Cell Physiology; Homeostasis and Feedback Loops

Question 1

What is physiology?

Answer 1

Mechanical, physical, and biochemical functions of living organisms; The study of life, especially how cells, tissues, organs, and whole organisms function

Question 2

Two approaches to physiology

Answer 2

the purpose (why?) and mechanism (how?)

Question 3

3 main functions of physiological systems

Answer 3

1. Facilitate the survival of the individual in their environment
2. Survival of the species
3. Coordinate the functions of the individual’s anatomical/physiological systems

Question 4

What is homeostasis?

Answer 4

the ability to maintain a relatively stable internal environment in an ever-changing outside world including regulating

Question 5

Examples of processes that undergo homeostasis

Answer 5

Concentration of nutrient molecules (glucose)
Concentration of O2 and CO2
Concentration of waste products (urea, etc.)
pH
Concentration of water, salt, and other electrolytes
Volume and pressure
Temperature

Question 6

Conditions in which setpoints change?

Answer 6

Puberty
Torpor/Hibernation
Fever

Question 7

Daily Torpor

Answer 7

some small animals, like hummingbirds, lower their temp during inactive periods to conserve energy
Ex: hummingbirds

Question 8

Fever

Answer 8

rise in body temperature caused by pyrogens

Question 9

Pyrogens

Answer 9

rise in the setpoint for metabolic heat production
Exogenous: from foreign substances
Endogenous: produced by immune cells in response to infection

Question 10

Homeostatic Control Systems: How is the internal environment kept constant?

Answer 10

DETECT deviations from normal in the internal environment that need to be held within narrow limits.
INTEGRATE this information with other relevant information.
Make appropriate adjustments in order to RESTORE factor to its desired value.

Question 11

Two control systems

Answer 11

1. Negative feedback
2. Positive feedback

Question 12

Negative feedback

Answer 12

Primary type of homeostatic control.

Maintains stability by defending set points.

The main strategy is to oppose the initial change.

Question 13

Positive feedback

Answer 13

Drives physiological values away from a set point.

The initial change is amplified.

The mechanism tends to destabilize the system in order to facilitate a specific action.

Question 14

Negative Feedback Example

Answer 14

Temperature regulation

Question 15

Negative Feedback Requires:

Answer 15

1. Sensor
2. Integrator
3. Effector

Question 16

Sensor

Answer 16

Monitors magnitude of a controlled variable and relays to the integrating center

Question 17

Integrator (Control center)

Answer 17

Compares sensor’s input with a set point

Question 18

Effector

Answer 18

Receives information from the integrating center and responds accordingly

Question 19

Positive Feedback Examples

Answer 19

Ovulation: hypothalamus releases GnRH which triggers the Anterior Pituitary which release FSH & LH triggering the Ovary to release Estrogen. Estrogen signals both the hypothalamus and anterior pituitary

Question 20

Positive Feedback Example #2

Answer 20

Parturition: Uterine contractions causes the fetus to push against the cervix which cause neuroendocrine reflex stimulates oxytocin release which causes uterine contractions

Question 21

Why is understanding homeostasis important?

Answer 21

1. Redundancy
2. Hierarchy and competition
3. Adaptability
4. Pathophysiology

Question 22

Redundancy

Answer 22

the more vital the parameter is, the more systems the body mobilizes to regulate it

Question 23

Hierarchy and competition

Answer 23

feedback loops may have opposite effects

Question 24

Adaptability

Answer 24

flexibility of feedback loops allows for many forms of physiological adaptation or acclimatization

Question 25

Pathophysiology

Answer 25

Homeostasis underlies many, if not all, disease processes.
Diseases such as diabetes, hypertension, and atherosclerosis, involve both the disturbance of homeostasis, as well as the presence of inflammation