Experiment 2
Which of the following statements is true?
A greater than threshold stimulus in a single neuron causes the same depolarization as a threshold stimulus.
_____ is the term used to describe the time following depolarization to denote non-responsiveness, and _____ describes the period of less than normal responsiveness observed prior to complete repolarization.
Absolute refractory period; relative refractory period
The electrical gradient for ______ is from the inside of the cell to the outside.
Cl-, Anions
Procaine
Decreases conduction velocity, Decreases amplitude of compound nerve action potentials, Dissolves in the lipid rich neuronal membrane, Prevents Na+ voltage gated channels from opening when a neuron is stimulated
conduction velocity
rate at which an action potential travels along the axon of a neuron (mm/msec)
This is an example of ______.
recruitment
Resting Membrane Potential:
refers to a separation of charged particles across the resting cell membrane, refers to more negative charges on the inside of the membrane with respect to the outside, is measured in millivolts.
repolarization
return of the membrane potential to resting state (negative on the inside with respect to the outside)
Which of the following cell types can conduct action potentials? a. smooth muscle cells b. cardiac muscle cells c. neurons d. skin epithelial cells e. skeletal muscle cells
smooth muscle cells, cardiac muscle cells, neurons, skeletal muscle cells
stimulus
some change that makes the membrane potential less negative
polarization
state of plasma membrane in which there is a separation of charge across the membrane with the inside of the membrane being negative with respect to the outside
maximal
stimulus that is large enough to recruit (stimulate to threshold) all of the neurons in a compound nerve
subthreshold
stimulus with a voltage less than needed to produce a response in an excitable tissue
supra-maximal
stimulus with greater voltage than the maximal stimulus
What is the correct sequence of events leading to an action potential?
stimulus; depolarization; repolarization; Na+-K+ pump activity
The phenomenon observed in the previous question is an example of ______.
the All or none law
A stimulator is used to apply a stimulus to a single neuron. The threshold stimulus is determined to be 2.5 volts. If a stimulus of 5 volts is applied, the resulting action potential will be _______ the action potential observed on the same neuron given a stimulus of 2.5 volts.
the same as
threshold
weakest stimulus capable of producing a response in an excitable tissue, sufficient to open Na+ voltage gated channels
Which of the following statements are true concerning the Na+/K+ pump. Select all correct answers.
It actively transports sodium out of the cell, It actively accumulates potassium in the cell, Three Na+ and two K+ ions are moved across the membrane with every cycle, It is an active transport system that requires ATP to function, It helps create the resting membrane potential by transporting three positive ions out of the cell and only two positive ions back in with every cycle causing a net decrease in membrane potential.
The concentration gradient for ______ is from the inside of the cell to the outside.
K+, Anions
The resting cell membrane is permeable to:
K+, Cl-
Which ions are found in a greater concentration in the intracellular fluid than in the extracellular fluid?
K+, anions (A-)
During membrane repolarization, ______ move out of the cell through _______ channels.
K+; voltage gated channels
The resting cell membrane is impermeable to:
Na+, Anions
The concentration gradient for ______ is from the outside of the cell toward the inside.
Na+, Cl-
Which ions are found in a greater concentration in the extracellular fluid than in the cytoplasm?
Na+, Cl-
The electrical gradient for ______ is from the outside of the cell to the inside.
Na+, K+
During membrane depolarization, _________ move into the cell through _______ channels.
Na+; voltage gated channels
How is the resting membrane potential of -70 mV (millivolts) best interpreted?
The inside of the fiber is 70 mV more negative than the outside.
A compound nerve action potential is the result of:
The sum of electrical activity from all the neurons making up the nerve
Which of the following will elicit an action potential in a single neuron?
Threshold stimulus, Supra-threshold stimulus
A nerve composed of several neurons, each having different properties with respect to irritability and conduction velocity, is:
a compound nerve
hyperpolarization
a state where the membrane is more polarized than in the resting state (more negative on the inside with respect to the outside)
excitability
ability to generate an action potential
conductivity
ability to propagate an action potential
depolarization
change in the membrane potential from more negative to less negative (graded potential) or from negative to positive (action potential)
All cells
develop resting membrane potentials
What are four factors that can influence conduction velocity?
diameter, temperature, myelin sheath, pharmacologic agents
The most excitable neurons of a compound nerve reach threshold when given a 3 volt stimulus. A stimulus of 4 volts then, results in a compound nerve action potential _____ the one observed in the same nerve with a stimulus of 3 volts. Correct!
greater than
action potential
large transient depolarization event including a polarity reversal that is conducted along the membrane of a muscle fiber or neuron
K+ and Cl-pass freely through the resting cell membrane through:
leakage channels
refractory
less or non-responsive to a stimulus, unable to respond
