NSCI 2001 Exam 1 Part 1 (2-4)

Glia

• Have no axons

• Myelin formation (Oligodendrocytes and Schwann Cells)

Tracts

Bundles of axons (CNS)

Ganglia

Groups of neuronal somata

Nerves

Bundles of axons (PNS)

Dorsal

• “Back”

• “Top” of the brain, “back or behind” of the spinal cord

Ventral

• “Belly”

• “Bottom” of the brain, “stomach or front” of the spinal cord

Always Superior

Up

Always Inferior

Down

Always Anterior

Front

Always Posterior

Behind

Rostral

• “Towards the beak”

• Follows the CNS, towards the brain (head)

Caudal

• “Towards the tail”

• Follows the CNS, towards the bottom of the spinal cord (feet)

Orientation of the Human Brain

• “X” Space - Rostral/Anterior, Caudal/Posterior

• “Y” Space - Dorsal/Superior, Ventral/Inferior

Coronal sectioning

Cross sectional

Horizontal sectioning

• Axial

• Most clinical scans are done this cut

Parasagittal

Sideview

Diencephlon (Midbrain area)

“Quiets” sensory neurons

Medial Longitudinal

• Runs Rostral/Caudral

• Separates left and right hemispheres

Gyrus and Sulcus

• G - Bump or ridge

• S - Groove (deep fissures)

What creates the embryo

Inner cell mass filled with fluid

Embryonic age

• Time after fertilization

• Biologists (Use this age in class)

Gestational age

• Time after last menstral period (E.A. + ~2 weeks)

• Clinicians

Primitive streak

• Cells migrate to here

• Splits right and left half

• Allows generation of mesoderm

Ectoderm

• Top layer (Dorsal)

• Skin and nervous system

Endoderm

• Bottom layer (Ventral)

• Gut, glandular organs, and liver

Mesoderm

• Middle space

• Bone, muscle, and some organs

• Induces ectoderm to become neural plate (CNS and PNS creation)

Dividing cells move…

Rostrally to extend the embryonic disk

Neurulation

• Neural plate → Neural groove → Neural tube/Neural Crest

• Plate bulges out and up to develop the CNS

Neural Crest

• Becomes the PNS (of the body)

• Is made from the tissue when the tube is formed

• Develops spinal column

Closure of neural tube…

• Starts in the center

• Moves both rostrally and caudally

• Creates the CNS

Alar plate

• “Top wings”

• Sensory

• Sensory axons in

Basal plate

• “Bottom wings”

• Motor

• Motor axons out

Sulcus limitans

• Separates alar and basal plates

• Visible in the brain stem

• Becomes dorsal and ventral horn

Spina Bifida

• Caudal

• Incomplete closure of the spinal tube or spine

• Most often of no consequence

Anecephaly

• Rostral

• Incomplete closure of the brain end of the spinal cord

• Rare and lethal

Cell cycle

• G1, S, G2, M

• When a cell differentiates into a neuron, mitosis ends and the cell enters G0 (terminal differential)

G1 Phase (gap)

Pause: factors that initiate or block cell division are expressed

S Phase

• DNA synthesis

• DNA is replicated

G2 Phase (gap)

Pause: proteins needed for mitosis are expressed

M Phase

• Mitosis

• Cell divides into two

PNS derives from…

• Neural crest

• Neural placodes

Neural Placodes

• Develops and becomes the PNS (of the head)

• Lens Placode

• Lens

Lens placode

• Eye

• Retina

• Brain tissue

Olfactory placode

• Sense of smell

• From both placode and crest

Placodes can also…

Induce changes in neighboring cells and tissues

Three primary vesicles

• Prosencephalon (Blue, Rostral)

• Mesencephalon (Orange)

• Rhombencephalon (Green, Caudal)

Secondary neural vesicles

• Myelencephalon

• Metencephalon

• Mesencephalon

• Diencephalon

• Telencephalon

Pontine flexure

• Marks the boundary between the Myelencephalon and the Metencephalon

• Opens the 4th Ventricle

• Becomes the brain stem

Prosencephalon becomes..

• The Forebrain (Rostral)

• Telencephalon

• Diencephalon

• Optic Vesicles

Telencephalon becomes…

• The most of the brain

• “C” shaped

• Cerebral cortex

• Basal ganglia

Diencephalon becomes…

• Thalamus

• Hypothalamus

Optic Vesicles becomes…

• Retina

Mesencephalon becomes…

• Midbrain

Rhombencephalon becomes…

• The Hindbrain (Caudal)

• Metencephalon

• Myelencephalon

Metencephalon becomes…

• Cerebellum

• Pons

Myelencephalon becomes…

• Medulla

The main meninges

• Dura mater

• Arachnoid mater

• Pia mater

Falx cerebri

• Stabilizes and prevents the brain from force and cerebral hemispheres from moving laterally (side to side)

Dural folds

• Stabilizes the posterior part of the brain

• Tentorium cerebelli is above the cerebellum

Lateral ventricles

• One in each hemisphere

• Within telencephalon

Third ventricle

• Ventral to the Lateral ventricles

• Lies on the midbrain

• Separates thalamus and hypothalamus

Cerebral aqueduct

• Connects the third and fourth ventricles together

• (Diencephalon to pons)

Fourth ventricle

• Rostral to the cerebellum

Cerebrospinal fluid (CSF)

• Extracellular fluid (plasma like)

• High Na, Low P, and little protein

• Made by the choroid plexus

• 500 ml produced each day

Choroid plexus

• Found in all ventricles

Total volume of ventricles

200 ml

Excess CSF drains through

Subarachnoid space to veins (arachnoid granulations/ Fourth ventricle)

Hydrocephalus (in newborns)

• CSF doesn’t drain

• Not fatal if treated correctly (Shunting to the abdomen)

• Doesn’t become severe

Hydrocephalus (in adults)

• Critical condition

• Pressure onto the brain stem can cause death

• Shunting for treatment

Menigitis

• Cloud or foggy CSF

• Changes in proteins or glucose

Lumbar Puncture

• To sample CSF

• Diagnose CSF diseases like meningitis