Voltage Gated Channels and Synaptic Transmission - Dr. Sylvester - Exam 1 - Pathophysiology 1

Voltage-gated ion channels are _________ for specific ions.

selectively permeable

T/F: Voltage-gated ion channels are coded for by many different genes.

T

T/F: All voltage-gated ion channels have the same structure, function, & are located in the same places in tissues.

F: thy are different in their own ways

There is one voltage sensitive ______ channel that does not inactivate & causes prolonged APs. Some can be found in the heart, & these are a big target for local anesthetics.

Na

________ ion channels can be activated by the extracellular presence of neurotransmitters or by intracellular second messengers.

ligand-gated

intracellular second messangers include _______ & _______

Ca2+, cyclic nucleotides (cAMP, cGMP)

Like Na+, ______ can cause APs using voltage-gates channels.

Ca2+

_______ can control the shape of APs generated primarily by Na+ conductance changes.

Ca2+

Intracellular ______ concentrations affect the activity of their channels & regulate a wide range of biochemical processes within cells, particularly neurotransmitter release.

Ca2+

______ different genes have been identified to code for Ca2+ channels.

16

Because of ______ role in so many biochemical processes, drugs that block these voltage-gated channels are valuable in treating a variety of health conditions like heart disease & anxiety.

Ca2+

_______ is required for neurotransmitter release.

Ca2+

What is the largest & most diverse class of voltage-gated ion channels?

K

About ______ different genes code for K channels, which differ substantially in their gating properties.

100

The most important function of K is to maintain _________.

resting membrane potential

___________ functions are to control excitability, contribute to resting membrane potential, & help regulate cell volume

voltage-gated Cl- channels

_______ is an inhibitory neurotransmitter that causes an influx of Cl- to hyperpolarize a neuron.

GABA

T/F: Channels are ion specific, but similarly sized & charged ions may sometimes travel through them.

True

What are the 3 units of voltage-gated channels?

- voltage sensor

- pore

- gate

Na, K, & Ca2+ channels are composed of _____ transmembrane _____-subunits arranged around a central pore.

4; alpha

Each alpha-subunit of a voltage-gated ion channel is composed of ______ segments.

6

Segments ______ of an alpha-subunit in a voltage-gated ion channel act as voltage sensors while segments ______ act as pore & gate regulators.

1-4, 5-6

in addition to having 4 alpha-subunits, each voltage-gated ion channel also has _____ regulatory beta-subunits.

2

The human brain has at least _______ neurons that can influence many other cells.

100 billion

Communication between neurons is made possible by _______, the functional contacts between neurons

synapses

What are the 2 classes of synapses?

electrical and chemical

_________ synapses permit direct, passive flow of electrical current from one neuron to another. The current flows through _______, which are specialized membrane channels that connect 2 cells.

Electrical, gap junctions

_______ synapses enable cell to cell communication via secretion of neurotransmitters.

Chemical

_________ arechemical agents released by the presynaptic neuron that produce secondary current flow in post synaptic neurons by activating specific receptors

neurotransmitters

Neurotransmitter secretion is triggered by an influx of _______ through voltage-gated channels to give rise to a transient increase in ion levels within the presynaptic terminal.

Ca2+

Increase in _______ causes synaptic vesicles to fuse with the presynaptic plasma membrane & release their contents into the synapse by exocytosis.

Ca2+

The _______ of neurons determine how neurons act.

receptors

________ is a class I neurotransmitter

acetylcholine (ACh)

biogenic amines:

- catecholamines (epinephrine, norepinephrine, dopamine)

- serotonin

- histamine

are ____________ neurotransmitters

class II neurotransmitters

amino acid neurotransmitters:

- GABA

- glycine

- glutamate

- aspartate

are __________ neurotransmitters

class III neurotransmitters

Nitrous oxide is a ________ neurotransmitters

class IV neurotransmitter

Many neurotransmitters come from _______

food

Class IV neurotransmitters do not act using _______; they are _______ that act as neurotransmitters.

synapses, gases

Neuropeptide transmitters come from our _______

DNA

_________ are transmitters that act slowly & produce long lasting effects

neuropeptide transmitters

Chemical transmission was discovered by ______ by isolating _________

Loewi, frog hearts

Loewi discovered that nerves release _______ which acts to slow the _______.

Ach, heart

List the steps of chemical synaptic transmission.

1. synthesis of neurotransmitters

2. storage of neurotransmitters

3. release of neurotransmitters

4. binding of neurotransmitters

5. removal of released neurotransmitters

when neurotransmitters that are released into synaptic space are taken back up for reuse by the pre-synaptic neuron

re-uptake

voltage-gated Ca2+ channels open when?

end of AP

The time between Ca2+ influx & postsynaptic response is ________.

0.06 milliseconds

Short delays between Ca2+ influx & exocytosis is important for _________.

synaptic vesicle fusion

T/F: A major fraction of the synaptic delay results from the slow-opening, voltage-gated Ca2+ channels.

T

T/F: There is an unlimited amount of synaptic vesicles in nerve terminals.

F: supply is limited

Fast synaptic transmission involves ________ vesicles, & neurotransmitter must be replenished locally.

recycling

____________ can be synthesized within the nerve terminal or transported rapidly across the nerve terminal membrane.

Small neurotransmitters

_________ must be inserted into secretory granules in the cell body & transported down the axon to the terminal.

Neuropeptides

T/F: The transmission of neuropeptides to a terminal can take hours or days depending on the length of the axon.

T

Neuropeptide transmission is specialized for ________ synaptic transmission & vesicle recycling.

fast

_________ are slower release & have long-lasting effects on postsynaptic cells to compensate for their long transmission process.

Neuropeptides

T/F: Postsynaptic potentials are graded potentials that are localized & different from action potentials.

T

_________ are excitatory or inhibitory, not the neurotransmitters.

Receptors

Neurons receive hundreds to thousands of synaptic inputs. It is the ________ of all of these inputs that results in the membrane reaching threshold or not.

summation

__________ begin to terminate when the neurotransmitter is released from its receptor. Ion channels will then close & membrane returns to resting potential.

Postsynaptic potentials

T/F: Each neuron releases only one kind of neurotransmitter.

F: Most neurons release many different kinds of neurotransmitters.

Low-frequency stimulation preferentially releases __________ at the nerve terminal because Ca2+ is released close to the synaptic membrane where their vesicles are located.

small neurotransmitters

High-frequency stimulation leads to a more diffuse increase of Ca2+ through the terminal, so ________ & ________ are released at the synaptic terminal.

neuropeptides, small neurotransmitters