Physiology Lecture 3 Flashcards
4 stages of neuron signaling
- Resting State
- Depolarizing phase
- Repolarizing phase
- Undershoot
CNS is composed of what?
Brain and spinal cord
PNS (peripheral nervous system) is composed of what?
Somatic Division and Autonomic Division
List the components of a typical neuron
- Dendrite
- Cell body (contains nucleus)
- Axon
- Myelin sheath
- Node of Ranvier
- Schwann cell
- Axon terminal
Difference between presynaptic and postsynaptic?
Presynaptic is a nerve cell that releases a neurotransmitter into a synapse.
Postsynaptic recieves the neurotransmitter.
What is the resting membrane potential on average?
-70mV
What contributes to the RMP
both concentration and electrical gradient
Which ion plays the biggest role in generating the RMP?
K+
The magnitude of the resting membrane potential depends mainly on two factors:
- Differences in ion concentrations in the intracellular and extracellular fluids
- Differences in membrane permeability to the different ions, which reflects the number of open/closed channels for the different ions in the plasma membrane
A ________ is established when inward K+ movement = outward K+ movement i.e. net flux = 0?
K+ equilibrium potential
T or F. K+ equilibrium does not result in electrical neutrality!!
T
K+ equilibrium potential is at approx. -90mV
Does each ion have its own equilibrium potential?
Yes
Why are cell membrane potentials never 0?
- The number of electrical charges between compartments of charges
- Concentration gradients of the ions
- Presence of ion channels and “leaky” membranes
What is the equation used to find membrane potential?
Goldman-Hodgkin-Katz Equation
A change in the _______ of the membrane to any ion will change the ______________.
permeability, resting membrane potential
A change in the __________ of any ion inside or outside the cell will change the ______________.
concentration, resting membrane potential
Changes in membrane potentials creates _________, which in return causes the membrane to transmit information suggesting a point of _____________.
excitability, biological regulation
APs are considered
brief and reversible
What is membrane conductance?
If the conductance of the membrane to a particular ion is low, then the resistance to movement of that ion across the membrane is high.
5 Stages of AP explained
RMP- at rest
Threshold level- when threshold level is reached, an AP is fired
Depolarization- opening of voltage gated NA+ channels, Na+ influx (enters cell)
-Equilibrium potential is reached
Repolarization- closure of Na+ and opening of K+ channels,K+ efflux (leaves cell)
Hyperpolarization- not all channels close in time causing this. K+ channels then close
Depolarization is an example of what?
Positive feedback loop
Hyperpolarization is an example of what?
Negative feedback loop
An AP ________ require the migration of large numbers of ions
Does not
Does depolarization reach threshold every time?
No
All-or-none response
What does lidocaine do and how does it do it?
Lidocaine binds to voltage-gated sodium channels in a 1: 1 fashion and prevents the flow of sodium ions through the channel pore.
What is a absolute refractory period?
A portion of the AP where a second stimulus will not initiate a 2nd AP.
What is a relative refractory period?
The instance after a absolute refractory period where a stimulus can generate an AP, but the magnitude of the APs during this period are lower.
When do refractory periods occur?
Occurs as the voltage-gated sodium channels are closing.
T or F. Absolute refractory period is shorter in cardiac muscle and nerves, and longer in skeletal muscle.
False, absolute refractory period is shorter in skeletal muscle and longer in cardiac muscle and nerves.
What is the domino effect of an AP?
An AP can travel the length of an axon because each point along the membrane is depolarized to a level that exceeds (more positive) threshold potential
Depolarization occurs at Node of Ranvier
Propagation of an AP is primarily ________.
What is an exception?
unidirectional, either goes from brain to muscle or periphery to brain
Funny bone is bidirectional
In regards to AP velocity, The ______ the fiber diameter, the ______ the action
larger, faster
The strength of the AP does what over distance
decreases
Myelin sheath purpose?
The main functions include protecting the nerves from other electrical impulses, and speeding the time it takes for a nerve to traverse an axon.
Node of Ranvier purpose?
AP depolarizes at node of ranvier to speed up nerve impulse (allows node to recharge)
T or F. A node is the only place where a full AP occurs.
True
What generates an AP?
Pain can generate an AP.
Structure that’s responsive to some kind of sensory information.
Synaptic input (Nerve to nerve interaction)
Graded potentials can either cause _______ or __________.
depolarization or hyperpolarization
Can single graded potentials initiate an AP?
No, results from a summative event
Either a large number of low voltage graded potentials or a smaller number of higher voltage graded potentials.
Both reduce the membrane potential(making it more positive) to the threshold potential
Receptor potentials can be both _________ or __________.
Stimulatory or inhibitory
What is a pacemaker potential?
A slow, positive increase in voltage across the cell’s membrane that occurs between the end of one action potential and the beginning of the next action potential.
Example is the SA node of the heart
What happens at the axon terminals?
Release of neurotransmitters into synaptic cleft between the dendrites of the next neuron.
Synapse
