Chapter4 Flashcards
Membrane potential
Difference in electrical charge between the inside and the outside of the cell.
Microelectrodes
Extremely fine recording electrodes, which are used for intracellular recordings.
Resting potential
Resting state of a neuron, about -70mV. Neuron is said to be polarized.
Ions
Positively or negatively charged particles.
Ion channels
Specialized pores in the neural membranes that ions pass through. Each one is specialized for the passage of a specific particle.
Sodium-potassium pumps
Active transport mechanisms that pump Na+ ions out of neurons and K+ ions into the neurons.
Transporters
Mechanisms in the membrane of a cell that actively transport opens or molecules across the membrane.
Depolarize
Decreasing the resting membrane potential of the neuron…..membranes becomes more positive
Hyperpolarize
Increasing the resting membrane potential of the neuron.
Excitatory postsynaptic potentials (EPSPs)
Graded postsynaptic depolarizations, increase the likelihood of generating an action potential.
Inhibitory postsynaptic potentials (IPSPs)
Graded postsynaptic hyperpolarizations, decreases the likelihood of generating an action potential.
Graded responses
Amplitudes are proportional to the intensity of the signals that elicit them. Weak signals elicit small postsynaptic potentials, strong signals elicit large postsynaptic potentials.
Neurotransmitters
Chemicals released from neurons at terminal buttons and interact with specialized receptor molecules on the next neuron- first messengers.
Axon hillock
The conical structure at the junction between the cell body and the axon.
Axon initial segment
Where action potentials are generated, adjacent to the axon hillock.
Threshold of excitation
The level of depolarization necessary to elicit an action potential, usually about -65mV.
Action potential
Massive, momentary reversal of the membrane potential from about -70mV to +50mV.
All-or-none responses
Responses that are not graded, they either occur to their full extent or do not occur at all.
Integration
Adding or combining a number of individual signals into one overall signal.
Spatial summation
The integration of signals that occur at different sites on the neuron’s membrane.
Temporal summation
Postsynaptic potentials produced in rapid succession at the same synapse sum to form a greater signal.
Voltage-activated ion channels
Ion channels that open or close in response to the changes in the level of the membrane potential.
Absolute refractory period
Brief period of about 1 to 2 milliseconds after the initiation of an action potential during which it is impossible to elicit a second one.
Relative refractory period
Period during which it is possible to fire the neuron again but only by applying higher-than-normal levels of stimulation.