Muscular System Flashcards
Study of muscles
Myology
Why is muscle tissue highly specialized?
Able to contract and has excitable cells that react to stimulation
Where is muscle tissue found?
All over body
What are the 3 muscle types?
Cardiac, smooth, skeletal
Striated, voluntary, large in size, multinucleated
Skeletal muscle
How is skeletal muscle attached to bone?
By tendons
Functions to move or stabilize skeleton, generate heat, voluntary sphincters
Skeletal muscle
Striated but involuntary, intercalated discs, circulates blood and audtorhythmicity
Cardiac muscle
Non-striated, involuntary, spindle shaped, controls diameter of passageways, moves food, urine, reproductive tract secretions
Smooth muscle
Where is smooth muscle found?
Around blood vessels and in walls of hollow organs
Ability to respond to stimulation by producing action potentials
Excitability
Ability to shorten and/or tense when stimulated by an action potential
Contractility
Ability to return to its original length after contraction or extension
Elasticity
What are the 5 functions of muscles?
Body movement, stabilize body position, store and move substances in body, heat production, store nutrients
What types of nutrients do muscles reserve?
Proteins that are broken down to amino acids
What are the 3 layers of connective tissues in muscles?
Epimysium, perimysium, endmysium
Surrounds entire muscle
Epimysium
Around muscle fascicles
Perimysium
Surrounds individual muscle fibers
Endomysium
Bundles of muscle fibers
Muscle fascicle
Stem cells that repair damaged muscle tissue
Myosatellite cells
Where are myosatellite cells located?
Embedded in endomysium
Extension of the above 3 connective tissue layers
Tendon
Flat, thick tendon
Aponeuroses
Embryonic stem cells that fuse together to form muscle
Myoblasts
Cell membrane of muscle
Sarcolemma
Cytoplasm of muscle
Sarcoplasm
Surrounds each myofibril; stores and releases calcium for muscle contraction
Sarcoplasmic reticulum
Network of tubules used to convey electrical impulses for muscle contraction, allows muscle fiber to contract simultaneously
T Tubules
How are t-tubules formed?
Invaginations of sarcolemma
Scattered among myofibrils; provide ATP
Mitochondria
Make up muscle fibers; bundles of proteins
Myofibrils
How many myofibrils make up a fiber?
1000+
Protein filaments responsible for muscle contractions
Myofilaments
Thin filament
Actin
Thick filament
Myosin
What makes up a sarcomere? How many are in each myofibril?
Actin and myosin, 10,000
Refers to a wasting of muscle due to the loss of myofibrils within muscle fibers
Muscular atrophy
Increase in size of muscle fiber due to increased production of myofibrils
Muscular hypertrophy
When do muscle fibers form?
Before birth
Can fibers regenerate new cells?
No
Cells that can regenerate new cells
Myosatellite cells
What is the organization of muscle from superficial to deep? (10)
Epimysium, whole muscle, perimysium, fascicle, endomysium, sarcolemma, muscle fiber, sarcoplasmic reticulum, myofibril, myofilament
Smallest contractile unit of a muscle fiber; basic functional unit of muscle fiber
Sarcomere
Anchors actin/thin filament; one at each end of sarcomere
Z-disc
Anchors myosin/thick filament; midline of sarcomere
M-line
Contain thick filaments and zone of overlap
A-band
Region where thick and thin filaments overlap
Zone of overlap
Contains only thin filaments
I-band
Striped or striated pattern within myofibrils; alternating dark thick filaments and thin filaments
Striations
Controls tropomyosin and calcium binds to it
Troponin
Lies in actin’s groove and acts to block myosin from attaching to actin’s active site; blocks cross bridge formation
Tropomyosin
Each actin protein has one; blocked by the troponin/tropomyosin complex under normal resting conditions
Active site
Motor protein; short rods (tails) with globular heads (project out towards actin that surrounds it)
Myosin
Double row protein with groove
Actin
Formed when myosin heads interact with actin’s active sites during contraction
Cross-bridges
Where are ATP-binding sites found?
Myosin heads
What happens when myosin cross bridges pull on actin?
Actin slides towards M line alongside myosin
What is the 1st step in the sliding filament theory?
AP leads to release of Ca by sarcoplasmic reticulum, Ca binds to troponin causing the active sites on actin to be exposed
What is the 2nd step in the sliding filament theory?
Cross bridges form when myosin heads bind onto actin
What is the 3rd step in the sliding filament theory?
Myosin heads pivot towards the M line
What is the 4th step in the sliding filament theory?
ATP gives myosin heads energy to unattached and reset
Time period of muscle rigidity following death, due to depletion of ATP
Rigor mortis
Synapse between motor neuron and skeletal muscle fiber
Neuromuscular junction
Site of communication between somatic motor neuron and skeletal muscle fiber of another cell
Synapse
How many NMJ’s does each muscle fiber have?
1
The axon of one motor neuron branches and forms NMJs with _____ muscle fiber cells
many
What is the presynaptic cell in an NMJ?
Axon
What is the postsynaptic cell in an NMJ
Muscle cell
Region of sarcolemma opposite of synaptic terminals
Motor end plate
Expanded tip of the axon at NMJ
Synaptic terminal
Vesicle filled with neurotransmitters
Synaptic vesicle
Space that separates synaptic terminal from motor end plate
Synaptic cleft
What is the 1st step of physiology at NMJ?
Action potential travels down axon to synaptic terminal
What is the 2nd step of physiology at NMJ?
Calcium channels open which causes the exocytosis of synaptic vesicles filled with acetylcholine
What is the 3rd step of physiology at NMJ?
ACh diffuses in to synaptic cleft and binds onto the surface of sarcolemma at the motor end plate, sodium rushes into sarcoplasm
What is the 4th step of physiology at NMJ?
Rush of sodium causes an action potential in the sarcolemma starting the muscle contraction
Enzyme that breaks down ACh
Acetylcholinesterase
Caused by bacterium found in improperly canned foods
Botulinum toxin
What is the function of botulinum toxin?
Blocks release of synaptic vesicles at NMJ
What can no ACh to cause contraction do?
Paralysis of respiratory muscles