Ventricles Spinal Cord Cranial Nerves Objectives Identify cranial
Ventricles, Spinal Cord & Cranial Nerves
Objectives • Identify cranial nerves and describe the function of each • Understand the signs and tests for CN dysfunction • Make an accurate model of the ventricle system of the brain • Discuss the clinical implications of dysfunction in the ventricular system • Describe the basic organization of the spinal cord
Cranial Nerves and Brain Stem Please refer to Cranial Nerve Handout
A few things first • 12 pairs • All ipsilateral symptoms and signs except IV Trochlear (which is also the only CN that exits brainstem on the dorsal surface) • The optic and olfactory nerves are CNS, the rest have axons and receptors that are considered PNS • Can carry motor, sensory or mixed information ipsilateral = same side
testing each cranial nerve more or less separately is helpful in diagnostics but not a good way to test function! Reality is more complex than that!
1 Olfactory (S) Receptors>nerve> olfactory bulb> olfactory tract (axon): • • • Amygdala (fear) Orbitofrontal cortex (food!) Thalamus (declarative memory) Hypothalamus (visceral) Hippocampus (memory)
Olfactory Test • Baby powder • Chocolate • Cinnamon • Coffee • Mothballs • Peanut Butter • Soap
2 Optic Nerve (S)
Rods and Cones> optic nerve> optic chiasm> optic tract> thalamus > superior colliculi > thalamus> occipital lobe
Optic Pathway Rods and Cones> optic nerve> optic chiasm> optic tract> thalamus > superior colliculi > thalamus> occipital lobe Test: • acuity • pupillary light reflex • visual field Superior colliculi
3 Oculomotor (M) All movements of eye, except: • Down and medial (trochlear) • Lateral (abducens) Directions of each CN and muscles
Oculomotor Reflexes • Pupillary Reflex • Consensual • Accommodation
Oculomotor Test with abducens and trochlear: basically move stimulus in shape of an H Signs of Lesion: 1. Lateral Strabismus (complains of double vision) 2. Ptosis (droopy eyelid) 3. Nystagmus (in absence of stimulus)
4 Trochlear Nerve (M) • Starts in and around oculomotor nucleus, crosses at midbrain, exits out the contralateral side of the dorsal brain stem and then back into the orbit (eewwwhhh!) Test for Lesion: can’t look down and in (trouble descending stairs)
5 Trigeminal Nerve (Mx) Sensory: face, mouth, cornea Motor: chewing muscles Reflexes: Masseter Corneal 3 Branches: 1. Ophthalmic 2. Maxillary 3. Mandibular
Test Trigeminal 1. Sensation of face 2. Clamp down jaw, try to open 3. Palpate masseter and temporal mm
6 Abducens (M) Abducts the eye (moves it laterally) Think about it- adduct would be medial
7 Facial (Mx) Sensory: taste tip of tongue Motor: facial expression, lacrimal & salivary glands Supplies the motor response to the corneal reflex (when the eye is touched) Test- facial expression and taste on tip of tongue
8 Vestibulocochlear (S) Tests: • Audition- tuning fork • Turn head and see if eyes move slowly in opposite direction • Test for balance by gently pushing them
9 Glossopharyngeal Nerve (Mx) • Sensory: soft palate and pharynx, taste/sensation from posterior tongue, carotid sinus (blood pressure sense) • Motor: parotid gland (salivary gland) and 1 pharyngeal mm • Sensory portion of the gag and swallowing reflexes so that’s how it is tested
10 Vagus (Mx) • Sensory: larynx & pharynx • Motor: autonomic functions of gut, cardiac (inhibition), vocal cords, swallowing • Motor component of the gag and swallow reflexes • Test: reflexes, hoarseness, uvula (thing in the back of your throat)
11 Spinal accessory nerve • Innervates shoulder and neck mm • Test sternocleidomastoid and trapezius
12 Hypoglossal Nerve • Movement of the tongue • Test: stick tongue out, it will point to the side of the lesion, make sure they can push equally on both checks with tongue
Basic Organization of the Spinal Cord
8 12 5 5 1 Cervical Thoracic Lumbar Sacral Coccygeal
S 1
Root Muscle(s) Action C 5 Deltoid Shoulder Abduction C 5 Infraspinatus Humeral external rotation C 5, 6 Biceps Flexion of supinated forearm C 6 Extensor carpi radialis, ulnaris Wrist extension C 7 Extensor digitorum, triceps Finger extension, forearm extension at elbow C 8, T 1 Interossei, lumbricals Finger ab and ad (spread and close against force) L 2 -L 4 Quadriceps, iliopsoas, adductors Knee extension, thigh on hip flexion, thigh adduction L 5 Anterior tibial, extensor halluces Ankle and big toe dorsiflexion (walk on heels) S 1 Gastrocnemius Ankle plantar flexion (walk on tip toes)
Same magnification, cross sections White matter is dark, grey is light Dorsal on top, ventral on bottom (imagine a person laying on stomach) Dorsal column Dorsal horn Lateral column Lateral horn Ventral column
Dorsal=sensory Ventral=motor
Ventricles
- Slides: 35