BIOS 286 Exam 3

Anterior

Toward the face/front

Posterior

Toward the back

Superior

Toward the head/above

Inferior

Toward the feet/below

Medial

Toward the midline of the body

Lateral

Toward the edge/side

Dorsal

Toward the top of the brain AND back of the spinal cord

Ventral

Bottom of the brain AND front of the spinal cord

Rostral

Front of the brain AND top of the spinal cord

Caudal

Back of the brain AND bottom of the spinal cord

Afferent

PNS to CNS (ascending, sensory, incoming)

Efferent

CNS to PNS (descending, motor, outgoing)

Coronal (Frontal) plane

Vertical cut, medial-to-lateral, divides brain into front and back pieces

Sagittal plane

Vertical cut, rostral-to-caudal, divides brain into left & right

Horizontal plane

Divides brain into top & bottom

Gyri

Raised ridges on the cortical surface

Sulci

Grooved indentations

Fissure

Particularly large/deep sulcus

Longitudinal fissure

Divides the 2 cerebral hemispheres

White matter

Myelinated axons (white due to myelin) — communication pathways

Gray matter

Primarily cell bodies and dendrites; location of most synapses

Location of gray/white matter in Cerebral Cortex

Gray OUTSIDE; White INSIDE (More processing/interpreting info; outer layer — gray matter — allows for decision making & thinking, more processing power; white matter jsut connects different parts of brain)

Location of gray/white matter in Spinal Cord

White OUTSIDE; Gray INSIDE (Spinal cord is mainly about signal transmission & simple reflexes NO complex thinking involved — white matter = long axons going up/down body quickly; gray matter = handles reflexes fast)

Commissures connects…

gray matter of left hemisphere to the right hemisphere

Do commissures cross the midline?

Yes

Association fibers connects…

different gray matter areas within the same hemisphere

Do Association fibers cross the midline?

No

Projection fibers connects…

cortex to lower brain structures OR spinal cord

Do Projection fibers cross the midline?

Descends/ascends

Corpus Callosum

Major commissure connecting 2 hemispheres

White matter tract connecting frontal lobe to parietal lobe within the same hemisphere

Association fibers

Dura Mater

Tough outer layer

Arachnoid Mater

Middle web-like layer

Pia Mater

Delicate layer directly on brain/spinal cord surface

Cerebrospinal fluid (CSF) functions

• Fills ventricles & central canal of spinal cord

• Provides nutrients

• Removes waste

• Cushions CNS

• Maintains stable extracellular environment

Ependymal cells

Line ventricles & secrete CSF by filtering blood

Hydrocephalus

Blockage of CSF drainage causing fluid buildup, increased intracranial pressure & brain damage — can be congenital or acquired (tumors, infections, bleeding, trauma)

BBB Routes

• Tight junctions

• Protein transporters

• Lipid-soluble diffusion

• Receptor-mediated endocytosis/transcytosis

• Efflux pumps

• Nanoparticle delivery

Tight junctions

Restrict water-soluble and polar compounds

Protein transporters

Move glucose, amino acids, nucleosides, choline

Lipid-soluble diffusion

Lipid-soluble agents cross the endothelial membrane

Receptor-mediated endocytosis/transcytosis

For proteins like insulin & transferrin

Absorbative-mediated endocytosis

For catonized proteins; native plasma proteins (albumin) are poorly transported

Efflux pumps

Actively expel/block certain drugs from brain — pushes them back INTO blood

Nanoparticle delivery

Mainly via Receptor-mediated endocytosis/transcytosis AND Absorpative-mediated endocytosis

Stroke

Interruption of blood flow to the brain; cell death

Ischemic stroke

Blood clot blocks a vessel

Ischemic stroke causes

• Atherosclerosis

• Atrial fibrillation

• Clotting

Hemorrhagic stroke

Ruptured blood vessel

Hemorrhagic stroke causes

• Aneurysms

• Tumors

• Hypertension

Frontal lobe functions

***LAST region to fully develop

• Executive function

• Attention

• Critical thinking

• Impulse control

• Motor planning

Frontal lobe notable structure(s)

Primary motor cortex

Parietal lobe functions

• Somatosensory perception (touch, pain)

• Spatial awareness

Parietal lobe notable structure(s)

• Primary somatosensory cortex

• Homunculus

Temporal lobe functions

• Hearing

• Smell

• Taste

• Higher-level emotional processing

• Language

Temporal lobe structure(s)

Limbic system structures

Occipital lobe functions

Visual processing (SMALLEST lobe)

Occipital lobe structure(s)

Primary visual cortex (V1)

Homunculus

Distorted body map on somatosensory/motor cortex — body parts represented proportionally to their sensory innervation density (NOT physical size) — hands, lips, & tongue are disproportionately HUGE

Basal ganglia

Collection of interconnected nuclei deep in forebrain & midbrain w/ strong connections to frontal lobe

Basal ganglia structures

• caudate nucleus

• putamen

• globus pallidus

• substantia nigra

• subthalamic nucleus

Basal ganglia functions

• Gatekeeper of VOLUNTARY movement

• Decision making

• Learning

• Emotional regulation

• Motivation

Non-cortical structures

• cerebellum

• brainstem

• spinal cord

Cerebellum

Inferior to occipital lobes; divded into 2 hemispheres

• regulates, refines, coordinates movement

• involved in cognitive functions & emotions

Brainstem

Between cerebrum & spinal cord; location of most cranial nerve nuclei

• Regulates heart rate, breathing & sleep

Spinal cord

• Receives sensory info, sends motor commands to body

• Can process some info independently (spinal reflexes)

Cranial nerves emerge DIRECTLY from the ___ or the ___ NOT the ___.

brain/brainstem AND spinal cord

3 embryonic germ layers

1. Ectoderm

2. Mesoderm

3. Endoderm

Ectoderm

Gives rise to the nervous system & skin

Mesoderm

Give rise to muscle, bones, & connective tissue

Endoderm

Gives rise to internal organs (gut, lungs, etc)

Neurulation

Process by which neural plate folds to form neural tube

The early embryo has a ____ neural plate (____ origin).

Flat AND ectodermal

Folding begins at approximately the _____ (~embryonic day ___ in humans).

4th somite AND 20

The ____ edges of the neural plate ____, meet at the ____, and fuse

Lateral AND elevate AND midline

Fusion proceeds both _____ (toward the head) and _____ (toward the tail).

Cranially AND Caudally

Cranial neuropore closes ~ day ___.

24

Caudal neuropore closes ~ day ___.

28

Somites

Segmented bocks of mesoderm along neural tube that differentiate into cartilage, vertebrae, & connective tissue

3 separate closure points:

1. hindbrain/cervical boundary (6–7 somite stage)

2. forebrain/midbrain boundary

3. rostral extremity of the forebrain

Spina Bifida

Posterior (caudal) neural tube fails to close

Anencephaly

Anterior (cranial) neural tube fails to close, causing severely decreased brain/skull development

From tube to brain: the key sequence

1. Neurulation

2. Neural epithelial cell proliferation

3. Neural stem cell-mediated neurogenesis

4. Radial & tangential migration of neural precursor cells

5. Neuronal differentiation & maturation (lamination, areal identity)

6. Generation of neurites & synapses

7. Gliogenesis

8. Postnatal refinement: synaptic pruning & oligodendrocyte myelination

Differential proliferation along the _______ axis of the neural tube generates different ____ structures

Anterior-posterior AND CNS

Proliferation dominates ____ in development and is not ______ – the _____ end expands much more than the _____ end, forming the brain vesicles

Early AND Homogenous AND Anterior AND Posterior

Radial migration

Perpendicular to brain surface; guided by radial glial cells; produces most excitatory neurons; builds layered structure of cortex

Tangential migration

Parallel to brain surface; involves GABAergic interneurons originating from ganglionic eminences (LGE & MGE); adds complexity & connectivity

The ________ generates the striatum

lateral ganglionic eminence (LGE)

The ________ generates the globus pallidus

medial ganglionic eminence (MGE)

Name the key zones of human neocortex (deep to superficial)

1. ventricular zone

2. subventricular zone

3. intermediate zone

4. subplate

5. cortical plate

6. marginal zone

Key cell types in human neocortex

• Neuroepithelial cells

• radial glial cells

• outer radial glial cells

• intermediate progenitor cells

• cajal-retzius cells

• astrocyte precursor cells

• pre-oligodendrocyte precursor cells

Gyrification: The convoluted folding of the _____ begins after ______ (before the ____ month the surface is ____).

cerebral cortex AND mid-gestation AND 6th AND smooth

Regional signaling molecules along the _______ determine which part of the tube becomes brain vs. spinal cord.

anterior-posterior axis

The _______ is the evolutionarily oldest structure (~____ million years).

hindbrain (rhombencephalon) AND 570

The _____ is the most recently evolved and responsible for ________.

cerebral cortex AND higher-order thinking

Disruptions in either migration type lead to malformations, neurological disorders, and cognitive deficits (NAME 1 kind of disruption)

Lissencephaly (smooth brain) — neurons fail to reach proper positions

Lissencephaly

Absence of normal gyri and sulci caused by defective neuronal migration (weeks 12–24 of gestation)

LIS1

Protein co-localizes w/microtubules & promotes stabilizations; mutations disrupt migration

DCX

Microtubule-associated proteinexpressed in migrating neuroblasts; mutations also cause lissencephaly