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Question 1

What is homeostasis?

Answer 1

maintain a steady state environment
temp - 37 C
PO2 - 95 mmHg
PCO2 - 40 mmHg
Water - 600 g kg
pH - 7.4

Question 2

what is an important barrier mechanism? where can you find it?

Answer 2

mucus - skin and surfaces near external environment

Question 3

how much of humans is water?

Answer 3

60%

Question 4

where is most water in our bodies found?

Answer 4

intracellular - 40% of body weight, 28L

Question 5

what percent makes up water found in interstitial fluid and lymph?

Answer 5

15% of body weight, 10.5L

Question 6

what percent makes up water found in plasma?

Answer 6

5% body weight, 3.5 L

Question 7

how much of the water found in our bodies is extracellular?

Answer 7

20% body weight, 14L = interstitial fluid + lymph + plasma

Question 8

what are transcellular fluids and what are examples?

Answer 8

CSF and joints - about 1L
-rightly regulated encapsulated spaces - water cannot freely pass
regulated by special epithelium…

Question 9

what are the constituents of plasma?

Answer 9

Na - 142
K - 4.4
Cl - 102
protein - 1 (resp. for osmotic pressure)
osmolality - 290 mOsm

Question 10

what are the constituents of interstitial fluid?

Answer 10

na - 145
K - 4.5
Cl - 4.5
protein - 0 mM
osmolality - 290 mOsm

Question 11

what are the constituents of cellular fluid?

Answer 11

na - 15
K - 120
cl - 20
protein - 4
osmolality - 290 mOsm

Question 12

why is osmolality the same across the 3 compartments?

Answer 12

water can flow freely from each compartment

Question 13

which two compartments are very similar? what do they have high and low levels of?

Answer 13

plasma + interstitial

high NaCl
low K+

Question 14

what is high and low in cellular fluid?

Answer 14

high K+

low NaCl

Question 15

what ions are found inside the cell and outside (mostly)?

Answer 15

• TONS of Na inside (10X more inside)

- TONS of K+ outside (25 X more outside)

Question 16

what is pumped in and out of the cell with the Na+K+ pumps?

Answer 16

Na+ pumped out – 3

K+ pumped in – 2

Question 17

what is the difference of homeostasis between single cell and multicellular organisms?

Answer 17

• single cell organisms biochem and physiology is controlled by the environment they live in
• multicell organisms generate their own environment in which cells live - organism maintains its own environment

Question 18

What does the milieu interieur say?

Answer 18

environment must be maintained within limits for optimum functioning
- gas tensions, glucose concentration, osmotic pressure, ion concen., pH, temp

by controlling its mileu the organism is no longer at the mercy of the environment

Question 19

what are the requirements for a feedback system?

Answer 19

sensor
integrator/comparator
effector
(controlled variable + set point)

Question 20

what is negative feedback?

Answer 20

reverse the change

Question 21

what is positive feedback?

Answer 21

make the change even worse - associated with a discrete end point

Question 22

what happens during anticipation of exercise?

Answer 22

1. symp outflow increases to maintain BP = vasoconstriction
2. hypothalamus senses heat increase and inhibits symp flow = vasodilation

*BP trumphs everything - without BP can’t supply O2 to tissue…

Question 23

what are set points?

Answer 23

vary form person to person - or over time within the individual

• deviations can either be 1. protective or 2. pathological

carcadian rhythm - since daily routine is so variable set points vary between active and passive times (day and night)

Question 24

what is feed forward control?

Answer 24

“excitement” or anticipation of change - gets the body ready!

Question 25

explain why homeostatic mechanisms can sometimes be redundant?

Answer 25

more than 1 control mech. – the more important, there are more things to back it up – if one fails, there are more to back it up.

Question 26

what is equilibrium?

Answer 26

no net energy transfer - there is balance
equal potential energy between compartments

forward rnx = reverse rnx

Question 27

what is steady state?

Answer 27

consistency over time - provide new stuff for decay
there is a rate of input and output - constant energy demands, constant metabolic expenditure

does not change over time
-most human mechanisms require a lot of energy to keep systems in steady state

ex. - cortisol