Musculoskeletal/Joints/Cartilage Flashcards
What surrounds muscles?
Epimysium
Sense, fibrous, irregular connective tissue
What is a fascicle?
A bundle of muscle fibres
What are fascicles surrounded by?
Perimysium
Dense, irregular, fibrous, connective tissue
What is a muscle fiber?
Muscle cell
Multi-nucleated and striated
What surrounds the muscle cells?
Endomysium
Areolar connective tissue
What is the sarcolemma?
The plasma membrane surrounding the muscle cells, within the endomysium
What is the process of bone movement following the contraction of muscle fibres?
Muscle contracts -> pulls on connective tissue sheath -> pulls on tendon -> pull or move bone
What are the two types of muscle connection to bone?
Direct and Indirect (more common)
What is a direct muscle attachment?
When epimysium fuses with the periosteum or periochondrium
What is an indirect muscle attachment?
When tendons attach muscles (via binding to connective tissue) to bone
What are benefits to indirect muscle attachments?
Tendons are smaller and conserve space
Tendons are more resilient than muscle
What fibre is found in high amounts in tendons?
Collagen
What is found within muscle cells?
Many myofibrils
What is a sarcomere?
The functional component of the myofibril, from Z-disc to Z-disc
What is titin?
Protein that anchors the thick filament to the Z-disc
What is the m-line in a muscle cell?
Its an accessory protein that runs perpendicular to the titin, and attaches to the titin within the thick filament, helping to further stabilize the thick filament
What is the m-line made of?
Myomesin, C proteins, creatinine kinase (functional protein)
What is the anisotropic band?
A-Band. Runs along the length to the thick filament
What is the I band?
Called ‘Isotrope band’
Runs from A-band to A-band
Covers space between intermediate filaments
What is the thin filament?
Troponin (protein that binds actin, Ca, and tropomyosin)
Nebulin (binds to Z-disc)
Tropomyosin (binds to active site of actin to prevent myosin binding)
Actin
What does actin consist of?
Polymerized G-actin that form a double helix structure
What does tropomyosin do?
Wraps around the active site of actin to prevent myosin head from binding.
Happens in resting position
What is troponin?
A protein that works to sense Ca binding.
When Ca binds to it, troponin pulls on tropomyosin which displaces tropomyosin from the active site of actin, allowing myosin to bind to actin, and causing contraction.
How many sections does troponin have and what binds to them?
3 troponin sections;
Troponin C binds to Calcium
Troponin T binds to tropomyosin
Troponin I (inhibitory) which binds to actin
What does myosin attach to?
Thick filament and troponin on the thin filament
What components make myosin?
Head- binds to actin active sites allowing for sliding of filaments. Also has enzyme ATPase activity, which cleaves ATP into ADP. Double head
Neck- has light chains (regulatory (regulate) and essential light chain (stabilize)) that support the head and regulate activity of myosin
Tail- found at thick filament end,. Double helical structure
What is the Z-disc
A long protein consisting of alpha-actinin that runs along the width of the myofibril
Helps with stabilizing thick and thin filaments
What is the H-zone?
Space between two thin filaments within the same sarcomere.
What is the purpose of dystrophin?
Links actin to the sarcolemma on the membrane of the myofibril adding strength
Why is mutation of dystrophin a problem?
Mutations (typically X-linked recessive disorder) means the actin isn't linked to the sarcolemma, and can lead to muscular dystrophy as the muscle cell membranes (sarcolemma) break down over time causing muscle weakness. Duchenne Disease (more severe) and Becker (missense mutation -> misfolded protein, less severe, 10-12 years)
How does skeletal muscle cell appear histologically?
Multinucleated, striated, long, cylindrical
Produces powerful contractions
How does cardiac muscle cell appear histologically?
Branching cells (allows heart to contract AROUND ventricles), one or two nuclei per cell, intercalated discs, some striations
What are the speeds of contraction for each type of muscle?
Skeletal: Fast/medium
Cardiac: Medium
Skeletal: Slow
How does smooth muscle cells appear histologically?
Non-striated, spindle shape with single nuclei, cells formed closely together
In comparison with extracellular environment, are intracellular muscle concentrations of K, Na, Cl, and organic anions higher or lower?
K- higher (150 vs 5)
Na- Lower (12 vs 140)
Cl- Lower (10 vs 105)
Organic Anions- higher (65 vs 0)
What is the typical resting membrane potential of human cells?
-40 to -90 mV in relation to extracellular environment
What ion typically drives the resting membrane potential of cells?
K as it is more permeable to the cell membrane.
What neurotransmitter is utilized at neuromuscular junctions?
Acetylcholine
How does acetylcholine cause excitation? Explain the process of ACh release to muscle contraction.
Released from neural cells at neuromuscular junctions, it opens a channel that is permeable to sodium, and allows positive Na charges into the cell, increasing the cellular membrane potential (to around +40). Depolarization is propagated along sarcolemma of cell, down T-Tubules, and action potential signals release of Ca from cisternae of Sarcoplasmic Reticulum, to sustain the charge. Calcium then binds troponin, causing troponin to unblock actin active site by moving tropomyosin, which allows myosin to bind to actin, and initiate contraction using ATP.
How is action potential achieved in the different muscle types?
In skeletal, ACh release from neuromuscular junctions will depolarize and initiate contraction.
In cardiac muscle, the sinoatrial node contains sodium channels that will spontaneously open to allow sodium entry and initiate depolarization (small levels of Na leak through to help initiate this)
In smooth muscle, sodium entry can be triggered by hormonal release leading to depolarization.
What is the sarcoplasmic reticulum?
It is an specialized endoplasmic reticulum organelle in muscle that stores calcium
How can a given motor neuron cause different stimulation?
There are different branches within the motor neurons that can stimulate different parts of the muscle through acetylcholine release at different neuromuscular junctions
Why are motor ratios useful?
Closer rations (i.e. eye is 1:1) allows for very specific muscular control.
Hand : 1:10
Back: 1:100
What is muscle tonus?
Continual tightness of muscle
Muscle held in steady, partially contracted state
What is muscle tetanus?
Sustained contraction of muscle
Only in skeletal muscle.
What are striations formed of?
Arrangement of proteins, particularly actin and myosin filaments, within the myofibril
How is the myosin head movement related to other heads?
They move in unison to create smooth movement
What allows for the lack of phosphate related fatigue to occur within myofibrils?
Excess phosphate and creatine build up cause muscle fatigue, as well as lactate is anaerobic respiration is utilized.
Fatigue will be reached with extended muscle use though
How is calcium released from the sarcoplasmic reticulum?
Influx of sodium caused by Ach activates the Voltage-sensitive dihydropyridine receptors (L-type Ca channel) within the sarcolemma, linked to the Ryanodine Receptors on the SR, and Ca is released from the sarcoplasmic reticulum.
How is creatine important?
We use it to store energy when muscles are at rest (in the form of ADP and creatine phosphate) and when energy is needed for muscle activation, we create ATP and creatine, so we can use ATP for contraction
What is isometric contraction?
Contraction that produces no movement, i.e. standing, sitting, and posture
What is isotonic movement?
Contraction that produced movement
What is isokinetic movement?
Muscle shortens at a constant speed, and exerts maximum tension over the full range of movement. This is only fully achieved with specially designed weight training equipment,
What are the 3 types of joints?
Fibrous, Cartilage, Synovial
What are the 3 basic structural classifications of joints?
Synarthrosis, Amphiarthrosis, Diarthrosis
What are the types of Synarthrosis joints and what kind of movement does this joint permit?
Extremely strong joints that prevent movement between bones.
Fibrous suture, Gomphosis, Cartilaginous Synchondrosis, Bony Fusion Syndesmosis
Give a brief example of a fibrous suture joint as well as an example.
Bones are interlocked and bound together by dense fibrous tissue.
Only in bones of skull
Give a brief description of a gomphosis joint as well as an example.
Fibrous connection between tooth and alveolar canal forms a periodontal ligament.
Teeth and socket
Give a brief example of a cartilaginous synchondrosis joint as well as an example.
Syn=together, chondro= cartilage
Rigid, cartilaginous bridge between two articulating bones.
Between the ends of first 2 ribs and sternum.
Give a brief description of a bony fusion synostosis joint as well as an example.
Rigid, immovable joint created when bones fuse together.
Epiphyseal lines of long bones, and frontal suture of frontal bone
What are types of amphiarthrosis joints and what movement does this kind of joint permit?
Permits more movement than synarthrosis joints, but is more secure than diarthrosis joints. Articulating bones are joined by cartilage or collagen fibres.
Fibrous Syndesmosis
Cartilaginous symphysis
Give a brief example of a Fibrous Syndesmosis joint as well as an example.
desmos= band or ligament
Bones are connected by a ligament
Distal articulation between the tibia and fibulla
Give a brief description of a cartilaginous symphysis joint as well as an example.
Articulating bones are attached/separated by a wedge of fibrous cartilage
Pubic symphysis
What is a diarthrosis joint and what movement does this kind of joint permit?
A free moving joint
Consists of synovial joints
What are the 6 types of muscle shape?
Flat (parallel fibers often with aponeurosis), Pennate (feather-like), Fusiform (spindle shape with round thick belly), Convergent (start at broad area and converge to single tendon), Quadrate (4 equal sides), Circular (surround opening)
How can pennate muscles within the body differ?
Can be uni/bi/multi pennate, meaning the fibers of the muscle may move in different directions.
i.e. deltoid is multipennate, rectus femoris is bipennate, extensor digitorum longus in unipennate)
What separates the intrinsic back muscles from the superficial back muscles?
Thoracolumbar Fascia
