Nerve impulses and synaptic transmission Flashcards
What are the 3 overlapping functions of the nervous system? Explain them.
- Sensory input. The nervous system uses its millions of sensory receptors to monitor changes occurring both inside and outside the body.
- Integration. The nervous system processes and interprets sensory input and decides what should be done at each moment
- Motor output. The nervous system activates effector organs—the muscles and glands—to cause a response, called motor output.
What are the different types of membrane channels?
- Leakage or nongated channels: are always open.
- Gated channels: changes shape to open and close the channel in response to specific signals
What are the 3 main types of gated channels? Explain them.
- Chemically gated channels; also known as ligand-gated channels, open when the appropriate chemical (in this case a neurotransmitter) binds
- Voltage-gated channels; open and close in response to changes in the membrane potential
- Mechanically gated channels; open in response to physical deformation of the receptor (as in sensory receptors for touch and pressure).
Generating a resting membrane potential depends on what?
(1) differences in K+ and Na+ concentrations inside and outside cells
(2) differences in permeability of the plasma membrane to these ions.
When do membrane potential changes occur?
- Concentrations of ions across membrane change
- Membrane permeability to ions changes
The terms depolarization and hyperpolarization describe changes in membrane potential relative … ?
to resting membrane potential
What are the two types of signals that changes in membrane potential can produce?
- Graded potentials—usually incoming signals operating over short distances that have variable (graded) strength
- Action potentials—long-distance signals of axons that always have the same strength
What is depolarization?
- A decrease in membrane potential
- The inside of the membrane becomes less negative (moves closer to zero) than the resting potential
What is hyperpolarization?
- an increase in membrane potential
- The inside of the membrane becomes more negative than the resting potential.
What is the membrane potential at rest within a neuron?
-70mV
If the membrane potential goes from -70mV to -95mV, is the neuron depolarized or hyperpolarized?
hyperpolarized since it became more negative
If the membrane potential goes from -70mV to 60mV, is the neuron depolarized or hyperpolarized?
depolarized because it became less negative
Why are graded potentials called “graded” ?
- Because their magnitude varies directly with stimulus strength.
- The stronger the stimulus, the more the voltage changes and the farther the current flows.
How are graded potentials triggered?
- by some change (a stimulus) in the neuron’s environment that opens gated ion channels.
T or F. A graded potential can only be depolarized but not hyperpolarized.
False. They can be either depolarized or hyperpolarized
Between graded potentials and action potentials, which is “brief, long-distance signals within a neuron” and which is “short-lived, localized changes in membrane potential”
Action potential - brief, long- distance signals within a neuron
Graded potential - short-lived, localized changes in membrane potential
Does strength decrease with distance during an action potential?
No, Strength does not decrease with distance because it is constantly being regenerated
What is the location of event of graded potentials?
Cell body and dendrites
What is the location of event of action potentials?
Axon
How does the central nervous system differ between weak and strong impulses?
by the frequency of impulses
*high frequency = stronger stimulus
Rate of Action Potential propagation (spread) depends on what two factors?
- Axon diameter - Larger-diameter fibers have less resistance to local current flow, so have faster impulse conduction
- Degree of myelination - Two types of conduction depending on presence or absence of myelin
What is the difference between continuous conduction and saltatory conduction?
- Continuous conduction: slow conduction that occurs in nonmyelinated axons
- Saltatory conduction: occurs only in myelinated axons and is about 30 times faster