Nervous System Flashcards
What are the branches of the nervous system?
What are the different meninges?
- dura mater: outermost layer
- arachnoid: membrane attached to dura mater
- pia mater: innermost layer, highly vascular, adherent to brain and spinal cord
- leptomeninges - arachnoid + pia mater
- subarachnoid space: contains CSF
What are the embryonic brain divisions and their derived brain structures?
- forebrain
- telencephalon: cerebrum, basal nuclei, hippocampus, + amygdala
- dincephalon: thalamus + hypothalamus
- midbrain
- mesencephalon: midbrain
- hindbrain
- metencephalon: pons + cerebellum
- myelencephalon: medulla oblongata
What are some features of the surface of the brain?
- gyrus/i + sulcus/i of main brain
- folia + sulci of cerebellar cortex
- arbor vitae “tree of life” cross-section
What are the different kinds of nervous tissue and the system they are part of?
What is white matter? Grey matter?
- white matter: formed by dense accumulations of myelinated axons. Myelin sheath is rich in lipids so has a white appearance
- grey matter: rich neuronal cell bodies , glial cells, and neuropil. Neuropil represents the axons, dendrites and cytoplasmic projections of glial cells that form the background matrix to neuronal cell bodies within the grey matter.
T/F: white matter is peripheral in the brain and central in the spinal cord
- False; white mater is peripheral in the spinal cord and central in the brain
- grey matter is peripheral in the brain and central in the spinal cord
T/F: the cells of the CNS that are sensitive to hypoxia are of mesodermal origin
- False; ectodermal origin
- ectodermal origin: neurons, astrocytes, oligodendrocytes
- mesodermal origin: microglia, vascular endothelium
What cells compose the CNS?
- neurons
- glial cells
- ependymal cells
- endothelial cells
- pericytes of blood vessels
What are neurons?
- functional cells of the nervous system in which two protoplasmic properties are highly developed
- irritability: generation of an impulse
- conductivity: ability to transmit such a impulse from one locality to another
- neurons are dispersed through the CNS and grouped in specific areas in the PNS
How are neurons distributed?
- individually
- layers (cortex)
- groups
- nuclei (CNS)
- ganglia (PNS)
Describe the structure of a neuron
- parts:
- perikaryon
- nucleus
- nucleolus
- dendrites
- axons
Describe the structure of a soma
- euchromatc nucleus w/ prominent nucleolus
- basophilic cytoplasm: nissl substance, SER, and ribosomes
- lipofuscin: “wear and tear” pigment
- cell body = perikaryon/soma: contains nucleus + organelles, axons and dendrites branch off it
What are the arrows pointing at?
- yellow: lipofuscin
- blue: nucleolus
- green: nucleus
What is shown in this image?
- neurons + glial cells
What are some features of synapses?
- specialized junctions with other cells that are along the length or at end of an axon
- act as transmission points for electrical impulses
- can trigger the generation of an action potential in the postsynaptic cells, can be excitatory or inhibitory
- synapses at end of an axon or axon branches are swollen into a club shape, called boutons terminaux
- those along the length of the axon result in varicosities (swellings) called boutons en passant
What are structures of synaptic knobs?
- 3 parts:
- presynaptic part: termination of axon (bouton terminaux)
- intersynaptic cleft
- postsynaptic cleft (dendritic thorn)
T/F: stimulatory synapse vesicles contain GABA, inhibitory synapse vesicles contain acetylcholine
-false; stimulatory = ACh, inhibitory = GABA
Neurons can synapse with:
- neurons
- muscle
- glands
What are the sense organs of the skin?
- thermoreceptor: sense heat or cold
- meissner’s corpuscle: senses touch
- nociceptor: sense pain
- pacinian corpuscle: senses pressure
What are functions of oligodendrocytes?
- myelin sheath to axons
- unlike Schwann cells (PNS), they form myelin sheaths for several axons at once (“octopus” shape)
What is shown? What are some features?
- oligodendrocyte
- small dark nuclei (between myelin sheaths or sounds neurons)
- can be destroyed by viruses/toxins resulting in primary demyelination
What are some functions of microglia?
- immunosurveillance
- immunoregulation
- reparative —> phagocytic
- gitter cells (myeophages) —> activated during necrosis/inflammation —> globular and swollen after having phagocytized debris from injured cells
What is shown? What are some features?
- microglia
- derived from blood-borne monocyte
- resident macrophage of CNS
- Gitter cells: note cytoplasmic vacuolation due to ingestion of cellular debris
What is shown?
- microglia
- activated Gitter cells (macrophages) in a area of brain tissue necrosis
What is shown?
- microglia
- activated microglia cells in a myelin sheath (“myelophages” w/ a “digestion chamber”)
What are some features of astrocytes?
- CNS counterpart of the fibroblast
- involved in cell communication and the functioning of blood brain barrier
- 2 types:
- protoplasmic (grey matter)
- fibrillation (white matter)
- glial fibrillary acidic protein (GFAP) staining
What is shown?
- astroytes
What are functions of astrocytes?
- transport of nutrients
- part of bbb
- antigen presentation
What are features of ependymal cells?
- form an epithelium that lines ventricular cavities within the brain and central canal of the spinal cord
- typically cuboidal or columnar with numerous motile cilia on their apical surfaces
- central canal ependymal cells have cilia to help the circulation of the CSF
- limited regenerative capacity: do not typically undergo mitotic proliferation
What is shown?
- ependymal cells (in spinal cord central canal)
What are functions of ependymal cells?
- produce CSF
- important barrier function that protects neural tissue from potential harmful substances (mechanism not really understood)
What is shown? What kind of epithelium? What are the arrows indicating?
- ependymal cells
- simple columnar epithelium
- motile cilia
What are features of the ventricular system?
- lined by ependymal cells
- communicates with the subarachnoid space
- circulates CSF
What are features of cerebral spinal fluid?
- produced in choroid plexus by specific modified ependymal cells
- produced and MUST BE drained at a constant rate
- the total volume of CSF is formed and renewed at least 3X a day
- can be sampled for clinical evaluation
What are functions of CSF?
- medium for filtration system: facilitates removal of metabolic waste from the brain and exchange of biomolecules into and out of the brain
- helps maintain the extracellular environment needed for the brain to function optimally (homeostasis)
- cushions CNS
Where and how is CSF produced?
- formed as plasma: filtered from blood though the choroid plexus ependymal cells
- produced by a mechanism that involves active secretion of Na+ into the ventricles —> water follows the resulting osmotic gradient
**plexus (Latin for brain) is a branching network of the vessels or nerves
What is shown? What kind of epithelial cells? What kind of junctions and what is their purpose?
- choroid plexus
- a layer of cuboidal epithelial cells surrounding a core of capillaries and loose connective tissue
- the epithelium: specific modified ependymal cells: have microvilli and are linked to adjacent cells by TIGHT junctions (unlike th ependymal)
- these tight junctions prevent the majority of substances from crossing the cell layer into the CSF: blood-CSF barrier
The choroid plexus folds into many villi around each capillary, creating frond-like processes that project into the ventricles. What does this do? What helps with this process?
- increases the surface area of the choroid plexus
- along with a brush border of microvilli
T/F: There is only one choroid plexus
- false; there is one choroid plexus in each of the 4 ventricles in the brain
- it is present in all parts of the ventricular system (except the cerebral aqueduct, frontal horn and occipital horn of the lateral ventricles)
Where is CSF resorbed?
- in the subarachnoid space into venous circulation
What are some features of the blood-cerebrospinal fluid barrier and brain-CSF boundary ?
- pair of membranes separates blood from CSF and CSF from brain tissue
- blood-CSF boundary at the choroid plexus is a membrane composed of ependymal cells and tight junctions that link them (choroid plexus capillaries are fenestrated and don’t have tight junctions)
- brain-CSF boundary is the arachnoid membrane
What are functions of the Blood-CSFB and Brain-CSFB?
- prevent passage of most blood-borne substances into brain
- facilitates transport of different substances into the brain due to distance structural characteristics between the two barriers (for a # of substances, BCSFB is primary site of entry into the brain)
- facilitates removal of brain metabolites and metabolic waste into blood
- modulates entry of leukocytes from the blood into the CNS
The choroid plexus cells secrete ____________, which recruit ________________, among other cells, to the brain. What does this have implications in?
- cytokines
- monocyte-derived macrophages
- normal brain homeostasis and neuroinflammatory responses
What are the layers of the cerebellum (w/ arbor vitae)?
- cortex cerebelli: grey matter (6 layers)
—> outermost to innermost
- molecular layer: basket cells
- ganglionic cell layer: purkinje cells
- granular cell layer: granule cells in stratum granulosum
- white matter core: myelinated nerve fibers
What are the labels 1, 2, + 3 in this image of a cerebellum?
- 1: molecular layer: basket cells
- 2: ganglionic cell layer: purkinje cells
- 3: granular cell layer
What structure is shown in this image? Label the arrows
- purkinje cell (blue)
- green: molecular layer
- red: dendrites of purkinje cell
- yellow: neuron of purkinje cell
- black: granular cell layer
What is this image of? Label the arrow and numbers
- cerebellum
- arrow: purkinje cell
- 1: molecular layer
- 2: ganglionic cell layer
- 3: granular cell layer
What is this image of? (Be specific). Label the numbers and arrows. What is the importance of the yellow label?
- cerebellum, fetal/newborn
- 1/arrows: external granular layer
- 2: molecular layer
- 3: ganglionic cell layer
- 4: granular cell layer
- yellow: exterior cortical lamina - additional exterior layer tat populates the internal granular layer during early postnatal development - eventually disappears
What are the cerebral cortical layers?
What is shown in this image?
- a nucleus in the CNS: a cluster of neurons, located deep within the cerebral hemispheres and brainstem that are performing a common function
Describe the structure of the spinal cord
- peripheral white matter, central grey matter
- central canal: opening in the horizontal bar of the grey matter, remnant of the lumen of the embryonic neural tube
- anterior horns: grey matter of the legs of the “H”, contains motor neurons whose axons make up the ventral roots of the spinal nerves
- posterior horns: grey matter of the arms of the “H”, receives sensory fibers from neurons in the spinal ganglia (dorsal roots)
- lined with ependymal cells
T/F: Spinal cord neurons are large and pseudo-unipolar, especially in anterior horns where large motor neurons are found
- false; large and multipolar
What is this? Label some key features
What are the functional divisions of the peripheral nervous system?
- somatic nervous system: a one neuron system that innervates (voluntary) skeletal muscle or somatosensory receptors of the skin, muscle, and joints
- autonomic nervous system: a two neuron visceral efferent system, that innervates cardiac and smooth muscle and glands. It is involuntary and has two major subdivisions:
- sympathetic (thoracolumbar)
- parasympathetic (craniosacral)
What are features of nerves in the PNS?
- collection of axons/dendrites outside the CNS
- consists of axons, dendrites, blood vessels, glial cells, and connective tissue investments
- endoneurium, perineurium, epineurium,
- cells present: endothelial cells, fibroblasts, and Schwann cells
What are features of ganglia in the PNS?
- collections of neuronal cell bodies and processes found outside the CNS
- cells of a ganglion: neurons, neuroglia cells (amphicytes), Schwann cells, endothelial cells. Axons also present
- two types:
- sensory (craniospinal)
- autonomic
What are the glial cells of the PNS and some features?
- schwann cells:
- envelope nerve fibers in the PNS
- wind repeatedly around a nerve fiber
- produces a myelin sheath similar to the ones produced by oligodendrocytes in the CN
- assist in regeneration of damaged fibers
- consists of plasma membrane of glial cells
- 20% protein and 80% lipid
- satellite glial cells (amphicytes):
- surround the neurosomas in ganglia of the PNS
- provide electrical insulation around the soma
- regulate the chemical environment of the neurons
Describe myelination
- production of myelin sheath (by schwann cells/oligodendrocytes)
- begins around the 14h week of fetal development (in humans)
- proceeds rapidly during infancy
- completed in late adolescence
- dietary fat is important to nervous system development
What is this structure? Label some important features
- nerve fiber
What is this structure? What are the black rings?
- peripheral nerve
- myelin sheaths
What is shown in this image?
- myelin sheath
What is this structure? what are the purple stained structures?
- peripheral nerve
- schwann cells
What can happen if the myelin sheath is damaged?
Label the yellow and blue spaces
What structure is shown? What are some features?
- myenteric plexus
- situated between the inner and outer longitudinal layers of the tunica muscularis
- helps control peristaltic movement of the gastrointestinal tract
