Homeostasis

Question 1

Define homeostasis

Answer 1

the ability or tendency of an organism or cell to maintain internal equilibrium by adjusting its physiological processes

(constant internal environment)

Question 2

what is “set point”

Answer 2

the ideal normal value of a variable
- values fluctuate around the set point to establish a normal range of values
- determined by CONTROL CENTRE

e.g. body temperature
rises and falls throughout the day (normal range) around 37˚C

Question 3

What is the role of organ systems in the body?

Answer 3

maintain homeostasis
- key: nervous system and endocrine system

Question 4

how does the body maintain homestasis

Answer 4

FEEDBACK SYSTEMS (3 components, 2 types)

in short…
STIMULUS (causes deviation from set point; detected by receptor)
RESPONSE (produced by effector)

Components
- RECEPTOR: monitors the value of some variable (e.g. blood pressure sensors)
- CONTROL CENTRE: establishes the set point (usually brain or spinal cord)
- EFFECTOR: can change value of variable (target organ/tissue/cell that can change value of variable)

Types
negative and positive

Question 5

describe function of negative feedback loop and examples

Answer 5

any deviation from the set point is resisted
e.g. body temp, blood pressure, blood sugar

Question 6

describe function of positive feedback loop and examples

Answer 6

When a deviation occurs, response is to make the deviation greater.
Unusual in normal, healthy individuals. leads away from homeostasis and can result in death.
e.g. after a hemorrhage, blood pressure drops and heart’s ability to pump blood decreases
e.g. GOOD positive feedback: childbirth (stretch receptors)

Question 7

Is blood pressure during exercise non-homeostatic?

Answer 7

No. Normal range changes to accommodate for larger blood flow, making the set point higher than when at rest.

Question 8

consequences of homeostasis disruption + examples

Answer 8

• disease
• death

e.g. diabetes and other hormone imbalances

Question 9

explain the positive feedback loop in childbirth

Answer 9

• uterus contracts
• stretch receptors detect contraction
• signal sent to the brain
• oxytocin released
• uterus contracts with greater force
• cycle continues until baby is born