Peripheral nervous system Flashcards
What are the three layers of CT in a nerve?
Endoneurium-surrounds individual axons
Perineurium-surrounds bundles of axons called fascicles
Epineurium-surrounds entire nerve
Olfactory nerve (CNI)
- Carries sense of smell
- sensory
- cribiform foramina
Optic nerve (CNII)
- carries sense of vision
- sensory
- Optic Canal
Oculomotor nerve (CNIII)
- Excites most extraocular muscle (medial rectus, s. rectus, i. rectus, and inferior oblique), excites levator palpebrae superioris, carries parasympathetic efferent fibers that stimulate intraocular muscles (ciliary muscles and circular pupillary constrictor muscles of the iris)
- Motor
- Superior orbital fissure
Trochlear nerve (CNIV)
- Excites the superior oblique extraocular muscles
- Motor
- Superior orbital fissure
Trigeminal nerve (CNV)
- Carries the sense of touch from the face
- excites the muscles of mastication including the masseter and temporalis
- Both sensory and motor
- Consists of three branches- opthalmic, maxillary, and mandibular
Opthalmic branch of trigeminal
- Sensory info from superior facial region including orbits
* Superior orbital fissure
Maxillary branch of trigeminal
- Sensory infor from middle facial skin including superior oral region
- Foramen rotundum
Mandibular branch of trigeminal
- Motor info to masseter and temporalis
* Foramen ovale
Abducens nerve (CNVI)
- Excites lateral rectus extraocular muscles
- Motor
- Superior orbital fissure
Facial nerve (CNVII)
- carries sense of taste from the anterior 2/3 of the tongue
- excites the muscles of facial expression including frontalis, orbicularis oris, orbicularis oculi, depressor anguli oris, depressor labii inferioris
- carries parasympathetic efferent fibers that stimulate the lacrimal gland, sublingual salivary gland and submandibular salivary gland
- Both sensory and motor
- Internal acoustic meatus and stylomastoid foramen
Vestibulocochlear nerve (CNVIII)
- carries sense of hearing
- Sensory
- Internal acoustic meatus
Glossopharyngeal nerve (CVIX)
- carries sense of taste from the posterior 1/3 of the tongue
- sense of touch from the posterior tongue and pharynx *sense of blood pressure and sense of blood gas concentrations from arterial baroreceptors and chemoreceptors located in the carotid sinus
- excites muscles of the pharynx important for swallowing
- carries parasympathetic efferent fibers that stimulate the parotid salivary gland
- Both sensory and motor
- Jugular foramen
Vagus nerve (CNX)
- carries sensory info from visceral organs
- sense of blood pressure and gas concentrations from arterial baroreceptors and chemoreceptors in the aortic arch
- carries the majority of parasympathetic efferent fibers that regulate visceral organs
- Both sensory and motor
- Jugular foramen
Accessory nerve (CNXI)
- Excites trapezius and deltoids
- Motor
- Jugular foramen
Hypoglossal nerve (CNXII)
- Excites muscle that move the tongue including genioglossus, hyoglossus, and styloglossus
- Motor
- Hypoglossal canal
Ganglia
gray matter in PNS
Dorsal root ganglia
bulge on dorsal root
- contains soma of pseudounipolar sensory neurons
- Afferent fibers travel in to the spinal cord through the dorsal root
Trunk of spinal nerve
*Formed by the fusion of ventral and dorsal nerve roots
Dorsal ramus
Small branch that curves posteriorly and innervates the skin and muscles of the posterior regions of the body
Ventral ramus
Large branch that curves anteriorly and innervates the anterior trunk and limbs
Plexus
Interlacing nerve network formed by several ventral rami that join together then branch again
Cervical plexus
Forms from C1-C5
*innervates skin and muscles of the neck and shoulder
Phrenic nerve
- cervical plexus
- Forms from ventral rami of C3-C5
- excites the diaphragm
Brachial plexus
- Forms from C5-T1
- Innervates pectoral girdle and arm
- Spinal trunks C5-T1 are called roots of the brachial plexus that converge to from 3 trunks, each runk divides into 2 divisions, these 6 divisions unite to form 3 cords
What are the 3 trunks of the brachial plexus?
Superior (C5-C6), Middle (C7), and Inferior (C8-T1)
What are the 2 divisions of the brachial plexus?
Anterior and posterior divisions
What are the 3 cords of the brachial plexus?
Lateral, medial and posterior cord
*cords give rise to branches of the brachial plexus that form the specific peripheral nerves that travel through the upper limb
Lateral cord of brachial plexus
formed from anterior divisions of superior and middle trunks
Medial cord of brachial plexus
formed by anterior division of inferior trunk
Posterior cord of brachial plexus
formed by union of all 3 posterior divisions
Ulnar nerve
- Travels down medial brachial and antebrachial regions
- Innervates flexors of medial forearm and hand, flexor carpi ulnaris, flexor digitorum profundus
- Forms from C8-T1 by way of MEDIAL cord
Median nerve
- Travels down the anterior brachial and antebrachial regions just lateral to the ulnar nerve
- Innervates flexors of lateral forearm and hand, flexor carpi radialis, flexor digitorum superficialis
- Forms from C6-T1 by way of LATERAL and MEDIAL cords
Musculocutaneous nerve
- travels down the anterior of the brachial region deep to biceps brachii and superficial to brachialis
- Innervates flexor arm muscles, biceps brachii, and brachialis
- Forms from C5-C7 by way of LATERAL cord
Radial nerve
- travels down posterior lateral brachial and antebrachial regions
- Innervates arm and forearm extensor muscles, extensor carpi or digitorum
- forms from C5-T1 by way of the POSTERIOR cord
Axillary nerve
- Travels through axillary region
- Innervates deltoid, teres minor
- Forms from C5-C6 by way of POSTERIOR cord
Lumbar plexus
T12-L4
*Innervates lower abdomen, medial and anterior portions of the thigh
Femoral nerve
*Lumbar plexus
Travels down anterior femoral region (thigh)
*Innervates quadriceps femoris
*Forms from L2-L4
Obturator nerve
*lumbar plexus
Travels down medial femoral region
*Innervates adductor magnus and longus
*Forms from L2-L4
Sacral plexus
L4-S4
*Innervates lateral and posterior portions of femoral and sural regions
Sciatic nerve
- sacral plexus
- largest nerve in the body, travels down the posterior femoral region
- excites hamstrings
- Forms from L4-S3-branches to form tibial nerve and common fibular nerve
Tibial nerve
Innervates posterior compartment of lower leg-gastrocnemius and soleus
Common fibular nerve
Branches into superficial fibular nerve and deep fibular nerve
Superficial fibular nerve
Innervates lateral compartment of leg- fibularis longus and brevis muscles
Deep fibular nerve
Innervates anterior compartment of lower leg-dorsi flexors and toe extensors, tibialis anterior, extensor digitorum longus
Somatic nervous system
Controls skeletal muscles
- Voluntary
- Muscles must be excited or they are inactive
- One motor neuron extends from the CNS all the way to the effector muscle
Autonomic nervous system
Regulates glands, smooth and cardiac muscles
- Involuntary
- Two neuron chain between the CNS and the effector
- preganglionic neuron-cell body lies in the CNS and axon extends to an autonomic ganglia in the PNS (myelinated)
- Postganglionic neuron-cell body lies in autonomic ganglia and axon extends to effector organ (unmyelinated)
Sympathetic autonomic division
Fight or flight, enables body to cope rapidly when excited, frightened, or during exercise and emergency situations
- Increases heart rate and blood pressure
- Activates sweat glands
- Pupils dilate
- liver releases glucose to meet increased energy needs
Parasympathetic autonomic division
Rest and digest, dominant in nonstressful situations, conserves energy and directs maintenance activities such as digestion and excretion
- Blood to visceral organs-increase digestive tract mobility
- Pupil constriction
- Glandular secretion-digestive
- BP,HR and respiratory rates are at low normal levels
Thoracolumbar region
- sympathetic division
- preganglionic fibers emerge from thoracic and lumbar spinal nerve roots (T1-L2)
- Short preganglionic fibers
- Long postganglionic fibers
Chain ganglia or paravertebral ganglia
lateral to bodies of thoracic and lumbar vertebrae
- contains soma of postganglionic sympathetic motor neurons that are postsynaptic to preganglionic sympathetic motor neurons
- Sympathetic efferent fibers travel from the lateral gray horn of the spinal cord out through the ventral root, then through the white ramus connecting to ganglion
Collateral ganglia or prevertebral ganglia
Anterior to the vertebral column
Adrenal medulla
Endocrine gland directly stimulated by preganglionic sympathetic fibers
*These cells release epinephrine (adrenaline) and norepinephrine (noradrenaline) into the blood stream to function as hormones
Craniosacral origin
- parasympathetic division
- preganglionic fibers emerge from brainstem and sacral regions through cranial nerves and sacral spinal nerves
- Long preganglionic fibers
- Short postganglionic fibers
- Ganglia close to target organ
Terminal ganglia
very close to target organ
Intramural ganglia
within the walls of the target organ
