Nervous System
Trace the direction of flow of electrical activity through a neuron, starting with the arrival of a signal at a dendrite
1. Dendrite 2. Cell body 3. Axon Hillock 4. Axon 5. Axon Terminal 6. Synaptic knob 7. Signal transmitted across synapse
Indicate three general functions of neuroglia.
1. Provide structural support of neurons. 2. Carry out phagocytosis. 3. Produce components of myelin.
Identify three functions of neuroglial cells.
1. guide neurons into position during embryogenesis 2. Remove excess ions and neurotransmitters from areas surrounding neurons. 3. produce growth factors for neurons
1. Sensory (afferent) neuron 2. motor (efferent) neuron 3. interneuron
1. located in PNS; carries impulses towards CNS 2. Located in PNS; carries impulses away from the CNS 3. Located in the CNS; integrates sensory signals
1. monoamines 2. amino acids 3. neuropeptides
1. norepinephrine 2. GABA 3. Endorphins
1. monoamines 2. amino acids 3. neuropeptides
1. serotonin 2. glycine 3. enkephalins
Match the function of the nervous system with the component that carries it out. 1. Sensory Input 2. Integration and Processing 3. Motor Output
1.Receptor 2.Brain and Spinal Cord 3. Effector
What is a neuronal pool?
A neuronal pool is a group of neurons within the CNS that synapse with each other and perform a common function, even though their cell bodies may be located in different parts of the CNS
Explain the function of a neurotransmitter
A neurotransmitter is the chemical released by presynaptic neuron in the process of synaptic transmission, to transfer information from one cell to another. IT binds to receptors on the postsynaptic neuron and results in either and EPSP or and IPSP on the postsynaptic neuron at the synapse
What is the effect of a neuromodulator?
Alters response of neuron to a neurotransmitter
Describe the net effects of EPSPs and IPSPs
An EPSP makes it more likely that an action potential will occur, by making the inside of the membrane less negative. An IPSP makes it less likely that an action potential will occur, by making the membrane more negative. Typically, postsynaptic neurons receive synaptic input from many presynaptic neurons. If the net effect is more excitatory than inhibitory, threshold may be reached and an action potential triggered. If the net effect is more inhibitory than excitatory an action potential will not occur
List the major events of an action potential
An action potential is an electrical sequence of events that is propagated down an axon as a nerve impulse. First, Na+ channels open, often in response to a neurtransmitter and NA+ ions enter the neuron, making the inside of the neuron less negative; this is called depolarization. The neuron responds by opening K+ channels; K+ ions then diffuse out of the cell, restoring the more negative charge inside the cell; this is called repolarization. After this, the membrane is returned to its resting state by the NA+/K+ pump, which restores the original concentrations of the ions on both sides of the membrane
Distinguish between an EPSP and IPSP
An excitatory postsynaptic potential, or EPSP, occurs when neurotransmitters released by a presynaptic neuron cause a postsynaptic neuron's membrane potential to move closer to the threshold. AN EPSP may or may not result in an action potential. An inhibitory postsynaptic potential, or IPSP, occurs when the membrane potential is made to move father from the threshold potential, making an action potential less likely to occur
Found Between neurons and blood vessels (blood-brain barrier); regulate ion concentration in nervous tissue
Astrocytes
The branch of the peripheral nervous system that controls cardiac muscle, smooth muscle, and glands are called the ____ nervous system
Autonomic
Name the specialized endings found at the end of an axon.
Axon Terminals
Identify the prefix that means "two".
Bi-
Cell body with a process arising from each end; one dendrite and one axon
Bipolar
Within neurons, dendrites are processes extending from the ______. They function to carry signals ______ the cell body.
Cell Body; toward
The genes in the nucleus of a neuron are the same as the genes in the nuclei of its schwann cells. What causes these cells to have such different form and function?
Cellular Differentiation
The two main divisions of the nervous system are the ______ and the _______.
Central and peripheral
Which are the two major divisions of the nervous system?
Central nervous system and peripheral nervous system
What is converegence?
Convergence is the synaptic connection of the axons of two or more neurons with the same postsynaptic neuron. In this process, axons from various parts of the nervous system can exert their influence on the same neuron, and the various effects can be summated
What is a function of the nervous system?
Coordinate all other body functions
The extension of a neuron that receives input is called a(n) ______.
Dendrite
what structure of a neuron is a short, highly branched process that helps receive input from other neurons?
Dendrite
Which three items are parts of a neuron?
Dendrites, Axon, and Cell Body
Which three items are parts of a neuron?
Dendrites, Cell Body, and Axon
What is divergence?
Divergence is the stimulation of two or more postsynaptic neurons by the axon terminals of a single neuron. In this process, the spread of an impulse from one neuron to several others allows amplification of the effects of the impulse
What results from the decomposition of neurotransmitter molecules or the reuptake of neurotransmitters from a synaptic cleft?
End of synaptic transmission
The class of neurotransmitters called neuropeptides include which neurotransmitter(s)
Enkephalins and substance P
Covers the choroid plexus; lines space in the brain (ventricles)
Ependymal cells
T/F Acetylcholine is actively transported across the synaptic cleft
False
T/F The occurrence of the refractory period allows and action potential to propagate along the axon in both directions
False
The region of a neuron where the axon originates is called the axon ______.
Hillock
The disease called multiple sclerosis involves an immune response against myelin of the central nervous system, causing scar formation (sclerosis) within the neural tissue. How would this affect nerve impulse conduction?
Impulses are blocked or interrupted
Explain how an axon in the peripheral nervous system becomes myelinated
In the PNS, neuroglia called Schwann cells encase axons of certain peripheral neurons in layers of cell membrane filled with a fatty material called myelin, to form myelin sheaths. A myelin sheath is an electrical insulator for myelinated axons
How is resting membrane potential achieved?
K + ions are in higher concentration inside of a neuron than outside, and NA+ ions are in higher concentration outside the neuron than inside. The negative charge inside of a neuron results mainly from a high concentration of negatively charged proteins, phosphate ions, and sulfate ions that are unable to cross the cell membrane. Although Na+ and K+ ions cross the cell membrane down their concentration gradients, the Na+/K+ pump returns the ions to their original locations and concentrations, to maintain the resting potential
The fastest impulse conduction would occur in what type of axon?
Large-diameter myelinated axon
Describe the effect of acetylcholine on the postsynaptic neuron
Ligand (chemically)-gated sodium channels open, and sodium diffuses into the postsynaptic neuron
What does it mean that neurons are excitable?
Local potential changes occur in the membrane due to changes in the surrounding area.
Phagocytes; supportive function
Microglia
Cell body with many processes; one axon and many dendrites
Multipolar
Some neuroglial cells produce the components of the electrical insulator called ______.
Myelin
What gives white matter of the central nervous system its white color?
Myelin
In what type of axon does saltatory conduction occur?
Myelinated axons
Thinking, learning, and regulating movement are functions of which organ system?
Nervous
Name two cell types in neural tissue
Neural tissue contains cells called neurons, which communicate with other cells through the conduction of electrical impulses, and neuroglia, which support, protect, insulate, and nourish neurons
Cells called ___ have a support function, though they may also send and receive impulses
Neuroglia
Describe a neuron
Neurons vary in size and shape, but each has a cell body, input processes called dendrites and an output process called an axon. Neuron may also be associated with certain neuroglia that form myelin
What is the effect of the binding of neurotransmitters to their receptors on the postsynaptic cell membrane?
Neurotransmitters are sometimes excitatory and sometimes inhibitory
The myelin sheath along an axon is not continuous. What are the gaps between Schwann cells called?
Nodes of Ranvier
The gaps between segments of myelin along an axon are called ______ of ______.
Nodes, Ranvier
What is a refractory period for a membrane?
Period of time after an action potential when the membrane cannot send another action potential.
What division of the nervous system consists of cranial and spinal nerves?
Peripheral Nervous system
Most cells are negatively charged on the inside but have a positively charged extracellular space outside. This difference in charges is called ______.
Polarity
The water molecule shows ______ because it has negatively-charged regions in the vicinity of the oxygen atom and positively-charged regions near the hydrogen atoms.
Polarity
The negative charge across a resting membrane is due to the more ____ ions diffusing out of the cell than ____ ions diffusing into the cell
Potassium; sodium
What are some functions of neuroglia?
Producing the myelin sheath around certain axons, provide structural and nutritional support for neurons, form scar tissue, perform phagocytosis, take up excess ions and neurotransmitters, exchange substances between blood vessels and neurons, support neuron regeneration (PNS), help with formation of cerebrospinal fluid (CNS), and help with the formation of synapses
List the general functions of the nervous system
Receives sensory information, detects changes, integrates and processes information for decision-making, and responds to these decisions; these are termed, respectively, the sensory, integrative, and motor functions. The nervous system is also responsible for thought processes, memory storage and learning
Define Facilitation
Repeated stimulation of an excitatory presynaptic neuron may cause it to release more neurotransmitter in response to one impulse, increasing the likelihood that a postsynaptic neuron will reach threshold; this is called "facilitation"
This figure illustrates ___ conduction along an axon. ( axon potential moving solely in the right direction)
Saltatory
The cells that are responsible for wrapping around axons, creating myelin sheaths in the PNS, are ______.
Schwann Cells
What is the source of myelin, found around large axons of the peripheral nervous system?
Schwann cell membranes tightly wound around axons.
In the peripheral nervous system, which type of neuroglial cell produces myelin?
Schwann cells
The cells that are responsible for wrapping around axons, creating myelin sheaths in the PNS, are ______.
Schwann cells
Which of the following are neuroglia found in the peripheral nervous system?
Schwann cells and satellite cells
Which type of neuron conducts impulses from peripheral body parts into the brain or spinal cord?
Sensory
Describe the flow of information in the nervous system
Sensory input flows from sensory receptors to the brain or spinal cord for integrating and processing, followed by motor output to an effector (or effectors) that elicits a response
What functions to detect changes inside and outside of the body?
Sensory receptors
Why is saltatory conduction along a myelinated axon faster than continuous conduction along an unmyelinated axon?
Since action potentials do not occur along with the areas of the axon membrane that are covered by myelin, myelinated axons have less membrane surface that will conduct the impulse
What occurs during depolarization of an axon?
Sodium channels open and sodium diffuses into the cell
Which organs make up the peripheral nervous system?
Spinal and Cranial
What organs make up the central nervous system?
Spinal cord and brain
The space between the synaptic knob of one neuron and the receptive surface of another is called the ______.
Synaptic Cleft
Describe a synaptic transmission
Synaptic transmission is the process by which an impulse in a presynaptic neuron transfers information to a postsynaptic cell. It involves a chemical neurotransmitter, released by the presynaptic cell, binding to receptors on the postsynaptic cell. This causes chemically-gates ion channels to open in the postsynaptic cell, creating a synaptic potential in that cell. AN uncommon type of synapse, called an electrical synapse, occurs in certain parts of the brain and eyes. This involves the direct exchange of ions through gap jxn. which alllows the information to be transferred to the postsynaptic cell
What happens after calcium channels open and calcium enters the synaptic knob
Synaptic vesicles migrate to the plasma membrane and release acetylcholine
During action potential, what change occurs first at the cell membrane
The area inside the neuron cell membrane becomes positively charged compared to the outside
Name two groups of nervous system organs
The organs of the nervous system are the central nervous system (brain and spinal cord) and the peripheral nervous system (peripheral nerves, including cranial nerves, spinal nerves, and ganglia)
Define refractory period
The refractory period is the short period of time during an action potential, during which a threshold stimulus cannot generate another action potential. This limits the frequency of action potentials and sends nerve impulses in only one direction along the axon
Which two characteristics apply to cells called interneurons (or association neurons)?
They are multipolar neurons. They link sensory neurons to motor neurons.
T/F If the postsynaptic membrane potential reaches threshold level, and action potential will be produced
True
Cell body with a single process that divides into two branches
Unipolar
Explain how impulse conduction differs in myelinated and unmyelinated axons
Unmyelinated neurons conduct impulses continuously down the entire surface of their axons. Myelinated neurons conduct impulses by a process called saltatory conduction. Since NA+ and K+ ions can only cross the cell membrane of the axon at the nodes of Ranvier, action potentials only occur at the nodes. The action potential "jumps" down the axon from node to node; this occurs much more quickly that continuous propagation
An action potential traveling down the presynaptic neuron reaches the synaptic knob. What initially occurs at the synaptic knob when that action potential arrives?
Voltage-gated calcium ion channels open, and calcium ions diffuse into the synaptic knob
Within the brain and spinal cord, myelinated axons provide the color for _______matter.
White
saltator-
a dancer: saltatory conduction- impulse conduction in which the impulse seems to jump from node to node along the axon
Define Neuropeptide
a neuropeptide is a short chains of amino acids, which can function as a neurotransmitter, which functions in synaptic transmission or a neuromodulator, which changes a neuron's response to a neurotransmitter or blocks release of a neurotransmitter
The neurotransmitter released at neuromuscular junctions, stimulating skeletal muscle contraction, is
acetylcholine
Which neurotransmitter is responsible for skeletal muscle contraction?
acetylcholine
peri-
all around: peripheral nervous system- portion of the nervous system that consists of the nerves branching from the brain and spinal cord
As an action potential occurs in one area of the axon, an electrical current to neighboring areas of the membrane initiates ______.
another action potential
Microglia
are tiny cells that perform phagocytosis of bacteria and debris
Where are axon terminals located?
at the ends of axons
ax-
axle: axon-cylindrical process that conducts impulses away from a neuron cell body
Hillocks, collaterals, and terminals are associated with what part of a neuron?
axon
A neuron has only one ______ , but can have many ______
axon, dendrites
Where is a synaptic cleft located?
between a synaptic knob and another cell
What will trigger the opening of chemically gated ion channels?
binding of neurotransmitter molecules
Ependymal
cells produce cerebrospinal fluid, which cushions and nourishes neurons, and also helps maintain the blood-brain barrier.
Structures called tracts are bundles of axons occurring within the ______ nervous system.
central
Neurotransmitters bind to ion channels that are ______-gated ion channels.
chemically
What type of process is typically more abundant in a neuron?
dendrite
Within a neuron, the _____ are highly branched cellular processes that carry signals toward the cell body of the neuron.
dendrites
Neurons include cell bodies and cell processes called ___ and ____
dendrites and axons
An action potential generates local currents that cause ____ of the membrane immediately adjacent to the action potential
depolarization
A cell membrane is ______ if its membrane potential becomes less negative (more positive) than the resting potential.
depolarized
Indicate the four types of neuroglia (glial cells) in the central nervous system.
ependymal cells astrocytes microglia oligodendrocytes
Neurons are ______, meaning they respond to changes in their surroundings with changes in their membrane potential.
excitable
An ______ postsynaptic potential involves the opening of sodium channels, depolarizing the membrane, and bringing it closer to a threshold level.
excitatory
sens-
feeling: sensory neuron- neuron that can be stimulated by a sensory receptor and conducts impulses into the brain or spinal cord
oligo-
few: oligodendrocyte-small type of neuroglia with few cellular processes
Sensory neurons conduct impulses in which direction?
from the peripheral body parts to the brain and spinal cord
Which cells lie entirely within the brain or spinal cord and form links between other neurons in the central nervous system?
interneurons
Neurons that are functionally classified as _______ (neurons) are those that form links between other neurons within the CNS.
interneurons, association, internuncial, or inter
Neurons that are functionally classified as________(neurons) are those that form links between other neurons within the CNS.
interneurons, association, internuncial, or inter
When depolarization occurs, the resting membrane potential becomes ______ negative and ______ 0mV.
less; closer to
multi-
many: multipolar neuron- neuron with many processes extending from the cell body
A charge inside of a cell, indicating that there is the possibility that charges will move across the cell membrane, is called ______.
membrane potential
Which term indicates that charges have the capability of moving across the cell membrane, creating an electric current?
membrane potential
4 types of neuroglia of the CNS are:
microglia, oligodendrocytes, astrocytes, and ependymal cells.
moto-
moving: motor neuron- neuron that stimulates a muscle to contract or a gland to release a secretion
Oligodendrocytes form ______ in the central nervous system.
myelin sheaths
What is the name for bundles of axons found within the peripheral nervous system?
nerves
Within the peripheral nervous system, bundles of axons wrapped in connective tissue form structures called _____
nerves
Within the peripheral nervous system, bundles of axons wrapped in connective tissue form structures called _______.
nerves
Astrocytes, oligodendrocytes, microglia, and ependymal cells are types of ______ found in the ______.
neuroglia; CNS
Schwann cells and satellite cells are types of ______ found in the ______ nervous system.
neuroglia; peripheral
A molecule acting as a(n) _____ will alter the release of neurotransmitters or alter the response of the postsynaptic neuron to the neurotransmitter.
neuromodulator
Dendrites are branches off of the ______ that function to ______.
neuron cell body; receive incoming signals
Cells called ________ are specialized to send and receive nerve impulses
neurons
The action of a ____ depends on the receptors at a particular synapse.
neurotransmitter
What is synthesized in the cytoplasm of the synaptic knob and stored in synaptic vesicles?
neurotransmitters
What is the name of the gaps found between segments of myelin along an axon?
nodes of Ranvier
The cell membrane of a neuron has both gated and non-gated ion channels. Which type of non-gates channel is more abundant
non-gated potassium channels
Form Myelin in CNS
oligodendrocytes
Name the type of neuroglia that provides insulating layers of myelin (myelin sheath) in the brain and spinal cord.
oligodendrocytes
Uni-
one: unipolar- neuron with only one process extending from the cell body
In which branch of the nervous system do the Schwann cells wrap around axons creating myelin sheaths?
peripheral nervous system
Oligodendrocytes
produce the myelin sheath around CNS axons, to increase conduction speed of nerve impulses.
Schwan cells
produce the myelin sheath around some peripheral axons, to increase conduction speed of nerve impulses.
A(n) _______ period is a brief time following a nerve impulse when the membrane is unresponsive to an ordinary stimulus.
refractory
Astrocytes
regulate nutrient and ion levels in neurons, and maintain the blood-brain barrier
-lemm
rind or peel: neurilemma- sheath that surrounds the myelin of a nerve cell process
2 types of neuroglia in the PNS
schwann cells and satelllite cells
Nerve impulses are conducted via the ______ neurons from peripheral body parts into the brain and spinal cord.
sensory or afferent
Neurons carrying nerve impulses toward the CNS are _______ , neurons while neurons carrying nerve impulses from the CNS to the periphery are _____ neurons.
sensory, motor or afferent, efferent
An excitatory postsynaptic potential (EPSP) occurs when neurotransmitters bind to their receptors and open chemically-gated ______ channels.
sodium
This figure shows a membrane at rest, during depolarization, and during repolarization. Note the pink and purple circles. These represent ions involved in the depolarization/repolarization process. What ion is represented by the purple circles?
sodium
astr-
starlike: astrocyte-star shaped neuroglia
Satellite cells
surround the cell bodies of peripheral neurons to protect them
A junction between two neurons is called a ______.
synapse
One neuron sends a signal to a nearby neuron through a structure called a(n)
synapse
Where are neurotransmitters stored?
synaptic vesicles
syn-
together: synapse- junction between two neurons
Bundles of axons within the central nervous system are called
tracts
Within the central nervous system, axons bundled together are called ______.
tracts
dendr-
tree: dendrite-branched process that serves as the receptor surface of a neuron
ependym-
tunic: ependyma- neuroglia that line spaces in the brain and spinal cord
A node of Ranvier is a narrow gap between which two structures?
two Schwann cells
bi-
two: bipolar neuron- neuron with two processes extending from the cell body
What determines the action of a neurotransmitter?
type of receptor it binds to
In ___ axons, impulse conduction is uninterrupted along the entire axon; while in ___ axons, action potentials only occur at nodes of Ranvier
unmyelinated; myelinated
Once synthesized, neurotransmitters are stored in membrane-bound structures called
vesicles
As an action potential occurs in one area of the axon, it causes nearby ______ channels to open, initiating another action potential in the neighboring membrane.
voltage-gated
