Anatomy & Physiology chapter 12

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Neuroglia in the CNS that remove cell debris, wastes, and pathogens by phagocytosis

Microglia

What are the least numerous and smallest neuroglia in the CNS?

Microglia

This serves as electrical insulation and increases the speed at which an action potential travels along the axon

Myelin

depolarization results from the influx of ______

Na+, sodium

Whenever a Schwann cell covers an axon, the outer surface of the Schwann cell is called the ______________

Neurilemma

The small, unmyelinated gaps between internodes

Nodes of Ranvier

Where do an axon's collateral branches originate?

Nodes of Ranvier

Which neuroglial cell forms the myelin sheath?

Oligodendrocytes

What makes white matter white?

Regions consisting of heavily-myelinated axons The axons appear glossy white bc of lipids in the myelin

Neuroglia in the PNS that surround neuron cell bodies in ganglia, regulate O2 and CO2, nutrient, & neurotransmitter levels around neurons in ganglia

Satellite cells

What are the two types of neuroglia in the PNS?

Satellite cells and Schwann cells

Neuroglia in the PNS that form myelin sheaths or indented folds of plasma membrane around peripheral axons

Schwann cells

which cells in the PNS play a role in repairing damaged nerves

Schwann cells

The membrane potential is the electrical potential of the cell's interior relative to its _________________

Surroundings

what is a current?

a movement of charges to eliminate a potential difference (btwn ions)

part of refractory period where the membrane cannot respond to further stimulation

absolute refractory period

the most widespread neurotransmitter

acetylcholine

if a graded potential is large enough, it triggers an _______________________ in the membrane of the axon

action potential

membrane channels that open or close in response to specific stimuli

active channels

synapses that release norepinephrine are called __________________

adrenergic synapses

what two FUNCTIONAL divisions can the PNS further divide into?

afferent and efferent

principle that states a given stimulus either triggers a typical action potential, or none at all

all-or-none principle

what is an axon potential?

an electrical impulse that is propagated along the surface of an axon and does not diminish as it moves away from its source

the flow of materials from the cell body to the axon is ___________________ flow, carried by _________.

anterograde; kinesin

at an ____________ synapse, a synapse occurs between the axons of two neurons

axoaxonic

specialized portion of the plasma membrane that surrounds the axoplasm

axolemma

an __________ is a long cytoplasmic process capable of propagating an electrical impulse known as an action potential

axon

the base of an axon in a multipolar neuron joins the cell body at a thickened region known as the __________________

axon hillock

bundles of ___________, or nerve fibers, carry sensory information & motor commands in the PNS

axons

the cytoplasm of an axon

axoplasm

the movement of materials between the cell body and axon terminals is called __________________

axoplasmic transport

the CNS consists of the _________ and the ________________

brain; spinal cord

what does the enzyme acetylcholinesterase do?

breaks down molecules of ACh by hydrolysis into acetate and choline

what is the afferent division of the PNS?

brings sensory information to the CNS

the arrival of what ion in the axon terminal triggers the exocytosis of ACh?

calcium

what is the efferent division of the PNS?

carries motor commands from the CNS to muscles, glands, & adipose tissue

the most abundant types of synapses

chemical synapses

what type of gated ion channels are the ACh receptors on the postsynaptic neuron?

chemically gated ion channels

after ACh is broken down into acetate and choline by acetylcholinesterase, what does choline do? what does acetate do?

choline: absorbed by the axon terminal & used to synthesize more ACh (with coenzyme A) acetate: absorbed by postsynaptic cell/other cells/tissues

synapses that release acetylcholine

cholinergic synapses

an axon may branch along its length, producing side branches known as _______________

collaterals

in an unmyelinated axon, an action potential moves along by ________________________

continuous propagation

nerves connected to the brain

cranial nerves

what is the intracellular fluid of a cell called?

cytosol

mechanically gated channels are typically located only on the __________ of sensory neurons

dendrites

materials that travel slowly from the cell body to the axon terminal, called the _____________

"slow stream"

the threshold for an axon is typically between ____ mV and _____ mV

-60; -55

slender, sensitive processes that extend out from the cell body (of the neuron)

dendrites

what are unipolar neurons?

dendrites & axons are continuous (fused) & cell body lies off to one side

where are chemically gated channels most abundant?

dendrites & cell body of neurons (areas where most synaptic communication occurs)

any shift from the resting membrane potential toward a more positive potential is called a _________________.

depolarization

what is the normal stimulus for neurotransmitter release?

depolarization of the axon terminal by the arrival of an action potential

a neurotransmitter of the CNS that has inhibitory and excitatory effects

dopamine

organs targeted by the efferent division of the PNS are called ______________.

effectors

neurotransmitter release is triggered by _____________________

electrical events

a synapse may be ______________ or _________________.

electrical; chemical

the membrane potential at which there is no net movement of a particular ion across the plasma membrane

equilibrium potential

neurotransmitters that cause depolarization and promote the generation of action potentials

excitatory neurotransmitters

a graded depolarization caused by the arrival of a neurotransmitter at the postsynaptic membrane

excitatory postsynaptic potential

what are the two major types of postsynaptic potentials?

excitatory postsynaptic potentials (EPSP) and inhibitory postsynaptic potentials (IPSP)

another way of saying a neuron is close to threshold

facilitated

in presynaptic ______________, the activity at an axoaxonic synapse increases the amount of neurotransmitter released when an action potential arrives at the axon terminal

facilitation

true or false; neurons come in only one shape/size

false

true or false; the properties of the action potential are dependent of the relative strength of the depolarizing stimulus

false

true or false; dendritic spines represent 30-40% of a neuron's total surface area

false; 80-90%

true or false; an action potential that reaches a chemical synapse will always be propagated to the next cell

false; an arriving action potential may or may not release enough neurotransmitter to bring the postsynaptic neuron to threshold

true or false; at resting membrane potential, most gated channels are open

false; closed

true or false; electrical synapses are very common

false; extremely rare

true or false; all stimuli that bring the membrane to threshold generate different action potentials

false; identical action potentials

true or false; the chemical gradient is not strong enough to overpower the electrical gradient

false; the chemical gradient is strong enough to overpower the electrical gradient, but the electrical gradient weakens the force

true or false; the effect of a neurotransmitter on the postsynaptic membrane depends on the nature of the neurotransmitter

false; the effect depends on the properties of the receptor

true or false; the postsynaptic cell can only be a neuron

false; the post synaptic cell can either be a neuron or another type of cell

true or false; the presynaptic membrane bears receptors for neurotransmitters

false; the presynaptic membrane is where neurotransmitters are released

true or false; the sympathetic & parasympathetic division of the autonomic nervous system have the same effect

false; they have opposite effects

what does GABA stand for?

gamma-aminobutyric acid

at electrical synapses, the presynaptic and postsynaptic membranes are locked together at ________ junctions. the opposing membranes are held in position by proteins called _______________, which form pores that allow ions to pass between the cells.

gap; connexons

active channels are also known as _____________ channels

gated

compounds that have direct effects on membrane potential open or close ______________ channels

gated ion

a typical stimulus produced a temporary, localized change in the resting membrane potential, this effect is called a _________________________.

graded potential

aka local potentials, are changes in the membrane potential that cannot spread far from the site of stimulation

graded potentials

what are bipolar neurons?

have one dendrite that branches extensively into dendritic branches at its distal tip & one axon, with cell body in between the two -rare -occur in special sense organs -small

what are multipolar neurons?

have two or more dendrites and a single axon -most common neurons in CNS

-70 mV --> -80 mV is an example of: _____________________

hyperpolarization

an increase in the negativity of the resting membrane potential; the loss of positive ions from inside the cell

hyperpolarization

in presynaptic ______________, activity at an axoaxonic synapse decreases the amount of neurotransmitter released when an action potential arrives at the axon terminal

inhibition

neurotransmitters that cause hyperpolarization and suppress the generation of action potentials

inhibitory neurotransmitters

a graded hyperpolarization of the postsynaptic membrane caused by the arrival of a neurotransmitter at the postsynaptic membrane

inhibitory postsynaptic potential

what are the general functions of the CNS?

integrating, processing, & coordinating sensory data & motor commands

neurons are nerve cells specialized for _____________________

intercellular communication

neurotransmitters that alter ion movement across the membrane are said to have _____________ effects

ionotropic

materials, such as neurotransmitters, enzymes, & lysosomes travel the length of the axon on neurotubules pulled by ______ and ________; "molecular motors" that run on ATP

kinesin, dynein

at resting membrane potential, ions move through ___________ channels

leak

movement of positive charges parallel to the inner and outer surfaces of a membrane: _________________

local current

gated channels that open or close in response to physical distortion of the membrane surface

mechanically gated channels

neurotransmitters that indirectly affect the postsynaptic cell by changing metabolic activity are said to have _____________ effects

metabotropic

why is the inner surface of a neuron negatively charged?

negatively charged proteins inside the cell are too large to cross the membrane and get out

an action potential in a neuron plasma membrane is also known as a ________________

nerve impulse

bundles of axons with associated blood vessels and connective tissues are called ____________

nerves

bundles of neurofilaments, called __________________, extend into the dendrites and axon, providing internal support for them

neurofibrils

the cytoskeleton of the perikaryon contains ______________ and ______________, which are similar to the intermediate filaments & microtubules of other types of cells

neurofilaments, neurotubules

synapse between a neuron & a glandular cell

neuroglandular junction

a compound released by a neuron that alters the rate of neurotransmitter released by the presynaptic neuron or change the postsynaptic cell's response to neurotransmitters

neuromodulator

synapse between a neuron & a muscle cell

neuromuscular junction

the basic functional units of the nervous system are individual cells called ____________.

neurons

neuromodulators are typically _____________, small peptide chains synthesized & released by the axon terminal

neuropeptides

which two gasses are known to be important neurotransmitters?

nitric oxide (NO) carbon monoxide (CO)

will a stimulus that shifts the resting membrane potential from -70 mV to -62 mV produce an action potential?

no

norepinephrine (NE) is also called _________________

noradrenaline

neurotransmitter that is widely distributed in the brain and ANS, typically has an excitatory (depolarizing) effect on the postsynaptic membrane

norepinephrine

neuromodulators that inhibit the release of the neurotransmitter substance P at synapses that relay pain sensations

opioids

leak channels are also known as ____________ channels

passive

membrane channels that are always open

passive channels

the cytoplasm surrounding the nucleus (in neurons) is the __________________

perikaryon

what is a synaptic delay?

period between arrival of a nervous impulse at the presynaptic membrane and the initiation of an action potential in the postsynaptic membrane

this includes all the neural tissue outside the CNS

peripheral nervous system

the cell involved in a synapse that receives the message

postsynaptic cell

membrane in a synapse that bears receptors for neurotransmitters

postsynaptic membrane

graded potentials that develop in the postsynaptic membrane in response to a neurotransmitter

postsynaptic potentials

the cell involved in a synapse that sends a message & includes the axon terminal

presynaptic cell

sensory structures that either detect changes in the environment (internal or external) or respond to specific stimuli

receptors

the time an action potential begins until the normal resting membrane potential has stabilized

refractory period

what are Nissl bodies?

regions of the perikaryon of a neuron that contain clusters of rough endoplasmic reticulum and free ribosomes -stain darkly -give gray color to areas containing neuron cell bodies (gray matter)

part of refractory period where the membrane can respond to further stimulation but only if it is larger than normal

relative refractory period

the primary function of opioids is probably to __________________.

relieve pain

the process of restoring the normal resting membrane potential after depolarization is called ________________

repolarization

the ______________ of the membrane is a measure of how much the membrane restricts ion movement

resistance

all neural activities begin with a change in the _______________________ of a neuron

resting membrane potential

the flow of materials from the axon terminal to the cell body is ______________ flow, carried by ________.

retrograde; dynein

which carries axon potentials faster? saltatory or continuous propagation?

saltatory

in a myelinated axon, an action potential moves along by _________________________.

saltatory propagation

the PNS delivers ___________ information to the CNS and carries _________ commands to peripheral tissues/systems

sensory; motor

a CNS neurotransmitter that is related to depression

serotonin

what are anaxonic neurons?

small neurons with many dendrites and no axon -located in brain & special sense organs

if the resistance of a membrane is high, then the current is ______. if the resistance is low, then the current is _____.

small; large

the ECF contains high concentrations of ______________ and _____________, whereas the cytosol contains high concentrations of ________________ and ________________.

sodium ions (Na+) chloride ions (Cl-); potassium ions (K+), negatively charged proteins

ion pump that exchanges THREE intracellular sodium ions for TWO extracellular potassium ions during normal resting potential of the cell

sodium-potassium ATPase

also called the cell body of a neuron

soma

what can the efferent division of the PNS be further divided into?

somatic nervous system & autonomic nervous system

what is the difference between the somatic nervous system & the autonomic nervous system?

somatic: controls SKELETAL muscle contractions (both subconscious & conscious) autonomic: controls smooth & cardiac muscle, glandular secretions, & adipose tissue (SUBCONSCIOUS)

multiple synapses that are active simultaneously at different locations have a cumulative effect on the membrane potential

spatial summation

nerves attached to the spinal cord

spinal nerves

what is the electrochemical gradient?

sum of the chemical and electrical forces acting on that ion across the plasma membrane

the effects of all the graded potentials that affect one portion of the plasma membrane

summation

what are neuroglia?

supporting cells to the neurons -preserve neural tissue -separate/protect neural tissue -act as phagocytes -help regulate composition of interstitial fluid

what can the autonomic nervous system of the PNS be further divided into?

sympathetic division & parasympathetic division

the activity of the _____________ division accelerates the heart rate, whereas _________________ activity slows the heart rate

sympathetic; parasympathetic

a specialized site where a neuron communicates with another cell

synapse

during a synapse, a narrow space called the ___________________ separates the two cells

synaptic cleft

_____________ occurs when resynthesis and transport mechanisms cannot keep up with the demand for neurotransmitter and the synapse weakens until ACh is replenished

synaptic fatigue

inside the axon terminal of the presynaptic cell, neurotransmitters are contained in ______________

synaptic vesicles

most of the ACh in the axon terminal of the presynaptic neuron is packaged in ____________________.

synaptic vesicles

the main axon trunk and any collaterals end in a series of fine extensions called _______________

telodendria

the addition of stimuli occurring in rapid succession at a single synapse that is active repeatedly

temporal summation

what is resting membrane potential?

the membrane potential of an unstimulated, resting cell

why can typical CNS neurons not divide?

they lack centrioles (organelles important in moving chromosomes during mitosis)

the membrane potential at which an action potential begins

threshold

true of false; a multipolar neuron is the most common type of neuron in the CNS

true

true or false; a cell's membrane permeability varies by ion

true

true or false; an action potential that reaches an electrical synapse is always propagated to the next cell

true

true or false; axoplasmic transport occurs in both directions

true

true or false; dynorphins have far more powerful pain-relieving effects than morphine or the other opioids

true

true or false; neuroglia far outnumber neurons

true

true or false; one neuron may communicate with another at a synapse on a dendrite, on the cell body, or along the length of the axon of the receiving cell

true

true or false; roughly half of the ACh released at the presynaptic membrane is broken down before it reaches receptors on the postsynaptic membrane

true

true or false; sodium and potassium ions are the primary determinants of the membrane potential of many cell types, including neurons

true

true or false; sodium-potassium ATPase pump ejects sodium ions as quickly as they enter the cell

true

true or false; the all-or-none principle applies to all excitable membranes

true

true or false; the degree of depolarization (in graded potential) decreases with distance away from the stimulation site

true

true or false; the diameter of the axon has effects on the propagation speed of an action potential

true

true or false; vesicles containing neurotransmitters move much more rapidly (from soma to axon terminal)

true

what are the 3 classes of gated channels?

1. chemically (ligand) gated channels 2. voltage-gated channels 3. mechanically gated channels

what are the four classes of opioids in the CNS?

1. endorphins 2. enkephalins 3. endomorphins 4. dynorphins

why is regeneration of axons limited in the CNS?

1. many more axons are likely to be involved in an injury 2. astrocytes produce scar tissue that can prevent axon growth across the damaged area 3. astrocytes release chemicals that block the regrowth of axons

How man types of neuroglia are in the PNS?

2

viewed anatomically, how many divisions does the nervous system have? what are they?

2; central nervous system & peripheral nervous system

the average number of ACh molecules in a single vesicle is _____________.

3000

What is the difference between myelination by Schwann cells and myelination by oligodendrocytes?

A myelinating Schwann cell can myelinate only one segment of a single axon, whereas an oligodendrocyte in the CNS may myelinate portions of several adjacent axons

the sodium-potassium pump requires energy in the form of _______

ATP

most sensory information arrives over type ___ fibers

C

True or false; all axons in the CNS are myelinated

False

True or false; each oligodendrocyte can only myelinate one axon

False; each oligodendrocyte myelinates segments of several axons

True or false; the cell bodies of astrocytes are smaller than that of the oligodendrocyts

False; the cell bodies of oligodendrocytes are smaller & have fewer processes

Are ependymal cells found in the CNS or PNS?

CNS

the _______ is the seat of higher functions, such as intelligence, memory, learning, & emotion

CNS

neurotransmitter of the CNS with generally inhibitory effects ; seems to reduce anxiety

GABA

What makes up the gray matter of the CNS?

Areas containing neuron cell bodies, dendrites, & unmyelinated axons

Neuroglial cells of the CNS that: 1. Maintain BBB 2. Provide structural support 3. Regulate ion, nutrient, and dissolved gas concentrations 4. Absorb & recycle neurotransmitters 5. Form scar tissue after injury 6. Guiding neuron development

Astrocytes

Which type of neuroglial cells provide a 3D framework for the CNS?

Astrocytes

Neuroglial cells of the CNS that line ventricles (brain) and central canal ( spinal cord); assist in producing, circulating, and monitoring cerebrospinal fluid

Ependymal cells

The areas of an axon that are wrapped in myelin are called ______________.

Internodes

in an action potential, repolarization involves loss of ______

K+, potassium

True or false; internodes are typically 1-2 mm in length

True

what are type A, B , and C fibers?

type A: largest myelinated axons, diameters 4-20 micrometers, carry action potentials up to 120 meters per second (268 mph) -sensory information about position balance, touch & pressure -also motor neurons that control skeletal muscles type B: smaller myelinated axons, diameters 2-4 micrometers, carry action potentials up to 18 meters per second (40 mph) -carry info to/from CNS -temperature, pain type C: unmyelinated axons, less than 2 micrometers in diameter, carry action potentials up to 1 meter per second (2 mph) -carry info to/from CNS -temperature, pain

gated channels that open or close in response to changes in the membrane potential; often found in areas of excitable membrane

voltage-gated channels


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