Chapter 11: Functional Organization of nervous tissue
Place the events of a chemical synapse in chronological order, starting with the first at the top.
1. An action potential reaches the presynaptic terminal 2. Voltage-Gated Ca++ channels open 3. Ca++ diffuses into the presynaptic terminal 4. Neurotransmitters are released into the synaptic cleft 5. Neurotransmitters bind to receptors on the postsynaptic membrane 6. Depolarization or hyperpolarization of the postsynaptic membrane occurs
Place in order the events of the propagation of an action potential in a myelinated axon. Start with the generation of an action potential.
1. An initial action potential is generated 2. Local currents are generated 3. Local currents flow to the next node of Ranvier 4. Local currents promote depolarization 5. Threshold is reached in the membrane 6. The next action potential is generated
Place the following structures in the order that an electrical impulse would travel beginning with the postsynaptic membrane.
1. Dendrites 2. Soma 3. Axon Hillock 4. Axon 5. Presynaptic terminals
Place the events of action potential propagation in an unmyelinated axon.
1. Generation of an initial action potential 2. Generation of a local current in membrane adjacent to initial action potential 3. Plasma membrane adjacent to initial action potential depolarizes 4. Plasma membrane reaches threshold 5. Generation of next action potential
Place the events that occur in the propagation of an action potential in an unmyelinated axon.
1. Initial action potential produced at a trigger zone 2. Action potential generates local currents 3. Depolarization of adjacent areas of the membrane 4. Threshold reached in adjacent areas of the membrane 5. New action potential produced
What is the name of the gaps found between segments of myelin along an axon?
Nodes of Ranvier
Explain why the propagation of action potentials occurs in one direction.
The absolute refractory period prevents the generation of an action potential in the reverse direction.
As a result of calcium ions diffusing into the presynaptic cell,
acetylcholine is actively transported from the presynaptic neuron.
Acetylcholine is broken down by the enzyme called
acetylcholinesterase or AChE
Electrical signals that are propagated along axons in a non-decremental fashion are called__________ potentials.
action
The electrical signals that are propagated along axons, regulating and coordinating body activities, are known as _____.
action potentials
The nervous system transfers information from one part of the body to another by using _____.
action potentials
Traveling waves of excitation moving down an axon are referred to as ______.
action potentials
The sensory division is also known as the ________ division of the nervous system.
afferent
The sensory division is synonymous with the _____ division of the nervous system.
afferent
Identify the descriptor that is NOT a structural type of neuron.
afferent neuron
The division of the peripheral nervous system that transmits electrical impulses from sensory receptors to the CNS is the ______ division, while the ______ division of the peripheral nervous system transmits electrical impulses from the CNS toward muscles and glands.
afferent, efferent
On neurons, the process that is cylindrical and relatively unbranched is called a(n)
axon
The process on a neuron that is cylindrical and relatively unbranched is called a(n) ______.
axon
Nerve fibers are also called ____________.
axons
Within a chemical synapse, the receptors _____.
bind to very specific ligands
A molecule such as a neurotransmitter or a hormone that _____ is called a(n) ligand.
binds to a receptor
Glial cells that are directly involved in defending the CNS against infection and injury include _____________.
both astrocytes and microglial cells
Which organs make up the central nervous system?
brain and spinal cord
The central nervous system consists of the ___________, which is found within the skull, and the_________ ________ , which is found within the vertebral column.
brain, spinal, cord
The function of acetylcholinesterase is to ______.
break down the neurotransmitter acetylcholine
The peripheral nervous system includes the __________.
cranial nerves
The somatic and autonomic nervous systems are subdivisions of the ______.
efferent division
Synapses in which gap junctions allow ions to diffuse quickly from cell to cell are called ______ synapses.
electrical
Gap junctions allow direct communication or ionic flow between adjacent cells for a(n) ______ synapse, while synapses that use neurotransmitters to signal from the presynaptic to postsynaptic cell are called _______ synapses.
electrical, chemical
Cerebrospinal fluid is produced by ____________ cells.
ependymal
A partial depolarization of a postsynaptic neuron or muscle cell in response to a neurotransmitter is a(n) ______ postsynaptic potential.
excitatory
Depolarization of a postsynaptic neuron in response to a neurotransmitter is called an ________ postsynaptic potential.
excitatory
The entry of calcium into the synaptic knob triggers ______.
exocytosis of neurotransmitter
Inhibitory postsynaptic potentials involve ______ of the plasma membrane.
hyperpolarization
The membrane potential actually dips lower than -70mV because the potassium channels do not close quickly enough. This phase is called ____________ .
hyperpolarization
A specific molecule binds to a membrane receptor. This molecule is called a ______.
ligand
Neurotransmitter receptors at the postsynaptic membrane act as ___________ regulated ion gates.
ligand
Myelin consists of protein and large amounts of ____________ , giving heavily myelinated tissue a white appearance.
lipid
Myelin has a high ______ concentration.
lipid
____________ are glial cells that are macrophages.
microglia
The nervous system
monitors internal and external stimuli. transmits information in the form of action potentials. interprets or assesses information. maintains homeostasis.
A depolarizing local potential will make the neuron ______ likely to generate a nerve impulse.
more
An excitatory local potential will make the neuron ______ likely to generate a nerve impulse.
more
Depolarization occurs because
more sodium ions diffuse into the cell than potassium ions diffuse out of it.
The peripheral nervous system is further subdivided into an afferent (sensory) division and an efferent (________) division.
motor
Presynaptic inhibition ______ the amount of neurotransmitter released from the presynaptic terminal.
reduces
When one presynaptic neuron _____ the amount of neurotransmitter released from another presynaptic neuron, it is called presynaptic inhibition.
reduces
The role of the Na+-K+ pump in membrane potential regulation is that it ______.
reestablishes correct ion distribution, compensating for ion leakage
A period of time after a nerve cell has responded to a stimulus in which it cannot be re-excited by a threshold stimulus is called a(n) ______ period.
refractory
As cations leave the cell, the membrane potential at that part of the membrane once again becomes negative. This phase of the action potential is called ____________ , because the resting membrane potential is being reestablished.
repolarization
The difference in electrical charge across the plasma membrane in an unstimulated cell is called the __________ ___________ potential
resting membrane
A cell is not stimulated but it does contain an electrical charge difference across its membrane. This charge difference is its _________
resting membrane potential
Identify all of the bases for neuron classification.
structure function
A junction between a neuron and another cell is called a(n)
synapse
The small, membrane-bound organelles that are found in the presynaptic terminals and which contain neurotransmitters are called ____
synaptic vesicles
The somatic nervous system is the sub-division of the efferent division that transmits electrical impulses from _____.
the CNS towards skeletal muscle
When threshold is reached, depolarization of the same magnitude occurs for all action potentials. If threshold is not reached, an action potential does not begin at all. This describes
the all-or-none law
For each ATP molecule used, the sodium-potassium pump transports
two K+ into the cell and three Na+ out of the cell.
An action potential arriving at the presynaptic terminal causes
voltage-gated calcium ion channels to open, and calcium ions to diffuse into the cell.
As the peak of the action potential is reached, the sodium channels close and the ____________ open, allowing these ions to diffuse out of the cell.
voltage-gated potassium channels
When threshold is reached, ____________ of the initial segment open briefly, allowing ____________ to diffuse into the cell.
voltage-gated sodium channels, sodium
The neuron plasma membrane is approximately _____ times more permeable to potassium ions than to sodium ions.
50-100
What is produced when depolarization of a cell membrane reaches threshold?
A new action potential is produced.
Match the parts of a neuron with the appropriate description.
Axon: Process of a neuron that transmits action potentials away from the cell body Dendrite: Process of a neuron that transmits action potentials towards the cell body Collaterals: Branches of an axon Presynaptic terminal: Enlarged end of axon containing vesicles filled with neurotransmitters Axon hillock: Site where the axon originates
Select the components of the central nervous system.
Brain and Spinal cord
Which items are continuous with each other at the foramen magnum?
Brain and spinal cord
Correctly pair the parts of a neuron with the correct description.
Cell body: Enlarged portion of a neuron that contains the nucleus and other organelles Axon: Process of a neuron that transmits action potentials away from the cell body Dendrite: Process of a neuron that receives stimuli and and generates local potentials Nissl body: Rough endoplasmic reticulum of a neuron responsible for protein synthesis Collaterals: Branches of an axon
Match each division of the nervous system with the correct description.
Central Nervous System: Consists of the brain and spinal cord Peripheral Nervous System: Consists of sensory receptors, nerves, ganglia and plexuses. Autonomic Nervous System: Consists of the sympathetic and parasympathetic divisions Somatic Nervous System: Division of the efferent division that is mostly under voluntary control Afferent Division: Also referred to as the sensory division of the PNS Efferent Division: Also referred to as the motor division of the PNS Enteric Nervous System: Independent sub-division that controls the digestive tract
Correctly match each division of the nervous system with its description.
Central Nervous System: Processes information, initiates responses and integrates mental processes Peripheral Nervous System: Detects stimuli and transmits information to and receives information from the CNS Autonomic Nervous System: Transmits information to cardiac muscle, smooth muscle and glands. Somatic Nervous System: Transmits information to skeletal muscle Afferent Division: Transmits information from receptors to the CNS Efferent Division: Transmits information from the CNS to muscles and glands Enteric Nervous System: Independent sub-division that controls the digestive tract
Identify the mechanisms by which neuromodulators alter synaptic transmission. Select all that apply.
Changing neurotransmitter receptor numbers Affecting the removal of neurotransmitters Affecting breakdown of neurotransmitters
Pair the neuronal pathways and circuits to the correct definition.
Convergent pathway: A pathway where several neurons synapse with a smaller number of neurons Divergent pathway: A pathway where a small number of neurons synapse with a larger number of neurons Oscillating circuit: Neurons arranged in a circular fashion that are repeatedly stimulated to produce action potentials
Match the neuronal pathways and circuits with the correct function.
Convergent pathway: Pathways that allow different parts of the nervous system to affect the activity of a neuron. Divergent pathway: Pathways that allow one part of the nervous system to affect more than one part of the nervous system. Reverberating circuit: Important in functions that are periodically active such as the sleep/wake cycle and respiration.
Match the type of synapse with the correct description.
Electrical synapse: A gap junction that allows an ionic current to flow between adjacent cells Chemical synapse: A synapse where one cell releases a neurotransmitter to communicate with another cell
Any two EPSPs will override one IPSP.
False
Gray matter consists of bundles of myelinated axons.
False
True or false: During the absolute refractory period a neuron will be re-stimulated if it reaches threshold.
False
True or false: Neurons consist of a cell body, a single dendrite and multiple axons.
False
True or false: Summation of all incoming signals occurs at the axon terminus of a neuron.
False
True or false: When a neurotransmitter binds to a receptor on a postsynaptic membrane, a depolarization will always occur.
False
Identify the components of the peripheral nervous system. Select all that apply.
Ganglia Sensory receptors nerves
____________ ion channels are closed until opened by specific signals.
Gated
_____ potentials are conducted in a decremental fashion, while ____ potentials are conducted with a constant magnitude.
Graded, action
_____ occurs when the inside of the plasma membrane becomes more negative, and ______ occurs when the inside of the plasma membrane becomes less negative.
Hyperpolarization, depolarization
Which of the following is NOT one of the phases of an action potential?
Hyperpotential
Explain how the neurotransmitter acetylcholine is removed from the synaptic cleft.
It is broken down by the enzyme acetylcholinesterase.
What is the nature of the signal that propagates along neurons that ultimately regulates and coordinates the functions of the body?
It is electrical
What effect will a neurotransmitter have on the postsynaptic membrane?
It may produce a depolarization or a hyperpolarization.
____________ ion channels are always open and are responsible for the permeability of the plasma membrane to ions when the plasma membrane is unstimulated.
Leak
Identify the structural types of neurons. Select all that apply.
Multipolar neuron Bipolar neuron Pseudo-unipolar
Select the item that is NOT a component of a neuron.
Myelin
These cells, wrapped repeatedly around the axon, form a coating called a ____________ . It consists of multiple layers of the ____________ of the neuroglia cells.
Myelin sheath, cell membrane
When Na+ channels open, what happens to the Na+ ions?
Na+ diffuses into the cell
Explain why Na+ ions diffuse into the neuron when the Na+ channels open.
Na+ is more concentrated outside the cell than inside; hence, the concentration gradient causes diffusion into the cell.
A compound that alters synaptic transmission or alters the action of a neurotransmitter is called a(n) __________
Neuromodulator
Describe characteristics of receptors at the synapses. Select all that apply.
Only specific molecules are able to bind to the receptors They are ligand activated receptors
Identify the correct sequence of information in a chemical synapse.
Presynaptic terminal, synaptic cleft, postsynaptic membrane
____________ cannot cross the plasma membrane because they are too large to fit through the leak ion channels.
Proteins
Identify the phases of an action potential. Select all that apply.
Repolarization Depolarization Afterpotential
Axons of the peripheral nervous system are associated with neuroglia cells called ____________ .
Schwann cells
Choose the neuroglial cell types found in the peripheral nervous system.
Schwann cells Satellite cells
The sodium-potassium pump moves the ions in which direction?
Sodium out of the cell and potassium into the cell
Correctly match the parts of a neuron with the correct description.
Soma: Also known as the cell body Nissl body: Rough endoplasmic reticulum of a neuron responsible for protein synthesis Collaterals: Branches of an axon Presynaptic terminal: Enlarged end of axon containing vesicles filled with neurotransmitters Axoplasm: Cytoplasm of an axon
What are the divisions of the motor division of the peripheral nervous system?
Somatic and autonomic
Which term best describes the concentration gradients for sodium and potassium on an excitable cell?
Steep
The efferent or motor division transmits impulses from ____________ .
The CNS to peripheral organs
Select the item that best defines the soma of a neuron.
The cell body of a neuron
Differentiate graded potentials and action potentials. Select all that apply.
The magnitude of graded potentials is variable and action potentials are all-or-none. Graded potentials are conducted in a decremental fashion and action potentials are conducted with a constant magnitude.
Identify the characteristics of action potentials. Select all that apply.
The strength of the stimulus determines the frequency of the action potentials. They are all-or-none. They are propagated in a non-decremental fashion.
As the strength of a stimulus increases, what will happen to action potentials?
They will be produced with increasing frequency
An action potential will not occur unless the membrane potential at the ____________ (the initial segment of the axon) reaches a level called ____________ .
Trigger zone, threshold
True or False: Inhibitory postsynaptic potentials (IPSPs) involve hyperpolarization of the plasma membrane.
True
True or False: The nervous system and the endocrine system are the major control systems of the body.
True
True or false: The potential difference is caused by a difference in concentration of charged particles on either side of the cell membrane.
True
True or false: There is a significant difference in concentration between the intracellular concentration of sodium and the extracellular concentration of sodium.
True
Glands, smooth muscles, and cardiac muscles are innervated by the ______ division of the motor nervous system.
autonomic
The division of the motor nervous system that is under involuntary control and innervates glands, smooth muscle, and cardiac muscle is the ______ division.
autonomic
The division of the nervous system that transmits electrical impulses toward cardiac muscle, smooth muscle, and glands is the ______ nervous system, whereas the division of the nervous system that transmits electrical impulses toward skeletal muscle is the ______ nervous system.
autonomic, somatic
Entry of ______ ions into the synaptic knob triggers exocytosis of neurotransmitters.
calcium
The division of the nervous system that is responsible for processing, integrating, storing and responding to information is the _________ nervous system.
central
The division of the nervous system that is the key decision maker of the body is the ______ nervous system.
central
The brain and spinal cord are the two components of the ______.
central nervous system
The nervous system is divided into the ______ nervous system, which includes the _____ and spinal cord, and the________ nervous system, which includes cranial nerves, spinal nerves, and ganglia.
central, brain, peripheral
The ______ are the two major subdivisions of the nervous system.
central, peripheral
The two major subdivisions of the nervous system are the ____________and the ________________ nervous systems.
central, peripheral
Identify the type of synapse that includes a presynaptic cell, synaptic cleft, and postsynaptic cell.
chemical
Synapses in which neurotransmitters are released are called ______ synapses.
chemical
Inhibitory postsynaptic potentials are due to the opening of ______ channels.
chloride or potassium
Due to the action of AChE, the neurotransmitter acetylcholine is broken down into
choline and acetic acid
Branched cytoplasmic extensions of the neuron that receive input and transmit signals toward the cell body are
dendrites
The highly branched cytoplasmic extensions of a neuron cell body that are specialized to receive input and conduct signals toward the cell body are called ______.
dendrites
____________ are processes that conduct electric signals toward the cell body.
dendrites
As these ions enter the cell, the cell membrane undergoes ____________ , with the membrane potential increasing to a peak of approximately +30mV.
depolarization
When the resting membrane potential shifts to a more positive value, this is referred to as
depolarization
The membrane potential becoming more positive in value is called __________ whereas, __________ refers to the membrane potential becoming more negative than the resting membrane potential.
depolarization,hyperpolarization
The term "potential difference" refers to the ______.
difference in electrical charge across the plasma membrane
The motor division is also known as the _______division of the nervous system.
efferent
The motor division is synonymous with the _____ division of the nervous system.
efferent
A hole which allows the brain and spinal cord to be continuous with one another is the ____________ ______________
foramen magnum
Increasing stimulus strength results in an increase in the ______ of action potentials.
frequency
Neurons are classified by which of the following?
function or structure
A group of related nerve cell bodies are outside of the central nervous system. The group is called a _____.
ganglia
Groups of related nerve cell bodies located outside of the central nervous system are called
ganglia
Electrical synapses allow ions to diffuse quickly from cell to cell via ______.
gap junctions
A protein channel that opens or closes in response to a stimulus would be classified as a ______ channel.
gated
Some protein channels in a cellular membrane are able to open or close in response to stimuli; because of this characteristic, these channels are called ______ channels.
gated
Supporting cells such as oligodendrocytes and ependymal cells are examples of ______ cells.
glia
There are several types of support cells within the nervous system. As a group, these support cells are called ______ cells
glial
The cells that account for over half of the brain's weight and outnumber neurons by at least 10 times are called cells.
glial cells
Which cell type accounts for over half of the brain's weight and outnumbers neurons by 10 to 50 times?
glial cells
Hyperpolarization of a postsynaptic neuron in response to a neurotransmitter is called an __________ postsynaptic potential.
inhibitory
An IPSP causes an ______ on its target membrane.
inhibitory postsynaptic potential
As the cells wrap around and around the axon, cytoplasm ends up in the outermost wrapping of the cell. Because myelin is nonpolar, it prevents ions from accessing the axon surface, serving as an electrical ____________ to the axon.
insulator
A synapse is a ______.
junction between two cells
A hyperpolarizing local potential will make the neuron ______ likely to generate a nerve impulse.
less
An inhibitory local potential will make the neuron ______ likely to generate a nerve impulse.
less
When the membrane potential decreases, the inside of the membrane becomes _____ negative. This is called ______.
less, depolarization
Action potentials are conducted more rapidly along ______ axons.
myelinated
Action potentials are conducted more rapidly along ______ axons.
myleinated
When the resting membrane potential becomes more _____ the condition is referred to as hyperpolarization.
negative
The two major control systems in the body are the ______ system and the ______ system.
nervous, endocrine
A compound that alters synaptic transmission is called a(n) ______.
neuromodulator
Compounds classified as ______ alter synaptic transmission by changing neurotransmitter receptor numbers or affecting the breakdown and/or removal of neurotransmitter.
neuromodulators
A cell that receives stimuli and transmits action potentials to other nerve cells or effector organs is a(n)
neuron
A cell that receives stimuli and transmits action potentials to other nerve cells or effector organs is a(n) ____________.
neuron
The structural unit of the nervous system that consists of a cell body, dendrites, and an axon is the ______.
neuron
The general types of cells that make up the nervous system are ____________and__________ cells.
neuron, glial
Select all of the cell types that are components of the nervous system.
neuron, glial cells
Ligand-gated ion channels bind ______ that have diffused across a synaptic cleft.
neurotransmitters
Synaptic vesicles within synaptic knobs contain chemicals called
neurotransmitters
Synaptic vesicles within synaptic knobs contain chemicals called _________
neurotransmitters
What substance fills synaptic vesicles?
neurotransmitters
The intracellular fluid has essentially the same number of positive and negative charges and is therefore electrically ______
neutral or balanced
The gaps found between Schwann cells forming the myelin are referred to as the _________ of __________.
node, Ranvier
Gaps between neighboring segments of the myelin sheath are called ____________ . At these points, the axon is not insulated.
nodes of ranvier
All of the nervous tissue outside the central nervous system is categorized as belonging to the ______ nervous system.
peripheral
Schwann cells and satellite cells are examples of neuroglial cells in the ______ nervous system.
peripheral
The sensory and motor divisions are the two functional sub-divisions of the ______ nervous system.
peripheral
The subdivision of the nervous system that consists of nerve tissue external to the central nervous system is the nervous system.
peripheral
The subdivision of the nervous system that is responsible for detecting stimuli in and around the body and sending that information to the central nervous system is the ______.
peripheral nervous system
The afferent or sensory division transmits impulses from ____________ .
peripheral organs to the CNS
Myelin has a high lipid content because it is formed of ______.
plasma membranes
A higher concentration of ____________ ions can be found on the inside of the plasma membrane.
potassium
The neuron plasma membrane is 50-100 times more permeable to _____ than to sodium.
potassium
Inhibitory postsynaptic potentials are due to the opening of ______ channels. Select all that apply.
potassium chloride
When a charge difference exists across the plasma membrane, this difference is referred to as the membrane _________
potential
The ____________ of a neuron release(s) neurotransmitters.
presynaptic terminals
The purpose of the absolute refractory period is to _____.
prevent action potentials from being generated in reverse direction
Propagation of an action potential down a myelinated axon requires that the action potential "jumps" from node to node in a process called ______ conduction.
saltatory
The propagation of action potentials from one node of Ranvier to another along a myelinated axon is called ______ conduction.
saltatory
The plasma membrane is ____________ permeable and allows some, but not all, substances to pass through it.
selectively
Most pseudo-unipolar neurons are ____________ neurons.
sensory
The neurons that conduct information towards the CNS are _________.
sensory neurons
List the components of the peripheral nervous system.
sensory receptors and nerves
The division of the peripheral nervous system that transmits electrical impulses from _____ to the _____ is the afferent division.
sensory receptors, central nervous system
Identify the two functional sub-divisions of the peripheral nervous system.
sensory, motor
The motor division is divided further into a somatic motor division serving ____________ muscle and a/an ____________ motor division serving ____________ muscle, cardiac muscle, and glands.
skeletal, autonomic, smooth
An unmyelinated axon will conduct action potentials more ______ than a myelinated axon.
slowly
A higher concentration of ____________ ions can be found on the outside of the plasma membrane.
sodium
During an EPSP, an influx of ______ occurs.
sodium
During an action potential of a neuron, the type of ion that enters the cell and causes depolarization is the _________ ion.
sodium
Excitatory postsynaptic potentials are due to the entry of the electrolyte ________ through gated ion channels in the postsynaptic membrane.
sodium
During an action potential, depolarization is due to ______ ions _____ the cell.
sodium, entering
The concentration of __________ ions is much greater outside the cell as compared to inside the cell, whereas the concentration of ____________ ions is much greater inside the cell as compared to outside the cell.
sodium, potassium
The cell body of a neuron is also known as the ________
soma
The division of the peripheral nervous system that includes efferent fibers to skeletal muscles is the _____ division.
somatic
The division of the nervous system that transmits electrical impulses toward skeletal muscle is the__________ nervous system, whereas the division of the nervous system that transmits electrical impulses toward cardiac muscle, smooth muscle, and glands is the _________nervous system.
somatic autonomic
The __________ nervous system communicates with the skeletal muscles and the __________ nervous system communicates with the smooth and cardiac muscle as well as glands.
somatic, autonomic
The motor divisions of the peripheral nervous system is further divided into the ______ and ______ subdivisions.
somatic, autonomic
The central nervous system includes the __________.
spinal cord
Hyperpolarization, or afterpotential, occurs because
the increased potassium ion permeability lasts slightly longer than the time required to bring the membrane potential back to its resting level.
The intracellular fluid is considered to be electrically neutral because ______.
there are the same number of positively and negatively charged ions.
Within a neuron, summation of all incoming signals occurs at the ______.
trigger zone
