Neuroanatomy 1

Gyrus

ridge on surface of cerebrum (and cerebellum)

Sulcus

groove

Fissure

deep groove; intended to denote a separation between major landmarks

Gray matter

generic term for neurons in the CNS

Nucleus

clearly defined mass of neuron cell bodies in the CNS ex. nucleus accumbens

Ganglion

collection of neuron cell bodies in the PNS ex. dorsal root ganglion

Substantia

less distinct borders of cell bodies than nuclei ex. substantia nigra

Locus

small but well-defined mass of neuron cell bodies (smaller than a nucleus) ex. locus coeruleus

White matter

generic terms for a collection of (myelinated) axons

Tract (projection)

set of axons in CNS, also known as fibers, that project from one structure and form synapses on a second common structure

Fasciculus

a smaller part of a tract, could be in CNS or PNS

Nerve

bundle of axons either projecting from the CNS to something in the periphery (muscle or gland), or from a sense organ to the CNS

Bundle

collection of axons that run together but do not necessarily share the same origin or destination

Chiasm

an X-shaped crossing of nerve fibers between the cerebral hemispheres

Commissure

group of nerve fibers crossing the sagittal plane without forming a cross-shape

Contralateral

result of crossing, at the more-or-less corresponding position on the laterally opposite side of the sagittal plane

Decussation

where nerve fibers obliquely cross from one lateral part of the brain to the other (cross at a level other than their origin)

How has neuroanatomy been studied?

static images (MRI), cadaver tissue, fluorescence, diffusion tensor imaging

Neural induction

a number of molecules interact to determine whether the ectoderm becomes neural tissue or develops in another way to become skin

Which layer provides signals to ectoderm?

mesoderm

Telencephalon

amygdala, hippocampus, cerebrum, basal ganglia, lateral ventricles

Diencephalon

epithalamus, thalamus, hypothalamus, subthalamus, pituitary, pineal, third ventricle

Mesencephalon

colliculi, cerebral peduncle, pretectum, cerebral aqueduct

Metencephalon

pons, cerebellum

Myelencephalon

medulla oblongata

Neural induction

commitment of ectodermal tissue to neural tissue

Neurulation

process of neural tube formation; forms inwards

Neuromeres

distinctions that start to form; budding of neural areas occurs in the rostral part of the neural tubes, which will eventually become the brain in regions called neuromeres; formation occurs by 4 weeks

Prosencephalon

forebrain

Mesencephalon

Midbrain

Rhombencephalon

hindbrain

Prosencephalon 5th week

telencephalon and diencephalon

Mesencephalon 5th week

mesencephalon

Rhombencephalon

metencephalon and myelencephalon

1. Mitosis/proliferation

creation of new cells

2. Migration

cells move to new locations

3. Differentiation

specialized of the cell type

4. Aggregation

cluster together with like cell types

5. Synaptogenesis

create new synapses

6. Neuron death

“pruning” of unsuccessful nerve cells

7. Synapse rearrangement

modifying synapses

8. Myelination

formation of myelin sheath around axons

Order of proliferation layers

ventricular → intermediate → cortical

Cortical plate

formed from migrating cortical cells; precursor of layers II-VI of cerebral cortex

Vertical cleavage

increases number of precursor cells and stay within ventricular zone

Horizontal cleavage

results in migration of superficial cell and another cell that stays within ventricular zone

Subplate

formed from first migrating cells

What layers develop first in the cortex?

deeper layers develop first, and then the more superficial layers develop by cellular migration through the deeper layers

What differentiates first?

neurons followed by astrocytes and oligodendrocytes

Growth cone

as the nerve cell develops, its spouts a hand-like distal end

Axonal pathfinding

axons locate their target tissues by using chemical attractants and repellants located around or on the surface of guide cells

Ventricles

set of structures that hold CSF in the brain; helps to bathe and cushion the CNS within the bone; 4 total

Sutures

joining of the skull bones; metopic, coronal, and sagittal

Anterior fontanelle

intersection of coronal and sagittal suture

Neural Tube Defects (NTD)

affect brain (anencephaly, encephalocele) or spinal cord (spinal bidifa)

Anencephaly

the brain initially protrudes through a defect in the cranial vault and is gradually destroyed; eventually all that’s left is a small, vascular mass of disorganized neural tissue mixed with choroid plexus

Spina bifida

affects the brain, spinal cord, and muscles surrounding it; may result in loss of movement and or sensation to the legs and feet as well as bowel movement and bladder dysfunction; arise from abnormalities occurring during three major concurrent migrations of cell groups during embryogenesis: neural tubes, notochord, and mesenchymal tissue

Pattern of brain maturation

posterior to anterior with visual areas maturing first followed by sensory and motor areas and concluding with frontal areas

Neurocranium

consists of bones that surround and encase the brain and sensory organs connected to the brain; also known as the braincase

Viscerocranium

collection of bones that defines the facial skeleton and supports the soft tissue of the face

Brainstem

lower part of the brain; continuous with spinal cord; provides main motor and sensory innervation to the face and neck via cranial nerves; bilaterally symmetrical

Components of brainstem

midbrain, pons, and medulla oblongata

What do the 12 cranial nerves innervate?

head, neck, throat, and abdomen

How do olfactory and optic nerves enter the brain?

via the inferior surface of the cerebrum

How do the last 10 cranial nerves enter/leave the brain?

via the brainstem

Afferent fibers

carry nerve impulses from receptors or sense organs towards the CNS

Efferent fibers

carry nerve impulses away from the CNS to effectors

Olfactory Nerve

I- sensory; smell

Optic Nerve

II- sensory; vision

Oculomotor Nerve

III- motor; eye movement

Trochlear Nerve

IV- motor; eye movement

Trigeminal Nerve

V- sensory and motor; somatosensory: face, mouth, cornea

Abducens Nerve

VI- motor; eye movement

Facial Nerve

VII- sensory and motor; motor control of facial expressions, taste from anterior tongue, lacrimal and salivary glands

Vestibulo-cochlear Nerve

VIII- sensory; hearing and balance

Glossopharyngeal Nerve

IX- sensory and motor; somatosensory: upper pharynx and taste from anterior tongue

Vagus Nerve

X- sensory and motor; autonomic gut function, somatosensory lower pharynx, motor control of vocal chords, swallowing

Spinal Accessory Nerve

XI- motor; motor control of shoulder and neck

Hypoglossal Nerve

XII- motor; motor control of tongue

Purely sensory cranial nerves

olfactory (I), optic (II), vestibulo-cochlear (VIII)

Purely motor cranial nerves

oculomotor (III), trochlear (IV), abducens (VI), spinal accessory (XI), hypoglossal (XII)

Mixed afferent and efferent cranial nerves

trigeminal (V), facial (VII), glossopharyngeal (IX), vagus (X)

Ascending tracts in brainstem

anterolateral system (spinothalamic); posterior column-medial lemniscus system; spinocerebellar tracts

Descending tract in brainstem

corticospinal tracts

Cerebellar connections in brainstem

pontine nuclei

Mesencephalic nucelus

CN V- sensory

Pontine (chief) sensory nucleus

CN V- sensory

Vestibular nucleus

CN VIII- sensory

Cochlear nucleus

CN VIII- sensory

Solitary nucleus

CN VII, IX, & X- sensory

Spinal (descending) nucleus

CN V- sensory

Edinger-Westphal nucleus

CN III- motor, parasympathetic

Oculomotor nucleus

CN III- motor, voluntary

Trochlear nucleus

CN IV- motor, voluntary

Trigeminal motor nucleus

CN V- motor, voluntary

Abducens nucleus

CN VI- motor, voluntary

Facial nucleus

CN VII- motor, voluntary

Superior salivatory nucleus

CN VII- motor, parasympathetic

Inferior salivatory nucleus

CN IX- motor, parasympathetic