Cell Function- Nervous Tissue 2

kms013's version from 2015-09-29 00:47

Section 1

Question Answer
synapsesites where nerve impulses are transmitted from one neuron to another or from neurons and other effector cells; junction of 2 neurons "cell communication"
presynaptictypically myleinated in ANS
vesiclefilled with NT created in soma of cell and delievered to axon; Presynapitc axon terminal fromwhich NT is released by exocytosis from vesicle
Voltage gatesstimulated by AP sent from soma has to reach threshold first;
synaptic cleftwhere axon terminal buttons communicate to post-synaptic membrane on dendrite
Post synapticfound on dendrite of non-neural cell; have receptors for transmitter and ion channels or another mechanism to initiate impulse; once a NT is released it is quickly enzymatically broken down diffused backinto pre-synaptic cell and or recycled (pumps)
describe what happens as AP comes through and down axonimpulse AP comes, changes voltage on membrane and opens voltage gated Ca, enables Ca to come in, this stimulates exocytosis of vesicles, vesicles go to membrane the exocytosis of NT goes across synaptic cleft, NT binds to receptor this causes local potential; this increases chances for AP by deplarizing the membrane more (EPSP)
IPSPNT open chloride or other anion cuasing influx of anions and hyperpolarization of post synaptic cell, making more resisitve to depolarization; brings us further away from firing AP; hyperpolarization; typically due to excess Ca; decremental---if not enough signal, will run out
EPSPcauses Na channels to open, increases depolarization; small added steps that slowly bring us toward AP/depol.
Calciumanion as NT cuases IPSP in the post synaptic membrane; catecholamines- epi, norepi, and dopa, and GABA; AA- glutamate, glycine, serotonin, sm. peptides,- endorphins
Neuroglia cells90% cells; astrocytes, satellite cells, ependymal cells, microglia; also called glial cells; support neural and survival activites; 10xs more abundant in mammillian brain; surrounds neuron bodies, axons, dendrites, and occupy space b/w neurons
AstrocytesRegulate extracellylar ionic conc. around neurons (buffering K) Extends processes with perivascular feet that cover capillary and contribute to BBB; communicate via gap junction with one another; attach cells to capillaries, most common site for tumors in adults- typically in white matter; protoplasmic- many short branches, predominate in grey mater
Blood brain barriersurrounds and blocks brain, preventing stuff from blood to get in head; feeds neuronal cells in brain; allows sugar, O2, Co2, alcohol, virus, anesthetics, drugs...does NOT allow antibiotics, dopamine, proteins
Satellite Celllike schwann cell; they are derived from embryonic neural crest; form intimate covery around large neuronal cell bodies in ganglia of PNS; exert a trophic and supportive effect on these neurons, insulating nourishing, and regulating their microenvironment
dependymal cellscolumnar / cuboidal cells that line the ventricles of the brain, central canal of the SC, the apical ends have cilia that move CSF; long microvilli are involved with absorption; there is no basal lamina and they are joined apically via junctional complexes instead of basil lamina they have projections that extend into adjacent neurophil
CSFproduced by ependymal cells; also moved and monitored in contents by ependymal cells
microglialess than oligodendrocytes or astrocytes, they are small cells wiht short irregular processes evenly distributed throughout grey and white matter; unlike other glial cells, these migrate through the neurophil, scanning tissue for damage d cells and invading microorganisms; they secrete immunoregulatiory cytoteines and constitute defense in CNS; do not originate from neural progenitor cells, but from blood circulating monocytes; like macrophage, presents antigen for defense mechanism
cells of myelinationoligodendrocytes and schwann cells
oligodendrocytesmyelin porducing cell inside brain and SC and are massive cells that send out processes to neuron cells then starts wrapping itself around the nerve; CNS located; 80% lipids, insulates nerves; each produce myelination to several neurons (up to 50 diff); community based and the predominant glial cell in CNS- white matter; mylenated cells vary in size and function (motor); the bigger the better/faster conduction speed
schwann cellmyelination in PNS and differentiate from precursor in neural crest; 1 neuron/innernode cover lenght of axon; have trophic interactions;
Neural conduction (2 ways)saltatory conduction, continuous conduction
saltatory conductionmylinated nerve fibers- in PNS, schwann cells wrap around nerve axon and give shape to internode and nodes of ranvier; this arrangment gives appearance of AP jumping from node to node; there is a high density of Na/K pumps at each node; higher than the amt located under each schwann cell (internode) when Achl is dumped onto mem; this causes influx of Na to go inside cell; the Na increases causing MP to change; If there is enough voltage change, this causes Na/K pumps to be activated; Na is squesszed down axon; results in activation of many Na/K pumps at each node; this gives appearance of jumping
continuous conductionneuronal transport in unmylinated nerve fibers; speed of cunduction is sloow but steady; all same characteristics of myelinated (but Na/K pumps are evenly distributed) wave of depolarization causes Ap- to cell and across axon
2 ways to increase signalspatial summation; temporal summation
types of synapsesaxosomatic (b/w axon and another cell body) axodendritic (b/w axon and dendrite) axoaxonic (b/w 2 axons; these modulate activities for the other 2 types)
neural plasticityinvolving formation and remodeling of synaptic connections; neural adaptations, increase dendrite branches, increase synapses; reallocation of brain regions (rewiring); use it or lose it, use it and improve it; repitition -- building more synapses
neural regnerationmore simply organized; peripheral; nerves have better capacity to do; a process involving reactivation of cell body; schwann cells, macrophage cells; PNS located, can regenerate; Nissl substance; proximal swelling sprouts; distal retraction; wallerian degeneration; endoneural (tunnel endoneurium and schwann cells) b/w 2-3 mm./day growth; NOGO-- bichemical markers that prevent neuronal activity rom going through astrocyte scars so CNS is totally blocked

Section 2

Question Answer
sarcoplasmthe cytoplasm of a muscle cell (storage of glycogen and myoglobin)
sarcoplasm reticulum (SR)smooth ER variation network around each fiber that is storage location for Ca ions
sarcolemmamuscle cell membrane
intercalated discsbind cardiac cells together
smooth musclelack striation; have slow, involuntary contractions; fusiform shape
skeletal musclebundles of long, multinucleated cells with cross-striations; contraction quick, forefull, and usually under voluntary control
cardiac musclecross-striations; intercalated discs; involuntary, vigorous, rhythmic
myoblastprogenitor cell from mesoderm, turn into muscel cell; skeletal muscles begin to differentiate when mesenchymal cells, called myoblasts, align and fuse together to make longer, multinucleated tubes called myotubes
myotubesformed by many myofibrils linking together, the more there are, the longer the fiber; forms muscle fiber; longer multinucleated tubes that come from myoblasts; synthesize the proteins to make up myofilaments and gradually begin to show cross-striations by ligh microscopy
All muscle contraction is caused by __________-the sliding interaction of the thick myosin filaments along thin actin filaments
multinucleatedas muscle cells mature, their nucleus is pushed to outside of cell; cardiac muscle is different
Muscle satellite cell (MSC)myogenic precursor cell; beneath basal amina but ouside muscle cell; inactive except for after muscle injury; proliferate and create new myotube; 3-4 days afer injury; made from myoblast
hypertrophy- increase of cell volume (high, nourishment)
hyperplasiahigh, molding; growth by increase of number of cells, takes place readily in smooth muscle (not lost ability to divide)
myogenesismyoblast---myoblasts fuse to form myotubes---differentiation---muscle fiber = muscle cell
fasciaprotective mechanism
Epimysiumsurrounds entire muscle; muscle is then further divided into fascicals
perimysiumsurrounds fascicle
endomysiumsurrounds individual muscle fiber; when individual muscle contracts and influence and pulls on endomysium
fasciclea bunch of muscle fibers surrounded by perimysium
fiberone cell of muscle; does not go the entire lenght
myofibrilmake up subunits of fiber; striated part; has sarcolemma; various amounts of mitochondria
myofilaments contain what?Myosin, actin, titin, nebulin, dystrophin, myomesin
myosinthick and heavy chain with a head that has 2 binding sites (1 touches actin, 1 is for ATP) and a tail that makes up heavy chain
actinseries of G actin0 has binding site for myosin head; F actin is combo of G-actin; has tropomyosin and troponin
tropomyosincovers binding site on G-actin
troponinlocated on tropomyosin and is a receptor
titinsupports myosin chain and attaches to Z line; has some spring and is major player in elasticity
Nebulinhelps keep actin aligned properly ; keeps actin G-actin subunits in helix and togheter
Dystrophinbinds sarcolemma to the outter microfilaments; macroprotein that keeps endomysium to fiber; in musculodystrophy, a genetic mutation that leads to defective linkages 1. Deshends- its X linked recessive (little boys) 8,9,10, 11 = non ambulatory....2. Bakers- 40 + years, but still non-amb.
Myomesinfound in M-band along with creatine kinase- transfer P from phosphocreatine to ADP thus helping supply ATP for relaxation;
Z discheavy CT; sarcomere in b/w Z disc is the functional unit of muslce; has apperance of Z line
I bandfrom Z line to tip of myosin, white area, and on either side of Z line; just titin and actin continaing area
A banddark area and light area lenght of myosin chain; darkest is where myosin and actin are overlapping; lighter area is H zone;
H zonelight area in mid A band where myosin is ONLY located
M linevery center and made of prteins called myomyesium and creatine kinase; I holds myosin in place others helps supply ATP for relaxation
Sarcoplasmic reticulumsystem of tubes found on periphery on all myofibiles; it is specialized for sequestiration of Ca2; depolarization of SERcan cause release of Ca2 initated by moor merve synapse and cause universal contration of all myofibriles
TriadTransverse (T) tubules and terminal cisterns
T tubuleslong finger like invaginations of the cell mem. penetrate deeply into the sarcomere; these divits resemble the routes on surface of death star
terminal cisternsenlargements of SR; found b/w junction b/w A and I band that lead prom T-tubles; after signal is transmitted to cisternae, which is concentrated with Ca, Ca is released via Caq channels into mem of surrounding myofilament; Ca binds to troponin and allows for A-M binding
Neuromuscular Junction (NMJ) motor-end platesynaptic vesicles, schwann cells, synaptic cleft, junctional folds
Synaptic vesiclesthese are found within th epresynaptic nerve and carry Ach; these vesicles are forced to membrane by influx of Ca and bind to memb ia SNAP/SNARE
Schwann cellcovers over top of motor endplate; an axon of single motor neuron can form MEP with one or man mucle fibers; innervation by a single motor neuron to a single muscle fiber provides prescise control of muscle activity and occurs in extraoccular muscles; large muscles, motor neurons branches to form MEPs with 100 muscle fibers; a single axon and all of its muscle fibers = motor unit
Synaptic cleft area that only ACh is dumped and b/w pre and post synaptic mem
Junctional foldsdips down into muscle itself that contain abundant receptors and increase surface area on post synaptic mem.; gives rise to more Ach transmembrane receptors
Excitation-contraction coupling1. AP reaches end of axon, Ca fluids in and directs vesicles to move toward synapse; 2. snape and snare, mem fuse, dump Ach; 3. Ach binds to receptor; 4. causes influx of Na = increase in voltage (difference mem pot in the NMJ) i s-90 not -70; 5. causes potential changes on mem of entire muscle fibers. this runs into down t tuble and then causes muscle to contract; this voltage change open Ca gates of Ca then binds to troponin; increase in tropomyosin then reflects the binding cite of actin; myosin is then attached to actin and binds = contraction; if myosin head is ATP phosphorylated, then it is let go of actin and is in flexed/relaxed state
contractioncross bridges; power stroke; recovery stroke; during contraction, neighter myofilaments change lenght; Ca binds troponin -= moving trpomyosin and reflecting myosin sites and allowing cross bridges to form
cross bridgeare the interactions of myosin binding to actin; this bind causes pivot in myosin heads (erect) which pulls actin farther into A band toward Z disc
power strokemyosin (attached to actin) and slides forward which pushes actin more into A band toward Z disc
recovery strokewhen ATp binds to the myosin and causes myosin to release from actin and lay back down waiting to start cycle over agian
Relaxationstop stimulating alpha motor neurons; as long as this is happening, the muscle is still contracting and Ca in muscle; when Ach stops, Ca stops or pumped back in cisternae
achesterasebreaks down Ach
in absense of ATP, like in rigormortis, ______________________the actin and myosin become stable and eventually the myosin heads decomposebreak off resulting in relaxation
striated muscle and mmyotendinous junctions contain sensory receptors acting as proprioceptors whcih provides the CNS with data from the MS system
muscle spindleor stretch receptors; encapsulated by modified perimysium with concentric layers of flattened cells, containing interstitial fluid and thin fibers with nuclu introfusal fibers
proprioreception to CNSyour ability to kjnow where you are in time and space; we get this through muscle spindles
Intrafusal fiberssends signals for proprioception to cerebellum; several sensory nerve axons penetrate each muscle spindle and wrap around IF fiber; different types of sensory and intrafusal fibers mediate reflexes of varying complexity to help maintian posture and regulate opposing muscle groups such as during walking
Nuclear chainfibers that are more spread out
nuclear bagcentralized and lots of fibers together; position that is static
primary afferent (1a)typically sense rate and change
secondary afferent (II) typically sense static; Ex. now we are in a different position