Cells Of The Nervous System And Neuromuscular Junction Flashcards
What is a unipolar neuron?
1 atonal projection
What is a pseudo-unipolar neuron?
Single atonal projection that divides into two
What is a bipolar neuron?
2 projections from cell body —> axon and dendrite
What is a multipolar neurone?
Numerous projections does cell body —> 1 axon and rest are dendrites
What are the key features of the soma?
Contains nucleus and ribosomes
Contains neurofilaments —> structure and support
Features of the axon?
Long process —> originates from soma at axon hillock
Can branch of into collaterals
Usually covered in myelin
Key features of dendrites?
Highly branched cell body
Not covered in myelin
Receives signal from other neurons
What are neurons?
Excitable cells of the CNS
Responsible for electrical transmission
What are oligodendrocytes?
Glial cell —> produces myelin
What is an astrocyte?
Most abundant cell type in CNS
What is a microglia?
Neuronal macrophages
What is an ependyma?
Epithelial cells lining the ventricles
In neuronal what is the charge like inside compared to outside?
Negative inside compared to outside
RMP between -40 - -90mV
What creates a potential difference across the membrane?
Difference in concentration
What happens in an AP?
- VGSC open —> Na+ influx —> further depolarisation
- VGKCs open at slower rate —> effluent of K+ from cell —> membrane repolarisation
How does the Na+K+ATPase pump restore the ion gradient?
- Resting config —> Na+ enters vestibule —> phosphorylation —> ions transported through protein
- Active config —> Na+ removed from cell —> K+ enters the vestibule
- Pump returns to resting config —> K+ transported back into the cell
What is saltatory conduction?
Myelin prevents AP spreading because it has high resistance and low capacitance
AP ‘jumps’ between nodes
What are nodes of ranveir?
Small gaps do myelin intermittently along axon
What happens at the synapse?
AP opens VGCCs at presymaptic terminal
Ca2+ influx —> vesicle exocytosis
NT binds to receptors on the post-synaptic membrane
Receptors modulate post-synaptic activity
NT dissociates from receptor
What happens to the NT once it dissociates from the receptor?
Metabolised by enzymes in the synaptic cleft
Recycled by transport proteins
What is an axodendritic synapse?
Connection between presynaptic terminal and neuronal dendrite
What is an axosomatic synapse?
Connection between presynaptic terminal and neuronal soma
What is an axoaxonic synapse?
Connection between presynaptic terminal and neuronal axon
What happens at a neuromuscular junction?
AP propagated along axon —> Ca+ entry at presynaptic terminal
ACh release into synapse
ACh binds to nicotinic ACh receptors on skeletal muscle —> chnage in end-plate potential
What is the sarcolemma?
Skeletal muscle membrane
What are T-tubules?
Continuous with sarcolemma and closely connected to sarcophagi control reticulum
AP travels through T-tubules
What is the location, function and effect of sarcophagi code reticulum?
Location —> surrounds myofibrils (contractile units of muscle)
Effect —> Ca2+ storage —> Ca2+ release following sarcolemma depolarisation
Effect —> Ca2+ —> myofibril contraction and muscle contraction
What is botulism?
Botulism toxin irreversibly disrupts stimulation-induced ACh release from presynaptic nerve terminal
What is Myasthenia Gravis (MG)?
Autoimmune disorder —> antibodies directed against ACh receptor
Cause fatigable weakness
What is Lambert-Eaton myasthenic syndrome (LEMS)?
Auto immune disorder —> antibodies directed against VGCC
