Spinal Cord, Nerves, and Reflexes Flashcards by Enide Clerizier

State the function of the spinal cord

conduction
neural integration
locomotion
reflexes

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location, segments, spinal nerves that exit from it, and regions of

Conus medullaris

cord tapers to a point inferior to lumbosacral enlargement

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location, segments, spinal nerves that exit from it, and regions of

Cauda Equina

bundle of nerve roots that occupy the vertebral canal from L2 to S5

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the three parts of the meninges

Dura mater
Arachnoid mater
Pia mater

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Explain the location and function

Dura Mater

location: the large venous channels (dural sinuses) arachnoid

function: carrying blood from the brain toward the heart.

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Explain the location and function

Arachnoid Mater

location: connect the dura mater to the pia mater

function: plays an important protective role by acting as a shock absorber.

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Explain the location and function

Pia mater

location: innermost layer between arachnoid meter and brain

supply your brain tissue with blood. It also helps contain cerebrospinal fluid

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neuron cell bodies with little myelin

grey matter

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Site of information processing, synaptic integration

gray matter

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abundantly myelinated axons

white matter

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Carry signals from one part of the CNS to another

white matter

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carry motor information down

descending spinal tracts

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carry sensory information up

ascending spinal tracts

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types of neurons in ascending tracts

First-order neurons
Second-order neurons
Third-order neurons

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detect stimulus and transmit signal to spinal cord or brainstem

First-order neurons

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continues to the thalamus at the upper end of the brainstem

Second-order neurons

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carries the signal the rest of the way to the sensory region of the cerebral cortex

Third-order neurons

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what does Ascending tracts do

carry sensory signals up the spinal cord

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name the ascending spinal tracts

-Anterior spinothalamic tract
-Lateral spinothalamic tract
-Spinoreticular tract
-Spinocerebellar tract

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type of sensation that is carried by spinothalamic tract

carries signals for pain, pressure, temperature, light touch, tickle, and itch

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the first, second, and third order neuron, where it crosses and synapses for

spinothalamic tract

First-order neurons end in posterior horn
of spinal cord
Second-order neurons start in posterior
horn, then decussate and form the
spinothalamic tract
Third-order neurons continue from there
to cerebral cortex

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state the type of sensation that is carried from the Spinoreticular tract

Carries pain signals resulting from tissue injury

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the first, second, and third order neuron, where it crosses and synapses for Spinoreticular tract

First-order neurons enter posterior horn and immediately synapse with second-
order neurons
Second-order neurons decussate to opposite anterolateral system; ascend the cord and end in reticular formation: loosely organized core of gray matter in the medulla and pons
Third-order neurons continue from the pons to the thalamus
Fourth-order neurons complete the path to the cerebral cortex

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state the type of sensation that is carried from the Spinocerebellar tract

Carry proprioceptive signals from limbs and trunk up to the cerebellum

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the first, second, and third order neuron, where it crosses and synapses for Spinocerebellar Tracts

* First-order neurons originate in the muscles and tendons and end in posterior horn of the spinal cord * Second-order nerves ascend spinocerebellar tracts and end in cerebellum providing it with feedback needed to coordinate movements * Posterior spinocerebellar tract stays ipsilateral * Anterior spinocerebellar tracts cross over and travel up contralateral side, but cross back to end in ipsilateral cerebellum

what does Descending tracts do?

carry motor signals down brainstem and spinal cord

what neurons does the descending spinal tracts use

upper motor neuron lower motor neuron

originates in cerebral cortex or brainstem and terminates on a lower motor neuron.

upper motor neuron

neurosoma is in brainstem or spinal cord. Axon leads to muscle or other target organ.

Lower motor neuron

name the descending spinal tracts

Corticospinal tract: Anterior and Lateral Reticulospinal tract Tectospinal tract Corticobulbar tract Vestibulospinal tract

what does the Corticospinal tract do?

carry signals from cerebral cortex for precise, finely coordinated movements

where does the upper motor neuron cross for corticospinal tracts

at the pyramids (ridges on anterior surface of medulla oblongata formed from fibers of this system)

state the upper, and lower motor neuron, where it crosses and synapses for Lateral corticospinal tract

UMN (from the primary motor cortex) crosses: over at the pyramids of the medulla oblongata UMN Synapses: lower motor neuron of anterior gray horn of spinal cord LMN synapses: with the skeletal muscle

state the upper, and lower motor neuron, where it crosses and synapses for Anterior corticospinal tract

UMN (from the primary motor cortex) crosses: over at the spinal cord UMN Synapses: lower motor neuron of anterior gray horn of spinal cord LMN synapses: with the skeletal muscle

state the type of sensation that is carried, for the Reticulospinal tract (lateral and medial)

- Control muscles of upper and lower limbs, especially those for posture and balance; - Contain descending analgesic pathways; reduce the transmission of pain signals to brain.

state the upper, and lower motor neuron, where it crosses and synapses for Reticulospinal tract (lateral and medial)

UMN (from the reticular formation of brainstem) DOES NOT crosses UMN (from the reticular formation of brainstem) Synapses: with lower motor neuron of anterior gray horns of spinal cord.

state the type of sensation that is carried through the Tectospinal tract

Reflex turning of head in response to sights and sounds

state the upper, and lower motor neuron, where it crosses and synapses for Tectospinal tract

UMN (from midbrain) crosses: from the primary motor cortex over at the spinal cord UMN Synapses: to contralateral side of midbrain at brainstem to lower motor neuron of cervical spinal cord

state the upper, and lower motor neuron, where it crosses and synapses for Corticobulbar tract

UMN (from the primary motor cortex) crosses: over at the lower motor neuron of cranial nerve nuclei in the brainstem UMN Synapses: at the lower motor neuron of cranial nerve nuclei in the brainstem LMN synapses: with the skeletal muscle

state the type of sensation that is carried, through the Vestibulospinal tract (lateral and medial)

Receive impulses for balance from inner ear; control extensor muscles of limbs for balance control.

state the upper, and lower motor neuron, where it crosses and synapses for Vestibulospinal tract (lateral and medial)

UMN (from brainstem vestibular nuclei) DOES NOT crosses UMN (from brainstem vestibular nuclei) Synapses: with lower motor neuron of anterior gray horns of spinal cord.

the thin sheath around a nerve axon

Neurilemma

loose connective tissue external to neurilemma

Endoneurium

layers of overlapping squamous cells that wrap fascicles: bundles of nerve fibers

Perineurium

dense irregular connective tissue that wraps entire nerve

Epineurium

cluster of neurosomas outside the CNS

Ganglion

is the sensory input to spinal cord.

Dorsal root

is motor output out of spinal cord

Ventral root

what are the divisions of the 31 pairs of spinal nerves

- 8 cervical (C1–C8): * 12 thoracic (T1–T12) * 5 lumbar (L1–L5) * 5 sacral (S1–S5) * 1 coccygeal (Co1)

innervates the anterior and lateral skin and muscles of the trunk. Gives rise to nerves of the limbs.

Ramus (anterior)

innervates the muscles and joints in that region of the spine and the skin of the back.

Ramus (posterior)

Types of nerve fibers

-Afferent fibers -Efferent fibers -Somatic fibers -Visceral fibers -General fibers: -Special fibers:

Carry signals from sensory receptors to the CNS

Afferent fibers or Sensory fibers

Carry signals from CNS to muscles and glands

Efferent fibers or Motor fibers

convey impulses for exteroreceptors of the skin

Somatic fibers

innervate blood vessels and internal organs

Visceral fibers

Function of Cervical plexus

supplies neck and phrenic nerve to the diaphragm (in the neck C1 to C5)

Function of Brachial plexus

supplies upper limb and some of shoulder and neck (near the shoulder C5 -T1)

Function of Lumbar plexus

supplies abdominal wall, anterior thigh, and genitalia (lower back L1- L4)

Function of Sacral plexus

supplies remainder of lower trunk and lower limb (pelvis, L4, L5, and S1 to S4)

Function of Coccygeal plexus

supplies the sacrotuberous ligament as well as the skin over the tailbone. (S4, S5, and Co1)

a specific area of skin that conveys sensory input to a spinal nerve

dermatome

a diagram of the cutaneous regions innervated by each spinal nerve

dermatome map

quick, involuntary, stereotyped reactions of glands or muscle to stimulation

reflex

pathway of a reflex arc

* Somatic receptors: in skin, muscles, or tendons. * Afferent nerve fibers: carry information from receptors to posterior horn of spinal cord or to the brainstem. * Integrating center: a point of synaptic contact between neurons in gray matter of cord or brainstem. Determines whether efferent neurons issue signal to muscles. * Efferent nerve fibers: carry motor impulses to muscles * Effectors: the muscles that carry out the response

stretch receptors embedded in skeletal muscles

muscle spindle

classifications of a reflex

- Development- (based on the time it develop) - Response - Complexity of circuit - Processing site- (based on where it is processed)

reflexes you are born with

innate reflexes

learned reflexes

acquired reflexes

one synapse

monosynaptic reflexes

multiple synapses

polysynaptic

processing in the spinal cord

spinal reflexes

processing in the brain

cranial reflexes

types of monosynaptic reflexes

stretch reflex

when a muscle is stretched, it “fights back” and contracts

Stretch (myotatic) reflex

type of stretch reflex

Knee-jerk (patellar) reflex

Testing somatic reflexes helps diagnose many diseases

Knee-jerk (patellar) reflex

have interneuron pathway in which signals travel over many synapses on their way to the muscle

polysynaptic reflexes

types of polysynaptic reflexes

- Flexor (Withdrawal) reflex - Crossed extensor reflex

when a muscle is stretched, it “fights back” and contracts Helps maintain equilibrium and posture

Stretch reflex

the quick contraction of flexor muscles resulting in the withdrawal of a limb from an injurious stimulus Triggers contraction of the flexors and relaxation of the extensors in that limb

Withdrawal reflex (the flexor reflex)

contraction of extensor muscles in limb opposite of the one that is withdrawn. Maintains balance by extending other leg.

Crossed extensor reflex

in response to excessive tension on the tendon. Inhibits muscle from contracting strongly Moderates muscle contraction before it tears a tendon or pulls it loose from the muscle or bone A Tendon Organ

tendon reflex