4 - Synaptic and Neuromuscular Transmission

1. multipolar

2. bipolar

3. unipolar

What are the 3 neuron structural types?

gap junctions

With an electrical synapse, the current flows between cells via _____

synaptic cleft

Gap between presynaptic and postsynaptic cells

chemical

The following are associated with a(n) [electrical/chemical] synapse:

1. AP in presynaptic cell causes voltage-gated Ca2+ channels to open

2. Ca2+ influx causes release of neurotransmitter from presynaptic terminal

3. Neurotransmitter binds ligand-gated Na+ channel on postsynaptic cell, leading to depolarization (can be excitatory or inhibitory)

circuits

Neurons are arranged in _____ where input cells synapse on output cells

input cells

Output cell may or may not fire an action potential depending on amount of excitation provided by the _____

one-to-one

_____ synapses:

-Neuromuscular junction

-Single AP in motoneuron causes single AP in muscle fiber

one-to-many

_____ synapses:

-Found in some motoneurons of spinalcord

-Single AP in motoneurons causes many APs in postsynaptic cells

many-to-one

_____ synapses:

-Many presynaptic cells converge on a postsynaptic cell

-Common

many-to-one

Postsynaptic potentials commonly use _____ synapse arrangement

excitatory

The following are associated with [excitatory/inhibitory] postsynaptic potentials:

-Pre-synaptic neuron depolarizes post-synaptic neuron, brings neuron's membrane potential to threshold, opens Na and K channels

-Ach, NE, Epi, dopamine, glutamate, serotonin are excitatory neurotransmitters

inhibitory

The following are associated with [excitatory/inhibitory] postsynaptic potentials:

-Pre-synaptic neuron hyperpolarizes post-synaptic neuron and membrane potential moves away from threshold, opens Cl channels

-GABA, glycine are inhibitory neurotransmitters

1. spatial summation

2. temporal summation

3. synaptic fatigue

What are the 3 ways synaptic inputs get integrated?

spatial summation

Two or more inputs arrive at postsynaptic cell simultaneously

temporal summation

Two inputs arrive at postsynaptic cell in rapid succession

synaptic fatigue

Repeated stimulation yields a

smaller than expected response

ionotropic receptors

-Ligand-gated ion channels that usually open in response to binding of neurotransmitter

-Usually located along dendrites or cell bodies and receive incoming information from other neurons

Na

A post-synaptic neuron may be excited due to _____ influx causing depolarization

K; chloride

A post synaptic neuron may be inhibited due to either _____ efflux or _____ influx causing hyperpolarization

1. glutamate

2. acetylcholine

3. glycine

4. GABA

What are the 4 neurotransmitters that activate ionotropic receptors?

glutamate

-Neurotransmitter that activates ionotropic receptors

-Primary excitatory neurotransmitters in the CNS

acetylcholine

-Neurotransmitter that activates ionotropic receptors

-Only neurotransmitter used at neuromuscular junction

-Also used by autonomic nervous system (PSNS and SNS)

glycine & GABA

-Neurotransmitters that activate ionotropic receptors

-Both neurotransmitters are used

in the CNS and both are chloride

channels

-Binding of these causes inhibition,

since increase in Cl permeability is

inhibitorys

metabotropic receptors

-Located along dendrites or cell bodies, receive incoming information, slower than ionotropic receptors

-Can use G-protein-coupled receptors (GPCR)

norepinephrine (NE)

-Neurotransmitter that activates G-protein-coupled receptors

-Uses alpha- or beta-adrenergic receptors

glutamate

-Neurotransmitter that activates G-protein-coupled receptors

-Metabotropic receptor

-Acts on post-synaptic sites in CNS

-Modulates cell excitability and

synaptic transmission via second

messenger pathways

-3 groups

GABA

-Neurotransmitter that activates G-protein-coupled receptors

-Found in CNS and autonomicdivision of peripheral nervoussystem

neuropeptides

Synthesized and packaged innerve cell body instead of axon terminal

neuromodulators

-May act on pre-synaptic cell to alter amount of neurotransmitter released

-May be co-secreted with neurotransmitter to alter response of post-synaptic cell

neurohormones

Released from neurons into blood

cell body

The different neuron structure types are based on the # of processes that extend from the _____

multipolar

Neuron structure - 3 or more processes extending from the cell body

multipolar

What is the major neuron type in the CNS and efferent PNS?

bipolar

Neuron structure - 2 processes extending from cell body in opposite directions - dendrite & axon

retina & olfactory system

Where will we find bipolar neurons?

unipolar

- Neuron structure - single short process from the cell body, branching into 2 or more

-peripheral process associated with sensory perception

-central process goes toward the CNS

afferent PNS

Where will we find unipolar neurons?

electrical

[Electrical/chemical] synapse:

-Fast & has ability to stimulate cells simultaneously

-Found in cardiac tissue

-Found in some smooth muscle

chemical

AP moves from the presynaptic to postsynaptic cell through a _____ synapse

chemical

[Electrical/chemical] synapse is slower

get neurotransmitter released from the presynaptic cell and get it to the postsynaptic cell

What is the goal with chemical synapse?

calcium

The goal of a chemical synapse is to get neurotransmitter released from the presynaptic cell and get it to the postsynaptic cell. In order to do that, we need an AP to occur. In order for that to happen, we need to voltage gated _____ channels to open.

neurotransmitters

When calcium rushes to the post synaptic cell, it causes the vesicles that have _____ in them to move to the cell membrane and get released, for receptor binding.

ligand-gated

Neurotransmitters bind _____ channel on the postsynaptic cell, leading to depolarization or hyperpolarization

depolarization

Excitatory response = _____polarization

hyperpolarization

Inhibitory response =_____polarization

many-to-one

What is the most common type of synapse?

need convergence of multiple input neurons to cause an AP = sum the inputs

With a many-to-one synapse, you are getting many inputs from many neurons, so info is coming in from multiple neurons all the time. What do we need in order to cause an AP?

excitation

When converging multiple input neurons to cause an AP, if our net is depolarization, that -> _____

inhibition

When converging multiple input neurons to cause an AP, if our net is hyperpolarization, that -> _____

excitatory

Ach, NE, Epi, dopamine, glutamate, and serotonin are _____ neurotransmitters

depolarize

Excitatory postsynaptic potentials -> [depolarize/hyperpolarize]

hyperpolarize

Inhibitory postsynaptic potentials -> [depolarize/hyperpolarize]

inhibitory

GABA and glycine are _____ neurotransmitters

-both inputs could be excitatory -> summation -> depolarization

-one could be excitatory & other inhibitory -> nothing

-both inputs could be inhibitory -> hyperpolarize -> further from threshold

With spatial summation, 2 or more inputs arrive at the postsynaptic cell at the same time. What happens (3)?

depolarization

Both inputs could be excitatory -> summation -> _____

hyperpolarization

Both inputs could be inhibitory -> _____ -> further from threshold

nothing/ cancel out

One input could be excitatory & other inhibitory -> _____

effects are additive

- could have 2 excitatory, one after another

- could have 1 excitatory & 1 inhibitory, one after another

With temporal summation, 2 inputs arrive at the postsynaptic cell in rapid succession (get one and then the other). What happens?

additive

With temporal summation, the effects are _____

smaller

Synaptic fatigue -> [smaller/larger] than expected response

may or may not cause depolarization

(Ca usually associated with 2nd messenger system)

What if there is a Ca influx from an ionotropic receptor interaction?

1. AMPA

2. NMDA

What are the 2 types of glutamate receptors?

AMPA

Allows both Na and K to cross the membrane, but the gradient that drives Na is the strongest one -> net effect is depolarization

Na; depolarization

AMPA allows Na and K to cross the membrane, but the gradient that drives _____ is stronger -> _____

NMDA

Depends on both glutamate binding and voltage, so when you are around resting membrane potential , there is a magnesium ion that blocks the binding site/ movement of other ions -> when glutamate binds and cell depolarizes -> magnesium block is removed

magnesium; magnesium

NMDA depends on both glutamate binding and voltage, so when you are around resting membrane potential , there is a _____ ion that blocks the binding site/ movement of other ions -> when glutamate binds and cell depolarizes -> _____ block is removed

inhibition

Binding of the glycine and GABA neurotransmitters will cause _____, because of increase in Cl permeability

chloride

GABA sub A is associated with _____

G; Gdp

In the system associated with metabotropic receptors, when we get binding, we get a _____ protein that's activated and a G protein alpha subunit that binds to _____

potassium; 2nd messenger synthesis

G protein beta subunit may activate ion channel like _____ while the alpha subunit may activate enzymes that are promoting _____

phospholipase C; adenylyl cyclase

Enzymes used in the 2nd messenger systems are ______ and _____

-activating enzymes, like protein kinases

-phosphorylate something & set off cascade of events in the cell

What is the goal when you set off cascade of the 2nd messenger system?

initiates cAMP second messenger system

Beta adrenergic GPCRs = _____

suppress cAMP system

Alpha 2 adrenergic receptors = _____

activate phospholipase C second messenger system

Alpha 1 adrenergic receptors = _____

increase neuron excitability & activate phospholipase C pathway

Glutamate activates 3 groups of G-protein coupled receptors. Group 1 does what?

suppress neuron excitability & inhibit adenylyl cyclase pathway

Glutamate activates 3 groups of G-protein coupled receptors. Groups 2 and 3 do what?

hyper

GABA _____polarizes the cell when we get an AP

biochemical

We can group neurotransmitters based on their _____ properties

biogenic amines

Acetylcholine belongs to a group of _____, along with NE, Epi, DA, serotonin, and histamine

amino acids

Glutamate, glycine, and GABA are all examples of _____

neurotransmitter

Neuropeptides are neuromodulators, which have the ability to act on the presynaptic cell to change how much of a _____ is released

postsynaptic

Neuropeptides are neuromodulators, which have the ability to be cosecreted along with the neurotransmitter, so the action is on the _____ cell

longer

Neurohormones travel a [shorter/longer] distance

modulators

VIP and Substance P are commonly acting as neuro_____