Cell Biology Flashcards
What equation is used to determine the equilibrium potential?
The Nernst equation
What is the RMP?
An electrical potential difference across the plasma membrane.
How is the RMP maintained?
The K+ leak channel
Na+ pump (Na+/K+ATPase)
What is a rapid change in RMP called?
An action potential
What causes an action potential (transient change in RMP)?
An influx of Na+ ions and an efflux of K+ ions through voltage dependent ion channels
What prevents action potentials from being sett off backwards?
The refractory period
What causes a refractory period?
The prolonged activation of K+ channels and inactivation of Na+ channels after an action potential has passed along the axon.
Explain the process of neurotransmission at the NMJ.
- The action potential invades the axon terminal.
- Depolarization of the axon terminal triggers the activation of voltage-gated Ca2+ channels.
- The influx of Ca2+ causes the release of a chemical signal (ach molecules).
- The ach molecules bind to the receptor (a Na+ channel) in the postsynaptic cell which causes an electrical signal.
- The EPP triggers an a.p. Via the v.g. Na+ channels located near the junction along folds.
What happens to the I band in skeletal muscle during contraction?
(Area of thick filaments alone)
Length decreases
In skeletal muscle, what happens to the z line during contraction?
The distance between z lines decrease.
Explain the composition of thick filaments in skeletal muscle.
Made up of myosin
Several 100s of myosin molecules make up each thick filament
The M line hold thick filaments together
Explain the composition of the thin filament in skeletal muscle
Comprised of actin, tropomyosin, and troponin
G-actin molecules form F-actin strands (g-actin molecules have myosin binding sites)
2 F-actin strands wind together in a double helix
Long filaments of tropomyosin wind around the double helix
What is the contractile unit of a microfibril called?
And what is it comprised of?
A sacromere
Made up of actin and myosin filaments
What initiates contraction in skeletal muscle?
An action potential triggers Ca+ release from the SR to the mycrofibril.
What does CNS and PNS stand for?
Central nervous system
Peripheral nervous system
