Nerve Signaling

Question 1

nerve/neuron

Answer 1

the fundamental unit of signal processing; an electrically excitable cell that processes and transmits information through electrical and chemical signals.

Question 2

dendrite

Answer 2

the structures on the neuron that receive electrical messages. These messages come in two basic forms: excitatory and inhibitory.

Question 3

axon

Answer 3

a long, slender projection of a nerve cell, or neuron, that typically conducts electrical impulses away from the neuron’s cell body

Question 4

membrane potential

Answer 4

the difference in electric potential between the interior and the exterior of a biological cell. Typical values of membrane potential range from –40 mV to –80 mV.

Question 5

resting potential

Answer 5

has a value of approximately −70 mV. The resting potential is mostly determined by the concentrations of the ions in the fluids on both sides of the cell membrane and the ion transport proteins that are in the cell membrane

Question 6

action potential

Answer 6

play a central role in cell-to-cell communication by providing for (or assisting in, with regard to saltatory conduction) the propagation of signals along the neuron’s axon towards boutons at the axon ends which can then connect with other neurons at synapses, or to motor cells or glands.

Question 7

depolarization

Answer 7

a sudden change within a cell, during which the cell undergoes a dramatic electrical change

Question 8

repolarization

Answer 8

the change in membrane potential that returns it to a negative value just after the depolarization phase of an action potential has changed the membrane potential to a positive value

Question 9

hyperpolarization

Answer 9

a change in a cell’s membrane potential that makes it more negative. It is the opposite of a depolarization.

Question 10

voltage-gated channel

Answer 10

form ion channels that are activated by changes in the electrical membrane potential near the channel. The membrane potential alters the conformation of the channel proteins, regulating their opening and closing. Cell membranes are generally impermeable to ions, thus they must diffuse through the membrane through transmembrane protein channels.

Question 11

neurotoxin

Answer 11

are poisonous or destructive to nerve tissue

Question 12

neurotransmitter

Answer 12

chemical messengers

Question 13

synapse

Answer 13

structure that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron

Question 14

synaptic vesicles

Answer 14

stores various neurotransmitters that are released at the synapse. The release is regulated by a voltage-dependent calcium channel. Vesicles are essential for propagating nerve impulses between neurons and are constantly recreated by the c

Question 15

presynaptic neuron

Answer 15

one that releases a neurotransmitter in response to an action potential.

Question 16

postsynaptic neuron

Answer 16

receives the neurotransmitter and may undergo an action potential (and become a presynaptic to the next nerve cell) if the NTs stimulate the cell enough.

Question 17

synaptic cleft

Answer 17

between the neurons

Question 18

ligand

Answer 18

a molecule which produces a signal by binding to a site on a target protein.

Question 19

ligand-gated channels

Answer 19

opens and allows ions to cross the membrane.

Question 20

Explain how nerves transmit information long distances

Answer 20

A signal is received by dendrites. A signal is produced by the axon branches. Each neuron is connected to thousands of other neurons.

Question 21

Describe how the resting potential in neurons is created and maintained

Answer 21

a result of different concentrations of Na+ and K+ ions inside and outside the cell. A nerve impulse causes Na+ to enter the cell, resulting in (b) depolarization. … The actions of the sodium-potassium pump help to maintain the resting potential, once it is established.

Question 22

Explain how an action potential is initiated and propagated in a neuron

Answer 22

Action potentials are formed when a stimulus causes the cell membrane to depolarize past the threshold of excitation, causing all sodium ion channels to open.
When the potassium ion channels are opened and sodium ion channels are closed, the cell membrane becomes hyperpolarized as potassium ions leave the cell; the cell cannot fire during this refractory period.
The action potential travels down the axon as the membrane of the axon depolarizes and repolarizes.
Myelin insulates the axon to prevent leakage of the current as it travels down the axon.
Nodes of Ranvier are gaps in the myelin along the axons; they contain sodium and potassium ion channels, allowing the action potential to travel quickly down the axon by jumping from one node to the next.

Source: Boundless. “Nerve Impulse Transmission within a Neuron: Action Potential.” Boundless Biology. Boundless, 08 Aug. 2016. Retrieved 04 Oct. 2016 from https://www.boundless.com/biology/textbooks/boundless-biology-textbook/the-nervous-system-35/how-neurons-communicate-200/nerve-impulse-transmission-within-a-neuron-action-potential-762-11995/

Question 23

Compare and contrast the activity of ligand-gated Na+ channels, voltage-gated Na+
channels, voltage-gated K+ channels, and the Na+/K+-ATPase

Answer 23

VG Na+ channels have both an activation and an inactivation gate, while VG K+ channels have only an activation gate.

When the membrane potential reaches the threshold, the cell begins to depolarize, which causes the Na+ activation gate to open (inactivation gate is open at resting too) and Na+ rushes in causing further depolarization of the cell. this depolarization causes the K+ activation gate to open and K+ rushes out causing the cell to repolarize. depolarization causes the inactivation Na+ gate to close and stops Na+ from coming in. K+ gates stay open and hyper polarization begins to occur. K+ activation gate closes at membrane potential and all gates return to normal until the process starts again.

Question 24

Explain how the electrical signal of an action potential is converted into the chemical signal at
a synapse

Answer 24

A typical neuron has a cell body (soma), branching processes specialized to receive incoming signals (dendrites), and a single process (axon) that carries electrical signals away from the neuron toward other neurons or effectors. Electrical signals carried by axons are action potentials . Axons often have thousands of terminal branches, each ending as a bulbous enlargement, the synaptic knob or synaptic terminal. At the synaptic knob, the action potential is converted into a chemical message which, in turn, interacts with the recipient neuron or effector. This process is synaptic transmission.

Question 25

Trace the “life” of a neurotransmitter from its synthesis to degradation/reuptake.

Answer 25

?

Question 26

Digoxin (or Digitalis, since it’s purified from the foxglove plant Digitalis lanata) is a drug used to
treat atrial fibrillation and atrial flutter, conditions in which the heart beats irregularly fast and can
lead to heart failure. Digoxin binds and blocks the Na+/K+-ATPase. How does this drug work to
slow down the heart? It doesn’t actually have anything directly to do with action potentials!
What is the mechanism of action of the venom of the Taiwanese banded krait (Bungarus
multicinctus)?

Answer 26

? a purified cardiac glycoside similar to digitoxin extracted from the foxglove plant, Digitalis lanata.[Digoxin is occasionally used in the treatment of various heart conditions, namely atrial fibrillation, atrial flutter and sometimes heart failure that cannot be controlled by other medication.

There are concerns that its general use may increase the risk of death.

By slowing down the conduction in the AV node and increasing its refractory period, digoxin can reduce the ventricular rate. The arrhythmia itself is not affected, but the pumping function of the heart improves, owing to improved filling.