role of Ca2+ in the nervous system Flashcards
What role does soluble Ca2+ play in the nervous system?
Acts as a charge carrier and signaling molecule
Examples include cardiac action potentials and cellular metabolism.
What is the concentration of free calcium in most intracellular environments?
Very low
Most intracellular Ca2+ is buffered.
In what form is Ca2+ a major structural constituent of bones and teeth?
Insoluble form
What is the electrochemical equilibrium in the context of the Nernst equation?
No net movement of ions across the membrane
What happens to the membrane potential if it is only selective for K+?
It would be at EK
How does Ca2+ facilitate neurotransmitter release at the NMJ?
By triggering neurotransmitter release from the presynaptic cell
What effect does low extracellular Ca2+ concentration have on EPP generation?
Reduces likelihood of EPP generation
What role does Ca2+ serve during neurotransmitter release?
Second messenger
What happens to Na+ and K+ channels during presynaptic Ca2+ entry?
They become inactivated
What is observed in Cell 1 during moderate depolarization?
Presynaptic Ca2+ current followed by inward postsynaptic current
What occurs in Cell 2 during strong depolarization?
Doesn’t trigger presynaptic Ca2+ & no postsynaptic current
What is synaptotagmin’s role in neurotransmitter release?
Ca2+ sensor for synaptic vesicle fusion
List the three models of presynaptic neurotransmitter release.
- Synchronous: within several ms after an AP terminus
- Asynchronous: up to several seconds
- Spontaneous: in the absence of depolarization
What happens when Syt1 is removed?
Abolishes synchronous but not asynchronous release
What behavioral abnormalities are associated with synaptotagmin-7 deficiency in mice?
Bipolar-like behavioral abnormalities
What pathologies are associated with impaired presynaptic vesicle exocytosis?
- LEMS (lambert-Eaton MS)
- Cognitive dysfunction/ageing
- Increased presynaptic Ca2+ in the ageing brain
- Toxins like latrotoxin, tetanus, and botulinum toxins
What mediates muscle contractions in skeletal muscle?
Interactions between myosin and actin
What is required for myosin-actin interactions?
Ca2+
Where is Ca2+ released from during muscle contraction?
Sarcoplasmic reticulum
What model describes muscle contraction involving Ca2+?
Sliding filament model
What characterizes cardiac muscle potentials?
Longer & sustained repolarization plateau
What produces the plateau in cardiac muscle potentials?
Ca2+ entry through voltage-gated calcium channels
In cardiac muscle, where does a larger amount of Ca2+ initiated contraction come from?
Outside the cell
What are calcium transients?
Local, short-lived, spontaneous intracellular Ca2+ spikes
What do calcium transients regulate in neuronal development?
- NT phenotype
- Dendritic morphology
- Axonal growth and guidance
What influences the timing and frequency of calcium transients?
Location and identity of Ca2+ channels & receptors
What do calcium transients activate that transduces ionic signals into biochemical ones?
Enzymes
What is the relationship between the incidence of Ca2+ transients and rates of axon outgrowth?
Inversely related
