Peripheral Nervous System Flashcards
Define “ganglion”
A cluster of cell bodies outside of the CNS; enveloped in an epineurium
Describe the dorsal root ganglia
Ganglia a short distance away from the spinal cord; contain neurosomas (cell bodies) of sensory neurons
Describe the sympathetic ganglia
Neurosomas that lie laterally to the vertebral body; responsible for carrying motor information
Name the twelve cranial nerves
I: Olfactory
II: Optic
III: Oculomotor
IV: Trochlear
V: Trigeminal
VI: Abducens
VII: Facial
VIII: Vestibulocochlear
IX: Glossopharyngeal
X: Vagus
XI: Accessory
XII: Hypoglossal
Describe cranial nerve I. Name? Function? Origin? Termination?
Name: Olfactory nerve
Function: sensory; contains “fascicles”, or projections from the olfactory bulb through the ethmoid bone into the nasal cavity
Origin: Olfactory mucosa in nasal cavity
Termination: Olfactory bulb
Describe cranial nerve II. Name? Function? Origin? Termination?
Name: Optic nerve
Function: Sensory; responsible for relaying visual information from the retina to the thalamus and midbrain at the optic chiasm; ultimately leads to occipital lobe
Origin: Retina
Termination: Thalamus and midbrain
Describe cranial nerve III. Name? Function? Origin? Termination?
Name: Oculomotor
Function: Predominantly motor responsible for opening of eyelid, pupillary constriction, and focusing
Origin: Midbrain
Termination: somatic fibers to levator palpebrae superioris; superior, medial, and inferior rectus muscles, and inferior oblique of the eye; autonomic fibers enter eyeball and lead to constrictor of iris and ciliary muscle of lens
Describe cranial nerve IV. Name? Function? Origin? Termination?
Name: Trochlear
Function: Predominantly motor; responsible for medial eye movements
Origin: Midbrain
Termination: superior oblique muscle of contralateral eye
Describe cranial nerve V. Name? Function? Subdivisions?
Name: Trigeminal
Function: Mixed nerve for sensation and chewing
3 divisions: V1 = opthalmic; V2 = maxillary; V3 = Mandibular
Describe subdivision V1 of the trigeminal nerve. Name? Function? Origin? Termination?
Name: Ophthalmic
Function: touch, temperature, pain, and sensation from upper face
Origin: superior region of the face; surface of eyeball; lacrimal gland; superior nasal mucosa; frontal and ethmoid sinuses
Termination: Pons
Describe subdivision V2 of the trigeminal nerve. Name? Function? Origin? Termination?
Name: Maxillary
Function: Touch, temperature, and pain from the lower face
Origin: Middle region of the face; nasal mucosa; maxillary sinus; palate; upper teeth and gums
Termination: Pons
Describe subdivision V3 of the trigeminal nerve. Name? Function? Origins? Terminations?
Name: Mandibular
Function: Mixed; some sensory for the lower face; motor for mastication (chewing)
Sensory origin: Inferior region of the face, anterior 2/3 of tongue (not taste buds), lower teeth and gums, floor of mouth, and dura mater
Sensory termination: Pons
Motor origin: Pons
Motor termination: Anterior belly of digastric; masseter, temporalis, mylohyoid, and pterygoid muscles; tensor tympani muscle of inner ear
Describe cranial nerve VI. Name? Function? Origin? Termination?
Name: Abducens
Function: Lateral eye movement
Origin: Inferior pons
Termination: Lateral rectus muscle of the eye
Describe cranial nerve VII. Name? Function? Origins? Terminations?
Name: Facial
Function: Mixed; taste; facial expression; secretion of tears, saliva, nasal, and oral mucus
Sensory origin: taste buds of anterior 2/3 of tongue
Sensory termination: Thalamus
Motor origin: pons
Motor termination: somatic fibers of digastric muscle, stapedius muscle of middle ear, stylohyoid muscle, muscles of facial expression. Autonomic fibers to submandibular and sublingual salivary glands, tear glands, nasal and palatine glands
What are the five subdivisions of the facial nerve (CN VII)?
Temporal
Zygomatic
Buccal
Mandibular
Cervical
Describe cranial nerve VIII. Name? Function? Origins? Terminations?
Name: Vestibulocochlear
Function: Predominantly sensory; hearing and equilibrium
Sensory origin: cochlea, vestibule, and semicircular ducts
Sensory termination: Fibers for hearing end in medulla; fibers for equilibrium end at junction of medulla and pons
Motor origin: Pons
Motor termination: Outer hair cells of cochlea of inner ear
Describe cranial nerve IX. Name? Function? Origins? Terminations?
Name: Glossopharyngeal
Function: Mixed; senses taste, touch, pressure, pain, and temperature on tongue and outer ear; regulates blood pressure and respiration; motor controls salivation, swallowing, and gagging
Sensory origin: pharynx; middle and outer ear; posterior 1/3 (including tastebuds) of tongue; internal carotid artery
Sensory termination: Medulla oblongata
Motor origin: Medulla oblongata
Motor termination: Parotid salivary gland; glands of posterior tongue; stylopharyngeal muscle (dilates pharynx for swallowing)
Describe cranial nerve X. Name? Function? Origins? Terminations?
Name: Vagus
Function: senses taste, hunger, fullness, and gastrointestinal discomfort; responsible for swallowing, speech, deceleration of heart, bronchoconstriction, gastrointestinal secretion and motility
Sensory Origin: Thoracic and abdominal viscera, root of tongue, pharynx, larynx, epiglottis, outer ear, dura mater
Sensory Termination: Medulla oblongata
Motor Origin: Medulla oblongata
Motor Termination: tongue, palate, pharynx, and most other internal organs
Describe cranial nerve XI. Name? Function? Origin? Termination?
Name: Accessory
Function: primarily motor; swallowing; head, neck, and shoulder movements
Origin: Medulla oblongata and spinal cord segments C1-C6
Termination: Palate; pharynx; trapezius and sternocleidomastoid muscles
“wanna be spinal nerve”
Describe cranial nerve XII. Name? Function? Origin? Termination?
Name: Hypoglossal
Function: Primarily motor; tongue movements of speech, food manipulation, and swallowing
Origin: Medulla oblongata
Termination: Intrinsic and extrinsic muscles of the tongue
Define plexus
A network of intersecting nerve fibers that serve the same part of the body
How many PAIRS of spinal nerves are there and what are their subdivisions?
31 pairs
C1-C8
T1-T12
L1-L5
S1-S5
Co1
Describe the proximal branches of spinal nerves. Where do they emerge? What kind of nerves are they? What structures are associated with it?
6-8 rootlets emerge from the anterior surface on either side of the spinal cord to form the ventral root (and posterior rootlets form the dorsal roots)
Dorsal root ganglia lie just distal to the point where posterior rootlets converge; sensory
Dorsal and ventral roots merge just beyond dorsal root ganglion and exits the vertebral canal through the intervertebral foramen
Describe the distal branches of spinal nerves
Begin immediately after emerging from the intervertebral foramen
Divides into posterior and anterior rami as well as a small meningeal branch (detects swelling at the spinal cord)
Describe the intercostal nerves
Nerves that arise from anterior rami of thoracic spinal nerves; travel along the inferior margin of a rib
Responsible for innervation of the skin and intercostal muscles, thus contributing to breathing; also innervate internal oblique, external oblique, and transverse abdominal muscles
Describe the cervical plexus. What are its somatosensory and motor innervations?
Composition: nerves C1-C5
Somatosensory innervation: ears, neck, mandible, chin, shoulders, chest
Motor innervation: Hyoid muscles
What does the axillary nerve innervate?
Sensory: skin of lateral shoulder and arm; shoulder joint
Motor: Deltoid and teres minor muscles
What does the musculocutaneous nerve innervate?
Sensory: skin of anterolateral forearm; elbow joint
Motor: brachialis, biceps brachii, and coracobrachialis muscles
What does the median nerve innervate?
Sensory: Joints and skin of the hand (half of thumb, index, middle, and half of ring fingers)
Motor: Brachialis, biceps brachii, and coracobrachialis muscles
What does the ulnar nerve innervate?
Sensory: joint of elbow and hand; skin of half of ring and pinky fingers, as well as the medial half of the palm and back of hand
Motor: some forearm flexors; adductor pollicis; hypothenar group; interosseous muscles; lumbricles III-IV
What does the radial nerve innervate?
Sensory: joints of elbow, wrist, and hand; skin of posterior arm, posterior and lateral forearm; skin of back of thumb and back of lateral hand
Motor: Mainly extensor muscles of posterior arm and forearm
Describe the phrenic nerve. What type of nerve is it? What does it innervate? What plexus does it emerge from?
Mixed nerve
Major nerve that innervates the diaphragm and is essential for breathing; also innervates the pleura and pericardium
Arises from the cervical plexus
Describe the iliohypogastric nerve. What type of nerve is it and what does it innervate?
Mixed nerve
Sensory innervation: skin of lower anterior abdominal and posterolateral gluteal regions
Motor innervation: internal and external oblique and transverse abdominal muscles
Describe the ilioinguinal nerve. What type of nerve is it and what does it innervate?
Mixed nerve of the lumbar plexus
Sensory innervation: skin of upper medial thigh; male scrotum and root of penis; female labia majora
Motor innervation: internal oblique
Describe the genitofemoral nerve. What type of nerve is it and what does it innervate?
Mixed nerve of lumbar plexus
Sensory innervation: skin of middle anterior thigh; male scrotum; female labia majora
Motor innervation: Male cremaster muscle (surrounds testis; pulls them closer to the body when cold)
Describe the lateral femoral cutaneous nerve. What type of nerve is it and what are its innervations?
Somatosensory nerve of the lumbar plexus
Sensory innervations: skin of anterior and upper lateral thigh
Describe the femoral nerve. What type of nerve is it and what are its innervations?
Mixed nerve of the lumbar plexus
Sensory innervation: skin of anterior, medial, and lateral thigh and knee; skin of medial leg and foot; hip and knee joints
Motor innervations: iliacus, pectineus, quadriceps femoris, and sartorious muscles
Describe the obturator nerve. What type of nerve is it and what are its innervations?
Mixed nerve of the lumbar plexus; passes through obturator foramen in pelvis
Sensory innervations: Skin of medial thigh; hip and knee joints
Motor innervations: obturator externus; medial (adductor) thigh muscles
What spinal nerves give rise to the sacral and coccygeal plexuses
L4, L5, S1-S5, Co1
Describe the sciatic nerve. What does it innervate? What nerves does it give rise to?
Innervates hamstring and muscles of the leg and foot
Gives rise to tibial nerve (innervates medial and posterior leg) and common fibular nerve (innervates lateral lower leg)
What is a dermatome?
Area of skin innervated by cutaneous branches of a spinal nerve
All spinal nerves except C1 participate in dermatomes
Some spinal nerves overlap on dermatome
