Nerve Tissue and Nervous System Review Questions

What is a ganglion, what are the types of ganglia found in the PNS, and where is the location of each type?

A ganglion is clusters of nerve cell bodies surrounded by connective tissue (except for parasympathetic ganglia). The types found in PNS are sensory ganglia and autonomic ganglia. THe sensory ganglia are when spinal nerves branch into a dorsal/ventral root, with cell bodies of sensory neurons in dorsal root ganglia, surrounded by satellite cells. the connective tissue capsule =epineurium and endoneurium present but no perineurium (so no blood-nerve barrier or fascicles). Autononic ganglia are sympathetic - similar to sensory, but smaller with less CT. Parasympathetic embedded in target organ (intramural ganglia) and may lack any CT capsule.

What type of repair is possible if a neuron is damaged by mechanical trauma or chemical insult? Why is such repair only possible in the PNS, but not in the CNS?

Axonal regeneration in PNs is possible if perikaryon destroyed, the cell dies, if axon is cut or chemically damaged in the pns the sistal part degenerates except connective tissue , schwann cells form a tube, proximal part invades the tube and may reestablish contact. In the CNS no regeneration is possible, since there are no neurolemmocytes and no CT. After two weeks chromatolysis (temporary loss of Nissl substance) occurs and the nucleus moves to periphery. macrohpages phagocytose debris and secrete neurotrophin growth factors. after 3 weeks schwann cells dedifferentiate and divide without myelin sheath, forming a tube, guiding the axon.

How are white matter and gray matter arranged in the spinal cord? What types of neuron cell bodies are found in the dorsal and ventral horns of the gray matter?

Gray matter is in the center in the form of H. the white matter is in the periphery. in the posterior dorsal horns of gray matter there are cell bodies of interneurons receiving sensory info. in the anterior ventral horns there are cell bodies of motor neurons.

Describe the mechanism for maintaining the resting potential of an axon, how this potential is disturbed by incoming signals, and the process that occurs at the axon hillock resulting in the generation of an action potential. What ion is actually responsible for the action potential? How is the resting potential re-established?

In a resting neuron Na+ is low in cytoplasm and K+ is high, due to Na/K pump. The plasma membrane is polarized with a resting potential of -65 mV (at rest) due to Na+/K+ pump ,anionic proteins, and Na+ leakage. Synapses on dendrites and cell body cause transient influx of Na+ which leads to depolarization(EPSP) or efflux of K+ leads to hyperpolarization (IPSP). The axon hillock sums EPSPs/IPSPs. when voltage gated Na+ channels are greater than -55mV closed, if resting potential decreased to threshold less than 55mV , voltage gated na+ channels briefly open, allowing a massive influx of Na+ so the membrane potential reverses to +30mV (action potential); Na+ channels then shut. This electrical disturbance moves rapidly (100 m/sec) to axon terminal and can't go backwards because Na+ channels are temporarily refractory. THe resting potential re-established by opening K+ channels which leads to a massive efflux.

What are 3 physiological characteristics of neurons that distinguish them from other types of cells, e.g., from epithelial cells?

Neurons are electrically excitable (respond to stimuli with an electrical signal b altering the ionic gradient across the plasma membrane, has a high atp demand -die within minutes if deprived. and they are fully differentiated - can't divide and not replaced if they die.

What is the chemical composition of CSF, where is it formed, how does it circulate, and where is it returned to the blood?

The CSF bathes the brain and the spinal cord. it circulates through ventricles, central canal, and perivascular spaces. it is mainly water and ions. there is 500 ml formed per day in teh choroid plexus in lateral ventricles and third and fourth ventricles. it is returned to the blood in arachnoid villi. the villi are covered by ependymal cells enclosing pia mater and capillary

What is the structure and function of the blood brain barrier?

The blood brain barrier structure is endothelial cells of capillaries, lack of fenestrations, joined by tight junctions, no pinocytotic transcytosis, wrapping by perivascular feet of astrocytes. They function to block hydrophilic substances in blood from entering the brain like toxicants and neurotransmitters (ex. glutamate)

What are the components of the central nervous system and the peripheral nervous system?

The components of CNS are cerebrum, cerebellum, spinal cord. The components of PNS are cranial nerves, spinal nerves, and ganglia

What are the components of a nerve? What 2 types of cells make up a nerve fiber?

The components of a nerve are nerve fibers and connective tissue. Axons in sheath of neurolemmocytes (schwann cells) make up nerve fibers.

What are the 4 main parts of the brain, and what are the general functions of each part? What are white matter and gray matter, ad where do these occur in the cerebrum? In which part of the brain do pyramidal cells occur? What are the 4 histologically distinct layers of the cerebellum?

The four main parts of the brain are the brain stem, diencephalon, cerebrum, and cerebellum. Brain stem connects the brain to the spinal cord and connects nuclei that control breathing, heart beat, and BP, the diencephalon is the relay center (thalamus) and controls emotion, body temp, secretes hormones (hypothalamus). THe cerebrum is the largest part in humans in 2 cerebral hemispheres; folded surface. the outer cortex of gray matter (cell bodies) and the inner portion of nuclei involved in controlling body movements and white matter (myelinated axons and oligodendrocytes). cerebellum coordinates muscular movement , psotural muscle tone, and blance. the surface is highly folded . Gray matter is cell bodies of neurons and occurs in the outer cortex of the cerebrum. the white matter is myelinated axons and oligodenrocytes and is on the inner portion of the cerebrum. Pyrimidal cells occur in the cortex, conscious part o the brain which interprets sensory info and initiates voluntary motor responses. The four histologically different layers of the cerebellum are the molecular layer, purkinje cell layer, granular layer, and cerebellar medulla. the molecular layer has neuropil and scattered nuerons, the purkinje cell layer has cell bodies of large neurons with dendrites in molecular layer, the granular layer has cellbodies of small neurons, the cerebellar medulla has white matter.

What are the 4 structural types of neurons, and where is each type found in the nervous system?

The four structural types of neurons are multipolar, bipolar, unipolar, and anaxonic. Multipolar are the most common type. Bipolar are found in sensory organs, retina, olfactory mucosa, and inner ear, unipolar are found in sensory ganglia. Anaxonic regulate other neurons in CNS (don't make action potential)

What are the 4 types of glial cells found in the CNS, and what is the function of each? Which type is most numerous?

The four types of glial cells found in the CNS are microglia, astrocytes, oligodendrites, and epindymal cells. oligodendrocytes wrap axons in myelin sheath (forms white matter), and have a dark, oval nucleus, and pale cytoplasm. the neuropil is proccesses of neurons and glial cells. Microglia are macrophage, from embyronic monocyte, small, elongate, dense nuclei, Astrocyte are most numerous glial cells that wrap capillaries with feet and form glial limiting memnbrane and form scar tissue. ependymal cells have cilia or microvilli and move/absorb CSF in ventricles and central canal, tight junctions, but no basal lamina.

What structure separates the innermost meningeal layer from making direct contact with neurons?

The glial limiting membrane of astrocytes, separates the pia mater from the cerebral cortex. It acts as a barrier to substances in CSF enetering the CNS.

From which embryonic tissue does the nervous system develop, and what are the stages of this developmental process? Into what adult structures do the neural tube and the neural crest develop?

The nervous system develops from the dorsal ectoderm. The notochord induces formation of neural plate in overlying ectoderm. The neural folds and Neural groove form and the neural crst cells become mesenchymal. THe neural folds fuse, forming the neural tube, with central canal, neural crest cells sit on top of the tube. the Nueural tube forms brain and spinal cord and the neural crest cells from the PNS

What are the 3 functional types of neurons, based on the direction of the nerve impulse towards or away from the CNS?

The three functional types of neurons are sensory, interneuron and motor. sensory carries impulse towards CNS and contains cell body in ganglion (dorsal root ganglion in spinal nerve), interneuron carries impulse within the CNS or regulate other CNS neurons, and the motor ones carries impulse away from CNS.

What are the 3 layers of connective tissue found in a large nerve, and which layer forms the blood-nerve barrier?

The three layers of connective tissue in a large nerve are epineurium, perineurium, and endoneurium. The perineurium forms the blood nerve barrier, along with capillary junctions. The epineurium is dense CT; continuous with dura mater, around and within each nerve, between fasciles, contains blood vessels internally. the perineurium are two to six layers of fibrocytes surrounding fascicles (bundles) of fibers, joined by tight junctions (form blood-nerve barrier, along with capillary tight junctions), endoneurium is within fascicle a thin layer of fibroblasts, capillaries, adn reticular fibers around schwann cells.

What are the 3 meningeal layers surrounding the CNS, from outside to inside? Which layer contains cerebrospinal fluid (CSF)?

The three meningeal layers surrounding the CNS are the dura mater, the arachnoid mater, and the pia mater. The arachnoid matter contained the CSF.

What are the 3 regions of a neuron, and what are the functions of each region? Which region generates and conducts the electrical impulse?

The three regions of a neuron are the cell body which contains the nucleus, many ribosomes in the cytoplasm and many intermediate filaments that clump into visible neurofibrils. The dendrites which are numerous, short, branched covered with spines, receive signals from other neurons or receptors , generate graded potential. and the axon which is a single, long branched at the ends and arises from axon hillock. it releases NT from boutons at tips of branches. The axon generates and conducts the electrical impulse.

What are the 2 divisions of the PNS? Compare and contrast the somatic and autonomic systems (control, type of signal, number of motor neurons, and neurotransmitters), as well as the 2 sub-systems of the autonomic nervous system (function, anatomic connection to CNS, location of ganglion, neurotransmitter released by postganglionic neuron, and effects on target organs). At which synapses is acetylcholine used as a neurotransmitter?

The two division of the PNS are sensory and motor. In the motor division are somatic and autonomic nervous systems. The somatic nervous system is voluntary and reflex movements of skeletal muscles, can only stimulate, single motor neuron w/ cell body in CNS, NT is Ach. The autonomic nervous sytem is involuntary control of smooth muscle, cardiac muscle, and glands. can stimulate or inhibit target. two neuron relay system (pre/postsynaptic motor neurons) and Ach used as NT between first and second neuron. The parasympathetic controls everyday activities, exits CNS in cranial/sacral regions, ganglion in/near target, and releases Ach from post-synaptic ganglionic neuron. The sympathetic controls fight or flight exists cns in thoracic/lumbar regions, ganglion close to CNS , release NE from postganglionic neurons. Ach is used in somatic nervous system and the autonomic nervous system for parasympathetic (between the first and the second neuron)

What are the 2 types of axonal transport, and what is being transported by each type, and in which direction?

The two types of axonal transport are fast and slow. Fast is 50-400 mm/day and transports membrane-associated material liek organelles and vesicles, it can do anterograde or retrograde(toxicants,viruses) and is powered by ATPase motor proteins moving along microtubule tracks(kinesin for anterograde, dynein for retrograde). Slow is 0.2-2mm/day and transports cytoskeletal elements and is anterograde only.

What are the two type of cells found in nerve tissue?

The two types of cells found in nerve tissue are neurons and glial cells.

What are the 2 types of glial cells found in the PNS, and what is the function of each?

Two types of glial cells in PNS are Neurolemmocytes (Schwann cells) and Satellite cells. Neurolemmocytes wrap melinated axons in a myelin sheath and support small diameter unmyelinated axons in pocket. Satellite cells surround cell bodies in ganglia.

What is myelin, and how is it formed in the PNS and CNS? How does the myelin sheath appear in paraffin-embedded tissues in cross section? What is a node of Ranvier? What is the function of the myelin sheath? What types of axons are unmyelinated, and how does their appearance differ in the PNS vs. CNS when viewed with the TEM?

myelin is mostly pasma membrane with an external lamina of type IV collagen and laminin. In PNS is formed when a neurolemmocyte wraps raroudn segment of one axon. Myelin is removed by xylene during histological processing, forming an empty space around the axon. Sheaths are interrupted by gaps, nodes of ranvier. Interdigitating processes of schwann cells partly cover the gaps. The function of the myelin sheath is to greatly speed up the conduction (up to 100x) . this is damaged in MS patients by certain neurotoxicants. In the CNS unlike neurolemmocyte, an oligodendrocyte can wrap segments of several (up to 50) axons . unmyelinated fibers are for small diamter axons which have slow conduction speeds. in the cns unmyelinated axons are naked. (*expand on this?*)

Once the action potential reaches the axon terminal, how is the signal then passed on to the next cell? What are the roles of Ca++, synaptic vesicles, neurotransmitter, LGICs, and neurotransmitter removal mechanisms in this process?

the signal is passed on to the next cell through synapses = special junctions between two cells which are separated by a space (synaptic cleft) with the exception of electrical synapses. 1. action potential arrives due to VG NA+ channels. 2. voltage gated ca2+ channels open. 3. increased Ca2+ causes synaptic vessicles to release NT, which binds to LGIC on post-synaptic cell. 4. binding triggers change in voltage in postsynaptic cell (EPSP if Na+ channel , IPSP if K+ channel). 5. NT taken back up by axon (serotonin) or broken down (ex. Ach by acetylcholinesterase). synapse can be with cell body, dendrite, or axon terminal of another neuron. some NTs synthesized in cell body , others in axon terminal, some NT bind to GPCRs that are not ion channels, initiating intracellular signaling pathways (ex. serotonin, dopamine) via G proteins