Homeostasis (WA1) Flashcards
Define and describe homeostasis (3)
- The maintenance of a constant internal environment.
- When an organism carries out homeostasis, it is independent from changes in external environment.
- Conditions within its body are maintained within narrow limits (set point)
What is the negative feedback system?
It is a control mechanism in which the factor being regulated is brought back to set point as soon as it is detected to have departed from it
What happen when a person enters a cold room?
The temperature receptors in the skin transmit a nerve impulse to the brain. the brain responds by sending a return nerve impulse to several target organs. Vasoconstriction of the arterioles that supply blood near the skin occurs, causing less blood to flow to the capillaries near the skin surface. This reduces heat loss from the skin surface by radiation. Less sweat is produced at the sweat glands to minimise heat loss due to evaporation of sweat. The hair erector muscles contract to raise the air, trapping heat since air is a poor conductor of heat. The body starts shivering to generate more heat. More metabolic activity, so cellular resp at higher rate, so more heat produced.
Note: Adipose tissue act as insulating layer of fat to trap heat
Why is the regulation of body temperature an example of negative feedback?
A receptor detected a stimulus which results in a self regulatory corrective mechanism that brings about the reverse effect of the stimulus.
Two advantages of Regulators
- Can stay active in cold conditions
- metabolic activity takes place at max rate all the time
Characteristics of regulators
maintain a constant internal environment, despite changes in external environment (carry out homeostasis)
- can live in wide range of climatic environments
- remain active thruout the yr, no need hibernate
Characteristics of conformers
cannot maintain constant internal temp. Allow internal conditions to fluctuate in response to external environment.
- can only live in narrow range of climatic environ
- need hibernate (behavioral adaptations)
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When body temp is high, what are the homeostatic responses
arterioles dilate and shunt vessels constrict, more blood sent to blood capillaries in dermis, more heat is loss to the environment through epidermis by conduction, convection and radiation
Sweat glands produce more sweat, more water evaporates, which increase heat loss
Decreased metabolic rate, less heat released by cellular resppiration
Hair erector muscle relax, hairs flatten
WHat are the two receptors of thermoregulation
Thermoreceptors in skin detects temp in external environment
Thermoreceptors in hypothalamus detects temp of blood
Whats excretion
its the removal of metabolic waste products and toxic substances from our body
WHats egestion
Its the removal of undigested material from the alimentary canal
Where are nitrogenous waste products excreted
Kidney (urine)
Skin (sweat)
Describe Ultrafiltration
Afferent arteriole is wider than efferent arteriole –> More blood entering glomerulus than exiting –> high hydrostatic pressure in glomerulus
Endothelial cells of glomeruluar capillaries has many small pores –> highly porous/partially permeable
High blood pressure forces water and small molecules (glucose, amino acids, urea, mineral salts) out of glomerulus into bowmans capsule. THis form glomerulus filtrate
Large molecules remain in blood
Large surface area of glomerular capillaries produce large volume of glomerular filtrate
What is reabsorbed in Proximal convoluted tubule
All glucose and amino acids
Most mineral salts
Water
What is reabsorbed at distal convoluted tubule
Water and mineral salts
What is reabsorbed at Loop of Henle
Water an dmineral salts
What is reabsorbed at collecting duct
Water and mineral salts
Whats osmoregulation
It is the control of water and solute conc in blood to maintain a constant water potential in the body
Receptors of osmoregulation
Osmoreceptors in hypothalamus detect changes in osmotic pressure/ water potential in blood
What does ADH do
ADH is secreted by pituitary gland in brain and transported in blood to kidney (impt)
Make cells in walls of collecting ducts more permeable to water
Increase amt of water reabsorbed
Whats osmostic pressure
Its the measure of tendency of a soln to take in water by osmosis
Dilute solution –> High water potential –> low osmmmotic pressure
Conc solution –> low water potential –> Higher osmotic pressure
Relationship between blood volume and blood pressure
More water reaborbed –> Blood vol increase –> BP increase
Less water reabsorbed –> Blood vol decrease –> BP decrease
How is blood cleaned in dialysis machine (6)
1) Blood is drawn from vein in patient’s arm
2) Blood is pumped thru a tubing to dialysis machine
3) tubing is bathed in a special dialysis fluid and tubing is partially permeable
4) Small molecules (eg urea) and metabolic waste products diffuse out of tubing
5) Large molecules (eg RBC, WBC platelets) remain in building
6) Filtered blood return to patient’s arm
