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BIOL 1142 - Exam 2

muscle, cardiovascular system

3 types of muscles skeletal, smooth, cardiac
skeletal muscle muscle that moves the skeleton
smooth muscle muscle used by internal organs (usually for constricting, squeezing - for example, blood vessels, glands)
cardiac muscle found ONLY in the heart
sarcolemma cell membrane/plasma membrane
t-tubules invaginations/tunnels of sarcolemma that penetrate through the thickness of the cell; allow action potentials to quickly reach all of the skeletal muscle
sarcoplasmic reticulum calcium storage
terminal cisternae enlarged areas of sarcoplasmic reticulum that surround t-tubules; usually a pair of terminal cisternae associated with a t-tubule
myofibrils long protein fiber composed of repeating units of sarcomeres
action potentials for muscle cells action potentials require plasma membrane; muscle cell action potentials differ from other action potentials because they need to activate the entire cell thickness
microanatomy of skeletal muscle skeletal muscle -> muscle fascicles -> individual muscle fibers -> myofibrils -> sarcomeres [more details of each division on power point slide chart]
Z disk boundary between adjacent sarcomeres; Z-disks line up to give skeletal muscle a striated appearance
I band light bands, composed of actin (thin) filaments
A band dark bands, composed of myosin (thick) filaments
sarcomere smallest contractile unit of a skeletal or cardiac muscle cell; composed of a Z-disk, 1/2 of an I band (actin - thin, light), A band (myosin - thick, dark), 1/2 of an I band (actin - thin, light), Z disk
myosin thick filaments; associated with A bands; motor protein
tropomyosin blocks the one place on each actin fiber where myosin can bind; helpd in place/postioned by troponin
troponin holds tropomyosin in position until calcium binds with it; calcium binds, changes shape, tropomyosin pulls away from the myosin binding site and allows actin to bind
neuromuscular junction synapse of the motor neuron and the motor end plate; where acetylcholine is released and binds to a nicotinic acetylcholine receptor, results in depolarization of muscle fiber and action potential results
excitation-contraction coupling how an action potential results in the shortening of a muscle cell - link between the action potential in the sarcolemma and the contraction of the muscle
contraction-relaxation cycle the actual shortening of a muscle cell
acetylcholine neurotransmitter released by motor neurons that causes muscle contraction
action potential -> muscle contraction??? describe this slide better Ach released -> binds to AChR at motor end plate -> Na+ enters the cell, causing depolarization -> volt. gated DHP receptors activate -> mech. gated Ca++ channels open -> Ca++ out of SR into sarcoplasm -> Ca++ binds to troponin -> contraction begins
rigor mortis occurs after death; lasts 24-48 hours; muscles contract and no ATP is available to release the myosin from the actin; eventually lysosomes break down muscle cells
twitch muscle fiber response to a single action potential by the motor neuron; twitches can summate; maximum frequency is called tetanus (steady tension)
properties that vary by muscle fiber type speed and tension of onset; maximum tension; duration of twitch
factors that affect tension sarcomere length - muscles have a "sweet spot" where they can produce maximum force); motor neuron frequency;
alternate pathways for ATP production in skeletal muscle (1) creatine phosphate (2) oxidative phosphorylation (3) glycolysis
motor unit motor neuron and all of the muscle cells it innervates
slow-twitch fibers small diameter, low tension, long endurance
fast-twitch oxidative-glycolytic fibers medium tension, endurance or short bursts, respond well to "training"
fast-twitch glycolitic fibers highest force, tire quickly
recruitment when the brain matches the strength of a movement with the correct number of units needed to perform a specific task
asynchronous recruitment nervous system spreads the task amongst a pool of motor units and alternates which units are being used at a given time; good for long activities that require low strength (eg, maintaining posture)
isometric contraction tension remains static; "same length" ex - applying force to try and move an immovable object
isotonic contraction same force, changes in length; concentric or eccentric
eccentric isotonic contraction lengthening muscle contractions
concentric isotonic contractions shortening muscle contractions
control of smooth muscle involuntary; controlled by autonomic nervous system, endocrine system, paracrines, or may be mechanically controlled
anatomical differences between skeletal muscle and smooth muscle smooth muscle is electrically coupled with gap junctions so that excitation can easily spread between cells; smooth muscle has much more complicated anatomy; smooth muscle fibers have longer actin and myosin filamnets, no T-tubules, no sarcomeres
different types of smooth muscle locations include: blood vessels, GI tract, urinary tract, respiratory tract, reproductive tract, ocular
functional differences between skeletal muscle and smooth muscle smooth can depolarize (excite) or hyperpolarize (inhibit); smooth controlled by nervous system or hormones, skeletal only by somatic neurons; smooth has slow, variable tension in multiple directions; Ca++ activates smooth from outside cell
cardiovascular system parts and function blood vessels, blood and the heart; primary function is transport of gasses, heat, waste, water, hormones, nutrients
anatomical features of the heart 2 functional halves divided by interventricular septum; right side - pulmonary circulation, left side - systemic circulation; pericardium (serous membrane), myocardium (muscular wall of the heart), endocardium (thin endothelium inner lining)
pulmonary circulation vena cava -> right atrium -> right atrioventricular valve -> right ventricle -> pulmonary semilunar valve -> pulmonary arteries -> lungs -> pulmonary veins
systemic circulation pulmonary veins -> left atrium -> left atrioventricular valve -> left ventricle -> aortic semilunar valve -> aorta -> arteries to organs -> returns to heart via inferior/superior vena cava
heart valves (1) right atrioventricular valve (tricuspid) (2) pulmonary semilunar valve (3) left atrioventricular valve (bicuspid) (4) aortic semilunar valve
differences between cardiac muscle and skeletal muscle smaller, 1 nucleus; branch, joined by intercalated discs; electrically coupled; graded contractions; require oxygen; wildly different action potentials; have desmosomes and gap junctions; contractions do not summate
2 types of cardiac muscle cells (1) contractile (2) autorhythmic
myocardial contractile cells about 99% of cardiac muscle cells; primary actors in the heart; resting membrane potential is -90 mV; action potential includes depolarization phase, plateau phase, repolarization phase
myocardial autorhytmic cells "pacemaker" cells; highly specialized; functions entirely in action potential production, electrical signal pathway; no sarcomeres or myofibrils, cannot contract; no stable resting membrane potential, each group of pacemaker cells have their own rhythm
cardiac muscle action potentials depolarization - voltage gated Na+ channles open/ends when they close; plateau phase - voltage gated Ca++ channels open/ends when they close; repolarization phase - voltage gated K+ channels open
pacemaker potential unstable "resting" state of myocardial autorhythmic cells
"funny channel" resting membrane potential of myocardial autorhythmic cells; varies widely
electrical signal travel through the heart SA node -> atrial internodal pathway -> AV node -> Bundle of His (AV bundle) -> right and left bundle branches -> Purkinje fibers
AV node located in the inferior right atrium, 50 BPM if allowed to self-regulate,
SA node located in the superior right atrium, rhythmicity of 90-100 BPM
Bundle of His AV bundle; electrically connects the atria and the ventricles
right and left bundle branches branches of the AV bundle that connect to Purkinje fibers located at the apex of the heart
Purkinje fibers transmit electrical signals to the contractile cardiac muscle cells and allow the heart to contract
ANS role in autorhytmicity pSNS nervous system releases ACh which binds with muscarinic (nicotinic) receptors on the SA node and slows heartrate; SNS releases epinephrine which binds to beta 1 adrenergic receptors on the SA node to increase heart rate
ECG electrocardiogram; picks up contractile cell activity and shows electrical activity of the heart, heart rate, heart rhythm, conduction velocity and abnormal physiology
ECG waves P wave - bump QRS wave - spike T wave - bump P wave - P wave - one cardiac cycle
12 lead ECG 12 leads are placed at different parts of the body, allowing reading of electrical signals across several different parts of the heart
cardiac cycle all of the events that happen inside the heart during a single heart beat - electrical activity, muscle contraction, muscle relaxation, changes in blood pressure, changes in volume
diastole relaxation of the heart, filling
systole contraction of the heart, emptying
atrial systole atrial contraction, about 100 msec of each heartbeat
atrial diastole atrial relaxation, about 700 msec of each heartbeat
ventricular systole ventricular contraction, has several phases, about 250 msec of each heartbeat
ventricular diastole ventricular relaxation, lasts until next ventricular systole (some overlap with atrial systole and atrial diastole)
mid-ventricular diastole just prior to the P wave on ECG; venous pressure > atrial pressure > ventricular pressure results in blood flowing into the ventricles; AV valve open, SL valve closed
late ventricular diastole Atrial Systole; P wave on the ECG; atrial pressure > ventricular pressure results in blood flowing into ventricles; AV valve open, SL valve closed; about 30% of blood volume fills ventricles b/c of contraction
early ventricular systole QRS wave on the ECG; ventricular pressure > atrial pressure but ventricular pressure < aortic pressure results in no blood flow; AV valve closed, SL valve closed
end diastolic volume maximum volume of the ventricles, also known as preload
S1 heart sound 1; heard when AV valve closes because ventricular pressure becomes higher than atrial pressure
isovolumetric contraction when heart is contracting but there is no volume changes because all valves are closed due to aterial pressure being greater than ventricular pressure
average arterial pressure 120 (systolic)/80 (diastolic)
ventricular systole S-T segment to mid T-wave on ECG; ventricular pressure > aortic pressure results in ejection of blood from the heart into the arteries; AV valve closed, SL valve open
ejection functional contraction, pumping of blood out into the arteries via the aorta or pulmonary trunk
early ventricular diastole second half of the T-wave on ECG; ventricular pressure > atrial pressure but atrial pressure < aortic pressure results in no blood flow; AV valve closed, SL valve closed
isovolumetric relaxation during early ventricular diastole when all valves are closed and no blood is flowing
S2 heart sound 2, heard when semilunar valve closes
end systolic volume minimum volume of the heart, after blood has been ejected from the heart
stroke volume difference between end diastolic volume (EDV/max volume) and end systolic volume (ESV/min volume); average normal stroke volume is 70 mL per minute ; influenced by length of cardiac muscle fibers before contraction (stretch) and force of contraction
cardiac output volume of blood pumped by a ventricle in one minute; calculated by Heart Rate X Stroke Volume; average normal cardiac output is 4900 mL/min
heart rate 70 BPM is normal average heart rate, calculated by measuring the time between beats
pSNS role in modulation of heart rate tonic parasympathetic activity at the SA node at rest; slows SA node, increases AV node delay, weakens atrial contraction
SNS role in modulation of heart rate speeds SA node, decreases AV node delay, strengthens atrial/ventricular contractions, increases secretion of epinephrine from adrenal medulla, venous constriction results in increase in venous return
preload end diastolic volume (max volume), or how much the ventricles are already stretched before contraction
skeletal muscle pump contraction of skeletal muscles compresses veins and assists blood in returning to heart
respiratory pump change in thoracic pressure due to breathing assists blood in returning to heart
afterload amount of pressure that the ventricle has to generate in order to eject blood into the aorta; affected by aortic pressure (ie, hypertension can place increase workload on the heart)
Starling's law increase in end diastolic volume -> increase in force and increase in stroke volume
actin thin filaments; associated with I bands; myosin binds here to allow sarcomere to shorten/contract
resting membrane potential for a skeletal muscle fiber -90 mV (same as the equilibrium potential for K+)
amount of time a skeletal muscle action potential takes ~10 msec
muscle contraction Ca++ binds to troponin -> moves tropomyosin away from myosin binding site -> myosin heads bind to actin -> release ADP/inorganic phosphates -> power stroke shortens sarcomere -> ATP release actin -> myosin returns to high energy state
muscle fatigue muscle loses the ability to maintain high tension; unsure of exact cause
things that affect how much force a muscle can produce more myofibrils = more sarcomeres = more force
creatine phosphate alternate pathway for ATP production; transfers to ADP readily, converts to ATP at rest; takes energy but is rapid
oxidative phosphorylation alternate pathway for ATP production; mitochondrial production of ATP, slow and limited in how much can be produced, better for endurance activities
glycolysis alternate pathway for ATP production; produces 2 ATP rapidly when glucose is broken down into pyruvate; limited by glucose supplies; lactic acid buildup happens because it can occur anaerobically
fibrous skeleton of the heart between atria and ventricles, valves, coronary sulcus. Electrical insulator, provides complete and total electrical separation from atria and ventricles except for AV bundle.
blood flow through the heart vena cava -> right atrium -> tricuspid valve -> right ventricle -> pulmonary semilunar valve -> pulmonary arteries -> lungs -> pulmonary veins -> left atrium -> bicuspid valve -> left ventricle -> aortic semilunar valve -> aorta
chordae tendineae, papillary muscles prevent prolapse of tricuspid and bicuspid valves
ECG waves and the cardiac cycle P wave - atrial depolarization/systole PQ - plateau phase (atrial diastole) QRS wave - ventricular depolarization ST - plateau (ventricular systole) T wave - ventricular repolarization TP - at resting membrane potential for both atria and ventricles
direction of blood flow and pressure blood always flows from high to low pressue
cardiac cycle all chambers in diastole -> atrial systole -> end diastolic volume -> ventricular systole/atrial diastole -> S1/isovolumetric contraction/ventricular ejection/end-systolic volume -> ventricular diastole -> S2/isovolumetric relaxation
Wigger's diagram graphical summary of all parts of the cardiac cycle
Created by: pinklrt98



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