systems physiology

physiology

the study of function and integration

fluid compartments in the body

intracellular and extracellular

intracellular fluid

within cells (ex.cytoplasm)

extracellular fluid

outside cells

types of extracellular fluids

interstitial fluid and plasma

what do interstitial fluid and plasma have in common

similar composition

how much of the cell does intracellular fluid take up

2/3

how much of the cell does extracellular fluid take up

1/3

what percentage of total body water does plasma take up

7%

what percentage of total body water does interstitial fluid take up

26%

what percentage of total body water does intracellular fluid take up

67%

dynamic constancy

fluctuation within a normal range

homeostasis

physiological variables in a state of dynamic constancy; not a static

blood sugar feedback loop

1. meal, blood sugar rises

2. pancreas receives signal about high glucose, Bcells release insulin

3. insulin tells fat, muscle cells to store sugar(out of blood, into cells)

4. decreases blood sugar

5. shuts off insulin release

labor and delivery feedback loop

1. baby head pushes on cervix-stimulates release of oxytocin from posterior pituitary

2. oxytocin binds to receptors on smooth muscle cells of uterine wall-uterus contracts

3. baby head pushes more

   • enhancement of original stimulus

what is the cell most permeable to

K+

what is the charge of inside the cell

negative

what is the resting membrane potential

-70mV

what ion does extracellular fluid have a lot of

na+

what do Na+ and K+ pumps do

pumps na+,k+ against their gradients, uses active transport(ATP),

what is pumped out of the cell with the na+/k+ pump

na+

what is pumped in the cell with the na+/k+ pump

k+

K+ and na+ leak channels

always open, ions travel with/down gradient

what is the ration btwn K+ and na+ leak channels

lots of k+ leak channels, few na+ leak channels

what is the movement of na+ and K+ in the leak channels

na+ in and k+ out

K+ and na+ voltage gated channells

ions travel down/with gradient, similar in #, open via voltage,

movement of na+ and K+ in the voltage gated channels

na+ in, and k+ out

why is the cell most permeable to K+

bc there are lots of k+ leak channels in the cell

where is na+ high: inside or outside the cell?

outside

where is K+ high: inside or outside the cell?

inside

where are the ratios of na+ and k+ like this?

bc of the na+/k+ pump

the na/k pump pumps out how many na+ for what amount of K that comes in

3 na+ out for every 2k’ in

what does the 3na’s being pumped out for every 2k going into the cell generate

net negativity in inside of the cell

what creates negative charge on membrane

K+ flows out through leak channels

driving force

willingness of ion to move

what does depolarizing mean

becoming more positive

hyperkalemia

high k+ in blood/extracellualr

what causes hyperkalemia

kidney’s not excreting potassium well

what are the effects of hyperkalemia

depolarizes the cell membrane, prevents repolarization, and prolongs ap duration

hypokalemia

decreased k+ outside of the cell

effects of hypokalemia

hyperpolarizes the cell membrane and shortens ap duration

excitability

how close rmp is to threshold

what does it mean rmp is closer to threshold

cell is more excitable

does na+ have an effect on rmp

no just k+ 

what are the phases/steps of an action potential

1: rmp, 2: threshold, 3: depolarization, 4: peak, 5: repolarization, 6: hyperpolariztion, 7: rmp

what is the average threshold point

-55 mV

what causes depolarization during action potential 

after hits threshold, current through opening voltage gated Na+ channels rapidly depolarize, causing more Na+ channels to open

what happens when a cell reaches its threshold 

Na+ channels open, allowing positively charged sodium ions into the cell 

what usually causes cell to reach its threshold 

na+ flowing into the cell

what happens when the action potential reaches its peak 

na+ channels close, voltage gated K+ channles open:k+ out of cell

what happens during repolarization of the cell

outward current through open voltage gated K+ channels: basically caused by K+ leaving the cell

what during hyperpolarization of an action potential 

persistent current through slowly closing voltage gated K+ channels, na+ channels fully closed 

what happens at the end of action potential

cell returns back to rmp because voltage gated K+ channels close 

what causes a steady resting potential at -70mv

K+ leak channels 

hyperpolarzing

becoming more negative

grade potentials

• hyperpolarzing or depolarizing

• mediated via ligand-gated channels

• height, magnitude dependent on stimulus strength

• decremental: can sum

action potential

• depolarizing

• mediated via voltage gated channels

• heigh, magnitude independent of stimulus strength

• non decremental: cannot sum

what effects the spike height of an action potential

the na+

more sodium on the outside of the cell means what for the spike of the ap

it will be higher 

more sodium on the inside of the cell means what for the spike on the ap

it will be lower

what happens to the driving force if depolarization occurs 

it goes down 

what happens to driving force if hyper polarization occurs

it goes up

what happens to driving force if sodium is greater on the outside/ decreased on the inside 

it goes up 

what happens to driving force if sodium is greater on the inside/ decreased on the outside

it goes down

hypernatremia 

increased na+ outside the cell 

effects of hypernatremia

no effect on rmp or ap duration

hyponatremia

decreased na+ outside the cell

effects of hyponatremia

no effect on rmp, and no effect on ap duration

what is a synapse

cell to cell junction between two neurons or a neuron and another cell

electrical synapse

uses gap junctions: direct physical connections btwn cells

chemical synapse

uses neurotransmitters into synaptic cleft

steps in chemical transmission 

1. ap probates down pre synaptic neuron 

2. voltage change from ap opens vg Ca2+ channels, ca2+ rushes into presynaptic terminal 

3. ca2+ helps synaptic vesicles fuse w/ pre-synaptic membrane, get release of neurotransmitters into synaptic cleft

4. neurotransmitters bind to receptors in post synaptic cell membrane.

5. response in post synaptic cleft(general) 

6. neurotransmitter removed from synaptic cleft 

is na+ inhibitory or excitatory

excitatory

excitatory neurotransmitters

make post synaptic cell more positive(depolarize) by opening na+ channels 

inhibitory neurotransmitters 

make post synaptic cell more negative(hyper polarize) by opening K+ channels 

what direction does na+ travel when excitatory neurotransmitters open na+ channels 

into the cell 

what does na+ moving into the cell when neurotransmitters open na+ channels cause

depolarization and increased likelihood of firing ap

is K+ inhibitory or excitatory 

inhibitory 

what direction does K+ flow when inhibitory neurotransmitters open up k+ channels

out of the cell, with the gradient

what are the effects of K+ flowing out of the cell when neurotransmitters open K+ channels

hyperpolarization, decreased likelihood of ap firing

ionotropic receptors

receptor and channel, ligand binds-channel opens- ions flow into pot synaptic cell

metabotropic receptors 

-receptor and binding of ligand begins 2nd messenger cascade 

SSRI’s

selective serotonin reuptake inhibitors- block reuptake protein so that more serotonin stays in the synaptic cleft which causes more post synaptic excitation 

what issue does ssri help solve 

less serotonin at some synapses 

what is the issue when anxiety is occurring

not enough inhibition at Gaba synapse

what does Cl do in anti anxiety meds

it is the ion causing the inhibitory response for neurotransmitter GABA

benzodiazepines

gaba agonists, promote more gaba transmission and get more post synaptic inhibition, anti-anxiety meds 

examples of benzodiazepines

xanax, valium 

what do local anesthetics do

they prevent the generation of ap(ap inhibition) by blocking voltage gated channels which prevents them from opening in response to na+ depolarization