Week 2 neuro sl 1-55 Flashcards
How thick is the cell membrane?
2 molecules thick, 2 phospholipid molecules thick
What is simple diffusion?
Process that doesn’t consume energy
What are 4 types of simple diffusion?
1) small uncharged molecules that are relatively lipid souble can diffuse through lipid bilayer (ex. steroid hormone)
2) Small uncharged molecules (ions) can diffuse through water-filled pores
3) Ion channels, some are leaky and ions flow in or out as needed
4) Some ion channels are voltage gated, and they open or close in response to changes in electrical voltage
What is active transport for? Give some examples.
-To move substances in and out of cells against gradients, uses metabolic energy, usually ATP
-ex. Endocytosis, exocytosis, phagocytosis
What can integral membrane proteins act as regarding the cell membrane?
Act as transporters
Why are ion channels important in nervous system?
Because they help produce electrical impulses that transmit information rapidly
What is resting membrane potential?
Cells in the body have a potential difference or voltage across membrane
Which is more negatively charged? the inside or outside of the cell
The inside is more negatively charged
What is the charge in neurons?
It’s -70mV
Why are voltage gated ion channels important for electrical activity in axons?
Because when the channels open, they can change the membrane potential of the cell, which is needed to conduct an electrical signal in neurons
What are action potentials?
Signals that go along nerves, taking signal from one place to another
What do neurons recieve send and pass signals on as?
As action potentials
What causes action potentials?
Brief discharges (depolarizations) of resting membrane potential, caused by a rapid influx of Na+ through the opening of sodium channels
Where do action potentials move once initiated?
Once initiated, they move along axon membrane toward the synapse
How do signals travel so far?
Signals must go a long way without weakening, so signals are continously reamplified, using voltage-gated ion channels
What is depolarization?
Neuron cell initially -70mV. Stimulation causes positive charges to flow into the cell, and the cell becomes more positive than resting potential.
What happens regarding Na+ membrane permeability in channels during action potentials.
Explosive increase in Na+ permeability results in depolarization -70mV to +30mV. Then, Na+ channels close and theres a rapid decrease in Na+ permeability.
The cell must then repolarize to compensate. K+ is positively charged so it will diffuse out of the cell, making the inside of the cell more negative again, back to original resting membrane potential
What doe Na+ and K+ pumps do and where?
They work constantly in the plasma membrane, they pump out Na+ that entered the axon during action potentials, and pump in K+ that left.
What happens in non myelinated axons action potentials?
Action potential passes smoothly along axon and all parts of membrane are depolarized
What happens in myelinated axons action potentials?
Action potential jumps between non-insulated nodes of ranvier, by saltatory conduction, enabling faster transmission and requiring less energy to restore the membrane
What does refractory period in axons do?
Ensures the action potential only goes in one direction, down the axon to its end
What do action potentials do once they reach the end of the axon?
They stimulate the next cell
What happens in pre-synaptic nerve endings?
Presynaptic nerve endings release neurotransmitters that stimulate action potentials in the postsynaptic cell
What does the presynaptic neuron end in?
A terminal bouton
What separates presynaptic neuron from postsynaptic neuron?
synaptic cleft
What is the process of what happens in the presynaptic neuron?
1) Action potentials reach axon terminals
2) Voltage-gated Ca2+ channels open
3) Ca2+ binds to sensor protein in cytoplasm
4) Ca2+ protein complex stimulates fusion and exocytosis of neurotransmitter
What occurs on the postsynaptic neuron side?
-Neurotransmitter binds to it’s receptor on the dendrite, causing ion channels on post synaptic dendrite membrane to open. These gates are chemically regulated.
-Cells are stimulated to produce action potentials
What process occurs in the postsynaptic neuron?
1)Chemically (ligand) gated channels open.
2)Na⁺ diffuses inward, causing depolarization (EPSP).
3)EPSP spreads locally and decreases over distance.
4)Voltage-gated Na⁺ and K⁺ channels open.
5)Action potential is conducted.
How can we record membrane potential?
Patch clamp technique using microelectrode, records voltage for a certain area of the cell membrane over time
What are neuromuscular disorders and how can they be caused?
-delayed relaxation of skeletal muscle after voluntary contraction or electrical stimulation
-Can be caused by mutations in muscle Cl- channel
-1) channel gates do not open properly
-2) repolarization delayed, several action potentials fire instead of just one
