Nervous Cells and Junctions Flashcards
What are the 4 types of neurone?
- Unipolar —> 1 axonal projection
- Pseudounipolar —> 1 divides in 2
- Bipolar —> 2
- Multipolar —> many
What are the 3 types of multipolar neurones?
- Pyramidal cells
- Purkinje cells (tree) - GABA neurons in cerebellum
- Golgi cells (star) - GABA neurons in cerebellum
What 3 features do all nervous cells have?
- Soma = body
- nucleus, ribosomes, neurofilaments
- Axon = nerve fibre
- origin = axon hillock, branches = collaterals
- myelinated
- Dendrites = branches of body
- receive signals
- unmyelinated
What are the 3 components of the soma?
- Nucleus
- Ribosomes
- Neurofilaments
What are the 5 types of nervous cells and their functions/features?
- Neuron
- electrical transmission
- Oligodendricyte
- glial cells —> produce myelin
- Astrocyte
- most abundant cells in CNS
- connect to blood vessels
- Microglia
- nervous macrophages
- Ependyma
- epithelial cells lining ventricles
Which 4 ions are important in neurotransmission?
Na+, K+, Ca2+, Cl-
What are the extracellular vs intracellular concentrations of each 4 ions across an axon membrane?
- Na+: 140 vs 10 mM
- high outer
- K+: 4 vs 150
- high inner
- Cl-: 120 vs 5
- high outer
- Ca2+: 2 mM vs 0.1 µM
- gradient
What is the range for RMP?
-40 to -90 mV
How is an AP generated?
- VGSCs open —> Na+ influx —> depolarisation
- VGKCs open (slower) —> K+ efflux —> repolarisation
How is a RP restored?
Na+/K+ ATPase:
- Resting configuration
- Na+ enter —> phosphorylation (ATP) —> Na+ out
- Active configuration
- Na+ all out —> K+ enter
- Resting configuration
- K+ in
What type of conduction occurs across an axon and how?
Saltatory conduction (cable transmission)
- myelin —> nodes of ranvier —> AP jumps across gaps
What are the 4 steps of synaptic transmission?
- AP propagation
- VGSCs open —> Na+ influx —> depolarisation —>
AP along axon —> VGKCs open —> K+ efflux —>
repolarisation
- VGSCs open —> Na+ influx —> depolarisation —>
- NT release
- AP opens VGCCs at pre-synaptic terminal —> Ca2+
influx —> NT vesicle exocytosis
- AP opens VGCCs at pre-synaptic terminal —> Ca2+
- Post-s receptor activation
- NT bind to post-synaptic receptors
- NT reuptake
- NT dissociate from receptors —> metabolise by
enzymes in synapse or recycles by transporter
proteins
- NT dissociate from receptors —> metabolise by
Which 2 types of communication occur at a synapse?
Autocrine
Paracrine
What are the 3 types of synapses?
- Axodendritic
- Axosomatic
- Axoaxonic
What is a neuromuscular junction?
Junction between axon terminal and muscle membrane —> unidirectional chemical communication between nerve and muscle
Which type of communication occurs at a neuromuscular junction?
Paracrine
What is a miniature EPP?
EPP change by 1 ACh vesicle —> not enough to generate AP
How does a nervous impulse cause muscle contraction? (3)
- AP across axon —> Ca2+ enter pre-synaptic
terminal - ACh released into synapse
- ACh bind to nAChRs on skeletal muscle —> change
EPP (muscle cell depolarisation)
How does excitation-contraction coupling occur? (3)
- nAChR activated (excitation) —> depolarisation —>
AP in muscle cell - AP travel through T-tubules —> to sarcoplasmic
reticulum - Sarcoplasmic reticulum release Ca2+ —>
contraction
What is the location, function and effect of sarcoplasmic reticulum?
Location: surround myofibrils
Function: Ca2+ storage and release (depolarisation)
Effect: Ca2+ release —> myofibril and muscle
contraction
What are 3 examples of disorders of neuromuscular junctions?
- Botulism
- BTx (toxin) —> irreversible disruption to ACh
release from pre-synaptic nerve
- BTx (toxin) —> irreversible disruption to ACh
- MG (Myasthenia Gravis)
- autoimmune
- antibodies against AChRs —> fatigable weakness
- LEMS (Lambert-Eaton Myasthenic Syndrome)
- autoimmune
- antibodies against VGCCs
