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Sara Ayala (Period 1) - Concept Map: 05 Muscular - Coggle Diagram
Sara Ayala (Period 1) - Concept Map: 05 Muscular
Major Functions of the Muscular System
Produce Movement:
- Responsible for all bodily locomotion (walking) and manipulation of the internal and external environment (disgusting food, pumping blood)
Maintain Posture and Body Position:
Makes continuous micro adjustments to maintain an erect or seated posture against gravity.
Stabilize Joints:
Keeps joints pulled tightly together and stabilized during movement.
Generate Heat:
Produces heat as a byproduct of muscle contraction to maintain standard body temperature.
Three Types of Muscle & Their Functions:
Skeletal Muscle
Location:
Attached to bones or (or for some facial muscles) directly to skin
Cell Appearance:
Single, very long, cylindrical, multi nucleate cells with visible striations.
Function & Control:
Moves bones and skin, enables locomotion, maintains posture, voluntary control via the somatic nervous system
Cardiac Muscle
Location:
Found exclusively in the walls lf the heart
Cell Appearance:
Branching chains of cells with 1-2 nuclei, striations, and intercalated discs
Functions & Control:
Propels blood into the circulation: involuntary control
Smooth Muscle:
Location:
Walls of hollow visceral organs (stomach, intestine, airways) and intrinsic eye muscles
Cell Appearance:
Single, spindle shaped cells with one central nucleus and no striations
Function & Control:
Propels substances (foodstuffs, urine, fluids) along internal channels, involuntary control
Criteria for Naming Skeletal Muscles
Muscle Location:
Named for the specific bone or body region associated with it (ex. temporalis sits over the temporal bone)
Muscle Shape:
Named for a distinctive geometric shape (ex. deltoid is triangular)
Muscle Size:
Named by relative size (ex. Maximus = largest, Minimus = smallest, Longus = long)
Direction of Muscle Fibers:
Named relative to the body's midline (ex. Rectus = straight/parallel, Transversus = perpendicular, Oblique = at an angle )
Number of Origins:
Named for the number of origin heads (ex. Biceps = 2 origins, Triceps = 3 origins)
Location of Attachments:
Named according to points of origin and intersection, with origin listed first (ex. sternocleidomastoid originates on sternum/clavicle and inserts on mastoid process)
Muscle Action:
Named for the principal movement produced (ex. flexor, extensor, such as extensor capri radialis longus)
Sarcomere (Microscopic Structure):
The functional, smallest contractile unit of skeletal muscle fiber, extending from one Z disc to the next adjacent Z disc
Bands and Markings:
Z Disc (Line):
Coin shaped sheet of proteins that anchors thin filaments and marks the boundary of single sarcomere
I Band:
Lighter region contracting only thin (actin) filaments
A Band:
Dark central region spanning the full length of thick (myosin) filaments
H Zone:
Lighter zone in the center of the dark A Band containing only thick filaments
M Line:
Dark protein line (myomesin) vertically bisecting the H Zone that anchors thick filaments
Myofilaments:
Thick Filaments (Myosin):
Made of myosin protein molecules with flexible tails and two globular heads containing actin binding and ATP binding sites
Thin Filaments (Actin):
Made of double stranded helical chains of actin subunits containing active binding sites for myosin heads
Regulatory & Structural Proteins:
Tropomyosin:
Rod shaped regulatory protein that blocks myosin binding sites on actin when muscle is relaxed
Troponin:
Three polypeptide complex bound to actin and tropomyosin that binds Ca^2+ ions to move tropomyosin out of the way
Titin (Elastic Filament):
Holds thick filaments in place, aids muscle recoil after stretching, and resists overstretching
Dystrophin:
Links thin filaments directly to sarcolemma proteins
Neuromuscular Junction (NMJ):
The specific site where a motor neuron's axon terminal meets a single skeletal muscle fiber (motor end plate)
Structural Components:
Axon Terminal:
The swollen bulb end of a somatic motor neuron axon containing synaptic vesicles filled with acetylcholine (ACh)
Synaptic Cleft:
The fluid/gel filled space separating the axon terminal from the sarcolemma
Junctonal Folds:
Deep infoldings of the sarcolemma at the motor end plate equipped with millions of ACh receptors.
Steps of Transmission at the NMJ:
An action potential travels down the motor neuron axon to the axon terminal.
Voltage gated Ca^2+ channels open, causing Ca^2+ to enter the axon terminal
Ca^2+ influx triggers synaptic vesicles to release ACh into the synaptic cleft via exocytosis
ACh diffuses across the cleft and binds to ACh receptors on the junctional folds
Binding opens chemically gated ion channels, allowing Na+ to follow inside the muscle cell (and K+ to flow out), creating a local depolarization called an end plate potential
Termination: Acetylcholinesterase (AChE) rapidly breaks down ACh in the Cleft to end stimulation
Sliding Filament Theory of Muscle Contraction:
Core Principle:
During contraction, thin filaments slide past thick filaments, increasing overlap between actins and myosin without either filament altering its physical length
Structural Changes During Contraction:
Z discs are pulls closer together toward the M Line.
I Bands shorten
H Zones disappear completely
A Bands move closer together but remain constant in length
Steps of the Cross Bridge Cycle:
1. Cross Bridge Formation:
High energy myosin head binds to exposed active site on actin.
2. Working (Power) Stroke:
Myosin head pivots and bends, pulling the thin actin filament toward the M Line.
3. Cross Bridge Detachment:
ATP molecule binds to the myosin head, causing it to release its hold on actin .
4. Cocking of Myosin Head:
ATP is hydrolyzed into ADP and inorganic phosphate (Pi), returning the mysoin head to its cocked high energy state
Actin Potential Generation in a Muscle Fiber:
Resting State:
The resting sarcolemma is polarized (inside of cell is negative relative to the outside)
Step 1:End of Plate Potential (EPP):
ACh binding at NMJ opens ligand gated channels, Na+ influx makes interior sarcolemma local voltage less negative
Step 2: Depolarization & Propagation:
If local EPP voltage reaches threshold, voltage gated Na+ channels open in sdjacent sarcolemma. Massive Na+ influx triggers an action potential that spreads along the sarcolemma and down into the T tubules
Step 3: Excitation Contraction (E-C) Coupling:
AP passing down T tubules activitates voltage sensing proteins
T tubule proteins trigger Sarcoplasmic Reticulum (SR) terminal cisterns to release stored Ca^2+ into sarcoplasm
Released Ca^2+ binds to troponin, exposing active sites on actin for cross bridge cycling
Step 4: Repolarization:
Voltage gated Na+ channels close and voltage gated K+ channels open
Rapid outflow of K+ restores resting electrical potential
Refractory Period: Time during repolarization when muscle fiber cannot respond to another stimulus
Na+-K+ pump restores original ionic concentration balances
Connective Tissue Coverings (Muscle Coverings)
Epimysium:
Definition:
Outer layer of dense irregular connective tissue surrounding the entire skeletal muscle organ
Function:
Encloses the muscle and can blend into surrounding deep fascia or tendons
Perimysium
Definition:
Fibrous connective tissue sheath wrapping around individual fascicles. (Fascicles: A bundled group of individual muscle fibers within the muscle organ
Endomysium
Definition:
Delicate layer of fine areolar connective tissue surrounding each individual muscle fiber (cell) inside a fascicle
Disorders associated with the Muscular system
Muscular Dystrophy
= Muscle weakness and atrophy
Causes/ Risk Factors:
Genetic, Different types depending on mutation, Duchenne
Symptoms:
Mental retardation, Muscle weakness, Eyelid drooping
Treatment Options:
No known cure, Physical therapy, Medication
Fibromyalgia
= Muscle Pain
Causes/ Risk Factors:
Exact causes is unknown, Physical trauma, Abnormal pain response
Symptoms:
Muscle pain, Tender points, Joint pain
Treatment Options:
Physical therapy, Exercise regimen, Massage
Myasthenia Gravis:
= Neuromuscular disorder that blocks neurotransmitters
Causes/ Risk Factors:
Autoimmune, Possible tumor of the thymus, Age
Symptoms:
Muscle weakness, Shortness of breath, Swallowing and chewing difficulty, Facial paralysis
Treatment Options:
No known cure, Medications, Thymectomy
Cerebral Palsy
= Spastic paralysis causing muscle weakness
Causes or Risk Factors:
Brain injury or abnormality, Hypoxia during, Premature birth
Symptom:
Mild to severe, Delayed development, Muscle tightness
Treatment Options:
No cure, Medication for symptoms, Physical therapy
Myositis
= Inflamation of the muscle
Causes/Risk Factors
Autoimmune, Infection, Medication induced
Symptom:
Muscle weakness, swelling, tenderness
Treatment Options:
Medication, Antibiotics, Reduce inflamation