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Nervous System
Anatomy and Physiology: studying the nervous system
111
Anatomy
Undergraduate 3
12/07/2010

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Cards

Term

Central Nervous System

(CNS)

Definition
brain & spinal cord
Term

Peripheral Nervous System

PNS

Definition

ganglia & nerves

connects the CNS with the rest of the body

 

a) afferent division

b) efferent division

Term

 

Afferent division 

of the

PNS

Definition

(bringing in)

-somatic sensory nerve cells

 

-visceral sensory nerve cells

Term

 

Efferent division

of the

PNS

Definition

(outgoing)


-somatic(voluntary) nervous system


-autonomic(involuntary) nervous system

                                -sympathetic

                                       -parasympathetic

Term

[image]

THE BRAIN

Definition

The BRAIN

-occupies the cranial cavity

 

-cerebrum

-brainstem

-cerebellum

Term

 

Cerebrum

Definition

consists of right and left hemispheres

(divided into lobes)

connected by the corpus collosum

Term

 

Brainstem

Definition

 

attaches the brain to spinal cord

-midbrain

-pons

-medulla oblongata

Term

 

Midbrain

Definition

 

prominent bundles of fibers from/to

the hemispheres

Term

 

PONS

Definition

 

connections between cerebrum

and cerebellum for 

motor efficiency

 

Term

 

Medulla Oblongata

Definition

 

cardiac, vasomotor and

respiratory centers

Term

 

 

Cerebellum

Definition

 

integrates sensory info about

body posture

and

modulates cerebral control over

skeletal muscles

Term

 

The Spinal Cord

Definition

 

the continuation of the CNS outside of 

the skull.

-contains white matter

and grey matter

Term

 

White matter

Definition

 

contains mylinated nerve fibers that

connect the brain with

the rest of the body

 

Term

 

Grey Matter

[image]

Definition

 

consists of unmyelinated fibers

and nerve cell bodies.

(the commissure communicates

the right side with the left)

Term

 

Meninges

Definition

 

-dura mater

-arachnoid

-pia mater

 

(cushion that protects brain)

Term

 

 

Dura Mater

Definition

 

fibrous CT

-the outermost layer forms

venous sinuses.

 

-trauma may cause subdural hematoma

Term

 

Arachnoid

Definition

 

weblike

no blood vessels

but cerebrospinal fluid

instead

Term

 

 

Pia Mater


Definition

 

very thin and vascular

(makes brain shiny)

 

Term

 

 

Meningitis


Definition

 

an inflammation commonly 

involving the arachnoid

and the pia mater

Term

 

Somatic (PNS)

 

Definition

 

nerve supply to the muscular system

and skin

(soma=body wall)

involved CONSCIOUS activity

Term

 

Autonomic (PNS)

 

Definition

 

nerve supply to the viscera (soft organs)

involves UNCONSCIOUS actions

relating to organs and glands

Term

 

 

Sympathetic division 

of the ANS of PNS

(thoracolumbar)

Definition

 

preganglionic cell located in T1-L2

the ganglion is paravertebral and the

postganglionic neuron has a long axon

(hyped up) Ach → NE

Term

 

Parasympathetic division

of the ANS of PNS

(craneosacral)

 

Definition

preganglionic fiber in brain or sacral

the ganglion is near or inside the

target organ.

the postganglionic neuron is short

(yawn, cold, tired)

ACh → ACh

Term

 

Neurotransmitters

of the

PNS

Definition

sympathetic division of the ANS:

-pregang. neurons release Ach(cholinergic)

-postgang. release norepinephrine (adrenergic)

parasympathetic division of the ANS:

-pregang. neurons release Ach

-postgang. release Ach

The adrenal gland recieves cholinergic(ACH) sympathic neurons and release epinephrine and norepinephrine into bloodstream

Somatic efferent neurons are all CHOLINERGIC(ACh)

The primary AFFERENT neurotransmitter remains UNKNOWN

(proposed: ATP, serotonin,histamine,prostoglandin..)

Term

 

The Neuron

 

Definition

 

neurons are the nerve cells that

receive, process and forward

impulses.

Term

 

 

Neuroglia

 

Definition

 

all other nerve cells besides the neurons

that are only supportive.

Term

 

Dendrites

Definition

are cell projections that

receive and bring

impulses to the cell body

Term

 

Axon

 

Definition

 

is the fiber that carries impulses

AWAY

from the cell body

Term

 

Neurofibrils

 

Definition

 

in the cell body and its

projections guide the 

transport of materials

Term

 

Chromatophilic

granules

 

Definition

 

indicate the presence of 

neurotransmitter

material

 

Term

 

Cell membrane

 

Definition
has the ability to carry impulses
Term

 

Membrane Potential

 

Definition

 

the difference in electrical charge between the inside and outside of the cell. represents stored electrical energy that can be put to work.

Term

(membrane potential)

Excitable Cell membranes 

have the capability of..

Definition

 

..changing their permeability so they

can allow ions in or out of the cell

in response to stimulation

Term

 

Mechanism in membrane potential

 

Definition

membrane proteins larger than the

thickness of the cell membrane have one 

end within the cytoplasm and

another outside the cell,

thus acting as channels that can be

open or obstructed (GATED)

Term

 

Consequence in membrane potential

 

 

Definition

 

polarization

Term

 

Polarization

Definition

the ion distribution on the cytoplasmic

side can differ from that on the

outside of the cell

Term

 

Action Potential

(significance of membrane pot.)

 

Definition

membrane stimulation alters 

permeability and polarization and may

cause a nerve impulse, called an

action potential.

Results in the transfer of info.

Term

 

 

Anions

 

Definition

 

negative charged ions

(phosphate, sulfate,proteins)

 

cannot diffuse through the cell membrane

Term

 

Active Transport

 

Definition

 

the sodium potassium pump works 

constantly to move

sodium out of the cell

and potassium into the cell

Term

 

Diffusion

 

Definition

 

slower than active transport

there is a passive leakage of 

sodium into the cell(slow) and

potassium out of the cell (faster)

resulting in a net loss of positive

charge (K+) by the cytoplasm

Term

 

Concentration gradient

 

Definition

 

more Na+ outside the cell

more K+ in the cytoplasm

 

maintained by the sodium potassium pump

Term

 

Resting membrane potential

Definition

a state of electrical polarization

which is developed and maintained

by a living, resting neuron

across its plasma membrane

 

Term

 

Resting membrane

 

Definition

the resting potential is about

-70millivolts

 

Term

 

Membrane depolarization

Definition

 

stimulation → sodium channels now open

sodium enters cell at the point of

stimulation.

the cytoplasm becomes less negative

maybe even positive

Term

 

Repolarization

Definition

slower potassium channels

then open,

and the loss of K+ re-establishes the polarization

Term

 

Hyperpolarization

 

Definition

if the cytoplasm becomes more

negative: inhibition

Term

 

Peripheral Nerve

Definition

the average nerve consists of numerous bundles of 

nerve fibers, which are axons and dendrites with very little else in

common other than their anatomical destination

-epineurium

-perineurium

-endoneurium

Term

 

Epineurium

Definition

 

the superficial collagenous fascia

surrounding the nerve

Term

 

Perineureum

Definition

intermediate fascia

surrounding the fiber fascicles

Term

 

Endoneurium

Definition

 

deep fascia surrounding

individual nerve fibers

Term

 

The compound

action potential

 

Definition

1. the stimulation of a large nerve

2. results in action potentials 

corresponding to different types of fibers

ex: motor sensory myelinated and unmyle.

3.thus a signal can travel at different

velocities

Term

 

Alpha

Definition

 

somatic 

sensory

and motor

30mph

Term

 

Beta

Definition

touch and pressure

15 mph

Term

 

Gamma

Definition

muscular spindles

10mph

Term

 

Delta

Definition

 

pain and temp.

5 mph

Term

 

"B"

Definition

 preganglionic ANS

1mph

Term

 

"C"

Definition

postganglionic ANS

.25MPH

Term

 

The axon terminal

 

Definition

several fine extensions

near the axons end, each with a 

specialized ending called a

synaptic knob(terminal button)

Term

 

Collaterals

Definition

branches the axon may give off

although it starts as a single fiber

Term

 

Synapse

Definition

the transfer of info from a 

presynaptic neuron to a post synaptic

neuron across a synaptic cleft

Term

 

Facilitation

 

The depolarization to threshold of a

postsynatic neuron...

Definition

 

 

depends on the balance between excitatory

and inhibitory input

Term

 

Below threshold excitation makes

the next depolarization more likely...

 

Definition

thus placing the neuron in a state of 

facilitation

Term

 

Stimulation of "A"

causes:

 

Definition

postsynaptic potentials in 1 and 2

facilitation of 3 and 4

Term

 

Stimulation of "A" and "B"..

Definition
 postsynaptic potentials in ALL NEURONS
Term

 

Convergence

[image]

Definition

Many presynaptic neurons

synapse with one

post synaptic neuron

 

allows subthreshold info to add up 

to threshold levels

Term

 

Divergence

 

Definition

 

ONE presynaptic neuron

synapses with MANY

post synaptic neurons

 

allows the amplification of an impulse

Term

 

The generator potential

 

Definition

a graded potential that can be affected by

the strength of the stimulus and the rate

of removal or application of the stimulus.

 

can increase or decrease the magnitude of the post synaptic impulse

Term

 

Consecutive generator potentials

have...

Definition
no refractory periods and can add up
Term

 

Spacial summation

Definition

more neurons (nerve fibers)

are recruited

Term

 

Temporal summation

Definition

 

more impulses are transmitted

per unit-time.

Term

 

Modulation of info transfer

Definition

allowed by changes that can take place at the synapse:

-one neuron can communicate with one or more neurons

-communication can be excitatory or inhibitory or occur with some or all of the other neurons

-nerve impulses involve hundreds of synapses as they traverse pools of neurons

Term

 

Nerve fibers depolarize on...

 

Definition

an "all or none" basis

 

Term

 

Nerve impulses can be..

 

Definition
weak or strong
Term

 

Excitatory post synaptic potentials

 

Definition

sodium opens

 

the neurotransmitter opens NA+ channels and causes a depolarization

EXCITATION: a postsynaptic potential either takes place or becomes more likely

Term

 

Inhibitory postsynaptic potential

Definition

(blocked) potassium opens

the neurotransmitter opens K+ channels and causes a hyperpolarization.

INHIBITION: a postsynaptic potential is less likely to occur

Term

 

Classification of Neurons

Definition

-bipolar

-multipolar

-unipolar

 

Term

 

BIPOLAR

Definition

 

-two processes

one dendrite and one axon

 

ex: in retina

Term

 

 

UNIPOLAR

Definition

one process occurs

for both

dendrite and axon

 

Term

 

 

MULTIPOLAR

Definition

many dendrites

and 

one axon

Term

 

Functionally, neurons can be..

 

 

Definition

Motor(efferent)

Sensory(afferent)

or

Interneurons (association neurons)

Term

 

MOTOR(EFFERENT)

neurons

Definition

 

from CNS to effector

 

Multipolar

Term

 

Sensory(afferent)

neurons

Definition

 

from receptor to CNS

 

unipolar or bipolar

Term

 

Interneurons

(association neurons)

Definition

 

capability to inhibit

 

Multipolar

 

Communication between neurons across commisure

Term

 

MOTOR

innervation

Definition

CNS→motor nerves→periphery

the stimulus for voluntary contraction:

1.      originates in neurons of the cerebral cortex

-may be transmitted to centers in brain stem

-or may descend via the spinal cord

2. Synapses with motor neuron of ventral horn

3. motor impulse exits via spinal nerve (to muscle)

Term

 

Sensory

innervation

Definition

Periphery→Sensory nerve→CNS

Sensory Stimuli:

1.originates in specialized nerve endings of the periphery

2. sensory fiber reaches spinal cord via a spinal nerve

3. dendrite enters doral root ganglion

4. axon leaves doral root ganglion and enters spinal cord

5. synapses with (inter) neuron of dorsal horn

6. impulse ascends to brain through white matter tract of spinal cord

Term

 

The spinal REFLEX

ARC

Definition

 

the sensory neuron synapses with a neuron of the gray matter of the spinal cord at basically the same level at which it enters.

 

receptors reach effectors

WITHOUT BRAIN INVOLVEMENT

there is no concious thought in a reflex

the sensory impulses DO NOT enter an ascending tract of the spinal cord to reach a higher center of the CNS

Term

 

In the spinal reflex arc, a 

particular stimulus always..

 

Definition

elicits the same specific response

(note clinical applicability)

Term

 

Components of the spinal

reflex

Definition

-receptor

-afferent neuron

-efferent neuron

-effector

Term

 

Monosynaptic Reflex

Definition

 

when the afferent neuron synapses with a motor neuron

Term

 

Myotactic reflex

Definition

monosynaptic (no interneurons involved)

important in maintaining posture against gravity.

 

-a muscle is stretched

-muscle spindles register stretch and generate a nerve impulse

-afferent neuron: through dorsal root ganglion, into spinal cord then

-activates the motor neuron of the muscle in question

 

ex: knee jerk(hitting knee stretches tendon, muscles contract)

 

Term

 

Withdrawal reflex

Definition

polysynaptic (interneurons involved)

most CNS reflexes are polysynaptic.

 

-sensory receptor is activated

-afferent neuron carries the impulse to the spinal cord

-impulse reaches interneuron

-one activates a motor neuron(causes withdrawal of the limb)

-another reaches CNS centers (causing awareness)


Term

 

integrative spinal reflex

Definition

there are 2 types:


1) ipsilateral flexion

2) contralateral extension

Term

 

Ipsilateral Flexion

Definition

ipsi = the same

 

 starts with receptor activation


♦motor neuron to flexor

♦inhibitory neuron to extensor muscle

♦interneurons send commissural fibers to opposite

side of the spinal cord.

ex: stepping on tac. The leg and foot that step on the tac react with an ipsi reflex.

Term

 

Contralateral extension

Definition

contra = opposite

starts with commissural interneurons

 

♦ motor neuron to contralateral extensor muscle (excitatory)

♦ inhibitory neuron to contralateral flexor muscle (inhibitory)

Term

 

Sensory receptors

Definition

if activated by the proper stimulus, they generate nerve

impulses in sensory fibers.

 

types:

-exteroceptors

-interoceptors

-mechanoreceptors

-thermoreceptors

-chemoreceptors

-photoreceptors

Term

 

exteroceptors

 

Definition

exter = outside

 

-receive stimuli from body surface

(touch pressure, pain, temperature)

Term

 

Interoceptors

Definition

inter = inside

 

-receive stimuli from internal environment of the body

(pressure, pain, chemical changes)

♦visceroceptors

♦propioceptors

Term

 

Viceroceptors

(part of interoceptors)

Definition

vicer = soft organ

 

monitor blood and viscerae

(pressure, blood gases pH)

Term

 

Proprioceptors

(part of interoceptors)

Definition

think soma

 

receive information on position of body parts

ex: know where your toes are pointing

 

(muscle spindles and golgi tendon organs)

Term

 

 

Mechanoreceptors

Definition

mechan = mechanical, or movement

 

somatic.

 

respond to physical deformation

Term

 

Thermoreceptors

Definition

thermo= tempurature

 

skin, mucosal membranes.

 

respond to temperature

Term

 

Chemoreceptors

Definition

chemo= chemical

 

pH, gases, taste.

 

Respond to chemical reaction

Term

 

Photoreceptors

Definition

photo= light

 

Retina. 

 

Transduce light energy into nerve impulse

Term

 

 

Muscle Spindle

 

Definition

encapsulated stretch receptor located

within skeletal muscle

 

the spindle constantly monitors changes in muscle length

Term

 

Intrafusal fibers

Definition

modified skeletal muscle fibers in

a muscle spindle

Term

 

Motor nerve fibers

_________ intrafusal fibers.

Definition

 

innervate

Term

 

Sensory nerve fibers sensitive to

stretch wrap around the 

___________ fibers.

Definition

 

intrafusal fibers

Term

 

Golgi tendon organ

Definition

sensory fibers in the tendon monitor

tension.

 

they assist in maintaining posture and inhibit muscle contraction if tension becomes excessive.

Term

 

Why does the muscle spindle constantly 

monitor changes in muscle length?

Definition

 

the intrafusal fibers maintain a degree of 

tension at all times, which is close to the 

threshold for the sensory nerve fibers.

Any further stretch of the perimeter of the intrafusal fiber (contraction of the muscle) activates the sensory fibers.

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