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anatomy exam 2
Terms in this set (46)
Define the resting potential
The resting potential is the transmembrane potential of a normal cell under homeostatic conditions
What effect would a chemical that blocks the voltage- gated sodium channels in neuron plasma membranes have on a neuron's ability to depolarize?
If the voltage-gated sodium channels in a neuron's plasma membrane could not open, sodium ions could not flood into the cell, and it would not be able to depolarize.
What effect would decreasing the concentration of extracellular potassium ions have on the transmembrane potential of a neuron?
If the extracellular concentration of potassium ions decreased, more potassium would leave the cell, and the electrical gradient across the membrane (the transmembrane potential) would increase. This condition is called hyperpolarization.
Define action potential
An action potential is a propagated change in the transmembrane potential of excitable cells, initiated by a change in the membrane permeability to sodium ions.
List the steps involved in the generation and propagation of an action potential
The four steps involved in the generation of action potentials are (1) depolarization to threshold; (2) activation of sodium channels and rapid depolarization; (3) inactivation of sodium channels and activation of potassium channels; and (4) return to normal permeability.
What is the relationship between myelin and the propagation speed of action potentials?
The presence of myelin greatly increases the propagation speed of action potentials.
Which of the following axons is myelinated: one that propagates action potentials at 50 meters per second, or one that carries them at 1 meter per second?
Action potentials travel along myelinated axons at much higher speeds (by saltatory propagation); the axon with a propagation speed of 50 meters per second must be the myelinated axon.
Describe the general structure of a synapse
The major structural components of a synapse, the site where a neuron communicates with another cell, are a presynaptic cell and a postsynaptic cell, whose plasma membranes are separated by a narrow synaptic cleft.
If a synapse involves direct physical contact between cells, it is termed ___________; if the synapse involves a neurotransmitter, it is termed ___________.
If a synapse involves direct physical contact between cells, it is termed electrical; if the synapse involves a neurotransmitter, it is termed chemical.
What effect would blocking voltage-gated calcium channels at a cholinergic synapse have on synaptic communication?
If the voltage-gated calcium channels at a cholinergic synapse were blocked, Ca2 could not enter the presynaptic terminal and trigger the release of ACh into the synapse, so no communication would take place across the synapse.
One pathway in the central nervous system consists of three neurons, another of five neurons. If the neurons in the two pathways are identical, which pathway will transmit impulses more rapidly?
Because of synaptic delay, the pathway with fewer neurons (in this case, three) will transmit impulses more rapidly.
Differentiate between a neurotransmitter and a neuromodulator
Type A fibers are myelinated and carry action potentials very quickly (120 m/sec). Type B are also myelinated, but carry action potentials more slowly due to their smaller diameter. Type C fibers are extremely slow due to their small diameter and lack of myelination.
Describe the events that occur during nerve impulse transmission at a typical cholinergic synapse
(1) The action potential arrives at the synaptic terminal, depolarizing it; (2) extracellular calcium enters the synaptic terminal, triggering the exocytosis of ACh; (3) ACh binds to the postsynaptic membrane and depolarizes the next neuron in the chain; (4) ACh is removed by AChE.
What is the difference between temporal summation and spatial summation?
Temporal summation is the addition of stimuli that arrive at a single synapse in rapid succession. Spatial summation occurs when simultaneous stimuli at multiple synapses have a cumulative effect on the transmembrane potential.
The contraction of flexor muscles and the relaxation of extensor muscles illustrate the principle of
Reflex arcs in which the sensory stimulus and the motor
response occur on the same side of the body
Polysynaptic reflexes can produce far more complicated responses than can monosynaptic reflexes because
the interneurons involved can control several muscle groups
What would happen if the normal circulation or reabsorption of CSF were blocked?
If the normal circulation or reabsorption of cerebrospinal fluid (CSF) became blocked, CSF would continue to be produced at the choroid plexuses in each ventricle, but the fluid would remain there, causing the ventricles to swell—a condition known as hydrocephalus.
How would decreased diffusion across the arachnoid granulations affect the volume of cerebrospinal fluid in the ventricles?
If diffusion across the arachnoid granulations decreased, less CSF would reenter the bloodstream, and CSF would accumulate in the ventricles. The increased pressure within the ventricles due to accumulated CSF could damage the brain.
Many water-soluble molecules that are abundant in the blood occur in small amounts or not at all in the extracellular fluid of the brain. Why?
Many water-soluble molecules are rare or absent in the extracellular fluid (ECF) of the brain because the blood-brain barrier regulates the movement of such molecules from the blood to the ECF of the brain.
The term higher brain centers refers to those areas of the brain involved in higher-order functions. These centers would probably include nuclei, centers, and cortical areas of
the cerebrum, cerebellum, and diencephalon
Which of the following is the site of cerebrospinal fluid production?
The dural fold that divides the two cerebellar hemispheres is the
Cerebrospinal fluid is produced and secreted by
The primary purpose of the blood-brain barrier(BBB) is to
isolate neural tissue in the CNS from the general circulation.
The establishment of emotional states is a function of the
Coordination of learned movement patterns at the subconscious level is performed by
Which structure in the brain would your A&P instructor be referring to when talking about a nucleus that resembles a sea horse and that appears to be important in the storage and retrieval of long-term memories? In which functional system of the brain is it located?
This nucleus is the hippocampus, which is part of the limbic system.
What are the two primary functional roles of the cerebellum?
The cerebellum (1) integrates proprioceptive sensations with visual information from the eyes and equilibrium-related sensations from the internal ear, and (2) adjusts the activities of the voluntary and involuntary motor centers on the basis of sensory information and the stored memories of previous experiences.
The corticospinal tract
carries motor commands from the cerebral cortex to the spinal cord.
What effect does injury to the primary motor cortex have on peripheral muscles?
Injury to the primary motor cortex affects the ability to exert fine control over motor units. Gross movements are still possible, however, because they are controlled by the basal nuclei that use the reticulospinal or rubrospinal tracts. Thus, walking and other voluntary and involuntary movements can be performed with difficulty, and the movements are imprecise and awkward.
Kayla is having difficulty controlling her eye movements and has lost some control of her facial muscles. After an examination and testing, Kayla's physician tells her that her cranial nerves are perfectly normal but that a small tumor is putting pressure on certain fiber tracts in her brain. This pressure is the cause of Kayla's symptoms. Where is the tumor most likely located?
Kayla's tumor is most likely adjacent to the corticobulbar tracts. The axons of those tracts carry action potentials to motor nuclei of the cranial nerves, which control eye muscles and muscles of facial expression.
Harry, a construction worker, suffers a fractured skull when a beam falls on his head. Diagnostic tests indicate severe damage to the motor cortex. His wife is anxious to know if he will ever be able to move or walk again. What would you tell her?
Injuries to the motor cortex eliminate the ability to produce fine control of motor units. However, as long as the cerebral nuclei are functional, gross movements would still be possible. Harry should still be able to walk, maintain his balance, and perform voluntary and involuntary movements using the rubrospinal and reticulospinal tracts in place of the corticospinal tracts. Although these movements may be awkward or difficult, they will still be possible.
A progressive disorder characterized by the loss of higher-order cerebral functions is
What physiological activities distinguish non-REM sleep from REM sleep?
During non-REM sleep, the entire body relaxes, and activity at the cerebral cortex is at a minimum; heart rate, blood pressure, respiratory rate, and energy utilization decline. During REM sleep, active dreaming occurs, accompanied by alterations in blood pressure and respiratory rates; muscle tone decreases markedly, and response to outside stimuli declines.
Damage to the hippocampus, a component of the limbic system, leads to
a loss of long term memory
EPSP's are a result of
Depolarizing sodium current
Which of the following is not a function of the spinal meninges?
Conduction of action potentials
Somatic motor neuron cell bodies are located in the ____ gray horn of the spinal cord and leave the central nervous system via the ____ root.
Have at least one interneuron
Somatic motor commands are initiated in the
primary motor cortex
Which of the following receptor types is direct-acting?
The basal nuclei and cerebellum are both involved in
Helping the primary motor cortex refine movements based on prior experience
Type A neurons
Are myelinated; conduct action potentials faster than type B and C fibers; utilize salutatory propagation
Which of the following neurotransmitters falls into the peptide class?
Spatial summation occurs
When two presynaptic neurons simultaneously stimulate a change in post-synaptic potential
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