Nerve and Muscle Physiology

Question 1

what helps to create the resting membrane potential

Answer 1

Created by passive diffusion of ions through
a selectively permeable membrane,
producing charge separation.

Question 2

in a typical cell is it more postive inside the cell or outsid e

Answer 2

negative inside and positive outside

Question 3

describe the relative concentrations of K na and cl in a cell and outside

Answer 3

more inside: k
more outside: Na
equal : cl

Question 4

what does the nernst equation tell us

Answer 4

• Nernst Equation – prediction of potential difference for a single ion

Question 5

what does the Goldman-Hodgkin-Katz Equation tell us

Answer 5

Goldman-Hodgkin-Katz Equation – used for a system involving more than one
permeable ion.

Question 6

• Threshold potential =

Answer 6

• Threshold potential – the potential at which an action potential will be
initiated by increased conductance of ions.

Question 7

• Nondecremental propagation =

Answer 7

• Nondecremental propagation – an action potential at one point on a cell
membrane.

Question 8

Relative refractory period=

Answer 8

Relative refractory period – following the absolute refractory period, when
a second potential can be evoked but requires a larger than normal
stimulation.

Question 9

When a stimulus produces depolarization that reaches threshold,
What channels open?

Answer 9

When a stimulus produces depolarization that reaches threshold,
voltage-gated Na+ channels open.

Question 10

What is responsible for for the

repolarization of the membrane?

Answer 10

Conductance is caused by opening of voltage-gated K+ channels, along
with the fall in Na+ conductance, and is responsible for the
repolarization of the membrane.

Question 11

what channels are open during hyperpolarization

Answer 11

• K+ channels remain open until the equilibrium potential is reached,
and results in temporary hyperpolarization.

Question 12

where is the action potential generated

Answer 12

• In a neuron, an action potential is generated at the axon hillock.

Question 13

what is the area behind the action potential called

Answer 13

As the action potential is conducted, the area of the membrane
directly behind the action potential is still in absolute refractory state

Question 14

what are mylin made out of and what is the function

Answer 14

Many nerve cells in vertebrates are myelinated (or covered in
multiple layers of insulating sheath of phospholipid membrane) so
that the current travels through the axon interior, but not across the
membrane.

Question 15

what forms mylin sheath in the PNS and CNS

Answer 15

The insulated sheath is formed by Schwann cells in the peripheral nervous
system.
• Insulated sheaths are formed from oligodendrocytes in the central nervous
system.

Question 16

What are the breaks in mylin called

Answer 16

To all propagation of the action potential, breaks called nodes of
Ranvier occur in the myelin sheath.

Question 17

does the action potenial run on or between the mylin

Answer 17

The propagation allows the action potential to “jump” from node to
node, bypassing the myelinated areas.
• The process by which the action potential “jumps” between nodes is
known as saltatory conduction. This allows for the rapid propagation
of the action potential.

Question 18

what are the 2 forms of synapses

Answer 18

Electrical synapse – electrical current passes directly from one cell to another.
• Chemical synapse – release of a neurotransmitter by a neuron results in the
electrical stimulation of the postsynaptic cell.

Question 19

Depolarization of the neuron reaches the axon terminal, where it
causes opening of ____channels

Answer 19

Depolarization of the neuron reaches the axon terminal, where it
causes opening of Ca2+ channels

Question 20

where do neurotransmitters get released

Answer 20

into the synaptic cleft

Question 21

At the postsynaptic membrane of a neuromuscular junction,
_____ binds to a specific subtype of acetylcholine receptor
known as the ___

Answer 21

At the postsynaptic membrane of a neuromuscular junction,
acetylcholine binds to a specific subtype of acetylcholine receptor
known as the nicotinic receptor

Question 22

The actions of acetylcholine can be blocked by ____

Answer 22

The actions of acetylcholine can be blocked by curare or by cobra
venom (a-bungarotoxin).

Question 23

• Depolarization of the motor neuron terminal results in ____ influx

Answer 23

• Depolarization of the motor neuron terminal results in Ca2+ influx.

Question 24

• Binding of _____ by ____receptors results in an end plate potential.

Answer 24

• Binding of ACh by nicotinic receptors results in an end plate potential.

Question 25

in muscle contraction , _____ is released from the sarcoplasmic reticulum, initiating
contraction.

Answer 25

Ca2+ is released from the sarcoplasmic reticulum, initiating

contraction.

Question 26

what initiates muscle contraction in msucles

Answer 26

Ca2+ is released from the sarcoplasmic reticulum, initiating

contraction.

Question 27

The thick filaments are composed of the protein ____and

anchored to the____line

Answer 27

The thick filaments are composed of the protein myosin and

anchored to the M line

Question 28

• The thin filaments are composed of ____, _____, and ______

and are anchored to the ____ line.

Answer 28

• The thin filaments are composed of actin, tropomyosin, and troponin
and are anchored to the Z line.

Question 29

Actin’s binding sites for myosin are covered by the protein

______

Answer 29

Actin’s binding sites for myosin are covered by the protein

tropomyosin.

Question 30

watch video on muscle shit

Answer 30

now

Question 31

what is blocking myosin binding sites

Answer 31

Binding of myosin to actin is blocked because myosin binding sites are
covered by tropomyosin.

Question 32

what binds to actin

Answer 32

myosin binds to actin

Question 33

what is bound to myosin head groups

Answer 33

• ADP is bound to the myosin head groups.

Question 34

• An action potential causes the release of ____ from the sarcoplasmic
reticulum and binding of Ca2+ to _____

Answer 34

• An action potential causes the release of Ca2+ from the sarcoplasmic
reticulum and binding of Ca2+ to troponin.

Question 35

• Binding of Ca2+ results in exposure of the _____ binding sites and
promotes binding of the myosin head group to actin, forming a
_____

Answer 35

• Binding of Ca2+ results in exposure of the myosin binding sites and
promotes binding of the myosin head group to actin, forming a
crossbridge.

Question 36

what two things slide past each other in muscle contraction

Answer 36

This binding results in ratcheting action of the myosin head group and
shortening of the sarcomere as actin and myosin slide past each
other.

Question 37

what causes the detaching of myosin head to detach and

“recock.

Answer 37

Binding of ATP to myosin causes the myosin head to detach and
“recock.

Question 38

what is rigor mortis

Answer 38

In rigor mortis, ATP is depleted and myosin remains bound to actin,
causing stiffness of the muscle

Question 39

is smooth muscle striated

Answer 39

its NONSTRIATED

Question 40

What is the result of action potential in smooth muscle

Answer 40

In depolarization or pharmacomechanical coupling, an increase in
Ca2+ leads to the activation of phospholipase C, which cleaves
phosphatidylinositol (IP3
), which releases Ca2+ from intracellular
stores.

Question 41

in smooth muscle , what does calcium bind to

Answer 41

calmodulin

Question 42

is cardiac muscle voluntary or involuntary

Answer 42

• Contraction of cardiac muscle is involuntary.

Question 43

Cardiac contraction is normally under the control of what

Answer 43

Cardiac contraction is normally under the control of cardiac

pacemaker cells in the sinoatrial (SA) node

Question 44

where are gap junctions found in the heart

Answer 44

• Gap junctions in cardiac muscle are found in intercalated disks.