Chapter 7 Muscular System Flashcards
Functions of skeletal muscle
- Move the skeleton
- Maintain posture and body position
- Support soft tissues
- Guard entrances and exits
- Maintain body temperature
Tissues in Skeletal muscle
- Skeletal muscle tissue
- Connective tissue proper: tendons and ensheathments
- Smooth muscle tissue
- Epithelium
- Nervous tissue
- Blood
Myofibrils
Actin and myosin are arranged in long fibers.
- these do the contraction, and there are lots of them in each muscle fiber
T Tubules
- Surround the myofibrils
- are transverse passageways that run the length of the fiber
- carry information across the cell so the whole fiber contracts together.
- talks to the sarcoplasmic reticulum
Sarcoplasmic reticulum
stores lots of calcium ions, which when released start a contraction
Fascicles
-Bundles of skeletal Muscle fibers surrounded or enclosed with endomysium connective tissue.
Endomysium
- part of a skeletal muscle
- surrounds/encloses fascicles
- help repair damaged tissue
perimysium
Gaps around various fascicles are filled with perimysium
- divides muscles into compartments between the fascicles
Epimysium
Collagen sheath/ barrier or membrane of the muscle
Relation between endomysium, perimysium, and epimysium is. . .
The collagen fibers of all 3 connective tissue layers connect at the ends of the muscle to form one of tow structures:
- Tendon
- Aponeurosis
Tendon
Bundle of collagen (dense Regular connective tissue) hooking muscle to bone
Aponeurosis
Broad sheet of collagen fibers connecting a muscle to the next muscle
sarcomere
- is the repeating unit that makes up the myofilaments of the myofibrils.
- These are why skeletal muscle has striations, and are made of thick and thin filaments
Dark, Thick filaments are made of
Myosin
Light, Thin filaments are made of
actin
H band
is the part of the A band that has myosin but not actin in it
M line
strands of protein arranged perpendicular to the rest of the sarcomere to keep all of the myosin aligned
Z line
The boundary between sarcomeres is made of interconnecting proteins
Steps of a muscle contraction
Step 0: Neurotransmitter Ach released
Step 1: Ach binds to muscle
Step 2: Ach changes membrane polarity start an action potential
Step 3: Action potential gets moved down the t tubules until it gets to the sarcoplasmic reticulum (stores calcium)
Step 4: calcium ion gets released into the cytoplasm
Step 5: Calcium binds to troponin which tells tropomyosin to move off of the actin
Step 6:Myosin head binds to actin (cross bridging)
Step 7: Myosin head releases ADP and phosphate to swivel its head around
Step 8: Contraction of myosin head
Step 9: Need Another ATP to release from actin and relax muscle
Step 10: Myosin breaks down new ATP into ADP and phosphate to release from actin and swivel back to it’s starting position
Step 11: resetting or builds towards tetanus
Contraction: latent period
the time it takes for the action potential to result in calcium release from the sarcoplasmic reticulum
Contraction: Contraction phase
Tension from the contraction of the muscle fibers peaks as myosin binds to actin and pivots
Contraction: Relaxation phase
the cell resets. Calcium is pumped back into the sarcoplasmic reticulum, myosin releases, and active sites are covered back up with tropomyosin.
Tetanus (physiologic)
Maximum amount of muscle tension
- Most muscles operate at incomplete tetanus where the cell is nearly at peak tension
- complete tetanus (ex: charley horse), where the cell doesn’t have enough time to get rid of cytoplasmic calcium and allow relaxation
Tetanus (the disease)
- also called “lockjaw”
- A bacterium enters the nervous system that causes motor neurons to be on full blast
- This leaves your muscle in complete tetanus, so every muscle is contracting at maximum power
- This lasts for week, if you don’t die first.
Rigor mortis
- When someone dies their cells quickly run out of ATP. – This leaves myosin stuck in the swiveled position on an actin, because it needs a new ATP to release and go back to start position.
- Cells run out of ATP so the muscle are unable to relax
Isotonic contraction
- The muscle keeps constant tension.
- This is what happens when you flex your forearm or lift something.
- The muscle changes LENGTH, tension stays the same
- requires MOVEMENT
Isometric contraction
- Tenses enough to maintain the same shape but no more. NO MOVEMENT
- length stays the same, tension changes
- Sitting up and holding a yoga pose are to examples.
origin of a muscle
Point of attachment of a muscle which does not change position when the muscle contracts
insertion of a muscle
- part that is being pulled toward the muscle
Angle of the joint gets smaller
Flexion
Angle of the joint gets bigger
Extension
movement in a circle
rotation
raising movement
elevation
lowering movement
depression
appendage moving away form the midline
Abduction
appendage moving towards the midline
adduction
protraction
moving anteriorly
retraction
moving posteriorly
tensors
muscles whose goal is to tense something up
Agonist
prime mover whose contraction is chiefly responsible for movement
antagonist
the muscle that would pull in the opposite direction
Synergist
Help the agonist do it’s job
List the two main groups of muscles and their sub groups (7)
Axial Muscles
- Head and neck
- spine
- trunk and pelvic floor
Appendicular muscles
- shoulders
- upper limbs
- pelvic girdle
- lower limbsMuscle fatigue definition and two types
- When the muscle can’t perform at the required level despite continued stimulation
- Endurance fatigue
- Burst fatigue
Endurance fatigue
- When muscles break down all of the energy resources they have and don’t have anything else to break down
- occurs in marathoners and endurance athletes
Burst fatigue
The muscle is used so hard that glycolysis happens creating lots of lactic acid which changes the pH so quickly that the muscle can’t do it’s job.
- occurs in sprinters
