Week 2 - A - Pharmacology 1 - Into to neurone, conduction and synaptic trasmission Flashcards
Neurones can be divided into morphological regions with distinct roles What are the different regions of the neruone? What is the perikaryon of the neuron also known as?
- Dendrites
- Soma (cell body)
- Axon hillock and initial segement
- Axon
- Synapse
- Perikaryon is the cell body of the neuron containing the nucleus
Neurones only cunt for 1/10th of the total number of cells in the nervous system – vast majority are glial cells What is the fucntion of the dendrite?
Dendrites increase the overall surface area of the neuron and are able to convey graded electrical signals from one neuron to the cell body of another
Once electrical signals have been passed from dendrite to soma, where is it passed to? Where is the nucleus of the cell found? What is the function of the Nissl substance in the cell body?
Soma conveys electrical signals passively to the axon hillock Nucleus of the cell is found in the cell body (soma) (perikaryon) Nissle substance has the same function as the rough ER and it manufactures and releases proteins
The axon hillock is the site of the all or nothing action potential which then travels to the initial segment and to the axon The axon can either transport materials between the soma to presynaptic terminal (the normal direction) or presynaptic terminal to soma (wrong direction) What are each ofthese directions known as?
Soma to presynaptic terminal - anterograde direction Presynaptic terminal to soma - retrograde direction
Synapse: point of chemical (usually) communication between neurones (or other cells) The axons typically branches at its far end into synaptic boutons and release a neurotransmitter What is the space between synaptic bouton and membrane of of other synapctic cell known as?
This is known as the synaptic cleft
Several virus exploit retrograde transport to infect neurones What is retrograde transport? Give examples of these neurones?
Retrograde transport - this is where the virus travels from presynaptic terminal to soma Rabies, herpes an polio are examples of this
What is a neurite?
This is the neuronal process that projects from the cell body, can be an axon or dendrite
What are the four different classifications of neurone according to its shape and number of neurites? Describe each?
Unipolar - one neurite leaves the cell body Pseudounipolar - one neurite leaves the cell body and bifurcates Bipolar - two neurties emerging from the soma Multipolar - three or more neurites emerging from the soma
Which type of neuron is extremenly common in sensation? Try remember the retina of the eye?
Bipolar neurones are extremely common in sensation
We know that neurones have different structural regions, what are these? What are the functional regions of the neuron?
Dendrite, soma, axon, axon hillock+initial segment, synapse Functional region - input (dendrite), integrative (cell body), conductile (axon), output (synapse)
What is the resting membrane potenital of a nerve cell? What channels open to cause depolarization of the cell? What channels open to cause hyperpolariation of the cell?
Resting membrane potential = -70mV Voltage activated sodium channels open to allow the cell to depolarise (Na+ influx) Voltage activated potassium channels open and sodium channels close to allow the cell to hyperpolarize (K+ efflux)
Action Potentials Allow Electrical Signals to be Conducted Over Large Distances Without Decaying The nerve cell membrane is ‘leaky’ (i.e. not a perfect insulator): passive signals do not spread far from their site of origin due to current loss across the membrane (imagine a leaky garden hose as an analogy for the axon) What can insulate the nerve axon to prevent the leakiness?
Myelin insulates the axon
The distance over which current spreads depends upon membrane resistance (Rm) and the axial resistance of the axoplasm (Ri) How can the axial reisstance of the axoplasm be decreased? How can the membrane resistance of the axon be decreased?
Axial resistance can be decreased by increasing the diameter of the axon Membrane resistance can be decreased by adding an insulating sheath to lower the current loss across the membrane
What are the macroglial cells that produce myelin in the CNS and PNS?
Mylein is produced by oligodendrocytes in the CNS and Schwann cells in the PNS
Conduction in myelinated axons is much faster than in nonmyelinated axons of the same diameter What are the nodes along the myelin sheath known as where the action potential seems to “jump” from one node to the next along the axon? What is this type of conduction known as and what does it help with?
These are the nodes of Ranvier Known as saltatory conduction (saltare - to hop or leap in latin) This type of conduction speads up the conduction of action potentials
When glutamate is released from the vesicles in the presynaptic cleft, what channels will it act on to generate the excitatory postsynaptic potential? When GABA or glycine is released from the vesicles in the presynaptic cleft, what channels will they act on to generate the inhibitory postynaptic potential?
Glutamate acts on the sodium channels and causes influx of the sodium depolarizing the cell GABA (y-aminobutyric acid) and glycine act on chloride channels causing chlorine to enter the cell and hyperpolarize it (negatively charged)
