Lecture 2.5 Control Systems & Homeostasis

Question 1

What are the elements of control?

Answer 1

• Regulated Variable: thing you want to control
• Sensor: way of measuring regulated variable
• Set Point: the value you want the regulated variable to be (can change over time)
• Comparator: way of comparing set point and regulated variable
• Effector: way of restoring regulated variable to set point

Question 2

What is an example of a homeostatic clash?

Answer 2

Marathon runner: losing water (sweat, resp, dehydration) - BV lowers, BP lowers, to increase BP, TPR increases, counteractive because then the body heats up because it would want to vasodilate to allow heat to be removed - body heats up too much because BP wins and can lead to death

Question 3

What is BP dependent on?

Answer 3

SV, HR, TPR

Question 4

What is GFR dependent on?

Answer 4

Pre and post glomerular arteriolar tone, mesangial cell contraction

Question 5

How does temp change?

Answer 5

36-37.5 is normal, 1C higher post ovulation, 0.6C higher in late afternoon

Question 6

What is the thermal energy balance?

Answer 6

Heat produced from body (90watts/hour) + heat from environment = heat lost from body

Question 7

What are the ways to lose heat?

Answer 7

Convection: heat carried away (fan blowing)
Conduction: heat transferred via touch
Radiation: heat radiating from the body when outside is cooler than internal body temp
Evaporation: sweat on the skin - liquid converted to gas

Question 8

What causes fever?

Answer 8

Pyrogenes and PGE2 - increase set temp in hypothalamus - operating at higher set temp so when body reaches 37 it thinks we are too cold (chills) then get crisis when reaching high temp point

Question 9

What inhibits PGE2?

Answer 9

Aspirin, nurofen, panadol etc