three types of muscles (cardiac,skeletal,smooth), functions, where they are found
Skeletal- organs attached to bones and skin, striated,voluntary,require nervous system stimulation
Cardiac- only in heart, bulk of heart walls, striated, involuntary
Smooth- in walls of hollow organs(stomach,urinary bladder, airways), not striated, involuntary
understand that muscles exhibit excitability, contractility,extensibility,elasticity
Excitability- ability to receive and respond to stimuli
Contractility- ability to shorten forcibly when stimulated
Extensibility- ability to be stretched
Elasticity- ability to recoil to resting length
four important functions of muscles
1. movement of bones or fluids(blood)
2. maintaining posture and body position
3. stabilizing joints
4. heat generation (especially skeletal muscle)
describe connective tissue sheaths that support muscles and the part they cover
Epimysium- dense irregular connective tissue surrounding entire
muscle; may blend with fasccia
Perimysium- fibrous connective tissue surrounding fasicicles(groups of muscle fibers)
Endomysium- fine areolar connective tissue surrounding each muscle fiber
difference between a muscle insertion and origin
a muscle insertion is a movable bone and an origin is immovable (less movable) bone
why skeletal muscles have a striated appearance
how the sliding filament model of muscle contraction works
During contraction, thin filaments slide past thick filaments-->
actin and myosin overlap more
- Occurs when myosin heads bind to actin-->cross bridges
-Myosin heads bind to actin; sliding begins
• Cross bridges form and
break several times,
ratcheting thin filaments toward
center of sarcomere
- Causes shortening of
- Pulls Z discs toward M
structure of the thick (myosin) and thin (actin) filaments
role of troponin and tropomyosin in muscle contraction
Troponin changes shape and moves tropomyosin away from myosin-binding sites
Tropomyosin blocks active sites on actin
how signal travels from a motor neuron to a muscle fiber
Action potential (AP) arrives at axon
terminal at neuromuscular junction
ACh released; binds to receptors
Ion permeability of sarcolemma changes
Local change in membrane voltage
Local depolarization (end plate
potential) ignites AP in sarcolemma
what happens during excitation-contraction coupling
1. The action potential (AP) propagates along the sarcolemma and down the T tubules.
2. Calcium ions are released.
3.Calcium binds to troponin and removes the blocking action of tropomyosin.
4.Contraction begins: Myosin binding to actin forms cross bridges and contraction (cross bridge cycling) begins. At this point, E-C coupling is over.
role of an action potential in releasing calcium ions from the SR
The axon branches to supply a number of muscle fibers called a motor
unit, and the action potential is conveyed to a motor end plate on
each muscle fiber.
(4) At the motor end plate, the action potential causes the release of packets or quanta of acetylcholine into the synaptic clefts on the surface of the muscle fiber.
(5) Acetylcholine causes the electrical resting potential under the motor end plate to change, and this then initiates an action potential which passes in both directions along the surface of the muscle fiber.
(6) At the opening of each transverse tubule onto the muscle fiber surface, the action potential spreads inside the muscle fiber.
(7) At each point where a transverse tubule touches part of the sarcoplasmic reticulum, it causes the sarcoplasmic reticulum to release Ca++ ions.
(8) The calcium ions result in movement of troponin and tropomyosin on their thin filaments, and this enables the myosin molecule heads to "grab and swivel" their way along the thin filament. This is the driving force of muscle contraction
Describe events that occur during the cross bridge cycle
- Cross bridge formation. Energized myosin head attaches to an actin myofilament, forming a cross bridge.
- The power (working) stroke. ADP and Pi are released and the myosin head pivots and bends, changing to its bent low-energy state. As a result it pulls the actin filament toward the M line.
- Cross bridge detachment. After ATP attaches to myosin, the link between myosin and actin weakens, and the myosin head detaches (the cross bridge “breaks”).
- Cocking of the myosin head. As ATP is hydrolyzed to ADP and Pi, the myosin head returns to its prestroke high-energy, or “cocked,” position
explain factors that can affect the force of muscle contraction
Force of contraction depends on number of cross bridges attached, which is affected by:
– Number of muscle fibers stimulated (recruitment)
– Relative size of fibers— hypertrophy of cells increases strength
– Frequency of stimulation
– Degree of muscle stretch
how the longitundinal and circular layers of smooth muscle work together to move substances through hollow organs
• Longitudinal layer
– Fibers parallel to long axis of organ; contraction--> dilates and shortened
• Circular layer
– Fibers in circumference of organ; contracion-->constricts lumen, elongates organ
• Allows peristalsis - Alternating contractions and relaxations of smooth muscle layers that mix and squeeze substances through lumen of hollow organs
types of valves found in the heart, where they are found, and how they function
• Two atrioventricular (AV) valves – Prevent backflow into atria when ventricles contract
– Tricuspid valve (right AV valve)
– Mitral valve (left AV valve, bicuspid valve)
– Chordae tendineae anchor cusps to papillary muscles • Hold valve flaps in closed position
• Two semilunar (SL) valves – Prevent backflow into ventricles when ventricles relax – Open and close in response to pressure changes
– Aortic semilunar valve – Pulmonary semilunar valve
Which of the following components accounts for the bulk of muscle fiber volume (up to 80%)?
The thin filaments are not comprised of which of the following components?
At the neuromuscular junction, the muscle contraction initiation event is ______.
A. a release of calcium ions from the sarcoplasmic reIculum
B. conducIon of an electrical impulse down the T tubules
C. binding of acetylcholine to membrane receptors on the sarcolemma
D. sliding of actin and myosin filaments past each other
binding of acetylcholine to membrane receptors on the sarcolemma
The time period between action potential initiation and mechanical activity of a muscle fiber is called the ______.
A. latent period
B. refractory period
C. action potential
D. excitation period
What is the significance of the muscle fiber triad relationship?
A. The terminal cisterns subdivide the sarcolemma.
B. The T tubules bring calcium to the sarcoplasmic reticulum.
C. The sarcoplasmic reticulum transfers calcium to the T tubules.
D. The T tubules conduct electrical impulses that stimulate calcium release from the sarcoplasmic reIculum
The T tubules conduct electrical impulses that stimulate calcium release from the sarcoplasmic reIculum
What is calcium's function during muscle contraction?
A. Calcium binds to troponin, changing its shape and removing the blocking action of tropomyosin.
B. Calcium binds to troponin to prevent myosin from attaching to actin.
C. Calcium depolarizes the muscle fiber.
D. Calcium flows down the T tubules to stimulate the influx of sodium from the sarcoplasmic reticulum.
Calcium binds to troponin, changing its shape and removing the blocking action of tropomyosin.
In a resting muscle cell, the myosin-binding sites are blocked by ______.
Calcium is released from the terminal cisterns in response to ______.
B. calcium pumps
C. an action potential
an action potential
How does calcium reenter the terminal cisterns after muscle contraction is finished?
B. Active transport
starting with the right atrium, the pathway of blood through the heart, to the lungs, back to the heart, to the rest of the body, and back to the heart
how the differences in pressure in the pulmonary and systemic circuits are reflected in the differences in heart anatomy
the differences and similarities of cardiac and skeletal muscle
the phases of the cardiac cycle, from the atrial systole to ventricular diastole
three wall layers found in arteries and veins
primary function of capillaries
3 types of capillaries and where they are found
how and under what conditions, blood flow is regulated through capillary beds
three sources of resistance described in lecture
relationship between blood flow, blood pressure, and resistance
how blood pressure changes throughout systemic circulation
why low capillary pressure is desirable
the factors that aid the return of blood to the heart through the venous system
how blood pressure is measured
the function of blood flow through body tissues (tissue perfusion)