Neurones, Nerve Conduction and Synaptic Transmission Flashcards
Receive input from other neurones and conveys graded electrical signals passively to the soma.
Dendrites.
The synthetic and metabolic centre of a neurone containing the nucleus, ribosomes, mitochondria and endoplasmic reticulum.
Cell body (soma).
Part of the neurone that integrates incoming electrical signals that are conducted passively to the axon hillock.
Cell body (soma).
Site of initiation of the “all or none” action potential in a neurone.
Axon hillock and initial segment.
Conducts output signals as action potentials to the presynaptic terminal and mediates material transport between soma and presynaptic terminal by slow and fast axonal transport.
Axon.
Point of (typically) chemical communication between neurones or other cells.
Synapse.
What type of neurone has one neurite? Give an example.
Unipolar.
- Peripheral autonomic neurone.
What type of neurone has one neurite that bifurcates? Give an example.
Pseudounipolar.
- Dorsal root ganglion neurone.
What type of neurone has two neurites? Give an example.
Bipolar.
- Retinal bipolar neurone.
What type of neurone has three or more neurites? Give an example.
Multipolar.
- Lower motor neurone.
What are the four functional regions present in most neurones?
- Input.
- Integrative.
- Conductile.
- Output.
Where might a sensory neurone be found running from and to?
From skin to dorsal horn of spinal cord.
Where might a motor neurone be found running from and to?
From ventral horn of spinal cord to skeletal muscle.
Where might a local interneurone be found running from and to?
Between neurones in the CNS.
Where might a projection neurone be found running from and to?
From dorsal horn of spinal cord to brain structures.
What causes depolarisation in neurones?
Opening of voltage-activated Na+ channels allowing Na+ influx.
What causes repolarisation in neurones?
Opening of voltage-activated K+ channels allowing K+ efflux.
What is the purpose of action potentials?
To allow electrical signals to be conducted over large distances without decaying.
Why do passive signals not spread far from their site of origin in a nerve cell?
Due to leaky membrane causing current loss and thus a reduced change in potential.
What factors may increase passive current spread and thus action potential velocity?
- Decrease ri (axial resistance of axoplasm) by increasing axon diameter.
- Increase rm (membrane resistance) by adding myelin.
What provides myelin in PNS?
Schwann cells.
What provides myelin in the CNS?
Oligodendrocytes.
Schwann cells and oligodendrocytes are both type of what cell?
Macroglia.
Demyelinating disorders have what effect on nerve conduction?
Slow or even stop the nerve conduction.
Give an example of a demyelinating disorder.
- Multiple sclerosis.
- Guillian-Barre Syndrome
What separates pre- and post-synaptic membranes?
A narrow synaptic cleft.
What holds the pre- and post-synaptic membranes together?
A matrix of extracellular proteins within the synaptic cleft.
What within the presynaptic terminal stores neurotransmitter?
Vesicles.
How are synapses classified morphologically?
By the location of the presynaptic terminal upon the postsynaptic cell.
What is the most frequently found transmitter in the CNS for excitatory synapses?
Glutamate.
Glutamate activates certain CNS receptors to generate what?
A local, graded, excitatory and depolarising response known as the excitatory postsynaptic potential e.p.s.p.
What is the most frequently found transmitter in the CNS for inhibitory synapses?
γ- Aminobutyric acid (GABA) or glycine.
γ- Aminobutyric acid (GABA) or glycine activates certain CNS receptors to generate what?
Local, graded, inhibitory (hyperpolarising) response known as the inhibitory postsynaptic potential (i.p.s.p).
What are the major amino acid neurotransmitters in the CNS?
Glutamate, GABA and glycine.
Where are peptides released from?
Secretory vesicles.
Synaptic vesicles release what?
- Acetylcholine.
- Amino acids.
- Amines.
Glutamate, GABA, Glycine, Acetylcholine and 5-HT can activate what?
Ionotropic ligand-gated ion channels (LGICs).
What do ionotropic ligand-gated ion channels mediate?
Fast neurotransmission.
Which of the following can NOT activate metabotropic G-protein-couple receptors?
- Glutamate.
- GABA.
- Glycine.
- Acetylcholine.
- 5-HT.
Glycine.
What do G-protein-coupled (metabotropic) receptors mediate?
Relatively slow neurotransmission.
The major excitatory neurotransmitter.
- Acts on ionotropic receptors to allow Na and Ca into cell, and K out.
- Net result of action is EPSP, depolarisation and excitation.
Glutamate.
Major inhibitory neurotransmitter.
- Acts on ionotropic receptors to allow Cl into cell.
- Net result of action is IPSP, hyperpolarisation and inhibition.
GABA
Locally-acting neurone, typically releases GABA to bring about an IPSP and inhibition.
Function is the local processing of information.
Interneurone.
Neuron responsible for conveying signal to other parts of the brain.
- Typically releases glutamate to bring about an EPSP.
Projection neuron.
Releases depolarising neurotransmitter e.g. glutamate.
Excitatory neuron.
Releases hyperpolarising neurotransmitter e.g. GABA.
Inhibitory neuron.
