Nervous System Flashcards
- Aka “Vegetative/ Involuntary/Visceral Nervous System”
- Functional division of the Nervous System
- Innervates viscera, smooth and cardiac muscles and glands which are all involuntary
- Divided into Sympathetic & Parasympathetic
Autonomic Nervous System (ANS)
The space between ganglion and capsular cells
Perilymphatic space
Three parts of the brainstem
- Midbrain
- Pons
- Medulla oblongata
The cell membrane of axon
Axolemma
- Aka Fusiform (Pleomorphic/Polymorphic)
Cell layer - Deepest layer
- Adjacent to white matter
- Consists of intermixed cells of raging shapes (spindle- shaped) and sizes (fusiform, granules, stellate, cells of
Martinotti)
Multiform layer
- Highly vascular innermost layer
- Made up of mesenchymal cell
- Gives rise to choroid plexus
Pia mater
▪ clusters of neurons in the CNS
▪ Islands of gray matter/ clusters of nerve cell bodies in the CNS sharing a common function
▪ Edinger-Westphal nucleus, red nucleus, etc.
Nuclei
- large sponge-like cavity that surrounds the trabeculae, filled with CSF, forms a hydraulic cushion
which protects the CNS fromtrauma - Connective tissue of the arachnoid is said to be Avascular
- Arachnoid Villi/Arachnoid Granulation
Subarachnoid space
− Synthesize myelin in the CNS
− Correspond to the Schwann cells of the PNS
− Myelin in CNS is rich in glycolipids
− Myelin in PNS is rich in phospholipids
− Classification
1. Interfascicular
▪ In between the fascicles
▪ Located along andin between axons which they myelinate
- Satellite
▪ Found in the cerebrum and cerebellum
− Myelinate several axons (Schwann cells myelinate one nerve fiber)
Oligodendrocytes
The primary
type of cell that most anyone associates with the nervous system. They are responsible for the
computation and communication that the nervous system provides. They are electrically active and release chemical signals to target cells.
Neurons
Small, unmyelinated fibers conducting at 0.5 to 2 m/sec (autonomic and
some sensory fibers)
Group C fibers
- ependymal cells + underlying blood vessels of the pia mater
- CSF production
Choroid plexus
- Phagocytes
- Macrophages of the CNS
- Member of the MPS (Mononuclear Phagocytic system)
- Numerous lysosomes indicative of their phagocytic activity
- May be involved in AIDS, producing AIDS dementia
Microglia
Large fibers that conduct at 15 to 100 meters/seconds (motor and sensory
fibers)
Group A fibers
Part of the cerebral peduncle that contain certain nuclei, tracts and decussations
Tegmentum
- Lower most part of brainstem
- Between pons and spinal cord at foramen magnum
- Connected to cerebellum by inferior cerebellar peduncle
Medulla oblongata
- CENTER or MIDDLE cerebellum layer
- Purkinje cells
- pyriform or pyramidal in shape with ramified dendrites that extend into the molecular
layer
Purkinje layer
Receptor for deep pressure
Golgi Mazzoni
Connects pons and cerebellum to diencephalon
Shortest and uppermost part of brainstem
4th ventricle continues with Sylvius aqueduct at midbrain
Divided by imaginary line passing through aqueduct into ventral (cerebral peduncle) and dorsal (tectum)
Midbrain
Expanded part of pons ventrally connecting cerebrum and cerebellum via middle cerebellar
peduncle-3 parts
Basis pontis
It includes:
▪ Diencephalon
▪ Midbrain
▪ Pons
▪ Medulla oblongata
Brainstem
A brain disorder that happens when certain nerve cells in your brain misfire. it
causes seizures, which can affect your behavior or the way you see things around you for a short time. it is treated with antiepileptic drugs or surgery may be an option for people whose seizures are not controlled by medication, or who cannot tolerate the side
effects of seizure medications.
Epilepsy
Surface of the cerebrum that has folded appearance
Sulci and gyri
It is responsible for reabsorbing CSF back to venous blood sinus circulation
Pacchionian granulations
− Short axons
− Terminates within the same vicinity
− E.g. Purkinje cells of cerebellum
Golgi Type II
- Made up several fasciculi as bundles of nerve fibers covered by dense CT (epineurium) then
gives off septa - Perineurium surrounds the bigger bundles of nerve fibers, then sends finer septa
- Endoneurium that surrounds individual nerve fibers
- Vasa Nervorum blood supply to the nerve; Nervi Nervorum innervates the nerve
Nerve Trunk
- Made up of small stellate granular cells
- Aka small stellate granular cell layer
Internal granular layer
Sensory organs found in the conjunctiva and external genitalia
End bulb of Krause
The association of the nerve cell bodies with the glial cell
Neurothil
Located at the Dorsum of the brainstem at
the pons and is connected via cerebellar
peduncles
Coordinates muscular activity
Maintains posture and equilibrium
Consists of convoluted folds called the Cerebellar Folium and this is separated by Sulci.
Cerebellum
A cellular sheath made up of squamous cells that
forms a semi-permeable barrier, characterized by
the abundance of myofilaments & supported by basal lamina
Perineurium
- Soma + Cytoplasm
- Contains the organelles in the fish- eyed nucleus (pale, poorly- stained with darkly staining nucleolus)
Perikaryon
- Efferent Pyramidal neurons- most conspicuous
- 1 or more cell type predominate per layer
- Horizontal and radial axons of the neuronal cells gives it Laminated Appearance
- Has 6 layers
Cerebral cortex
It conducts impulses AWAY from the CNS to the effector organ
Efferent/Motor neurons
- Structural and functional units of the NS
- Number of neurons in the body: 10^10 - 10^11 PARTS
Neurons
- Tissue that makes up the nervous system
- Basic property: Conductivity (Conduction of nerve impulses)
- Made up of cells and fibers
Nervous Tissue
- Largest part of the brain and is composed of right and left hemispheres
- Performs higher functions (Touch, vision, hearing, speech, reasoning, emotions, learning, and fine
control movement)
Cerebrum
Arachnoid + Pia mater
Leptomeninx
- Also called Plexiform Layer
- Overlying it is a delicate connective tissue in the brain called pia mater
- Basket cells, capsular substance cells
- Peripheral portion: neuroglial cells and
Horizontal Cells of Cajal (small fusiform cell)
Molecular layer
- Outermost layer of the meninges
- Thick External layer
- Consisting of dense, fibroelastic connective tissue which is
continuous with the periosteum of the skull - Around the spinal cord, the dura mater is separated from the periosteum of the vertebrae by the Epidural Space (contains a plexus of thin-walled veins and areolar connective tissue)
Dura mater
Receptor organ for touch found in finger tips, lips, palms, soles, nipple and
conjunctiva
Meissner’s corpuscle
Its grey mater is located peripherally, white mater
is located centrally
Cerebrum and Cerebellum
- Made up of loose CT
- Highly avascular
- Give rise to Arachnoid Villi
Arachnoid
− Synthesize CSF
− Cuboidal/columnar cells lining the ventricles of the brain and central spina canal that synthesize CSF
− Beneath ependymal cell layer are numerous BV that form the choroid plexus
Ependymal cells
Nerve fibers that are formed in granular layer
Mossy fibers
▪ Numerous/ branched dendrites; one axon
▪ Motor neurons of the spinal cord
▪ Internuncial neurons
▪ Most of the cells in NS are multipolar
Multipolar
▪ Betz cells in motor cortex
▪ Paired Mauthner neurons in the medulla oblongata
Giant neurons
- Innermost Layer of the meninges (rests directly on the surface of brain and spinal cord)
- Delicate layer
- Lined internally by Flattened, mesenchymally derived cells
- Pia mater + Glial Layer = Physical Barrier (separates the CNS tissue from CSF)
Pia mater
- OUTER cerebellum layer
- relatively fewer and smaller neuronal cell bodies
- many fibers that extend parallel to the length of the folium
Molecular layer
- Upwards continuation of medulla posteriorly of pons
- Along the mid line lies the Raphae nuclei
Pontine tegmentum
Part of the cerebral peduncle that contain corticobulbar, corticospinal, corticopontine
Basis pedunculi (crus cerebri)
- aka small pyramidal cell layer
- made up of small pyramidal cell
External granular layer
The tunnels covered by the Pia matter
where blood vessels penetrate the CNS
Perivascular spaces
- Abundant number of neuronal cell bodies, dendrites, initial unmyelinated portions of axons, astrocytes, and
neuroglial cells - Where most synapses occur
- Occupies the thick surface of cortex of both cerebrum and cerebellum
Gray mater
It contains polyribosomes attached to endoplasmic reticulum that indicates high metabolic activity.
Nissl bodies
Impinges on the effector organ
Axon terminal
- Region of the spinal cord that is arranged roughly in letter “H”
- Consists of dendrites, axons, supporting cells and their processes and nerve cell bodies
- As compared to cerebral and cerebellar arteries, the spinal cord doesn’t have cortex and is not layered
- Its primary significance is the site of synapse
- Consists of long slender posterior horns and short thick ventral horns joined by
horizontal gray commissure - Ventral horns have large multipolar neurons (motor) while dorsal horns (sensory)
- The central spinal cord is lined by ependymal cells
Inner (Central) gray mater
Layer of the cerebrum that contains numerous neuroglial cells and
largest pyramidal cells (especially in the motor area- Betz cells are found)
Internal Pyramidal layer
- Basal ganglia structure
- Black substance: neuromelanin in dopaminergic neurons
Substantia nigra
Receptor organ for heat sensation found in subcutaneous tissue finger tips and joint capsule
Ruffini’s end organ
− Long axons
− Originate in the CNS and terminates distant from its origin to the periphery
− e.g. Cranial nerves
Golgi Type I
It conduct impulses TOWARDS CNS
Afferent/Sensory neurons
− Largest neuroglial cell
− Take part in the formation of tight junctions that make up the BBB (fluid and electrolyte balance)
− “End-feet” impinge on BV and neuron to form the BBB
− 3 Types:
1. Protoplasmic - Forms BBB in the gray matter
- Fibrous - Forms BBB in the white matter
- Specialized Astrocytes
▪ Bergman Glial cells in the cerebellum with protoplasmic processes that extend up to the pia mater
▪ Muller cells intermediate between astrocytes and ependymal cells
▪ Pituicytes in neurohypophysis
Astrocytes
It is located between sensory and motor
neurons
Internuncial/ Interneurons/ Central/ Intercalated neurons
Part of the cerebral peduncle that contain pigmented masses of grey matter belong to extrapyramidal system
Substantia nigra
▪ In spinal and cerebral ganglia
▪ Only one process; usually the axon; no dendrites
▪ Amacrine cells of retina: no axons; have one
dendrite
▪ Ganglion cells
Unipolar/ Pseudounipolar
The cytoplasm of axon
Axoplasm
- Synthesize by ependymal cells
- CSF in Central Spinal Canal
- Central spinal canal is equivalent to ventricles of the brain
Cerebrospinal fluid
▪ 1 axon, 1 dendrite
▪ Neurons of the special senses
▪ In retinal, gustatory, vestibulocochlear, olfactory epithelium
Bipolar
- aka medium- sized pyramidal cell layer
- made up of medium- sized pyramidal cell
External pyramidal layer
- Found in midbrain
- Involved in motor coordination
- Pale pink/ red due to iron which may be present in two forms, hemoglobin and ferritin
Red nucleus
- Region of the spinal cord that contains no nerve cell bodies
- Arranged in ascending and
descending nerve fiber tracts, supporting cells and their processes.
Outer (Peripheral) white mater
Cells in the 3rd ventricle that interdigitate with the ependymal cells
Tanycytes
Consists of organs and structures located within the cranial cavity and vertebral canal. Includes brain and spinal cord
Central Nervous System (CNS)
- a.k.a “Pachymeninx”
- Avascular
- Reflection/folds give rise to venous sinuses (transverse/ sagittal/ cavernous)
Dura mater
It is made up of ependymal cells + BV that synthesize CSF
Choroid plexus
Surround the ganglion cells in the spinal cord
Capsular/ Satellite Cells
- Where large pyramidal cells are seen (Betz cell)
- Aka Ganglion cell layer
Internal pyramidal layer
Fibers that conduct impulses at 3 to 14m/sec (mainly visceral sensory fibers)
Group B fibers
Receptor organ that mediate deep pressure and found hand, foot, palms, soles, peritoneum, pleura, mesenteries, penis, clitoris, urethra, nipple, breast and pancreas
Pacinian corpuscle
Three layers of the cerebellum
- Molecular layer
- Purkinje layer
- Granular layer
− Slender cells that synthesize myelin in the PNS
− Form a sheathe called the Sheath of Schwann/ Neurilemmal sheath
− Myelin
− lipid cover rich in phospholipids in the PNS and rich in glycolipid in the CNS
− Oblique discontinuities in the Schwann sheath are called “Schmidt-Lanterman clefts”
Schwann cells
It includes organs and structures located outside the cranial cavity and vertebral canal
- Includes:
- 12 pairs of Cranial nerves
- 31 pairs of Spinal nerves
- Sympathetic, Peripheral (i.e. Auerbach’s plexus) and Spinal ganglia
- Sensory receptors (pain receptors, Meissner’s corpuscles)
Peripheral Nervous System (PNS)
- INNER cerebellum layer
- with numerous small neurons that exhibit intensely stained nuclei
Granular layer
Conducts between neurons appearing as end feet/ terminal buttons
Synapses
▪ clusters of neurons in the PNS
▪ Auerbach’s plexus, Meissner plexus, Dorsal root ganglia
Ganglia
Branches of axons
Axon Collaterals
They are known to play a supporting role for nervous
tissue. Ongoing research pursues an expanded role that they might play in signaling, but neurons
are still considered the basis of this function.
Glial cells
- Middle part of brainstem (between medulla and midbrain)
- Connected to cerebellum by middle cerebellar peduncle.
- Consists of 2 parts: Basis Pontis (ventrally) and Pontine Tegmentum (dorsally)
Pons
The six layers of the cerebrum
- Molecular layer
- External granular layer
- External pyramidal layer
- Internal granular layer
- Internal pyramidal layer
- Multiform layer
Nerve fibers that make synapses in all the layers
Climbing fibers
They are < 4 microns in diameter
Dwarf neurons
