Exam 1: APs, Escape Responses, Nervous System, Sensory Systems

Which neuron structure is more common in invertebrates than they are in vertebrates?

unipolar neurons

How do nicotinic receptors work?

When ACh binds to a nicotinic receptor, the receptor changes shape, opening a pore in the middle of the receptor that allows ions to cross the membrane.

Define: efferent neurons

convey signals from the central nervous system to effector organs

In general, there is a correlation between the complexity of the nervous system and the total number of isoforms of voltage-gated ion channels. What does this suggest?

More diverse voltage-gated channels are required to build a highly complex nervous system.

What does the third functional zone of a motor neuron consist of?

axon Action potentials occur in the axon. SIGNAL CONDUCTION

Define: lateral giant escape.

caused by LGIs when posterior end is stimulated; results in animal being propelled up and forward

What class of neurons are motor neurons?

efferent neurons

The MoGs then connect to what? What type of connection is this?

flexor muscles; chemical synapses

How many functional zones does a neuron have?

four

Mauthner Neurons have a (high/low) threshold.

high

Which of these three is the most common in the vertebrate nervous system?

multipolar neuron

What class of receptor do skeletal muscle cells express?

nicotinic ACh receptors

Define: lateral giant interneuron (LGI)

one neuron/segment, soma, and dendrites in each segment; electrical connection to anterior segment via axon

The membrane potential is expressed relative to the voltage (inside/outside) the cell.

outside

The influence of each ion on the overall membrane potential is proportional to its _____________________.

permeability

Unipolar neurons are generally what class of neurons?

sensory neurons

Define: medial giant interneuron (MGI)

soma dendrites in cerebral ganglion; axon projects through all abdominal segments

Giant axons are associated with what responses in organisms?

startle and escape

What happens to the charge difference during depolarization?

the charge difference between the inside and outside of the cell decreases, and the membrane potential becomes less negative due to either positively charged ions entering the cell or negatively charged ions moving out of the cell

True or False: Action potentials are triggered by the net graded potential at the membrane of the axon hillock.

True

True or False: MGI synapses with MoGs occur in all segments.

True

In many neurons, the threshold potential is approximately ______ mV.

-55

Most neurons have a resting membrane potential of approximately what value?

-70 mV

Describe the events of signal transmission at a chemical synapse.

1) Action potentials arrive at axon terminal. 2) Voltage-gated Ca++ channels open. 3) Ca++ enters the cell. 4) Ca++ binds to synaptotagmin on the membrane vesicles in the active zone of the synapse. 5) Synaptotagmin binds to the SNAREs. 6) Docked vesicles fuse with the membrane and release neurotransmitter by exocytosis. 7) Neurotransmitter diffuses across the synaptic cleft and binds to receptors. 8) Binding of neurotransmitter to receptor activates signal transduction pathways.

The removal of neurotransmitter from the synapse depends on three main processes. What are they?

1) Neurotransmitters can simply diffuse passively out of the synapse. 2) Surrounding cells, including presynaptic neurons, can also take up neurotransmitter. These cells act as important regulators of many neurotransmitters. 3) Enzymes present in the synapse can degrade neurotransmitter.

How do you ensure preferential activation and rapid flexion to abrupt stimuli?

1) Rapid depression of chemical synapses between mechanoreceptors and sensory interneurons with repeated stimulation. (Neurotransmitters get released less and less until there are none left.) 2) High threshold of sensory interneurons and LGIs 3) Recurrent synaptic inhibition onto afferent terminals: narrow time window for LGI activation

You have isolated two neurons, joined by a synapse, in a Petri dish. You have stimulated the first neuron at the axon hillock and successfully generated an action potential. However, there is no response by the postsynaptic neuron. Describe at least 3 possible malfunctions in synaptic transmission that would prevent the postsynaptic neuron from responding as it should.

1) Small concentration of neurotransmitter due to low frequency of AP in presynaptic cell or fast rate of degrading enzymes in synaptic cleft; result = weak response. 2) Very low density of receptors on the postsynaptic cell. 3) Postsynaptic cell needs to have the right receptor that will bind the neurotransmitter.

Two factors are required to establish a potential difference across a membrane. What are they?

1) a concentration gradient for an ion 2) a membrane that is permeable to that ion

Voltage-gated Na+ channels have two gates. What are they and how do they work?

1) activation gate: sodium channel undergoes a conformational change that opens an activation gate, allowing Na+ ions to move across the membrane, increasing the permeability of the membrane to Na+ 2) inactivation gate: time-dependent conformational change occurs in the channel, closing an inactivation gate; no more Na+ can enter the cell, terminating the depolarization phase of the action potential

As for all ligand-receptor interactions, what two factors influence the strength of signal in the target cell?

1) amount of neurotransmitter present in the synapse 2) the number of receptors on the postsynaptic cell

What are the three resistors of electrical conduction within a neuron?

1) cell membrane 2) extracellular fluid 3) cytoplasm

Three resistors of electric conduction in cells?

1) cytoplasm (intracellular fluid) 2) extracellular fluid 3) membrane / lipid bilayer

Action potentials have three phases. Describe each one.

1) depolarization phase: triggered when the membrane potential at the axon hillock reaches threshold 2) repolarization phase: follows depolarization, during which the membrane potential rapidly returns to the resting membrane potential 3) after-hyperpolarization phase: follows repolarization, in which the membrane potential becomes even more negative than the resting membrane potential and may approach the K+ equilibrium

What are the three forms of tail flip response in decapods? Hint: They are named after the neural circuitry that contributes to the expression.

1) lateral giant escape 2) medial giant escape 3) non-giant escape

Most neuron structure diversity falls within one of three major structural types. List them.

1) multipolar neurons 2) bipolar neurons 3) unipolar neurons

Animals use two main strategies for increasing the speed of action potential conduction. What are they?

1) myelination 2) increasing the diameter of the axon - giant axons

The concentration of neurotransmitter in the synapse is a result of the balance between what two rates?

1) rate of neurotransmitter release from the presynaptic cell 2) rate of removal of the neurotransmitter from the synapse

Neurons perform three distinct functions. What are they?

1) receive and integrate incoming signals 2) conduct these signals through the cell 3) transmit these signals to other cells

Neurons can be divided into one of three classes, depending on their functions. List them.

1) sensory (or afferent) neurons 2) interneurons 3) efferent neurons

What are the two main disadvantages to using large axons to increase conduction velocity?

1) take up more space; may limit the number of neurons that can be packed into the nervous system 2) have a much larger volume of cytoplasm per unit length, making them energetically expensive to produce and maintain

True or False: Neurons are the only cells that are specialized to use changes in membrane potential to communicate signals across long distances.

True

True or False: Spatial summation can also prevent action potential generation.

True

Explain why this relationship exists.

A higher density means more Na+ channels are available to open at a given stimulus intensity, and more Na+ will enter the cell. As a result, the balance point between the dissipation and influx of Na+ ions is more easily reached at a lower level of depolarization. Thus, a smaller graded potential can excite a neuron with high densities of voltage-gated Na+ channels.

How is the signaling between a neurotransmitter and its receptor terminated?

A specific enzyme in the neuromuscular synapse, called acetylcholinesterase, breaks the ACh down into choline and acetate reducing the concentration of ACh in the synapse, and causing the bound ACh to release from the receptor.

In squid, some parts of the mantle are much farther away from the central nervous system than other parts. How, then, do APs reach all parts of the mantle at the same time?

APs must be conducted faster in the neurons that innervate the distant parts of the mantle than in neurons with short axons. Axons that activate muscles at the far end of the mantle cavity have very large diameters, while axons that activate muscles in the region of the mantle cavity closest to the CNS have smaller diameters. Combining axons of varying diameters allows the near-simultaneous contraction of the entire mantle by speeding up conduction to the most distant part of the body.

Synthesis equation for acetylcholine

Acetyl CoA + choline --> ACh + CoA

How can an action potential carry information about the signal strength?

Because action potential frequency is related to the strength of the stimulus.

Explain the importance of animal behavioral hierarchies and how they are determined at the level of nervous networks. Use an example to explain.

Behavioral hierarchies that are higher in the spectrum also correlate to higher levels of predictability in terms of the type of physiological mechanism that will be utilized to execute the behavior. This may be due to how some mechanisms shut off others in order to be completed. An example would be the amphibian fast escape. Defense is of high behavioral hierarchy, and thus it is possible for us to predict what sort of physiological mechanism will be utilized while also shutting off lower hierarchal behaviors. To execute defense (high level), the amphibian will utilize Mauthner Neurons. Only when this defense mechanism has been completed will the organism resume normal postural swimming (low level).

Although signal transmission across an electrical synapse is much more rapid than across a chemical synapse, chemical synapses have one substantial advantage over electrical synapses. What is it?

Chemical synapses provide an additional level of regulation for the nervous system; in comparison, direct electrical coupling across an electrical synapse limits the diversity of the signal in the postsynaptic cell.

Why do action potentials occur only in the downstream direction rather than spreading backward toward the axon hillock?

During the absolute refractory period, Na+ are unable to open in response to change in the membrane potential, thus are incapable of generating additional action potentials. This prevents backward (retrograde) conduction of action potentials. In addition, during the relative refractory period, a larger depolarization is required to reach threshold in order to fire another action potential (due to the membrane being more hyperpolarized). Only a very strong stimulus can cause an action potential during the relative refractory period. Together, the absolute and relative refractory periods prevent retrograde conduction of action potentials.

True or False: Neurons are the only excitatory cells.

False

True or False: The changes in membrane potential during the action potential are associated with measurable changes in ion concentrations inside or outside the cell.

False; NOT associated. The number of ions moving across the membrane is extremely small compared with the total number of ions in the intracellular and extracellular fluids.

True or False: The bulk of the fluid in the cytoplasm and extracellular fluids is electrically charged.

False; it is NOT charged

True or False: Increasing the radius of an axon has a much greater effect on the membrane resistance than the intracellular resistance.

False; much greater effect on the intracellular resistance.

True or False: LGI synapses with MoGs occur in all segments.

False; only anterior segments 1-3

True or False: The amount of neurotransmitter released at a synapse is NOT related to the frequency of action potentials at the axon terminal.

False; related.

True or False: Changes in the time constant of the membrane have a relatively large effect on local current flow as axon diameter increases.

False; relatively small effect

What does this mean for the M Neuron?

For the M Neuron to fire, there must be multiple EPSPs that sum from sensory input

What type of channel is responsible for the loss of positive charge in electrotonic conduction?

K+ leak channels

List all the differences between graded potentials and action potentials.

GRADED POTENTIALS 1) vary in magnitude 2) vary in duration 3) decay with distance 4) occur in dendrites and cell body 5) caused by opening and closing of many kinds of ion channels ACTION POTENTIALS 1) always the same size and shape (in a given cell type) 2) always the same duration (in a given cell type) 3) do not decay with distance 4) occur in axons of neurons (also in muscle cells) 5) caused by opening and closing of voltage-gated ion channels

How is the time constant important for temporal summation?

If the time constant is small, these potentials will decay rapidly, and they are less likely to be able to sum to provide a supra threshold potential. If the time constant is large, these potentials will decay slowly, making them more likely to overlap in time, and thus to sum to a supra threshold potential.

Explain how the cell membrane acts as a capacitor.

In a cell, the cytoplasm and the extracellular fluids are conducting materials, whereas the lipid bilayer of the cell membrane is the insulator.

Electrical synapse versus chemical synapse?

In an electrical synapse, the electrical signal is directly transmitted from the presynaptic cell to the postsynaptic cell via GAP JUNCTIONS. In a chemical synapse, the electrical signal in the presynaptic cell is converted to a chemical signal, in the form of a neurotransmitter, which crosses the synaptic cleft and binds to a receptor on the postsynaptic cell membrane. The receptor converts the chemical signal to an electrical signal in the postsynaptic cell.

Which of these channels will cause hyperpolarization when opened?

K or Cl

True or False: The structure of a neuron relates to the function of that particular neuron.

True

What are the three primary ions that affect the membrane potential for most cells? Why?

K, Na, Cl because they can move across membranes and there are differences in their intracellular and extracellular concentrations

What are the LGIs and MGIs connected to? What type of connection is this?

Motor Giant neurons (MoGs); electrical synapses

When you increase axon diameter, you decrease membrane resistance, therefore decreasing the length constant and slowing conduction speed. However, intracellular resistance decreases, increasing conduction speed (by increasing length constant). Why don't these two effects cancel each other out?

NET EFFECT Ri decreases in proportion to the radius of the axon squared, while Rm decreases in direct proportion to the radius of the axon. Thus, increasing the radius of an axon has a much greater effect on the Ri than on the Rm. Therefore, the net effect of increasing the radius of an axon is to increase the speed of conduction.

Which of these channels will cause depolarization when opened?

Na or Ca

What are the most important ion channels in the dendrites and cell body of a neuron?

Na, K, Cl, and Ca

What is the relationship between the density of voltage-gated Na+ channels to the threshold in neurons?

Neurons that have a higher density of voltage-gated Na+ channels will have a LOWER threshold than neurons with a lower density of voltage-gated Na+ channels.

What is the relationship between the density of voltage-gated Na+ channels to the relative refractory period in neurons?

Neurons with higher densities of voltage-gated Na+ tend to have SHORTER relative refractory periods because of the decrease in the threshold potential.

Why is the action potential termed the "all-or-none" response?

Once an action potential has been initiated, it always proceeds to its conclusion; it never stops halfway through or fails to reach its peak depolarization.

Why would there be a direct electrical input to the LGI?

Organism is ready to respond or is aware that there is something going on. Preparedness.

What happens to membrane resistance and intracellular resistance as axon diameter increases?

Rm = decreases ---> greater flow of ions from leak channels (Membrane resistance is inversely proportional to the surface area of the membrane. As surface area increases, so does the number of leak channels, allowing greater ion flow across the membrane so that membrane resistance decreases.) Ri = decreases ---> more volume, less resistance (Intracellular resistance is related to the volume of the axon. As volume increases, intracellular resistance decreases.) BOTH MEMBRANE RESISTANCE AND INTRACELLULAR RESISTANCE DECREASE.

What types of cells form the myelin sheath?

Schwann cells, which are specialized lipid-rich cells

Describe the escape response in amphibians in one sentence.

The fast start escape response is caused by a unilateral C-flexion, approximately 8 ms after stimulation, 90 degrees away from the side stimulated.

Explain why.

The effect of membrane resistance and membrane capacitance on the time constant of the membrane have a tendency to cancel each other out.

Why is that saltatory conduction along a myelinated axon is much faster than conduction along an unmyelinated axon of equivalent size?

The myelin increases distance over which electrotonic current can spread by acting as an insulator that prevents charge from leaking out across the membrane.

The placement of the nodes of Ranvier is critical for the function of a myelinated axon. Explain why.

The nodes cannot be placed too far apart or the signal will not be sufficient to depolarize the neuron beyond threshold at the next node, because current inevitably decreases with distance, although less so in a myelinated axon than in an unmyelinated axon.

What is temporal summation?

The phenomenon in which depolarizations that occur at slightly different times combine to determine the net change in membrane potential at the axon hillock.

What is spatial summation?

The phenomenon in which graded potentials from different sites interact with each other to influence the net change in membrane potential at the axon hillock.

How does changing the time constant of the membrane affect the speed of conduction along the axon?

The smaller the time constant of the membrane, the faster the membrane can depolarize by a given amount and the greater the rate of electrotonic current spread and AP propagation.

The exact shape of the action potential can vary among neurons from different organisms, between types of neurons from the same organism, and even among action potentials within the same neuron under different physiological conditions. Why is this so?

The variations in the shapes of action potentials are the result of the diversity of the molecular properties of the voltage-gated Na+ and K+ channels among these neurons.

Why are some voltage-gated K+ channels referred to as delayed rectifiers?

They respond relatively slowly to changes in membrane potential, increasing the length of the action potential.

How is action potential frequency coupled to the extent of neurotransmitter release?

When action potentials arrive at the axon terminal at high frequency, the processes removing Ca++ from the cell cannot keep up with the influx of Ca++ through the activated channels, and the intracellular Ca++ concentration increases. This increased intracellular Ca++ provides a stronger stimulus for exocytosis. Thus, the signal intensity that was coded by action potential frequency is translated into differences in the amount of neurotransmitter released by the neuron.

What is the relationship between membrane resistance and current flow?

When membrane resistance is high, current flow across the membrane will be low, and less charge will be lost. When membrane resistance is low, current flow across the membrane is large, and more charge will be lost, resulting in greater dissipation of the axonal current with distance.

Explain the process of how the Mauthner Neurons regulate the C-flexion behavior when stimulated. Include the types of neurons involved.

When the organism is stimulated on one side, a single action potential in the M neuron propagates down the axon that crosses onto the contralateral side. This process begins when stimulation excites the M neuron somas and causes an action potential to fire. This excitation causes depolarization of a crossed inhibitory interneuron that hyper polarizes the M neuron axon on the opposite side of the stimulus to prevent it from firing an AP on the wrong side. Input to the Commissural Neuron inhibits both M neuron somas, one on the wrong side of the stimulus and the other on the same side of the stimulus (to allow only one AP on stimulated side). The M neurons excite segmental motor neurons the side ipsilateral to the M neuron axon (or contralateral to the soma). Other motor neurons are excited with a delay via relay neurons (descending interneuron). Results in contraction and C-flexion on the opposite side to the stimulus.

Why, then, would giant axons be used if they can be disadvantageous? Hint: when would they be useful?

You would expect that giant axons would be used only when extremely high-speed conduction is necessary for survival.

Define: excitatory potential

a depolarizing graded potential that makes an action potential more likely to occur by bringing the membrane potential closer to the threshold potential

What is convergence in an escape pathway usually associated with?

a high threshold of the response

Define: inhibitory potential

a hyperpolarizing graded potential that makes an action potential less likely to occur (by taking the membrane potential farther from the threshold potential)

Which neurons are responsible for the mediation of this fast start response?

a single pair of Mauthner Neurons

The property of excitability gives neurons certain abilities. What are they?

ability to store, recall, and distribute information

What is the name of the neurotransmitter that is released into the synapse by vertebrate motor neurons?

acetylcholine (ACh)

What is the most important determinant of ACh concentration in the neuromuscular junction?

acetylcholinesterase activity plays an important role in regulating the strength of the signal to the postsynaptic cell by regulating the concentration of neurotransmitter at the synapse

What characteristic of a graded potential reflects the strength of an incoming stimulus?

amplitude

What does the second functional zone of a motor neuron consist of?

axon hillock Incoming signals from dendrites and the soma are conducted to the axon hillock. If the signal at the axon hillock is large, an action potential is initiated. SIGNAL INTEGRATION

What does the fourth functional zone consist of?

axon terminals Each axon terminal is a swelling of the end of the axon that forms a synapse with the target skeletal muscle cell. At the axon terminal of a motor neuron, the electrical signal is transduced into a chemical signal in the form of a chemical neurotransmitter. The neurotransmitter diffuses across the synapse and binds to specific receptors on the muscle cell membrane, initiating a signal in the muscle cell and causing the muscle to contract. SIGNAL TRANSMISSION

Which of the following statements is true about voltage-gated K+ channels? Select one: a) Many triggered to begin to open at voltages below the resting membrane potential. b) Some triggered to begin to open at voltages near the threshold potential c) They are triggered to open at voltages near the Na+ equilibrium potential. d) They are all triggered to begin to open at voltages near the resting membrane potential.

b) Some triggered to begin to open at voltages near the threshold potential

The genome of the nematode worm Caenorhabditis elegans completely lacks voltage-gated Na+ channels. What kind of potential does it use, then, to transmit information along the short distances required in the neurons of these small animals?

graded potentials

Action potentials are able to travel over long distances without decaying because Select one: a) the action potential uses completely different ions than graded potentials. b) one action potential generates the next one in an adjacent area of membrane. c) the axons are perfectly insulated, so no current is able to leak out. d) once the electrical signal has passed threshold, it is impossible for the signal to decay.

b) one action potential generates the next one in an adjacent area of membrane

Why do action potentials generally occur in the axon?

because voltage-gated Na+ channels are usually present at high concentrations only in the axon

Which of these three is the least common in the vertebrate nervous system?

bipolar neuron

Define: medial giant escape.

caused by MGI when anterior is stimulated (tactile or visual stimulus; results in animal being propelled backward

Define a graded potential.

changes in the membrane potential of a cell that vary in magnitude with the stimulus intensity; results from the opening and closing of ion channels

Vertebrate motor neurons receive incoming signals in the form of a ____________ neurotransmitter.

chemical

Define: relative refractory period

coincides with the after-hyperpolarization phase; a new action potential can be generated, but only by a very large stimuli

Define: absolute refractory period

coincides with the depolarization and repolarization phases; the axon potential is incapable of generating a new action potential, no matter how strong the stimulus

What do LGIs act as? What does this mean?

command neurons; LGIs make final decision to fire AP or not (integration)

Graded potentials can travel through the cell, but they decrease in strength as they get farther away from the opened ion channel. What is this phenomenon called?

conduction with decrement

Define: sensory neurons

convey sensory information from the body to the central nervous system (which consists of the brain and spinal cord in vertebrates)

Define: interneurons

convey signals from one neuron to another (located within the central nervous system)

What does the first functional zone of a motor neuron consist of?

dendrites and cell body (or soma) Dendrites are responsible for sensing incoming signals, converting these signals into an electrical signal in the form of a change in membrane potential, and transmitting the signal to the soma. SIGNAL RECEPTION

Define: SNARE proteins

docking proteins that bind readily release pools of vesicles at the active zone of the synapse

What are some of the factors that can regulate the density of receptors on the postsynaptic cell?

genetic variation among individuals, the metabolic state of the postsynaptic cell, and specific drugs and disease states

Define: unipolar neuron

has a single process from the cell body In most unipolar neurons, this process splits into two main branches (pseudo-unipolar). One of these branches conveys signals toward the cell body, and the other conveys signals away from the cell body.

Define: multipolar neuron

have many cellular extensions (or processes) that originate at the cell body. Only one of these processes is an axon, whereas the remaining processes are dendrites.

Define: bipolar neuron

have two main processes extending from the cell body, one of which is highly branched and conveys signals to the cell body, and thus is functionally similar to a dendrite, and the other of which conveys signals away from the cell body, and thus acts as an axon

Is the density of voltage-gated channels at the nodes of Ranvier high or low? What is the result of this?

high density; decreases the threshold potential for firing of action potentials, decreasing the size of the electrotonic current needed to trigger an action potential

Nodes of Ranvier contain (high/low), while internodes contain (high/low), densities of voltage-gated channels.

high; low

What is the crossed inhibitory interneuron responsible for?

hyperpolarizes the M neuron axon on the opposite side of the stimulus to prevent it from firing

In what area does the membrane potential occur? Why is this?

in the area immediately adjacent to the membrane; Electrical interactions can only occur across very small distances, and do not affect ions in the bulk phase of the cytoplasm or extracellular fluid.

Reducing ion leakage (increases/decreases) the length constant of the membrane, (increasing/decreasing) the distance that local current can travel electrotonically before degrading.

increase, increasing

Reducing ion leakage (decreases/increases) overall conduction velocity.

increases

What is the function of a myelin sheath?

increases the speed of conduction of electrical impulses to the axon terminals

The length constant (decreases/increases) as membrane resistance increases, but (decreases/increases) as intracellular resistance increases.

increases; decreases

What is the Commissural PHP Neuron responsible for?

inhabitation of both M neuron somas first = inhibits M neuron soma on opposite side of stimulus second = inhibits M neuron soma on same side of stimulus to allow only one AP to fire

Define: myelin

insulating layer that wraps around the axons of vertebrate motor neurons

What does divergence in an escape pathway indicate?

large amplitude of response

When Na+ enters the cell, what causes the depolarization to move along the membrane in all directions?

positive charges from Na attract nearby negatively charged particles and repel positively charged ones, causing the positive charges to spread away from the site of the initial depolarization along the membrane

What type of feedback system drives the depolarization phase of an action potential?

positive feedback loop HODGKIN CYCLE

A decrease in neurotransmitter release with repeated action potentials is termed...?

synaptic depression

Define: presynaptic cell, postsynaptic cell, synaptic cleft

the cell that transmits the signal = presynaptic cell the cell receiving the signal = postsynaptic cell space between the two = synaptic cleft Together, these three components make up the SYNAPSE.

What does the Nernst equation calculate?

the equilibrium potential for an ion

Define equilibrium potential.

the membrane potential at which an ion is at its equilibrium distribution across a membrane (the chemical and electrical forces are equal and opposite)

What happens to the charge difference during hyperpolarization?

the membrane potential becomes more negative; either negatively charged ions enter the cell or positively charged ions move out of the cell

What is repolarization?

the membrane returns to its resting membrane potential, following a depolarization or hyperpolarization

Define: saltatory conduction

the mode of conduction of action potentials in myelinated axons in which action potentials appear to jump from one node of Ranvier to the next

What might determine the value for maximal flux of a mediated-transport system?

the number of transporter molecules in the membrane and the rate of conformational change when binding solute

Define: electrotonic current spread.

the passive conduction of charge along a cell membrane; occurs because of electrical interactions inside the neuron

What does the Goldman equation calculate?

the resting membrane potential based on the concentrations and permeabilizes of all of the relevant ions

Define: neuromuscular junction

the synapse between a motor neuron and a skeletal muscle cell

What is the cranial relay neuron responsible for?

used to ensure that the M neuron that successful fired does not fire a second time

Define: synaptic vesicles

vesicles that contain neurotransmitters that release neurotransmitter into a synapse

Define resting membrane potential.

voltage difference when the cell is not involved in sending an electrical signal (Vm)

Which one is more diverse: Na+ or K+ voltage-gated channels?

voltage-gated K+ channels = more diverse

What types of channels, when opening and closing, cause the characteristic phases of the action potential?

voltage-gated ion channels

When will an axon fire an action potential?

when a graded potential causes the membrane potential at the axon hillock to depolarize beyond the threshold potential