LESSON 4 Flashcards
- for short distance communication
graded potentials
- for long distance communication
action potentials
4 types of ion channels
leakage channels
voltage-gated channels
ligand-gated channels
mechanically-gated channels
- protein channels present in the plasma membrane of neurons and muscle fibers which open and close to allow certain ions to move across the plasma membrane
ion channels
- Their gates randomly alternate between open and closed spots
leakage channel
- They open in reaction to a change in membrane potential (voltage)
voltage-gated channel
- These channels open and close in response to a specific chemical stimulus/binding of a ligand or chemical stimulus
ligand-gated channel
- Open and close in reaction to mechanical stimulation specifically vibration (sound waves), pressure (touch) or tissue stretching
- The force alters the channels from their resting position, thus opening the gates
mechanically-gated channel
- voltage difference between the inside and
outside of a cell membrane when the cell is not responding to a stimulus
resting membrane potential
in many neurons and muscle fibers, it is __ to __ mV
-70 to -90 mV
- series of rapidly occurring events that
decrease and reverse the membrane potential and then eventually restore it to the resting state
action potential/nerve impulse
2 main phases of action potential:
- depolarizing phase
- repolarizing phase
- the voltage-gated channels open and
an action potential of the same amplitude occurs when depolarization reaches a threshold point
all-or-none principle
threshold point in many neurons
-55 mV
- a weak depolarization that cannot bring the membrane potential to threshold
subthreshold
- a stimulus that is just strong enough to depolarize the membrane to threshold
threshold
- a stimulus that is strong enough to depolarize the
membrane above threshold
suprathreshold
a reduction of voltage across a plasma membrane
(the interior surface of the plasma membrane becomes less negative/more positive than the outside) as a result of the opening of the voltage-gated sodium channels, allowing the inward flow of sodium ions
depolarization
- restoration of a resting membrane potential after
depolarization
repolarization
- Action potentials are self-propagated, and once started the action potential progresses along the axon membrane
propagation/conduction of nerve impulses
the membrane is ____ behind the leading edge of a nerve impulse
- refractory
- happens in unmyelinated axons
- Ions flow through their voltage-gated
channels in each adjacent segment of
the membrane
continuous conduction
- happens along myelinated axons
- Ions flow through their voltage-gated
channels from one node to the next
node of Ranvier
saltatory conduction
- Impulse traverse the entire length of
an axon - Nerve impulse propagates only at a
relatively SHORT distance
continuous conduction
- Impulse leaps/jumps from one node
to the next - Nerve impulse propagates MORE
RAPIDLY / towards a FARTHER
distance
saltatory conduction
- slower, uses more energy, less efficient
- uses higher number of ion channel
continuous conduction
- faster, uses minimum voltage channel
- prevent delay of nerve impulse
- more efficient
- uses less energy
saltatory conduction
what do you call the interval of complete unresponsiveness
absolute refractory period
- a second action potential cannot be initiated, even with a very strong stimulus
absolute refractory period
- period where stronger than minimum effective stimulus will lead
to the transmission of a nerve impulse called
relative refractory period
The change allows the influx of Na+ ions into the cell
leading to
depolarization
Resting state is restored by the outflow of K+ ions out of the cell leading to what you call
repolarization
At a _______, a presynaptic neuron converts an ______ into a ________. The postsynaptic neuron
then converts the chemical signal back into an ______
chemical synapse
electrical signal (nerve
impulse)
chemical signal (neurotransmitter release)
electrical signal (postsynaptic
potential)
- Nerve impulse propagation in which the impulse “leaps” from one node of Ranvier to
the next along a myelinated axon is
saltatory conduction
Axons with larger diameters conduct impulses at ______
higher speeds
