Nervous system-COT

central nervous system (CNS)

Brain and spinal cord; derived from neurectoderm (neural tube)

peripheral nervous system (PNS)

Everything outside the CNS (nerves, ganglia, neural tissue); derived from neural crest

neurectoderm

Embryonic source of the CNS (neural tube)

neural crest

Embryonic source of the PNS and all PNS glia

somatic division

Part of PNS with afferent sensory fibers from peripheral receptors and efferent motor fibers to skeletal muscle (voluntary)

autonomic division

Involuntary visceral motor part of the PNS; includes sympathetic and parasympathetic systems

afferent fibers

Sensory fibers carrying information from receptors (touch, temperature, pain) toward the CNS

efferent fibers

Motor fibers carrying information from the CNS to the periphery to innervate skeletal muscle

enteric nervous system

Third subdivision of the PNS (per most); innervates the gut; sensory and motor; important for GI motility

myenteric (Auerbach's) plexus

Enteric plexus formed by enteric ganglia and neurites (with the submucosal plexus)

submucosal (Meissner's) plexus

Enteric plexus formed by enteric ganglia and neurites (with the myenteric plexus)

CNS/PNS border in the spinal cord

Entry and exit points of the nerve roots; dorsal root ganglia and ventral roots are PNS

CNS/PNS border in the brain

Olfactory (I) and optic (II) nerves are CNS; the rest of the cranial nerves are PNS

neuronal cell body (soma)

Supports the neuron's metabolic and synthetic needs; integrates electrical signals (final integration at the axon hillock)

dendrites

Input end of a neuron; receive information via synapses and carry the signal toward the soma; typically several

axon

Output end of a neuron; usually one; conducts action potentials away from the soma

neurites

General term for neuronal processes (dendrites and axons)

neuropil

Neuronal processes considered as a distinct type of tissue

axon hillock

Area where the action potential (spike) is typically generated; mostly lacks Nissl bodies

action potential (spike)

Electrical signal generated at the axon hillock and conducted down the axon

bipolar neuron

One dendrite arrives at the soma and one axon leaves; simplest neuron; sensory (e.g., photoreceptors, olfactory receptors); the second neuron in a sensory chain

unipolar neuron (pseudounipolar neuron)

Evolutionary modification of bipolar neuron; soma sits off the conducting chain on a short stalk; peripheral sensory neurons (touch, vibration, temperature, pain)

peripheral process

Receiving end of a unipolar neuron (used instead of "dendrite")

central process

Transmitting end of a unipolar neuron (used instead of "axon")

multipolar neuron

Most typical neuron; more than one dendritic tree on the soma, one axon that may branch; e.g., primary spinal cord motor neurons, somatic and visceral motor neurons

arborization

Branching of a dendritic tree or axon

Which neuron shape are radial glia?

Bipolar (though they are not neurons)

Which neuron type is found in the dorsal root ganglion?

Pseudounipolar sensory neurons (central nucleus, ring of satellite cells, no synapses on the soma)

Which neuron type is found in the ventral horn and autonomic ganglia?

Multipolar motor neurons (eccentric nucleus, dispersed satellite cells, abundant synapses)

Nissl bodies

Light microscopy appearance of large amounts of basophilic rough ER and polyribosomes; indicate heavy protein synthesis; mainly absent from the axon hillock

axodendritic synapses

Synapses from a neighboring cell's axon onto a dendrite

presynaptic element

Region specialized for vesicular release of neurotransmitter

postsynaptic element

Contains membrane receptors that convert the chemical signal into a membrane potential

membrane potential

Electrical change produced in the postsynaptic cell when neurotransmitter binds its receptors

axosomatic synapse

Synapse onto the soma

axoaxonal synapse

Synapse onto an axon

terminal bouton

Presynaptic element at the end of an axon

bouton en passant

Presynaptic element along the length of an axon

dendritic spine

Normal location of the postsynaptic element

excitatory and inhibitory synapses

Can be distinguished by their EM morphology

myelinated axon

Axon wrapped in a myelin sheath; spikes propagate by saltatory conduction

saltatory conduction

Spikes jump between nodes of Ranvier along a myelinated axon

nodes of Ranvier

Gaps in the myelin where spikes are regenerated

unmyelinated axons

Lack a myelin sheath; spikes travel more slowly

myelin sheath

Insulating layer formed when a supporting cell wraps its cytoplasm around an axon many times

glial cells

Support cells of the nervous system; differ between CNS and PNS

Origin of CNS glia

Stem cells in neurectoderm (except microglia)

Origin of PNS glia

Neural crest

astrocytes (astroglia)

Structural support and scaffolding in development; nutritive and metabolic link between nervous tissue and vasculature; form the innermost structural component of the blood-brain barrier

glial fibrillary acidic protein (GFAP)

Unique intermediate filament of astrocytes; antibodies to it are used as a specific astrocyte label

Do astrocytes fire action potentials?

No; membrane potential fluctuates with local neuronal activity but no fast action potentials, so classically not thought to participate in neural computation

Astrocyte functions (slides)

Form part of the blood-brain barrier; regulate interstitial fluid composition; structural support of CNS; assist neuronal development; replicate to occupy space of dying neurons

oligodendrocytes

Myelinating cells of the CNS; one cell myelinates numerous axons through its individual processes

microglial cells

Resident macrophages of the brain; derived from monocyte precursors (not neurectoderm); self-renewing; phagocytic

Microglia entry and exit

Colonize the brain in embryonic life; may leave the brain but not re-enter; systemic macrophages enter only in pathology

activated microglia

State when responding to injury or infection; hallmark of chronic diseases such as Alzheimer's

radial glia

Progenitors of cortical neurons and glia; span from the apical ventricular zone to the outer surface; produce neurons and guide them into cortical layers

oligodendrocyte precursor cells (OPCs)

Fourth type of adult CNS glia (described 1983); receive direct synapses from neurons; lineage-committed to form oligodendrocytes

ependymal cells

Line brain ventricles and central canal of the spinal cord; help produce and circulate CSF

Schwann cell

PNS cell that myelinates peripheral axons; functionally homologous to the oligodendrocyte but wraps only one axon region

Schwann cell vs oligodendrocyte

Schwann cell myelinates one axon segment (PNS); oligodendrocyte myelinates multiple axons (CNS)

satellite glial cell

Supports neuronal cell bodies in ganglia; functions like CNS astrocytes (metabolic support, barrier/interface); insulates PNS cell bodies

perineurial glia

Peripheral glia (most probably) that extend the blood-brain barrier around peripheral nerves

Meissner's and Pacinian corpuscles

Their wrapped morphology is formed by specialized peripheral glial cells

peripheral microglial cells

Found in larger animals between satellite glia and large motor neuron cell bodies; thought to regulate neuronal cell size

Is there a PNS correlate of radial glia?

No; the PNS forms by chemotactically-directed cell migration

rhombencephalon

Hindbrain (3-vesicle stage); divides into myelencephalon and metencephalon

myelencephalon

Becomes the medulla; lumen becomes the caudal fourth ventricle

metencephalon

Becomes the pons and cerebellum; lumen becomes the rostral fourth ventricle

mesencephalon

Midbrain; superior colliculi, inferior colliculi, tegmentum; lumen becomes the cerebral aqueduct

prosencephalon

Forebrain (3-vesicle stage); divides into diencephalon and telencephalon

diencephalon

Thalamus, hypothalamus, epithalamus, subthalamus, optic nerve and retina, posterior pituitary, pineal gland; lumen becomes the third ventricle

telencephalon

Cerebral cortex, basal ganglia, hippocampus, amygdala, olfactory bulb; lumen becomes the lateral ventricles

superior colliculi

Midbrain (brainstem) vision structure

inferior colliculi

Midbrain (brainstem) auditory structure

tegmentum

Part of the midbrain (mesencephalon)

cerebral aqueduct

Lumen of the mesencephalon

fourth ventricle

Lumen of the hindbrain: caudal part from myelencephalon, rostral part from metencephalon

third ventricle

Lumen of the diencephalon

lateral ventricles

Lumen of the telencephalon

spinal cord (embryology)

Neural tube caudal to the rhombencephalon; lumen becomes the central canal

central canal

Ventricular lumen of the spinal cord

3-vesicle stage

Prosencephalon, mesencephalon, rhombencephalon

5-vesicle stage

Telencephalon, diencephalon, mesencephalon, metencephalon, myelencephalon

brainstem

Midbrain + pons + medulla oblongata

rostral

Toward the front of the head (nose/beak)

caudal

Toward the tail

Dorsal and ventral in the brain

Dorsal is up (top); ventral is down (bottom)

longitudinal fissure

Deep fissure partially dividing the two cerebral hemispheres

lobes of the cerebral hemisphere

Frontal, parietal, occipital, temporal

central sulcus

Separates primary motor cortex (anterior) from primary somatosensory cortex (posterior)

primary motor cortex

Anterior to the central sulcus (frontal lobe)

primary somatosensory cortex

Posterior to the central sulcus (parietal lobe)

tracts/pathways

Bundles of axons running from one nucleus to another; those exiting the CNS are spinal or cranial nerves

association, commissural, projection tracts

Three types of cerebral tracts; commissural tracts cross in the corpus callosum

nucleus

Collection of neuronal cell bodies inside the CNS (e.g., lateral geniculate nucleus)

ganglion (ganglia)

Collection of neuronal cell bodies in the PNS; ALL cell bodies outside the CNS are in ganglia

tracts (CNS)

Collections of axons in the CNS

nerves

Collections of axons in the PNS

Types of ganglia

Dorsal root, sympathetic (along vertebral column), parasympathetic (in organ walls), enteric (GI), cranial nerve ganglia