Chapter 11: Musculoskeletal System Flashcards
What is rhabdomyolysis (break down the name) and why is it interesting regarding WWII?
Rhabdomyolysis (rhabdo - striation, myo - muscle, lysis - breakdown) is the destruction of skeletal muscle. Diagnosis includes presence of creatine kinase upwards of five times the normal amount in the blood, as well as the presence of erythrocyte free urine with the presence of heme points.
This is interesting regarding WWII because of the rampant cases of rhabdomyolysis in London following the 57 day blitzkrieg of the Germans on London. This causes symptoms of pain, swelling, with the effects of depleted blood volume (shock, weakness, low blood pressure, decreased urine output). The compression of the constant bombing led to extreme physical trauma to the muscles that led to the destruction of skeletal muscles.
Musculoskeletal system short hand
MSK
What is oxidative phosphorylation?
Oxidative phosphorylation is the metabolic process that occurs in mitochondria. Uses an electron transport chain which makes a proton gradient generating a proton motive force that utilizes oxygen as a final electron acceptor which creates CO2 as a biproduct.
Essentially the process by which cells use oxygen to covert energy from food to able ATP energy.
What are the three types of muscle?
The three types of muscle are skeletal, smooth, and cardiac.
What is unique about skeletal muscle, what is it innervated by, what is the neurotransmitter that it responds to, is it striated, is it multinucleated, what are the two kinds of skeletal muscle?
Skeletal muscle is responsible for voluntary movement and is innervated by the somatic nervous system and is therefor responsive to acetylcholine (recall that all of the somatic nervous system uses acetylcholine as a neurotransmitter). Skeletal muscle is striated due to presence of sarcomeres and is always multinucleated. Skeletal muscle is made up of two distinct fibers: red fibers (slow twitch) and white fibers (fast twitch).
What are slow twitch and fast twitch muscle fibers, where are they located (in which type of muscle), what is the difference between them?
Slow twitch (red fibers) and fast twitch (white fibers) are two distinguished fibers of skeletal muscle.
Red fibers (slow twitch) have high myoglobin content (responsible for their red appearance) and many mitochondria and therefor primarily derive their energy aerobically (oxidative phosphorylation). Muscles that contract slowly but can sustain activity such as muscles that support posture contain primarily slow twitch muscle fibers.
White fibers (fast twitch) contain less myoglobin and are therefore lighter in color. White fibers have fewer mitochondria and therefore derive most of their energy anaerobically (glycolysis) and tire quickly. White fibers Muscles that contract rapidly but fatigue quickly, such as eyeball muscles, have high quantities of white fibers.
What is smooth muscle, where is it located, is it multinucleated, what is it innervated by, is it striated (why or why not), can it operate without nervous system input (if so, what is that called)?
Smooth muscle is responsible for involuntary action, thus is innervated by the autonomic nervous system. Smooth muscle is not multinucleated. It is not striated as the actin and myosin fibers responsible for contraction and relaxation are not well organized. It can operate without input from the nervous system, which is known as myogenic activity.
Smooth muscle is located in the respiratory tree, digestive tract, bladder, uterus, blood vessel walls, and many other locations.
What is the term for a constant state of low level contraction, such as what is seen in blood vessels or digestion?
This is called tonus.
What is cardiac muscle, what is it composed of, where is it located, is it striated, is it multinucleated, what is it innervated by, can it operate without signal from the nervous system (what’s that called)?
Cardiac muscle is found in the heart and has characteristics of both skeletal and smooth muscle. It is primarily uninucleated but may contain cells with two nuclei. Cardiac muscle appears striated like skeletal muscle, but its action is involuntary and therefor innervated by the autonomic nervous system. It can operate without signal from the nervous system, called myogenic activity.
How do cardiac myocytes communicate with each other?
Cardiac myocytes are connected by intercalated discs which contain gap junctions. The gap junctions are connections between cytoplasm of adjacent cells allowing flow of ions directly between cells. This allows for rapid and coordinated depolarization of muscle cells and efficient contraction of cardiac muscle.
What is the myogenic activity of the cardiac muscle cells? Describe the nodes and pathway of the myogenic activity as well as the intercellular communication of cardiac muscle.
Myogenic activity of cardiac muscle is the ability of cardiac muscle to define and maintain their own rhythm.
Starting at the sinoatrial node (SA), depolarization spreads using conduction pathways to the atrioventricular node (AV). From there, the depolarization spreads to the bundle of His and its branches, and then to the Perkinje fibers. The gap junctions across the intercalated discs allow for progressive depolarization between cells.
How do the nervous system and endocrine system play a role in regulation of cardiac muscle contraction?
The vagus nerve of the parasympathetic nervous system slows the heart rate. Norepinephrine from the sympathetic nervous system (recalling that the post ganglionic cells of the sympathetic nervous system are norandrogenic) and epinephrine from the adrenal medulla bind to ardrenergic receptors in the heart causing increased heart rate and greater contractility. One way that epinephrine does this is by increasing calcium levels within the cardiac myocytes as cardiac contraction, like all muscle, rely on calcium.
What is a sarcomere? What filaments are they made out of, and which is which? What two other proteins go along with the thin filaments, and what anchors the filaments together?
The sarcomere is the basic contractile unit of skeletal muscle and is made of thick and thin filaments. The thick filaments are myosin, the thin filaments are actin. The two other proteins that act along with actin are troponin and tropomyosin, which help regulate the interaction between actin and myosin using calcium. Titin acts as a spring and anchors the actin and myosin fibers together, preventing excessive stretching of the fibers and facilitating the relaxation of the sarcomere.
What are the divided lines, zones, and bands of a sarcomere?
Z-lines: define the boundary of a sarcomere (z is end of alphabet, end of sarcomere)
M-line: runs down the center of a sarcomere (M is is the Middle of the Myosin filaments)
I-band: region containing only thin filaments (I is a thin letter, thin filaments)
H-zone: contains only thick filaments (H is a thick letter, thick filaments)
A-band: contain thick filaments in their entirety, including overlap of thin filaments (A is All of the thick filaments, overlapping or not)
Remember: the A-band size remains constant, all the other zones, bands, and lines become smaller during contraction.
Accurately describe from largest to smallest the gross structure of a muscle down to the sarcomere.
Muscle, muscle fiber (myocytes), myofibril, sarcomere.
What is the sarcoplasmic reticulum, where is it found, and what purpose does it serve?
The sarcoplasmic reticulum is a covering surrounding the myofibrils. The SR is a modified endoplasmic reticulum that contains high concentrations of calcium ions.
What is a myofibril?
A myofibril are a series of sarcomeres that are attached end to end.
What is the name of the cell membrane of a myocyte?
The name of the cell membrane around a myocyte is sarcolemma.
What is the name for the modified cytoplasm located just outside of the sarcoplasmic reticulum?
The name for the modified cytoplasm outside of the SR is the sarcoplasm.
The sarcoplasm is capable of propagating action potential. Which system do they immediately distribute this action potential through? (Hint if needed: perpendicular)
The system that the sarcoplasm propagates action potential through are known as the transverse tubules (T tubules).
What is a muscle fiber? Is there another name for muscle fibers?
A muscle fiber contains many myofibrils arranged in parallel, also called myocytes.
What are the events that initiate muscle contraction, in order? Start with neurotransmitter release and trace the pathway to the point of where myosin binds with actin.
Release of acetylcholine from motor neuron.
Activation of acetylcholine receptors (cholinergic receptors) in sarcolemma.
Depolarization of sarcolemma.
Spreading of signal through transverse tubules.
Release of calcium from sarcoplasmic reticulum.
Binding of calcium to troponin.
Conformational shift of tropomyosin.
Exposure of myosin binding sites on actin.
Myosin binds to actin.
Describe the mechanism by which myosin binding sites are exposed on the thin filament.
Depolarization activates an action potential that ultimately leads to the release of calcium from the sarcoplasmic reticulum. Calcium binds to troponin, causing a conformational shift of tropomyosin which exposes the myosin binding site on actin. Myosin stands ready to bind to the myosin binding sites of actin.
What role does the binding of ATP to the myosin head play in the cross bridge cycle? What about the dissociation of ADP and inorganic phosphate from the myosin head?
ATP allows the myosin head to dissociate from actin. Dissociation of ADP and inorganic phosphate from myosin causes the powerstroke.
It is the dissociation of ADP and Pi from myosin that is responsible for the power stroke, not the hydrolysis of ATP. The binding of ATP is required for releasing the myosin head from the actin filament.
What is the neuromuscular junction?
The neuromuscular junction is where the efferent motor neurons communicate with the muscles, and where contraction begins.
How does relaxation of the muscle occur?
Relaxation of the muscle occurs via the degradation of acetylcholine in the synapse by the acetylcholinesterase. The absence of acetylcholine allows for repolarization of the sarcolemma. As the signal decays, calcium release ceases, and the SR takes up calcium via SERCA pumps (active transport) from the sarcoplasm. Without calcium, tropomyosin covers the myosin binding site of actin and contraction is prevented.
Why do muscle fibers contract in an all or nothing fashion?
Because they are innervated by neurons that deliver signals using action potentials which are an all or nothing phenomena as well. Muscles either respond completely or not at all as stimulus must reach a threshold value. The strength of a response from one muscle cell cannot be changed: it’s all or nothing. Therefor, nerves control overall force by the number of motor units they recruit to respond. Maximal response occurs when all fibers within a muscle are stimulated to contract simultaneously.
How does rigor mortis happen?
ATP production ceases after death. Without ATP, myosin cannot detach from actin making it impossible for muscles to relax and lengthen. Muscles will then be stuck in a contracted state, called rigor mortis.
What is a simple twitch in a muscle fiber? Describe the graph associated with simple twitch.
A simple twitch is the response of a single muscle fiber to a brief stimulus above the threshold. It consist of a latent period (time between reaching threshold and the onset of contraction, the time is explained by the action potential spreading along the muscle and calcium release from SR), a contraction period, and a relaxation period (assuming calcium is cleared from the sarcoplasm.
Describe frequency summation and tetanus.
Frequent and prolonged stimulation will disallow the muscle fiber sufficient time to relax. The contractions combine and become stronger and prolonged, known as frequency summation.
Tetanus is if the contractions are too frequent that the muscle is not able to relax at all.
Prolonged tetanus will result in muscle fatigue.
This is a physiological phenomena of muscle fibers.
What does creatine phosphate do in the muscle cells?
Creatine phosphate is a supplemental energy reserve in muscle. Creatine phosphate is created by transferring a phosphate group from ATP to creatine during times of rest. This can be reversed for muscles to use to quickly generate ATP from ADP.
What is the appendicular skeleton and what does it consist of?
The appendicular skeleton is one of the two major divisions of the skeleton and it consist of bones of the limbs (humerus, radius, ulna, carpals, metacarpals, phalanges, femur, tibia, fibula, tarsals, metatarsals), the pectoral girdle (scapula and clavicle), and pelvis. Bones of the appendicular skeleton are typically long bones which are characterized by cylindrical shafts called DIAPHYSIS that swell at each end to form METAPHYSIS, that terminate in EPIPHYSIS.
Describe the structure of a bone.
The epiphyseal plate is the growth plate that adds length up to adulthood. The epiphysis is the knob end of a bone. The metaphysis is the middle neck between the epiphysis and the diaphysis. The diaphysis is the cylindrical shaft. Periosteum is a fibrous sheath that surrounds the bone that protects and provides a place for muscle attachment and some are capable of differentiating into bone forming cells.
The bony matrix requires uniform distribution of organic and inorganic materials.
What are the structural units called?
Which canals run parallel? Perpendicular? What do those canals contain?
What are mature bone cells called?
The structural units of the bony matrix are called osteons, or Haversian systems.
The longitudinal canals of bone (axis parallel to bone) are called Haversian canals, those that run perpendicular to the axis are called Volkmann canals. These canals contain blood vessels, nerve fibers, and lymph vessels that maintain the health of the bone.
Mature bone cells are called osteocytes.
Osteons contain concentric circles of bony matrix. What are those circles called?
Those concentric circles are called lamellae.
There are small spaces between the lamellar rings. What are those spaces called? What do they house (hint: cells).
Those small spaces are called lacunae (lah-kyoon-eye) and they house osteocytes.
There are tiny channels that connect the lacunae. What are they called and what do they do?
Those channels are called canaliculi (can-uh-lick-you-lie). Canuliculi allow for the exchange of nutrients and waste between osteocytes and the Haversian and Volkmann canals.
What is bone remodeling? What two cell types are largely responsible for bone remodeling? What causes bone remodeling (hint: activity)?
Bone remodeling is the breakdown and rebuilding of bone. Osteoblasts build bone, osteoclasts (polynucleated resident macrophages of bone) resorb (degrade) bone. Bone remodeling occurs in response to stress and remodels in such a way as to accommodate the repetitive stresses faced by the body.
What is a synovial capsule?
A synovial capsule encloses the actual joint cavity (articular cavity)
What is the synovium and what does it secrete? Is synovium cartilage?
The synovium is a layer of soft tissue in movable joints that secretes synovial fluid which lubricates the movement of structures in the joint space.
Synovium is not cartilage, it is a soft tissue that lines joints.
What is articular cartilage?
Articular cartilage contributes to the joint by coating the articular surfaces of the bone so that impact is restricted to the lubricated joint.
Muscles can be classified by the types of movement the coordinate.
Flexor? (Flexion)
Extensor? (Extension)
Abductor? (Abduction)
Adductor? (Adduction)
Medial rotation?
Lateral rotation?
Flexor: decreases angle across a joint (like bicep brachii, brachii means “of the arm”)
Extensor: increases the angle across the joint (like tricep brachii, brachii means “of the arm)
Abductor: moves body part away from the midline (deltoid muscle)
Adductor: moves body part toward the midline (pectoralis major)
Medial rotation: rotates axis of limb toward midline (subscapularis)
Lateral rotation: rotates axis of limb away from midline (infraspinatus)
