Electrical properties Flashcards
Where is resistance located in the axon?
- In the fluid INSIDE the axon
2. Across the cell membrane
What effect will increasing diameter have on resistance?
Decrease resistance
How is resistance decreased across the cell membrane?
Ion channels (allow ions to move freely)
Ion channel specific to sensory neurons; Located on dendrites; Channels open or close in response to some sensory stimulus (temp, light, etc.); Cause local potentials
Modality-gated ion channels
Ion channels that open in response to neurotransmitter or drug binding; Located on post-synaptic terminal; Cause local potentials
Ligand-gated ion channels
Ion channels that open or close in response to changes in the membrane potential; Channels will only let specific ions pass; Located on axons and presynaptic terminals; Important for: action potentials and release of neurotransmitters from the presynaptic terminal
Voltage-gated ion channels
The inside of an axon is usually more [negative/positve] compared to the outside. Where are Na, K, Cl, and Ca most located?
Negative; K= inside; Na, Cl, Ca = outside
The equilibrium potential is [positive/negative] for Na. The equilibrium potential is [positive/negative] for K. The equilibrium potential is [positive/negative] for Cl.
Positive; Negative; Negative
When ion channels open in a resting neuron, which way does sodium move? Potassium? Chloride? Calcium
Na = moves into cell K = moves out of cell Cl = moves into cell Ca = moves into cell
Sodium-potassium ATPase pumps __ Na+ ions out and __ K+ ions in.
3; 2
Local potentials, or graded potentials, in sensory neurons are called _______ potentials. What type of ion channels are in sensory neurons?
Receptor potentials; Modality-gated
Local potentials, or graded potentials, in post-synaptic membranes are called _______ potentials. What type of ion channels are in post-synaptic membranes?
Synaptic; ligand-gated
______ refers to the inside of the cell becoming more positive where ______ refers to the inside of the cell becoming more negative
Depolarizing; hyperpolarizing
Sequential local potentials can add together on one neuron
Temporal summation
Different local potentials that occur at the same time can combine from more than one neuron; The effect can be additive or subtractive
Spatial summation
Large, brief depolarization that is repeatedly regenerated along the length of an axon; Actively propagated, so it travels long distances along the axon without a decrease
Action potentials
What does a strong stimuli increase in terms of APs?
- Increases the frequency of action potentials in one neuron
- Increases the number of neurons that are activated
Sodium ion channels quickly open due to ____ and close ____
Voltage; spontaneously
Potassium ion channels remain open as long as the membrane is _______ and close who the membrane is _______
Depolarized; hyperpolarized
No stimulus, no matter how strong, can produce a second action potential
Absolute refractory period
A larger than normal stimulus can produce a second action potential
Relative refractory period
What are the roles of a relative refractory period
- Allows APs to occur at greater frequency (do’t need to wait for another to occur)
- APs will only go in one direction
How can you in increase the speed of APs?
- Increase membrane resistance (myelination)
2. Decrease resistance inside the neuron (larger axon/dendrite spine diameter)
In terms of Na ion channel density, where are they most concentrated? where are they least concentrated?
Nodes of Ranvier; internode region
Increases the speed of AP dramatically
In myelinated axons, is the speed of the AP the same throughout the axon?
No, APs slow at the nodal regions where APs are regenerated
What will happen to the equilibrium potential for potassium in a hypokalemic patient?
increase (more negative)
What will happen to the membrane potential for potassium in a hypokalemic patient?
increase (more positive)
Will a neuron become more or less excitable in a patient with hyperkalemia?
more excitable
