TOPIC 5: REGULATION | BIOLOGY FORM 3
TOPIC 5: REGULATION | BIOLOGY FORM 3
internally in the force of an often harsh and fluctuating external
is the process of controlling the internal body environment and needs.
- Maintaining favorable condition such as pH and required ionic concentration for the functioning of cells, tissues and organs.
- Enabling organisms to get rid of body wastes and useless materials for example excess water and salts
- Enabling organisms to get rid of excess materials for example excess water and salts
- Ensuring survival of the organisms
- Temperature regulation (thermoregulation)
- Blood sugar regulation
- Metabolism of food stuffs
- Absorption of solar radiation
- Convection – This is flow of heat from the interior of an animal’s body to exterior in the surrounding
- Sweating/Evaporation – This occurs when animal loose water vapour from their body surface
- Conduction – This is transfer of heat by physical contact between two bodies
- Breathing out
- Metabolism of food stuff
- Solar radiation
- Contractions of body muscles
- Ectothermic animals example fish migrate to places with a more suitable temperature for them
- Use of shade – snakes, frogs, lizards take shade to avoid being over heated
- Pant – turtles and tortoise pant during hot day to loose excess heat
- Burrow – toads burrow during cold conditions to avoid over cooling
- Bask – snakes, lizards and chameleons bask in the sun to raise their body temperature
- Social behavior – bees cluster together to raise body temperature
- Flex their body muscles e.g. python flex its muscles and coil eggs during cold condition
- Use of metabolic heat – bees contracts their muscles using prior flying in cool weather to raise their body temperature.
animals gain heat only through metabolism of food substances. The
temperature ranges of these animals are as follows:
- Mammals 35oC – 40oC
- Birds 40oC – 45oC
species of endothermic animal has their own optimum temperature during
which metabolic activities occur for example homo-sapiens 36.7oC, House fowl 41oC
regulation in endothermic animals is a physiological process. It is
controlled by hypothalamus and contains two thermo receptors hot and
During hot conditions hot center in the hypothalamus is activated by increase in blood temperature.
Hypothalamus uses nerve impulses and hormones as error signals to activate responses that increase heat loss from the body.
of error signals that activate responses that cause heat loss so that
the core temperature is brought to its set point are:
- Sweating – Sweat glands secrete sweat and sweat pores open. Sweat evaporates at the surface of skin with heat.
– Vasodilation is the increase of size of the blood vessels near the
skin surface so that the heat is lost by radiation as a result of direct
contact of vessels with skin.
- Flattening of body hairs: Hair erector muscles on the surface of the body reduce insulation so that heat loss is simplified.
– This is a process of opening mouths and hanging out of tongue. Dogs
do this process. Panting causes heat loss by evaporation.
of stunt vessels, a process done by whales closing of stunt vessels
directs most of core blood to reach the skin and increase pressure
gradient between the skin and the environment hence heat is lost easily
to the environment
- Shivering is a reflex shaking of muscles. The process results into generation of heat.
of skin hairs: hair erector muscles erect causing the skin hair to
stand and collect air around them which act as insulation for heat loss.
of blood capillaries: Vasoconstriction is a process of narrowing the
blood capillaries leading to the skin. This in turn reduces the
temperature gradient of the body and environment and heat loss
- Opening of shunt vessels, a process done by whales.
Opening of shunt vessels and back to the internal blood circulation. The
process reduces heat loss to the surrounding
- Increase in
metabolic activity. An increase in respiration is affected by an
increase in thyroxin secretion. During cold conditions, hypothalamus
stimulating hormone which in turn stimulates the secretion of thyroxin
hormone which influences fast respiration hence an increase in heat
the thermo-regulating mechanism back down. Positive feedback occurs and
a person goes into a state of hypothermia and suffers heat stroke.
of hair In cold conditions hair erector muscles erect causing the still
hair to stand and collect air around them which acts as insulation for
- Possession of heat under epidermis: fat is a bad conductor of heat, thus prevents heat loss
of narrowing skin blood capillaries: human beings constrict skin blood
capillaries; this reduces the amount of blood passing close to the skin.
This prevents heat loss by convection.
- Ability to shiver:
During cold conditions human beings are able to perform involuntary
muscles contractions, shivering generate heat
of heavy black clothes: During cold conditions human being put on heavy
clothes, examples sweaters and coats. Heavy clothes create layer of air
between the body’s surface and the clothes. Trapped air is a bad
conductor of heat.
- Use f heating systems in houses Human beings
during cold conditions use heating systems of different types to warm
houses so that they can make their living conditions comfortable.
of flattening of skin hair. During hot conditions human beings relax
hair erector muscles these cause body hair to lie flat on the body
surface and reduce insulation so that heat loss is affected
of widening the size of the skin blood vessels During hot conditions
human beings can enter a state of vasodilation where the skin blood
vessels near the skin surface expand. Vasodilation enables excess heat
to leave the body by radiation as a result of direct contact of vessels
with the skin
- Possession of sweat glands Sweat glands secrete
sweat on the body’s surface through sweat pores. Excess heat is lost
when sweat evaporates
- Use of Shade: During hot conditions human beings take cover in shade areas to avoid being over heated
- Wearing of light-white clothes These reduce absorption of heat during hot condition
- Use of air conditioners Air conditioners reduce excess heat in houses
of air Circular muscles near the body surface (between endothermic and
epidermis) Circular muscles near the body surface shunt the blood away
from the body surface during cold conditions then prevent heat loss by
- Possession of bladder (fat layer inside the
epidermis). Bladder acts as a thermal insulator. Bladder controls the
flow of heat from the body core to the body surface. The process occurs
during cold condition
of circular muscles near the body surface (i.e. between endothermic and
bladder) where the animal is surrounded by warm sea circular muscles
open blood vessels near the body surface. This allows an animal to get
rid of excess body heat.
cold conditions squirrels and some bats spend the winter in a state of
dormant state of hibernation in which they appear to be asleep and
during which no food is eaten
takes place in burrows. The temperature of these animals falls below
normal. The chemical activities in the body go very slow using food
stored as fat and glycogen.
is the maintenance of constant internal salt and water concentration in
an organism. OR It is the process by which the osmotic pressure of
blood and tissue fluid is kept constant.
pressure of blood and tissue fluid of an animal is exposed as the
depression of freezing point in relation to the habitat in which the
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. People who are very active might
need more than that.
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
Amount of salt taken into the body 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. Excess salts cause the kidney to
work harder as it is responsible for removing excess salts from the
Hormonal Abnormalities: When less ADH is produced it leads to increased content of water in the blood and vice versa.
Blood sugar regulation:
The hormones found in the pancreas in the Langerhans control regulation
of blood sugar in the body. These hormones are insulin and glucagon.
is the hormone, which is produced from the B-cell. This hormone is
secreted when there is a large amount of blood sugar in the body.
Insulin promotes conversion of blood sugar into glycogen and stored in
the liver and skeletal muscles. Insulin forces the uptake of glucose by
body cells to produce energy.
This is the hormone, which is secreted due to the lower level of
glucose in blood sugar. This Glucagon stimulates liver cells to release
glucose into the blood stream. Glucagon stimulates liver cells to
release glucose into the blood stream.Also Glucagon stimulates
absorption of glucose from the ileum
sugar regulation is the maintenance of a relatively constant blood
glucose level of the body. The end product of digestion of carbohydrate
is mainly simple sugars or glucose.
is absorbed from the alimentary canal active transport into the blood
stream. Hence the blood sugar level in the blood rises to the extent
that regulation of it is necessary.
sugar in mammals is regulated using hormones, which are insulin and
Glucagon. These hormones are secreted by a specialized group of
pancreatic cells called islets of Langerhans. The alpha cells of the
islets of Langerhans secretes Glucagon while the beta cells secretes
the blood sugar level rises in the body insulin is secreted. The
insulin accelerates the entry of glucose into the liver and muscles to
be converted into Glycogen.
is secreted in response to a decline in blood sugar level in the blood
stream. Glucagon promotes the conversion of Glycogen to glucose and
inhibits the oxidation of glucose in the liver.
Skip or forget yourinsulinororal glucose-lowering medicine
Eat too many grams of carbohydrates for the amount ofinsulinyou took, or eat too many carbs in general
Have an infection
Are under stress
Become inactive orexerciseless than usual
Take part in strenuousphysical activity, especially when your blood sugar levels are high andinsulinlevels are low
Fatigue(weak, tired feeling)
Blood sugar more than 180 mg/dL
Slow-healing cuts and sores
Nerve damagecausing painful cold or insensitive feet, loss ofhairon the lower extremities, orerectile dysfunction
Stomachand intestinal problems such aschronic constipationordiarrhea
Damage to youreyes, blood vessels, orkidneys
sudden mood changes
trouble thinking clearly or concentrating
loss of consciousness
you have hypoglycemic unawareness, a condition in which you do not know
your blood sugar level is dropping, your blood sugar can drop so
quickly you may not even have warning symptoms. When this occurs, you
can faint, experience a seizure, or even go into a coma.
low blood sugar is a medical emergency. If you know that someone is
diabetic and he or she is experiencing these symptoms, help him or her
to eat 15 grams of quickly digesting carbohydrate, such as:
a half cup of juice or regular soda
1 tablespoon of honey
4 or 5 saltine crackers
3 or 4 pieces of hard candy or glucose tablets
1 tablespoon of sugar
affects your body’s ability to use insulin.
that unlocks your cells, letting glucose in for energy. People with
diabetes use a variety of treatments to help their bodies use the
glucose in their blood.
you inject too much insulin, your blood sugar may drop too low. People
also sometimes inject insulin when planning to eat a big meal, but then
they do not eat enough.
certain medications, such as quinine
drinking too much alcohol
some medical conditions, such as hepatitis or kidney disorders
a tumor that produces excess insulin
endocrine disorders, such as adrenal gland deficiency
low blood sugar levels are somewhat common for people with diabetes;
however, severely low blood sugar levels can be life-threatening. They
may lead to seizures and nervous system damage. Immediate treatment is
critical. It is important to learn to recognize your symptoms and treat
a medication that raises blood sugar levels, is important. Talk to your
healthcare provider for more information.