Cells of nervous system and neuromuscular junction Flashcards
4 types of neurones
Unipolar, pseudounipolar, bipolar and multipolar.
Examples of multipolar neurones?
Pyramidal cell, purkinje cell and golgi cell.
Where are purkinje and golgi cells found?
Cerebellum.
What neurotransmitter do purkinje and golgi cells release?
GABA
What part of the neurone can be covered with myelin?
Axon.
Function of dendrites?
Receive signals from other neurones.
Oligodendrocyte function?
Myelinate neurones.
Most abundant cell type in CNS?
Astrocyte.
Astrocyte function?
Homeostasis of neuronal external environment.
What are microglia?
Neuronal macrophages.
What are ependyma?
CNS epithelial cells.
What are the ion concentrations under resting potential?
High potassium inside, high sodium outside.
What causes membrane depolarisation to happen?
Opening of voltage gated sodium ion channels. This results in NA+ influx. This leads to further depolarisation.
What causes membrane repolarisation.
Opening of voltage gated potassium ion channels. Efflux of K+ (potassium ions move out).
Membrane potential reseting potential difference?
-70mV.
What restores the membrane potential?
Na+K- ATPase restores the ion gradients.
What are the small gaps in myelin called?
Nodes of ranvier.
How does myelin prevent action potential from spreading?
High resistance and low capacitance.
What is saltatory conduction?
Action potential jumps between nodes.
Na+ K+ ion ratio for Na+K+ ATPase?
3 sodium ions out and 2 potassium ions in.
How does Na+K+ATPase work?
Three sodium ions and ATP bind to pump. Upon phosphorylation of pump sodium ions are transported through protein. Two potassium ions bind to pump, release of phosphate reverts channel to original form and potassium is released on the inside on the membrane.
What happens when an action potential reaches presynaptic terminal?
Voltage gated Ca2+ ion channels open. Ca2+ influx leads to vesicle exocytosis.
How does neurotransmitter re uptake take place?
Metabolised by enzymes in synaptic cleft. Recycled by transporter proteins.
Neurotransmitter release is an example of what type of communication?
Paracrine. Can also act on same neurone in this case would be autocrine.
Synapses are organised into 4 types. What are the 4 types?
Axodendritic, axosomatic, axoaxonic and dendrodentritic.
What receptor do acetylcholine bind to on skeletal muscle?
Nicotinic acetylcholine receptors.
What occurs when acetylcholine binds to receptors on skeletal muscle?
Change in end plate potential.
What is the release mechanism of neurotransmitter called?
Quantal release.
How does muscle contraction happen?
Action potential travels along t tubule. Calcium ions are released from sarcoplasmic reticulum. Muscle contraction.
How does botulism disrupt neuromuscular junction?
Stops release of acetylcholine from presynaptic terminal.
How does myasthenia gravis disrupt neuromuscular junction?
Antibodies disrupt acetyl choline receptor on post synaptic terminal.
How does lambert eaton myasthenic syndrome disrupt neuromuscular junction?
Antibodies directed at voltage gated calcium ion channels.
