CNS and PNS Flashcards
What does myelinated and unmyelinated mean (plus difference in PNS and CNS)
Covered in myelin or not
In CNS myelinated fibres oligodendrocytes (white matter- fatty)
In PNS by Schwann cells)
What are the largest and smallest peripheral nerves
Largest are motor and proprioception 12-20um
Smallest are postgang autonomic or sensory
What makes up spinal nerve root
Anterior (ventral) and posterior (dorsal) root attached at either side of cord by rootlets within intervertebral foramen
Anterior= motor or efferent for skeletal (T1-L2 and S2-S4 also autonomic fibres) plus unmyelinated afferent pain fibres which have doubled back from posterior root
Posterior= sensory or afferent. Unipolar and pass to peripheral nerves or CNS. No synapses in posterior root ganglia
After forming nerve the ANTERIOR roots (larger) form great plexus aka cervical, brachial, lumar and sacral.
POSTERIOR RAMI DO NOT FORM PLEXUS
Fascicles and single nerves coverings
Surrounded by Perineurium and epineurium respectively
What muscles do posterior rami supply
All trunk (erector spinae and transversospinalis deep to thoracocolumbar fascia and levator costae) plus splenius and deep neck muscles.
Post rami divides into medial and lateral branch to supply muscles, only one branch reaches skin.
In upper half thorax medial post rami supply cutaneous branches
In rest of body lateral branches of post rami provide cutaneous branches
C1 has no cutaneous branch
NO POST RAMI EVER SUPPLIES SKIN OR MUSCLE OF A LIMB!
Do spinal nerves carry any SNS supply
Yes every spinal nerve without exception carries post ganglionic, unmyelinated, SNS which hitchhike along nerve to provide vasoconstrictor function etc for temp regulation
What rami supplied flexor and extensor
Anterior= flexors
Posterior= extensors
Both + skin
Where are there PSNS fibres
All parts of body get SNS but only viscera have PSNS EXCEPT gonads and adrenals who have only SNS
Sacral PSNS
Preganglionic fibres in lateral grey horn of S2-S4
Constitute pelvic splanchnic nerves
Leave anterior rami of sacral nerves near anterior sacral foramina and pass forwards to enter inferior hypogastric plexus
Then run into pelvic viscera to hindgut as far as splenic flexure
Synapse around postganglionic cell bodies in walls of these viscera
Cranial PSNS ganglia
Ciliary
Pterygopalatine
Submandibular
Otic
All have PSNS (preganglionic fibres from brainstem nucleus) SNS and sensory roots
CILIARY
PSNS root from Edinger-Westphal nucleus CN III carried ny branch of IO muscle (inferior CNIII)
SNS root from superior cervical ganglion by ICA plexus
Sensory root from branch of nasociliary nerve with CN V cell bodes
Branches short ciliary nerves of eye
Pterygopalatine ganglion
PSNS root from superior salivary nucleus by nervus intermedius (CN VII) greater pretrosal nerve and nerve of pterygoid canal
SNS root from superior cervical ganglion by ICA plexus, deep petrosal nerve and nerve of pterygoid canal
Sensory root from branches of maxillary nerve with cell bodies in trigeminal ganglion
Branches to lacrimal gland via zygomatic and lacrimal nerves, to mucous glands in nose, nasopharynx, palate via maxillary nerve branches. Taste fibres to palate via greater petrosal nerve and cell bodes in geniculate ganglion of CN VII
Submandibular
PSNS root superior salivary nucleus by nervus intermedius CN VII, chorda tympani and lingual nerve
SNS superior cervical ganglion by facial artery
Sensory Branch of lingual nerve with cell bodies of trigeminal ganglion
Branches to submandibular and sublingual glands via branches of lingual nerve
Otic ganglion
PSNS root from inferior salivary nucleus via glossopharyngeal nerve tympanic branch, tympanic plexus and lesser petrosal nerve
SNS root from superior cervical ganglion by fibres with middle meningeal artery
Sensory from auriculotemporal nerve with cell bodies from trigeminal ganglion
Branches to parotid via auriculotemporal nerve
Otic has additional somatic motor root from nerve to medial pterygoid and pas through w/o synapse to supply tensor tympani and tensor palati
3 primary brain vesicles
& embryology age
-7-8 weeks from rostral neural tube
-Prosencephalon (forebrain)
-Mesencephalon (midbrain)
-Rhombencephalon (hindbrain)
5 secondary brain vesicles
Prosencephalon
-Telencephalon (hemispheres)
-Diencephalon (thalamus, hypothalamus, globus pallidus)
Mesencephalon
Rhombencephalon
-Metencephalon (pons, medulla)
-Myelencephalon (cerebellum)
3 Types of white matter tracts and examples
Commissural
-2 hemispheres
-Corpus callosum, hippocampal/forniceal, anterior, habenular, posterior commissure
Association fibres
-Same hemisphere
-External capsule, Extreme capsule
Projection fibres
-Cortex with lower centres
-Internal capsule, CST, CBT
Corpus callosum parts and relations
-Rostrum, genu, body and splenium
-Relations
Superior: Interhemispheric fissure/medial longitudinal fissure, falx cerebri, inferior sagittal sinus
Lateral: Callosal sulcus
Inferior: Septum pellucidum, thalamus, fornix
Corpus callosum blood supply
Arterial: Pericallosal (ACA) and posterior pericallosal (PCA), ACOM
Venous: internal cerebral veins
