Quiz 4 (Section 2 Quiz 1)

Question 1

what are electrochemical gradients

Answer 1

-the driving force for ion movement across membranes
-due to concentration differences across a cell membrane
-due to potential differences across a membrane

Question 2

which ion(s) are most important for establishing the normal resting membrane potential of a neuron?

Answer 2

-K+ and Na+

Question 3

action potentials:

Answer 3

-conduct neural signals along the membrane
-are an all-or-none phenomenon

Question 4

which of the following statements about the absolute refractory period are true?

Answer 4

-the absolute refractory period occurs when the inactivation gates of the voltage-gated sodium channels are closed.

Question 5

electro-

Answer 5

potential difference between inside and outside of cell

Question 6

-chemical

Answer 6

concentration difference between inside and outside of cell

Question 7

concentration of potassium:

Answer 7

high inside (intracellular), low outside (extracellular)

Question 8

concentration of sodium

Answer 8

low inside (intracellular), high outside (extracellular)

Question 9

the equilibrium potential:

Answer 9

is the electrical potential that exactly opposes the net diffusion down the concentration gradient across the membrane. (Nernst/reversal potential) point where electrical and chemical forces cancel out

Question 10

nernst equation:

Answer 10

EMF (V) = (RT/zF) * (log(conc out/conc in))

Question 11

EMF in nernst equation:

Answer 11

the electromagnetic force (potential inside the membrane) in volts

Question 12

R in nernst equation:

Answer 12

universal gas constant (8.314 J/K/mol)

Question 13

T in nernst equation:

Answer 13

temperature in kelvin

Question 14

z in nernst equation:

Answer 14

electrical charge of the ion

Question 15

F in nernst equation:

Answer 15

Faraday’s constant (96,485 C/mol)

Question 16

RT/F =

Answer 16

61

Question 17

concentration of an ion is in:

Answer 17

mEq/L or mmol/L

Question 18

potassium concentrations:

Answer 18

in: 140 mEq/L
out: 4 mEq/L

Question 19

sodium concentrations:

Answer 19

in: 14 mEq/L
out: 142 mEq/L

Question 20

calcium concentrations:

Answer 20

in: 0.00007 mEq/L
out: 2 mEq/L

Question 21

chloride concentrations:

Answer 21

in: 10 mEq/L
out: 110 mEq/L

Question 22

in the nernst equation, if you end with a positive number, it indicates

Answer 22

more positive inside the cell than outside

Question 23

in the nernst equation, if you end with a negative number, it indicates

Answer 23

more negative inside the cell than outside

Question 24

when do you use the Goldman Hodgkin Equation?

Answer 24

when the membrane is permeable to several different ions (MULTIPLE IONS)

Question 25

ions most important for membrane potential:

Answer 25

Na+, K+, Cl-

Question 26

what does membrane potential depend on?

Answer 26

-polarity of the electrical charge of each ion -permeability of the membrane to each ion -concentration of the respective ions on the inside and outside of the membrane

Question 27

Goldman equation:

Answer 27

EMF (mv) = 61 * log( (PNa[Na]out + PK[K]out + Pcl[Cl]in)/(PNa[Na]in + PK[K]in + Pcl[Cl]out) ) if other concentrations are not permeable, they equal 0.

Question 28

electrochemical driving force causes net movement of the ion across the membrane. equation is:

Answer 28

Vdf = Vm - Veq,X

Question 29

Vdf is inside relative too outside:

Answer 29

-positive Vdf = positive ion moves out of the cell -negative Vdf = positive ion moves into the cell -opposite for negative ions -positive Vdf = negative ion moves into the cell -negative Vdf = negative ion moves out of the cell

Question 30

when a cell in equilibrium what happens to the ions?

Answer 30

they are still moving

Question 31

dendrites:

Answer 31

input

Question 32

axon terminals:

Answer 32

Output. where the neuron connects to another neuron.

Question 33

what is action potential?

Answer 33

rapid changes in membrane potential that spread rapidly along a nerve fiber membrane. -all or none -must pass threshold to happen -propagate along a nerve fiber until it reaches the end (if it starts, it doesnt stop) -conducts neural signals -constant amplitude. cannot become greater. one or none (ex. if two collide, its not double, only amplitude of one of them)

Question 34

action potential phases:

Answer 34

-resting: flat before and after peak -depolarization: going up -repolarization: going down the threshold/overshoot is the max peak

Question 35

voltage gated Na+ channel:

Answer 35

-2 gates (inactivation and activation) -gate is closed when at rest. a certain voltage must come along to be opened.

Question 36

voltage gated K+ channel:

Answer 36

1 gate

Question 37

large anions:

Answer 37

-too big to cross through the membrane -contribute to negative intracellular charge when K+ ions leave cell -are anions of proteins, organic phosphates and sulfates

Question 38

calcium ions:

Answer 38

-play a significant role in action potentials in cardiac cells and smooth muscle cells -calcium pumps: establish calcium concentration gradient (higher out than in) -voltage gated calcium channels: slower channels. contribute to sustained depolarization of some cells.

Question 39

what does the speed of transmission depend on?

Answer 39

fiber size and whether it is meyelinated

Question 40

Action potentials are sent from neurons to other tissues to:

Answer 40

initiate various cellular responses. muscle contraction and secretion of glands

Question 41

action potentials deliver sensory information to:

Answer 41

the central nervous system.

Question 42

excitation:

Answer 42

-the process of elictiing an AP due to any process that leads to influx of Na+ ions. -mechanical, chemical, and electrical stimuli

Question 43

initiation:

Answer 43

occurs only after the threshold potential is reached. -initial rise in potential die to one of the three stimuli. -threshold = -55 mV. triggers posiitve feedback loop

Question 44

positive feedback loop:

Answer 44

more and more voltage-gated Na+ channels open as a potential increases, until all Na+ channels are open

Question 47

is unmyelinated or myelinated neurons larger?

Answer 47

unmyelinated

Question 48

out to in:

Answer 48

epineurium perineurium endoneurium

Question 49

how often are nodes of ranvier?

Answer 49

about every 1-3 mm

Question 50

what happens in the nodes of ranvier?

Answer 50

there is no myelination so a lot of ions flow in this region.

Question 51

myelin sheath:

Answer 51

the plasma membrane of a schwann cell. wraps arond neurons in the peripheral nervous system. on eneuron per wrap. hard for ions to flow through.

Question 52

oligodendrocytes:

Answer 52

form myelin around neurons in the central nervous system- the brain and spinal cord. multiple neurons wrapped in one (opposite of myelin sheath in peripheral nervous system.

Question 53

saltatory conduction:

Answer 53

process of AP progogation in myelinated axons

Question 54

benefits of saltatory conduction:

Answer 54

-increases transmission velocity 5-50x because AP can now jump long places -conserves energy because less energy expenditure by Na+/K+ pumps because fewer ions cross the membrane

Question 55

refractory period:

Answer 55

the time in which a neuron is unable to fire another action potential

Question 56

absolute refractory period:

Answer 56

the time in which neural excitability is zero, because the sodium channels are inactivated

Question 57

relative refractory period:

Answer 57

interval following the absolute refractory period in which neural excitability is reduced and an AP can only be generated with a strong stimulus

Question 58

typical action potential:

Answer 58

depolarization immediately followed by repolarization

Question 59

action potentials with a plateau occur where?

Answer 59

cardiac muscle fibers

Question 60

plateaus in action potential:

Answer 60

-membrane does not immediately repolarize after depolarization -occurs in cardiac cell

Question 61

what are some causes of a plateau?

Answer 61

voltage gated Ca+2 channels are slower to open that voltage gated Na+ channels- prolonged depolarization phase. -voltage gated K+ channels are slower to open than usual-delayed repolarization

Question 62

repetitive discharges:

Answer 62

-rhythmic, self-induced depolarizations -occurs in the smooth muscle, regions of the heart, and some brain centers. rhythmic beating of the heart, peristalsis of the intestines, and control of breathing -caused by: high membrane permeability to Na+ leading to leakage of Na+. these leakages lead to the channels opening by themselves.

Question 63

skeletal muscle:

Answer 63

composed of muscle fascicles arranged in parallel

Question 64

muscle fiber:

Answer 64

muscle cell 10-80 micro meters in diameter

Question 65

muscle fascicles:

Answer 65

composed of muscle fibers arranged in parallel

Question 66

sarcolemma:

Answer 66

plasma membrane of a muscle fiber and collagen coating that fuses with the tendon

Question 67

sarcoplasm:

Answer 67

intracellular fluid in muscle cell. contains a lot of mitochondria

Question 68

sarcoplasmic reticulum:

Answer 68

specialized reticulum important for muscle contraction

Question 69

myofibrils:

Answer 69

-special organelle for muscle fiber contraction. arranged in parallel in muscle fiber. -contractile organelle of the muscle. 100s to 100s in parallel within each muscle cell. extend the entire length of the muscle fiber. 1-2 micro meters in diameter. composed of repeating sacromeres arranged in series

Question 70

sacromeres

Answer 70

functional unit of satiated muscle. composed mainly of actin and myosin proteins. causes muscle contraction

Question 71

myosin:

Answer 71

thick filaments. main contractile machinery

Question 72

actin:

Answer 72

thin filaments. protein that myosin walks along

Question 73

z-disk:

Answer 73

forms the lateral boundaries of the sarcomere. attaches multiple actin filaments together. attaches myofibrils together across an entire muscle fiber

Question 74

titin:

Answer 74

elastic molecule holding myosin and actin filaments in place

Question 76

I band:

Answer 76

Region around a a disc where there are only thin filaments (actin)

Question 77

M line:

Answer 77

Center of myosin tails

Question 78

H zone:

Answer 78

Region around M line where there are thick filaments only (myosin)

Question 79

A band:

Answer 79

Region that contains thick and thin filaments