Outline of NeuroAnatomy - HIGH YIELD

NeuroAnatomy 
1.      General Organization

   a.       31 pairs of spinal nerves & 12  CN

           i.      C1-C7 exit on top on vertebrae, rest is below

1.      C8 goes over T1 vertebrae

2.      Blood supply, Meninges & spinal fluid

    a.   2 main arteries:

                                                                                               
 Internal carotid -  supplies front area

1.      obstruction causes CONTRALATERAL    weakness & loss of sensation

2.      divisions:

a.       ACA- midline area -- LEGS

b.      MCA- lateral level of cerebrum -- ARM

c.       PCA- lower level of cerebrum -- HEAD

          ii.      Vertebral artery – changes its name to basilar at the pons & then divides to PCA

1.      Obstruction affects visual area of cerebrum, brain stem & cerebellum

b.      Circle of willis:

                  CN III- exits btwn the posterior cerebral a. & sup. cerebellar Aneurysm of either causes CN III palsy – down & out eye

     ii.      Located within the PIA

c.       PAD 

    i.      From brain à skull = Pia, Arachnoid, Dura

d.      Sinuses:

           i.      Superior sagittal sinus- spinal fluid drainage

            ii.      Cavernous sinus- venous blood drains from the eye, entry source into brain of orbital & facial infections

1.      Carotid a. & all nerves entering orbit go through sinus

             iii.      Transverse sinus- runs by ear, can be involved in inner ear infections

e.       CSF:

         i.      Secreted by chroid plexus

         ii.      Flows from the 2 lateral ventriclesà2 interventricular foramina à 3^rd ventà aqueduct of sylviusà 4^th ventricleà outside brain via Middle foramena of Magendie, or Lateral foramena of Luschkaà subarachnoid space

          iii.      Obstruction anywhere will head to dilation of lateral vents = hydrocephalus

           iv.      Hemorrages:

1.      Subarachnoid- rupture of aneurysm

2.      Subdural- tearing of bridging veins

3.      Epidural – blood collects btwn dura & bone, tears middle meningeal a.

3.      Spinal cord

   a.       Central= gray matter (neuronal cell bodies & synapses), peripheral= white matter (ascending & descending pathways)

   b.      SPINOTHALAMIC: enters spinal cord, crosses over to opposite half of cord, ascends to thalamis on OPPOSITE side, then moves on to cerebral cortex

              i.      LESION= loss of pain & temp. CONTRALATERAL, BELOW level of lesion

   c.       DORSAL COLUMN: initially on same side of spinal cord, crosses over @ junc btwn spinal cord & brain stem

                  i.      Synapses before cross over- n.cuneatus (upper level), n. gracilis (lower level)

                  ii.      LESION= decrease in conscious proprioception & sterognosis (vibration) IPSILATERAL, BELOW level of lesion

   d.      SPINOCEREBELLAR: remains ipsilateral. Enters cerebellum via sup. & inf. peduncles

   e.       **CEREBELLAR LESIONS TEND TO PRODUCE IPSILATERAL DEFECTS. CEREBRAL CONTRALATERAL DEFECTS**

   f.        CORTICOSPINAL TRACT (MOTOR): extends from motor area of cerebral cortex down to brain stem, crossing over at medial lemniscus

                   i.      Synapse in the anterior horn – above synapse= UMN, below = LMN

                   ii.      UMN- spastic paralysis, no muscle atropy, no fasiculations & fibrillation, hyperreflexia, Babinski reflex present

                   iii.      LMN- opposite

       

4.      Brain stem

   a.       Location: diencephalon- 1,2;  midbrain- 3,4;  pons- 5,6,7,8;  medulla- 9,10,11,12

   b.      CN parasym: 3,7,9, 10

   c.       Rostral Midbrain:                                                           

   d.      Pons:

   e.       Rostral medulla: 

   f.        nucleus Solitarius- located in medulla (somatic Sensory- lateral)

                    i.      include taste (7,9 & 10), sensory from carotid (9), sensory return along vagus (10)

   g.       Nucleus aMbiguous- located in medulla (somatic Motor- medial)

                    i.      Involved in swallowing (9&10) & speech (10)

   h.      CCR: vertigo, with difficulty in taste, swallowing or speech.

                    i.      Brain stem lesion. Nucleus solitaries & ambiguous lie near vestibular nuclei

   i.         CCR: lesion ABOVE level of nucleus of CN 7 (pons)- area of face BELOW eye paralyzed

   j.         CCR: lesion severed nucleus of CN 7- bell’s palsy

                     i.      “crocodile tears”= cry when eating instead of salivating. Regenerating fibers are effd up

5.      Visual system:

a.       CCR: pt with severe blow to back of head = bilateral central scotomas

    i. center of the retina projects to occipital lobe

b.      Optic reflexes:

     i.      Pupillary light reflex = shine light in 1 eye both pupils constrict (consensual reflex)

c.       Accommodation

      i.      Stimulate the smooth muscle of the ciliary body in the eye to contract, enabling the lens to change its shape

      ii.      CN 3: constricts pupil to focus

       iii.      CCR: syphilitic pupil (Argyll-robertson)- constricts during accommodation, but not to light

1.      Lesion lies in pretectal area of superior colliculus

d.      Conjugate gaze:

           i.      Damage to the motor areas of the cerebral cortex produce contralateral paralysis of extremities & ABILITY OF EYE TO LOOK TOWARD 


CONTRALATERAL ENVIORN

1.      Broadmans area 8

            ii.      MEDIAL LONGITUDINAL FASCICULUS – seen in MS. Eye can’t look medially

            iii.      CCR:  Lesion close to SUP. COLLICULAR LEVEL (convergence & vert gaze circuit in MB next to sup. colliculus)

1.      parinaud’s syndrome: pupillary constriction & paralysis of vert gaze

2.      pineal gland tumor 

6.      ANS & Hypothalamus:

a

7.      Cerebellum, basal ganglia, & thalamus

a.       Cerebellar dysfunction – awkwardness of intentional movements

             i.      Sways with or without eyes closed

b.      Basal ganglia disorder- meaningless unintentional movement occurring unexpectedly

8.      Cerebral cortex

a.       CN10- kuh kuh kuh  (soft palate), CN12- la la la (tongue), CN 7- mi mi mi (lips)

b.      Cerebral cortical   regions: 

 i. Area 4 (primary motor area): lesion = flaccid paralysis, spasticity & deep tendon reflex increases if area 6 is involved

ii. Area 8 (frontal eye field): lesion= probs moving eye to opp side

iii. Area of frontal cortex: complex behavioral activities. Lesion changes judgment

iv.      Lesion to dominant cortex = aphasia, lesion to non-dominant cortex= visual & auditory

 v.      Area 44,45 (brocas): Lesion to dominant cortex = aphasia, lesion to non-dominant cortex= visual & auditory

vi.      Area 3,1,2 (primary somesthetic area): lesion CONTRA impairment of touch, pressure & proprioception.

vii.      Area 41, 42 (auditory)

 viii.      Area 22 (wernickes)

ix.      Area 39 (angular): lesion in DOMINANT hemisphere = alexia & agrapha (cant read & write)

 x.      Area 17,18, 19: total destruction causes blindness in CONTRA visual field,

1.      Damage to 18,19 alone = difficulty recognizing & ID’ing objects