Homeostasis in mammals title Homeostasis in mammals

17.1 What is homeostasis and why is it important? content Homeostasis in mammals 17.1 What is homeostasis and why is it important? 17.2 Regulation of the amounts of water and minerals by the kidneys 17.3 Regulation of body temperature by the skin 17.4 Regulation of blood glucose level by the liver and pancreas

17.1 What is homeostasis and why is it important? maintenance of a constant internal environment inside the body the best internal environment for cells, tissues & organs to function efficiently and effectively is provides Homeostasis examples maintained by kidneys osmoregulation & excretion skin & blood regulation of body temperature liver & pancreas regulation of blood sugar level negative feedback mechanisms

17.2 Regulation of the amounts of water and minerals by the kidneys Why important? affect normal metabolic reactions to avoid unnecessary total water movement into or out of cells Which organs are responsible for that? the kidneys important components of the urinary system Urinary system kidneys ureters urinary bladder urethra

The urinary system renal artery renal vein kidney ureters dorsal aorta inferior vena cava renal artery carries blood from aorta to kidney renal vein returns blood from kidney to inferior vena cava kidney produces urine ureters carry urine to urinary bladder

The urinary system urinary bladder two sphincter muscles urethra a muscular and elastic bag for temporary storage of urine two sphincter muscles these muscles relax when the bladder is full and urine is emptied to outside (urination) urethra passes urine from urinary bladder to outside

Examination of the urinary system of a mammal Carry out Practical 17.1 Examination of the urinary system of a mammal

dark-red & bean-shaped organs Kidneys dark-red & bean-shaped organs pelvis cortex a nephron consist of medulla cortex (outer, lighter coloured) medulla (inner, darker, with cone-like structures) pelvis (central cavity into which the cones stick out) each contains 1 - 2 million nephrons (functional units of the kidneys)

Nephron first coiled tubule glomerulus second coiled tubule a network of capillaries second coiled tubule Bowman’s capsule cup-shaped loop of Henle U-shaped loop collecting duct allows urine to flow into pelvis

Nephron efferent arteriole capillary afferent arteriole renal artery surrounding the coiled tubules and the loop of Henle leaves a Bowman’s capsule afferent arteriole a branch of renal artery renal artery renal vein

Examination of a dissected mammalian kidney or a kidney model Carry out Practical 17.2 Examination of a dissected mammalian kidney or a kidney model

How does a nephron work? Urine is formed by ultrafiltration reabsorption small molecules & water forced out from blood to Bowman’s capsule glomerular filtrate useful substances in glomerular filtrate are absorbed back into capillaries Ultrafiltration and reabsorption

How does a nephron work? Nephron is adapted to ultrafiltration efferent arteriole The glomerulus and Bowman’s capsule afferent arteriole efferent arteriole is narrower than afferent arteriole glucose amino acids water urea salts high hydrostatic pressure wall of capillaries of the glomerulus is differentially permeable only small molecules can pass through

Regions where reabsorption occurs How does a nephron work? Substance reabsorbed Regions where reabsorption occurs Mechanism Glucose (100%) Active transport & diffusion At first coiled tubule only Amino acids (100%) Mainly active transport Active transport & diffusion Salts (80%) At first coiled tubule, loop of Henle, second coiled tubule & collecting duct Water (99%) Osmosis Urea (50%) Diffusion

smaller proportion of water is reabsorbed The functions of the kidneys in homeostasis Osmoregulation (3 cases) Case A: drink too much water dilute blood more & dilute urine smaller proportion of water is reabsorbed

The functions of the kidneys in homeostasis Osmoregulation (3 cases) Case B: concentrated blood body lacks water less & concentrated urine greater proportion of water is reabsorbed

The functions of the kidneys in homeostasis Osmoregulation (3 cases) Case C: higher concentration of salt in the filtrate excess salts taken in more urine with a higher salt concentration water withdrawn from blood into the glomerular filtrate

The functions of the kidneys in homeostasis Excretion Metabolic wastes removed by high concentration is example excretion urea toxic in form of urine produced by kidneys

17.3 Regulation of body temperature by the skin 10 20 30 40 human body temperature (oC) environmental temperature (oC) Constant body temperature skin maintained by enables staying much more active at all times

Why is the regulation of body temperature important? Do you remember ? Enzymes work efficiently only within a narrow range of temperature Constant body temperature Constant activity of enzymes and rate of metabolism

Heat Gain and Heat Loss

Core temperature vs Skin temperature

Beneath the dermis is a layer of subcutaneous fat Structure and functions of the skin Diagram showing a longitudinal section through mammalian skin > 80% of total heat loss occurs through the skin the skin consists of epidermis 3 layers dermis subcutaneous fat Beneath the dermis is a layer of subcutaneous fat

Structure and functions of the skin Epidermis Diagram showing a longitudinal section through mammalian skin innermost layer produces new cells by cell division contains melanin protects the body by absorbing UV light a dark pigment

Structure and functions of the skin Epidermis Diagram showing a longitudinal section through mammalian skin middle layer consists of living cells produced from the innermost layer cells being pushed towards the surface die & flatten form outermost layer

Structure and functions of the skin Epidermis Diagram showing a longitudinal section through mammalian skin outermost layer made up of dead cells reduces water loss from evaporation protects the body from mechanical injury prevents the entry of pathogens

Structure and functions of the skin temperature receptor Dermis pain receptor Diagram showing a longitudinal section through mammalian skin sensory receptors touch receptor detect stimuli such as touch pressure pain heat and cold pressure receptor

Evaporation of sweat helps in regulating the body temperature Structure and functions of the skin sweat pore Dermis sweat gland Diagram showing a longitudinal section through mammalian skin sweat glands secrete sweat sweat duct sweat passes through sweat duct to sweat pore on skin surface (sweating) Evaporation of sweat helps in regulating the body temperature

Helps in regulating the body temperature Structure and functions of the skin O2 and nutrients Dermis blood vessel Diagram showing a longitudinal section through mammalian skin blood vessels and capillaries supply useful materials to living skin cells and remove waste products Helps in regulating the body temperature

Structure and functions of the skin Dermis hair follicle Diagram showing a longitudinal section through mammalian skin hair follicles produce new hair cells from the base of each follicle surrounded by nerve endings

Helps in regulating the body temperature Structure and functions of the skin Dermis hair erector muscle Diagram showing a longitudinal section through mammalian skin erector muscles and hair muscle contracts hair erects muscle relaxes hair lies flat Helps in regulating the body temperature

Structure and functions of the skin Dermis sebaceous gland Diagram showing a longitudinal section through mammalian skin sebaceous/oil glands secrete sebum or oil keeps the hairs and skin supple and waterproof reduces the growth of micro-organisms

Helps in heat insulation Structure and functions of the skin Beneath the dermis Diagram showing a longitudinal section through mammalian skin subcutaneous fat made up of fat-storing cells Helps in heat insulation subcutaneous fat

What happens when a mammal is The role of the skin in regulating body temperature What happens when a mammal is cold / hot? The role of the skin in regulating body temperature

Fever

Examination of a skin model and a slide of mammalian skin Carry out Practical 17.3 Examination of a skin model and a slide of mammalian skin

17.4 Regulation of blood glucose level by the liver and pancreas Why is the regulation of blood glucose level important? glucose may also be lost in urine cells lose water by osmosis affects normal metabolism too high Blood glucose level too low brain cannot function properly kept constant (90 - 100 mg/100cm3 of blood)

changes in insulin level The roles of the liver and the pancreas in regulating blood glucose level work together liver pancreas releases insulin glycogen  glucose changes in insulin level brings blood glucose level to suitable level

for a normal person, glucose is 100% reabsorbed What happens if the body fails to regulate blood glucose? glucose reabsorption in kidneys insufficient insulin excess glucose in urine for a normal person, glucose is 100% reabsorbed cannot be cured, Diabetes mellitus but can be controlled by injecting insulin regularly regulating intake of carbohydrates

blood glucose level (mg/ 100cm3) What happens if the body fails to regulate blood glucose? diabetic 1 2 3 100 150 200 time (hours) blood glucose level (mg/ 100cm3) 1 2 3 100 150 200 time (hours) blood glucose level drops very slowly with no injection of insulin injection of insulin blood glucose level drops fast after injection normal person normal level glucose solution ingested

Concept diagram Homeostasis in mammals constant internal environment is the maintenance of a is controlled by includes constant internal environment negative feed-back mechanisms osmoregulation regulation of blood glucose level excretion regulation of body temperature

constant water potential of cells and body fluid Concept diagram osmoregulation maintains a constant water potential of cells and body fluid controlled by consist of kidneys nephrons salt reabsorption maintain constant levels of work by water ultrafiltration

remove metabolic wastes Concept diagram excretion maintains a low level of controlled by metabolic wastes kidneys which remove metabolic wastes in urine

Concept diagram regulation of body temperature skin, blood maintains a skin, blood controlled by constant body temperature by the degree of the degree of the amount of vasodilation/ vasoconstriction erection of hair sweating subcutaneous fat (long-term response)

Concept diagram regulation of blood glucose level maintains a caused by constant blood glucose level liver controlled by level of insulin released by pancreas