D3.3 Homeostasis

mammals excrete ___ waste in the form of ___ + ___ = ___

mammals excrete nitrogenous waste in the form of urea + water = urine

why is osmoregulation needed in the body? what is it performed by?

• because the body is constantly gaining and losing water through ingestion, sweat, urination, egestion, reabsorption, etc.

• it needs to be regulated in the body so the standard level in maintained

• is performed by the kidney

in the kidney, urine exits the ___ ___ via the ___ towards the ___

finish the diagram’s boxes

in the kidney, urine exits the renal pelvis via the ureter towards the bladder

what are the 3 functions that nephrons performs? how many nephrons makes the kidney?

1. filtration - removal of metabolic waste from blood via ultrafilteration in the glomerulus

2. excretion - removal of waste

3. osmoregulation - regulate osmotic concentration in the loop of henle and collecting duct

kidney is composed of approx. 1 million nephrons

finish the diagram

outline where and under what conditons ultrafiltraton is taken place.

• filration of blood under high hydrostatic pressure in the glomerulus

  • blood enter via afferent arteiolres (short, wide —> low resistance)

  • blood exits via efferent arterioles (narrow —> high resistance)

  • difference in arteriole diameter creates high perssure within the glomerulus in order to filter as much blood as possible, so solute particles can move

• extensive capilarry bed of hte glomerulus —> inc SA —> more opportuntiies for filtration

Explain the 3 structural adaptations of the glomerulues for the purpose of ultrafiltration?

1. fenestrated capillaries: fenestratio slits in the wall (endothelium) allows blood plasma to pass through

2. basement memrane: a layer of glycoproteis that allows only small solutes and water to permeate and form the filtrate in bowman’s capsule (size selective)

3. podocytes: cells that surround/ wrap around capillaries to form filtration slits. provide structural support to avoid bursting of the capaillary under high pressure

List what remains and what leaves the blood in ultrafiltration

remains (too big)

• RBC

• WBC

• platelets

• large proteins

leaves (small) and forms filtrate in bowman’s capsule

• urea

• glucose

• AA

• ions (Na+, Cl-)

• water

• water-soluble vitamins

• toxins

• medicines

label and annotate the proces of ultrafiltration and its associated structures.

Describe selective reabsorption

• filtrate still contains useufl substances such as water , glucose, AA, ions

• needs to be reabsorbed into the bloodsream

• process occurs in the proximal convoluted tubule (PCT)

• urea, waste, toxins remain in the filtrate, and will exit as urine

4 adaptations of the PCT to capillary diffusion in selective reabsroption

1. cells of PCT contain many mitochondria to power active transport of Na+/K+ pump

2. microvilli on the cell lining to maximise diffusion surface area for reabsorption. to have more membrane proteins for transport

3. PCT wall is only one cell thick to reduce diffusion distance form filtrate blood

4. PCT cells are connected by tight junctions to prevent leakage of layer materials (e.g. urea)

Draw a diagram to show selective reabsorption

Explain the process of selective reabsorption at the PCT

• Na+ diffuse passively form PCT lumen into PCT cell via indirect active tranpsort of cotransporters. This transports glucose and AA at the same direction

• them, Na+ diffuse actively from PCT cell into blood via Na+K+ pumps.This maintains low conc of Na+ in PCT cell. ATP produced from the mitochondira in the PCt cells is used for active transport

• glucose and AA passively diffuses from PCT cell into blood

• water moves passively via osmosis, following the same direction of ions

Explain the process of osmoregualtion at the kidney.

• filtrate from PCt goes down the Loop of henle through the descending limb, then back up the ascending limb

• in the ascending limb

  • acive transport of Na+ out of the filtrate in the asecendng limb, into medulla fluid region

  • creates a hypertonic (High solute conc) medula and hypotonic (lower solute conc) ascending limb

• filtrate travels to the collecting duct for reabsorption of water

  • water exits filtrate via osmosis by aquaporins

  • from collecting duct (low solute conc) to medulla (high solute conc)

  • cocn maintained by ascending limb, so that osmosis is possible

  • water in the medulla is reabsorbed by capilarries

• concentrated filtrate (urine) collects in renal pelvis —> down ureter —> bladder —> exit

How is osmoregulation regulated by the endocrine system? outline the negative feedback loop?

• osmoreceptors in the hypothalamus detect blood solute conc levels

• hypothalamus regulates secretion of antidiuretic hormone ADH from the pituitary gland

• high blood solute conc (dehydration) —> concentrated urine (dark)

• inc secretion of ADH

• inc water absorption in the collecting duct

• low blood solute conc (quenched) —> diluted urine (light)

• dec secretion of ADH

• dec water absorption int he collecting duct

explain the mechanism of ADH

• high blood solute conc —> inc ADH

  • inc aquaporins —> inc reabsorption

    • vesicles containing aquaporins fuse into collecting duct cell membrane

    • inc osmosis rate

• low blood solute conc —> dec ADH

  • dec aquaporins —> dec reabsorption

    • collecting duct cell membrane containing aquaporins removed from cell membranes into intracellular vesicles within the cells

define homeostasis

• regulation of a constant internal env desptite change in the external env

• allows fluctuations within set acceptable limits

• scale differs: in a large cell, or an organism

list 4 homeostatic variables in humans

1. body temp

2. blood pH

3. blood glucose conc

4. blood osmotic (total solute) conc

Describe the regulation of blood glucose

• set normal value: 6-100 mg/ 100mL

• blood brings glucose to diff. lcoations, and is used in all cells for cell resp.

• brain uses ~25% of energy generated in the body

• dangerous for unregulated glucose levels

• regulated through negative feedback

• by insulin (dec glucose) and glucagon (inc glucose) hormones produced and secreted form the pancreatic endocrine cells

Explain the function of insulin

• secreted from β cells in the pancreas

• move by blood, towards target cells,

• bind at receptor moelcules, which stimulates membrane vesicles containing glucose carrier molecules to fuse to the cell membrane

• increase permeabilit of membraes to glucose —> inc glucose uptake

• dec blood glucose conc

What are the 3 target organs for insulin

1. liver: enzymes activiated fro glycogenesis

2. muscle tissue: stimualte glycogenesis

3. adipose(fat-storage cells): prevent lipolysis, so that instead of lipids breaking down into triglycerides, glucose is breaking down into triglycerides. glucose replaces lipids.

explain the function of glucagon

• secreted from a cells in the pancreas

• transported in the blood

• activates enzymes in liver cells to speed up glycogenolysis

• antagonistic to insulin

• inc production of glucose from AA and fatty acids

• inc blood glucose conc when dec of blood glucose conc is detected (neg feedback)

distinguish glycogenesis and glycogenolysis

glycogenesis (insulin cuases this to dec glucose conc in blood):

glucose —> glycogen (AA)

glycogenolysis

glycogen (AA) —> glucose

compare and contrast Insulin vs glucagon

• Insulin is produced and secreted by beta cells,while glucagon does so by alpha cells

• Insulin is secreted when there is high blood glucose cont, glucagon is secreted when there is low blood glucose cont

• Insulin lowers blood glucose level, while glucagon raises blood glucose level

• Insulin stimulates glucose movement from blood to cells, glucose stimulate glucose movement from cells to blood

• Both hormones produced by pancreas

• Both regulate blood glucose levels.

What is diabetes

a group of diseases in whcih the body fails to regulate blood glucose levels

type 1 diabetes physiological changes and risk faactors

• full name: type 1 insulin dependent diabetes/ early onset diabetes

• lack of insulin production, so high blood glucose conc in blood can’t be regulated down

• constant thrist

• undiminished hunger

• excessive urination

• can affects any age, but is typically diagnosed in early childhood or adolescence

• overall issue is unsure but possibly: genetics, autoimmune issue, beta cell issue

type 1 diabetes prevention and treatment

• no idrect cure as beta cells can’t be revived directly

• regular measurement of blood glucose test

• combo of

  • inject insulin into the bloodstream daily (usually after meals)

  • dietery modification: no large glucose intake, low carb

  • regular exercise: glucose is used more, less insulin needed

type 2 diabetes physiological changes and risk faactors

• full name: insulin independent diabetes/ late onset diabetes

• beta cells produce sufficient insulin, but insulin receptors on target cells become insulin resistnat

• as a result, beta cells inc prodcution of insulin and become exhausted

• high blood glucose can’t be regulated back down

• family history - genetics

• sedentary lifestyle, lack of exercise

• body weight: overweight or obese

• diet - high processed food, high sugar, unhealthy fats

• age: common in 45+, but now increasingly seen in jeunes

type 2 diabetes prevention and treatment

reversible with a combo of

• moderate weight loss

• regular physical activity

• healthy diet

what is thermoregulation

• control of body temp through negative feedback loop

• coordinated by the nervous system

• the hypothelamus inegrates signals from both the periphral and central thermoreceptors to regulate body temp

how do birds and mammals hav thermoregulation?

• detect changes in temp with specialised neurons called thermoreceptors

  • skin: peripheral thermoreceptors

  • in body: central thermoreceptors

what is the role of the hypothelamus in thermoregulation?

• constantly monitoring the temp of blood flowing through

• inegrates signals (input) from pericpheral and central thermorecptors to regulate bod tmep

• initiates behavioural (e.g. shiver) and physiological responses to regulate temp

what is the role of the pituitary gland in thermoregulation?

• works with hypothelamus

• to produce and release of hormones into bloodstream

Outline the negative feedback loop of thermoregulation

1. thermoreceptors detect a dec in body temp

2. hypothalamus stimulates the pituitary gland

3. pituitary gland secretes throid stimulating hormone (TSH) to stimulate the thyroid gland

4. thyroid gland secretes thyroxin hormone into bloodstream

5. thyroxin increases cells’ metabolic rate, resutling in heat production to inc body temp

• vice versa, when inc in body temp, TSH production is lowered to dec metabolic rate, less heat production

4 mechanisms in low temp

1. skeletal muscles (nervous control)

• nerves tell muscles to continually contract and relax (shiver)

• involuntary nervous control

• to generate heat

• no thyroxin invovled

2. hair erector muscles

• muscles atthe base of hair

• when contract, hair stands up → insulating effect

3. blood vessles

• peripheral blood vessels undergo vasoconstriction

• vessels in the core dilate

• blood flows close tot he core and vital organs to conserve heat

4. fat-storing bwo adipose tissue

• uncoupled respiration: mitochondria can release energy as heat without producing ATP, to inc body heat in cold env

3 mechanisms in high temp

1. blood vessels

• periphral blood vessles undergo vasodilation

• core blood vessels constrict

• blodo flows to the surface, for more heat loss

2. sweat

• secreted by glands in skin in response to high body temp

• sweat evaporates off the skin, absorbing energy in the form of heat

• dec body temp

3. hair erector muscles

• muscles underneath hair relax, cuasing hair to lay flat

• reudce insulating effect, cools the skin

• mor eheat is lost due to conduction or direct air movement