Neurons and Neuroglia: Structure, Function, and Brain Anatomy

Neurons

specialized cells that communicate with other neurons, muscles, or glands utilize electrochemical signaling can be categorized be function, morphology, or neurotransmitter released

Neuroglial cells

nonneuronal cells that provide support functions in the nervous system located within the CNS and PNS

Soma

metabolic and genetic region of a neuron

Dendrites

branches processes extending from the soma, may contain small mushroom-shaped projections

Axon hillock/initial segment

initial portion of axon closest to soma, location of action potential (AP) generation

Axon

typically a single branched process extending from the soma, region of AP conduction and transport of materials from soma

Axon terminal

end region of an axon that transmits info to another cell forming a synapse

Multipolar neurons

contain a single axon and numerous dendrites extending from the soma

Unipolar neurons

contain one axon extending from the soma

Pseudounipolar neurons

contain one axon extending from the soma, consisting of a peripheral branch and a central branch

Bipolar neurons

contain two processes, one axon and one dendrite, extending from the soma

Oligodendrocytes

myelinate axons in the CNS; can myelinate multiple segments on one or more axons

Nodes of Ranvier

gaps in myelination

Astrocytes

contain expanded tips at end of processes 'endfeet'; components of the blood-brain barrier

Microglia

macrophage-like cells able to detect and phagocytose invaders (e.g. bacteria)

Ependymal cells

line brain ventricles by forming a continuous epithelial sheet; assist with cerebrospinal fluid (CSF) production and circulation

Satellite cells

surround neuronal cell bodies within sensory and autonomic ganglia

Gray matter

cell bodies of neurons and neuroglia

Nucleus/nuclei

a cluster of neuron cell bodies

Lamina/laminae

'layer' or 'band' of neuron cell bodies (lamina of Rexed)

Cortex

neuron cell bodies found on the outer surface of the brain & cerebellum

Ganglion/ganglia

group of cell bodies in PNS

White matter

neuronal processes: fibers/axons

Tract

group of axons

Fasciculus/fasciculi

'bundle' of axons

Lemniscus/lemnisci

'band' of axons

Funiculus/funiculi

'column' of axons; often large, found in spinal cord; includes several fasciculi or tracts

Nerve

group of axons in the PNS

Endoneurium

surrounds individual axons

Perineurium

encloses each small bundle of axons

Epineurium

wraps around entire nerve

Diencephalon

"through" or "between" "brain"

Telencephalon

"end" "brain" = cerebral hemispheres

Thalamus

relay center for most sensory info to the cerebral cortex; involved in motor control

Hypothalamus

main autonomic center of the brain; aids in the control of the pituitary gland

Epithalamus

situated dorsomedially to thalamus; includes the pineal gland

Association fibers

connect different cortical areas within same hemisphere

Commissural fibers

connect a cortical region from one hemisphere to a cortical region in the opposite hemisphere

Projection fibers

Connect a cortical region to a subcortical region or vice versa

Corticopetal fibers

Afferents to cerebral cortex

Corticofugal fibers

Efferents from the cortex

Internal capsule

Paired structures (R + L) that include major sensory and motor pathways

Gyri

Highly convoluted folds of the cerebral hemispheres

Sulci

Grooves between adjacent gyri

Fissures

Deeper grooves in the cerebral hemispheres

Brainstem

Connects the spinal cord to the cerebrum and cerebellum

Medullary pyramids

Paired structures on the ventral surface of the medulla comprised of descending fibers (corticospinal axons)

Medullary olives

Paired structures on the ventrolateral surface of the medulla comprised of many neurons

Inferior cerebellar peduncles (ICPs)

Paired stalks of axons going to and from the cerebellum that help attach the cerebellum to the medulla

Middle cerebellar peduncles (MCPs)

Paired stalks of axons going to the cerebellum that help attach the cerebellum to the pons

Tectum

Dorsal region of the midbrain containing two paired nuclei: superior colliculi and inferior colliculi

Superior cerebellar peduncles (SCPs)

Paired white matter structures that connect the cerebellum to the midbrain and cerebrum

Choroid plexus

Structure that produces and secretes cerebrospinal fluid (CSF)

Arachnoid villi (arachnoid granulations)

Structures responsible for the resorption of cerebrospinal fluid

Interventricular foramina

Paired structures that connect the anterior horn of each lateral ventricle to the III ventricle

Cerebral aqueduct

Single canal that connects the III ventricle to the IV ventricle, located in the midbrain

Rhomboid fossa

The floor of the IV ventricle

Lateral apertures (foramina of Luschka)

Paired apertures that connect the IV ventricle with the subarachnoid space

Median aperture (foramen of Magendie)

Single aperture between the cerebellum and medulla that connects the IV ventricle with the subarachnoid space

Cisterna magna (cerebellomedullary cistern)

Reservoir between the cerebellum and medulla

Obstructive (non-communicating) hydrocephalus

Blockage of CSF circulation within the ventricles

Communicating hydrocephalus

Excess CSF throughout the entire ventricular system often due to dysfunctional resorption

Papilledema

Optic disc swelling that indicates increased intracranial pressure

caudate nucleus

neurons involved in motor control

amygdala

nuclear complex

hippocampus

gray matter structure not found on cerebrum surface; functions: processing of memory and emotions

fornix

white matter structure; fiber tract connecting the hippocampus to the diencephalon

corpus striatum

series of motor nuclei located deep within each hemisphere (telencephalon)

septum pellucidum

thin, curtain-like structure; separates the anterior horns of the R + L lateral ventricles

interthalamic adhesion

a bridge of gray matter connecting the R + L halves of the thalamus

cervical enlargement

cord segments C4-T1; accommodates innervation of the upper extremities

lumbosacral enlargement

cord segments L2-S3; accommodates innervation of the lower extremities

conus medullaris

at vertebral level L1-L2; tapers into filum terminale

V-M (ventral median) fissure

unpaired, continuous

D-M (dorsal median) sulcus

unpaired, continuous

D-I (dorsal intermediate) sulci

paired R +L; present at T6 and above; not continuous

posterior (dorsal) funiculi

paired: R + L; continuous; located between dorsal median sulcus and dorsal lateral sulcus; contain mostly ascending fibers

dorsal lateral tract (Lissauer's tract)

continuous; found at the dorsal lateral sulcus zone; comprised of short collateral fibers (ascending & descending)

fasciculus gracilis

continuous; major ascending pathway

fasciculus cuneatus

major ascending pathway; not continuous along cord; present only at T6 and above

spinothalamic tract

anterolateral system; continuous; major ascending pathway

anterior white commissure

large bundle of fibers that cross midline (decussate) to contribute to the spinothalamic tract

lamina II (substantia gelatinosa)

receives incoming fibers from dorsal root and descending p/ways; contains important interneurons that can modify nociceptive data

intermediolateral nucleus (IML)

in lateral horn of spinal cord segments T1-L2/3; preganglionic sympathetic neurons

nucleus dorsalis (Clarke's nucleus)

located in cord segments C8-L3; neurons of the dorsal spinocerebellar tract

sacral autonomic nucleus

located in cord segments S2-S4; preganglionic parasympathetic neurons

phrenic nucleus

innervates diaphragm; found in cord segments C3, 4, 5

(spinal) accessory nucleus

axons form the spinal root of CN XI; innervate SCM and trapezius muscles; found in cord segments C1-5

neural crest cells

PNS neurons and neuroglia (cranial, spinal, and autonomic nerves)

globus pallidus

medial part of the lenticular nucleus

putamen

lateral part of the lenticular nucleus

Mesencephalon (midbrain)

forms midbrain & cerebral aqueduct

Metencephalon

forms cerebellum, pons, choroid plexuses, & (rostral portion) IV ventricle

Myelencephalon

forms medulla & (caudal portion) IV ventricle

Neural tube cells

brain & spinal cord

Sulcus limitans

divide the mantel zone into alar plate & basal plate

Alar plate

dorsal horn cells

Basal plate

ventral horn cells

Marginal zone

white matter of spinal cord

Cauda equina

lumbar and sacral nerve roots continue caudally