Introduction to Neurons, Nerve Conduction and Synaptic Transmission Flashcards by Caroline Maguire

What do dendrites do?

Receive input from other neurones
Convey graded electrical signals to the soma
Add surface area to the neurone

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How are electrical signals conveyed to the soma?

Graded

PASSIVELY

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What is the soma aka?

Perikaryon

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What is the soma the centre of?

Synthesis and metabolism

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What does the soma contain?

Nucleus
Ribosomes
Mitochondria
ER

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What does the soma integrate?

Incoming signals that are conducted passively to the axon hillock

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What occurs at the axon hillock?

Initiation of the ‘all or none’ action potential

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What does the axon do?

Conducts output signals as action potentials to other cells/neurons
Mediate transport materials between the soma and the presynaptic terminal

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What can viruses do to a neuron? Give examples of such viruses.

Affect retrograde transport

Herpes, Polio, Rabies

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What direction does the axon transport materials in?

ANTEROGRADE
or
RETROGRADE

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Dendrites can be either…..

Apical or Basal

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Unipolar

1 neutrite

e.g PNS

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Pseudounipolar

1 neutrite that bifurcates

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Bipolar

2 neutrites

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Multipolar

3/+ neutrites

e.g LMN

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How many functional regions do most neurones have?

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Name the 4 functional regions of a neurone.

Input
Integrative
Conductile
Output

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What causes the upstroke of an AP in neurones?

The opening of voltage activated Na+ channels

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What is ‘over-shoot’?

A brief period when polarity is reversed to inside positive

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What causes the downstroke of an AP in neurones?

The opening of voltage activated K+ channels

and the closure of activated Na+ channels

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Why does undershoot occur?

Because K+ channels don’t close immediately once membrane potential is reached

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The nerve cell membrane is ‘leaky’. Explain this.

Not a perfect insulator

Passive signals don’t spread far from their site of origin due to current loss across the membrane

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The amplitude of an AP is….

CONSTANT

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Current leaks back to what across the membrane resistance (rm)?

Extracellular space

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What does current leaking to the extracellular space generate?

Generates a potential change (Vm)

For a given current (I), Vm increases linearly with rm

TRUE

Describe the process of membrane potential change.

PASSIVE | Decays exponentially with distance

What does the distance over which current spreads depend on?

Membrane resistance (rm) AND Axial resistance of the axoplasm (ri)

What decreases resistance?

Increasing diameter | Decreasing distance of travel

What is passive conduction a factor in?

The propagation of an AP

What is the relationship between the length constant and local current spread?

The longer the length constant (λ) the greater the local current spread

What does greater local current spread increase?

AP conduction velocity

What does increasing axonal diameter do?

Decreases ri

What does adding myelin do?

Increases rm

Schwann cells surround a ...... axon

SINGLE

Oligodendrocytes surround .... axons

MANY

Conduction in myelinated axons is THE SAME AS/ FASTER than in non-myelinated axons of the same diameter

FASTER

Where do AP's 'jump' from?

One node of ranvier to another

What do you find clusters of at NOR?

Voltage activated Na+ channels

Name 2 demyelinating disorders?

MS | Guillian-Barre Syndrome

Name the 3 types of synapse.

Axodendritis Axosomatic Axoaxonic

Name the 3 types of synapse in order from most common to least common.

Axodendritis Axosomatic Axoaxonic

What neurotransmitter is most frequently used for EXCITATORY synapse?

Glutamate

What does glutamate activate?

Activates postsynaptic, cation selective, ionotropic, glutamate receptors.

What is the outcome of glutamate activation?

This generates a local, graded excitatory (depolarizing) response: the excitatory postsynaptic potential (epsp).

What does glutamate activate?

Activates postsynaptic, CATION selective, ionotropic, glutamate receptors.

What neurotransmitter is most frequently used for INHIBITORY synapse?

-aminobutyric acid (GABA), or glycine

What does y-aminobutyric acid (GABA) and glycine activate?

Activate postsynaptic, ANION selective, ionotropic, GABAA, or glycine, receptors.

What do the INHIBITORY neurotransmitters generate?

This generates a local, graded, inhibitory (hyperpolarizing) response: the inhibitory postsynaptic potential (i.p.s.p.)

What are the major amino acid neurotransmitters in the CNS?

Glutamate, glycine and GABA

What are pre and post synaptic membranes separated by?

Synaptic cleft

What is the synaptic cleft composed of?

A matrix of extracellular proteins

What are the membrane differentiations i) presynaptically? Ii) postsynaptically?

i) the active zones around which vesicles cluster | ii) the postsynaptic density containing neurotransmitter receptors

What is the information transfer sequence in the CNS?

1. Electrical 2. Chemical 3. Electrical

Many inputs converge upon a neurone to determine its input is know as?

SPATIAL summation

A single input may modulate output by variation in action potential frequency of that input

TEMPORAL summation

Physiologically, spatial and temporal summation isolated/complementary processes

COMPLEMENTARY

Name the 3 main types of neurotransmitter substance.

Amino acids Amines Peptides

What type of neurotransmitter are released from synaptic vesicles?

Amino acids and amines

What type of neurotransmitter is released from secretory vesicles?

Peptides

What can Glutamate, GABA, glycine, acetylcholine, and 5-HT activate? What do these mediate?

Ionotropic ligand-gated ion channels (LGICs) | Mediate fast neurotransmission

GPCRs mediate relatively slow neurotransmission

TRUE

Glycine and Glutamate only occur in neurones

FALSE | They occur in all other cells

What must be specifically synthesized by neurones that release glycine and glutamate? What does this require?

GABA and amines | They need specific enzymes

What is neurotransmitter concentrated in the vesicles by?

Transporters embedded in the vesicle membrane

At the terminal, what do enzymes mediate?

Synthesis of neurotransmitter from precursor substances within the cytoplasm

Outline the process of synthesis and storage of peptide neurotransmitters

1. Synthesis of precursor peptide by ribosomes in the RER 2. Cleavage of precursor in Golgi by active neurotransmitter 3. Secretory vesicles budd off from Golgi 4. Secretory granules are transported to the presynaptic terminal by fast axoplasmic transport via microtubules

Introduction to Neurons, Nerve Conduction and Synaptic Transmission Flashcards

(67 cards)