Chapter 1A

Question 1

Homeostasis

Answer 1

The maintenance of relatively stable internal conditions. A dynamic state of equilibrium or balance, and is maintained by contributions of all organ systems.

Question 2

Variables

Answer 2

Factors that are inconsistent and changeable such as blood sugar, body temperature, blood volume, etc.

Question 3

Receptor

Answer 3

The “sensor”. Monitors environment and responds to stimuli. The receptor sends information to the control center.

Question 4

Stimuli

Answer 4

Things that cause changes in controlled variables.

Question 5

Control Center

Answer 5

Determines and keeps track of the set point at which the variable is maintained. Receives information from receptor and determines the appropriate response. Sends message to effector (negative feedback).

Question 6

Effector

Answer 6

Receives information from the control center and provides the means to respond. Response either reduces stimulus (negative feedback), or enhances stimulus (positive feedback).

Question 7

Negative Feedback

Answer 7

Most common feedback mechanism within the body. Response reduces or shuts off original stimulus. Variable changes in opposite direction of initial change.
Ex.: regulation of body temperature (a nervous system mechanism), regulation of blood glucose by pancreas (an endocrine system mechanism).

Question 8

Example of negative feedback

Answer 8

Receptors sense increased blood glucose (blood sugar). Pancreas (control center) secretes insulin into the blood. Insulin causes body cells (effectors) to absorb more glucose, which decreases blood glucose levels.

Question 9

Positive Feedback

Answer 9

Response enhances or exaggerates the original stimulus. May show a cascade or amplifying effect as feedback causes variable to continue in the same direction as initial change. Usually controls rare events that do not require constant adjustment. For example: enhancement of labor contractions by oxytocin, platelet plug formation and blood cutting when you get a cut, etc.

Question 10

Homeostatic Imbalance

Answer 10

Disruption of homeostasis leads to increased risk of disease. Contributes to changes associated with aging. Control systems become less efficient.
If negative feedback mechanisms become overwhelmed, destructive positive feedback mechanisms may take over, for example heart failure.

Question 11

Survival Needs

Answer 11

Nutrients, oxygen, water, normal body temperature, and appropriate atmospheric pressure.

Question 12

Mucosal

Answer 12

Opened to the outside world.
Ex.: mouth, nose, anus,

Question 13

Serosa (serous membrane)

Answer 13

Not open to the outside world. Consistency of snot. Covers the surfaces in ventral body cavity.