Lecture 5: Peripheral Nervous System Flashcards by Elle Chapman

Components of the CNS

brain, brainstem and spinal cord

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Components of the PNS

Nerves and ganglia outside the CNS
-somatic and autonomic

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how many pairs of spinal nerves are there

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how many pairs of cranial nerves are there

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Somatic NS

voluntary; the division of the PNS that includes sensory and motor neurons

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Sensory (Afferent) neurons

-send signals from outside world to brain
-convey input from receptor for somatic and special senses

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Somatic Motor (efferent) neurons

-send signals from brain to outside world
-innervate skeletal muscles

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Autonomic NS

Involuntary
-regulates cardiac muscle, smooth muscle and glandular tissue
-autonomic motor neurons regulate visceral activities by exciting or inhibiting activities in effector tissues

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Afferent divisions of the PNS

Somatic sensory and visceral sensory

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Somatic Sensory

carries signals from receptors in skin, muscles, bones and joints

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Visceral Sensory

carries signals mainly from organs in the thoracic and abdominal cavities

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Neuron system of somatic

-direct highway
-fully myleinated
-1 neuron system

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Neuron system of Autonomic

-2 neuron system
-preganglionic neuron and postganglionic neruon
-preganglionic is mylinated
-postganglionic is unmylinated
-synapse occurs at ganglion

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major difference between CNS and PNS

the CNS is composed by the spinal cord and the PNS is composed by cranial nerves

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Which of the following sensory responses is not a part of the Somatic Sensory division?

a) Proprioception
b)Taste
c)Pressure
d)Vision

Taste

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General Sensory Receptors by Structural Class

Free nerve endings
Encapsulated
Proprioceptors

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Free nerve endings of sensory neurons: Functional Class by stimulus type

Nociceptors, thermoreceptors, mechanoreceptors, and chemoreceptors

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Free nerve endings of sensory neurons: Body Location

MOST body tissues: most dense in connective tissues

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Modified free nerve endings (Merkel discs): Functional Class by Stimulus Type

mechanoreceptors (light pressure)

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Modified free nerve endings (merkel discs): body location

deepest layer of the epidermis

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Hair Follicle Receptors: Functional Class

Mechanoreceptors (hair deflection)

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Hair Follicle Receptors: Body Location

In and surrounding hair follicles

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Tactile (Meissner’s) corpuscles: Functional Class by Stimulus Type

Mechanoreceptors (light pressure, discriminative touch, vibration of low frequency)

**detects how many objects are touching your skin at a time

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Tactile (Meissner’s) corpuscles: Body Location

Hairless skin, particularly nipples, external genitalia, fingertips, eyelids

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Sensory receptors: Free nerve endings

-Free Nerve endings of sensory neurons -Modified free nerve endings (Merkel discs) -Hair Follicle Receptors

Sensory Receptors: Encapsulated

-Tactile (Meissner's) Corpuscles -Lamellar (Pacinian) corpuscles -RUffini Corpuscles

Sensory Receptors: Proprioceptors

-muscle spindles -Tendon Organs

Lamellar (Pacinian) corpuscles: Functional Class by Stimulus Type

-Mechanoreceptors (deep pressure, stretch, vibration of high frequency)

Lamellar (Pacinian) corpuscles: Body Location

Dermis and hypodermis; most abundant on fingers, soles of feet, external genitalia, nipples

Ruffini Corpuscles: Functional Class by Stimulus Type

Mechanoreceptors (deep pressure and stretch)

Ruffini Corpuscles: Body location

deep in dermis, hypodermis and joint capsules

Muscle Spindles: Functional class by stimulus type

Mechanoreceptors (muscle stretch)

Muscle Spindles: Body Location

Skeletal muscles, particularly those of the extremeties

Tendon Organs: Functional Class by stimulus type

machanoreceptor (tendon stretch)

Tendon organs: Body location

tendons (at ends of muscles)

Which of the following is responsible for sensing proprioception? a) free nerve endings b)merkel cells c) muscle spindles d) hair follicle recpeptor

C) muscle spindles

true or false: Pacinian corpuscles are responsible for sensing deep pressure?

true

Breakdown of the vertebrae

7 cervical 12 thoracic 5 lumbar 5 sacral 3-5 coccygeal

Purpose of spinal nerves

-communication system between brain and various body parts -essential for voluntary and involuntary actions -highway for sensory and motor integrations -important for rapid automatic responses through reflexes

3 parts of the anatomy of the spinal nerve

-Epineurium -Perinrurium -Endonerurium

what are fasicles

bundles of axons

how many pairs of spinal nerves are there

Which pairs of spinal nerves leave the spinal cord ABOVE their corresponding vertebrae level?

1-7

Each spinal nerve connects to the spinal cord through:

dorsal root via dorsal rootlets

Dorsal root

contains axonal processes of sensory neurons arising from posterior horn

The dorsal root contains:

the dorsal root ganglion -enlargement of the dorsal root -cluster of cell bodies of sensory neurons -functions as sensory relay stations by processing and modulating sneosry signal before reaching the CNS

The spinal nerve and the dorsal root gagnglion lie within the

intervertebral foramina

Ventral root

contains axonal processes of motor neurons whose cell bodies are located in the anterior horn of the spinal cord

ventral root connects to the spinal cord via

ventral rootlets

each spinal nerve branches into a:

dorsal and ventral ramus

WHich type of fibers do the dorsal and ventral rami contain

sensory and motor

what do the dorsal and ventral rami supply?

exit through intervertebral foramina to supply the entire somatic region of the body

Dorsal Rami

supplies dorsum of the neck and back

Ventral rami

-supplies anterior and lateral regions of neck and trunk -supplies all regions of the limbs -much thicker than dorsal rami

ventral rami branch into

nerve plexuses

how many primary nerve plexuses does the ventral rami form and what do they target

4 -travel to specific target tissues, such as muscles, skin, and organs to facilitare motor control and sensory perception

four main plexuses

cervical, brachial, lumbar, sacral

Cervical Plexus

-spinal nerves C1-C4 -supply sensory & motor innervation to the neck and proportions of the head

Brachial Plexus

-supply nerves C5-T1 -supply sensory & motor innervation to shoulder and upper limbs

Lumbar Plexus

-Spinal nerves L1-L4 -supplies nerves to the lower back, abdominal wall, and part of the lower limb

Sacral Plexus

-spinal nerves L4-S5 -innervates the buttocks, pelvic structures and the remainder of the lower limb

The path from the spinal cord

1. Nerves originate from the spinal cord through two roots: dorsal and ventral 2. Dorsal and Ventral roots unite outside the spinal cord to form a spinal nerve 3. THe spinal nerve branches into two rami: dorsal and ventral

path of dorsal roots information

carrying sensory information into the spinal cord

path of ventral roots information

carrying motor information away from the spinal cord

which of the following plexus is responsible for innervation of the upper limbs

brachial

which anatomical structure of the spinal nerve has both sensory and motor components

ventral rami

What are dermatomes

-sctions of the skin innervated by a single spinal nerve -motor and sensory innervation for those specific areas

important dermatones

T4: nipples T10: Umbillicus

Motor Reflex Arc

-neural pathway that mediates rapid involuntary actions -integrates sensory inputs and motor outputs -physiological and nural response against potential harmful stimuli

Pathway of the motor reflex arc

1. Sensory Receptor 2. Sensory neuron (afferent) 3. Dorsal Root ganglion 4. Dorsal Root 5. Posterior Horn 6. Interneurons 7. ANterior Hron 8. Motor Neuron (efferent) 9. Effector Muscle