Ch 8 Physiology Mastering
Which membrane potential opens a sufficient number of the voltage-gated Na+ channels to cause a significant change in the membrane potential (making it much less negative)?
-60 mV
The following are steps involved in transmission at the cholinergic synapse: 1. Chemically regulated ion channels on the postsynaptic membrane are activated. 2. Calcium ions enter the axon terminal. 3. An action potential depolarizes the axon terminal at the presynaptic membrane. 4. Acetylcholine is released from storage vesicles by exocytosis. 5. Acetylcholine binds to receptors on the postsynaptic membrane. The correct sequence for these events is
3, 2, 4, 5, 1
Arrange the following events in the proper sequence: 1. Efferent neuron reaches threshold and fires an action potential. 2. Afferent neuron reaches threshold and fires an action potential. 3. Effector organ responds by performing output. 4. Integrating center reaches decision about response. 5. Sensory organ detects change in the environment.
5, 2, 4, 1, 3
Threshold is achieved when
A neuron is stimulated strongly enough to trigger an action potential.
A weak, subthreshold stimulus will result in _______.
A small depolarization at the receiving end of the NEURON
The time during which an excitable membrane CANNOT respond to further stimulation regardless of the stimulus strength is the
Absolute refractory period.
Match the type of signal to its description. A. graded potential B. action potential C. both Originate(s) at the trigger zone
Action potential
Match the type of signal to its description. A. graded potential B. action potential C. both Require(s) a minimum stimulus to occur
Action potential
The all-or-none principle states that
All stimuli great enough to bring the membrane to threshold will produce identical action potentials
When two or more graded potentials arrive at the trigger zone, which of the following could happen?
An excitatory & inhibitory signal can cancel each other out Two excitatory stimuli may be additive, & summation could occur Two inhibitory stimuli may be additive, resulting in lower excitability.
A DEPOLARIZING synaptic potential is also known as _______.
An excitatory postsynaptic potential (EPSP)
Match the term with its description. A. ependymal cells B. astrocytes C. satellite cells D. Schwann cells E. oligodendrocytes F. microglia Highly branched cells that transfer nutrients between blood vessels & neurons
Astrocytes
An excitatory postsynaptic potential occurs _______.
At the receiving end of the INTERNEURON
The sympathetic and parasympathetic nervous systems are divisions of which system?
Autonomic nervous system
Match the part of the neuron to its description. A. dendrites B. axon C. cell body Location of voltage-gated ion channels
Axon
Which 2 properties determine the conduction velocity in a mammalian neuron?
Axon diameter & the Leak resistance of the membrane
A chemical synapse USUALLY includes ________.
Axon terminal Presynaptic cell Synaptic cleft Postsynaptic cell
NT is stored and released from
Axon terminals & axon varicosities
Which of the following describes a similarity between graded potentials & action potentials?
Both can involve voltage-gated sodium channels.
Match the glial cell to the nervous system division in which it is found. A. central nervous system B. peripheral nervous system Ependymal cells
CNS
Match the glial cell to the nervous system division in which it is found. A. central nervous system B. peripheral nervous system Microglia
CNS
A damaged neuron has a better chance of survival & repair if the ________ is/are undamaged.
Cell body
Match the part of the neuron to its description. A. dendrites B. axon C. cell body Make(s) proteins necessary for repair of damaged neuron
Cell body
Match the part of the neuron to its description. A. dendrites B. axon C. cell body Supported by satellite cells
Cell body
At a(n) ________ synapse, a neurotransmitter is released to affect the postsynaptic cell.
Chemical
Which type of synapse is most prevalent in the nervous system?
Chemical synapse
The part of the neuron that RECEIVES most of the incoming signals is the __________.
Dendrite
Match the part of the neuron to its description. A. dendrites B. axon C. cell body Receive(s) most of the incoming synapses
Dendrites
The multiple thin, branched structures on a neuron whose main function is to RECEIVE incoming signals are the
Dendrites.
An excitatory postsynaptic potential (EPSP)
Depolarizes a neuron, INCREASING the likelihood of an action potential.
The absolute refractory period of an action potential
Ensures one-way travel down an axon Allows a neuron to ignore a 2nd signal sent that closely follows the 1st Prevents summation of action potentials.
Match the term with its description. A. ependymal cells B. astrocytes C. satellite cells D. Schwann cells E. oligodendrocytes F. microglia Cells that are a source of neural stem cells
Ependymal cells
Graded potentials that arrive at postsynaptic neurons are called ________ if they make that cell more likely to fire.
Excitatory
Anterograde & retrograde axonal transport are forms of ________ transport.
Fast
Which is/are the most common inhibitory NT of the CNS?
GABA & glycine
An axon that is MORE NEGATIVE than the resting membrane potential is said to be _______.
Hyperpolarized
Where do most action potentials originate?
Initial segment (axon hillock)
During an action potential, activation of voltage-gated sodium & potassium channels occurs at different rates. What is the effect of this difference on ion flow across an axon membrane?
Initially, Na+ flows INTO the cell followed by K+ flowing OUT of the cell.
The inactivation gate
Is coupled to the movement of the activation gate, but is much slower.
What would happen to the membrane potential if a resting cell suddenly becomes MORE PERMEABLE to Na+?
It would DEPOLARIZE.
If an increase in EC potassium hyperpolarizes a neuron, which of the following would be correct?
It would change the membrane potential to a MORE NEGATIVE value.
The major determinant of the resting potential of all cells is
K+ gradient between the blood & interstitial fluid.
The channels that provide for the movement of potassium in the resting neuron are _______.
Leakage
A suprathreshold stimulus results in _______.
MORE action potentials
Spatial summation refers to
Multiple graded potentials arriving at one location simultaneously.
A single action potential is described as _______.
NOT graded
When voltage-gated Na+ channels of a resting neuron open,
Na+ enters the neuron & the neuron depolarizes.
The rising phase of the action potential is due to
Na+ flow into the cell only.
Which type of receptor would bind acetylcholine & be found in skeletal muscle?
Nicotinic cholinergic
Increasing the voltage resulted in which of the following?
No change to the action potential
The gaps between adjacent Schwann cells on an axon are called
Nodes of Ranvier
If a hyperpolarizing graded potential & a depolarizing graded potential of similar magnitudes arrive at the trigger zone at the same time, what is MOST likely to occur?
Nothing. They will cancel each other out.
Match the term with its description. A. ependymal cells B. astrocytes C. satellite cells D. Schwann cells E. oligodendrocytes F. microglia Cells in the CNS that form myelin
Oligodendrocytes
Which glial cells form myelin in the central nervous system?
Oligodendrocytes
What characterizes repolarization, the 2n phase of the action potential?
Once the membrane depolarizes to a peak value of +30 mV, it repolarizes to its negative resting value of -70 mV.
The inhibitory neurotransmitters of the CNS, GABA and glycine, act by opening ________ channels.
Only Cl-
What effect did DE-creasing the EC sodium have on the resting membrane potential?
Only a small change occurred, because the resting neuron is not very permeable to sodium.
Interneurons are found
Only in the CNS.
The point during an action potential when the inside of the cell has become MORE POSITIVE than the outside is known as the
Overshoot.
Match the glial cell to the nervous system division in which it is found. A. central nervous system B. peripheral nervous system Schwann cells
PNS
The afferent and efferent axons together form the
PNS.
Which ion(s) is/are higher in concentration INSIDE the cell compared to outside?
Potassium
Which of the following would NOT cause the membrane potential to change from -70 mV to +30 mV?
Potassium ions leaving the cell (because then it will be MORE negative)
Glial cells
Provide structural & metabolic support. Provide structural & metabolic support & help maintain homeostasis of the brain's EC fluid. Guide neurons during growth & repair. Help maintain homeostasis of the brain's EC fluid.
Most neurons have at least two processes extending from the soma, or cell body. Which type of neuron only has ONE process extending from the cell body?
Pseudounipolar neuron
Match the term with its description. A. ependymal cells B. astrocytes C. satellite cells D. Schwann cells E. oligodendrocytes F. microglia Cells that form supportive capsules around cell bodies
Satellite cells
Match the term with its description. A. ependymal cells B. astrocytes C. satellite cells D. Schwann cells E. oligodendrocytes F. microglia Cells that myelinate only one axon each; Multiple cells per axon
Schwann cells
Myelin is formed by
Schwann cells & oligodendrocytes.
To increase the amount of NT released onto a postsynaptic cell, the presynaptic cell would have to
Send action potentials with HIGHER frequency.
Which of the following neurons or groups of neurons are NOT considered to be a part of the efferent pathway?
Sensory
Information coming into the CNS is transmitted along ________ neurons.
Sensory & afferent
The stimulus for graded potentials includes _______.
Sensory stimuli & neurotransmitter
Calcium is important in the synapse because it
Signals the exocytosis of the NT.
Establishing the resting membrane potential requires energy through the use of the _______.
Sodium-potassium pump
Autonomic motor neurons are subdivided into the
Sympathetic & parasympathetic divisions.
When a second EPSP arrives at a single synapse before the effects of the first have disappeared, what occurs?
Temporal summation
Increasing the strength of the stimulus applied to the sensory receptor increased _______.
The frequency of action potentials in the sensory neuron The amount of NT released at the axon terminal of the sensory neuron The frequency of action potentials in the interneuron
Once the stimulus alters the receptor on the cell's membrane, what happens next?
The membrane permeability is altered. A second messenger is activated on the inside of the cell. Ion channels open, allowing ions to enter or exit.
What characterizes depolarization, the 1st phase of the action potential?
The membrane potential changes from a NEGATIVE value --> POSITIVE value.
What event triggers the generation of an Action Potential?
The membrane potential must DEPOLARIZE from the resting voltage of -70 mV to a threshold value of -55 mV.
The Nernst equation predicts
The membrane potential resulting from permeability to a single ion.
Which stimulus was at/above threshold?
The moderate & strong stimuli
What does the Goldman-Hodgkin-Katz equation take into account that the Nernst equation does NOT?
The permeabilities of the ions
When sodium channels open during an action potential, the opening is caused by
The presence of positive charge.
What effect did IN-creasing the EC potassium have on the resting membrane potential?
The resting membrane potential became LESS NEGATIVE.
Whether/not a neuron produces an action potential at a given moment depends on ________.
The total potential change reaching threshold voltage at the trigger zone
Why are Na+, K+, & Cl- the only ions considered in the GK equation when calculating resting membrane potential (Vm)?
These are the ions to which cell membranes are permeable at rest.
The minimum voltage that is required to generate an action potential is called the _______.
Threshold voltage
The resting membrane potential results from
Uneven distribution of ions across the cell membrane & differences in membrane permeability to Na+ & K+.
What opens first in response to a threshold stimulus?
Voltage-gated Na+ channels
What is the first change to occur in response to a threshold stimulus?
Voltage-gated Na+ channels change shape, & their activation gates open.
The sodium-potassium exchange pump
requires ATP to function.
