Nervous System Flashcards
Neurons
Neurons (nerve cells) are network that form the human nervous system. They typically have numerous long processes.
Neurons form the parenchyma.
Neuron is a functional unit in both CNS and PNS.
Glial cells descriptions, functions, embryonic development, and compositions
Glial cells are supporting cells of the nerve cells which have short processes. (They are like glue)
Glial cells form the stroma
They suppport neuronal survival and activities.
They are 10X more abundant than neurons.
They develop from progenitor cells of the embryonic neural plate (neural tube and the neural crest).
They substitute for cells of connective tissue. The collagen-like structure are neuropils.
Anatomical divisions of the Nervous System
Central Nervous system and Peripheral Nervous System
Components of the Central Nervous System
Cerebrum, Cerebellum, and Spinal Cord
Components of the Peripheral Nervous System
Cranial nerves, Spinal nerves, and Peripheral nerves or Ganglia
Define Nuclei, Tracts, Ganglia, and Nerves
Nuclei are somas or cell bodies in CNS.
Tracts are collection of axons in CNS (sheathed by oligodendrocytes).
Ganglia are somas or cell bodies in PNS.
Nerves are collection of axons in PNS (sheathed by Schwann cells or neurolemmocytes).
Functional divisions of the Nervous System
- Sensory (Afferent)
a. Somatic- sensory input perceived consciously (skin)
b. Visceral- sensory input not perceived consciously (heart) - Motor (Efferent)
a. Somatic - motor outpur controlled voluntarily (skeletal muscle)
b. Autonomic Nervous System - motor output NOT controlled voluntarily (heart, gland, effectors)
Somatic (Voluntary) Nervous System and Autonomic(Involuntary) Nervous System
Remember: SAME DAVE
Division of the Autonomic Nervous System
Sympathetic division (fight, flight, freeze) and Parasympathetic division (rest and digest)
Neuronal pathways of the ANS (autonomic nervous system)
Preganglionic (cell body in CNS) and Postganglionic (cell body in a ganglion)
Depolarization Wave
Stimuli by environment changes->
Membrane Depolarization: Neurons respond by altering ionic gradient [(electrical potential) cells that rapidly change its potential are excitable]->
Action potential/ Depolarization wave/Nerve impulse
Development of Nerve tissue
Nervous tissue develops from ectoderm (outermost)[3rd week of development]->
Thickens to form epithelial neural plate [signal comes from the underlying axial structure, the notochord]->
Sides of the plate fold upward and grow toward each other medially->
Neural tube forms [within few days]- gives rise to CNS, neurons, glial cells
Neural crest (mesenchymal) above neural tube-> gives rise to PNS and non-neuronal cell types
All the rest of will become epidermis
3 main parts of a Neuron
- Cell body/ Perikaryon/ Soma - contains nucleus and organelles. Synthetic or Trophic center.
- Dendrites - elongated processes-> Receive stimuli from other neurons at synapses.
- Axon - single long processes ending at synapses. Conduct nerve impulse to other cells. May also receive information from other neurons.
Neurolemma
Neuronal cell membrane
Smallest neuron
Cerebellar granule cell
Neuronal classifications
Structural:
- Multipolar neurons- (most common) 1 axon and 2 or more dendrites (interneurons, motor)
- Bipolar neurons- 1 dendrite + 1 axon (sensory neurons of the retina, olfactory epitehlium, inner ear- SPECIAL sensory)
- Unipolar or Pseudounipolar neuron- axon bifurcates close to perikaryon. Peripheral process connects the dendrites. Central process leads to the CNS. (general sensory)- dorsal root ganglia
- Axoaxonic neuron- many dendrites but no true axon. Do NOT produce action potential but regulate electical changes of adjacent CNS neuron.
Functional:
Sensory, Interneuron, Motor Neuron
Interneurons
Interneurons:
- connect 2 brain regions to form functional circuits in CNS.
- play a vital role in reflexes
- either multipolar or anaxomic
- comprise 99% of all neurons in adults
Locations of Soma in CNS, Axons in CNS, Cell bodies in PNS, Axons in PNS
Soma in CNS are found in gray matter (cortex).
Axons in CNS are found in white matter (medulla).
- Medulla oblongata- mixture of white matter tract and gray matter nuclei
Cell bodies in PNS are found in ganglia and some sensory regions (olfactory mucosa)- (gray matter in medulla)
Axons in PNS are bundled in nerves (white matter forming a path)
In cerebellum:
Cortex: outer layer (gray mater)
Medulla: inner layer (white matter)
Nuclei: gray matter in medulla
Tract: white matter-> arbor vitae
What is Parkinson’s disease and state its treatment
Parkinson’s disease is a gradual loss by apoptosis of dopamine-producing neurons which cell bodies lie within the nucleus of the CNS substantia nigra. It is treated by L-dopa (dopamine percursor)
Describe the cell body of a typical neuron with regard to its nucleus, cytoplasm, golgi, mitochondria, cytosketelal components, and pigmentation
Nucleus- unusually large, euchromatic (intense synthetic activity), prominent nucleolus
Cytoplasm- numerous free polyribosomes & highly developed RER (active production of cytoskeletal proteins & proteins for transport and secretion). Basophilic (chromatophilic substances or Nissl bodies) are abundant in large neuron cells like motor neurons.
- Axon hillock- origin of axon
Golgi apparatus- is only found in cell body
Mitochondria- can be found throughout the cell (abundant in axon terminals)
Microtubules, Actin filaments, Intermediate filaments (Neurofilaments- type IV intermediate filaments) are abundant in both cell body and processes
Lipofuscin- residual bodies left from lysosomal digestion can be seen
Neurofilaments
Neurofilaments are Type IV Intermediate filaments (neurofibrils) that can be seen on light microscopy by a silver stain.
Function of dendrites and location of the cytoskeletal element
Dendrites are principal signal reception and processing sites of neurons. Their cytoskeletal elements are predominantly in distal region.
Dendritic spine
Dendritic spine is the initial processing site for synaptic signal. It depends on actin filaments and changes continuously as synaptic connections on neurons are modified (key important in neural plasticity), It can be visualized with silver staining through confocal or electron microscopy to see as most synapses occur.
Axolemma
Axon plasma membrane
Axoplasm
Axon cytoplasm
Axon Hillock
where concentrated ion channels generate action potential. It is the origin of axon.
Collaterals
Major branches of interneurons and some motor neurons which influence activity of many other neurons
Terminal buoton
A dilation at the end of the axon
Describe an axon with regard to its organelle and mechanism of injury
Axon is a single, long cell extension emerging from the axon hillock of the cell body. It contains mitochondria, microtubules (with kinesin and dynein), neurofilaments, transport vesicles but few polyribosomes or cisternae of RER. Maybe, myelinated by glial cells to increase the speed of action potential propagation (node of ranvier). If severed, distal part quickly degenerates and undergoes phagocytosis.
Anterograde and Retrograde transport in the axon
Anterograde transport- movement of organelles & macromolecules from cell body to synaptic terminals along microtubules via kinesin (K+ :)->
Retrograde transport- movement of macromolecules taken up by endocytosis (including virus and toxins) from the periphery to the cell body by dynein. This process can be used to study pathways of neuron (peroxidase injected into axon terminals). Rate of axonal transport=axon growth
Microtubules is the cytoskeletal component as the track
Nerve impulse
Nerve impulse or Action potential is an electrical process initiated at axon hillock when other impulses received at the cell body or dendrites meet a certain threshold. Membrane depolarization is produced by volage-gated Na+ & K+ channels in the axolemma.
Axon’s resting potential
-65mV (electical difference) as K+ is many times greater than the extracellular concentration
Describe the components of the eletrical and chemical synapse
Threshold->
Voltage-gated Na+ channels open->
Influx of Na+
Axoplasm shifts the resting potential from -65mV to +30mV (depolarization)->
Voltage-gated Na+ channels close & K+ channels open->
Returns to resting potential->
Refractory period wherein neuron is ready to repeat the process & generate another action potential->
Impulse arriving at the synaptic nerve endings promote the discharge of stored neurotransmitters->
Nerve impulse opens Ca2+ channels->
Ca2+ influx NT release by exocytosis->
NT diffuses across the synaptic cleft->
NT inhibits or stimulates action potentials
Describe the chemical synapse component to application in anesthesia
Local anesthesia are low molecular weight molecules that bind the voltage regulated Na+ channels to the axolemma interfering the sodium ion influx inhibiting action potential.
Describe excitatory and inhibitory neurotransmitters
Excitatory NT opens postsynaptic Na+ channels that causes Na+ influx which then causes depolarization.
Inhibitory NT opens Cl- channels that causes Cl- influx (or other anion) which then causes hyperpolarization
Synapses
Synapese are sites where nerve impulse are transmitted from one neuron to another or to other effector cells. Its structure ensures transmission is unidirectional. It converts an electrical signal from presynaptic cell to chemical signal that affects the post-synaptic cell.
Synaptic cleft: 20-40nm gap
Neurotransmitters
NT are small molecules that bind specific receptor proteins to either open or close ion channels or to initiate secondary messenger cascade.
Components of synapse
Presynaptic axon terminal (terminal buoton)- contains mitochondria & numerous synaptic vesicles
Synaptic cleft- separates pre and post synaptic membrane
Postsynaptic cell membrane- contains receptors and ion channels
Ways NT are cleaned up at synapses
a. Diffusion – from greater to lesser concentration. The only method of clean up for nitric oxide and endocannabinoids which are lipid soluble
b. Enzymatic degradation – NMJ with acetylcholinesterase like PACMAN 😊 e.g. MAO (Monoamine Oxidase) uses oxygen to clip amine group off of mono amines
- Occurs within the neuron (it’s a mitochondrial enzyme)
- Targets for Monoamine oxidase inhibitors
c. Reuptake – transporter or method on presynaptic that picks up neurotransmitter either for recycling or enzymatic breakdown. Common target for drugs such as SSRI (selective serotonin reuptake inhibitor)
d. Glial activity
e. Endocytosis of receptor-NT complex by postsynaptic cell
SSRIs
Selective Serotonin Reuptake Inhibitor is a treatment for depression and anxiety. It augments level of serotonin at postsynaptic membrane by inhibiting reuptake by presynaptic membrane.
Types of synapses
- Axosomatic- Axon to cell body
- Axodendritic- Axon to dendritic spine
- Axoaxonic- Axon to axon (modulates synaptic activity)
Depending on the type of NT if it can stimulate or inhibit action potential
Neuropil
Network of fine cellular processes emerging from neurons & glial cells that resembles collagen by light microscopy
Describe the CNS glial cells
- Oligodendrocytes- Origin: neural tube. Extend many processes-> becomes sheet-like-> wraps a nearby CNS axon-> most cytoplasm moves out of the growing extension-> leaving cell membrane (myelin). Predominant glial cells in white matters. Morphology in light microscopy: small cells with rounded, condensed nuclei & unstained cytoplasm (d/t abundant Golgi). Funtions:
- Myelin production in more than 1 axon
- Electrical insulation
- Astrocytes- Origin: neural tube. Large # of long radiating, branching processes. Glial fibrillary acid protein (GFAP) makes up bundles of intermediate filaments located at proximal region (unique marker for astrocytes). Distal lack GFAP which then is not readily seen by microscopy and its synaptic sites. Most common glial cells of the brain. Fibrocytic astrocytes have long delicate processes, abundant in white matter. Protoplasmic astrocytes have many short processes, predominates in the gray matter. Astrocytes communicate via the gap junctions.
- Ependymal cells- Origin: neural tube. Columns or cuboidal cells that line the fluid filled ventricles of brain & central canal of spinal cord. In some apical ends, have cilia that facilitates movement of CSF and long microvilli involved in absorption. It is joined apically by apical junction complexes similar to epithelial cells. NO basal lamina- basal ends extend into the adjacent neuropil.
- Microglia- small cells and actively mobile processes evenly distributed throughout gray and white matter. They are NOT interconnected since they are constantly used in immune surveillance of the CNS tissue. They do NOT originate from progenitor cells but form blood monocytes. Morphology in H&E: nuclei-> small. dense, slightly elongated. Immunohistochemistry: demonstrates microglial process.
Myelin sheath
Composed of mostly lipid that which appears white under the microscope.They encapsulate the axon and facilitate rapid transmission of nerve impulse.
Astrocytoma
Atrocytoma is a tumor derived from fibrous astrocytes. They can be distinguished by their expression of the GFAP.
Fibrocytic Astrocytes and Protoplasmic Astrocytes
Fibrocytic astrocytes have long delicate processes, abundant in white matter.
Protoplasmic astrocytes have many short processes, predominates in the gray matter.
Alzheimer’s disease
Alzheimer’s disease is a type of dementia that affects perikarya and synapse d/t neurofibrillary tangles (accumulation of proteins associated with microtubules) and neuritic plaques (aggregates of B-amyloid proteins)
Functions of Astrocytes
- Extending processes affects formation, function, and plasticity of synapse
- Regulates extracellular ionic concentration around neurons-> buffering extracellular K+ levels
- Supporting movements of differentiating neurons during CNS development
- Expanding perivascular feet cover endothelial cells and modulate blood flow-> help move nutrients & wastes between neurons & capillaries
- Glial limiting membrane forms a barrier layer that lines the meninges
- Astocytic scar fills tissue defects after CNS injury
Multiple Sclerosis
MS happens when myelin sheaths are damaged by autoimmune mechanism. T lymph and microglia phagocytose & degrade myelin debris. This destruction exceeds capacity of oligodendrocytes to produce myelin & repair myelin sheaths.
Describe the PNS glial cells
- Schwann cells or Neurolemmocytes- differentiate from precursors in neural crest. This is the counterpart of oligodendrocytes. Rich with phospholipid bilayers that is repeatedly wrapped around the axon (pale staining). A schwann cell forms myelin around a portion of only 1 axon (unlike oligodendrocytes). It uses of all its body and membranes to myelinate a small segment of the axon. Functions:
- Surrounds and insulates PNS axons and myelinate large diameter axons
- Allows for faster action potential in the PNS
- Satellite cells of Ganglia- derived from embryonic neural crest. A satellite cell forms a thin, intimate glial layer around large neuronal cell body in ganglion. Functions:
- Electrically insulates PNS cell bodies
- Regulates nutrients & waste exchange for cell bodies in ganglia
Meninges and the 3 layers
Meninges are membrane of connective tissue between bone and nervous tissue that covers the CNS.
3 layers:
- Dura mater (tough mother)- Dense irregular connective tissue organized as an outer periosteal layer continuous with the periosteum of the skull and an inner meningeal layer. Along the superior sagittal surface, they separate to form a blood-filled dural venous sinus. Separated from the arachnoid by thin subdural space.
Epidural space- contains a plexus of thin walled veins and loose connective tissue that separated dura mater from the periosteum
- Arachnoid- CT is avascular- 2 components:
- Sheet of loose connective tissue in contact with the dura mater
- System of loosely arranged trabeculae composed of collagen and fibroblasts continuous with the underlying pia mater
Arachnoid villi- functions in releasing excess fluid into the blood
Subarachnoid space- sponge-like cavity that surrounds the trabeculae. Filled with CSF. Protects CNS from minro trauma. Communicates with the ventricles of the brain where CSF is porduced.
Leptomeninges- also called Pia-arachnoid which arachnoid has a very close association with the Pia mater
- Pia mater- most delicate innermost part consists of flattened, mesenchymally derived cells.
Glial limiting membrane or glia limitans- thin superficial layer of astrocytic processes that separate pia from nerve cells or fibers
Spinal Meninges:
1)Dura Mater – “Tough Mother”
- No periosteal layer
- Epidural space filled with adipose tissue
2)Arachnoid Mater – “Spider Mother”
- No arachnoid villi
- Subarachnoid space still filled with CSF
3)Pia Mater – “Tender Mother”
•Tightly adheres to spinal cord
Neural tissue composition
Cells- Neuron (parenchyma) and Glial cells (stroma)
ECM
- No fibers outside the supportive CT structures
- No ground substances
- Fluids are tightly regulated by the blood brain barrier
Depolarization
Flipping of electrochemical gradient between inside and outside of the membrane
Identify the glial cell in CNS
Astrocytes
Euchromatin and Heterochromatin within the astrocytes are sometimes described as salt and pepper
Identify the glial cell in CNS
Oligodendrocytes
Smaller-sized nuclei that are a lot heterochromatic
Much more punctate, smaller nuclei than astrocytes.
Identify the glial cell in CNS
Microglia
Can be identified by their spindly and flattened nuclei that often occur in solitary fashion
Identify the glial cell in CNS
Ependymal cells- cuboidal-looking cells that are lining the ventricular spaces of the CNS (filled with CSF)
May resemble an epithelial tissue-> but to verify, ependymal cells do not have basement membrane
Also see the lining of choroid plexus (lack BBB)
Identify the glial cell in PNS
Schwann cells-
Rich with phospholipid bilayers that is repeatedly wrapped around the axon (pale staining)
Notch in between is node of ranvier
Flattened nuclei belong to schwann cells- pushed to the periphery of the wrappings
Identify the glial cell in PNS
Satellite cells
Form a barrier between neuron cell body and extracellular environment inside the Ganglion.
Main components of white matter
- Myelinated axons (grouped as tracts)
- Oligodendrocytes
- Astrocytes and microglia
- few neuronal cell bodies
Components of gray matter
- Abundant cell bodies
- Dendrites
- Astrocytes and microglia
- Most synapses occur
Cerebral nuclei
localized variously-shaped darker areas deep in the brain containing neuronal cell bodies
Pyramidal neurons and Purkinje cells
Pyramidal neurons are multipolar neurons found in the areas of the brain including the cerebral cortex.
Purkinje cells are some of the largest neurons in the human brain found within the purkinje layer in the cerebellum.
Layers of cerebral cortex and cerebellar cortex
There are 6 layers of the cerebral cortex.
There are 3 layers of the cerebellar cortex:
- Molecular- thick outer layer with many neuropil and scattered neuronal cell bodies
- Purkinje cell layer- thin layer consists only of very large neurons (purkinje cells) with dendrites extending throughout the molecular layer
- Granular layer- thick inner layer that contains various very small, densely packed neurons (including granule cells) & little neuropil
Anterior horn, Posterior horn, and Cental canal
Remember SAME DAVE!
Anterion horn- contains cell bodies of motor neuron (axons make up the ventral root of spinal nerve)- MULTIneuron
Posterior horn- (interneurons) receive sensory fibers from neurons in the spinal (dorsal root) ganglia- MULTIneuron
- Dorsal root ganglion- collection of unipolar sensory neuron cell bodies
- Spinal nerve- combination of motor and sensory axons
Central canal- developed from the lumen of neural tube. Continuous with ventricles of brain. Lined by ependymal cells. Contains CSF.
Blood Brain Barrier
BBB is a functional barrier that allows much tighter control than that in most tissue over the passage of substance moving from blood to the CNS tissue.
Capillary endothelium is the main structural component of BBB:
Tightly sealed by occluding junctions
Little or no transcytosis activity
Surrounded by basement membrane
Limiting layer of perivascular astrocytic feet envelopes the basement membrane of capillaries
Functions:
- Protects neurons and glia from bacterial toxins, infectious agents, etc
- Helps maintain the stable composition & constant balance of ion in the interstitial fluid.
NOT present in:
- Hypothalamus - plasma components are monitored
- Posterior pituitary - releases hormones
- Choroid plexus - CSF is produced
Capillary Endothelium
Main structural component of BBB
Tightly sealed by occluding junctions
Little or no transcytosis activity
Surrounded by basement membrane
Limiting layer of perivascular astrocytic feet envelopes the basement membrane of capillaries
Choroid Plexus
Consists of highly vascular tissue projecting into large ventricles of the brain.
Found in roofs of the 3rd and 4 ventricles and part of the lateral ventricular walls
Each villus contains a thin layer of well-vascularized pia mater covered by cuboidal ependymal cells
Functions to remove water from the blood and release it to the CSF
Describe a CSF
Cerebrospinal fluid is clear fluid containing NA+, K+, Cl-, very little protein and sparse lymphocytes
Fills ventricles, central canal of spinal cord, subarachnoid and perivascular space
Provides ion required for CNS neuronal activity
In arachnoid, CSF helps absorb mechanical shock
Hydrocephalus
Decrease in absorption of CSF or a blockage of outflow from the ventricles during fetal development
Myelinated Fibers and describe the mechanism of Schwann cells
Axons of large diameter in PNS that are engulfed by neurolemmocytes
Plasma membrane of covering Schwann cells fuses with itself at the mesaxon. Wide flattened process of the cell continues to extend itself moving circumferentially around the axon many times. Multiple layers of Schwann cell membrane unite on a thick myelin sheath up to 100 lamellae.
Composed of lipid bilayer, fused proteins (major dense line seen on TEM which temporarily disappear at myelin clefts or Schmidt-Lanterman cleft for membrane maintenance)
Myelin is formed around 1 axon.
Composition of a Schwann cell, function of Myelin sheath, description of node of ranvier
A Schwann cell is surrounded by an external lamina containing type IV collagen & laminin (like basal lamina of epithelial cells)
Myelin sheath serves to insulate axons* and *maintain a constant ionic microenvironment most suitable for action potential
Nodes of ranvier (nodal gap) of where axon is only partially covered by interdigitating Schwann cell processes. Axolemma is exposed to ions in the interstitial fluid. Much higher concentration of voltage-gated Na2+ channels which renews action potential and produce saltatory (jumping) conduction.
Intermodal segment- length of axon ensheathed by 1 Schwann cell
Unmyelinated Fibers
In PNS, the glial cells do not form the multiple wrapping of a myelin sheath. Each Schwann cell encloses portion of many axons with small diameter. Without thick myelin sheath, nodes of ranvier are not seen. Have evenly distributed voltage-gated ion channels. Impulse conduction is NOT saltatory and much slower.
Illustrate and describe supporting tissues of the nerve
Nerves- bundles of nerve fibers in PNS. Whitish glistening appearance because of myelin and collagen content.
Endoneurium- external lamina of Schwann cells. Consists of reticular fibers, scattered fibroblasts, and capillaries. Loose connective tissue to reticular connective tissue.
Perineurium - sleeve that covers fascicles (bundles of axons with Schwann cells). Contains flat fibroblasts and edges are sealed together by tight junctions. Dense irregular to loose connective tissue. 2-6 layers of this make up the blood-nerve barrier.
Epineurium - Dense irregular connective tissue- toughest of all the layers- fibrous coat of peripheral nerves that fills the space between fascicles.
Describe Ganglia and state the 2 types
Ganglia is an ovoid structure containing neuronal cell bodies + glial satellite cells supported by delicate connetive tissues surrounded by dense capsules. Relay stations to transmit nerve impulses.
- Sensory Ganglia- receive afferent impulse that go to the CNS. Associated with cranial nerves (cranial ganglia) & dorsal roots of the spinal nerves (spinal ganglia)[unipolar cell body]. Relay information from ganglion’s nerve endings to the gray matter of the spinal cord via synapses with local neurons.
- Autonomic ganglia- affect the activity of smooth muscle, secretion of some glands, heart rate and other involuntary activities to maintain the body’s homeostasis. Smaller bulbous dilations in autonomic nerves [multipolar neurons]
Intramural ganglia- autonomic ganglia that are located in the walls of digestive tract
2 neuron circuits:
- Preganglionic fiber - located in CNS. Axon forms a synapse with Postganglionic fiber (chemical mediator is acetylcholine)
- Postganglionic fiber - located in peripheral ganglion system
2 parts of Autonomic ganglia
- Sympathetic part/division- preganglionic nerves are in thoracic and lumbar segments of spinal cord. 2nd neurons are located in small ganglia along vertebral column
- Parasympathetic part/division- preganglionic nerves are in medulla, midbrain, & s_acral portions of spinal cord_. 2nd neurons are located within the affector organs (ex. stomach or inttestines). May lack distinct capsules altogether
Neural Plasticity
process controlled by several growth factors produced by both neurons and glial cells called Neurotrophins
Ependyma
where neural stem cells are located that supply new neurons, astrocytes, and oligodendrocytes in adult CNS
Describe Regeneration after injury to axon
Injury to CNS or PNS->
(when neuronal cell body is intact)
2 weeks: Chromatolysis ( color degeneration d/t RER degeneraion)- cell body swells lightly. Nissl bodies is initially diminished. Nucleus migrates to a peripheral position within the perikaryon->
Nerve fibers distal to injury degenerates along with its myelin sheath->
Debris is phagocytosed by macrophages->
3 weeks: Muscle fiber shows denervation atrophy but Schwann cell or Oligodendrocyte proliferates to form a component cord penetrated by the growing axon->
3 months: Regeneration success and functional connections with muscle fibers are restored.
Neuroma
swelling that happens from newly growing axon that form extensive gap between distal and proximal segment of cut or injured peripheral nerves. Source of spontaneous pain. Can happen when sensory fibers grow into columns formerly occupied by motor fibers connected to MEP. Function of muscle will not be reestablished
Identify the dark staining and the pink staining regions
Dark staining- cell bodies of neuron
Pinkish- neuropil (neuron extension and glia)
Identify the classification of neurons
Polygonal structure with extension-> cell body of neurons-> multipolar neurons
Clear area on the center of the body- nucleus with the nucleolus
Nissl bodies- basophilic staining-> quite active in terms of transcription and translation
Identify the cells in the backround
Glial cells on the background
Salt and pepper speckles-> nuclei that belong to the astrocytes
More punctate, smaller more condensed nucleoli-> belong to the oligodendrocytes
Background-> all neuropil (dendrite extensions, axon extensions and glial cells)
Microglia or endothelia?
Endothelial cells lining the capillary-> when flattened cells are grouped together and not solitary
When its solitary-> it belongs to Microglial cells
Classify this neuron from gray matter
Multipolar neuron in gray matter
Identify backgound cells
Astrocyte nuclei-> more euchromatic
Oligodendrocyte nuclei->smaller, darker, more punctate, heterochromatic
Neuropil-> fibery structures in the backgound
Identify the light staining areas
Many tracts emerging from the ventral horn of the spinal cord
Pale staining structures-> myelin sheaths by the oligodendrocytes
Identify the blue structure
Meninges
Identify cell bodies
Dorsal root ganglion (spinal ganglion)-> oval and large cell bodies-> unipolar neurons-> site where unipolar cell bodies are all aggregate together in the PNS
Identify the glial cell
glial cells (satellite cells) outline just outside of the unipolar neuron cells
neuron cell bodies- large euchromatic nucleus with punctate nucleolus & large cytoplasm containing lots of Nissl bodies
Identify the middle portion
Central canal-> contains CSF-> lined by ependymal cells
Describe the cerebrum neural tissue
Gray matter- more cell bodies
White matter- more axons
Gyri- folds or hills 😉
Sulci- grooves or sulken or sunken 😊
NEURAL TISSUE CEREBRUM IS QUITE VASCULAR!
Identify cell pointed
Oval, large, euchromatic of neuron cell bodies-> distinct and punctate nucleoli-> cytoplasm are basophilic d/t Nissl bodies
Identify cell pointed
Astrocytes-> euchromatin, heterochromatin cytoplasm, punctate nucleoli
Identify cell pointed
Oligodendrocytes
Identify the region in cerebrum
White matter-> majority of nuclei are those of glial cells
Identify the location and name the external layer
Cerebellum-> with gyri and sulci too
External layer: Molecular layer contains lots of neuron cell bodies, neuropil
Identify layer
2nd layer: Purkinje cell layer-> contains interneurons (multipolar Purkinje cells) that have elaborate dendrites that extend to the molecular layer and axon fibers that branch extensively into the inner layer of cerebellar cortex-> allows communication and neural network and inner most layer
Identify layer
Inner layer: Granular cell layer-> most cellular-> layer that contains the smallest sized neuron cell bodies in our anatomy d/t the granular appearance
What does the medulla of the cerebellum comprise of?
Medulla of the cerebellum-> comprised of white matter
Classify neuron and state location
Unipolar neurons-> from the cell body, short cytoplasmic extension coming out & branching immediately into the proximal and distal branches with the proximal branch plugging into the spinal cord synapse with the multipolar interneurons that are in the dorsal horn of the spinal cord
Euchromatic nuclei-> highly active
Punctate nucleolus-> suggesting construction of ribosomes
Speckled cytoplasm-> full of Nissl bodies consistent
Found in Dorsal Root Ganglion
Identify pale staining regions
Axons-> Pale-staining regions are with myelination
Identify the structure pointed
Node of ranvier-> where axon cell membrane would depolarize
Identify the structures on the topmost and bottommost parts of the image. State how to distinguish from different connective tissue and muscle types.
Perineurium which contains flat fibroblasts
To distinguish: Smooth muscle will have more regularity in shapes of the nuclei and tissue will be more cell dense and no pale staining regions
Dense irregular CT-> collagen fibers run in 1 parallel direction, and it will be less cellular. Also, nuclei will be flatter and highly condensed (fibrocytes)
Identify the structures
- Dura mater- dense CT
- a. epidural space (above the dura)
- b. subdural space (below the dura
-
Arachnoid mater- delicate loss CT
* d. subarachnoid space- actual space filled with CSF - Pia mater- delicate and thin CT
Identify the structures
- Epineurium- dense CT
- Perineurium- around a fascicle
- Endoneurium- delicate basement membrane around each axon or Schwann cell
Action of Acetylcholine
Binds ACh receptors (cholinergic receptors) in PNS to open ion channels in postsynaptic membrane and stimulate muscle contraction
Actions of Glutamate, Gamma-aminobutyric acid (GABA), and Glycine
These 3 are amino acids (NH3-COOH-R) that act as important transmitters in the CNS:
- Glutamate- Most common NT in the brain. Opens Na+ channels which excites activity in neurons to promote cognitive functions in the brain (learning and memory)
- GABA- Primary inhibitory NT. Synthesized from glutamate which opens or closes various ion channels. Also influences muscle tone.
- Glycine- Opens Cl- channels which inhibits activity between neurons in the CNS, including retina
Monoamines
Synthesized from an amino acid by removing carboxyl group and retaining the single amine group. Also called biogenic amines
Serotonin or 5-hydroxytryptamine (5-HT) is a monoamine which modulates actions of the NT. Its functions are related to sleep, appetite, cognition (learning and memory), & mood.
Catecholamines
These are distinct group of monoamines:
Dopamine- produces inhibitory activity in the brain which opens K+ channels & closes Ca2+ channels. It plays a role in cognition (learning and memory), motivation, behavior, & mood
Norepinephrine (Noradrenaline)- NT of PNS(sympathetic division of autonomic nervous system) and specific CNS regions
Epinephrine (Adrenaline)- Various effects on the CNS, especially the spinal cord, thalamus and hypothalamus
Neuropeptides
Small polypeptide that act as signals to assist in and modulate communication among neurons in the CNS:
Enkephalin- Regulate response to noxious and potentially harmful stimuli
Neuropeptide Y- Involved in memory regulation and energy balance (increased food intake and decreased physical activity)
Somatostatin- Inhibits acitivites of neurons in specific brain areas
Substance P- Assists with pain information transmission into the brain
Cholecystokinin (CKK)- Stimulates neurons in the brain to help mediate satiation and repress hunger
Beta-endorphin- Prevents release of pain signals from neurons and fosters a feeling of well-being
Neurotensin- Controls and moderates the effects of dopamine
Actions of Adenosine and Nitric Oxide NT
Adenosine- part of nucleotide which inhibits activities in certain CNS neurons
Nitric oxide- Involved in learning and memory. Relaxes mucle in the digestive tract. Important for relaxation of smooth muscle in blood vessels (vasodilation)
