A&P ch 13, the Peripheral Nervous System

what does the peripheral nervous system do?

gathers input from sensory receptors and sends motor output to effectors

what is considered a part of the PNS

everything coming directly off the brain and spinal cord

how many nerve pairs are there

12 cranial and 31 spinal nerves

how are receptors classified?

by type of stimulus, body location, and structural complexity

what is a mechanoreceptor

detects touch, pressure, vibration and stretch

what is a thermoreceptor

detects temperature

what is a photoreceptor

detects light

what is a chemoreceptor

detects chemical balance

what is a noicepter

detects pain

what is a proprioceptor

moniters stretch in skeletal muscle, tendons, joints, connective tissue coverings; you know where your body parts are without looking at them

what are some nonencapsulated roots

free nerve endings, Merkel discs (light touch), and hair follicle receptors

what are some encapsulated receptors

found mostly in skin; Meissners corpuscles, Pacinian corpuscles, Ruffinis endings, Muscle spindles, tendon organs, joint kinesthetic

how are somatic afferent senses processed?

3 orders: first order—PNS, conducts from spinal cord to medulla
second order—CNS, from medulla to thalamus/cerebellum
third order—CNS, from thalamus to somatosensory cortex

how are somatic efferent pathways out?

two parts:

upper motor neuron—from brain to spinal cord
lower motor neuron—spinal cord to the effect in the body

how are cranial nerves classified?

based on the direction they transmit impulses: sensory, motor, or mixed

how are the cranial nerves ordered?

they are ordered rostrally (from the nose) to caudally (back of the head, near the spinal cord)

Cranial Nerve I: olfactory

sensory, smell, through cribriform plate

Cranial nerve II: optic

sensory, vision, from the back of the eye→partially cross at optic chiasma→goes through thalamus and to occipital cortex

Cranial Nerve III: oculomotor

Motor eye movement, fibers run from midbrain through superior orbital fissures to four of six eye muscles

Cranial Nerve IV: trochlear

motor, through superior orbital fissure, passes through trochlea; eye’s superior oblique muscle

Cranial Nerve V: trigeminal

; mixed, three divisions (one passes through sup. orb. fis), senses oral and nasal cavities, moves for chewing

Cranial Nerve VI: Abducens

; motor, eye movement, fibers enter orbits through sup orb fis, innervates lateral rectus muscle

Cranial Nerve VII: facial

mixed, muscles for face, five branches, senses front 2/3 of tongue, moves facial expressions

what are the names of the five branches of the Facial Nerve

cervical, mandibular, buccal, zygomatic, temporal

Cranial Nerve VIII: vestibulocochlear

; sensory, hearing, balance/equilibrium, runs through cochlea

Cranial Nerve IX: glossopharyngeal

mixed, swallowing throat and sensing back 1/3 of tongue, fibers run through jugular foramen

Cranial Nerve X: vagus

; mixed, automatic controller of all chest and abdominal organs, extends beyond head and neck

Cranial Nerve XI: accessory

motor, moves head, neck and shoulders, rootlets pass cranium via foramen magnum

Cranial Nerve XII: hypoglossal

mixed, motor in tongue, talking and swallowing, fibers run through medulla and through hypoglossal canal

Are the spinal nerves sensory, motor, or mixed?

mixed

What are the sections of spinal nerves

cervical, thoracic, lumbar, sacral, and coccygeal

how many spinal nerves are in each section?

8 cervical

12 thoracic

5 lumbar

5 sacral

1 coccygeal

how is each spinal nerve connected to the cord?

via the ventral and dorsal roots

what are rami

connect to nerve; supply entire body from neck down, dorsal rami supply back body trunk (shorter) and ventral rami supply the front truck and limbs (longer)

what is a plexus

a bundle of branching nerves, they are named cervical, brachial, lumbar, sacral, and coccygeal

which section of the ventral rami does NOT form a plexus?

T2-T12

what is the cervical plexus

C1-C5, innervates skin in the neck, ear, back of head, and shoulders

what is the brachial plexus

C5-T1; innervates upper limb, travels down from neck through arm (five major branches)

what are the five major branches of the brachial plexus?

axillary, musculocutaneous, median, ulnar, and radial

what is the lumbar plexus

L1-L4; innervates thigh an abdominal wall

what are two nerves in the lumbar plexus

Femoral—quads

Obturator—adductors

what is the sacral plexus

L5-S5; innervates posterior thigh, hamstrings, lower leg, foot and part of the pelvis

what are the two nerves associated with the sacral plexus?

Sciatic—hammies and adductor magnus

Pudendal—external genetalia

what are dermatomes

innervates skin by cutaneous branches of all spinal nerves except C1, helps locate specific problem on the surface of the body

what are motor endings and motor activity

connect nerves to their effectors, PNS elements that activate effectores by releasing neurotransmitters

skeletal muscle: ACh

smooth muscle: slow release

what are the classifications of reflexes

Development—innate reflexes and acquires reflexes
Response—somatic reflexes and visceral reflexes
Complexity of Circuit—monosynaptic and polysynaptic
Processing site—spinal and cranial reflexes