CH 9 & 11 Flashcards
What is the characteristic that allows muscles to pull on bones and organs to create movement called?
Contractility
When muscles stretch and recoil, they recoil to a shorter length. What is this property called?
Elasticity
Skeletal muscle exhibits alternating light and dark bands called
Striations
Muscles that arenotunder conscious control are said to be?
Involuntary
Muscle fibers are bundled together into fascicles by which connective tissue layer?
Perimysium
Which property allows muscle cells to stretch to as much as three times their contracted length?
Extensibility
Because skeletal muscle is under the conscious control it is said to be?
Voluntary
When a muscle lengthens, the collagenous components protect the muscle because they resist?
Stretching
Which muscles are not attached to bones?
Involuntary muscles
Glycogen
a starch-like carbohydrate found in muscle cells that provides energy during intense exercise
The innermost layer of connective tissue that surrounds each muscle fiber
endomysium
Muscle and nerve cells have developed which characteristic more than other cells?
Excitability
The protein found in muscle cells that stores and then releases oxygen when needed
Myoglobin
Which prevents muscle cells from becoming too slack?
Elasticity
Which stem cells fuse to form a muscle fiber?
Myoblasts
When a muscle relaxes, elastic recoil of the collagen helps to return the muscle to its?
resting tension
Which connective tissue layer surrounds the entire muscle?
Epimysium
when a muscle is injured these cells can multiply and help repair the damage
Satellite Cells, stem cells located between a muscle fiber and the endomysium
What is the function of T-tubules?
to stimulate the terminal cisternae to release calcium
What happens to the sarcoplasmic reticulum when a skeletal myofiber is first stimulated?
Calcium is released into the sarcoplasm through gated channels
Infoldings of the sarcolemma that are associated with two terminal cisternae
Transverse Tubules (T-Tubules)
Which protein makes up the thick filaments of a myofibril?
Myosin
4 Components of Thin Filaments
Fibrous (F) actin , Globular (G) actin, Tropomyosin, and Troponin
Which membranous structures conduct impulses through the sarcoplasm to stimulate the release of calcium?
T-tubules
Elastic filaments in a myofibril are made of which protein?
Titin
What are the end-sacs of the sarcoplasmic reticulum called?
Terminal Cisternae
Which is found in thin filaments but is not a regulatory protein?
Actin
A thick filament is composed of pairs of this molecule, intertwined together
Myosin
What happens when calcium ions bind to troponin?
Tropomyosin moves off the active site on actin
Thin filaments are primarily composed of which protein?
F actin
What is the function of T-tubules?
To stimulate the terminal cisternae to release calcium / carry the action potential through the sarcoplasm
Which protein links actin fibers to the inner face of the sarcolemma?
Dystrophin
What stabilizes thick filaments and prevents over-stretching?
Elastic filaments
In a thin filament, each tropomyosin molecule has a small calcium-binding protein bound to it called
Troponin
What are two regulatory proteins found in a myofibril?
Tropomyosin and Troponin
Under the microscope, muscle that has alternating light and dark regions is said to be
Striated
Within a sarcomere, the overlap of actin and myosin produce what bands?
A Bands (anisotropic) , dark bands
A genetic condition in which an abnormal form of the dystrophin protein is produced
Muscular Dystrophy
Within a sarcomere, what is the region within the A band that lacks thin filaments?
H band
What is the portion of a myofibril from one Z disc to another called?
Sarcomere
Which type of neuron controls a skeletal muscle cell?
Somatic motor neuron
What causes skeletal muscle cells to be striated?
the alternating light and dark regions of the sarcomeres
What do all the muscle fibers innervated by a single nerve fiber constitute?
a Motor Unit
When are large motor units used?
Where physical strength is needed
What are light bands in skeletal muscle called?
I bands that are bisected by Z discs
A synapse is the point where a nerve fiber meets a target cell. When the target cell is a muscle fiber, what is this synapse called?
Neuromuscular Junction (NMJ)
Each muscle fiber is innervated by how many motor neurons?
Only one motor neuron per muscle cell
A neuromuscular junction is a type of what?
Synapse
What is a motor unit?
All of the muscle fibers innervated by a single motor nerve fiber
Within a synapse, a neuron ends in a swelling called?
an axon terminal
What are smaller motor units used for?
Fine motor control
What is the neurotransmitter used in a neuromuscular junction?
Acetylcholine (ACh)
I bands are composed primarily of which protein?
Actin (thin filaments)
What is a neuromuscular junction?
A site where a nerve fiber communicates with a muscle fiber
What is the indented region of the sarcolemma that participates in the neuromuscular junction called?
Motor end plate
What are the folds in the sarcolemma at the neuromuscular junction called?
Junctional folds
The synaptic knob does not touch the muscle fiber but is separated by which structure?
Synaptic cleft
What do neurons and muscle cells have in common?
Their membranes undergo voltage changes when stimulated
What is acetylcholine?
The neurotransmitter released at a neuromuscular junction
What is the difference in electrical charge from one point to another called?
electrical potential or voltage
What is the change in membrane potential with the entry of sodium ions called?
Depolarization
During an action potential, the loss of potassium ions from the cell results in what?
Repolarization
The junctional folds of the neuromuscular junction are the site of which receptors?
Acetylcholine (ACh) receptors
Which cells have plasma membranes that undergo voltage changes in response to stimuli?
Neurons and muscle cells
The quick up and down voltage shift from negative to positive, created by the movement of Na and K cations across the cell membrane is called what?
Action potential
the voltage measured across the muscle cell at rest is about -90mV and is called what?
the Resting Membrane Potential (RMP)
What is excitation?
Excitation involves the generation of action potentials, and occurs in both neurons and muscle fibers
During depolarization of a muscle cell or nerve cell, ion channels in the plasma membrane open allowing which ions to enter the cell?
Sodium
When a nerve signal arrives at a synaptic knob, which voltage-gated channels open in the knob?
Calcium channels
During repolarization, which ions diffuse out of the cell, changing the membrane potential back to a negative value?
Potassium
When Ach binds to its receptors on the motor end plate, an ion channel opens and which ions diffuse quickly into the muscle cell?
Sodium
Where does the end-plate potential occur?
Motor end plate
What is action potential?
A rapid fluctuation in the membrane potential following stimulation
Which phase of contraction links the action potential in the sarcolemma to the activation of the myofilament?
Excitation-contraction coupling
The process by which action potentials in a nerve fiber lead to action potentials in a muscle fiber is called what?
Excitation
What must occur before tropomyosin can shift, revealing the active sites that allow myosin heads to bing to the actin filaments?
Calcium must bind to troponin
What potential causes the opening of ion channels, which results in the initial movement of sodium and potassium across the plasma membrane at the neuromuscular junction. If continued, this in turn can trigger an action potential at the neighboring sarcolemma.
The end-plate potential
What is the step in which the muscle fiber develops tension and may shorten?
Contraction
What is the name of the prevailing theory regarding muscle contraction?
Sliding filament theory
The “cocking” of the myosin head, hydrolysis of ATP and the power stroke occur during which phase of skeletal muscle contraction?
Contraction
What does Myosin ATPase do?
it is found in the myosin head and hydrolyzes ATP to release energy
What occurs when calcium binds to troponin?
The troponin-tropomyosin complex changes shape and exposes the myosin binding sites (G active sites)
During contraction, the cocked myosin head binds to an exposed active site onto the actin protein of what?
The thin filament, forming a cross-bridge
The overlapping of myofilaments increases during what?
Muscle contraction
During contraction, what causes a power stroke?
When myosin releases ADP and ratchets to a low energy position
During contraction, each power stroke consumes one molecule of what?
ATP
The cross-bridge created by the binding of a myosin head to an active site on an actin filament is broken by binding what?
ATP
Which stage of contraction occurs when the myosin releases ADP and flexes, pulling the thin filament toward the M line?
Power stroke
What forms a cross bridge?
The cocked head of myosin bound to actin
The Steps of Muscle Relaxation
1) The nerve signal ceases
2) AChE breaks ACh down
3) Active transport pumps in the sarcoplasmic reticulum begin to pump calcium back into the cisternae
4) Calcium releases from troponin
5) Tropomyosin covers the myosin binding sites
What is the enzyme that breaks down acetylcholine?
Acetylcholinesterase (AChE)
How much does a muscle fiber shorten from a single cycle of power and recovery strokes by all the myosin heads?
1% of its resting length
What does the Sarcoplasmic Reticulum do from excitation through contraction?
Releases and reabsorbs calcium continuously
What is the hydrolysis of ATP and preparation for reattachment to the thin filament by the myosin head called?
The Recovery stroke
Why does a filament stay in place when a single myosin head releases?
Because hundreds of other myosin heads are still attached
In which phase does muscle tension decline and sarcoplasmic calcium levels fall?
Relaxation
During which phase of muscle contraction is calcium transported back into the cisternae and tropomyosin moves back to block the actin active sites?
Relaxation
What is the role of acetylcholinesterase?
It breaks down ACh, ending muscle stimulation
After contraction, what causes muscles to return to their resting length?
Elastic elements within the sarcomere
During relaxtion, calcium is actively pumped back into what?
the sarcoplasmic reticulum/ terminal cisternae
What is a lever?
an elongated structure that is utilized to generate a mechanical advantage around a fulcrum
Within skeletal anatomy levers, what supplies the effort?
Muscle contraction
Within skeletal anatomy levers, what serves as the resistance?
Muscle tone, the weight of an object being manipulated, or the weight of the lever itself
What is mechanical advantage?
the ratio of a lever’s output force to its input force
Within a musculoskeletal lever system, what is the fulcrum?
Joints
If a lever’s mechanical advantage is 1.0 or greater, what does it produce?
the lever produces more FORCE (but less speed or distance) than the force exerted on it
If a lever’s mechanical advantage is less than 1.0 what does the lever produce?
it prodcues more speed or distance (but less force) than the force exerted on it
What is a 1st Class Lever?
Fulcrum is between resistance and effort (RFE)
What is a 2nd Class lever?
Resistance is between Fulcrum and Effort (FRE)
What is a 3rd Class lever?
Effort is applied between the fulcrum and resistance (FER). MOST MUSCULOSKELETAL LEVERS ARE 3RD CLASS
Sitting in a chair and raising one thigh is an example of what class of lever system?
2nd Class Lever
Which factors allow the shoulder to have a wide range of motion?
Loose joint capsule and shallow joint cavity
What is the Glenoid Labrum?
fibrocartilage structure that increases the depth of the glenoid cavity
4 muscles of the Rotator Cuff (muscles that stabilize shoulder joint)
Subscapularis, Infraspinatus, Supraspinatus, and Teres Minor (these muscles’ tendons form the rotator cuff)
In TMJ, which ligament prevents posterior displacement of the mandible?
Lateral Ligament
What is the joint that is the articulation between the arm and the shoulder?
Glenohumeral joint
What are the 3 ligaments that support the shoulder joint?
Trasnverse humeral, glenohumeral, and coracohumeral ligaments
What bursae cushion muscles and tissues within the shoulder joint?
The subdeltoid, subacromial, subcoracoid, and subscapular bursae
What is the function of the Olecranon Bursa?
cushions movement of tendons over the posterior aspect of the elbow joint
What are the 2 ligaments that restrict side to side movements of the elbow joint?
Ulnar and Radial Collateral ligaments
Which joint occurs in the elbow region but is not part of the hinge joint?
Proximal Radioulnar joint
What is the function of the Anular Ligament?
Holds head of the radius within the radial notch of the ulna
Which ligament bridges the gap in the inferior margin of the acetabular labrum?
Transverse Acetabular ligament
Where is the Round Ligament (teres) found and where does it connect?
Found within the hip joint, runs from the acetabulum to the fovea capitis
The patellofemoral joint is an example of what class of synovial joint?
Gliding (plane) joint
The medial and lateral patellar retinacula are part of which muscle?
Quadriceps femoris
Which joint is the most complex diarthroses in the body?
The Knee
Which aspect of the knee joint is not covered by the joint capsule?
Anterior
The primary stabilizing structures of the knee include the tendons from which muscles?
Quadriceps and Semimembranosus tendons
What is the function of the Menisci?
to absorb shock and prevent the femur from moving side to side on the tibia
What is the superficial ligament located on the medial surface of the knee?
Tibial Collateral ligament
What aspects (sides) of the knee does the joint capsule cover?
Only the posterior and lateral aspects of the knee
What is the function of the posterior cruciate ligament?
To prevent the tibia from being displaced backward
What are the menisci of the knee composed of?
Fibrocartilage
Hyperextension of the knee is prevented by which ligament?
Anterior Cruciate Ligament (ACL)
Locking the knee causes what to be twisted and taught?
Ligaments
What are the 4 anterior bursae of the knee?
Suprapatellar, Superficial infrapatellar , Deep infrapatellar, and Prepatellar bursae
What is the ankle joint also referred to as?
The Talocrual Joint
In order to lock the knee, what direction does the femur rotate?
Medially
Within the ankle joint, what motion is reduced by the malleoli (bumps of ankle bone) of the tibia and fibula?
Side to side motion
Which ligament binds the fibula to the foot on the lateral side of the ankle?
Lateral collateral ligament
The calf muscles cause plantar flexion of the foot via what tendon?
The Achilles/calcaneal tendon
What is the role of the anterior and posterior tibiofibular ligaments?
To bind the tibia to the fibula
Which ligament binds the tibia to the foot on the medial side of the ankle?
Deltoid Ligament
What is arthritis?
joint pain and inflammation
What is Bursitis?
inflammation of a bursa
What is Dislocation?
displacement of a bone from its normal position (separation of articular surfaces at a joint)
What causes gout?
A build up of uric acid. Produces sharp, paintful crystals in synovial fluid
What is Rheumatism?
general term for conditions characterized by inflammation and pain in joints, muscles, and associated structures
What is a sprain?
a tear in a ligament or tendon
What is a strain?
injury caused by overstretching a tendon or muscle
What is Synovitis?
inflammation of a joint capsule
What is Osteoarthritis?
results from wear and tear of bones. VERY common in people over 70
What is Rheumatoid Arthritis?
an auto immune disease that causes inflammation in synovial joint fluid and deterioration of joints
What structures may be affected by rheumatism?
Muscles, tendons, bones, and ligaments
