Chapter 12 Neurophysiology
Threshold potential is: +55 mV -70 mV +70 mV +90 mV -55 mV -90 mV
-55 mV
The resting membrane potential of a typical nerve cell is: 0 mV -55mV +70mV -70mV +30mV
-70mV
An action potential is initiated when: -the membrane potential reaches -55 mV at the axon hillock -voltage-gated Na+ channels open at the axon hillock -spatial and/or temporal summation of graded potentials is strong enough -All choices are correct -the threshold potential is reached at the axon hillock
-All choices are correct
Following the arrival of an action potential at the axon terminal, place the following steps in transmission across the synapses in order: 1. neurotransmitters are released by exocytosis from the presynaptic terminal 2. voltage-gated calcium channels open on the axon terminal and calcium flows into the terminal 3. the neurotransmitter binds with a receptor protein on the postsynaptic membrane 4. Neurotransmitters diffuse across the synaptic cleft 5. Na+ channels open and the postsynaptic membrane is depolarized 5, 1. 4, 3, 2 1, 2, 3, 4, 5 1, 4, 3, 2, 5 2, 1, 4, 3, 5 2, 3, 1, 5, 4
2, 1, 4, 3, 5
When two or more graded potentials arrive at the trigger zone (axon hillock), which of the following could happen? A. An excitatory and inhibitory signal can cancel each other out B. Two excitatory stimuli may be additive and summation could occur C. Two inhibitory stimuli may be additive and depolarization to the threshold could occur A, B & C C Only A and B
A and B
Which of the following statements concerning acetylcholine is FALSE? -Synthesis of acetylcholine occurs in the axon terminal -Acetylcholine is degraded into carbon dioxide and water in the postsynaptic cell -It is synthesized from the precursors acetyl coenzyme A and choline -The enzyme acetylcholinesterase destroys acetylcholine in the synaptic cleft
Acetylcholine is degraded into carbon dioxide and water in the postsynaptic cell
Information coming into the central nervous system is transmitted along __________ neurons. Sensory and Efferent Afferent Afferent and Sensory Efferent Sensory
Afferent
Which neuroglial cell plays a role in forming the blood-brain barrier in the CNS? Satellite cells Astrocytes Microglial Schwann cells Oligodendrocytes
Astrocytes
Action potentials are initiated at the __________ of a motor neuron. Dendrites Axon hillock Cell bodies
Axon hillock
A type of change in membrane potential in which the membrane potential becomes less negative (a.k.a more positive) than resting potential is termed: Repolarization Depolarization Hyperpolarization Inhibiting
Depolarization
During the absolute refractory period only strong stimuli will trigger another action potential. True False
False
Presynaptic facilitation would decrease the amount of neurotransmitters released from a presynaptic neurons's axon terminal. True False
False
The enzyme monoamine oxidase is responsible for the deactivation of norepinephrine in the synaptic cleft. True False
False
The dendrites and cell body are the neuron's output zone because these components send out signals. True False
False
The dendrites and cell body are the neuron's output zone because these components send out signals. True False
False
The outward movement of sodium ions rapidly restores the negative resting potential. True False
False
Clusters of nerve cell bodies in the peripheral nervous system are called: Neuroglia Nodes Ganglia Microglia White matter
Ganglia
Under normal circumstances, the preferred fuel source for the neurons of the brain is: Ketones Fatty acids Amino acids Glucose Lactic acid
Glucose
A change in membrane potential from -70 mV to -90 mV is an example of: Depolarization Repolarization Absolute refractory Hyperpolarization
Hyperpolarization
An inhibitory postsynaptic potential (IPSP) causes: Repolarization Depolarization Lowering the threshold for an action potential to occur Initiation of an action potential Hyperpolarization
Hyperpolarization
After an action potential has peaked (+30 mV), which ion gates close? Ligand gated calcium channels Ligand gated sodium channels Activation gate of voltage gated sodium channels Voltage gated potassium channels Inactivation gate of voltage gated sodium channels
Inactivation gate of voltage gated sodium channels
After an action potential has peaked (+30 mV), which ion gates close? Voltage gated potassium channels Ligand gated calcium channels Ligand gated sodium channels Inactivation gate of voltage gated sodium channels Activation gate of voltage gated sodium channels
Inactivation gate of voltage gated sodium channels
All of the following regarding inhibitory postsynaptic potentials are true EXCEPT: K+ rushes out Membrane potential moves towards threshold Binding of neurotransmitters causes the membrane potential to become more negative Cl- rushes in Causes K+ channels to open
Membrane potential moves towards threshold
Repolarization involves: Potassium ions flooding out of the cell All of the choices are correct. Sodium ions flooding into the cell Results in a net negative charge on the outside of the membrane, positive on the inside None of the choices are correct
None of the choices are correct
Which of the following will occur when an excitatory postsynaptic potential is being generated? Potassium gates open and repolarization occurs Sodium gates open and depolarization occurs The membrane potential becomes more negative All choices are correct Chloride gates open and Cl- rushes into the cell
Sodium gates open and depolarization occurs
Which of the following will occur when an excitatory postsynaptic potential is being generated? Sodium gates open and depolarization occurs Potassium gates open and repolarization occurs All choices are correct Chloride gates open and Cl- rushes into the cell The membrane potential becomes more negative
Sodium gates open and depolarization occurs
In a resting neuron, the concentration of: Sodium ions is higher in the intracellular fluid and potassium in the extracellular fluid Sodium and potassium ions is higher in the intracellular fluid Sodium and potassium ions is higher in the extracellular fluid Sodium ions is higher in the extracellular fluid and potassium in the intracellular fluid Sodium and potassium ions are equal on the inside and outside of the membrane
Sodium ions is higher in the extracellular fluid and potassium in the intracellular fluid
All of the following are true of excitatory postsynaptic potentials EXCEPT: The membrane potential gets closer to reaching threshold potential The axon hillock becomes becomes more negative The membrane potential becomes less negative The neuron gets closer to firing an action potential
The axon hillock becomes becomes more negative
The neurotransmitter acetylcholine is inactivated by: Diffusing into the blood and broken down by the liver The enzyme monoamine oxidase Being taken up by the presynaptic neuron The enzyme acetylcholinesterase
The enzyme acetylcholinesterase
What ensures the one-way propagation of an action potential away from the initial site of activation? The electrical period The salutatory period The refractory period
The refractory period
During the relative refractory period, there is no response to a stimulus of normal threshold magnitude but the neuron can generate an action potential if the stimulus is of higher magnitude. False True
True
The stronger the triggering event, the larger the resultant graded potential. True False
True
The voltage-gated sodium channel has two gates: an activation gate and an inactivation gate True False
True
All of the following are true of summation EXCEPT: The axon hillock keeps score of all graded potentials received Spatial summation involves a postsynaptic neuron stimulated by multiple presynaptic neurons at the same time a single excitatory postsynaptic potential (EPSP) can induce an action potential
a single excitatory postsynaptic potential (EPSP) can induce an action potential
Graded potentials occur along the __________ of neurons, while action potentials occur along __________ of neurons. cell bodies; dendrites cell bodies and dendrites; axons axons; cell bodies and dendrites axons and cell bodies; dendrites
cell bodies and dendrites; axons
Saltatory conduction of action potentials can only occur in an unmyelinated axon. true false
false
The outward movement of sodium ions rapidly restores the negative resting potential. true false
false
Which of the following pairings is INCORRECT: synaptic end knobs - voltage gated channels graded potential - voltage gated channels relative refractory period - hyperpolarization absolute refractory period - depolarization and repolarization action potential - voltage gated channels
graded potential - voltage gated channels
Which type of neuroglial cell forms the myelin sheath in peripheral neurons? neurolemmocytes (Schwann) cells microglial oligodendrocytes
neurolemmocytes (Schwann) cells
To what ions do inhibitory synapses become more permeable? potassium or chloride sodium or chloride potassium or calcium calcium or chloride potassium or sodium
potassium or chloride
In a resting neuron, the concentration of: -Sodium ions are higher in the intracellular fluid and potassium in the extracellular fluid -sodium ions are higher in the extracellular fluid and potassium in the intracellular fluid -sodium and potassium ions are equal on the inside and outside of the membrane
sodium ions are higher in the extracellular fluid and potassium in the intracellular fluid
Consider two presynaptic neurons synapsing onto a single postsynaptic neuron. The release of neurotransmitters from each individual presynaptic neuron causes a graded EPSP but not an action potential in the postsynaptic cell. However, when both of these presynaptic neurons stimulate the postsynaptic neuron at the same time an action potential is generated in the postsynaptic neuron. This is an example of: presynaptic inhibition spatial summation temporal summation
spatial summation
_________ refers to when a postsynaptic neuron is stimulated by multiple presynaptic neurons at the same time. presynaptic facilitation temporal summation spatial summation presynaptic inhibition saltatory conduction
spatial summation
Which of the following statements concerning the propagation of action potentials is INCORRECT? -the refractory period places a limit on the frequency in which a neuron can conduct action potentials -All choices are correct -stronger stimuli will produce action potentials stronger in amplitude -conduction by local current flow is slower than conduction by saltatory conduction -saltatory conduction occurs in myelinated axons
stronger stimuli will produce action potentials stronger in amplitude
With the exception of olfaction, all sensory pathways first travel to the ________, which acts as a relay station to the cerebrum. pons hypothalamus cerebellum thalamus
thalamus
Which is NOT a factor contributing to the resting membrane potential? the membrane is 50 to 75 times more permeable to K+ than to Na+ the sodium-potassium pump the presence of fixed negatively charged proteins inside the cell the presence of more Na+ leaky channels than K+ leaky channels
the presence of more Na+ leaky channels than K+ leaky channels
Which of the following statements is FALSE about graded potentials, they: are the precursor to action potentials are short lived they travel down the axon without diminishing in strength are local changes in the membrane potential
they travel down the axon without diminishing in strength
What ensures the one-way propagation of an action potential away from the initial site of activation? The refractory period The electrical period The activation period The salutatory period The rest period
The refractory period
What extensions project like antennae away from the nerve's cell body and conduct signals towards the body? dendrites mitochondria axons endoplasmic reticulum organelles
dendrites
The strength of a stimulus is coded by the ____. frequency of action potentials strength of action potentials frequency of salutatory periods duration of the refractory periods duration of the resting period
frequency of action potentials
What are the two basic forms of electrical signals? physical and action potentials high potentials and low potentials graded potentials and chemical potentials graded potentials and action potentials physical potentials and chemical potentials
graded potentials and action potentials
What are the chemical messenger for the nervous system? neurotransmitters released into the synaptic cleft neurotransmitters released into the blood hormones released into the blood hormones released in the spinal canal hormones released into the synaptic cleft
neurotransmitters released into the synaptic cleft
In general terms, what sort of distance do graded potentials die out over? long distances graded distances short distances active distances
short distances
Depolarization from the resting potential of -70 mV proceeds slowly until it reaches a critical level known as ____. depolarizing potential threshold potential electrical action polarizing action active potential
threshold potential
