Neuro pt2 Flashcards
What is the resting membrane potential of a neuron?
The resting membrane potential is typically around -70 mV.
What is the role of the Na+-K+ ATPase pump?
[Na+]out > [Na+]in and [K+]out < [K+]in, maintaining the polarized state of the neuron.
What happens to K+ ions at rest?
K+ leaks out of the cell.
What is the state of Na+ channels at rest?
Na+ channels are closed at rest.
What is the chloride ion concentration gradient?
[Cl-]out > [Cl-]in, but the negative charge inside the cell balances the influx.
Define depolarization.
Inside of the cell becomes less negative; the resting potential approaches zero or becomes positive (e.g. Na+ moves into the cell).
What is hyperpolarization?
Inside of the cell becomes even more negative; the resting membrane potential gets larger.
What are graded potentials?
Short-term, localized depolarization or hyperpolarization that depends on the intensity of the stimulus. The larger the stimulus, the greater the change in voltage.
What is an action potential?
An all-or-none, uni-directional wave of depolarization along the length of a cell.
What triggers the opening of Na+ channels during action potential?
Depolarization at the axon hillock to a threshold level (-50 mV).
What is the Hodgkin Cycle?
A positive feedback loop where the opening of Na+ channels causes further depolarization.
What occurs immediately after Na+ channels close?
The resting potential can be regenerated.
What is the role of K+ channels during repolarization?
K+ channels open, allowing K+ to rush out of the cell, restoring the resting membrane potential.
Define threshold in the context of action potential.
The level of depolarization that will trigger an action potential.
How is stimulus intensity coded by action potential?
By the frequency of action potentials; more intense stimuli lead to higher frequencies.
What is the absolute refractory period?
A period when it is impossible to generate another action potential while Na+ channels are open.
What is the relative refractory period?
A period when action potentials can occur, but the stimulus must be greater than before.
What factors influence the speed of action potential?
Axon diameter and the presence of myelin sheath.
What are Group A fibers?
Large diameter/thick myelin fibers associated with sensory and motor functions.
What is a synapse?
The junction of a neuron that allows transfer of message to a postsynaptic cell.
What is an electrical synapse?
Cells that are electrically coupled, allowing direct passage of ions.
What is a chemical synapse?
A synapse that relies on neurotransmitter passage across the synaptic cleft.
What happens during depolarization of the presynaptic axon terminal?
The influx of Na+ ions causes it to become depolarized.
What triggers neurotransmitter release?
Increased Ca++ in the axon terminal causes synaptic vesicles to fuse with the plasma membrane.
What are excitatory postsynaptic potentials (EPSPs)?
Depolarizations that lead to an increased likelihood of generating an action potential.
What are inhibitory postsynaptic potentials (IPSPs)?
Hyperpolarizations that lead to a decreased likelihood of generating an action potential.
How are neurotransmitter effects terminated?
By degradation, reabsorption, or diffusion away from the synapse.
What are the general characteristics of neurotransmitters?
Most neurons release one neurotransmitter, more than 100 are known, may be synthezised in axon terminal or in cell body.
What is acetylcholine (ACh)?
A neurotransmitter involved in skeletal muscle and various parts of the CNS.
What are biogenic amines?
Neurotransmitters like dopamine, norepinephrine, and epinephrine derived from tyrosine.
What are amino acids in neurotransmission?
Examples include glycine, glutamate, and GABA.
What are neuropeptides?
Neurotransmitters like enkephalins and endorphins, often associated with pain regulation.
What determines if a neurotransmitter is inhibitory or excitatory?
The type of channel it opens; generally, glycine and GABA are inhibitory, while glutamate is excitatory.
What are ionotropic actions?
Actions that open Na+ or Cl- channels.
What are metabotropic actions?
Actions that promote longer-lasting changes using a second messenger system.
what are receptor potential
potential generated by a stimulus in a receptor cell
what are post synaptic potentials
potential generated by neurotransmitters on the postsynaptic cell
