Introduction to neurophysiology Flashcards
What are the 3 types of neurons?
Sensory neurons
Motor neurons
Interneurons
What are the 4 types of glial cells of the CNS?
Astrocytes
Ependymal cells
Oligodendrocytes
Microglia
What are the 2 types of glial cells of the PNS?
Schwann cells
Satellite cells
What is a key difference between glial cells and neurons in terms of electrical excitability?
Glial cells, unlike neurons, are not electrically excitable and do not fire action potentials
List 2 key functions of astrocytes.
Regulate extracellular potassium [K+] levels
Re-uptake of neurotransmitters e.g. glutamate
By which 2 main mechanisms do astrocytes regulate extracellular potassium levels?
Uptake and spatial buffering
Astrocytes regulate extracellular K+ levels via spatial buffering. What is this?
Astrocytes redistribute K+ via gap junctions to areas with lower K+ concentration
This prevents local K+ buildup and maintains neuronal excitability
Which cell is responsible for myelination in the CNS? …PNS?
CNS - Oligodendrocytes
PNS - Schwann cells
What is the function of the myelin sheath?
Insulates the axon to allow for rapid conduction of electrical signal along the axon
What kind of epithelium are ependymal cells?
Ciliated cuboidal
Ependymal cells line which 2 areas of the brain?
Ventricles and choroid plexus
What are the functions of ependymal cells in the ventricles and choroid plexus?
Ventricles - circulate CSF
Choroid plexus - CSF production
How and where is CSF produced?
Ependymal cells in the choroid plexus filter blood plasma to produce an ultrafiltrate
Where do microglia originate from, and how do they enter the brain during development?
Microglia originate from bone marrow-derived yolk sac progenitors
These progenitors cross the blood brain barrier early in development (before it is fully formed) and then populate the brain and spinal cord
Local interneurons are important for which processes?
Spinal reflexes
Which type of interneurons connect different brain regions?
Relay interneurons
Are interneurons mostly excitatory or inhibitory?
Inhibitory
What 4 ways can neurons be classified based on their morphology?
Unipolar
Bipolar
Multipolar
Pseudo-unipolar
What are the 4 common functional domains in typical neurons?
Dendrites
Soma (cell body)
Axon
Pre-synaptic terminals
Which specialised feature is seen on dendrites?
Dendritic spines
Where in the post-synaptic neuron is the action potential first generated?
Initial segment of the axon
By what process does an AP travel from the soma to the pre-synaptic terminal along the axon?
Fast axonal transport
Through which structures do substances travel during fast axonal transport?
Microtubules
Microtubules in axons are stabilised by what?
Tau proteins
The cytoskeleton in an axon contains which 3 key structures?
Microtubules
Microfilaments
Neurofilaments
Abnormalities in tau proteins are implicated in which disease?
Alzheimer’s disease
Which type of motor protein is involved in anterograde transport?
Kinesins
Which type of motor protein is involved in retrograde transport?
Dyneins
What is meant by the hyperpolarization phase of an AP and what causes it?
When the membrane potential overshoots the resting potential and becomes more negative than the resting potential
K+ channels are slow to close, allowing excess K+ to leave the cell
What are the 2 types of AP refractory periods?
Absolute refractory period
Relative refractory period
A new AP cannot be generated in the absolute refractory period due to what?
Na+ channel inactivation
Describe the generation of an AP during the relative refractory period.
A new AP is possible, but only with a stronger stimulus
Dendrites have slower electrical conduction than axons due to what?
Less VG Na+ channels
What is the conduction velocity of a myelinated neuron?
120 m/s
What is the conduction velocity of an unmyelinated neuron?
25 m/s
What is saltatory conduction?
The process by which an AP jumps from one node of Ranvier to the next, skipping over the myelinated sections of the axon
What are 3 things that influence conduction velocity in an axon?
- Density of voltage-gated Na+ channels
- Diameter of axon
- Myelination
In what way does axon diameter affect conduction velocity? Why is this?
The larger the axon diameter, the faster the conduction velocity
This is because large diameter reduces internal resistance, allowing ions to move more freely through the axon
In what ways does myelination affect membrane resistance and membrane capacitance?
Increases membrane resistance (prevents ion leak)
Reduces membrane capacitance (prevents charge loss to membrane)
