Physiology Test 2
Terms
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- striated
- skeletal and cardiac
- non-striated
- smooth
- multinucleate
- skeletal
- single or binucleate
- cardiac
- single nucleate
- smooth
- voluntary
- skeletal
- involuntary
- cardiac and smooth
- spontaneous activity
- cardiac
- some spontaneous and some not
- smooth
- sarcoplasmic reticulum (SR)
- axial system of tubules and vesicles surrounding the myofibrils and organized in regular repeating pattern
- sarcomere
- smallest organized unit of contractile mechanism
- Z-lines
- thin dark bands that define ends of sarcomere
- I Band
- light area on either side of Z line
- A Band
- midway between any two Z lines; dark area
- M line
- dark stripe through middle center of A band
- H zones
- lighter areas on both sides of the M line
- Arteries
- carry blood from heart to tissues
- Veins
- carry blood from tissues to heart
- pulmonary circulation
- serves lungs
- systemic circulation
- serves all other organs
- lymphatic system
- transports fluid, proteins, WBCs, and micelles from tissues to vascular system
- aorta and large arteries
- conduits with elastic walls; assit in maintaining high pressures
- Resistance is due to?
- friction between flowing blood and vessel walls and bw molecules and blood cells
- Arteries inflow during Systole
- Sysole=contraction=ejection of blood from ventricle; arteries inflow is greater than outflow
- Arteries outflow during diastole
- Diastole=Relaxation=blood filling ventricle; Arteries outflow is greater than inflow
- Smaller arteries and arterioles
- conduits with add'l function of regulation which organs and tissues will receive more or less flow; more smooth muscle
- Capillaries
- resposible for exchange of nutrients; oxygen, and waste bw blood and tissues; no muscle, only basement membrane and endothelial cells
- Venules, small veins, and large veins
- thinner, less muscular walls; more compliant; return blood from capillaries and operate in maintaining optimal distribution of blood V bw venous and arterial systems
- 3 Types of vessels in vascular system
- 1. aorta and arteries:distribution 2. microcirculation: diffusion and filtration 3. Vains: collection
- Order of hydrostatic pressure
- aorta>arteries>arterioles>capillaries>veins
- Volume capacity of systemic arterial distributing system (High P)
- most limited, least variable, and least dilatable
- Low pressure system
- greatest cpacity and most dilatable; serves as resorvoir function
- Lymphatic system constituents
- lymph, lymphoid tissue, and lymphoid organs
- Lympoid organs are
- spleen, thymus, bone marrow, and nodes
- 3 Functions of Lymphatic System
- 1. returning filtered plasma protein and excess interstitial fluid to blood 2. transporting lipids into interstitial lymphatic vessels to blood 3. helping defend the body against pathogens
- Lymphatic Capillaries
- tiny, closed-end channels with porous walls made of endothelial cells; allow proteins and fluids to enter the lumen wehn P is higher in interstitial space than capillary
- collecting vessels
- connective tissue and scattered smooth muscle cells and endothelium
- right lymphatic duct
- right half of head and neck, right half of upper thorax and right upper extermities into right subclavian vein
- thoracic duct
- drains rest of body into left subclavian vein
- Resistance=
- Length/Cross-Sectional Area
- Factors determining changes in resistance
- length of conduits, cross-sectional area, and series or parallel
- SBP
- peak arterial pressure; sysolic pressure
- normal SBP
- 120 mm Hg
- DBP
- minimum arterial pressure; diastolic pressure
- normal DBP
- 80 mm Hg
- pulse pressure
- difference between SBP and DBP
- Magnitude of pulse pressure is determined by?
- stroke volume and distensibility of arteries
- MAP
- mean arterial pressure=1/3 pulse pressure+DBP
- Flow
- mean arterial pressure/resistance
- Resistance
- inversely proportional to radius raised to 4th power
- total peripheral resistance
- TPR; F=MAP/TPR
- Plasma skimming
- when a vessel gives off a smaller branch andthe flowing blood is of low hemocrit
- turbulent flow depends on?
- velocity, tube diameter, and fluid density and viscosity
- For water, when does turbulence occur?
- when Nr exceeds 2000
- What values of Nr can be reached in aorta and pulmonary artery?
- 3600-5800 and higher
- Murmurs during systole are due to?
- turbulence when rate of flow is high in exercise or when viscosity is low in anemia
- stenoses
- Anatomical constrictions that follow turbulence
- aneurysms
- dilations that follow turbulence
- Poiseuille's equation
- Resistance= 8Lpi/pi r cubed
- neurogenic control
- nerve-dependent contractile activity
- myogenic control
- nerve-independent contractile activity
- myogenic contractile activity
- spontaneous depolarization, pH, pO2, pCO2, and mechanical stimuli (stretch)
- What substances are found released around arteries, precapillaries, and capillaries?
- NE, ACh, CO2, lactic acid, and nuclear metabolism products
- Local metabolic effects are stronger in?
- metarterioles and precapillary sphincters
- What primarily affects the arterioles
- constrictor nerve fibers
- What protects a tissue against ischemia?
- locally induced vasodilation when arterial pressure is decreased or when constiction of arterioles reduces blood flow
- Autoregulation of local blood flow is affected by?
- myogenic response to stretch, vasomotor effects of local metabolites, and tissue pressure
- Autoregulation (Bayless Mechanism)
- Myogenic Response to stretch:constriction when P increases and dilation when pressure decreases
- 2 objections to Myogenic Response to Stretch
- Bayless Mechanism: 1. Increased vasoconstrictor response to increased wall tension is positive feedback->cardiovascular instability; increased BP will elevate flow resistance further raising BP leading to add'l vasoconstriction 2. smooth muscle contractile response to vascular distension abolishes stretch stimulus
- Autoregulation (Effects of Local Metabolies)
- instability (caused by + feedback) can be limited by "metabolic vasodilators" and by max range of vasomotor response;due to structural complexity, unlikely that myogenic response to stretch would operate within rigid diameter limits
- What functions together to produce autoregulation?
- local metabolic factors and myogenic mechanism
- Autoregulation (Tissue Pressure Effects)
- increase in perfusion pressure leads to increase in tissue pressure by increasing capillary hydrostatic pressure and enhancing fluid movement into EC; this is followed by compression of capillaries, venules, and small veins and increases resistance in blood flow
- Net movement out of capillary because?
- Hydrostatic pressure is greater than osmotic pressure
- Dynamic center
- HP=OP
- Net movement into capillary because?
- osmotic pressure is greater than hydrostatic pressure
- edema
- increased movement of fluid out of capillaries
- recall of fluids
- net movement of fluids into capillaries
- Found in all types of blood vessels except capillaries
- adrenergic nerve endings
- What vessels have richest innervation of adrenergic nerve endings?
- arterioles and arteries
- vasoconstrictor nerve fibers
- important in homeostasis of blood pressure and blood flow, including reflex adjustments that arise from baro and chemoreceptors
- Vasoconstrictor neural input
- controls blood flow and influences peripheral heat exchange
- vasodilation
- inhibition of vasoconstriction
- pressor and depressor are located in?
- vasomotor center in medulla
- function of pressor
- maintain arterial BP even with no afferent input
- function of depressor
- discharges in response to afferent input to inhibit tonic pressor activity in order to optimize BP
- What modifies rate of pressor nerve discharge?
- afferent input and upper CNS input to medulla pressor
- Bainbridge Reflex
- rise in HR in response to rapid infusion of blood or saline; not a response to stretch
- autonomic neurohumoral control
- secretion of epinephrine from adrenal medulla in response to stimulation
- Simulation of what causes autonomic neurohumoral control
- splanchnic nerve, lateral columns of spinal cord, vasomotor center in medulla, or lateral hypothalamus
- function of renin-aldosterone system
- neurohumoral regulating mechanism for body sodium and water content, arterial blood pressure, and potassium balance
- renin
- secreted by kidney; converts angiotensinogen to angiotensin I
- ACE I (angiotensin converting enzyme)
- sound in lungs; coverts angiotensin I to angiotensin II
- most potent vasoconstrictor
- Angiotensin II
- Angiotensin II
- stimulates vasoconstrictor neurons centrally and can cause release of ADH; rapidly metabolized by angiotensinases in peripheral capillary bed
- rate-limiting step in angiotensin production
- renin release
- Where is renin produced?
- juxtaglomerular apparatus of renal artery
- Renin is produced in response to?
- decrease in renal artery pressure, decrease in EC fluid V, stimulation of sympathetic nerves to kidney, or alteration in distal tubule sodium load
- What inhibits renin release?
- elevated blood sodium, potassium, angiotensin II, or ADH
- Where are chemoreeptors located?
- carotid and aortic bodies adjacent to carotid sinus and roor of aorta
- fibers of aortic body run into?
- vagus
- fibers of carotid body arE?
- branches of glossopharyngeal nerves
- Where is largest blood flow?
- carotid body
- What stimulates chemoreceptors?
- anoxia, hypercapnia, and acidosis.
- primary effect of chemoreceptor stimulation on pulmonary and systemic
- reflex vasoconstriciton
- local hypnoxia does what to systemic vascular muscle?
- vasodilation
- local hypnoxia does what to pulmonary vascular muscle
- vasoconstriction
- Circulating Vasoconstrictors
- ADH, Epi, NE, Ang II and Ang I
- Vasodilators
- histamine, EDRF, EDHF, Kinins, Decreased pO2, decreased pH, Increased pCO2, increased temp, adenosine, ANP, Some PG's, Some LT'S, VIP, Substance P, ACh
- Local Vasoconstrictors
- serotonin, vold vasoconstriction, AA PG's, LT's, decreased pO2, and endothelin
- atrioventricular valves
- tricuspid (R) and bicuspid (L)
- semilunar valves
- pulmonary and aortic valves
- RA is continuous with?
- vena cavae
- endocardium
- layer of endothelial cells
- myocardium
- cardiac muscle cells
- epicardium
- connective tissue, fat, and coronary arteries
- distensibility of pericardium
- resists large, rapid increase in cardiac size
- autrhytmicity
- due to automaticity; myogenic spontaneous polarization of cardiac myocytes because of decrease of K+ permeability and conductance
- pacemaker cells
- fastest rate of decrease in K+; more permeable to Na+which keeps resting potential closer to 0; hyperexcitable
- conductivity
- due to intercalated discs allowing transmission of AP's b/w neighboring cells allowing heart to function as a synctitium
- What is responsible for synchronized cardiac cycle
- SA Node-AV node-Bundles of His-Pirkinje fibers-ventricular cells
- Why does cardiac muscle only contract in twitch fashion?
- long duration of AP and long duration of refractory period
- EKG or ECG
- recording of electrical activity of heart; converts minute surface currents to movements or to spot of light on a cathode ray tube
- isoelectric line
- line of no deflection; occurs when entire heart is either depolarized or resting
- P-wave
- occurs when atrial muscle is depolarized
- QRS complex
- ventricular muscle is depolarized
- Lead I
- B/W r AND l ARMS; MOST SENSITIVE TO ACTIVITY SPREADING THROUGH HEART
- Leads II and III
- b/w left leg and right and left arms; most sensitive to activity proceeding from base to apex of heart
- Diastole
- ventricles relax and fill with blood
- Systole
- ventricles are contracting and ejecting blood from heart
- What keeps SL valves shut?
- reverse pressure gradient
- isovolumetric contraction
- both AV and SL valves are closed
- stroke volume
- volume of blood ejected in a single beat
- diastole commences with?
- isovolumetric relaxation phase
- Formula for Stroke volume
- SV+EDV-ESV
- FIRST 2 HEART SOUNDS
- LUB-DUB
- 1st heart sound
- AV valves closing
- 2nd heart sound
- SL valves closing
- 3rd heart sound
- Venous flow into atria
- 4th heart sound
- Venous flow into Ventricle
- Heart murmur
- valvular obstructions causing turbulent blood flow or weak valves causing regurgitation
- Athletes murmur
- large ventricular mass and strong ventricular contractions due to left ventricular hypertrophy
- Cardiac output
- amt of blood pumped out of LV and into aorta during one minute;
- formula for cardiac output
- heart rate x stroke volume
- How is CO regulated?
- changing both strength and rate of contraction
- Frank-Starling's Law of the Heart
- intrinsic ability to adjust output in response to changes in input; underlying mech is L-T relationship
- Sympathetic activity results in?
- increased rate and increased Ca concentration; more rapid and more forceful contractions of ventricles and increased stroke volume
- How does norepinephrine increase the rate of relaxation?
- increases Ca resequestration nto SR
- Parasympathetic activity
- decreases heart contractility; dominant under resting conditions
- myosin
- make thick filaments
- thin filaments
- composed of actin, tropomyosin, and troponin
- actin
- wrap around each other to form double helix
- tropomyosin
- lies on either side of each thin filament in groove formed by double strands of actin; extends length of 7 actin
- troponin
- 3 subunit at end of each of each tropomyosin
- TN I
- inhibitory
- TN T
- Tropomysion associated
- TN C
- Ca binding
- function of myosin crossbridges
- slide thin filaments past thick filaments; shortening sarcomeres and overall muscle
- resting potential of skeletal muscle
- -90 mV
- motor unit
- collection of muscle fibers innervated by a single motor neuron
- myoneural junction
- specialized regions where axons of motor neurons end
- motor end plate
- area of muscle cell membrane in myoneural junction area
- arrival of nerve AP results in?
- release of ACh->binding of nictinic adrenergic receptors->end plate potential->propogated AP
- Depolarization due to ACh receptor actication in result of?
- highly localized increase in conductance of membrane to Na and K
- twitch
- one impulse in nerve gives rise to one impulse in muscle
- What maintains refractory period after AP?
- active Na pump
- tranverse-tubule system
- responsible for rapid inward conductance of electrical impulse; network of fine tubes
- As t-tubules penetrate the fiber, they make contact with?
- SR
- termination of SR longitudinal tubules
- lateral sacs or terminal cisternae
- triads
- t-tubules in contact with 2 terminal cisternae at level of Z line
- final site where electrically controlled event in E-C coupling occurs
- triads
- resting state of Tropomyosin
- myosin heads cannot make contact with actin binding sites
- During activation of tropomyosin
- Calcium is made available from SR and binds TN C; this causes conformation change that TN I releases inhibition and allows tropomyosin to roll out of grooves in actin and expose actin binding sites to myosin
- Reaction sequence
- myosin+ATP=charged myosin intermediate; then interaction with actin; actin-myosin forms an ATPase system that splits ATP into ADP and Pi (energy liberating step); new ATP binds myosin forcing detachment
- mechanical summation
- when muscle is restimulated before it is completely relaxed and 2nd twitch adds to mechanical effect producing longer, stronger contraction
- tetanus
- repeated stimulation producing fusion of individual twitches; state of continued contraction
- What causes fatigue?
- reversible depletion of ATP
- Contracture
- continued rapid sequence of stimuli resulting in gradual decrease in max contractile force and progressively less relaxation in which muscle fails to react maximally before next stimulus becomes effective; result of muscle fatigue
- motor unit summation
- as strength of a stimulus is increased, more individual fibers are stimulated due to motor unit recruitment and strength of contraction of whole muscle is increased
- isotonic
- constant force; e.g. object lifted upwards
- isometric
- same length; only force is generated; e.g. object is too heavy to be moved; no external shortening takes place
- contractions
- isometric->isotonic->isometric(relaxation)
- auxotonic
- force continuously increases while motion continuously occurs e.g. pouring water out of a pitcher
- negative work
- force is constant while muscle is lengtrhening; e.g. descending stairs
- Length-Tension Relationship (optimum length)
- length at which max force can be produced
- Force-Velocity Relationship
- greater the load, lower the velocity; load so great that it can't be lifted then velocity is 0; no load, velocity is max
- Power
- force x velocity
- When is power maximal?
- when force is about 1/3 power
- cardiac muscle cells
- shorter and smaller in diameter; arranged in branching network
- Why do cardiac cells have same striated pattern as skeletal muscle?
- same sarcomere and contractile apparatus structure
- Automaticity is limited to specialized cells in
- SA node, internodal pathways, other atrial sites, around AV node, and in Purkinje system
- 5 Phases of cardiac AP
- 0. initial rapid de or spike overshooting 0 potential by 20-30 1. inital rapid de returning TMP to 0 2. slow re 3. final re returning TMP to restin potential 4. rest TMP with gradual de towards threshold
- Phases of ion conductance
- Na Cl K in; K out; decrease in K conductance in pacemaker cells
- Purposes of intercalated discs
- 1. structural attachment via desmosomes 2. relaying of impulses from one cell to the next via gap junctions
- syncitium
- how individual cardiac cells transmit impulses across cell boundaries
- max tension of cardiac muscle
- 1/3 to 1/2 of skeletal muscle
- fight or flight
- increased sympathetic outflow from ventral hypothalamus to cardioaccelatory center in medulla; increased NE; increased HR and contraction force
- Cardiac muscle does not...?
- tetanize or exhibit summation
- Smooth muscle has
- no organized sarcomere structure; but has thick and thin and intermediate filaments
- Dense plaques
- found in smooth muscle; located on sarcolemna
- dense bodies
- smooth muscle; scattered through cytoplasm
- Multiunit smooth muscle
- every single cell must have neuroreceptors for each cell to control
- Single unit smooth muscle
- gap junctions allow it to function as 1 cell