them to avoid the extremeness of temperatures, which would interfere with their metabolism.

TEMPERATURE REGULATION IN ANIMALS LIVING IN VERY COLD CLIMATE

Animal living in very cold climate such as polar bear have the danger of suffering hypothermia. Therefore their adapted to avoid heat loss such as

i.Thicker hair which is better in holding air around the body thus act 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 shapes compared to their counterparts living in hot or temperate climate

-Large bodies means small surface area to volume ratio thus reduced heat loss

Figure.polar bear

Normal bear has small body

Temperature of poikilotherms depends on different factors: -

1.      Amount of heat produced in its body by metabolism.

2.      The heat, which it receives & looses by radiation from the sun and near objects i.e. rocks.

3.      The heat, which it receives & looses by conduction with object touching it.

4.      The heat, which it receives & looses to the air.

5.      The heat, which it receives & looses by evaporation of water from its skin.

Adaptation to cold climate:

Mammals, which live in very cold environments, are insulated by a thick layer of sub-cutaneous fat. The body shapes & sizes increase the ability to conserve heat, i.e. smaller surface area to volume ratio e.g. rounded bodies of whale, seals & polar bears which consists of thick thermal shell enclosing a substantial core.

Other animals without such adaptation can’t survive the coldest season unless they migrate or hibernate.

Hibernation: Is a state of sleep and greatly reduced metabolic rate, (reduce energy needed) that enables certain mammals to survive prolonged periods of low temperature & food scarcity e.g. hedgehog, rodents & bats.

Causes of hibernation: changes in day length & climate trigger hormonal changes, which slow down metabolism & lead to hibernation.

-In some species hibernation is striggered by an environmental stimulus such as food shortage. In certain cases hibernation is usually proceeded by extra feeding & the lying down of fat stores in the body. Small animals are prone to hibernate as they have a high basal metabolic rate and few food stores.

Small animals, Small birds (humming birds) and smallest mammals (shrew) have particular problems in maintaining high body temperature due to their large surface area to volume ratio, since they can’t carry thick insulation.

-Addition metabolism is necessary to produce required heat.

Young mammals: include newly born baby, have regions of special adipose tissue known as brown fat. These fats involve the rapid production of heat by special metabolism of free fatty acid; these pads of brown fat are also found in some hibernating animals.

Adaptation in hot climate.

Very few organisms can tolerate wide range of temperature like in the desert (0ºC-midnight to 55ºC at noon). Most desert animals survive by restricting their activities when conditions get less extreme e.g. kangaroo rats spend most of their day in deep burrows where temperature stays approximately constant.
Large animals like camels have thick non-wettable fur that is pale coloured to reflect heat and allow water to evaporate from their skin surface so that cooling occurs.

Surface area: elephants have large ears to increase surface area for evaporation. Ears are important sites for heat exchange.

Therefore changes in body colour and body size with climate is one of the adaptations to hot climate.

Human beings adopt different climate with type of clothes and food.

Aestivation: is a period of inactivity in some animals during summer or hot dry season e.g. fish, amphibians & reptiles who inhabit fresh water e.g. lugfish burying themselves in mud bottom at dry season and reactive as water return.

Advantages of poikilotherms

-Organism  can regulate behaviour pattern to regulate body temperature.

-Low food consumption as they do not generate heat internally for temperature control.

-Organism can go in hibernation when the need arises.

-Insect larva have diapause (dormancy period) to avoid hostile temperature conditions.

Disadvantages of poikilotherms

-Low metabolic rate, therefore sluggish when external temperature are low and can be preyed upon easily.

-Depend too much on external temperature to react to external stimuli.

-When temperature are too low they go to hibernation and possibly leading to death.

2.OSMO-REGULATION IN MAMMALS
Is the regulation of concentrations of water and mineral salts in an organism.
or

Is the control of osmotic pressure within an organism. Blood and tissue fluid must be kept at a constant  osmotic pressure to avoid unnecessary movements of water in and out of cells by osmosis.
Water and mineral  salts serve various physiological functions in the animal;s body.For proper functioning the amounts of water and mineral salts need to be maintained at a constant level.

-Osmoregulation prevents the cells from bursting or shrinking.

Osmosis is the movement of a solvent from a dilute solution to a more concentrated solution through a membrane.

The water content and dissolved substances such as mineral salts in the cells must be controlled, ie. Control of osmotic concentration within an organism. If the osmotic pressure of blood and tissue fluid is too high, cells lose water by osmosis and the body becomes dehydrated.

The osmotic pressure of a solution depends upon its strength, ie, amount of dissolved substances it contains. Example osmotic pressure of a sugar solution increases with addition of sugar in it.

So osmoregulation is especially important in animal cells as they do not posses the strong cellulose cell walls found in plant cells.

MECHANISM OF OSMOREGULATION
The regulation of osmotic pressure is controlled by hormone called Anti-duretic hormone(ADh).This is produced in the pituitary gland and protects the body against excessive water loss.
-When the amount of water in the body falls, leading to a rise in osmotic pressure. The pituitary gland releases ADH into the bloodstream.When it reaches the kidneys it increases the reabsorption of water from convulated tubules and collecting ducts into the capillaries surrounding the tubules.This returns the water balance to normal
-When the osmotic pressure in the blood falls, due to a low concentration of salts ions, particulary sodium and chlorides ions another hormone Aldosterone is released from the adrenal glands into the blood stream.This hormone stimulates reapsorption of sodium and chloride ions from the kidney tubules and loop of Henle

Kidney: Are the organs associated with osmoregulation. They control the rate of osmosis between the blood plasma and the surrounding cells.

The body gain water by eating and drinking, and it loses water by urine, faeces (defacation), sweat and exhaled breath. This will produce corresponding changes in the blood concentration. The Hypothalamus in the brain will detect such changes and try to balance it. Failure in liver-insulin mechanism will also alter blood concentration.

If the blood is too concentrated, the hypothalamus will stimulate the pituitary gland to secrete into the blood the ADH (anti diuretic hormone) which causes the kidney tubules to absorb more water from glomerular filtrate back into the blood. Thus the urine is more concentrated, (Hypertonic Urine) and the further loss of water from the blood is reduced.

If the blood is too diluted, production fo ADH is suppressed and less water is absorbed from glomerular filtrate, thus urine is more diluted (Hypotonic Urine.) as means of eliminating excess water in the body.

Important roles of the kidney.

Without kidneys life is not possible. Single kidney can suffice the work. Kidney failure is caused by severe infection, low or high blood pressure.

Functions of the kidney

-Control the acid-alkali balance, (It maintain blood plasma at PH of 4)

-Maintain exact proportion of water in the blood.

-They expel salt above certain concentration, ie.  They regulate the osmotic pressure of the body fluids by regulating the concentration of salts in the blood.

-Regulate total volume of blood.

-expel (excrete) harmful waste matter from the body , ie. Urea.

-Help to conserve body’s  water supply so that more is available for perspiration (cooling by sweating), in hot weather. ie. Little but very concentrated urine.

-Over a ton of blood is filtered through kidneys in 24 hours.

Diagram of kidney tubule(nephrone).

Camels and scarcity of water.

Figure .Carmel with hump.

The camel is the mammal with the longest loops of Henle, this helps it to conserve salt ions,which in turn increases the rate of water reabsorption in the kidney tubules and helps it to conserve water

Camels do not store any water in rumen. The fat hump is not so useful for it does not provide any water, because oxidation of fat leads to respiratory loss of moisture.

Camels are able to survive in the desert because:-

-They excrete small volume of urine which is more concentrated, (more hypertonic) than human urine. So high tolerance of water scarcity.

-They lose very little water in their sweat, (only when their body temperature rises more than 56 C.)

-Can survive even after losing ¹/₃ (one third) of their body weight due to loss of water. Man dies if he/she loses ¹/₅ of the body weight due to loss of water.

BLOOD SUGAR REGULATION.
Several mechanism involving nervous, hormonal and metabolic pathways are used to maintain a constant blood glucose level. The liver, together with a set of glands in the pancreas, control with great accuracy the amount of glucose sugar in the blood. The liver is unique in vertebrates and plays a key role in their metabolism.

MECHAINISM OF BLOOD SUGAR RGULATION.
The regulation of blood sugar is controlled by two hormones. INSULIN and GLUCAGON. These hormones are produced by  Islets of Langerhans
When there is excess glucose in the blood, the islet's of Langerhans produce more insulin and less glucagon.Insulin stimulates the liver cells to lower blood glucose level by conversion of excess glucose to glycogen and fats for storage, also by increased oxidation of glucose to provide energy
When glucose level in the blood falls the islets of Langerhans produce more glucagon and less insulin.The glucagon stimulates the liver cells to convert stored glycogen and fats to glucose and to reduce respiration of glucose to energy.The blood glucose level is then raised back to normal

Figur.e Antoagonistic action of Insulin and Glucagon hormones

Why maintain constant body’s sugar level.

-Sugar is the main source of energy in the body.

-Any slight changes in glucose concentration alter the blood’s osmotic pressure, and hence alter the rate at which water moves in and out of body cells by osmosis.

-When blood glucose is depleted faster than it can be replenished, it drops gradually resulting in Hypoglycaemia. This causes fatigue and affects the functioning of the brain, since the blood glucose is the only source of respiratory substrate in the brain.

Therefore, is important for the normal functioning of the body cells.

What increases blood sugar level.

Normal level of glucose in man’s arteries is 85 mg/100cm³. After a heavy meal of carbohydrates it may rise to 180mg/100cm³. Normally it does not fall below normal except during prolonged starvation.

CAUSES, SYMPTOMS AND EFFECTS OF HIGH AND LOW BLOOD SUGAR LEVEL.
1. HYPOGLYCAEMIA.(Low blood sugar)
Is a condition in which the level of glucose in the blood is abnormally low.
CAUSES
It can be caused by the following drugs, hormone deficiencies, tumours. organ failure like kidney,liver and gastrointestinal surgery
SYMPTOMS
The brain is the first organ to feel the effects of hypoglycaemia
signs and symptoms.headachesor dizziness trembling, blurred vision, depression, anxiety, fequent hunger
FFECTS
An in adequate suplly of glucose can effects in impairment of body function

2.HYPERGLYCAEMIA(HIGH BLOOD SUGAR)
Is chareacterized by too much glucose circulating in the blood
Causes
It caused by diabetes, obesity or eating disorders
Symptoms
-Frequent, hunger , thirst and urination,blurred vision. fatique, poor of wound. dry mouth.dry or itchy skin .importency
Effects
The increasedlevel has been linked to increase cerebral lactate
-promote oedema
-caues stroke
-Impairing their cerebrovascular brain reactivity
3. DIABETES MELLITUS
This occur when pancreas can not insulin and cause glucose is contained in the urine, ie. Blood sugar is high

Symptoms.
i. Frequent urination
ii.Extreme thirst and hunger
iii. weight loss
iv.slowing healing of hunger
v.Numbness in hands and feet
vi. Dry, itchy skin
vii. blurred vision
effects
-comma(becoming unconscious for a long time even die
Treatments
This can be treated by injection of insulin and a carefully regulated diet

OSMOREGULATION IN PLANTS.

Plants need less energy compared to animals because they do not move around, hence produces less heat and loose less water. The problem of plants is the absorption of heat from direct sunlight for photosynthesis. Leaves have a large surface area exposed to sun. Direct sunlight can cause temperature rising of leaves up to 50 degrees centigrade.

Terrestrial plants take up water mainly with their roots and leaves. Water is lost by transpiration through stomata pores, the lentils (in the bark) and cuticle of stems & leaves. Water loss is mainly regulated by the opening or closing of the stomata spores.

Factors affecting osmoregulation in plant are light, temperature and air humidity, wind, surface area.

Ways of controlling temperature in plants:

- Wilting- decreases the surface area of the leaves exposed to the sun, hence controls temperature.

-  Transpiration: lowers temperature, although maximum effect rarely exceeds 5 degrees centigrade.

-  In some plants, stomata open with increase ambient temperature.

-  Stomata closure to conserve water results into increase in leaf temperature.

-  Some desert plants avoid adverse conditions by completing their life cycle during short rainy seasons and passing the rest of the year as fruits or seeds that lie dormant in the soil.

-  Other plants survive the dry months underground perennating organs like bulbs, corms, tubers or fleshy roots.

-  Presence of special water- storage tissues, e.g.: succulents plants in the arid areas (xerophytes).

-  Presence of transpiration checks to reduce transpiration, e.g. leaves with a thick cuticle, stomata sunk in pits and leaves rolled with stomata on the inside.

-  Physiological draught:

*The high salinity of water surrounding halophytes makes it difficult for them to take in water by osmosis

· In temperate regions during winter water freezes:

-Many herbaceous plants avoid winter conditions as seed or peranneting organs.

-  Deciduous trees and shrubs shed their leaves to stop transpiration.

-  Conifers reduce transpiration by adaptations that is reduced leaf surface and the presence of a thick cuticle on leaves.

-  In cases where an excess water accumulates in a plant, a special water – expelling glands called hydathodes may occur.

Note: A continuos flow of water must be maintained to meet the plant’s needs of transport and structural support.

Plants types (groups) as modified for water conservation

1) Hydrophytes:

-          Plants growing sub merged under water or floating on water or in very wet soils. That is low minerals, less light, water waves and currents, low concentration of dissolved gases.

*Submerged:

Have soft roots to absorb mineral salts.

Tissues are soft and weak with air spaces to keep the plants floating.

Leaves are thin ribbon like with chloropast but no stomata

Some have spores in epidermis called hydathodes for the secretion for water, e.g. hydrilla

*Floating:

Have soft bush like roots, which absorbs water through the entire surface.

Big leaves which floats on water to receive sunlight.

Have stomata on the upper side to transpire water,. e.g. pistia.

 2) Halophytes:

-          Plants growing the sea shore. They absorb water against the osmotic gradient that is high salt concentrate.

·         Adaptation:

-          Have still roots for support and breathing roots to absorb oxygen from the atmosphere, eg. mangroves with roots called pneutomato phores.

-          The seed germinate while still on the parent plant to avoid suffocation of lack of air.

3) Meseophytes:

-          plants growing in moderate areas that is moderate water supply, enough air and mineral salts, e.g. garden plants, shade loving herbs and large forest trees.

Adaptation:

-          Well developed root system, large thin leaves with chlorophyll, and have most stomata on their lower surface

-          Grow tall to compete for light.

4) xenophytes.

-          Plants growing in areas with scarcity of water (drought).

-          Strong winds, high day temperature and very low night temperature.

*Adaptation.

-          Well developed root system often extensive, grow deep and branch in all direction hence large absorbing surface area.

-          Some have fewer and smaller leaves; some cases are reduced to pines or hairs which reduce surface area for water loss.

-          Some have rolling and folding leaves, e.g. Marram grass.

-          Some have waxy leaves.

-          Some have sunken stomata with hair above to reduce water loss.

-          Some have stems covered with cork to prevent evaporation.

-          Some have succulent stems and leaves consisting  of parenchyma cell which store water, eg. of succulents are sisal and cactus.

-          Very few stomata to minimize water loss