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Muscular System, Hermione Muro-Meza, period 1 - Coggle Diagram
Muscular System, Hermione Muro-Meza, period 1
Major Functions
- Produce movement : responsible for all locomotion and manipulation
ex: walking, digesting, pumping blood
- Maintain posture and body position
- Stabilize joints
- Generate heat as they contract
Muscle Types
Cardiac
- walls of the heart
- branching chains of cells; uni- or bi-nucleate; striations
Smooth
- unitary muscle in walls of hollow visceral organs (other than the heart); multi unit muscle in intrinsic eye muscle, airways, large arteries
- single, spindle shaped, uni-nucleate; no striations
Skeletal
- attached to bones or (some facial muscles) to skin
- single, very long, cylindrical, multi-nucleate cells with obvious striations
Skeletal Muscle Names
Facial
- temporalis
- zygomaticus
- orbicularis oris
- platysma
- masseter
- orbicularis oculi
- frontalis
Upper Half
- trapezius
- sternocleidomastoid
- deltoid
- pectoralis major
- serratus anterior
- bicep brachii
- tricep brachii
- Brachioradialis
- Flexor carpi radialis
- rectus abdominis
- external oblique
- infraspinatus
- teres major
- latissimus dorsi
- extensor carpi radialis
- flexor carpi ulnaris
- extensor digitorum
Lower Half
- iliopsoas
- adductor longus
- sartorius
- gracilis
- rectus femoris
- vastus medialis
- bicep femoris
- semitendinosus
- semimembranosus
- tibialis anterior
- extensor digitorum longus
- fibularis longus
- gastrocnemius
- soleus
Sacromere
- smallest contractile unit (functional unit) of muscle fiber
- Contains A band with half of an I band at each end
-region between two Z discs
- Individual sarcomeres align end to end along myofibril, like boxcars of train
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Sliding Filament Theory
Contraction: activation of cross bridge to generate force
- shortening happens when tension caused by the cross bridge on thin filaments excess force which opposes the shortening
- relaxed state: thin and thick filaments overlap slightly at ends of A band
Sliding Filament Model:
- sarcolemma: muscle fiber plasma membrane
- sarcoplasm: muscle fiber cytoplasm
- modified organelles: myofibrils, sarcoplasmic reticulum, t-tubules
When contraction occurs is when the thin and thick filament create a cross bridge with ATP which causing the pull of the thin filament which has actin to overlap the thick filament that contains myosin
- Z-discs pulled forward M line
- I bands shorten
-Z-discs become closer
- H zone disappear
- A bands move closer to each other
Action Potential
1. End Plate Potential
generated at the NMJ, the epp causes a wave of depolarization that spreads to the adjacent sarcolemma
2. Depolarization: generating and propagating action potential. Depolarization of the sarcolemma open voltage-gated sodium channels. Na1 enters, following its electrochemical gradient. At a certain membrane voltage, an AP is generated(initiated). The AP spreads to adjacent areas of the sarcolemma and opens voltage-gated Na1 channels there, propagating the AP. The AP propagates along the sarcolemma in all directions, just like ripples from a pebble dropped in a pond.
3. Repolarization: restoration of resting condition
- Na+ voltage-gated channels close, and voltage-gated K+ channels open
- K+ efflux out of cell rapidly brings cell back to initial resting membrane voltage
- Refractory period: muscle fiver cannot be stimulated for a specific amount of time until repolarization is complete
- Ionic conditions of resting-state are restored by Na+ - K+ pump
-Na+ that came into the cell is pumped back out, and K+ that flowed outside is pumped back into cell
Muscle Coverings
Epimysium: dense irregular CT surrounding entire muscle; blend w/ fascia, externally covers muscle (blood vessels and nerve fibers)
Perimysium: fibrous CT surrounding fascicles(group of muscle fibers)
Endomysium: fine areolar CT surrounding each muscle fiber
Disorders
Duchenne Muscular Dystrophy(DMD)
- most common and serious muscular disorder, muscle-destroying diseases that generally appear during childhood
- progresses from extremities upward, finally affecting head, chest muscles, and cardiac muscles
- caused by defective gene for dystrophin, a protein that links thin filaments to extracellular matrix and helps stabilize sarcolemma
Myasthenia Gravis
- characterized by drooping upper eyelids, difficulty swallowing and talking, & generalized muscle weakness
- consist of shortage of ACh receptors
- autoimmune disease
Rigor mortis
- 3-4 hours after death, muscles begin to stiffen
- Intercellular calcium levels increase
- ATP is also needed for cross bridge detachment
- Muscles stay contracted until muscle proteins break down, causing myosin to release text