Flashcards in Physiology Deck (91)
Where on the neurone decides whether to initiate an all or nothing action potential?
Unipolar neurones occur where?
Pseudounipolar neurones occur where?
Dorsal root ganglion
Bipolar neurones occur where?
Retinal bipolar neurone
Multipolar neurones occur where?
Lower motor neurones
What triggers the upstroke within a neuronal AP?
Na + influx
Voltage gated Na+ channels
What triggers the downstroke within a neuronal AP?
Voltage gated K+ channels
Why if signalling was passive would the AP diminish as it travels along the neurone?
The membrane is leaky allowing ions to exit the axon and reducing the concentration gradient reducing speed of transmission.
Saltatory Conduction is enabled by what?
The nodes of Ranvier formed between myelin sheath.
Why does myelination increase the speed of conduction?
As it insulates the axons preventing leakage of ions and maintaining the concentration gradient.
Ion channels only located at nodes thus conduction jumps from one node to the next.
How would you increase the passive conduction speed of a neurone?
Decrease Ri - Increase axon diameter
Increase Rm - Add insulating material
Influx of what ion causes the exocytosis of vesicles containing the neurotransmitter?
What types of synapse are there?
Synapse between axon and dendrite
Synapse between axon and Soma ( cell body )
Synapse between axon and axon
What is the main excitatory neurotransmitter?
How does Glutamate cause an increased +ve AP?
Activates postsynaptic Cation selective channels
What is the main inhibitory neurotransmitter?
How does GABA cause an increased -ve AP?
Activates postsynaptic anion selective channels
Influx of Cl- ion
What are the two main forms of synaptic summation?
Spatial and Temporal Summation
What is the purpose behind summation?
Calculation of excitatory and inhibitory AP that responds too many stimuli from the surroundings allowing a proportionate response.
Convergence of many inputs upon a neurone to determine its output.
Determined by the axon hillock whether the sum of the AP input is enough to surpass the threshold to trigger an all or nothing response.
If a single input fires frequently enough it can trigger an all or nothing response.
Direct postsynaptic membrane potential is activated by...
Why do inotropic receptors result in rapid opening of the ion channels?
Ionotropic receptors are integral to the ion gates
Indirect postsynaptic membrane potential is mediated by
Metabotropic receptors result in rapid opening of ion channels? T/F
False - Activation results in slow opening of ion channels
Why does metabotropic receptors cause a slow opening of ion channels?
G - protein coupled receptor
Receptor is separate to the ion channel