spinal cord, brainstem, forebrain 1/30

spinal cord

located within vertebral canal

7 cervical vertebrae

12 thoracic vertebrae

5 lumbar vertebrae

5 sacral vertebrae

extends from foramen magnum to first lumbar vertebra

what is a spinal cord segment?

a part of the spinal cord with a pair of spinal nerves branching off of it

how many spinal cord segments?

31 total

how many cervical spinal cord segments?

8

how many thoracic spinal cord segments?

12

how many lumbar spinal cord segments?

5

how many sacral spinal cord segments?

5

how many coccygeal spinal cord segments?

1

what attaches to each spinal cord segment?

a pair of spinal nerves

C1-C7 spinal nerves

emerge above their respective vertebra

C8 spinal nerve

emerges between CV7 and TV1

how do you classify the level of spinal cord lesions?

according to spinal cord segment, not vertebral level

as you progress through development, what does the spinal cord do?

ascends in the vertebral canal

how old?

8 weeks gestation

how old?

24 weeks gestation

how old?

newborn

how old?

adult

dural sac

extends from conus medullaris to SV2

composed of caudal equina

filum terminale

CSF

site of lumbar needle tap

lumbar needle tap

drains CSF for analysis below LV1 so as to avoid puncturing the spinal cord—typically at LV3

ventral midline of spinal cord

anterior median fissure (artery removed)

dorsal surface of spinal cord

posterior median sulcus

white matter

3 funiculi—anterior, lateral, and posterior

4 parts of gray matter

dorsal, ventral, lateral horns; intermediate zone

what does white matter contain?

myelinated structures (axons)

what does gray matter contain?

unmyelinated structures (soma, dendrites)

lateral horn

only found in segments T1-L2

origin of preganglionic sympathetic fibers

dorsal and ventral roots form

proper spinal nerves

blue

ascending pathways

red

descending pathways

purple

fibers passing in both directions

dorsal horn

receives sensory impulses

ventral horn

origin of somatic efferent/motor neurons

cervical segments

have the most white matter

relatively large horns for UE innervation

thoracic segments

less gray matter bc trunk doesn’t require much innervation

lumbar and sacral segments

most gray matter bc LEs require more innervation

what does this weigert stain depict?

cervical cord

what does this weigert stain depict?

thoracic cord

what does this weigert stain depict?

lumbar cord

what does this weigert stain depict?

sacral cord

brainstem contents

functional centers for all but one of the 12 pairs of cranial nerves

long tracts (CNS axon bundles) that transmit ascending impulses from all parts of the body to the forebrain and impulses that originate in the forebrain

vital functional centers (cardiac, respiratory)—so, lesions are often fatal

how is brainstem damage manifested?

by functional loss (somatosensory, motor, etc.) and abnormalities in cranial nerve functions due to their origin here

neural tube

one end develops into the brain, the other into the spinal cord

medulla

inferior part of the brainstem

contains superior open part (associated with fourth ventricle) and inferior closed part

pons

intermediate part of the brainstem

midbrain

superior part of the brainstem

what is the cavity between the pons and cerebellum?

fourth ventricle—continuous with cerebral aqueduct

medulla (ventral surface)

midbrain (ventral surface)

medulla ventral surface features

medial to lateral: anterior median fissure (continuous with spinal cord), medullary pyramids, preolivary sulci, olives, postolivary sulci

preolivary sulcus

CN 12 emergence point

postolivary sulcus

CN emergence from superior to inferior: CN 9, 10, 11

pons ventral surface (basilar pons) features

most inferior: pontomedullary sulcus (separates pons from medulla)

down midline: basilar sulcus (with basilar artery)

transverse fibers extending from basilar sulcus

pontomedullary sulcus

CN 6 (medial), CN 7, and CN 8 (lateral) emergence point

midpontine level of basilar pons

CN 5 emergence point—motor root more medial than sensory, sensory root is larger

midbrain ventral surface features

cerebral crus, separated by interpeduncular fossa

cerebral crus

CN 4 (emerges from dorsal surface of brainstem, but wraps around lateral sides and can be seen anteriorly) decussation point on lateral/superior sides of pons

CN 3 on medial sides (from interpeduncular fossa)

medulla dorsal surface features

closed (medial to lateral): posterior median sulcus, gracile tubercles, cuneate tubercles

open (medial to lateral): hypoglossal trigones, vagal trigones (slightly inferior; both with nuclei deep to them), vestibular area

pons dorsal surface features

medial to lateral: posterior median sulcus (continued from spinal cord), facial colliculi, vestibular area (continued from open medulla), cerebellar penducles (superior, middle, and inferior)

midbrain dorsal surface features

medial to lateral: corpora quadremina (inferior and superior colliculi)

cerebellar peduncles

attachment site for cerebellum

consist of white matter

inferior colliculi

superior to CN 4 emergence point (before it wraps around laterally)

closed medulla cross section stain

caudal open medulla cross section stain

rostral open medulla cross section stain

caudal pons cross section stain

middle pons cross section stain

rostral pons cross section stain

caudal midbrain cross section stain

rostral midbrain cross section stain

forebrain

consists of telencephalon and diencephalon

superior to the brainstem

diencephalon

contains functional centers for the integration of all info passing from brainstem and spinal cord to cerebral hemispheres, and centers for motor and visceral activity integration

telencephalon

paired cerebral hemispheres that integrate the highest mental functions (ex. sensory and emotional awareness, learning and memory, intelligence and creativity, and language)

most common vascular lesions

“capsular strokes” or bleeds that occur deep in the brain, in the internal capsule of the forebrain within the white matter

third ventricle

cavity of the diencephalon, continuous with cerebral aqueduct

structures of the telencephalon

corpus callosum, interventricular foramen, septum pellucidum, cerebral cortex

corpus callosum

white matter connecting left and right hemispheres

structures of the diencephalon

thalamus, hypothalamus, subthalamus, epithalamus

thalamus

egg shaped, superior to hypothalamus

hypothalamus

inferior to thalamus

controls a lot of autonomic functions

subthalamus

inferior to thalamus and posterior/inferior to hypothalamus

epithalamus

posterior to thalamus

consists of pineal gland

ventral (inferior) surface of diencephalon

mammillary bodies

stalk of pituitary gland (infidibulum)

optic chiasm

coronal myelin stain of diencephalon

telencephalon lateral surface

cerebral cortex—twists and turns to form a gyri with sulci (fissures) in between

components of the telencephalon

cortex, medulla, deep nuclei

lateral ventricles

lateral fissure

starts anteriorly and ends about 2/3 through the brain (ant-post direction)

separates frontal and temporal lobe and parietal and temporal lobe

central sulcus

begins superiorly, goes inferiorly down middle of the brain and stops when it intersects w/ lateral fissure

separates frontal lobe from parietal lobe

precentral gyrus

anterior to central sulcus

primary motor cortex

postcentral gyrus

posterior to central sulcus

primary somatosensory cortex

occipital lobe

most posterior lobe, no clear boundary between it and the parietal & temporal lobes

paracentral lobule

region of the frontal lobe consisting of gyri and sulci and the medial extension of the central sulcus

parieto-occipital sulcus

separates the parietal lobe from the occipital lobe

inwardly curved sulcus on the posterior medial side of the brain

cortical stroke

a bleed (ischemic response to blockage) that occurs in the cerebral cortex

multiple sclerosis

paraventricular plaques within the medulla of the forebrain along the lateral ventricles

PI: the C7 spinal nerve emerges between which vertebrae?

CV6 and CV7

why do we classify lesions in the spinal cord according to spinal cord segment and not vertebral level?

because the spinal cord is not found at all vertebral levels

PI: which of the following brainstem levels includes the decussation of the trochlear nerve?

F

PI: which of the following brainstem levels includes the facial colliculus?

D

PI: which of the following brainstem levels includes the cerebral crus?

H

PI: which labeled cranial nerve emerges from the interpeduncular fossa, near the cerebral crus?

5