Anatomy Chapter 12
The equilibrium potential of sodium is
+66mV.
The equilibrium potential of potassium is
-90mV.
On which structure do most neuron to neuron communications occur?
A
__________ carry sensory information to the CNS.
Afferent neurons
Neurofilament
C
Which of the following can cause demyelination?
Demyelination can be caused by arsenic, diphtheria, multiple sclerosis and mercury.
________ carry motor information to peripheral effectors.
Efferent neurons
Which part(s) of the neuron can propagate an action potential?
L
The _______ division of the peripheral nervous system brings sensory information to the central nervous system.
afferent
The part of the peripheral nervous system that carries sensory information to the CNS is designated
afferent.
The all-or-none principle states that
all stimuli great enough to bring the membrane to threshold will produce identical action potentials.
Neurons that are rare, small, and lack features that distinguish dendrites from axons are called
anaxonic.
What type of membrane channels are found at label "L"?
both voltage-gated Na+ channels and voltage-gated K+ channels
The ________ nervous system is composed of the brain and spinal cord.
central
The sum of the electrical and chemical forces acting on an ion is known as its
electrochemical gradient.
The most common neuron of the nervous system is the
interneuron
Ion channels that are always open are called ________ channels.
leak
Graded potentials
may be either a depolarization or a hyperpolarization.
Which of the following is not involved in creating the resting membrane potential of a neuron?
membrane permeability for sodium ions greater than potassium ions
The cytoplasm that surrounds the nucleus of a neuron is called the
perikaryon.
The nervous tissue outside of the central nervous system composes the _______ nervous system.
peripheral
The efferent division of the peripheral nervous system innervates _________ cells.
skeletal muscle, smooth muscle, heart muscle, glandular
The ________ nervous system controls the skeletal muscles.
somatic
The site of intercellular communication between a neuron and another cell is the
synapse.
Identify the structure labeled "N"
synaptic terminals
Axons terminate in a series of fine extensions known as
telodendria
Identify the structure labeled "M"
telodendria
When potassium channels open and the ions diffuse through the membrane,
the inside of the membrane will become more negative.
If the sodium-potassium pumps in the plasma membrane fail to function, all of the following occur except
the intracellular concentration of potassium ions will increase.
Ions can move across the plasma membrane in which of the following ways?
through voltage-gated channels as in the action potential, through passive or leak channels, by ATP-dependent ion pumps like the sodium-potassium exchange pump, through chemically gated channels as in neuromuscular transmission
Sensory neurons of the PNS are
unipolar
Neurons in which dendritic and axonal processes are continuous and the soma lies off to one side are called
unipolar.
Any stimulus that opens a ________ ion channel will produce a graded potential.
voltage-gated, chemically gated, sodium, mechanically gated
Regions of the CNS with an abundance of myelinated axons constitute the ________ matter.
white
The following are the main steps in the generation of an action potential. 1. Sodium channels are inactivated. 2. Voltage-gated potassium channels open and potassium moves out of the cell, initiating repolarization. 3. Sodium channels regain their normal properties. 4. A graded depolarization brings an area of an excitable membrane to threshold. 5. A temporary hyperpolarization. 6. Sodium channel activation occurs. 7. Sodium ions enter the cell and depolarization.
4, 6, 7, 1, 2, 3, 5
_______ open or close in response to binding specific molecules.
Chemically gated channels
________ nerves are nerves that connect to the brain.
Cranial
Dendrites
Dendrites membranes contain numerous chemically gated ion channels.
Which of the following is not true regarding the establishment of a neuron's resting membrane potential?
Electrical forces do not push sodium ions into the cell.
_________ line the brain ventricles and spinal canal.
Ependymal cells
What is happening at the low point?
Excessive potassium has diffused out causing hyperpolarization.
__________ provide information about the external environment.
Exteroceptors
___________ are the most numerous type of neuron in the CNS.
Interneurons
_________ monitor the digestive, respiratory, cardiovascular, urinary, and reproductive systems.
Internoceptors
Which of the following is true about threshold for an action potential?
It is more positive than the resting membrane potential.
Which of the following is not a function of astrocytes?
They rebuild injured neurons.
Branches that may occur along an axon are called
collaterals
Damage to ependymal cells would most likely affect the
formation of cerebrospinal fluid.
The basic functional unit of the nervous system is the
neuron.
When pressure is applied to neural tissue, all of the following effects are possible except
neurons are triggered to divide
The rabies virus travels to the CNS via
retrograde axoplasmic transport
Glial cells that surround the neurons in ganglia are
satellite cells.
At the normal resting membrane potential of a typical neuron, its sodium-potassium exchange pump transports
3 intracellular sodium ions for 2 extracellular potassium ions.
How would the absolute refractory period be affected if voltage-regulated sodium channels failed to inactivate?
It would last indefinitely.
__________ channels open or close in response to physical distortion of the membrane surface.
Mechanically gated
________ account for roughly half of the volume of the nervous system.
Neuroglia
Clusters of RER and free ribosomes in neurons are called
Nissl bodies
___________ monitor the position of skeletal muscles and joints.
Proprioceptors
The neurilemma of axons in the peripheral nervous system is formed by
Schwann cells
What is happening between the middle and high point?
Sodium ions are entering the axon and causing depolarization.
________ nerves are nerves that connect to the spinal cord.
Spinal
Puffer fish poison blocks voltage-gated sodium channels like a cork. What effect would this neurotoxin have on the function of neurons?
The axon would be unable to generate action potentials.
How would a chemical that prevents the opening of voltage-regulated Na+ channels affect the function of a neuron?
The neuron will only be capable of producing graded potentials.
Which of the following statements about the action potential is false?
The rapid depolarization phase is caused by the entry of potassium ions.
How does blocking retrograde axoplasmic transport in an axon affect the activity of a neuron?
The soma becomes unable to respond to changes in the distal end of the axon.
Deteriorating changes in the distal segment of an axon as a result of a break between it and the soma is called ________ degeneration.
Wallerian
The largest and most numerous of the glial cells in the central nervous system are the
astrocytes.
The neuroglial cells that participate in maintaining the blood-brain barrier are the
astrocytes.
The ________ nervous system provides involuntary regulation of smooth muscle, cardiac muscle, and glandular activity.
autonomic
The plasma membrane of an axon is called the
axolemma
The axon is connected to the soma at the
axon hillock
Neurons that have one axon and one dendrite, with the soma in between, are called
bipolar.
Raising the potassium ion concentration in the extracellular fluid surrounding a nerve cell will have which effect?
both hyperpolarize it and decrease the magnitude of the potassium equilibrium potential
Most neurons lack ________ and so are permanently blocked from undergoing cell division.
centrioles
If acetylcholine (ACh) causes inhibition of a postsynaptic neuron, to what type of membrane channel did the ACh bind?
chemically-regulated potassium channel
Functions of astrocytes include all of the following, except
conducting action potentials.
A movement of charges in response to a potential difference is called
current.
A threshold stimulus is the
depolarization necessary to cause an action potential.
A shift of the resting transmembrance potential toward 0 mV is called
depolarization.
Opening of sodium channels in the axon membrane causes
depolarization.
All of the following cause demyelination except
dopamine deficiency.
The _______ division of the nervous system carries motor commands to muscles and glands.
efferent
In the peripheral nervous system, Schwann cells participate in the repair of damaged nerves by
forming a cellular cord that directs axonal regrowth.
Regions of the CNS where neuron cell bodies dominate constitute the ________ matter.
gray
Voltage-gated channels are present
in the membrane that covers axons.
Voltage-gated sodium channels have both an activation gate and a(n) ________ gate.
inactivation
If the permeability of a resting axon to a sodium ion increases,
inward movement of sodium will increase and the membrane will depolarize.
Which of the following is not a function of the neuroglia?
memory
Small, wandering cells that engulf cell debris and pathogens in the CNS are called
microglia
The sodium-potassium ion exchange pump
moves sodium and potassium opposite to the direction of their electrochemical gradients.
The most abundant class of neuron in the central nervous system is
multipolar
Neurons that have several dendrites and a single axon are called
multipolar.
What is contained inside a synaptic terminal?
neurotransmitter molecules
The axoplasm of the axon contains which of the following?
neurotubules, mitochondria, vesicles, neurofibrils
The tiny gaps between adjacent Schwann cells are called
nodes of Ranvier.
The myelin sheath that covers many CNS axons is formed by
oligodendrocytes.
During depolarization of a neuron
potassium ions move out of the cell.
Which of the following is not a recognized structural classification for neurons?
pseudopolar
Which of the following is a type of glial cell found in the peripheral nervous system?
satellite cells
Which of the following activities or sensations is/are not monitored by interoceptors?
sight
