Homeostasis

Question 1

Homeostasis

Answer 1

Maintenance of constant internal environment

Question 2

Process of homeostasis

Answer 2

Change is detected by a receptor
Input information send along afferent pathway to control center
Output information sent along efferent pathway to effector
Response of effector feeds back to influence, return variable to homeostasis

Question 3

What needs to be controlled

Answer 3

Conc of blood glucose
Conc of individual inorganic ions in blood (Ca2+)
Water potential of blood and body fluids
pH of blood and body fluids
Core body temp
Hydrostatic pressure of the blood

Question 4

Conc of blood glucose, uncontrolled consequences

Answer 4

Too much or too little can change water potential of cells

Brain needs constant supply of glucose for respiration

Question 5

Water potential of blood and body fluids consequences

Answer 5

Water will be drawn in or out of cells by osmosis

Question 6

pH of blood and body fluids consequences

Answer 6

Affects enzyme, bond charges, shape of active site changes

Question 7

Core body temp consequences

Answer 7

Affects enzyme function

Question 8

Hydrostatic pressure of blood consequences

Answer 8

Maintain conc gradients for diffusion in the lungs, maintain supply of oxygen and glucose for respiration, removal of waste products
Low blood pressure, insufficient oxygen to brain, fainting
High blood pressure, can damage to endothelium lining of blood vessels

Question 9

Advantages of homeostasis

Answer 9

Independence from fluctuating external conditions, activity times and ranges of climactic conditions

Question 10

Components of a control system

Answer 10

Optimum point/set level
Receptor
Coordinator
Effector
Feedback loop

Question 11

What is the optimum point/set level

Answer 11

The level, or the norm at which system operates

Question 12

What is the receptor

Answer 12

Detects any deviation from the set point and informs the coordinator

Question 13

What is the coordinator

Answer 13

Coordinates information from receptors and send instructions to effector

Question 14

What is the effector

Answer 14

Brings about corrective measures to return system to optimum point

Question 15

What is the feedback loop

Answer 15

Receptor detects stimulus created by the change to the system, effector brings about appropriate response

Question 16

Negative feedback

Answer 16

Conditions cause the level of a particular factor to fluctuate from norm
Change detected by receptors
Receptors communicate info with hormones or nervous system to effectors
Effectors correct mechanism, restores factor to normal level
Receptors detect normal levels
Corrective mechanism turned off
Fluctuations between too much and too little of the mechanism, level of factor is never constant

Question 17

Coordination center

Answer 17

In nervous communication, normal to have ventral coordination center in brain
Information from receptors relayed to coordination center
Coordination center sends messages to effectors

Question 18

Dual control

Answer 18

Usual to have dual control of one factor
Different mechanisms restore the norm from deviations in different directions
If temp rises, sweating, if temp falls, shivering

Question 19

Advantages of dual control

Answer 19

Gives more precise control

Keeps fluctuations to a minimum

Question 20

Positive feedback

Answer 20

A small change from the optimum point leads to a much greater change in the same direction
Occurs in hypo and hyperthermia

Question 21

Examples of positive feedback

Answer 21

Nerve impulses

Blood clotting

Question 22

Positive feedback in nerve impulses

Answer 22

A stimulus leads to a small influx of sodium ions, this small influx increases the permeability of the membrane to sodium ions so more sodium ions enter

Question 23

Positive feedback in blood clotting

Answer 23

Platelets release chemicals that attracts more platelets
Activated platelets will release contents of stored granules into plasma
Platelet activating factor activates more platelets