Biology [Module 5:Kidney&Liver&Homeostasis]

homeostasis

-the ability to maintain a relatively constant internal environment e.g temp, blood ph,water potential of blood

receptor

cell that detects a stimulus

control centre

decides the response

effector

muscle or gland that carries the response

negative feedback

reverse a change so you can restore the change back to the set point(normal value)

positive feedback

reinforce the change so the change moves further away from the set point e.g blood clotting

whcih receptors detect a change in temperature ?

thermoreceptors in the skin in the hypothalamus 

ways to lose heat

-vasolidation

-sweat glands secrete more sweat

-hair erectile muscle relax

vasolidation=too hot

-arterioles dilate so more blood flows to the skin surface at the cappilaries

-more heat is lost by radiation reversing temp(change back to set point=negative feedback)

-hair erectile muscle relax

-hairs low flat

-so less insulation

-,so more heat lost by conviction reversing temp back to set point

vasoconstriction=too cold

-vasoconstriction of arteries

-less sweating

-hair erectile muscles contract to raise hairs

-increasing insulation shivering

-to gain heat reversing temp back to the set point

Thermoregulation

-Changes in body temperature affect protein structure (including enzymes).

-Body temperature must stay within a narrow range for enzymes to function efficiently.

Ectotherms

-Rely on external sources of heat to maintain body temperature (e.g., snakes).

-Body temperature fluctuates with the environment.

-Regulated by behavioural & physiological mechanisms.

Advantages(ectotherms)

• Don’t use much energy to keep warm → more energy from food can be used for growth.

disadvantages(ectotherms)

-Less active at cooler temperatures, slower to respond → higher risk from predators.

-Inactive in winter (cannot warm up sufficiently).

responses

-Cold: bask in sun, dark colours absorb more heat, increase heat absorption from environment.

-Hot: seek shade, light colours reflect heat, decrease absorption, increase heat loss.

adaptations

• Expose body → absorb more heat (snake).

• Hide in burrow → reduce absorption (lizard).

• Orient body towards/away from sun → regulate heat absorption (lizard).

• Alter body shape → regulate surface area exposed (lizard).

endotherms

• Maintain constant internal body temperature using metabolic processes (independent of environment).

• Heat generated mainly by respiration.

• Examples: mammals, birds.

• Use behavioural & physiological mechanisms for thermoregulation.

advantages(endo)

• Enzymes maintained at optimum temperature.

• Can remain active in cooler temperatures.

• Can survive in extreme conditions (e.g., Antarctic).

disadvantage (endo)

• Require more food to fuel high metabolic rate.

• Less energy from food is available for growth.

Behavioural Responses

If too hot:

• Move to shade, wallow in water, orient body to reduce sun exposure.

• Gain less heat by conduction.

• Estivation (prolonged deep sleep).

If too cold:

• Bask in sun, press body to warm surfaces (gain heat by conduction).

• Become dormant in cold months (hibernation, e.g., black bear).

liver

-involved in homeostasis

-removes nitrogenous waste

-located beneath the diaphragm on the right hand side

-largest organ in the body 

structure

excretion

-metabolic waste removal Fromm cells e.g bile from breakdown of haemoglobin

secretion

-useful substances that are releases outside the cells e.g insulin, digestive enzymes

liver functions

-thermoregultion

-detoxificarion

-metabolim of carbohydrate, lipid and proteins

ornithine cycle

-the liver removes toxic excess nitrogenous waste from the body

alcohol damages the liver

-nad required is breaking down fats

-with excess alcohol intake, most nad would be reduced in detoxifying alcohol

-less nad would be available in break down fats so fat accumulates in hepatocytes

kidney

-involved in homeostasis ,excretion,osmoregulaion

excretion in kidney

-excretes urea and excess ion dissolve in water urine(urea is formed from excess nitrogenous waste in the live in the ornithine cycle)

osmoregulation

-maintaing body fluids and ion balance in the blood

urinary system

kidney structure

nephron structure

detoxification of alcohols

glomerulus 

-ultra filtration

-rbc and proteins remain in the blood a they are too large

high hydrostatic pressure

afferent arteriole has a wider diameter and efferent arteriole has a narrower diameter

ultra filtration

-blood enters the glomerulus through the wider afferent and leaves through the efferent arteriole which is narrower

-therefore high hydrostatic pressure than oncotic pressure for UF

-samller molecules like waterleaves through the pores of the capillary 

-basement membrane prevent RBC and protein from passing through

-gaps between podocytes allow smaller mol to pass through

PCT(proximal convoluted tubules)

-selective reabsorption

-cuboidal epithelial cells

-almost all the water is reabsorbed bak into PCT

selective reabsorption

-the uptake of nutrients+water from the glomerulus filtrate back into the blood capillary by cell transport

steps:

-active transport of Na+ ions of cuboidal epithelial cells into blood capillaries

-sets up a Na+ ion gradient

-Na+ ions would diffuse by facilitated diffusion

and co-transport glucose another nutrients into the blood capillaries 

-water is reabsorbed by osmosis into the blood capillaries 

loop of henle

-osmoregulation=water potential of blood

*countercurrent multiplier mechanism

osmoregulation steps

-ascending limb is impermeable to water

-na+ and cl- are actively transported out of the limb to tissue fluid in the medulla

-descending limbis impermeabel to water

-na+ and cl- would diffuse by facilitated diffusion into the descending limb

-this sets up a water potential gradient-the bottom has the lowest w.p

osmoreceptors

-located in the hypothalamus which detect change in w.p of blood 

posterior pituitory gland

-secres ADH into the blood

ADH

antidiuretic hormone makes the walls od the distal convoluted tubules/collecting duct more permeable to water

ADH transportation into collecting duct

-neurosecretery neurone produces ADH

-ADH is transported through the axon to the posterior pituitary gland where it is stored 

-through the posterior pituitary gland ADH is transported into the blood capillaries and transported into the collecting duct which is the target tissue

water diffusing into the blood cappilaries

-ADH binds to a complementary receptor on the epithelial cells=cells lining the DCT

-sending signals for vesicles containing aquaporins(channel proteins) to fuse with plasma membrane 

-so water diffuses from the DCT into blood cappilaries by osmosis

water potential in the blood increases

-osmoreceptors detected the increase

-send a nerve impulse to hypothalamus

-the effector posterior pituitary gland secrets less ADH into the blood capillary

-less ADH binds to complementary receptor on the walls of DCT

-less vesicles counting aquaporins fuses with the plasma mem

-the permeability of the membrane decreases, more concentrated volume of urine is produced

advantages of kidney transplant

-diet is less limited

-better quality of life

disadvantages of kidney transplant

-invasive surgery=greater risk of rejection

-need immune-repressants for their rest of their life

-side effects=high blood pressure

for kidney transplant you have to match the antigens of the donor to that of the recipient

—if not closely matched the donate kidney will be recognised as foreign antigen 

-antigens on donated kidney will be different

-triggerin an immune response ,causing rejection ,t-killers will stack he tissues leading to a rejection; antibodies would be produced by plasma B cells

-immuno represent drugs are used to suppress the immune response

causes of kidney failure

-diabetes

-heart disease

-hypertension

haemodialysis

-removes waste products from the blood

-passes blood dialyser=filtering system

-returns clean blood to the body

haemodialysis steps

-blood from the patients artery is passed through (dialysed)partially permeable mem

-heparin(auto coagulant)is added to prevent blood from clotting

-on the outside of the membrane the dialysis fluid flows in opposite direction to the blood

-the dialysis fluid has the w.p and conc of ions and glucose that the patents blood should have 

-toxins move by simple diffusion from blood into the dialysate

-air trap removes any trapped air bubble before clean blood is returned to a vet the arm.

Urine Testing

-Substances not reabsorbed by the nephron can be detected in urine (e.g. glucose → diabetes; proteins → kidney failure).

Pregnancy Testing

• Detects hCG (human chorionic gonadotrophin), a hormone secreted by pregnant women shortly after conception.

• Uses monoclonal antibodies: antibodies produced from a single clone, specific to hCG.

urine test steps

1. If pregnant, urine contains hCG.

2. Urine moves along the stick; hCG binds to mobile monoclonal antibodies with coloured beads → forms hCG–antibody complex.

3. Complex moves up test strip and binds to immobilised monoclonal antibodies, forming a visible blue line → confirms pregnancy.

4. A second set of immobilised antibodies bind to unbound mobile antibodies, forming a control line → confirms the test is working.

Testing for Anabolic Steroids

• Steroids are derived from cholesterol (lipid soluble).

• Anabolic reaction: building larger molecules from smaller ones.

• Catabolic reaction: breaking down larger molecules into smaller ones (e.g. respiration).

Effects of Anabolic Steroids(Advantages (performance enhancement)

-Increased muscle mass.

-Faster recovery from injury.

-Quicker muscle repair.

Side effects:

• Depression.

• Aggression.

• Liver damage/failure.

• Heart attack/cardiovascular disease.

Effects of Steroids on Body System

On lungs

• Stronger diaphragm → larger tidal volume.

• Improved pulmonary ventilation (breathing rate × tidal volume).

• Greater increase in lung volume during inhalation → more O₂ enters lungs.

• More O₂ delivered to skeletal muscles → more aerobic respiration → more ATP for contraction.

On heart:

• Stronger cardiac muscle.

• Improved cardiac output (cardiac output = stroke volume × heart rate).

• Left ventricle walls become stronger → greater stroke volume.

• More O₂ and glucose reach muscles.

• More aerobic respiration → more ATP available for muscle contraction.