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102 Cards in this Set
- Front
- Back
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Sodium-potassiump pump
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pumps 3 Na out, 2 K in. moving + outside cell, therefore more - inside. leads to charge imbalance inside membrane. needs ATP
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Potassium channel vs Sodium channels
(K flows out along chemical gradient vs NA flows in along electrochemical gradient) |
effect of K movement alone. very leaky. -mV. (vs)
effect of Na mnovement alone. not as leaky. +mV |
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Polarization
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charge difference across memrane
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Depolarization
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decreases magnitude of difference. any change from the resting potential towards 0 mV. influx of Na. results from opening voltage gated Na channels.
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Hyperpolarization
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increases magnitude of difference. loss of + ions therefore increase in - of resting potential.
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Repolarization
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approach back to resting membrane potential. process of restoring normal resting potential after depolarization. loss of K. results from opening of voltage-gated K channels
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Types of Ion channels for Action Potentials
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1. leak channels (always open) 2. mechanical channels (open due to mechanical deformation of membrane) 3. voltage-gated channels (rely on change in membrane potential) 4. chemical-messenger gated channels / ligand-gated channels (has reception and signaling molecule)
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Graded Potential
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1. Depolarizing/Hyperpolarizing 2. no threshold 3. amt of depolarization/hyperpolarization depends on stimulus intensity 4. passive spread from stimulus site 5. effect decreases w/ distance 6. no refractory period 7. occur in most cell membranes
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Action Potential
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1. Depolarizing 2. Depolarization to threshold before action potential 3. all-or-none phenomenon 4. action potential at a site deporalizes adjacent site to threshold 5. propagated along w/o decrease in strength 6. refractory period 7. occur only in excitable membranes of specialized cells
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CNS vs PNS
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CNS = brain & spine. processes sensory data & motor commands. PNS = all neural tissue outside CNS. afferent division (brings sensory info from receptors to organs) and efferent division (carries motor commands from CNS to muscles)
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Somatic nervous system (SNS) vs autonomic nervous system (ANS) - efferent division of PNS
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SNS controls skeletal muscle contractions. voluntary. under conscious control. (vs) ANS/visceral motor system. provides automatic regulation of smooth, cardiac muscle & glandular secretions. subconscious level.
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Neuromuscular junction
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synapse btwn neuron & muscle cell
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Neuroglandular junction
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neuron controls/regulates activity of a secretory (gland) cell.
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Axoplasmic transport
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movement of materials btwn cell body & synaptic knob. cell body -> knob =anterograde flow. (reverse is retorgrade flow)
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Structural Classification of Neurons
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1. anaxonic (small, all processes equal. in brain and special sense organs) 2. bipolar (2 distinct processes. in special sense organs) 3. unipolar (pseudounipolar. dendrite & axon continous w/ cell body to one side. in PNS) 4. multipolar (>2 dendrites, 1 axon. in CNS)
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Functional classification of neurons
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1. sensory (afferent neurons. deliver info to CNS. located in peripheral sensory ganglia. unipolar w/ afferent fibers that extend btwn sensory receptor & CNS) 2. motor (efferent neurons. carry instructions from CNS to peripheral effectors in organ. axon travelling away from CNS) 3. interneurons (association neurons. most abundant. responsible for both distribution of sensory info and coordination of motor activity. for higher functions)
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Types of receptors - Sensory neurons
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1. interoceptor (monitor digestive, respiratory, cardio, urinary, reproductive system. sensation for taste, deep pressure & pain) 2. exteroceptors (provides infor about external environment thru senses) 3. proprioceptors (monitors position & movement of skeletal muscles)
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Neuroglia in CNS - ependymal cells
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ependyma = line central canal & form epithelium. slender processes that branch and make direct contact w/ neuroglia in surrounding neural tissue
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Neuroglia in CNS - astrocytes
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largest & most abundant. maintains bld barrier & isolates CNS from general circulation. encases capillaries & control permeability. repairs damaged tissue. guide neural development. control interstitial environment.
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Neuroglia in CNS - oligodendrocytes
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smaller. processes in contact w/ neural body. cooperate in formation of myelin sheath. ties clusters of axons together. white matter (because of lipids)
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Neuroglia in CNS - microglia
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least & smallest. capable of migrating thru neural tissue, engulf cell debris, waste products & pathogens.
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Neuroglia in PNS - satellite cells
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aka amphicytes. surround neuron cell bodies & regulate environment ~ astrocytes.
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Neuroglia in PNS -schwann cells
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aka neurilemmal cells. form sheath around peripheral axons, therefore shielded from contact w/ interstitial fluid. can myelinate only 1 segment of single axon.
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Wallerian degeneration - in PNS (repair of damaged nerves)
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1. fragmentation of axon & myelin 2. schwann cells form cord, grow into cut, unite pieces . macrophage engulfs debris 3. axon sends buds into network of schwann cells & grows along cord 4. axon continues to grow & is enfolded by schwann cells.
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Transmembrane potential
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1. intracellular fluid (cytosol) & extracellular fluid differ in ionic composition. cytosol has more K & - charged proteins. ECF has more Na & Cl 2. cells have selectively permeable membranes, ions go through channels 3. inner surface has an excess of - charges
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Passive Forces
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1. chemical gradients (K higher inside, tend to move out of cell thru K channels. driven by conc gradient) 2. electrical gradient (cell membrane more permeable to K than Na, K leaves cytoplasm faster, therefore cytosol exhibits net loss of + charge. + and - charge btwn cell membrane restricts ion movement = potential difference) 3. electrochemical gradient (sum of chemical & electrical forces acting on that ion across the cell membrane)
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Current
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movement of charges to eliminate potential difference
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Resistance
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measure of how much the membrane restricts ion movement. greater resistance, smaller current.
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All or none principle - Action potential
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properties of action potential independent of relative strength of depolarizing stimulus, as long as stimulus exceeds threshold, action potential is generated.
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Generation of an Action potential
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1. deporalization to threshold 2. activation of Na channels and rapid depolarization 3. inactivation of Na channels & activation of K channels 4. return to normal permability.
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Refractory period - Action potential
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time action potential begins to stabilization of normal resting potential when membrane doesn't respond to additional stimuli. absolute refractory period = all voltage gated Na channels already open or inactivated. relative refractory period = when Na channels regain normal resting condition & continues until transmembrane potential stabilizes at resting levels.
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Continuous propagation - Action potential
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action potential spreads across entire excitable membrane surface in a series of small steps. affects adjacent membranes and cycles repeated
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Saltatory propagation - Action potential
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action potential leaps from node to node. carries nerve impulses more rapidly & uses less energy because less surface area is used and fewer Na ions must be pumped out
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Axon types
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1. Type A fiber (largest. myelinated. 140 m/s or 300 mph) 2. Type B fiber (smaller. myelinated. 18 m/s or 40 mph) 3. Type C fiber (unmyelinated. 1 m/s or 2 mph)
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Nerve impulses
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electrical events that allow msgs to move from one location to another thru action potentials along axons.
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Electrical synapse
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direct physical contact btwn cells. membranes joined by gap junctions. pores allow passage of ions. propagates action potential quickly. rare. always propagates an action potential.
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Chemical synapse
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involves NT. action potential may/may not release enough NT to bring postsynaptic neuron to threshold. abundant.
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Excitatory neurotransmitter - Chemical synapse
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cause deporalization & promotes generation of action potentials
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Inhibitory neurotansmitter - Chemical synapse
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cause hyperpolarization & supress generation of action potentials
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Cholinergic synapse
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releases acetylcholine (ACh). released at neuromuscular junction involving skeletal muscle fibers.
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Norepinephrine
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in brain & ANS. aka noradrenaline. excitatory, deporalizing effect
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Dopamine
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in CNS. inhibitory/excitatory effect. inhibitory = precise control of movement. excitatory = high
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Serotonin
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in CNS. affects attention & emotional states.
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Gamma aminobutyric acid (GABA)
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inhibitory effect. reduces anxiety.
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Neuromodulators
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compounds that alter rate of NT released by presynaptic neuron or changes the postsynpatic cell's response to NT.
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Opiods
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neuromodulators that relieve pain. inhibit release of neurotransmitter substance P at synapse that relay pain sensations
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Postsynaptic potentials
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graded potentials that develop in postsynaptic membrane in response to neurotransmitters. 2 types: 1. EPSP graded depolarization caused by arrival of NT at postsynaptic membrane 2. IPSP graded hyperpolarization of postsynaptic membrane
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Temporal summation vs. Spatial summation
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Temporal = addition of stimuli in rapid succession at a single synapse that is active repeatedly. Spatial = simultaneous stimuli applied at different locations that have cumulative effect on transmembrane potential. multiple synapses that are active simultaneously.
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Properties of muscle tissues
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Excitability (responds to NT), Contractility (shortens & generates force), Extensibility (stretchable), Elasticity (returns to original shape)
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Functions of muscle tissues
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produce body movements, stabilizes body positions, regulates organ volumes, movement of substance within body, produce heat contractions of skeletal muscle.
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Skeletal muscle - Connective tissue
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Superficial fascia = loose CT & fat under skin.
Deep fascia = dense irregular CT around muscle. Epimysium = CT surrounds whole muscle. seperates muscle from tissue/organs. Perimysium = CT surrounds bundles of muscle fibers. seperates muscles into compartments. Endomysium = CT sperated individual muscle cells |
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3 types of muscle
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1. skeletal (move body by pulling bones, attaches to bone, skin or fascia, striated w/ light & dark banks visible, voluntary control) 2. cardiac (pushes bld thru. striated. controlled by ANS. intrinsic pacemaker) 3. smooth (pushes fluids & solids thru digestive tract, regulates diameter of small arteries. nonstraited. involuntary)
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Sarcolemma- skeletal muscles
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cell membrane of muscle fiber, surrounds sarcoplasm
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Tranverse tubules - skeletal muscles
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signal conducted thru narrow tubes continuous w/ sarcolemma extend into sarcoplasm at right angles to cell surface. invaginations of the sarcolemma into center of the cell, filled w/ extracellular fluid & carry muscle action potentials.
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Myofibrils - skeletal muscles
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consist of bundles of protein filaments called myofilaments. responsible for contractions because can shorten. T Tubules encircles myrofibrils.
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Sarcoplasmic Reticulum - skeletal muscles
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membrane that forms tubular network around ea individual myofibril. system of tubular sacs similar to smooth ER in nonmuscle cells.
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Sarcomere - skeletal muscles
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repeating functional units w/in myofibrils. area between 2 Z lines/discs. consists of thick & thin filaments, proteins for stabilization and regulation.
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A band vs I band
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length of thick filament. dark. (vs.) length extends from one sarcomere to the next. light.
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M line
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protein for connecting thick filaments. anchors thick filaments.
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H zone
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light region on either side of m line. only in thick filaments.
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Z line
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marks boundary btwn adjacent sarcomeres.
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Thin filaments
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made of actin. consists of 4 proteins: 1. F actin (twisted strand of 2 rows of globular molecules of G actin) 2. Nebulin (long strand that extends along F actin cleft & hold it together) 3. tropomyopsin (strands that cover active sites on G actin & prevents it from binding to myosin) 4. troponin (made of 3 globular subunits that bind to tropomyosin , G actin and calcium)
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Thick filaments
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made of myosin. tail bound to other myosin molecules in thick filament. head projects outward toward think filaments w/ 2 globular protein subunits = cross-bridges.
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Contraction
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1. myosin head binds to actin to form cross bridges 2. myosin heads rotate toward center of sarcome (power stroke) 3. myosin head binds ATP, cross bridges detach from actin 4. myosin head hydrolizes ATP to get reoriented and energized. H zone and I band get smaller, zones of overalp get larger, Z lines move closer, wid of A band remains constant.
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Neuromuscular Junction (NMJ)
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specialized intercellular connection for communication btwn nervous system and skeletal muscle fiber. neuron stimulates fiber by 1. arrival of AP at synpatic terminal, change in transmembrane potential 2. permeability changes in membrane trigger release of ACh 3. ACh bind to receptor, changes permeability, Na rushes into cell 4. results in AP in sarcolemma 5. ACh broken down by AChE.
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Excitation-contraction coupling
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occurs as passage of AP along a T tubule triggers release of Ca from sisternae of SR at triads. Relaxation = troponin holds tropomyosin in position to block myosin-binding sites on actin. Contraction = Ca binds to troponin, changes shape, uncovers myosin binding sites on actin (tropomyosin)
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Rigor mortis
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muscles stay contracted because Ca leaks out of SR and allows myosin heads to bind to actin. BUT ATP synthesis ended, therefore crossbridges can't detach from actin until proteolytic enzymes digest decomposing cells.
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Tension production
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skeletal muscles contract most forcefully when stimulated over a narrow range of resting lengths. amt of tension = # of crossbridges formed.
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Twitch
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single stimulus contraction-relaxation sequence.
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Latent phase vs. Contraction phase vs. Relaxation phase
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begins at stimulation and is time needed for conduction of an action potential and release of Ca (vs) tension rises to a peak (vs) Ca levels downs, active sites covered, active cross-bridges lessen, tension falls.
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Treppe
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repeated stimulation at a slow rate.
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Wave summation
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stimulus before relaxation phase, 2nd more powerful contraction occurs.
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Incomplete tetanus
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convulsive tension. stimulation continues. not allowed to relax, tension rises until peak value
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Complete tetanus
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higher stimulation frequency elimantes relaxtion phase. tension plateaus at max levels. continuous contraction
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Isotonic contractions
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tension rises & skeletal muscles length changes 1. concentric (muscle tension exceeds resistance, therefore muscle shortens. load is moved) 2. eccentric (peak tension developed is less than load, muscle elongates due to gravity)
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Isometric contraction
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tension rises but muscle length does not change. tension never exceeds resistance. no movement occurs
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Muscle tone
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resting tension (motor units are active) in a skeletal muscle = firm. involuntary contraction. doesn't produce movement. essential for posture and maintaining bld pressure.
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ATP formation
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generated by 1. aerobic metabolism in mitochondria (95% of demands. Krebb's cycle. produces 34 ATP) 2. glycolysis (breakdown of glucose to pyruvic acid in cytoplasm. anaerobic process. produces 2 ATP)
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Cori cycle
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shuffling of lactic acid to liver & glucose back to muscle cells
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Muscle fatigue
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at peak levels of activity, ATP demands can't be met (oxygen cant diffuse thru muscle fast enough) therefore glycolysis produces ATP, pyruvic acid is produced which is converted to lactic acid. inability to contract. depletion of creatinine phosphate, decline of Ca in sarcoplasm.
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Recovery period
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when oxygen is abundant, lactic acid can be recycled by conversion back to pyruvic acid, body's oxygen demand is elevated
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Oxygen debt
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amount of oxygen required to restore normal, preexertion conditions.
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3 major types of skeletal muscle fibers
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1. fast fibers (most of skeletal muscle fibers in body. can contract at 0.01 sec or less after stimulation. large diameter, densely packed myofibrils, large glycogen reserves, few mitochondria. fatigue rapidly) 2. slow fibers (smaller diameter. 3x longer to reach peak tension after stimulation. can contract for extended periods, surrounded by capillaries, more oxygen supply. contain myoglobin) 3. intermediate fibers (like fast fiber in appearance, has little myoglobin. more capillaries and more resistant to fatigue than fast)
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White muscle vs Red muscles
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dominated by white fibers, not used as often. (vs) dominated by slow fibers. used often
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Atrophy vs Hypertrophy
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wasting away of muscles, caused by disuse or severing of nerve supple, diet. (vs) enlargement of stimulated muscle due to repeated, exhaustive stimulation. increase in diameter of muscle fibers
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Anaerobic endurance vs aerobic endurance
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length of time muscular contraction can continue to be supported by glycolysis & reserves of ATP & CP. (vs) length of time muscle can continue to contract while supported by mitochondria.
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Cardiac muscle tissue
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relatively small, single-centrally placed nucleus. T tubules short & broad. no triads. SR lacks terminal cisternae. dependent on aerobic metabolism to obtain energy
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4 major functions of cardiac muscle
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1. contracts w/out neural stimulation (automaticity) 2. innervation by nervous system can alter pace & amt of tension 3. contractions last 10x than skeletal 4. cell membrane properties differ, cant produce tetanic contractions
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Smooth muscle tissue
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form sheets, bundles, sheaths around other tissues. long & slender, spindel shaped. single centrally located nucleus. no T tubules. SR forms lose network in cytoplasm. lack myofibrils & sarcomeres. nonstriated. thick and thin filaments arranged diagonally, therefore contract in corkscrew. 2 layers: longitudinal & circular.
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Multiunit smooth cell
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each cell acts relatively independently of other smooth muscle cells in organ
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Visceral smooth cells
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not always inervated by motor neurons. not under voluntary control.
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Innervations - smooth muscle tissue
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no NMJ, innervating nerves have bulbous swellings called varicosities, which release NT into synaptic clefts called diffuse junctions
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Contraction - smooth muscle tissue
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visceral contraction (longitudinal layer contracts, organ dilates and contracts. circular laywer contracts, organ elongates) peristalsis (mix & squeeze substances thru lumen of hallow organs. slow, synchronized contraction. action potential transmitted from cell to cell)
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Role of Ca - smooth muscle tissue
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binds to calmodulin and activates it. this activates kinase enzyme. kinase transfers phosphate from ATP to myosin cross bridges. phospholyrated cross bridges interact w/ actin to produce shortening. muscle relaxes when Ca levels drop.
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Stress-relaxation response
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response to stretch only briefly, then adapts to its new length, which retains it ability to contract. allows for temporary storage of content
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Hyperplasia
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by mitosis. smooth muscles can divide and increase.
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Types of smooth muscle
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1. single unit (stomach, vessels, uterus. contract rhytmically as a unit. electrically coupled via gap junctions. exhibit spontaneous action potentials. arranged in opposing sheets & exhibit stress-relaxation response) 2. multiunit (~skeletal. loacted in airways, arteries, arrector pili muscles, internal eye muscles. rare gap junctions, infrequent spontaneous depolarization, structurally independent muscle fibers, rich never suppply. graded contractions in response to neural stimuli)
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Neuron structure
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cell body (perikaryon), dendrites (input structure), axon (generated action potential. transmit it to terminal)
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End plate potenial - EPP
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Depolarization of the postsynaptic membrane at the neuromuscular junction, mediated by acetylcholine, in response to action potentials arriving at the endings of presynaptic motor neurons.
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Slow oxidative fibers
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slow-twitch. red. lots of mitochondria, myoglobin and bld vesels. prolonged, sustained contractions for posture
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Fast oxidative-glycolytic
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fast-twitch A. red (lots of mitochondria, myoglobin and bld vessels. split ATP at very fast rate, for walking and sprinting
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Fast glycolytic
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fast-twitch B. white, few mitchondria and blood vessels, low myoglobin. anaerobic movements for short duration, like weight-lifting
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