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Justin Cabrera P.6 Muscular system - Coggle Diagram
Justin Cabrera P.6
Muscular system
Major functions of the muscular system
Maintain posture & body position
Stabilize joints
Produce movement: responsible for all locomotion & manipulation
Generate heat as they contract
Names of all the skeletal muscles(including the facial muscles)
Facial Muscles
Orbicularis Oculi
Thin, flat, muscle eyelid
Function: Closes eye, blinking, & squinting
Frontal Belly
Covers forehead & dome of skull; no bony attachments
Function: Raises the eyebrows, wrinkles forehead skin horizontally
Temporalis
Function: closes jaw, elevates and retracts mandible
Covers temporal, frontal, & parietal bones
Zygomaticus Minor & Major
Muscle pair extending from cheekbone to mouth
Function: Raises lateral corner of mouth
Masteer
Covers lateral aspect of mandibular ramus
Function: Prime mover of jaw closer; elevates mandible
Buccinator
Function: Compresses the cheek
Keeps food between grinding surfaces of teeth
Orbicularis Oris
Multilayered muscle of the lips
Function: Closes lips, protrudes lips
Platysma
thin, sheet like superficial, neck muscle
Function: Tenses skin of neck, helps depress mandible
Skeletal Muscles
Upper half
Pectoralis major
Pectoral muscle
Deltoid
Shoulder Muscle
Trapezius
Back muscle
Serratus Anterior
Abdominal muscle
Sternocleidomastoid
Neck muscle
Rectus Abdominis
Abdominal muscle
Biceps Brachii
Bicep muscle
Brachioradialis
Forearm muscle
tricep brachii
Triceps muscle
Flexor carpi radialis
Forearm muscle
external oblique
Abdominal Muscle
infraspinatus
External Abdominal muscle
teres major
Back muscle
latissimus dorsi
Back Muscle
extensor carpi radialis
Forearm muscles
flexor carpi ulnaris
Forearm muscles
extensor digitorum
Forearm muscles
Lower half
bicep femoris
Hamstring muscle
semitendinosus
Leg muscle
vastus medialis
Quadricep muscle
semimembranosus
Leg muscle
vastus lateralis
Quadricep muscle
tibialis anterior
Leg muscle
rectus femoris
Quadricep muscle
extensor digitorum longus
Leg muscle
gracilis
Quadricep muscle
fibularis longus
Leg muscle
sartorius
Quadricep muscle muscle
gastrocnemius
Leg muscle
adductor longus
Quadriceps muscle
soleus
Leg muscle
iliopsoas
Quadricep muscle
Neuromuscular junction
3.Calcium entry causes release of ACh neurotransmitter into synaptic cleft
4.ACh diffuses across to ACh receptors (𝑁𝑎+chemical gates) on sarcolemma
5.ACh binding to receptors, opens gates, allowing 𝑁𝑎+to enter resulting in end plate potential
AP arrives at axon terminal
6.Acetylcholinesterase degrades ACh
2.Voltage-gated calcium channels open, calcium enters motor neuron
Action potential in a muscle fiber
Depolarization
Large influx of 𝑁𝑎+through channels into cell triggers AP that is unstoppable and will lead to muscle fiber contraction
AP spreads across sarcolemma from one voltage-gated 𝑁𝑎+channel to next one in adjacent areas, causing that area to depolarize
If end plate potential causes enough change in membrane voltage to reach critical level called threshold, voltage-gated𝑁𝑎+channels in membrane will open
3.Repolarization: restoration of resting conditions
𝐾+efflux out of cell rapidly brings cell back to initial resting membrane voltage
Refractory period: muscle fiber cannot be stimulated for a specific amount of time, until repolarization is complete
𝑁𝑎+voltage-gated channels close, and voltage-gated 𝐾+channels open
Ionic conditions of resting state are restored by 𝑁𝑎+−𝐾+pump
1.Generation of end plate potential
auses chemicallygatedion channels (ligands) on sarcolemma to open
𝑁𝑎+diffuses into muscle fiber
ACh released from motor neuron binds to ACh receptors on sarcolemma
Because 𝑁𝑎+diffuses in, interior of sarcolemma becomes less negative (more positive)
Results in local depolarization called end plate potential
Muscle coverings
Epimysium
dense irregular connective tissue surrounding entire muscle; may blend with fascia
Endomysium
fine areolar connective tissue surrounding each muscle fiber
Perimysium
fibrous connective tissue surrounding fascicles(groups of muscle fibers)
3 types of muscles & their functions
Cardiac
Functions: Propels blood into circulation; involuntary control
Locations: Walls of hearts
Characteristics: Has intercalated discs
Smooth
Functions: Voluntary movement, locomotion; voluntary control
Description: Multinucleate cells
Locations: Attached to bone or skin
Skeletal
Location: Bones, Facial muscles, and skin.
Functions: Propels substance/objects; involuntary control
Description: Single, very long, cylindrical, multinucleate cells with obvious striations
Sliding filament theory of muscle contraction
Nervous system stimulates muscle fiber, myosin heads are allowed to bind to actin, forming cross bridges, which cause sliding (contraction)
Cross bridge attachments form and break several times, each time pulling thin filaments a little closer toward center of sarcomein a ratcheting action
During contraction, thin filaments slide past thick filaments, causing actin and myosin to overlap more
Z discs are pulled toward M line
I bands shorten
Z discs become closer
H zones disappear
A bands move closer to each other
Sarcomere
Contains A band with half of an I band at each end
Consists of area between Z discs
Smallest contractile unit (functional unit) of muscle fiber
Individual sarcomeres align end to end along myofibril, like boxcars of train
Disorders
Duchenne muscular dystrophy
muscle-destroying disease
generally appear during childhood
Disease progresses from extremities upward, finally affecting head, chest muscles, and cardiac muscle.
Caused by defective gene for dystrophin, a protein that links thin filaments to extracellular matrix and helps stabilize sarcolemma
Sarcolemma of DMD patients tear easily, allowing entry of excess calcium which damages contractile fibers
Inflammation follows and regenerative capacity is lost resulting in increased apoptosis of muscle cells and drop in muscle mass