L1-Homeostasis

Question 1

Homeostasis definition

Answer 1

A defining feature of physiology involving the maintenance of nearly constant conditions in the internal environment referred to as a steady state

Question 2

Steady state definition

Answer 2

The maintenance of nearly constant conditions over time

Question 3

Examples of cell mechanisms to maintain homeostasis

Answer 3

Diffusion, endocytosis, exocytosis, protein transporters, plasma membrane

Question 4

Organ definition

Answer 4

Composed of two or more kinds of tissues (muscle, nervous, epithelia, connective) arranged in various proportions and patterns

Question 5

Organ systems definition

Answer 5

Collection of organs that perform a general function

Question 6

Organ systems of the body (11)

Answer 6

Circulatory, digestive, endocrine, immune, integumentary, lymphatic, musculoskeletal, nervous, reproductive, respiratory, urinary

Question 7

Basal metabolic rate (BMR)

Answer 7

• Energy expenditure at rest (kcal/hr/sq m body surface area)
• Largest proportion of daily energy usage (60%)

Question 8

Resting metabolic rate (RMR)

Answer 8

-Metabolic rate to sustain daily resting metabolism
-Taken under less strenuous conditions compared to BMR
-RMR>BMR
-RMR is greater in males due to increased muscle
mass and body size
-Declines with age
-Higher in people living in the arctic vs. tropical regions
-Decreased by malnutrition

Question 9

Mass balance concept

Answer 9

For a system at steady state for metabolism, any substance taken in by the body is nearly equal to the amount leaving the body plus that removed by metabolism

Question 10

Hormones that increase RMR

Answer 10

Thyroid hormone, growth hormone, testosterone, epinephrine, norepinephrine

Question 11

Net fluid balance

Answer 11

• Fluid input needs to match fluid output
• If intake exceeds output the organism is in positive balance (urine output will increase)
• If intake is less than output than the organism is in negative balance (thirst and conservation will increase)

Question 12

Primary ECF cation

Answer 12

Na+

Question 13

Primary ICF cation

Answer 13

K+

Question 14

Homeostasis of blood glucose

Answer 14

• Blood glucose levels will swing throughout the day, increasing after meals
• In diabetes, blood glucose is pathologically elevated due to dysregulation of the hormone insulin. Pancreatic B cells are the sensor of blood glucose as well as the integrator/comparator.

Question 15

Components of a negative feedback system

Answer 15

• Receptor, integrator, and effector (minimum requirements)
• Set point
• Sensors
• Major process to maintain a stable internal environment

Question 16

Feedforward/anticipatory control

Answer 16

Can regulate body systems particularly when a change with time is desirable. Anticipate change and can act in combination with negative feedback systems.

Question 17

Positive feedback

Answer 17

Accelerates a process and thus can be unstable, less common

Question 18

Negative feedback example at the molecular level (glucose)

Answer 18

When energy stores in the cell are depleted, glucose is metabolized to generate ATP. As ATP levels are restored it feeds back to inhibit the activity of specific enzymes that breakdown glucose. As ATP levels decrease again the negative feedback is removed.

Question 19

Negative feedback example at the systems level (thyroid)

Answer 19

TRH from the hypothalamus acts on the anterior pituitary gland to increase secretion of TSH. TSH acts on the thyroid to increase synthesis & secretion of TH. TH will negatively feed back on the anterior pituitary to prevent too much or too little TSH release.

Question 20

Gain of a system

Answer 20

Capacity of the system to restore a controlled variable to its set point after a perturbation. Higher gain=better ability to restore a controlled variable to its set point.

Question 21

Positive feedback negative outcome (blood loss example)

Answer 21

If a person loses 2L of blood the negative feedback mechanisms are overwhelmed and instead the initiating stimulus causes more of the same, which is positive feedback. This leads to decreased blood pressure, and decreased blood flow to the heart, and eventually death.

Question 22

Example of a useful positive feedback system

Answer 22

Blood clotting after vessel rupture, uterine contractions during childbirth, estrogen effects on the pituitary-hypothalamus before ovulation, all or none action potentials, calcium-induced calcium release in heart