Unit 2 Homeostasis

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Negative feedback systems maintain homeostasis by producing a response that is the opposite of the original change. Negative feedback decrease the original stimulus

Homeostasis refers to the body’s maintenance of internal environments within tolerance limits despite stimuli from the external environment

Osmotic pressure refers to the tendency of a solution to take in the pure solvent Simply put, Osmotic pressure is determined by the concentration of substances dissolved in the water of the blood plasma.

Excretion - removal of products of metabolism Eliminations - removal of undigested food

Positive feedback has no role in homeostasis. When it occurs, the response to a stimulus reinforces and intensifies the stimulus

The intensified stimulus results in an even greater response, it does this through the nervous and endocrine system

Childbirth Blood clotting

Thermoregulation Blood glucose regulation Gas concentration regulation Bodily fluids regulation

A chemical process in which oxygen is used to make energy from carbohydrates. Formula; C6H12O6 + 6O2 → 6CO2 + 6H2O

Carbon dioxide is carried in the blood plasma as hydrogen ions

– Neo = New – Genesis = Creation – Lysis = Breakdown of cell – Lipo = fat

Thermoregulation refers to the regulation of body temperature; the balance of heat gain and heat loss in order to maintain a constant internal body temperature independent of the environmental temperature

○ The STIMULUS is the change in the environment that causes the system to operate ○ The RECEPTOR detects the change ○ The MODULATOR is a control centre responsible for processing information received from the receptor and for sending information to the effector ○ The EFFECTOR carries our a response counteracting or enhancing the effect of the stimulus ○ FEEDBACK is achieved because the original stimulus has changed by the response

Stimulus - Increase in body temperature Receptor - peripheral thermoreceptors are stimulated sending info to the hypothalamus Modulator - The hypothalamus responds through the effector Effector - *Vasodilation of skin areterioles occur * Sweating occurs * Behavioural response occurs * In the long term, can be a decrease in metabolic rate Response - * Vasodilation causes an increase in blood flow through the skin, with the surface temperature rising causing heat loss through convection *Sweat evaporates having a cooling effect *Decrease in metabolic rate causes less heat to be produced in the body Feedback - body temperature decreases

Stimulus -decrease in body temp Receptor - peripheral thermoreceptors are stimulated sending info to the hypothalamus Modulator - Hypothalamus activates the effectors Effector * Skeletal muscles cause shivering * Vasoconstriction of skin blood vessels * Adrenal medulla secretes adrenaline and noradrenaline increases cellular metabolism * Pituitary gland releases TSH which causes the thyroid to release thyroxine into the blood * Behavioural change Response * Shivering increases heat production * Vasoconstriction causes a reduction in heat loss * Increased metabolism causes the body to produce more heat * Thyroxine increases metabolic rate, which increases the heat produced Feedback - body temperature increases

Stimulus - Increase in blood glucose Receptor - chemoreceptor detects increase in blood sugar sending information to the hypothalamus Modulator - Hypothalamus activates the liver, adrenal glands and pancreas Effector * Pancreas secretes insulin and glucagon through alpha and beta cells. Insulin causes a decrease in blood glucose levels * Liver converts glucose to glycogen for storage through the process of glycogenesis Response * Insulin causes a decrease in blood glucose levels * Liver causes the glucose to be used for storage Feedback - Decrease in blood glucose

Stimulus - Decrease in blood glucose Receptor - chemoreceptors detect decrease in blood sugar sending information to the hypothalamus Modulator - Hypothalamus activates the liver, adrenal glands and pancreas Effector * Pancreas secretes glucagon through alpha cells. Glucagon causes an increase in blood glucose levels * Liver converts glycogen to glucose for use through the process of glycogenolysis Response * Glucagon causes a decrease in blood glucose levels * Liver causes the glucose to release into the blood Feedback - Decrease in blood glucose

Stimulus - increase in bodily fluids Receptor - Osmoreceptors in the thirst centre of the hypothalamus detect an increase in plasma volume and decrease in osmotic concentration of extracellular fluid Modulator - The thirst centre of the hypothalamus is stimulated making the person feel overly hydrated Effector - The kidneys begin with excretion being excreted as urine - Adrenal glands release aldosterone to maintain sodium levels within the body Response - Kidneys excrete at a faster rate and release excrete large volumes of water - Aldosterone maintains the sodium levels in the body Feedback - Decrease in bodily fluids

Stimulus - Decrease in bodily fluids Receptor - osmoreceptors in thirst centre of hypothalamus detect the increased osmotic pressure of blood Modulator - the hypothalamus stimulates the posterior lobe of the pituitary gland and the thirst centre is stimulated Effector - Posterior lobe of pituitary gland releases ADH which is carried to nephron tubules - Thirst centre makes the person feel thirsty to trigger a behavioural response Response - ADH increases the permeability to water of the distal convoluted tubules and the collect ducts - meaning more water is reabsorbed into the blood plasma - Water is consumed replenishing thirst Feedback - Increase in bodily fluids

Stimulus - Increase in CO2 concentration Receptor - Central chemoreceptors in medulla oblongata Modulator - Respiratory centre in the medulla oblongata sends nerve impulses to diaphragm and intercostal muscles Effector - Diaphragm and intercostal muscles have an increased rate and depth of breathing Response - Decrease in Co2 Feedback - Decrease in breathing rate

Physiological activites - Nervous or Endocrine mechanisms - body does it subconsciously Behavioural activities - conscious decisions to maintain homeostasis

Thermoregulation Blood glucose Gas concentrations Bodily Fluids

Disruptions to homeostasis are; Hormonal - Insulin & Thyroxine Behavioural - Drugs, Exercise, Eating Habits Disease - Emphysema, Fever, Hypertension