Muscular System Flashcards
Describe the morphology of skeletal muscle cell
- extremely long and cylindrical shape
- Nuclei are peripherally located
- Cells are multinucleate
- Striated
Why skeletal muscle fiber is multinucleated?
B/c there’s embryonic mesoderm cells that divide and increase
What is the functional organelle of skeletal muscle fiber?
Myofibrils
What is the smallest functional unit of muscle fiber?
Sarcomeres
Do muscle cells divide? Describe cellular differences that are associated w/ muscular “hypertrophy” vs “atrophy”.
Muscle cells don’t divide
Increase in cell size (hypertrophy) vs decrease in cell size (atrophy)
Describe in detail the 5 major structural components of a sarcomere
- Z disk(c): Boundaries of each sarcomere
- Actin (thin) myofilament: Extend from Z disc towards center of sarcomere
- Myosin (thick) Myofilament: Located in center of sarcomere
- M-Line: Bisects the myosin myofilaments
- Titin: Springlike molecule that resists overstretching
ALL ARE PROTEINS
What is the source of skeletal muscle fibers being striated?
Source of striation is myosin and actin myofilament
What are the three regions of the myofibril?
- I Band
- H Zone
- A Band
What happens in the A band?
More and thicker structures that allows for less light to pass through (More myosin)
What happens in the I band?
Less structure and allows more light to pass through (no myosin)
What happens in the H zone?
Occurs in less structured middle of the A band (no actin)
What structures can be found in the I band?
Z-Disc, Titin, and Actin
What structures can be found in the A band?
Myosin, actin, m line, and titin
What structures can be found in the H zone?
Myosin, M line, and titin.
What happens to the 3 regions during full contraction?
A band doesn’t change in size
H zone disappears
I band gets smaller
Describe conducting system of skeletal muscle to trigger muscle contraction
- Neurotransmitters are released from the ends of somatic motor neurons that stimulate sarcolemma
- Action potential spreads throughout the sarcolemma of muscle cells
- Action potential hits deeper and hits sarcoplasmic reticulum, which triggers it to release calcium inside the cell
- Once calcium is released; actin and myosin are triggered to slide and create contraction of sarcomere
What is rigor mortis?
Stiffness of skeletal muscle after death
What causes rigor mortis, and how muscle relaxes after RM?
Cause: Sarcoplasmic reticulum leaks calcium signaling myofibrils to contract (body stiffens)
Relaxation: As proteins denature, actin and myosin detach then the body relaxes
What is a bundle of muscle fibers called?
Fascicle or fasciculus
What are the 3 connective tissues of skeletal muscles?
- epimysium
- perimysium
- endomysium
What is epimysium?
Fibrous covering of whole muscle
What is perimysium?
Fibrous covering of fascicle
What is endomysium?
Fibrous covering of a single cell (muscle fiber)
Describe origin and insertion of a skeletal muscle
Origin: One end of muscle acts as an anchor (doesn’t move)
Insertion: Other end attaches to the bone that is moving (moves during contraction)
What’s tendon?
Structure that connects muscle to bone; made of dense regular proper connective tissue
What’s aponeruosis?
A flat tendon
When you extended your cubital joint, what are the prime mover, and antagonist muscles?
Prime mover (agonist): Triceps
Antagonist: Biceps
What are characteristics that muscles names are based on? (7)
- location
- size
- shape
- orientation of fasciculi
- origin/insertion
- # of heads
- Function
What are two muscles based on location?
- Pectoral
- Brachial
What are 2 muscles that are based on size?
- gluteus medius
- gluteus maximus
What are 2 muscles based on shape?
- deltoid
- trapezius
What are 2 muscles based on orientation of fasciculi?
- rectus
- oblique
What are 2 muscles based on origin/insertion?
- digiti
- carpi
What are 2 muscles based on # of heads?
- biceps
- triceps
What are 3 muscles based on function?
- extensor
- flexor
- pronator
What is a primer mover?
Primarily responsible for generating movement
What is a antagonist?
Muscle that does the opposite of th agonist
What is a synergist?
Muscle that helps out
What does the fixator do?
Stabilize one part of the body during movement of another part
When you flex your cubital joint, what are the prime mover, synergist, and antagonist?
Primer Mover - Biceps
Antagonist - Triceps
Synergist - Brachialis
What are the 13 characteristics of skeletal muscles?
- cell size: extremely long
- nuclei? : multinucleated
- shape: cylindrical
- location: attached to the bone
- sarcomeres? Yes
- striated?: Yes
- Interconnected?: No
- Sarcoplasmic reticulum?: Yes
- Transverse Tubules?: Yes
- Source of calcium: Sarcoplasmic reticulum
- Speed of contraction: very rapid
- Nervous control: Voluntary
- Fatigue: Tires rapidly
What are the 13 characteristics of cardiac muscles?
- cell size: normal cell size
- nuclei? : mononucleated
- shape: cylindrical branched
- location: heart
- sarcomeres? Yes
- striated?: Yes
- Interconnected?: Yes
- Sarcoplasmic reticulum?: Yes
- Transverse Tubules?: Yes
- Source of calcium: Sarcoplasmic reticulum & external (blood)
- Speed of contraction: rapid
- Nervous control: autorhythmic involuntary
- Fatigue: does not tire
What are 13 characteristics of smooth muscles?
- cell size: slightly longer cell size
- nuclei? : mononucleated
- shape: spindle
- location: walls of hollow organs and tubes
- sarcomeres? no
- striated?: no
- Interconnected?: Yes (GI Tract) and No (Eye Iris)
- Sarcoplasmic reticulum?: no
- Transverse Tubules?: no
- Source of calcium: External blood
- Speed of contraction: Slow
- Nervous control: Involuntary
- Fatigue: Does not tires (Latches)
Difference b/w multiunit and visceral smooth muscles?
Multiunit: are not interconnected, has precisely controlled movement, and example is the iris (eye)
Visceral: Interconnected like cardiac muscle and has rhythmic pulsating contractions
What are the 5 functions of the muscular system?
- Produce movement of skeleton
- Maintain posture and body position
- Supports soft tissue
- Guard entrances and exits
- Generate heat
What are skeletal muscle cells also called?
- Muscle fibers
Where do muscle tissues develop from?
- Myoblasts fuse together to form muscle fibers
What are sarcomeres?
Long row of repeating segments that consists of the smallest functional unit of muscle cell
What is the sliding filament theory?
Actin slides towards myosin during contraction
What is the sarcolemma?
The muscle cell membrane
What is transverse tubules?
Folded sarcolemma tubules that conduct electrical impulses
What is the sarcoplasm?
Cytoplasm of the muscle cell/fiber
- Contains sarcoplasmic reticulum
What is the sarcoplasmic reticulum?
Network of membranous channels around each myofibril
- stores calcium and is continuously pumping calcium in and out
What is the triad?
Connecting point b/w surface signal of the T tubule and the two terminal cisterns of sarcoplasmic reticulum
What is the neuromuscular junction?
The link b/w nervous system and muscular system in which the “synapse” or space where motor neurons meet muscle
What neurons dictate the contraction of skeletal muscle fibers?
Somatic motor neurons