3.4 Homeostasis In Human

7/28/2019 3.4 Homeostasis In Human

http://slidepdf.com/reader/full/34-homeostasis-in-human 1/35

3.4 Homeostasis in Humans



What is homeostasis?

The maintenance of a relatively constant internalenvironment for the optimal function of cells.

Example:

The metabolism of the body affected bychanges in chemical factors (glucose and oxygenlevel) & physical factors (temperature andosmotic pressure).

The regulation of the physical and chemicalfactors in the internal environment withintolerable limits is vital for humans to survive.



Internal environment

PHYSICAL FACTORSBody temperature,Blood pressure,

Osmotic pressure

CHEMICAL FACTORSSalt & sugar level,Concentration of

enzymes

Factors Effecting InternalEnvironment



Without homeostasis, enzymatic and othermetabolic processes and reactions in the bodywill not be able to function normally.

Homeostatic regulators work on the principle of

negative feedback mechanism. – A system that maintains a factor within narrow

limits by constantly adjusting and takingcorrective action

–

Changes in the internal environment have to beremain within a normal range. (E.g. normal bodytemperature – 37oC)

Homeostasis in Humans



The excretory system plays animportant role in homeostasis.

The primary organs of theexcretory system are the kidneys.

The excretory system



The Human Kidney

Structure: Has an outer light-red region(renal cortex) and inner darker red brownregion (renal medulla)

Functions:

a. Regulate the water and salt balance in thebody by excreting more or less salt, andincreasing the intake or loss of water.

b. Regulate the osmotic pressure and ioniclevels in the blood

c. Excrete waste products

d. Regulate the blood pH



The position of kidneys in human body



The Structure of a Kidney



The Nephron

The functional unit of kidneys. Consist of 3 major parts:

1. Glomerulus

2. Bowman’s capsule

3. Renal tubule – made up of the proximalconvoluted tubule, the loop of Henle and

the distal convoluted tubule



The Structure of a Nephron



To produce urine, the nephronperform 3 basic processes:

a) Ultrafiltrationb) Reabsorption

c) Secretion

The formation of urine



a) Ultrafiltration

1. Blood containing urea and other wasteproducts enter kidney via the renalarteries.

2. Then to the Bowman’s capsule which madeup of 2 layers of cells that surround theglomerulus

3. The inner wall (podocytes) and space

between the 2 layers of cell (capsularspace).



4. Podocytes and endothelium of the glomerulusform the filtration membrane that permits thepassage of water and solutes from blood into thecapsular space

5. The fluid (which contain glucose, amino acid,urea, water, salt and small molecule) that entersthe capsular space is called glomerular filtrate.

6. Red blood cells and plasma protein remain in theblood and flows into the efferent arteriole.

a) Ultrafiltration



a) Ultrafiltration



b) Reabsorption

1. The glomerular filtrate will enter therenal tubule.

2. ..\The process of reabsorption.doc

http://localhost/var/www/apps/conversion/tmp/The%20process%20of%20reabsorption.doc






c) Secretion

1. A process in which waste and excesssubstances that were not initially filteredare secreted into the renal tubule.

2. Occurs actively at the distal convolutedtubule through passive diffusion and activetransport.

3. Secreted substances – hydrogen

ions,potassium ions, ammonia, urea, creatinine,toxin and certain drugs.



4. Purpose:- Eliminate and increase water removal from

the body

- Regulate the blood levels of certain ions.(E.g. H+ secreted more if blood pH is low)

3. Secretion

S h Of h



Schematic Diagram Of The ProcessOf Urine Formation

S h i Di Of Th P



Schematic Diagram Of The ProcessOf Urine Formation



The constituent of urine

Substance AmountWater 1 – 2 litres

Chlorine (Cl-) 6.3 g

Sodium (Na+) 4.0 g

Bicarbonate (HCO3-) 0.03 g

Urea 30 g

Potassium (K + ) 2.0 g

Uric acid 0.8 g

Creatinine 1.6 g



Test yourself

1. Explain in brief the formation of urine.2. What are the constituent of urine?



Negative Feedback Mechanism

1. Mechanism that regulates homeostasis(maintenance of a relatively constantinternal environment).

2. Helps to regulate:

– Blood glucose level

– Body temperature

– Blood osmotic pressure (salt content in theblood)

– Partial pressure of oxygen and carbondioxide



Negative Feedback Mechanism



The Role of Kidneys in Homeostasis

1. The maintenance of the water in the bodyis by keeping the blood volume and bloodosmotic pressure stable.

2. Maintaining the water content in blood atconstant level is called osmoregulation.

3. Volume of urine production and excretion

from the kidney regulates osmoregulation4. ADH – responsible for osmoregulation.



5. Osmoreceptor cells in the hypothalamusmonitor the blood osmotic pressure(increase when sweating, decrease when

haemorrhage or severe dehydration).6. ..\The regulation of blood osmotic

pressure.doc

The Role of Kidneys in Homeostasis

Haemodialysis and kidney

http://localhost/var/www/apps/conversion/tmp/The%20regulation%20of%20blood%20osmotic%20pressure.doc








Haemodialysis and kidneytransplant: life-saving therapies

1. Kidney function maybe impaired byexcessive blood loss, certain poisons orinfectious diseases.

2. Prolonged impairment, high bloodpressure and high glucose level can alsodestroy nephrons→ kidney failure.

3. Kidney failure cause accumulation of toxic

waste in the blood → death4. Haemodialysis machine and kidney

transplant can overcome the kidneyfailure.

Haemodialysis and kidney



4. Haemodialysis machine - act as an artificialkidney, operates on the principal of dialysis (separation of solute molecules

based on their different diffusion ratesacross a semi-permeable membrane).

5. Kidney transplant - placing the donor’skidney low in the abdominal cavity, withthe renal artery and vein connected to therecipient’s iliac artery and vein.

Haemodialysis and kidneytransplant: life-saving therapies



Kidney Transplant



1. The patient’s blood is drawn out, treatedwith an anticlotting agent (heparin) andpassed across one side of a cellophane

membrane.2. The other side of membrane containing

salts so that the blood does not losemineral salts by diffusion.

3. Urea and other wastes diffuse out fromthe blood and purified blood returned tothe patient.

Haemodialysis process



The process of dialysis in a haemodialysis



The Regulation of Blood Sugar Level

1. Normal range – 75 → 110 mg/100 ml 2. Regulate by islet cells in the pancreas→

produce hormone insulin (reduce blood

glucose level) and glucagon (increaseblood glucose level).

3. Defects in the production, release and

reception of insulin→

diabetes mellitus4. Over secretion of insulin → hypoglycaemia



1. Defects in the production, release andreception of glucagon→ ____________

2. Over secretion of glucagon→

___________







The Regulation of Body Temperature

1.

Changes in body temperature is detected bythermoreceptors in the skin and in thehypothalamus.

2. Thermoreceptors in the skin monitor the externaltemperature.

3. Thermoreceptors in the hypothalamus monitorthe temperature in the blood as it passesthrough the brain.

4. Thermoreceptors send impulses to the

thermoregulatory centre in the hypothalamuswhich in turn send impulses to several differenteffectors to either raise or reduce the bodytemperature.

http://localhost/var/www/apps/conversion/tmp/scratch_2/The%20regulation%20of%20internal%20body%20temperature%20by%20different%20effectors.doc



Exercise

Do Checkpoint 3.4 on page 109 in thetextbook.

Documents

3.4 Homeostasis In Human