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76 Cards in this Set
- Front
- Back
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What is a Bipolar neuron. Give three locations in the body where these are found.
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Cell body has an axon on one end, dendrites on the other. Found in the retina, olfactory epithelium, and acoustic ganglia.
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Define a multipolar neuron. Where in the body are these neurons found?
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Cell body has an axon on one end, and two or more dendrites on the other. Found everywhere in the CNS. These are the most abundant neurons.
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Define psuedounipolar neuron. Where are these found in the body?
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Single process is divided into two, resulting in a t shaped structure. These are found in the cranial and spinal ganglia of the PNS
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What do interneurons do? Where are they found?
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They transmit signals within the area of the perikaryon. They link primary sensory neurons with final end motor neurons.They are defined by their processes being completely confined to one region, like the spinal cord or an olfactory lobe.
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What portion of a nerve cell receives excitatory or inhibitory stimuli from other cells?
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The Perikaryon
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What is the primary substance found in the nucleus of a nerve cell?
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Euchromatin and nucleolus (cat's eye)
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What are Nissl Bodies?
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Basophilic RER and free ribosomes.
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What is Chromatolysis?
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A reduction in the number of nissl bodies as a result of cell injury.
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Where in the nueron are golgi bodies found? Mitochondrion?
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Golgi bodies are found only in the perikaryon while mitochondria are also found in the axons, dendrites, and axon terminals.
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What structures are used in immunocytochemistry to identify neurons?
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Neurofilaments (which form neurofibrils)
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What is the function of microtubules in neurons?
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Structural mainly and also used in mitosis, cytokinesis, and vessicular transport.
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What is the function of dendrites emanating from the perikarya?
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Increase the receptive capacity of the neuron
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What cellular structures are found in dendrites? What structure is not found in dendrites?
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RER and free ribosomes, but not golgi apparatus.
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How are neurofilaments and microtubules aligned in a neuron?
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along the long axis of the dendrite.
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What structures is the axon hillock devoid of?
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RER and free ribosomes (unlike dendrites!)
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What is the initial segment?
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The region of the axon between the axon hillock and the point at which the axon becomes myelinated.
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Which glial cells can undergo cell division? Can neurons divide?
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Astrocytes can divide. Neurons can not divide.
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What is the only way to tell between an oligodendrocyte and an astrocyte histologically?
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Immunocytochemistry
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What is the largest of the glial cells? what is it shaped like and what is its function?
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The astrocyte. It is stellar (star) shaped and it terminates at neurons and blood vessels. It aids with ion flow at nodes of ranvier.
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Where are protoplasmic astrocytes found? What is their function and how can you distinguish them from fibrous astrocytes?
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Grey Matter. They cover non-synaptic neuronal surfaces. They have a clearer cytoplasm than astrocytes
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Where are fibrous astrocytes found? How do they differ from protoplasmic astrocytes?
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Mostly in white matter, some gray matter. They have higher levels of Glial fibrillary Acid Protein, an intermediate filament protein.
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What is glial fribriallary acidic protein used for in histology?
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immunocytochemically identify astrocytes in brain tissue
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What cell helps form the blood brain barrier?
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Astrocytes
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What is the role of astrocytes?
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Form Blood Brain Barrier
Repair of CNS Tissue via scar or plaque formation Fluid transport to damaged areas (import Na) |
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In what portion of the brain are oligodendrocytes found in high concentration, why?
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Corpus Callosum b/c it is highly myelinated.
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What cells become enlarged during myelination? How do you ID them immunocytochemically?
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Oligodendrocytes. Stain for any myelin protein! MAG or MBP
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What is the function of microglia?
Where are they derived from? |
Phagocytosis of damaged brain tissue.
Bone marrow |
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What cells are cuboidal or squamous in shape and line the ventricles of the brain? What fluid are they bathed in? What is their fxn?
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Ependymal cells. They are bathed in CSF. Apical surface have cilia, which move CSF.
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Explain the structure and function of the choroid plexus
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In the ventricles of the brain, the choroid plexus is formed by ependymal cells and underlying capillaries. It makes CSF
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Compare myelination in the CNS and the PNS
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In the CNS, myelin is a specialized membrane of oligodendrocytes. In the PNS, it is schwann cells that direct myelination, however, they do not ensheath the axon with the membrane of Schwann cells, rather, they use clefts of schwann cells.
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What is an internode? Node of ranvier? Paranode?
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An internode is a region that is myelinated, a node of ranvier is a region that is unmyelinated in the CNS. A paranode is a region adjacent to the node of ranvier that contains the terminal loops of myelin, contains uncompacted myelin.
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What is compaction?
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The process of major dense line formation in myelination. Critical!!!
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What is the function of the uncompacted regions during myelination?
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Delivery of nutrients to the area being compacted.
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What is the intraperiod line?
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A result of the close apposition of two adjacent oligodendroctye processes (lines in between the MDL)
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What is MS?
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An autoimmune disorder where myeline is stripped from axons via macrophages. The spaces devoid of myelin are replaced with astrocytic processes, called an MS plaque. Destroys saltatory conduction b/c no more nodes of ranvier!
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How do you stain for MS plaques immunocytochemically?
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Stain for GFAB
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At what point on the myelinated axon is that axon exposed to the extracelluar environment?
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Node of Ranvier
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What cells line the central canal of the spinal chord? Where is white matter found in the spinal chord?? Gray matter?
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Ependymal cells. White matter is on the periphery, gray matter forms the central "H"3
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What cells does gray matter contain?
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Motor neurons; receive signals from sensory neurons through the posterior horns.
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What are the two layers of the cerebellum?
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outer gray matter layer and inner white matter layer.
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What are the layers and their functions of the cerebellar cortex?
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Outer Molecular layer - receives dendrites of perkinje cells.
Central perkinje cells - just neurons inner Granule layer - recieves axons of perkinje neurons. |
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What are perkinje neurons?
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Flask like, myelinated cells that receive both excitatory and inhibitory impulses from the motor areas of the cerebral cortex.
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What is the function of the cerebellum?
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Modulates and organizes motor impulses to coordinate movement of muscle groups.
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What are the three major layers of the cerebrum?
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Outer gray matter layer, cortex, and inner white matter layer.
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What is the function of the cerebrum?
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integrates sensory input and voluntary motor movements. It coordinates complex processes such as language, learning, and memorization.
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Are schwann cells mitotic? From what tissue are they derived?
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Yes! Ectodermal tissue
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Is connective tissue found in the PNS? CNS?
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Only in the PNS - b/c it contains the mitotic schwann cell!
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Do nerve fibers in the PNS have Nodes of Ranvier? Why?
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No! B/C a nerve FIBER isn't myelinated, it is surrounded by a lamina. Ergo, no nodes of ranvier!
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What structure gives PNS nerves structural support and elasticity?
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Epineurium
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Explain the structure of peripheral nerves in the PNS
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Epineurium surrounds the peripheral nerve. The space b/t the nerves is filled with collagen, fibroblasts (hint in PNS), and blood vessels. The nerve fibers are then arranged in bundles to form nerves. Each nerve bundle, a fascicle, is surrounded by a perineurium (flattened epithelial like cells, joined by gap junctions to protect the nerve from toxic molecules). Each nerve fiber is wrapped by a schwann cell, then the SC and the Fiber is encased by the endoneurium, a CT made of reticular cells and mostly of collagen.
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What is the thin sheath of schwann cell called that surrounds the PNS Nerve fiber?
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Neurilemma.
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Where are nodes of ranvier in the PNS?
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Each schwann cells myelinates a nerve fiber at one point, thus, the nodes of ranvier are found in between each schwann cell.
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what is a schmidt lanterman cleft?
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An area on a PNS nerve fiber where myelin is not compacted and thus has some schwann cell cytoplasm. These clefts allow for raw materials to be delivered so other areas can be compacted.
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What is the ratio of Protein/Lipid in myelin in the PNS and CNS?
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30/70 protein/lipid.
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What is the major myelin protein in the PNS? Do you need MBP to make myelin in the PNS? Where do you find MBP in the PNS?
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Po, NO! In the MDL, as in the CNS
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What is a ganglion? What cells surround these?
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A collection of nerve cell bodies outside of the CNS. Satellite cell (serve as glial, supportive cells)
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What are the two types of ganglia?
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Sensory (cranial and spinal) and autonomic ganglia.
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Where are sensory ganglia found and what is their fxn?
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They are found in Dorsal Root of Spinal Nerves and cranial ganglia are in the path of cranial nerves. They send impulses to the CNS ergo Afferent.
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What kind of neurons do sensory ganglia have? Fxn?
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Pseudounipolar. Send one thin process to the CNS. The other thicker process goes to the periphery.
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Do synapses form with the perikarya of sensory ganglion neurons? Why?
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No b/c these cells do not receive impulses!
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Are autonomic ganglia found in the sympathetic or parasympathetic NS?
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Both!
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What are intramural ganglia? What are they surrounded by?
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autonomic ganglia in the walls of the digestive tract. They are surrounded by stroma (Not CT) and have few satellite cells.
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What does the submucosal plexus of Meissner and the myenteric plexus of Auerbach do?
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They contain autonomic ganglia that cause smooth muscle contraction.
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What type of neurons are found in autonomic ganglia? How are their nuclei oriented?
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Multipolar neurons. Nuclei are eccentrically oriented and the cytoplasm has fine nissl bodies.
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Are their synapses in autonomic ganglia?
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Yes!
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Can nervous tissue regenerate?
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Only some cells can - Schwann cells, glial cells, and ganglionic satellite cells. The process of degradation is called Wallerian Degradation
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When can a nerve regenerate?
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It can regenerate if the proximal segment of the axon maintains continuity with the perikaryon. Else, the distal segment is consumed by macrophages or schwann cells.
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What events occur following axonal injury?
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Chromatolysis
Decrease in cytoplasmic basophilia Increase in perikarya volume Migration of nuclei to periphery of perikarya. |
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Explain regeneration of neurons
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Schwann cells proliferate and create an endoneurium. The axons of surviving nerve cells split into neurites. The tubes guide the axon in its growth. Central tubes are then surrounded completely by schwann cells. Of all of the new fibers, only one is selected for myelination. This surviving fiber then forms new synaptic contacts.
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What are the two types of sensory receptors (give examples)?
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Encapsulated (Meissner's Corpuscle in Dermal Papillae, or Pacinian Corpucles in dermis (pressure sensitive) and Nonencapsulated (free nerve endings, like for pain and touch, like merkel's disc in basal lamina, or the hair fiber receptor).
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What is a neuromuscular spindle and what does it do?
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Structures found in skeletal muscle that relay info to cns for Maintaining muscle activity (like posture). they also regulate activity of opposing muscle groups, such as walking. They have intrafusal and extrafusal fibers. Intrafusal fibers have nuclear chains (small fibers) or nuclear bags (long chains) that are richly innervated by sensory neurons to monitor degrees of stretch.
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What is a golgi tendon organ? What does it do?
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Similar to intrafusal fiber...found at the site where muscle inserts into tendon. It is surrounded by a fibrous capsule and collagen taht connects the muscle to the tendon. Proprioceptive sensory fxn from 1b sensory fiber detects muscle stretch.
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What is a myoneural junction?
Motor unit? |
site where a short axon terminal (bouton) meets a muscle fiber.
A motor unit is where one axon meets one muscle cell. |
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If you see perkinje cells, what structure are you looking at?
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Cerebral cortex
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What protein is found at the IPL?
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PLP - Proteolipid protein.
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What neurons are found in the dorsal root ganglion?
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Psuedounipolar sensory neurons.
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