Chapter 9 - Muscle System Flashcards
What is smooth muscle?
- Involuntary (Autonomic NS)
- Found on hollow organs
- Not Striated
- Found in Intestine, Bladder, and stomach
- One nuclei 1:1 ratio
What is Skeletal Muscle?
- Voluntary (attached to skeleton)
- Striated
- Rapid fatigue
- Has a lot of power
- Multinucleated
What is Cardiac Muscle?
- Involuntary (Autonomic)
- Striated
- Intercalated Discs
- Binucleated (2-3)
What are the important functions of muscles?
- Produces movement
- Maintains posture and body position
- Stabilizes joints
- Generates Heat as they contract
What does muscle not provide?
- Protection (bone provides protection not muscle)
What are the characteristics of muscle?
- Responsive
- Conductivity
- Contractility
- Extendibility
- Elasticity
What is hyperplasia?
- Increase in cell #
- ends at birth or when hatched
- (we are born with the same amount of muscle fibers that we have when we get older)
What is Hypertrophy?
- Increase in cell size
- cells come together to form myotubes that pick up MULTIPLE nuceli along the way
- Occurs after birth or hatching
What are embryonic mesoderm cells?
- AKA myoblast under go cell division but can also do it in the right enviroment
What is the process of making a myotube?
- Embryonic mesoderm cells called myoblast under go cell division (Hyperplasia)
- Several myoblasts fuse together to form a myotube
- Myotube matures into skeletal muscle fiber picking up nuclei
What is Epimysium?
- Surrounds the entire muscle and defines its volume
- Outer layer of muscle fiber
What is the Perimysium?
- a connective tissue sheath that surrounds individual muscle fascicles (bundles of muscle fibers), and separates them from other fascicles within the skeletal muscle
What are Fasicles?
- A bundle of muscle fibers
What is Endomysium?
- Separates single muscle fibers from one another
What is a Sarcolemma?
- AKA plasma membrane
- Conducts the electrical current down the muscle fiber
What is the Sarcoplasmic Reticulum?
- AKA endoplasmic reticulum
- dedicated to calcium ion (Ca2+) handling, necessary for muscle contraction and relaxation
- Terminal Cisternae
What is the Terminal Cisternae?
- Part of the sarcoplasmic reticulum
- this is where calcium is stored and is released when the action potential travels down the muscle
What is the Transverse Tubule?
- Connection point between sarcolemma and the interior portion of muscle fiber
What is the triad?
- 2 terminal cisternae
- 1 Transverse tubule
What is Glycoside?
- Filled with glycogen (stored glucose)
What are myofilaments?
- Contractile proteins
- Contain Actin and Mysoin
What is Actin?
- Thin myofilament
- Contains 2 regulatory proteins that try to keep myosin from binding
What is Myosin?
- Thick myofilament
- Has myosin head that tries to connect to Actin
What makes up the cytoskeleton?
- Actin and Myosin
What is the Sarcoplasm?
- Cytoplasm
- What are Myofibrils?
- Contractile Units composed of myofilament
What is a sacromere?
-Functional unit of muscle fiber (Skeletal Muscle)
What do the several mitochondria in the muscle fiber do?
- Creates ATP by using the glucose
What is a muscle twitch?
- Response of a muscle to a single brief threshold stimulus
- Single Contraction
- Graded response
What are the three phases of a twitch?
- Latent Period
- Period of Contraction
- Period of Relaxation
What is the Latent Period?
- Muscle recevies message from the neuron to start the contraction
- AKA excitation-contraction coupling
What is the period of contraction?
- Cross bridge forms
- Increase in tension of the muscle
What is the period of relaxation?
- Decrease in tension
- Up take of calcium in sarcoplasmic reticulum
What is a motor unit?
- Neuron that connects with multiple muscle fibers
- 1 neuron can activate MULTIPLE muscle fibers
- More motor units, more strength, more muscle fibers
What causes graded muscle responses?
- Increase in Frequency of the stimulation OR
- Increase in motor units that are stimulated
What is an unfused (incomplete) tetanus?
- another stimulus is applied before the muscle relaxes causing more tension resulting in unfused tetanus
What is a fused (complete) tetanus?
- Higher stimulus frequencies resulting in no relaxation at all between the stimuli
What is the maximal stimulus?
- stimulus strength that it cannot go over no matter how many motor neurons are activated;;;;;
What are the steps for a skeletal muscle contraction?
- Action Potential travels down the Axon terminal activating Ca2+ channels letting in Ca2+ into the Axon terminal
- Ca2+ enters and interacts with cytoskeletal proteins causing a shift
- When the cytoskeletal proteins shift, this creates a Ach neurotransmitter filled vesicle that binds with plasma membrane
- Vesicle goes through ecocytosis, neurotransmitter moves into synaptic cleft causing a graded potential
- Ach binds to ligan-gated Na+/K+ channels bringing Na+ in and K+ out
- As membrane potential moves towards 0 this creates an action potential (depolarization)
- Action potential leaves the synpatic cleft region generation AP up the sacromere
- AP travels down sacromere to t-tubules generating an AP and causing Ca2+ channels to activate
- Terminal Cisternae release Ca2+ out into sarcoplasma
When does the latent period stop and period of contraction begin?
- Latent period ends when Terminal cisternae releases Ca2+ into the sarcoplasma
- This is where period of contraction begins
What are the two regulatory proteins found on actin?
- Tropomyosin
- Troponin
What does Tropomyosin do?
- Long regulatory protein that blocks the binding site for myosin on Actin
- Long thread
What does troponin do?
- Ca2+ binds to troponin and moves tropomyosin away from myosin
- If Ca2+ doesnt bind then myosin head will bind to actin
What is the sliding filament theory?
- a muscle fiber contracts when myosin filaments pull actin filaments closer together and thus shorten sarcomeres within a fiber
What is the steps of the cross-bridge cycle?
- Cross-bridge formation
-* Myosin head binds to Actin (tropomyosin moves allowing this) - The power stroke
*ADP and Pi are removed from the myosin head, making the myosin pull on the actin - Cross bridge detachment
- ATP binds to myosin head, causing myosin and actin to detach
- Cocking of myosin head
- Myosin head undergoes ATP hydrolysis (removal of one phosphate group)
- This returns/ resets the myosin head until this happens again
What is the steps of the period of relaxation?
- Nerve stimulation ceases, removing Ach
- There is active transport of Ca2+ back to the Sarcoplasmic reticulum
- Tropomyosin moves back over binding sites on Actin
- Returns to resting state
