Homeostasis Part 1 Lecture Notes PDF

H O M E O S T A S I S P A R T 1 Mohamad Razif bin Othman PRH 1016  Imagine this.. Imagine driving on this seemingly endless road. Hopefully, your imaginary car is equipped with cruise control. Cruise control can help keep you safe as well as help y...

H O M E O S T A S I S P A R T 1 Mohamad Razif bin Othman PRH 1016  Imagine this.. Imagine driving on this seemingly endless road. Hopefully, your imaginary car is equipped with cruise control. Cruise control can help keep you safe as well as help you avoid a speeding ticket by keeping the speed of the car at the speed limit. Cruise control works by monitoring the car’s speed and adjusting the throttle as needed to keep the speed within a narrow range around the set speed limit. If the car starts to go faster than the set limit, it causes the throttle to release less gas until the speed drops back down to the setpoint. The opposite happens if the car’s speed starts to fall below the set speed limit. Cruise control on a car is a good analogy for physiological mechanisms that maintain the human body in a steady state HOMEOSTASIS 2  Define homeostasis as the maintenance of a constant internal environment Learning Explain the basic principles of homeostasis and the maintenance of : Objectives Regulation of body temperature Regulation of blood glucose concentration Regulation of body water & electrolyte balance 3  Definition From the Greek, Homeo means “same” and -stasis meaning “standing still” A physiological process: maintenance of a relatively stable internal environment: a characteristic of many organism esp. higher vertebrates 11/6/2024 4  Claude Bernard (1850s) French Physiologist Established that multicellular organisms have an internal environment that can be modified to maintain cellular function An organ can modify the composition of blood. The “milieu interieur” could be maintained Example: the liver can secrete glucose into the blood; raising blood glucose levels if glucose levels should fall 11/6/2024 5  Need for homeostasis Conditions outside our body are changing all the time. But conditions within our body must be kept constant e.g pH and body temperature. Why? 11/6/2024 6  Need for homeostasis Why does body temperature have to be kept constant? Ensure that enzymes do not get inactivated or denatured since enzymes only work within a certain temperature range Why must tissue fluid be kept at a constant pH and water potential? Change in pH affects enzyme reactions in the cells Change in water potential affects the cells (cells can be crenated or burst) 11/6/2024 8  Benefits of Homeostasis Enables organism to live in a wider variety of habitats Able to control their own metabolic needs Enables a more efficient & economical metabolic reactions Less dependent on their environment 11/6/2024 9  Parts in your body that need to be kept within a range:  Body Temperature  Blood pressure  Blood pH  O2 and CO2 concentration  Osmoregulation-Water balance  Blood glucose 11/6/2024 10  How is Homeostasis achieved? A stimuli which is a change in the internal environment A receptor which can detect the stimulus An automatic or self-regulatory corrective mechanism (regulator), which brings about changes through the effector (organs/tissue that is involved in bringing about the change) A negative feedback as response 11/6/2024 11  Negative Feedback - Homeostatic control involves a principle called negative feedback - E.g. water potential of blood increases above normal (stimuli), it is detected by osmoreceptor (detector). - Your body respond by returning the water osmolality back to the normal condition. 11/6/2024 12  Negative Feedback That is, the body always reacts to bring about an opposite effect to changes If the system is disturbed, the disturbance sets in motion a sequence of events that tends to restore the system to its original state, this is known as the negative feedback process Negative feedback is most common in biological systems 11/6/2024 13  Negative Feedback Humans require the interaction of multiple systems to maintain homeostasis. The organs and systems of the human body help to provide all of the cells with their basic needs. 11/6/2024 14  R E G U L A T I O N O F B O D Y T E M P E R A T U R E  The Mammalian Skin Main organ involved in body temperature regulation Functions: o Protective covering o Excretory organ o Regulator of body temperature Any change in the temperature of the surroundings can be detected by the skin 11/6/2024 16 11/6/2024 17  Functions of the different skin parts Blood vessels to bring oxygen to the cells in the skin. The arterioles can dilate or constrict to regulate the amount of blood flowing through the skin. This helps to regulate body temperature Sweat glands produce sweat which can help to cool down the body temperature Hair can help to trap air to insulate the body 11/6/2024 18  Functions of the different skin parts Nerve endings (temperature receptors/ thermoreceptor s Detect changes in temperature of the external environment Fatty/adipose tissue Stores fat and serves as an insulating layer, preventing heat loss 11/6/2024 19  Heat Production and Heat Loss Heat is produced in the body: Due to metabolic activities (e.g. tissue respiration). Esp. in liver and muscles whereby lots of heat are produced in these organs Extra heat in human is gained by eating hot food, from the sun, warm air, by exercising 11/6/2024 20  Body Heat Loss Occurs in 2 steps: Conduction of heat from the deeper organs and tissues to the skin Transfer of heat from the skin to the surrounding through: Radiation Conduction Evaporation – 27% Convection - 2% Urination & defecation - 1% 11/6/2024 21  How is temperature controlled? Body temperature is monitored and controlled by temperature receptors in the skin and brain. These receptors detect changes in the temperature of blood flowing through those areas. The thermoregulatory centre in the brain is called the hypothalamus. If body temperature deviates from 37 °C, the hypothalamus and skin receptors send out electrical signals that trigger actions or behaviours that increase or decrease heat loss. 11/6/2024 22  Regulation of Body Temperature Hypothalamus in the brain Monitors and regulates the body temperature Receives information about the heat changes in the external environment from the temperature receptors in the skin Monitors the temperature of blood that passes through it Hypothalamus set point: usually maintain at 37.5 ± 0.5 °C 11/6/2024 23  Temperature Regulation Several thermoregulatory responses take place, if body core temperature either increase above or decreases below almost exactly 37oC, to bring it back to this temperature Temperature regulating mechanisms Autonomic: vasodilation, vasoconstriction of blood vessels Somatic: shivering Endocrine: through hormones thyroxine, adrenaline Behavioral changes: clothing, movement 11/6/2024 24  R E G U L A T I N G B O D Y T E M P E R A T U R E O N A H O T D A Y  Regulating Body Temperature On a Hot Day 11/6/2024 26 11/6/2024 27  Blood vessels regulation 11/6/2024 28  Sweat production regulation 11/6/2024 29  Hair follicle regulation 11/6/2024 30 11/6/2024 31  R E G U L A T I N G B O D Y T E M P E R A T U R E O N A C O L D D A Y 11/6/2024 32 11/6/2024 33 11/6/2024 34  Blood vessels regulation 11/6/2024 35  Sweat production regulation 11/6/2024 36  Hair follicle regulation 11/6/2024 37 11/6/2024 38 11/6/2024 39  Failure of Temperature Regulation Hypothermia Defined as core body temperature of less than 350C. Hyperthermia Abnormally high body temperature due to failure of temperature regulation 11/6/2024 40 REGULATION OF BLOOD GLUCOSE 11/6/2024 46  Regulation of blood glucose 2 main organs involved: Liver & pancreas Liver: a storehouse for glycogen 2 hormones are responsible for controlling the concentration of glucose in the blood, secreted by islets of Langerhans in pancreas: Glucagon: secreted by Alpha cells Insulin: secreted by Beta cells 11/6/2024 47  Glucose Homeostasis Hormones action: Insulin - promotes the conversion of glucose into glycogen (glycogenesis), where the excess glucose can be stored for a later date in the liver Glucagon - promotes the conversion of glycogen into glucose (glycogenolysis), where the lack glucose can be compensated for by the new supply of glucose through breakdown of glycogen 11/6/2024 48  Glucose Homeostasis The hormones target the liver, one or the other depending on the glucose concentration In cases where glucose levels increase, less glucagon and more insulin is released by the pancreas and targets the liver In cases where glucose levels decrease, less insulin and more glucagon is released by the pancreas and targets the liver 11/6/2024 49 11/6/2024 PRESENTATION TITLE 50 11/6/2024 PRESENTATION TITLE 51  Failure of blood glucose regulation Normal fasting blood sugar: 4-6 mmol/L High blood sugar (Hyperglycaemia) Condition in which an excessive amount of glucose circulates in the blood plasma Associated disease condition: Diabetes mellitus Low blood sugar (Hypoglycaemia) An abnormally low level of sugar in the blood Can cause serious complications: seizures/fit; loss of consciousness or coma, death 11/6/2024 52  E N D O F PA R T 1 11/6/2024 55