HomeostasisBy: Luke Richmond Alicia Liek Zhong

Homeostasis• Homeostasis is the maintenance of a constant

internal environment (conditions within the body) i.e. blood and tissue fluids.

• By ensuring the conditions are kept constant, we remain relatively unaffected by our surroundings i.e. pH level, temperature.

Why is homeostasis important?•Body temperatureTemperatures outside are constantly changing body but our body cells have

to remain constant because enzymes in our body can only work within a specific temperature range. Changes in body temperature might result in enzyme inactivation or denaturisation

•pH and water potentialA drastic change in pH of tissue fluid will affect enzyme reactions in our cells

and harm our body. Drastic changes in tissue fluid will also affect our health.

Hence, homeostasis is extremely important to our body!!

Negative Feedback•If the system of our body is disturbed, the disturbance sets in motion a

sequence of events to try to restore the system, in this case, our body to its original state. This process is negative feedback.

• When organs or structures in out body detects a change in the body condition, it will trigger a corrective mechanism to bring about the changes to restore the body to its normal condition.

When does negative feedback happen?

•In a negative feedback loop, the must be:

● A normal point/set-point to be maintained

● A stimulus , which is a change in the internal environment

● a receptor to detect the changes

● a corrective mechanism to bring about the reverse effects of the stimulus

● a feedback to the receptor when the set-point is reached which causes the corrective mechanism to stop

Thermoregulation• One of the most important example of homeostasis is thermoregulations

• As the name suggests, thermoregulation is the regulation of body temperature. It cool down the body when it is too hot or warm the body up when it is too cold.

• The body temperature is controlled by hypothalamus in the brain and it receives input from two receptors: one in the hypothalamus itself to control blood temperature as it passes through the brain, monitoring the core temperature; the other one is the receptors in the skin, monitoring external temperature

Thermoregulation

Thermoregulationthe body gains heat through:

• vigorous muscular exercise

• the consumption of hot food

• being in warm environmentand heat is lost:

• Through skin by radiation, convection and conduction

• by evaporation of water in sweat from the surface of the skin

• in faeces and urine

• in the air that is exhaled.

Thermoregulationwhat happen when temperature of the body rises?• When body temperature begins to rise, the body must be cool down

• This can be achieved by:

• widening of the arterioles and narrowing of the shunt vessels in the skin to allow more blood to flow through the blood capillaries, allowing heat in the blood to be lost to the surrounding by conduction, convection and radiation.

• producing more sweat in sweat glands. As sweat evaporates,there’s cooling effect and reduces amount of heat in the body

• reduce metabolic rate, to reduce amount of heat released within the body.

Thermoregulationwhat happen when the temperature falls?• arterioles narrow and shunt vessels widen to allow less blood to flow

through the skin, preventing heat lost to surroundings.

• produce less sweat, less heat is lost through evaporation of water through the skin.

• increase metabolic rate to increase amount of heat released within the body

• ‘Shivering’ occurs. This increase the amount of heat released and helps to raise the body temperature to normal.(Muscles shaking produces a lot of heat)

Blood glucose concentration• body cells need glucose for respiration, which release energy to perform

vital activities.

• DRASTIC CHANGE IN BLOOD GLUCOSE CONCENTRATION CAN BE DANGEROUS AS IT MIGHT RESULTS IN DEATH!!

• blood contain normally about 0.8 – 1g per dm3

• Glucose level rises after sugary meal and fall after a vigorous exercise or starvation.

Blood glucose concentration

Blood glucose concentrationwhen blood glucose concentration rise above the normal level, the following

events take place:

• blood glucose concentration rises become a stimulus(a change)

• The stimulus activates the receptor, the Islets of Langerhans in the pancreas.(produces hormones)

• the receptor send impulses to the corrective mechanism, and releases hormone insulin from the pancreas into the bloodstream.

• Insulin increases the rate of absorption of glucose into the cells.

• At the same time, insulin also cause liver to convert glucose into glycogen and stored in the liver.

• Thus, the concentration of blood glucose decrease and go back to normal.

Blood glucose concentrationWhen blood glucose concentration falls below normal level:

• Blood glucose falls below normal level is the stimulus.

• it stimulates the receptor, Islet of Langerhans in the pancreas.

• the receptor sends impulses to the corrective mechanism, Islet of Langerhans secrete hormone glucagon into the bloodstream.

• Glucagon causes the liver to convert glycogen stored in the liver into glucose and then release glucose into blood stream.

• Thus the concentration of glucose in bloodstream increases and go back to normal level.

Blood Pressure• The approximate blood pressure is 120/80mm Hg

• Factors affecting blood pressure are-Heart rate-Size of blood vessel lumen(pathway for blood to travel)-Water balance-Temperature-Metabolic rate-Breathing-Detoxification-Hormones-Blood sugar level-Disesases

Blood Pressure• There is a mechanism maintaining the blood pressure

• The kidneys release renin into the bloodstream, which interacts with angiotensin.

• Angiotensin causes the blood vessels to narrow, and releases aldosterone.

• Aldosterone increases the amount of water and sodium absorbed by the kidneys, leading to an increased amount of salt and water in the bloodstream.

• These activities by this mechanism causes the blood pressure to rise.

• Likewise, the mechanism causes the kidneys to release less renin when the blood pressure is too high.

• An imbalance in the human body due to homeostasis include-Gout-Acidosis-Diabetes-Infections-Poisoning-Hypoglycemia-Hyperglycemia

Medical Conditions

Medical Conditions• Gout• Due to increased uric acid in blood(hyperuricemia).

• Uric acid is produced by purines breakdown, which are found in many foods

• Painful in big toe

• Acidosis• Due to high pH levels in body.

• Caused by increased acid or loss of bicarbonate

• Can cause kidney failure or shock.

Medical Conditions• Diabetes• Increased levels of blood sugar level in blood(lack of insulin)

• Hypoglycemia• Abnormally low blood sugar levels

• Hyperglycemia• Abnormally high blood sugar levels

• Commonly caused by diabetes