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Jasmine Jimenez Period 6 Muscular System - Coggle Diagram
Jasmine Jimenez Period 6 Muscular System
3 Types of Muscles & their Functions
Cardiac
found in the walls of the heart
has branching chains of cells; uni- or binucleate; striations
rapid involuntary contraction and relaxation that helps pump blood throughout the body
Smooth
cells are single, spindle shaped, uninucleate, have no striations
Functions
Respiratory Tract - regulation of bronchiole diameter
Integument - raises hair with erector pili muscle
Genital - contractions during pregnancy, propulsion of sperm
Sensory - dilation and constriction of the pupil as well as changing lens shape
Renal - regulation of urine flow
Gastrointestinal Tract - propulsion of food
found in the unitary muscle, in walls of hollow visceral organs, multi unit muscle in intrinsic eye muscles, airways, large arteries
Skeletal
attached to bones, facial muscles, or to skin
cells are single, long, cylindrical, multinucleate cells with obvious striations, cells referred to as muscle fibers
voluntary control allowing for movement
Major Functions of the Muscular System
Maintain Posture/Body Position
Generate Heat
heat generated when contracting
Produce Movement
responsible for all locomotion & manipulation
Digesting
Pumping Blood
Walking
Stabilize Joints
Sarcomere
smallest contractile unit of a muscle fiber
individual sarcomeres align end to end along myofibril
consists of two myofilaments that cause muscle contraction
thin actin
bind to myosin
pulled on by myosin to cause contraction
thick myosin
head
sit of all activity because they are the ATP binding sites and actin binding sites
no myosin heads at the center of sarcomere
tails
Skeletal Muscles
Body
Anterior
Axial
Sternocleidomastoid
Trapezius
Pectoralis Major
Serratus Anterior
Rectus Abdominus
External Oblique
Illiopsoas
Appendicular
Deltoid
Biceps Brachii
Brachioradialis
Flexor Carpi Radialis
Flexor Carpi Ulnaris
Sartorius
Adductor Longus
Gracilis
Rectus Femoris
Vastus Medialis
Vastus Lateralis
Gastrocnemius
Soleus
Tibialis Anterior
Fibularis Longus
Extensor Digitorum Longus
Posterior
Axial
Infraspinatus
Teres Major
Trapezius
Latissimus Dorsi
Sternocleidomastoid
Gluteus Maximus
Appendicular
Bicep Femoris
Gastrocnemius
Extensor Digitorum
Soleus
Extensor Carpi Radialis
Fibularis Longus
Tricep Brachii
Semitendinosus
Deltoid
Semimembranosus
Facial Muscles
Orbicularis Oris
pucker
Frontalis
raises eyebrows
Buccinator
compresses cheek
Orbicularis Oculi
blink
Zygomaticus
smile
Masseter
prime mover of jaw closure
Temporalis
closes jaw
Sternocleidomastoid
rotate head, flexes neck
Sliding Filament Model
states that when the nervous system stimulates muscle fiber, myosin heads will interact with the binding sites on the actin subunits
these attachments will form and break several times as the thick filaments pull the thin filaments in towards the center of the sarcomere (pulling z discs toward M line, I bands shorten -> H band disappears)
Overall affect: A bands from adjacent sarcomeres get closer together so that the entire muscle cell will shorten
Mechanism by which muscles contract
Neuromuscular Junction
Each muscle fiber has an NMJ
Interface between the nervous system and skeletal muscle
Axon terminals nearly touching muscle fiber separated by synaptic cleft where the muscle produces junctional folds within the postsynaptic membrane
Axon terminal has "bubbles" containing acetylcholine (ACh) the neurotransmitter
When a nerve impulse reaches the end of an axon, axon terminal releases ACh into synaptic cleft
Junctional folds contain ACh receptors, ACh binding to ACh receptors, protein acts as ion channel - opens once ACh binds, sodium ions will enter and potassium ions will leave (but not in equal #, sodium will enter in greater quantity -> affecting membrane potential - > depolarization occurs because inside membrane is now more positive -> causing other nearby channels to open)
Once a particular threshold voltage is reached, this will generate action potential
Sodium diffusing further in the cell
Acetylcholinesterase in synaptic cleft breaks down ACh closing channel, preventing further muscle contraction until another nerve impulse arrives
Action potential will continue to propagate and continue along the sarcolemma and down T tubules (opens up calcium ion release channels)
Repolarization will now occur, Potassium channels will now open and potassium ions that are more highly concentrated within the cell will diffuse out of the muscle fiber -> restoring the negative charge inside
Disorders
Duchenne Muscle Dystrophy (DMD)
muscle destroying disease
sex-linked recessive disease, almost exclusive in males
Rigor Mortis
3-4 hours after death, muscles stiffen
Action Potential in a muscle fiber
After being generated the AP will initiate excitation-contraction coupling
AP causes a rise in levels of calcium (this is what causes filaments to slide)
When a muscle cell is relaxed tropomyosin blocks myosin binding sites on actin subunits but as more calcium ions become present calcium will bind to troponin allowing for myosin-actin binding
Once 2 ions bind it will change shape, push tropomyosin off of myosin binding making them available for cross bridge cycling
In cross bridge cycling the myosin heads use ATP to change conformation and repeatedly pull on the actin filaments to cause contraction
As calcium levels deplete, troponin returns to its original shape, tropomyosin blocks actin's binding sites and muscle fiber relaxes
Muscle Coverings
Perimysium
Covers the fascicle
Endomysium
Covers the Muscle fiber
Epimysium
Covers the muscle