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Denise Juarez P.2 Muscular System - Coggle Diagram
Denise Juarez P.2 Muscular System
Disorders associated with the Muscular System
Duchenne muscular dystrophy (DMD)
most common and serious form of muscular
dystrophies, muscle-destroying diseases that generally appear during childhood
Inherited as a sex-linked recessive disease
disease progresses from extremities upward, finally affecting head, chest muscles, and
cardiac muscle
Rigor mortis
3–4 hours after death, muscles begin to stiffen
Intracellular calcium levels increase because ATP is no longer being synthesized,
so calcium cannot be pumped back into SR
Muscles stay contracted until muscle proteins break down, causing myosin to
release
Myasthenia Gravis
neuromuscular disorder that blocks nuerotranmistters
autoimmune, possible tumor of the thymus, age, women
muscle weakness, double vision, facial paralysis
Fibromyalgia
muscle pain
physical trauma, abnormal pain response, more common in women
muscle pain, tender points, fatigue
Cerebral Palsy
brain injury or abnormality, premature birth, brain infections
mild to serve, seizures, muscle tightness
Spasic paralysis causing muscle weakness
Myositis
autominnune, infection, muscle trauma
fatigue, muscle weakness, difficulty breathing
inflammation of the skeletal muscle caused by an infection
Action potential in a muscle fiber
AP crosses from neuron to muscle cell via the neurotransmitter acetylcholine
Neurons and muscle cells are excitable cells capable of action potentials
Decision to move is activated by brain, signal is transmitted down spinal cord to motor
neurons which then activate muscle fibers
triggers a sequence of actions that ultimately results in the contraction and relaxation of the muscle fiber.
Skeletal Muscles
Anterior
frontalis
orbicularis oculi
temporalis
massester
zygotematicus
orbicularis oris
sternocleidomastoid
pectoralis major
external oblique
serratus anterior muscle
internal oblique muscle
deltoid
sternohyoid
rectus abdominis
pronator teres
flexor capri radialis
palameris longus
illopsas
biceps brachial
pectinous
brachioradials
adductor longus
tibialis anterior
rectus formis
extensor digitorium longus
gracilis
sartorius
patellar ligament
fibulas longus
soleus
vastus laeralis
vastus medialsis
Posterior
triceps brachial
erector spinae
trapezius
latissimus dorsi
deltoid
levator scapulee
occipitalis
brachioradialis
infraspinatus
teres major
rhomboid major
extensor digitorium
gluteus medius
flexor capri ulnaris
gluteus medius
semitendinosus
extensor capri radialis longus
biceps femoris
soleus
semimembranosus
fibulas longus
gracilis
adductor mangus
gastrocnemius
Major Functions of the Muscular System
Generates Heat as they contract
Stabillize Joints
Produce movement: responsible for locomotion and manipulation
Maintain Posture and Body Position
Nueromuscular Junction
Calcium entry causes release of ACh neurotransmitter into synpatic cleft
ACh diffuses across to ACh receptors (𝑁𝑎+ chemical gates) on sarcolemma
Voltage-gated calcium channels open, calcium enters motor neuron
ACh binding to receptors, opens gates, allowing 𝑁𝑎+ to enter resulting in end plate potential
AP arrives at axon terminal
Acetylcholinesterase degrades ACh
Sliding filament theory of muscle contraction
Contraction: the activation of cross bridges to generate force
shortening occurs when tension generated by cross bridges on thin filaments exceeds forces opposing shortening
contraction ends when cross bridges become inactive
sliding filament model of contraction states that during contraction, thin filaments slide past thick filaments, causing actin and myosin to overlap more
cross bridge attachments form and break several times, each time pulling thin filaments a little closer toward center of sarcome in a ratcheting action
in relaxed state thin and thick filaments overlap only slightly at ends of A band
nervous system stimulates muscle fiber, myosin heads are allowed to bind to actin, forming cross bridges, which cause sliding (contraction) process to begin
Muscle coverings ( connective tissue coverings)
Perimysium:
fibrous connective tissue surrounding fascicles (groups of muscle
fibers)
Endomysium:
fine areolar connective tissue surrounding each muscle fiber
Epimysium:
dense irregular connective tissue surrounding entire muscle; may
blend with fascia
3 types of muscles & their functions
Smooth
in walls of hollow visceral organs
single, spindle shaped, uninucleate, no striations
Cardiac
walls of heart
branching chains of cells, uni-or binucleate, striations
Skeletal
attached to bones or to skin
single, very long, cylindrical multinucleate cells with obvious striations
Sarcomere
Smallest contractile unit (functional unit) of muscle fiber
Contains A band with half of an I band at each end (area between Z discs)
Individual sarcomeres align end to end along myofibril, like boxcars of train
each sarcomere extends from 1 z disc to the next
the basic contractile unit of a muscle fiber
composed of thin and think filaments
Characteristics of Muscle Tissue
Contractility:
ability to shorten forcibly when stimulated
Extensibility:
ability to be stretched
Excitability:
ability to receive and respond to stimuli
Elasticity:
ability to recoil to resting length
Contractions
Isotonic contraction:
muscle shortens because muscle tension exceeds load
muscle changes in length and moves load
Isometric contraction:
no shortening; muscle tension increases but does not exceed load
neithershortens nor lengthens
Thin filaments:
composed of fibrous protein actin
Tropomyosin and troponin: regulatory proteins bound to actin
Thick filaments:
composed of protein myosin that contains two heavy and four light polypeptide chains
Generation of an Action Potential Across the
Sarcolemma
Generation of end plate potential
ACh released from motor neuron binds to ACh receptors on sarcolemma
Causes chemically gated ion channels (ligands) on sarcolemma to open
Results in local depolarization called end plate potential
Depolarization
generation and propagation of an action potential (AP)
If end plate potential causes enough change in membrane voltage to reach critical
level called threshold, voltage-gated 𝑁𝑎+ channels in membrane will open
AP spreads across sarcolemma from one voltage-gated 𝑁𝑎+ channel to next one
in adjacent areas, causing that area to depolarize
Repolarization
restoration of resting conditions
𝐾+ efflux out of cell rapidly brings cell back to initial resting membrane voltage
𝑁𝑎+ voltage-gated channels close, and voltage-gated 𝐾+ channels open
Refractory period: muscle fiber cannot be stimulated for a specific amount of
time, until repolarization is complete