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120 Cards in this Set

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What are the 2 major divisions of the nervous system?
The Central Nervous System (CNS) and
The Peripheral Nervous System (PNS)
Pg. 072
What are Neuroglia cells?
Supporting cells located in the CNS.
Pg. 072
What are the 3 major parts of a Neuron?
1) The Cell Body
2) Dendrites
3) Axons
pg. 072
What type of insulating material surrounds many of the axons?
Myelin Sheath
Pg. 072
What is a myelin sheath?
A type of insulating material that surrounds many axons.
Pg. 072
What is the part of the “structure that conducts impulses away from the cell body” that does not have myelin surrounding it?
The Axon Hillock
Pg. 072
What is the Axon Hillock?
The initial segment of the axon.
Pg. 072
What does the CNS consist of?
The Brain and Spinal Cord
Pg. 072
What does the PNS consist of?
Everything else in the nervous system with the exception of the brain and spinal cord.
Pg. 072
What are nerves?
Bundles of axons located in the PNS.
Pg. 072
What do the bundles of PNS axons enter into?
They enter either the brain or spinal cord.
Pg. 072
What are the collection of axons called in the CNS?
Tracts
Pg. 072
What are Ganglia?
Bundles of neuron cell bodies located in the PNS.
Pg. 072
What are groupings of nerve cell bodies in the CNS called?
Nuclei
Pg. 072
What are neurons in the PNS functionally classified as?
Sensory Neurons
or
Motor Neurons
Pg. 072
What direction do Sensory neurons conduct impulses with regard to the CNS?
They conduct impulses into the CNS.
Pg. 072
What is another name for Sensory Neurons?
Afferent Neurons
Pg. 072
What direction do Motor neurons conduct impulses with regard to the CNS?
They conduct impulses out of the CNS.
Pg. 072
What is another name for Motor Neurons?
Efferent Neurons
Pg. 073
What is the division of efferent neurons that stimulate skeletal muscles called?
Somatic motor Neurons
Pg. 073
What is the division of motor neurons that stimulate smooth muscles, cardiac muscles and glands called?
Autonomic Motor Neurons
Pg. 073
What are the neurons that stimulate smooth muscles, cardiac muscles and glands subdivided into?
Sympathetic and Parasympathetic
Pg. 073
True or False. Autonomic motor neurons can be innervate effectors voluntarily.
False. Autonomic motor neurons innervate involuntary effectors.
Pg. 073
What are neurons whose dendrites, cell body, and axons are located entirely within the CNS known as?
Association Neurons
Pg. 073
What functions do association neurons have?
They can: Receive sensory information, integrate and analyze information and stimulate motor neurons.
Pg. 073
Structurally, how are neurons classified?
They are classified according to their number of extensions, or processes.
Pg. 073
What structurally does a Bipolar neuron consist of?
2 processes, 1dendrite and 1axon
Pg. 073
What structural classification do most sensory neurons have?
Most are Pseudounipolar
Pg. 073
What structurally does a Pseudounipolar neuron consist of?
They have 1 process but it later divides into 2processes.
Pg. 073
What structural classification do neurons whose dendrites, cell body, and axons located entirely within the CNS have?
Multipolar
Pg. 073
What types of neurons have a multipolar structural classification?
Motor Neurons and Association Neurons
Pg. 073
What structurally does a Multipolar neuron consist of?
They have many dendrites and only a single axon.
Pg. 073
What is the nervous system’s ratio of supporting cells to neurons?
There are about 5 times more supporting cells than neurons.
Pg. 073
What are the names of the 2 kinds of supporting cells in the PNS?
Schwann Cells and Satellite Cells
Pg. 073
What function do Schwann Cells serve in the PNS?
They form myelin sheaths around many of the axons in PNS.
Pg. 073
What function do Satellite Cells serve in the PNS?
They support neuron cell bodies in the ganglia of the PNS.
Pg. 073
What are the supporting cells in the CNS known as?
Neuroglial cells, or (Neuroglia, Glial cells or Glia)
Pg. 073
What are the names of the different neuroglial cells?
Oligodendrocytes
Astrocytes
Microglia
Ependyma
Pg. 073
What function do Oligodendrocytes serve?
They form myelin sheaths around axons in the CNS.
Pg. 073
How are Oligodendrocytes and Schwann cells similar and different?
They both form myelin sheaths around axons.
However Oligodendrocytes = CNS
and
Schwann cells = PNS.
Pg. 073
What function do Astrocytes serve?
Astrocytes have extensions that surround blood capillaries and extensions in close proximity to axons at synapses.
Pg. 073
What function do Microglia cells serve?
They are the nervous system’s phagocytic cells.
Pg. 073
What function do Ependyma cells serve?
They are an epithelial layer that lines the ventricles of the brain and the central canal of the spinal cord.
Pg. 073
What structures do Ependyma cells line?
The ventricles of the brain and the central canal of the spinal cord.
Pg. 073
What do the blood capillaries in the brain lack compared to capillaries in other organs?
They lack pores in their walls.
Pg. 073
What is a consequence of the brain’s blood capillaries lacking pores?
There is no filtration of fluid out of the capillaries of the brain as compared to what happens with other organs.
Pg. 073
How does the brain obtain nutrients and regulatory molecules since there are no pores in the brain’s blood capillaries?
The Nutrients and Regulatory molecules move through the cytoplasm of the cells by Diffusion, Active Transport, Endocytosis and Exocytosis.
Pg. 073
What neuroglial cell has a direct relationship to the selectivity of the brain’s blood capillaries?
Astrocytes
Pg. 073
What is the selective ability of molecules passing from the blood to the brain known as?
Blood-Brain Barrier
Pg. 074
The nervous system contains what kinds or axons?
Myelinated axons
and
Unmyelinated Axons
Pg. 074
True or False. Schwann cells only surround myelinated axons in the PNS.
False. Schwann cells surround both myelinated and unmyelinated axons in the PNS.
Pg. 074
What are the term(s) given to describe what is formed when Schwann cells surround myelinated and unmyelinated axons?
Sheath of Schwann
or
Neurilemma
Pg. 074
What is believed to aid in the ability of damaged axons in the PNS to regenerate and what does it form?
The Sheath of Schwann by forming a regeneration tube.
Pg. 074
What is the difference between myelinated and unmyelinated axons in the PNS?
In Myelinated axons the Schwann cells wrap themselves around the axon.
Pg. 074
What happens as a Schwann cell wraps itself around the axon?
It’s cytoplasm is squeezed to the outside.
Pg. 074
What is produced by Schwann cells wrapping themselves over and over again around the same section of axon with then a different Schwann cell wrapping itself around the next section and what are they called?
Gaps are produced.
They are called Nodes of Ranvier
Pg. 074
True or False. Oligodendrocytes form myelin sheaths the exact same way in the CNS as Schwann cells do in the PNS.
False. Oligodendroccytes form myelin sheaths in a similar way except Oligodendrocytes have several extensions that are able to form myelin sheaths around several axons.
Pg. 074
What is the direct result of Oligodendrocytes having several extensions enabling formation of myelin sheaths around several axons?
There is not a continuous Sheath of Schwann or Neruilemma around axons in the CNS the way there is a continuous Sheath of Schwann around axons in the PNS.
Pg. 074
What are reason(s) why CNS axons do not commonly regenerate are they are damaged?
1) There is not a continuous Sheath of Schwann or Neruilemma around the axons of the CNS.
2) Regeneration of CNS axons is also inhibited by molecules produced by Oligodendrocytes and Astrocytes.
Pg. 074
True or False. The CNS contains both white matter and gray matter.
True
Pg. 074
What color do the areas of the CNS have that contain mostly axons?
White
Pg. 074
Why do the areas of the CNS that contain mostly axons have a white color?
Because of the phospholipids of plasma membranes of the myelin sheaths.
Pg. 074
What does the “white matter” of the CNS contain?
Axon tracts
Pg. 074
What “major parts of a neuron” compose the “gray matter” of the CNS and why is it gray?
Cell bodies and Dendrites Because there are no myelin sheaths surrounding the cell bodies and dendrites.
Pg. 075
What is the color of the brain’s surface and its inner core?
Brain’s surface = Gray
Inner core = White
Pg. 075
What are action potentials?
They are nerve impulses produced by axons
Pg. 075
True or False. Action potentials are all-or-nothing and they do not decrease in amplitude.
True
Pg. 075
In measuring membrane potential what are the leads connected to which indicates voltage and also graphs the rapid changes in the membrane potential?
Oscilloscope
Pg. 075
What is the process called when membrane potential decreases or (goes to zero)?
Depolarization
Pg. 075
What is the process called when membrane potential increases or (goes to a higher voltage which is even more negative on the inside)?
Hyperpolarization
Pg. 075
What direction will an oscilloscope deflection occur in respect to the resting membrane potential during depolarization?
Upward direction
Pg. 075
What direction will an oscilloscope deflection occur in respect to the resting membrane potential during hyperpolarization?
Downward direction
Pg. 075
How are gated ion channels in the axon regulated?
They are voltage-regulated
Pg. 075
How are the axon’s Na+ and K+ plasma membrane channels stimulated to open?
They are stimulated to open by depolarization.
Pg. 076
What are other names for the gated Na+ and K+ channels in an axon’s membrane?
Voltage-Gated Channels or Voltage-Regulated Channels
Pg. 076
Why are gated channels for Na+ and K+ in an axon’s membrane also called Voltage-Gated or Voltage-Regulated Channels?
Because these channels open in response to a Depolarization Stimulus.
Pg. 076
What term is used to identify “the certain level” a depolarization stimulus must reach in order to open the voltage-gated channels?
The Threshold
Pg. 075
What threshold must Voltage-Gated Na+ Channels be depolarized to in order to open?
They must be depolarized from the RMP of -70 mV to approximately -55 mV.
Pg. 076
True or False. A Voltage-Regulated ion channel is only open for about a millisecond before it becomes inactivated.
True
Pg. 076
What is one of the types of polypeptides that may be involved with inactivating a gated ion channel and how do these particular molecules accomplish this?
Ball and Chain type polypeptide.
They block the channel.
Pg. 076
What is the difference between closed and inactivated gated ion channels?
Closed channels = can be opened by a depolarization stimulus
Inactivated channels = cannot be opened by a depolarization stimulus
Pg. 076
Approximately how long does an inactivated channel stay inactivated?
Approximately 1 millisecond
Pg. 076
Where do the “action potentials” or “nerve impulses” generally begin?
At the axon hillock
Pg. 076
Why is the stimulus for an action potential the depolarization of the axon’s plasma membrane?
1) Because the opening of Voltage-Gated Na+ and K+ channels produces the action potential.
2) Because production of the action potential’s depolarization stimulus originates at the synapse.
Pg. 076
What will happen if depolarization is not sufficient enough to reach -55 mV?
The voltage-Gated ion channels remain closed.
No action potential is produced.
The depolarization will gradually decay and will disappear after it travels about 1-2 mm.
Pg. 077
What is the term for an axon’s ability to spread potential charge along the axon?
“Cable Properties”
Pg. 077
Why is the spread of potential charge over distance short?
1) Because charges can leak through the plasma membrane.
2) Because there is internal resistance of the axon cytoplasm to the spread of charges.
Pg. 077
True or False. An axon conducts charges equally as well as the conduction of electricity by a wire.
False
Pg. 077
What general action produces an action potential?
The sequential opening and closing of Na+ and K+ channels.
Pg. 077
What kind of mechanism is the effect of Na+ diffusing into an axon causing it to become more polarized and example of?
Positive feedback effect
Pg. 077
What happens at the same time Voltage-Gated Na+ channels become inactivated?
The Voltage-Gated K+ channels open.
Pg. 077
How is the membrane potential of an axon brought back down to RMP from +30 mV?
Voltage-Gated Na+ channels become inactivated while at the same time Voltage-Gated K+ channels open allowing K+ to flow out of the axon.
Pg. 077
How do the voltages change during depolarization?
There is a rapid change from -70 mV to +30 mV.
Pg. 077
What is the process of membrane potential going from +30 mV to -70 mV called?
Re-polarization
Pg. 077
Why is the use of ATP necessary for Depolarization and Re-polarization?
1) To maintain the concentration gradients
2) To restore the concentration of Na+ and K+
Pg. 077
What are the certain characteristics of Action Potentials?
1) They are an All-or-None event.
2) The frequency a membrane fires action potentials are determined by the strength of a depolarization stimulus above threshold.
3) They have a Refractory Period
Pg. 077-078
What is meant by an action potential being an “all-or-none” event?
It fires to its maximum amplitude or it does not fire.
Pg. 078
What is the Refractory Period of an action potential?
It is the period of time a plasma membrane has when an action potential has been produced and cannot produce a second one.
Pg. 078
What specific term is used to describe the phase a membrane cannot respond, that occurs during the production of the action potential?
Absolute Refractory Period
Pg. 078
Why does the Absolute Refractory Period occur?
It results from the inactivation of the Na+ channels.
Pg. 078
What specific term is used to describe the phase of a membrane immediately following the action potential?
Relative Refractory Period
Pg. 078
What is occurring in the Relative Refractory Period?
There is a continued outward diffusion of K+
Pg. 079
What happens as a result of the continued outward diffusion of K+ that occurs in the Relative Refractory Period?
It causes the membrane potential to decrease below the RMP and hyperpolarize for a moment.
Pg. 079
What does the Refractory Period of an action potential prevent?
Prevents action potentials from adding together (summate) or running together continuously
and
Prevents action potentials from backtracking
Pg. 078-079
What are important consequences of the inabilities of action potential’s to run together and to summate?
Action potentials remain separate, all-or-none events that are able to code for the strength of a stimulus by their frequency of firing.
Pg. 079
What is an important consequence of the inability an action potential has to backtrack?
It means the action potential produced in the axon hillock travels towards the axon terminal not away from.
Pg. 079
True or False. Action potentials are not regenerated along the axon.
False. Action potentials are regenerated along the axon.
Pg. 079
Is it correct to say action potentials are conducted along the length of an axon?
No. Action potentials are regenerated along the length of the axon.
Pg. 079
What does it mean for action potentials to be conducted without decrement?
They do not decrease in amplitude as they are regenerated along the axon from the axon hillock to the axon terminals.
Pg. 079
What is meant by an action potential being a local event?
An action potential occurs only in the small stimulated region of the axon membrane, not in the entire axon.
Pg. 079
What is an important result of action potentials being local events?
It results in a potential difference between the stimulated region of the axon and the adjacent un-stimulated region.
Pg. 079
What are important consequences of resultant potential differences caused by action potentials being local events?
1) Movements of charges can depolarize the next region along the axon.
2) In unmyelinated axons movement of charges are able to bring the immediately adjacent plasma membrane’s region to a threshold depolarization.
3) These above events are able to repeat from the axon’s first segment to the last.
Pg. 079
How does conduction of action potentials in myelinated axons differ from unmyelinated axons?
Myelinated axons can produce action potentials only at the Nodes of Ranvier.
Pg. 079
What is the process that produces action potentials in myelinated axons called?
Salutatory Conduction
Pg. 080
What are some consequences of Salutatory Conduction?
1) Action potentials seem to jump from node to node
2) Each node must be depolarized to threshold by an action potential produced at the previous node
3) A myelinated axon reproduces the action potential fewer times than an unmyelinated axon would in an axon of equal length.
Pg. 080
Which type of axon has a faster conduction of action potentials?
Myelinated axons
Pg. 080
What can a deficiency of Ca2+ called and what does this condition cause?
Hypocalcemia
It decreases the threshold of excitation of neurons by increasing the permeability of sodium channels, causing them to have repetitive responses to a single stimulus.
Pg. 080
What does Hypocalcemia in the interstitial fluid impede?
It impedes the normal release of Acetylcholine by the axon terminal of the neuromuscular junctions, and inhibits muscle stimulation.
Pg. 080
What does Hypocalcemia consequently lead to?
Paresthesia (tingling)
Tetany
and
Psychiatric disorders in children
Pg. 080
How can Hypocalcemia cause inhibit muscle stimulation but still cause tetany?
Because the increased neuronal excitability overrides the inhibition of muscle contraction.
Pg. 080