Nervous System

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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


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