Skeletal muscles

Question 1

What is membrane potention?

Answer 1

is the voltage or potential inside of a membrane relative to the outside

Question 2

resting potential

Answer 2

its when the Vm is at rest

Question 3

depolarization

Answer 3

It’s a positive change in membrane potential. influx of cations in or anions out.

Question 4

hyperpolarization

Answer 4

its a negative change. Either cations out or anions in

Question 5

repolarization

Answer 5

a negative change in membrane potential. Brings the membrane back to resting potential

Question 6

Is K+ high or low inside the cell

Answer 6

High concentration of potassium inside the cell

Question 7

Concentration of Na+ and Ca2+ inside the cell relative to outside

Answer 7

low concentration

Question 8

what determines resting membrane potential?

Answer 8

1. ion concentration gradient

2. membrane permeability

Question 9

chemical force?

Answer 9

ions traveling along the concentration gradient

Question 10

what is electrical force?

Answer 10

Relation to the charge- where the cations and anions want to travel

Question 11

what is the electrochemical force

Answer 11

its the sum of the chemical and electrical force

Question 12

equilibrium potential

Answer 12

where the chemical and electrical force are equal to each other, no ions are traveling through the membrane

Question 13

what are some factors that help a cell maintain resting potential/ Vm?

Answer 13

Na+/K+ ATPase
and
K+ channels

Question 14

how does the Na+/K+ ATPase work?

Answer 14

3 Na out and 2K in.

1. Maintains concentration gradient for Na+ and K+.
2. Stabilizes resting membrane potential

produces a -1 charge inside the cell

Question 15

K+ channels- how do they work?

Answer 15

1. re-polarization after AP (a negative change in membrane potential-in this case Cation K+ is out the cell)

Question 16

when a membrane potential is NOT at equilibrium- describe the forces, net force, force strength

Answer 16

1. Net force is not at zero
2. The further away the membrane potential is from membrane equilibrium the net force increases
3. net force acts on an ion to reach membrane equilibrium

Question 17

How does net force work?

Answer 17

it works to bring the cell to membrane equilibrium

its influenced by chemical and electrical force

Question 18

The resting membrane potential for neurons is close to which cation?

Answer 18

to K+

Question 19

Ion channels are ___ or ____

Answer 19

active or passive transport

Question 20

voltage gated ion channels have

Answer 20

alpha - pore formining subunit

beta and gamma- accesory subunits

Question 21

ligand gated ion channels

Answer 21

ligand bind to the channel, acts on it

the ligand can be either intracellular or extracellular

Question 22

stretch activated channels

Answer 22

mechanic force/physical force opens the channel

ex: cochlea

Question 23

what are two types of ion channels based on permeability

Answer 23

1. specific- voltage gate

2. non-specific/promiscuous- ACh receptors allows several ions to pass through

Question 24

extracellular channel ex

Answer 24

voltage gated Na+ channels- located on the plasma membrane, exposed to the extracellular space

Question 25

intracellular channel ex

Answer 25

ryanodine receptors | located within the cell

Question 26

what is graded potential? list characteristics

Answer 26

a small change in membrane potential decremental magnitude varies depending on the stimulus can be either excitatory or inhibitory can lead to an AP at the axon hillock

Question 27

axon hillock

Answer 27

AP starts here

Question 28

Action potentials!

Answer 28

all or nothing arent decremental like graded potential travel along the PM travels in one direction

Question 29

what is absolute refractory period?

Answer 29

- channels open or close. Even if they are closed they can not be reopened by a second stimulus - depolarization and repolarization occur - NO AP CAN BE GENERATED whatsoever

Question 30

relative refractory period

Answer 30

AP can occur but the stimulus has to be very strong to create a second one - Na channels can be reopened - but it currently is hyperpolarized-requires a lot of energy - voltage-gated K+ channels open and repolarize the cell

Question 31

voltage gated channel- activation gate

Answer 31

responds to change in membrane potential

Question 32

synaptic transmission

Answer 32

neuronal AP initiates depolarization of muscle PM

Question 33

excitation-contraction coupling

Answer 33

chemical energy/AP is converted into mechanical energy | sarcomeres shorten- contraction

Question 34

what neurons (general term) control skeletal muscles

Answer 34

somatic motor neurons

Question 35

what are the voltage gated Na channels

Answer 35

1. activation gate | 2. inactivation gate

Question 36

activation gate

Answer 36

responds to change in membrane potential depolarization occurs, both activation gate and inactivation gate open

Question 37

inactivation gate

Answer 37

its a function of time - ball and socket inactivation gate closes first and then the activation gate- this allows the membrane to go back to resting membrane potential

Question 38

steps for depolarization to occur starting at axon hillock

Answer 38

Graded potential--> axon hillock -->AP down the membrane --> Ca channels open, influx of Ca causes ACh vesicles to fuse at the synaptic cleft --> ACh binds to ACh receptors at NMJ --> Na+ and K+ flow through the channel --> depolarization occurs and Na+ channels open along the sarcolema --> DHP receptor on the T-tubule open and ryanodine receptors open

Question 39

what is a TRIAD

Answer 39

sarcoplasmic reticulum plus t-tubule

Question 40

what is the conformation of myosin when ATP is absent

Answer 40

myosin head is bound to actin filament, needs ATP to be released

Question 41

conformation of myosin with ATP present

Answer 41

myosin/actin are weakly bound

Question 42

during contraction- which direction does myosin travel

Answer 42

the plus end- barbed end

Question 43

what happens during muscle relaxation

Answer 43

ACh release decreases and eventually is removed from the NMJ

Question 44

what enzyme removes ACh from the NMJ

Answer 44

acetylcholinesterase

Question 45

how does acetylcholinesterase work

Answer 45

it breaks down ACh , recycles choline back to the synaptic cleft

Question 46

What is SERCA ?

Answer 46

its a Ca2+ ATPase pump, pumps Ca2+ back into the SR.

Question 47

what does calsequstrin do?

Answer 47

binds to Ca2+ to concentrate ions