Homeostasis

Question 1

Define homeostasis.

Answer 1

Maintaining internal environment despite changes in its internal/external environment.

Question 2

Describe homeostasis imbalance.

Answer 2

-disease caused by disturbance of homeostatic mechanisms
EX: aging, genetic mutation, pathogen, environment factors
*moderate = disease
*severe = death

Question 3

Describe the homeostasis control mechanisms.

Answer 3

3 interdependent components
-sensor aka receptor
-integrating center aka control center
-effector
‘Stimulus to response model’

Question 4

Describe the stimulus to response model.

Answer 4

*signals via the NS or endocrine system or both
-afferent = from receptor to control center
-efferent = control center to effector
-effector to response/function
EX: Regulation of blood pressure:
▪ Blood vessels baroreceptors (sensors) detect if blood pressure is too high or too low and send a signal to the hypothalamus (control center)
▪ Hypothalamus sends a message (effector) to the heart, blood vessels, and kidneys, which act respond to regulate blood pressure

Question 5

Describe sensory receptors.

Answer 5

*detect signals from external environment (extrinsic factors)
-Mechanoreceptors - distention of tissue, organs or muscles (stretch receptors, baroreceptors)
-Thermoreceptors - changes in temp
-Electromagnetic receptors - electromagnetic energy (photoreceptors)
-Nociceptors - pain
-Chemoreceptors - chemical stimuli

Question 6

Describe internal environment homeostasis.

Answer 6

EX: level of chemical in blood & tissue, body temp, blood volume, BP, pH
*mechanisms to maintain internal homeostasis:
-osmosis
-passive & active transport

Question 7

Describe the 3 types of cell signaling.

Answer 7

1. Neurotransmitters = chemicals by neurons that diffuse across gap to adjacent neurons or other target organs/tissues
2. Neurohormones = chemicals by neurons into blood to distant target organ/tissue
3. Hormone = chemical secreted by cells or glands into blood for action at distant target tissue/organ

Question 8

Describe lipid VS water soluble hormones.

Answer 8

Question 9

Describe the 3 types of cell signaling.

Answer 9

1. Autocrine – chemical acts on same cell
2. Paracrine – chemical from one cell acts on adjacent cell
3. Endocrine – chemical released directly into blood

Question 10

Describe NS VS endocrine system.

Answer 10

Question 11

Describe up regulation vs down regulation.

Answer 11

1. Upregulation = absence of hormone -> increase in # of hormone receptors
   *when hormone levels are low, cells are more sensitive to it
2. Downregulation = Presence of hormone -> decrease in # of hormone receptors
   *when hormone levels are high, cells are less sensitive to it

Question 12

Describe negative feedback VS positive feedback.

Answer 12

1. Negative = reverses changes (most common)
   EX: BP & volume low, HR or CO increases as the blood vessels constrict and kidneys increase water retention – increased BP & volume - negative feedback bring cardiac output, blood vessel size, and kidney function back to normal.
2. Positive = amplifies changes unless corrected (least common)
   EX: CHF decrease CO = fluid in lungs. Low CO decreases BP, body increases blood volume but CO still low (no neg feedback loop) so CO & BP decrease (positive feedback loop) NEED INTERVENTION
   *can revert from neg to pos

Question 13

What causes homeostatic imbalance?

Answer 13

-trauma, genetic change, pathogen, environment factors, age