Lecture 3:Graded potential, Action potentials and synapses

Question 1

What does the video mention red in class about resting memebrane potential animation include?

Answer 1

there are more potassium channels than sodium ions. It depends on diff permeability like leak channel. The charges create voltage and the difference= membrane potential depend on the presence of soium radiant canal K+

Question 2

What does the second video about rsting memebrane potential include of?

Answer 2

sodium ability to change memebrane potential ion behave independantly than other ion gated open

Question 3

what are the type of gated ion channel

Answer 3

chemical gted chanels (opens only with binding of a specific chemical like a nerotransmitters
Voltage-gated channels( open and close in resposnse to change in memebrane potentials
Mechanically gated channels( open and close in response to physical deformation of the membrane as in sensory receptors
depolarization is toward zero while hyperpolarization is further away than zero more negtive inside

Question 4

changes in memebrane potential

Answer 4

ion concentration change and a permeability to ions changes

Question 5

Describe graded potentials

Answer 5

Short lived, local
Stronger stimulus increase magnitude
when there is a weak stimulus small chanel open the rsult is a small change
they are short distance signals where receptor potential: receptor of sensory neurons and postsynaptic potential= dendrites or soma of neuron or muscle cell

Question 6

action potential

Answer 6

They do not decay with distance for example the dinosaure they are regenrative because it doesnt decay they can have all similar action potential along the dinosaure. They travel long distance without change in axon and only occur in muscle cell and axons of neurons (excitable cells). It involves opening of specific voltage gated channels.

Question 7

Voltage-gated channels

Answer 7

voltage gated Na+ and K+ channels give neuron ability to generate and propagate action potentials. AP are very rapid. There is a 200-300 frequency. most sodium channels are in the close state when they sense a change it change the membrane it becomes more depolarize it open chanel in a brief period of time so quickly

Question 8

Describe the phase of the action potential and the changes in ion permeability that accompany each phase

Answer 8

1- Steady resting memebrane potential is ner Ek, Pk, PNa due to leak K+ channels
2- local membrne is brought to threshold voltage by a depolarizing stimulus
3- current through opening voltage-gated Na+ channels rapidly depolarize the membrne causong more Na+ channels to open
4- Innactivation of Na+ channels and delaying opening of voltage gated K+ channels halts memebrane depolarization
5- outward current through open voltage gated k+ channels repolarize the membrane back to negative potential
6- persitente current through slowly closing voltage gated K+ channels hyperpolarizes memebrane toward Ek: Na+ channels retourn from inactive state to closed state
7- closure of voltage gated K+ chanels return the membrane potential to its resting value

Question 9

absolute refractory period

Answer 9

sodium active no other activation when closed other action potential

Question 10

relative refractory period

Answer 10

depolarization reverse to positive value increase permeability potassium hyperpolarize -80

Question 11

action potential thresholds

Answer 11

it indicates wheter or not incoming stimuli are sufficient to generate an action potential. According to numerous factors the value can vary

Question 12

Describe the mechanism of action potentials propagation

Answer 12

Current entering during an AP is sufficient to easily depolarize adjacent membrane to the threshold potential. The propagation of AP from initail segment to the axon terminal is typically one way because the absolute refractory period follows along in the wake of the moving AP

Question 13

Compare the various ways that action potenital can be initiated

Answer 13

Action potentials are initiated by membrane depolarization which causes the opening of voltage-gated ion channels, which causes an influx of sodium into the cell. For nerve and muscle cells, sodium channels are opened, which produces the rapid upstroke of the action potential.

Question 14

Compare and contrast graded potential and action potentials

Answer 14

Graded potential= amplitude varies with size of the initiate event. It can be summed. Has no threshold. Has no refractory period. Is conducted decrementally the amplitude decrease with distance. Duration varies with initiating conditions. Can be a depolarize or hyperpolarize. Initiate by receptor, neurotransmitter or sponstanely. depends on ligand gated chanels or other chemical or physical changes
Action potentials= All or none the amplitude is independent of the size. cannot be summend. threshold of 15mV . has a refractory period. depolarization is amplified to a constant value. duration is constant for a given cell type under constant conditions. is only a depolarization. inititate by graded potential. depend on voltage gated channels

Question 15

Breifly describe the functional anatomy of synapses and the mechanism of neurotransmitter release

Answer 15

The synapse is the point of communication between two neurons(or neuron and muscle), the chemical synapses is neurotransmitters relay info from pre to postsynaptic cell across synaptic cleft and electrical synapses are pre and post synaptic cellsjoinded by a gap junctions. For the mechanism neurotrasmitter are stored in vesicles there the vesical docked on PM at release regions as active zones . The transmitter release inititatewhen AP reaches synaptic bouton. This is when the AP depolorizes the membrane bouton causin voltage gated Ca2+ to open that activate vesicle docking and fusion with the PM.