Spinal Cord, Peripheral Nervous System, And Cranial Nerves Flashcards
Structural and Nutritional Support of CNS and PNS
- CNS: astrocyte
- PNS: Satellite cells
- look at slides for what it looks like
Myelination in CNS and PNS
- CNS: oligodendrocyte
- PNS: Schwann cells/neurolemmacyte
- look at slides for what they look like
Phagocytes
- CNS: microglia
- PNS: —
- look at slides for what they look like
Line ventricles
- CNS: ependymal cells
- PNS: —
- look at slides for what they look like
Spinal Cord
- functions: sensory and motor innervation of body
- 2-way conduction of signals btw body and brain
- major center for reflexes (don’t need brain. Sensory neuron tells motor neuron to activate)
- project white matter, so axons are gonna travel in the spinal cord and are gonna conduct signals btw the body and brain
- begins at foramen magnum
- terminates at L1/L2 as conus medullaris
- Filum terminals extends from conus medullaris to coccyx; anchors spinal cord
Mixed spinal nerve
- each spinal cord segment has a mixed spinal nerve with dorsal and ventral roots
Cauda equina
- collection of spinal nerves traveling inferiorly to exit at associated intervertebral foramen
Spinal cord meninges
- epidural space: filled with fat and veins (not present in cranial cavity!) (blue things = veins)
- dura mater = toughest
- subdural space (potential space)
- arachnoid mater = spidery
- subarachnoid space filled with CSF
- Pia mater = deepest
Spinal cord segment
- the spinal cord transmits nerve signals from the motor cortex to the body, and from afferent fibers of sensory neurons to the sensory cortex of the brain
- in each segment a pair of spinal nerves is formed
- each segment corresponds w/ a vertebra
- 31 spinal cord segments
How is gray and white matter presented in spinal cords?
- gray matter = deep
- white matter = superficial
Spinal Cord Gray Matter: Posterior/dorsal horn
- receives sensory neuronal input
Spinal Cord Gray Matter: Anterior/Ventral Horn
- houses somatic motor cell bodies
- mostly skeletal muscles
Dorsal Root Ganglion
- sensory cell bodies found here
Lateral Horn
- smooth muscles (organs)
- houses visceral motor* cell bodies
Spinal Cord Roots
- roots emerge from dorsal and ventral horns
- one way pathway for neurons signals
- going out of ventral root and in thru the dorsal root
Posterior/dorsal root
- sensory (afferent) axons AND CELL BODIES found in dorsal root
Anterior Root
- motor (efferent) axons found here
- motor signals travel from cell body thru axon
Dorsal and Ventral Roots come tgthr to form a ____
- mixed spinal nerve
Mixed spinal nerve splits to form ____
- dorsal (posterior) and ventral (anterior) rami
Summary of Formation of Spinal Nerves
Spinal cord in vertebral column
- spinal nerves are named after their adjacent vertebra
- 8 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
Spinal nerves in situ
- dorsal rami: innervate muscles and skin surrounding vertebral column
- ventral rami will form plexuses
- spinal nerve travels thru intervertebral foramen
Nerve Plexuses
- a nerve plexus is a network of nerves…formed by ventral rami only
- all spinal nerves except T2-T12 (travel btw ribs and form intercostal nerves) branch and rejoin
- each muscle in a limb receives its nerve supply from more that one spinal nerve… damage to one spinal nerve cannot completely paralyze any limb muscles
Cervical Plexus
- C1-C4
- phrenic nerve (C3,C4,C5) — travel down thru our thorax and innervate a muscle called the diaphragm
- innervates the muscles of the neck and the diaphragm
Brachial Plexus
- partly in neck, partly in axilla (armpit region)
- gives rise to most nerves of the upper limb
- mixing of ventral rami (C5-C8) and most of the ventral ramus of T1
Main components of brachial plexus
- ventral rami (roots)
- trunks will form anterior and posterior divisions
- divisions split up to form cords
- cords form terminal branches
Terminal Branches of Brachial Plexus: Axillary Nerve (C5-C6)
- motor innervation: deltoid muscle (and teres minor)
- sensory innervation: shoulder joint and skin on part of deltoid (pictured below)
- sending axons to the skin, right around the area that we’re sending axons to the muscles
Terminal Branches of Brachial Plexus: Musculocutaneous nerve (C5-C7)
- motor innervation: anterior compartment of arm
- sensory innervation: skin sensation for lateral forearm
Terminal Branches of Brachial Plexus: Radial Nerve (C5-8)
- sensory innervation: skin over dorso-lateral arm, forearm, and hand
- motor innervation: posterior compartment of arm and forearm (extensors)
Terminal Branches of Brachial Plexus: Median Nerve (C5-8)
- sensory innervation: skin of lateral palm and digits 1-3 and lateral side of digit 4
- motor innervation: anterior compartment of forearm (with ulnar)
- intrinsic muscles of the thumb
Terminal Branches of Brachial Plexus: Ulnar Nerve (C8-T1)
- sensory innervation: skin of medial hand, medial side of digit 4, all of digit 5
- motor innervation: flexors and intrinsic hand muscles on ulnar side of anterior forearm
Lumbar Plexus (L1-L4)
- branches that innervate part of the skin around the genitals and part of the skin around the abdominal region
- femoral and obturator = main 2
Femoral Nerve (L2-4)
- sensory innervation: skin of antero-medial thigh and skin of medial leg and foot
- motor innervation: muscles of anterior thigh, thigh flexors, leg extensors (iliopsoas, sartorius, rectus femoris, vastus lateralis, vastus medialis (and v. intermedius))
Obturator Nerve (L2-4)
- sensory innervation: skin of medial thigh
- motor innervation: muscles of medial thigh (adductors)
> adductor longus, gracilis, adductor magnus, and adductor
brevis
Sacral Plexus
- L5-S4
- gluteal nerves
- sciatic nerve
- pudendal nerve
Gluteal Nerves
- inferior gluteal nerve (L5-S1): motor innervation = gluteus Maximus
- superior gluteal nerve (L4-S1): motor innervation = gluteus medius and minimus, tensor fascia lata
> thigh abductors
Sciatic Nerve
- L4-S3
- provide innervation to basically the whole posterior aspect of your leg
- sciatic, common fibular, tibial
Sciatic Nerve: Tibial Nerve (L4-S3)
- sensory innervation: skin of postero-lateral leg. Skin of sole of foot (subdivides into plantar nerves)
- motor innervation: muscles of posterior thing and posterior leg
- hamstring muscles = tibial nerve
Common Fibular Nerve (L4-2)
- sensory innervation: skin of antero-lateral leg, skin on dorsum of foot
- motor innervation: muscles of anterior leg (deep fibular) and muscles of lateral leg (superficial fibular)
Pudenal Nerve (S2-4)
- sensory innervation: skin of external genitalia
- motor innervation: muscles of perineum (Levator ani, coccygeus), external anal sphincter
Cranial Nerves Overview
- part of peripheral nervous system
- sensory and motor nerve fibers that innervate the head/viscera
- all of organs in our thoracic and abdominal cavities
- originate at brain or brain stem
- named in order, anterior-posterior
- 12 pairs (CN 1-CNXII)
> 3 pairs of sensory nerves
> 5 pairs of motor nerves
> 4 pairs of mixed nerves
Sensory of Cranial Nerves: CN I — Olfactory Nerve
- origin in olfactory epithelium of nasal cavity
- olfactory nerves travel thru cribriform plate
- synapse in olfactory bulb
- olfactory tract terminates in olfactory cortex (turns it in to a sensation that the brain can understand)
- neurons = collect olfactory sensations
- olfactory tract: collection if axons going to the brain
Sensory of Cranial Nerves: CN II Optic Nerve
- special sense of vision
- origin in retina of eye
- axons travel posteriorly in optic tract
- some axons cross to opposite side of brain in optic chains
- terminates in primary visual cortex (in occipital lobe) = where we make sense of this electrical signal in our retina
Sensory of Cranial Nerves: CN VIII Vestibulocochlear
- special senses of hearing and equilibrium (figuring out where you are in space if you need it balance yourself)
- origin in the inner ear (with petrous part of temporal bone)
- connects to brain stem at pons
- labyrinth (balance): filled with fluid
- cochlea (hearing): send axons into the brain
5 motor cranial nerves
- CN III, IV (4), VI (6) innervate extrinsic eye muscles
- CN XI (11) innervates sternocleidomastoid and trapezius
- CN XII (12) innervates muscles of the tongue
Motor Cranial Nerves: CN III Occulomotor
- innervates all extrinsic muscles of the eye except superior oblique and lateral rectus
- origin in the midbrain
Motor Cranial Nerves: CN IV Trochlear
- innervates superior oblique muscle
- eye look down and out
Motor Cranial Nerves: CN VI Abducens
- innervates lateral rectus (abduct the eye)
CN XI — Spinal Accessory Nerve
- sends rootlets from spinal cord up thru foramen magnum; exits again from jugular foramen
- rootlets enter cranial cavity
- innervates sternocleidomastoid and trapezius muscles
> does this after it exits jugular foramen
CN XII — Hypoglossal
- originates in medulla oblongata
- innervates muscles of tongue, including genioglossus
Mixed Cranial Nerve: CN V — Trigeminal Nerve
- sensation from the face into your brain
- motor innervation to muscles of mastification
Mixed Cranial Nerve: CN VII Facial Nerve
- conveys special sensation (taste) from the anterior 2/3 of tongue
- motor innervation to muscles of facial expression
Mixed Cranial Nerve: CN IX Glossopharyngeal Nerve
- conveys general and special sensation of taste to posterior 1/3 of tongue
- visceral sensation from carotid body -> sense blood pressure and blood gases
- motor innervation to stylopharyngeus muscle (swallowing)
- visceral motor from your salivary glands
Mixed Cranial Nerve: CN X Vagus Nerves
- wanderer
- visceral sensations to organs of thorax and abdomen
- somatic motor to muscles of larynx (speaking) and pharynx (swallowing)
- visceral motor (parasympathetic) to thoracic and abdomen
CN V — Trigeminal Nerve
- has three divisions
- V1 Opthalmic Division of Trigeminal Nerve
- V2 Maxillary Division Of Trigeminal Nerve
- V3 Mandibular Division of Trigeminal Nerve
V1 Opthalmic Division of Trigeminal Nerve
- sensation to forehead, upper eyelid, cornea, bridge of nose
V2 Maxillary Division of Trigeminal Nerve
- sensation to bottom eyelid, side of nose, upper lip, maxillary region
V3 Mandibular Division of Trigeminal Nerve
- sensation to side of temple, side of ace (cheek), bottom lip and chin, mandibular teeth and anterior 2/3 tongue
- motor innervation to muscles of mastification (masseter, temporalis, pterygoids)
CN VII - Facial Nerve
- motor to muscles of facial expression
- visceral motor (parasympathetic) to lacrimal gland (tears) and sublingual and submandibular glands
- taste (special sense) from anterior 2/3 of tongue
CN IX Glossopharyngeal
- motor to stylopharyngeus muscle (swallowing)
- visceral sensory to carotid body and sinus (senses blood chemistry
- general sensory to pharynx, posterior 1/3 of tongue (if you swallow hot coffee and it burns)
- taste and general sense to posterior 1/3 of tongue (bitter taste, sweetness, sour, etc)
- visceral motor to parotid gland (saliva) (what makes our mouth water with food)
CN X Vagus
- wanders all over the body
- somatic motor to larynx and pharynx (speaking and swallowing)
- visceral sensory to organs of thorax and abdomen (what makes us feel cramps or gas pain or a feeling of fullness)
- visceral motor (parasympathetic) to organs of thorax and abdomen
> what tells our stomach to speed up or slow down digestion, tells our heart to beat faster, or tells our lungs to dilates and allow more air to get in