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187 Cards in this Set

  • Front
  • Back

The pathway of muscle contraction is
corticospinal pathway transmits to spinal cord, synapse in grey matter of spinal cord activates a motor neuron that causes muscle contraction
All cells are ____ charged compared to outside of the cell.
negatively
The resting potential ranges from _____ to _____ depending on the type of cell.
-5 to -100 mV
The resting potential in neurons and muscle is approximately
-60 to -90 mV
Membranes have a high _______ due to lipids in the membrane.
resistance.
The magnitude of the resting potential is due to
1. The concentration differences of ions across the cell, 2. The selective permeabilities of the ions.
The forces that affect the diffusion of ions across the membrane are
1. Electrical (ions move toward the opposite charge), 2. Chemical (concentration gradient).
Electrochemical potential is
the algebraic sum of the electrical and chemical forces for an ion.
Ohm’s law is
V=IR
In Ohm’s law, V is
potential difference (millivolts)
In Ohm’s law, I is
current or movement of ions (picoamps or nanoamps)
In Ohm’s law, R is
resistance to current (megaohms)
Conductance (g) is
the reciprocal of resistance (1/R), and the ability of an ion to move across the membrane (opening channels)
The equilibrium potential is
the membrane potential of zero when the chemical and electrical gradient oppose each other.
The membrane potential with no net movement of an ion across the membrane is
the equilibrium potential.
The equilibrium potential is negative for ________, but positive for _______.
K+ and Cl-; Na+.
The equilibrium potential for potassium is
-89 mV
The equilibrium potential for sodium is
+60 mV
The equilibrium potential for chlorine is
-72 mV
At rest, the conductance of _____ is approximately 50 times greater than ______.
K+, Na+
Due to ___________, the resting potential is close to the ________ equilibrium potential.
the selective conductance of the plasma membrane to potassium over sodium; potassium.
The leak channels that potassium and sodium pass across the membrane down their chemical gradient are
always open and are not gated or activated.
For the leak channels that potassium and sodium pass across the membrane down their chemical gradient, the number of K+ leaks channels is _____ than the Na+ leak channels.
much larger
The larger number of potassium leak channels gives K+
50 times greater conductance than Na+.
The function of the Na+/K+-ATPase is to
maintain Na+ and K+ chemical gradients by pumping out Na+ and in K+.
The membrane potential can be changed by changing
the ion concentration gradients, ion conductance, or both
Under normal physiological conditions, the ion concentration gradients
do not change.
Under normal physiological conditions, changes in __________ causes changes in the membrane potential.
the relative conductance of the ions
Changes in ion conductance are due to
opening or closing of ion channels.
Depolarizing the plasma membrane is
moving closer to 0 mV membrane potential
Hyperpolarizing the plasma membrane is
making the membrane more polarized (more negative mV) compared to resting potential.
Repolarizing the plasma membrane is
return of membrane potential to its resting level.
The driving force for an ion is
the difference between membrane (Vm) and equilibrium (Ex) potentials. It equals Vm – Ex
The larger the difference between the membrane potential and the ion equilibrium potential,
the larger the driving force and current carried by the ion.
The movement of an ion across the membrane will be dependent on
the driving force on the ion and the ion’s valence.
The ion will move in a direction that will
bring the membrane to the ion’s equilibrium potential.
Because the equilibrium potential for sodium is positive, opening Na+ channels will cause
it to flow in the cell and make the membrane potential more positive.
Because the equilibrium potential for potassium is negative, opening K+ channels cause
it to flow out of the cell and make the membrane potential more negative.
Because the equilibrium potential for chlorine is negative, opening the K+ channels with a -70 mV membrane potential will cause
it to flow in the cell and make the membrane potential more negative (-70 mv to -72 mV)
Because the equilibrium potential for chlorine is negative, opening the K+ channels with a -75 mV membrane potential will cause
it to flow out of the cell and make the membrane potential more positive (-75 mv to -72 mV)
If potassium channels close, the resting membrane potential will
become more positive, because potassium will stay in the cell.
The 3 types of ion channels are
ligand-gated, voltage-gated, mechanically-gated
The opening of a channel is called
gating
The number of ions passing through a channel determines
current
The number of ions passing through a channel depends on
the length of time it is open.
In the nervous system, the ligand-gated channels are activated by
neurotransmitters.
Voltage-gated channels are activated by
changes in membrane potential
Mechano-sensitive channels are also known as
stretch receptors
Mechano-sensitive channels are activated by
a change in the shape of a cell.
Gap junctions are
channels between two cells that allow the passage of large molecules.
Gap junctions are found in abundance in
cardiac muscle and certain smooth muscle.
Gap junctions can be regulated by
Ca2+, H+, and voltage
The pores in Gap junctions close when
Ca2+ is elevated and when pH decreases to protect adjacent cells.
In neuron anatomy, the cell body
contains nucleus and protein synthesis
In neuron anatomy, dendrites
receive input from other neurons.
In neuron anatomy, axons
transmit action potentials.
In neuron anatomy, the axon hillock
is the part of the axon next to the cell body
In neuron anatomy, the axon collaterals
are branches of the axon
In neuron anatomy, the axon terminals
are nerve terminals that release neurotransmitters
In neuron anatomy, the synapse
is the junction between nerve and nerve, muscle, or gland.
90% of cells in the central nervous system are
Glia (neuroglia)
Oligodendrocytes are found in
brain and spinal cord
The role of oligodendrocytes is
to wrap around axons to form myelin sheath and nodes of Ranvier.
Schwan cells are found in
the peripheral nervous system.
The role of Schwan cells is
to wrap around axons to form myelin sheaths and nodes of Ranvier.
Schwann cells are critical for
transmission of axon potential.
The role of astroglia is
regulate cerebrospinal fluid and form the blood brain barrier.
The role of microglia is
perform immune functions of the central nervous system.
Action potentials are
a rapid change in membrane potential.
Action potential are a property of
excitable cells (nerve, muscle, glands)
The excitability in action potentials is provided by
opening and closing of voltage-gated channels.
For a stimulus to cause an action potential, it must
reach a threshold of 55 mV
When the action potential threshold is reached
Na+ channels open allowing Na+ influx.
Influx of Na+ leads to
further depolarization of neuron (positive feedback).
At the peak of the action potential, channels
go from open to inactivated.
Na+ channels inactivate after
1 msec.
Depolarization produced by influx of Na+ causes
delayed opening of K+ channels
Efflux of K+ after an action potential causes
repolarization of neuron
Hyperpolarization after an action potential is due to
high K+ conductance.
The summary of an action potential is
1. Neuron at resting potential, 2. Depolarization reaches threshold potential and activates voltage-gated Na+ channels, 3. Influx of Na+ leads to further depolarization, 4. Delayed opening of K+ channels, 5. Na+ channels inactivate, 6. Neuron repolarized by efflux of K+, 7. Hyperpolarization due to K+ conductance, 8. K+ channels close and membrane returns to resting potential.
The properties of action potentials are
1. All-or-none response, 2. Constant amplitude, 3. Threshold, 4. Refractory period
The all-or-none response of action potentials means
once it is initiated, it goes to completion.
The absolute refractory period is
the inactivation of sodium channels immediately after firing.
The relative refractory period is
when some Na+ channels have returned to resting state, but K+ channels remain open.
The purpose of the refractory period is
to limit frequency of action potentials to approximately 100/sec and prevent action potential moving backwards.
The relative refractory period means subsequence stimuli
must be stronger to reach action potential.
The spreading currents depolarization in an action potential is propagated through
voltage-gated Na+ channels activating.
In nerve cells, action potentials propagate
from axon hillock to nerve terminal
In skeletal muscle fibers, action potentials propagate
from middle to ends.
Myelin insulates the axon to
prevent charge from leaking out of the axon.
Voltage-gated sodium channels and Na+/K+ ATPase in the axon are located only
at the Nodes of Ranvier.
Saltatory conduction is
the spread of current from node to node in an axon.
Condunction of action potential is much faster in ________ neurons.
myelinated.
The conduction velocity of an action potential is increased by
myelination and increasing the axon diameter.
In voltage-gated channels, voltage sensors
detect the voltage across the membrane
In voltage-gated channels, inactivating gates
inactivate the channel on the cytoplasmic side by blocking the opening
In voltage-gated channels, are/are not selective for a given ion.
are very selective
In voltage-gated channels, auxiliary subunits
modulate the activity of the channels.
An alpha motor neuron signals at
the neuromuscular junction.
The neuromuscular junction is located at
the End plate.
One alpha-motor neuron can innervate
several muscle fibers.
The neurotransmitter at the neuromuscular junction is
acetylcholine (Ach)
The postsynaptic receptor at the neuromuscular junction is
nicotinic cholinergic receptor.
The type of receptor of the nicotinic cholinergic receptor is
ligand-gated ion channel selective for cations (Na+ and K+)
The bouton is located
on top of the muscle fiber.
The synaptic cleft is located between
the bouton and muscle fiber itself.
Neurotransmitter release is initiated by
arrival of an action potential at nerve terminal.
The arrival of an action potential at the nerve terminal causes
depolarization of nerve terminal to activate voltage-gated calcium channels, increasing intracellular calcium.
Increased cytosolic calcium causes
release of Ach stored in vesicle into synaptic cleft.
Vesicles containing Ach bind to the plasma membrane to release their contents using
SNARE proteins.
Once released from the vesicles into the synaptic cleft, Ach
binds to and activates nicotinic cholinergic receptors (NAChR) on the endplate.
After binding to the NAChR, the Ach
dissociates from the receptor and is removed from the synapse
Ach in the synaptic cleft is metabolized by
acetylcholine esterase (AChE)
Acetylcholine esterase (AChE) is localized in
folds of the endplate.
AChE hydrolyzes Ach to
chline and acetate
Choline from the hydrolyzed Ach
is taken back into the nerve terminal to synthesize new Ach
Acetate from the hydrolyzed Ach
diffuses away from the synaptic cleft.
Acetyl Chloline (Ach) is regenerated by
1. Choline taken back into cell, 2. Choline acetyltransferase transfers acetyl group from acetyl CoA onto Choline.
Ach is taken back into the vesicle by
1. ATP dephosphorylation to ADP pumps H+ into vesicle, 2. H+ countertransported out with Ach in.
The types of synapses in the CNS are
1. Axodendritic, 2. Axosomatic, 3. Axoaxonic (presynaptic inhibition)
An axodendritic synapse fires on
a dendrite
An axosomatic synapse fires on
a cell body (soma)
An axoaxonic synapse fires on
an axon
The function of graded potentials is
generate action potentials
For graded potentials, local current spread
passively, do not propagate.
For graded potentials, amplitude
depends on the strength of stimulus (graded)
For graded potentials, decremental means
amplitude decreases as the distance form site of stimulus increase.
Graded potentials produce
electrical signals over a short distance.
Stimulus causing graded potentials leads to _______ depending on ________.
depolarizing or hyperpolarizing; the channel and ion that goes through it.
For graded potentials, temporal summation is
increasing the frequency of the action potentials of a single neuron will increase the amplitude of graded potentials.
For graded potentials, spatial summation is
multiple action potentials arrive at the same location at the same time.
The types of graded potentials are
1. Synaptic, 2. Pacemaker, 3. Generator, 4. Receptor
The types of synaptic graded potentials are
1. End-plate potentials (EPPs) in skeletal muscle, 2. Excitatory postsynaptic potentials (EPSPs) in neurons), 3. Inhibitory postsynaptic potentials (IPSPs) in neurons.
Pacemaker graded potentials are found in
heart and smooth muscle.
Generator graded potentials are found in
sensory nerve terminals
Generator graded potentials respond to
physical and chemical stimuli (heat, touch, pressure, stretching)
Receptor graded potentials are found in
special sensory tissues
Receptor graded potentials respond to
physical and chemical stimuli (sound, light, chemicals)
Excitatory postsynaptic graded potentials are produced by
excitatory neurotransmitters (excitatory amino acids glutamate and aspartate).
Excitatory postsynaptic graded potentials affect membrane potential by
moving it closer to threshold
Excitatory postsynaptic graded potentials use
ionotropic receptors
Ionotropic receptors are
ligand-gated channels (Na+-K+ channels.
Ionotropic receptors are activated by
glutamate and aspartate
Inhibitor postsynaptic graded potentials affect membrane potential by
moving it further from threshold.
Inhibitor postsynaptic graded potentials are produced by
glycine
Inhibitor postsynaptic graded potentials use
ionotropic receptors (cl-)
Action potentials are initiated at the axon hillock because
it has the lowest threshold
The greatest concentration of Na+ and K+ voltage gated channels in a neuron is at
the axon hillock.
Action potential is generated by a single/summation of excitatory postsynaptic potentials .
summation
Action potential is inhibited by a single/summation of inhibitory postsynaptic potentials
summation.
The types of muscle are
smooth and striated
The types of striated muscle are
skeletal and cardiac
Skeletal muscle is regulated by
voluntary controls
For skeletal muscle, striations are
linear
The most important skeletal muscle for survival is
diaphragm.
Cardiac muscle is regulated by
the autonomic nervous system
For skeletal muscle, striations are
branched
Smooth muscle is regulated by
autonomic, hormonal, and paracrine control
For smooth muscle, striations are
not present.
For skeletal muscle, though ________ stops at birth, fibers can still _______.
cell division; increase in size.
For skeletal muscle, fascicles are
bundles of muscle fibers.
Individual muscle cells are multi_______.
nucleated
Myofibrils are
cylindrical bundles of thick and thin filaments that form muscle fibers.
A sarcomere is
a function unit of the muscle fiber.
In a sarcomere, thick filaments are composed of
myosin
IN a sarcomere, thin filaments are composed of
actin.
Thick sarcomeric filaments contain
cross bridges
Cross bridges are composed of
heavy and light chain, ATP binding sites, actin binding sites.
Thin sarcomeric filaments contain
cross-bridge binding sites.
A bands are composed of
overlapping myosin and actin
I bands are composed of
actin alone
The molecular mechanism of contraction is
a sliding filament mechanism
The sliding filament mechanism of muscle contraction is
1. Shortening of sarcomeres due to thin filaments sliding over thick filaments, 2. I band shortens, but A band length does not change.
In shortening of sarcomeres, the thick and thin filaments do not change
length.
Swinging of cross bridges creates
muscle contraction
The 4 steps of the cross bridge cycle are
1. Energeized cross bridge binds to actin, 2. Phosphate is released and cross bridge rotates (power stroke) and pulls thin filaments towards the center of sarcomere while ADP is released form myosin head, 3. ATP binds to myosin head, cross bridge detaches, 4. Hydrolysis of ATP by ATPase on myosin energizes cross bridge.
The role of ATP in cross bridge cycle is
1. Hydrolysis of ATP energizes the cycle, 2. Binding of ATP breaks the linkage
Lack of ATP in cross bridge cycle produces
rigor mortis.
Muscle contraction initiates in response to
an increase in Ca++
The two regulator proteins of the cross bridge cycle are
tropomysin and troponin
The roles of troponin in cross bridge cycle are
1. Bind to tropomysin and holds it over myosin binding site, 2. Contains Ca++ binding sites, 3. Binding of Ca++ to troponin causes conformation change which makes tropomysin move aside and expose myosin binding sites on actin.
Action potentials in muscles trigger
release of Ca2+ from lateral sacs of the sarcoplasmic reticulum causing contraction.
______ help propagate action potential within muscle fibers
transverse tubules.
Relaxation in muscles occurs when
lateral sacs pump Ca2+ out of cytosol using Ca2+-ATPase pump.
During relaxation in muscles, the sarcomere
extends to its resting length.
Ca2+ is concentrated in the sarcoplasmic reticulum via
Ca2+ binding proteins.
The steps of Ca2+ release in muscle contraction are

1. Action potential travels along muscle fiber and activates L-type Ca2+ channels, 2. Conformation change in L-type Ca2+ channels causes activation of ryanodine receptors, 3. Activation of ryanodine receptors causes the release of Ca2+ from the sarcoplasmic reticulum.