homeostasis

Question 1

what is homeostasis?

Answer 1

maintenance of nearly constant conditions in the internal environment

Question 2

what is steady state?

Answer 2

the condition that homeostasis aims to achieve

Question 3

how are steady state and equilibrium different?

Answer 3

equilibrium is when solute concentrations are constant in time without requiring the input of energy

Question 4

how do organ systems collectively create a stable environment for the cells?

Answer 4

by buffering the external environment

Question 5

what constitutes an organ?

Answer 5

it is made up of two or more kinds of tissues (muscle, nervous, epithelia and connective)

Question 6

what is an organ system?

Answer 6

collection of organs that perform a general function

Question 7

what is mass balance?

Answer 7

any substance taken in by the body is nearly equal to the amount leaving the body plus what is removed by metabolism

Question 8

what is the central compartment of mass balance?

Answer 8

extracellular fluid, including blood plasma

Question 9

what is the basal metabolic rate? how much of our daily usage does it account for?

Answer 9

energy expenditure at rest. accounts for about 60% of expenditure in sedentary people

Question 10

when is metabolism lowest?

Answer 10

during sleep

Question 11

what does metabolism encompass?

Answer 11

all chemical processes involved in energy production, release and growth

Question 12

how many calories does an individual need per day to sustain resting metabolism ?

Answer 12

abour 30 kcal/kg body weight

Question 13

what is the difference between BMR and RMR?

Answer 13

RMR includes daily activity while BMR does not

Question 14

why does RMR decrease during aging?

Answer 14

reduced muscle mass

Question 15

what are some factors that increase RMR?

Answer 15

more muscle mass, increased body size, some hormones, and cold temperature

Question 16

what does malnutrition do to RMR?

Answer 16

decreases it

Question 17

what is net fluid balance and when is it positive?

Answer 17

fluid input needs to match fluid output. it is positive when intake exceeds output. (pee it out)

Question 18

what is the primary ECF cation and what is the primary ICF cation? How is this established?

Answer 18

ECF- Na
ICF- K
established by Na/K ATPases that transport 3 NA out of the cell in exchange for two K molecules into the cell

Question 19

T or F. All nutrients are controlled within extremely narrow ranges in homeostasis.

Answer 19

False. some, like plasma glucose, fluctuate over broader ranges.

Question 20

what is the pattern of plasma glucose throughout the day?

Answer 20

after meals, it spikes to varying degrees depending on the amount of carbohydrates digested. Hormones decrease the high levels without overshooting to a significant degree.

Question 21

what are the three components of negative feedback systems?

Answer 21

receptor, integrator (compares to a set point) and effector

Question 22

what does negative feedback do?

Answer 22

initiation of responses that counter deviations of a controlled variable from a normal range

Question 23

what is feed forward control?

Answer 23

regulates body systems with a desirable change like changing heart rate in anticipation of exercise
(may work with negative feedback)`

Question 24

what is positive feedback and why is it not widely used in the body?

Answer 24

it accelerates a process. uncommon because it is more likely to be unstable

Question 25

what is an example of negative feedback control at the molecular level? What is this called?

Answer 25

an active product that inhibits a step in the production of itself. Called end product inhibition

Question 26

what is an example of negative feedback control at a system level?

Answer 26

secretion of thyroxin activated by TSH hormone secreted by the pituitary. thyroxin then inhibits the pituitary from secreting TSH

Question 27

what is the “gain” of negative feedback? What is its error?

Answer 27

capacity of the system to restore a controlled variable to its set point after a perturbation. error occurs when the correction does not return the value to normal

Question 28

what does higher gain mean? what is the formula for gain?

Answer 28

when the system is better able to restore a variable to its set point
gain=correction/remaining error

Question 29

when is blood loss countered by negative feedback and when by positive feedback?

Answer 29

negative- one liter of blood is lost

positive- two liters of blood are lost

Question 30

what is the positive feedback mechanism related to blood loss?

Answer 30

decrease in blood pressure leads to a decrease in blood flow to the heart. this weakens the heart further and further diminishes blood flow

Question 31

what are some physiological examples of positive feedback?

Answer 31

blood clotting, child birth contractions, estrogen effects before ovulation, action potentials and calcium release in the heart

Question 32

T or F. The set point regulated by homeostatic mechanisms can be changed.

Answer 32

True

Question 33

what is a hierarchy of importance as it pertains to homeostasis?

Answer 33

certain homeostatic controls are more important to maintain and they will be maintained even if it throws other aspects of homeostasis further out of whack