Homeostasis

Question 1

What is Homeostasis?

Answer 1

The maintenance of the body’s internal environment within narrow limits

Includes:

Blood pH near 7.4

Body temperature near 37°C

O2/CO2 levels

Water balance / solute concentration

Blood glucose near 100mg/mL

Blood Pressure

Question 2

Homeostatic control system

Answer 2

Receptor/sensor: detects change and signals control center

Control center: relays information to appropriate effector

Effector: acts to restore normal balance

Because of the fluctuating nature of the control system, it is often called a dynamic equilibrium

Question 3

Homeostatic control system

Example: increase in carbon dioxide and decrease in
oxygen during exercise

Answer 3

Receptor: chemical receptors in brain stem are
stimulated by increased CO2, chemical receptors in
carotid arteries detect low oxygen levels

Control center: receptors go to brain, which sends
nerve signals to muscles to increase depth and rate of
breathing

Effector: increased breathing movements flush excess
carbon dioxide from body and increases oxygen
content

Question 4

Negative and Positive Feedback

The body maintains homeostasis through
2 feedback mechanisms:
——————————————–

Answer 4

Positive Feedback

• Moves variable farther away from a steady state
• In short: response increases initial stimulus
• Not useful for maintaining homeostasis

-Often associated with disease or drug
addiction

-For example: uterine contractions in birth.

Oxytocin increases contractions until
delivery

Negative Feedback

• Moves variable towards a steady state
• Change in level causes the opposite effect

(Too high, will cause a decrease in production; too
low will cause an increase in production)

In short: response reduces initial stimulus

Like a thermostat

Question 5

What is thermoregulation?

Answer 5

Regulation of heat distribution

Question 6

Thermoregulation - increase and decrease

Answer 6

Increase Body Temp

Detected by
hypothalamus →
activate cooling
mechanisms

Skin arterioles dilate,
increasing heat loss
(vasodilation)

Sweating causes
evaporative cooling

Body temperature
decreases
———————————————
Decrease Body Temp

Detected by hypothalamus
→ activate warming
mechanisms

Skin arterioles constrict
conserving heat
(vasoconstriction)

Skeletal muscle contraction
(shivering) occurs
generating heat

Hairs stand on skin

Body temperature increases