Neurons and neuron related cells Flashcards
What are the three main functional classes of neurons?
-sensory
-interneuron
-motor
Where in the neuron is an action potential generated?
The axon hillock
What does a neuron do with inputs?
They have the potential to sum up all the incoming inputs and produce a relative output.
What moves down the axon?
Not only electrical activity, also enzymes (constant supply of materials).
What are the Nissl granules in the soma?
This is similar to endoplasmic reticulum (short chains of AAs and proteins).
What is the resting membrane potential in a neuron?
About -70mV.
What is the most abundant intracellular ion?
K+
What is the most abundant extracellular ion?
Na+
What is depolarisation?
Positive synaptic input (becomes more positive).
What is hyper polarisation?
Negative synaptic input (becomes more negative).
How is the resting membrane potential maintained?
K+ and Na+ leak channels that use ATP.
What is the process of a typical chemical synapse between neurons?
-presynaptic neurons release NTs (ACh)
-diffuse across the synaptic cleft
-activate post synaptic neurons on dendrites of post- synaptic cell
-leads to local transient changes in membrane potential
How are chemically gated ions channels opened?
NT attaches to receptor on the ion channel which causes shape to change to let ions through, leads to change in membrane potential.
How is an action potential triggered at the axon hillock?
Once the voltage reaches above the threshold, it generates an AP.
What happens if the stimulus voltage doesn’t reach the threshold?
It dissipates.
What causes the stimulus voltage to reach the threshold?
The local transient change in membrane potential (causes Na+ channels to open to depolarise cell).
What is the refractory period?
Na+ channels can’t be excited/ activated.
AP can only travel in one direction: true or false?
True.
What factors are conduction velocity dependent on?
-axon diameter
-myelination
How does axon diameter influence conduction velocity?
If the axon diameter is wider, it will travel faster (less resistance)
How does myelination influence conduction velocity?
This wraps the axons (layers of fatty cell membrane- insulation) and if lots of myelination, faster signal.
These layers can’t conduct so the signal jumps across and therefore travels faster.
What happens when Ca2+ binds to SNARE protein?
Pulls so close, it fuses.
What does botox do in regards to SNARE?
disrupts the SNARE proteins.
What does the tetanus toxin do in regards to SNARE?
interferes- reduces the inhibitory signals sent to the motor neurons and so they are over-activated (contracted).
What are the ways that the removal of NTs occurs?
-diffusion
-enzymatic degradation
-uptake by cells
How are NTs removed by diffusion?
They are released into the synaptic cleft and then diffuses away.
How are NTs removed by enzyme degradation?
Broken down by enzymes.
How are NTs removed by uptake from cells?
Returned to neuron, transported to neighbouring cells.
What are graded potentials?
These are potentials that don’t reach the threshold.
How can graded potentials reach the threshold?
By having lots of graded potentials close together.
What are the different areas where info can enter the cell?
-axosomatic synapses
-axodendritic synapses
-axoaxonal synapses
What are the features of a graded potential?
-local event (passive)
-affects short distance
-variable amplitude
-repolarisation (decay over time)
-can summate
What are the features of an action potential?
-regenerative wave (active)
-affects over long distance possible
-all or nothing (set amplitude)
-repolarisation is dependent on ion channels
-cannot summate
What is functional syncytium?
This is where all cells in group behave in a certain way.
What are connexons?
Bridge between cells.
What is the purpose of connexons in cells?
Set of connexons make a physical pore between cells so ions can flow through them (cells with no delay).
What are the 4 main glial cells in the CNS?
-astrocytes
-microglial
-ependymal cells
-oliodendrocytes
What are the 2 main glial cells in the PNS?
-satellite cells
-schwann cells
What is the general role of glial cells?
-surround and support neurons
-electrical insulation
-supply nutrients
-maintain chemical environment
-destroy/ remove dead cells and pathogens.
