Exam 2 - Nervous Flashcards by James Ozorkiewicz

two systems responsible for maintaining homestasis

nervous and endocrine

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regulates body activities by responding rapidly using nerve impulses

nervous system

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system responds more slowly by use of hormones

endocrine system

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the branch of medical science that deals with the normal functioning and disorders of the nervous system

neurology

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brain and spinal cord

CNS

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12 cranial nerves, spinal nerves (31 pairs), peripheral nerves

PNS

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The nervous system comprises:

brain, spinal cord, spinal nerves, ganglia, enteric plexuses, and sensory receptors

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functions of the nervous system

sensory, integrative, motor

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detect changes in internal / external environment
carry info to brain and spinal cord
afferent neurons

sensory

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afferent neurons

sensory receptors

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analyze and store info
make decisions
many are interneurons, relatively short in brain, spinal cord, and ganglia that connect nearby neurons

Integrative

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responds to decisions
motor neurons carry info from brain to spinal cord to effectors (muscles or glands)
efferent neurons

Motor

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efferent neurons

motor neurons

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general organization of the nervous system

somatic
autonomic
enteric

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sensation from body wall, limbs, head, special senses (sight, hearing, taste, balance, smell)

somatic

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motor control of skeletal muscle

somatic (voluntary control)

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sensation from internal organs like heart, lungs, bladder

autonomic

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motor control of smooth and cardiac muscle (i.e. involuntary muscle), glands (involuntary control)

autonomic

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sensation from gastrointestinal tract

enteric

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motor control of smooth muscle and glands of the GI (involuntary control)

enteric

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consists of all nervous tissue outside the CNS

PNS

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made up of Somatic, Autonomic, and Enteric Nervous Systems

PNS

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has both sensory and motor neurons

PNS

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The motor part of the ANS has which two branches?

sympathetic and parasympathetic

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an association (a bundle) of neuronal axons in the PNS

nerve

a group of neuronal cell bodies in the PNS

ganglion

an association (a bundle) of neuronal axons in the CNS

tract

an association (a bundle) of (unmyelinated) nerve cell bodies in the CNS

Nucleus

an extensive network of nerves found within the PNS

Plexus

cells that have the property of electrical excitability, and are specially adapted to produce and transmit AP's

Neurons

cells of the NS that support, flourish, and protect the neurons

Neuroglia

are there more neuroglia or neurons? Why?

neuroglia stupid! neurons do not replace themselves via mitosis like neuroglia

what are the basic parts of the neuron

cell body and nerve fibers comprising of an axon and dendrites

name adaptions for neurons

axoplasm (the cytoplasm of an axon) | axolemma (the plasmalemma of axon)

axoplasm

(the cytoplasm of an axon)

axolemma

(the plasmalemma of axon)

like most cell neurons have nucleus, cytoplasm, typical organelles what are the specialized forms of organelles?

Nissl bodies (prominent clusters of rough ER)

prominent clusters of rough ER in a neuron

Nissl bodies

little trees

dendrites

typically short, tapering, highly branched

dendrites

propagates impulses to another neuron, muscle, or nerve

axon

can approximate three feet in humans

axon

almost always a single axon per nueron, T or F

True

typically arises from an elevation in the cell body called the axon hillock

axon

small hill of the neuron

axon hillock

first part of the axon

intial segment

impulses i.e. AP's generally arise in the

trigger zone

the junction of the hillock an initial segment

trigger zone

if an axon is cut what happens

distal fragment dies

does axon contain RER?

No... protein synthesis does not occur in axon

axon contains?

Mitochondira Microtubules Neurofibrils

may branch of main axon

axon collaterals

end of axons and collaterals

axon terminal (telodendria)

telodendria

end of axons and collaterals

telodendria end in either

synaptic bulbs | varicosities

synaptic bulbs are

bulb-shaped structures at end of telodendria

varicosities are

string of swollen bulbs at end of telodendria

cytoskeleton of typical neuron comprised of

neurofibrils | microtubules

neurofibrils of typical neuron

intermediate filaments which provide structure and support

microtubules of typical neuron are made of and do what?

tubulin | moving material between the cell body and axon

what does synthesis of new proteins, vessicles, etc take place in the neuron?

cell body not axon

how far apart can cell body and axon terminals be?

over a meter

one way only, cell body to axon terminals | transports axoplasm to growing or generating axons

slow axonal transport

two way transport, both toward and away from cell body uses microtubules as "tracks" and "motors" transports organelles and materials that are used to form axolemma membranes, synaptic end bulbs, and synaptic vessicles

fast axonal transport

Look at slide 21 of ppt... before you do imagine the three structural classifications of neurons

multipolar bipolar pseudounipolar

special senses think

bipolar neuron

sensory neurons think

pseudounipolar neuron

structural classification of neurons is based on...

processes (axons or dendrites) extending from the cell body

key takeaway from structural classification?

trigger zone of each neuron location

the vast majority of the neurons in the human body are

multipolar neurons

have several dendrites and only one axon and are located throughout the brain and spinal cord

multipolar neurons

have one main dendrite and one axon

bipolar neurons

are used to convey the special senses of sight, smell, hearing, and balance and are found where?

bipolar neurons | found in retina of eye, inner ear, and olfactory area of the brain

contain one process which extends from the body and divides into a central branch that functions as an axon and as a dendritic root

unipolar neurons (psuedounipolar)

often employed for sensory neurons that convey touch and stretching info from extremities

unipolar neurons (psuedounipolar)

not excitable cells | small, more numerous than neurons

neuroglia

play a supporting role (nourishment) | make up half the volume of the CNS

neuroglia

in cases of injury or disease, multiply to fill in spaces formerly occupied by neurons

neuroglia

not excitable cells small, more numerous than neurons play a supporting role (nourishment) make up half the volume of the CNS in cases of injury or disease, multiply to fill in spaces formerly occupied by neurons

neuroglia

astrocytes microglia oligodendrocytes ependymal cells AMOE

Neuroglia of the CNS

astrocytes microglia oligodendrocytes ependymal cells

Neuroglia of the PNS

``` Schwann cells (neurolemmoytes) Satellite cells ```

Neuroglia of the PNS

regulate the composition of the extracellular fluid in the CNS help form the BBB take up excess neurotransmitters may influence formation of neuronal synapses

Astrocytes (star shaped)

phagocytes of the CNS

Microglia

line the ventricles of the brain; produce, monitor, and aid in circulation of CSF; help form the blood CSF barrier

Ependymal cells (of CNS)

myelinate axons in the PNS

Schwann cells

neuroglia of the CNS completely surround ___ and ___ of neurons

axons and cell bodies of neurons

do not typically undergo mitosis, meaning if a neuron dies there is no reservoir of cells to replace it

neurons

do undergo mitosis (can be highly malignant and grow rapidly i.e. brain tumors -- can be highly malignant and grow rapidly, and include astrocytomas, oligodendrogliomas, and schwannomas

neuroglial cells

No mitosis

nuerons

yes mitosis

neuroglial cells

myelination is produced by ___ of the CNS and ____ of the PNS

Oligodendrocytes (CNS) Schwann cells (PNS)

a multi-layered complex of lipids and proteins, i.e. player of plasma membranes insulates axons (prevents loss of electrical signal speeding up conduction of nerve impulses)

myelin

a ___ or ___ can be associated with a neuron, yet the neuron may be unmeylinated. Myelination requires

Schwann cell (neurolemmocyte) or oligodendrocyte requires the glial cell to have wrapped its plasma membrane around the axon many times

schwann cell in the

PNS

oligodendrocytes in the

CNS

the outer nucleated cytoplasmic layer of the schwann cell, which encloses the myelin sheath is the ____

neurolemma

unmyelinated cells w/ Schwann cells means axons lay in grooves on the surface of schwann cells but there is no

myelin sheath and no neurolemma

neurolemmocyte

schwann cell

schwann cell inner portion encircles the axon, forming many layers that comprise the

myelin sheath

resides in the neurolemma (outer nucleated cytoplasmic layer of the schwann cell)

nucleus of the neurolemmocyte

outer lay of a myelinating Schwann cell

neurolemma

contains the nucleus and virtually all the cytoplasm of Schwann cells, not to be confused with Axolemma which NS?

Neurolemma in the PNS

only on nerve fibers supplied by potentially nerve-producing cells gaps between myelinating cells (where there is no myelin)

nodes of ranvier (found in CNS and PNS)

a nerve fiber consists of

axon plus myelin sheath

the ___ surrounds the nerve fiber

endoneurium

the endoneurium overlies the

Schwann cells

have multiple processes each process can form a myelinated segment where they can myelinate several segments of ONE axon OR several axons

oligodendrocytes

are neurolemmas present in the CNS? | why?

NO; oligodendrocyte cell body and nucleus do not envelope the axon

one oligodendrocyte can myelinate multiple times there is no? there are?

no neurolemma are nodes of Ranvier

color of myelin and type of matter

white; white matter of the CNS

matter or region with neuronal cell bodies and no myelin what makes it gray?

gray matter; Nissl bodies make it gray

Virtually all cells in the body exhibit a membrane potential, which is an electrical voltage difference across the membrane T or F

True

Nerve cells are highly adapted for using membrane potentials, and changes in membrane potentials, to initiate and transmit nerve impulses T or F

Neurons communicate with one another by using which two types of electrical signals?

``` Action potentials (nerve impulses), for both short and long distance communication within the body. This is “all-or-none” ``` Graded potentials, for short-distance (localized) communication only. The physiological role of graded potentials is to affect (and effect) the generation of action potentials. This is NOT “all-or-none”

Neuronal signals: Both types of signal depend on which two features of the plasma membrane of excitable cells?

– Existence of a resting membrane potential – Presence of specific ion channels

Are there more specific leakage channels for K+ or for Na+

K+

Is the resting membrane is more permeable to K+ or to Na+

K+

The resting membrane potential is due to a small buildup of anions in the cytosol just inside the membrane, and an equal buildup of cations in the extracellular fluid just outside the membrane

Equal numbers, but on opposite the membrane, sides!

higher sodium and Cl where

ECF

Higher K, organic phosphates, amino acids, proteins where?

ICF

The resting membrane is 50 to 100 times more | permeable to ___ than to ____

K+ than to Na+

Cl- permeability is in between that of Na+ and K+

True dat

The membrane is impermeable to nearly all of the negatively charged intracellular molecules

True dat times two

▪ K+ diffuses down its concentration gradient out of the cell ▪The intracellular negatively charged ions are left behind because they can’t get through the membrane ▪The interior of the membrane becomes negatively charged; the exterior becomes positively charged; net diffusion of K+ stops (electrochemical equilibrium) ▪Na+ diffuses into the cell but at a much lower rate than K+ diffuses out because the membrane is less permeable to Na+ ▪A little Cl - diffuses into the cell, also making the interior more negative ▪Net result: the resting membrane potential

ESTABLISHING THE RESTING MEMBRANE POTENTIAL

▪___ or ____ gated ion channels produce graded potentials in response to stimuli ▪_____ means the size of the change in the membrane potential varies in proportion to the strength of the stimulus (not all-or-none) ▪Local effects only: channels open, current flows through the membrane and along the membrane, and travels only a short distance before diminishing to zero

GRADED POTENTIALS ▪Ligand-gated or mechanically gated ion channels produce graded potentials in response to stimuli ▪“Graded” means the size of the change in the membrane potential varies in proportion to the strength of the stimulus (not all-or-none) ▪Local effects only: channels open, current flows through the membrane and along the membrane, and travels only a short distance before diminishing to zero

A graded potential can either ____ the membrane or ____the membrane

depolarize hyperpolarize

membrane becomes more polarized (more negative)

hyperpolarization

membrane becomes less polarized (less negative or more positive)

–Depolarization:

difference between graded potentials and action potentials?

▪graded potentials are a localized phenomenon, and do not travel far before being attenuated, once an action potential is generated it travels the length of the neuron and can initiate an action potential in subsequent neurons, muscles, or glands ▪Action potentials are all-or-none

▪_____ accompanies opening of voltage-gated Na+ channels. Stimulus causes depolarization to threshold (-55 mV) ▪_____ accompanies opening of voltage-gated K+ channels and closure of Na+ channels

Depolarization Repolarization

– ___ has both Na+ and K+ voltage- gated channels closed – ____ has Na+ gates open – ______ accompanied by K+ gates open and Na+ gates closed or closing – Resting state restored finds K+ gates closed

Resting state Depolarization Repolarization

▪The _____ progresses sequentially down the length of the axon ▪The _____ measured at a fixed point on the axon varies with time as the action potential transits the point

action potential voltage

CALCIUM ION DEFICIT ▪______ appear to bind to the exterior surfaces of the sodium channel protein molecule. ▪The _____ charges of the calcium ions alter the electrical state of the channel protein, increasing the voltage level required to open the gate. ▪Absent the bound calcium ions, ____ than normal voltages are required for gate activation.

Calcium ions positive smaller

CALCIUM ION DEFICIT ▪Calcium ion concentration in the _____ therefore has an effect on the voltage level at which sodium channels become activated. ▪When there is a deficit of calcium ions, the sodium channels become ______ by very little change of the membrane potential from its normal resting level. ▪The nerve fiber then becomes ___ ____, sometimes discharging repetitively without provocation, rather than remaining in the resting state.

extracellular fluid activated (open) highly excitable

_____ is associated with muscle contraction, cramps, and even tetany, which can be lethal because of tetanic contraction of the respiratory muscles

low blood calcium

Propagation of nerve impulses ▪Nerve impulses must travel from where they arise at a trigger zone (typically the axon hillock) down the neuron to the axon terminals. ▪That movement is called _________ ▪Propagation depends on ______ feedback

propagation, or conduction positive

Positive feedback of propagation ▪The inflow of _____ ions causes depolarization that opens voltage-gated Na+ channels in adjacent segments of the membrane ▪Those in turn allow in sodium ions, causing that segment to _____, and so on down the axon

sodium depolarize

Explain the function of dendrites:

Receive stimuli through activation of ligand-gated or mechanically-gated ion channels. In sensory neurons produces generator or receptor potential. In motor neurons and interneurons produces excitatory and inhibitory postsynaptic potentials

Explain the function of the cell body:

Receives stimuli and produces EPSPs and IPSPs through activation of ligand-gated or mechanically gated ion channels

Explain the function of the Junction of the axon hillock and initial segment of axon:

Trigger zone in many neurons integrates ESPSs and IPSPs--- if sum is depolarization that reaches threshold, initiates action potential (nerve impulse)

Explain the function of the axon:

Propagates (conducts) nerve impulses to axon terminals in a self- reinforcing manner. Impulse amplitude does not change as it propagates along the axon

Explain the function of the axon terminals and synaptic end bulbs (varicosities):

Inflow of Ca2+ caused by depolarizing phase of nerve impulse triggers exocytosis of neurotransmitters from synaptic vesicles

Types of conduction ▪Step-by-step depolarization and repolarization of adjacent segments is termed ______. ▪______ is a special mode of impulse propagation that occurs along myelinated axons

continuous conduction. Saltatory conduction

Saltatory conduction ▪Only in ______ ▪Voltage-gated channels are concentrated at _______, with few in regions where the myelin sheath covers the ______ ▪______ is carried by extracellular and intracellular ions from one node to the next, and the nodes depolarize and repolarize as previously discussed

myelinated axons nodes of Ranvier; axolemma Electric current

▪ Saltatory conduction is much ____ than continuous conduction ▪ It is also more energy efficient, requiring less ____ to repolarize

faster ATP

Metabolism ▪Neurons produce virtually all their ATP via _____ of glucose ▪This process requires large amounts of ____, so the nervous system requires a high blood flow, and is consequently highly vascularized ▪Alternative—and very minor—sources of energy for neurons are ______, ____, and ____.

aerobic metabolism oxygen ketones, medium chain fatty acids, and possibly amino acids

Metabolism ▪Most of the brain’s energy consumption goes into sustaining the __________ ▪The majority of vertebrate species devote between 2% and 8% of basal metabolism to the brain. It is higher in primates, and in humans it rises to 20% to 25%

electric charge of neurons

The greater the diameter of the axon, the faster the conduction will be (less resistance to the flow of ions through the axoplasm) ▪ __ fibers – Large diameter – Myelinated – Conduct at about 100 meters/second (around 200 miles per hour) ▪__ fibers – Medium diameter – Myelinated – Conduct at about 15 meters/second (around 32 miles per hour) ▪__ fibers – Small diameter – Unmyelinated – Conduct at about 1 meter/second (around 3 miles per hour)

▪ A fibers – Large diameter – Myelinated – Conduct at about 100 meters/second (around 200 miles per hour) ▪B fibers – Medium diameter – Myelinated – Conduct at about 15 meters/second (around 32 miles per hour) ▪C fibers – Small diameter – Unmyelinated – Conduct at about 1 meter/second (around 3 miles per hour)

Perceiving stimulus intensity ▪Since all nerve impulses are the same size, there would not seem to be a way to distinguish between stimuli of different magnitudes ▪Two mechanisms enable stimuli of differing intensities to be registered as such ________

– Frequency of impulses | – Number of sensory neurons activated (recruited)

Example of intensity perception (using touch) ▪Frequency of impulses – A light touch generates a _____ of widely spaced nerve impulses – A firm pressure causes nerve impulses to go down the axon closer together (i.e. at a higher frequency) ▪Number of sensory neurons recruited – A light touch stimulates only a few pressure sensitive neurons – A firm pressure stimulates more pressure sensitive neurons

low frequency

Stimulus strength and generation of action potential ▪No action potential is generated by a ___ stimulus. ▪Several action potentials result from a ____ stimulus, yet each has the same amplitude. This is perceived as a stronger stimulus.

subthreshold suprathreshold

Exam 2 - Nervous Flashcards

(153 cards)