Chapter 9 - Muscle System

Question 1

What is smooth muscle?

Answer 1

• Involuntary (Autonomic NS)
• Found on hollow organs
• Not Striated
• Found in Intestine, Bladder, and stomach
• One nuclei 1:1 ratio

Question 2

What is Skeletal Muscle?

Answer 2

• Voluntary (attached to skeleton)
• Striated
• Rapid fatigue
• Has a lot of power
• Multinucleated

Question 3

What is Cardiac Muscle?

Answer 3

• Involuntary (Autonomic)
• Striated
• Intercalated Discs
• Binucleated (2-3)

Question 4

What are the important functions of muscles?

Answer 4

• Produces movement
• Maintains posture and body position
• Stabilizes joints
• Generates Heat as they contract

Question 5

What does muscle not provide?

Answer 5

• Protection (bone provides protection not muscle)

Question 6

What are the characteristics of muscle?

Answer 6

• Responsive
• Conductivity
• Contractility
• Extendibility
• Elasticity

Question 7

What is hyperplasia?

Answer 7

• 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)

Question 8

What is Hypertrophy?

Answer 8

• Increase in cell size
• cells come together to form myotubes that pick up MULTIPLE nuceli along the way
• Occurs after birth or hatching

Question 9

What are embryonic mesoderm cells?

Answer 9

• AKA myoblast under go cell division but can also do it in the right enviroment

Question 10

What is the process of making a myotube?

Answer 10

• 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

Question 11

What is Epimysium?

Answer 11

• Surrounds the entire muscle and defines its volume
• Outer layer of muscle fiber

Question 12

What is the Perimysium?

Answer 12

• a connective tissue sheath that surrounds individual muscle fascicles (bundles of muscle fibers), and separates them from other fascicles within the skeletal muscle

Question 13

What are Fasicles?

Answer 13

• A bundle of muscle fibers

Question 14

What is Endomysium?

Answer 14

• Separates single muscle fibers from one another

Question 15

What is a Sarcolemma?

Answer 15

• AKA plasma membrane
• Conducts the electrical current down the muscle fiber

Question 16

What is the Sarcoplasmic Reticulum?

Answer 16

• AKA endoplasmic reticulum
• dedicated to calcium ion (Ca2+) handling, necessary for muscle contraction and relaxation
• Terminal Cisternae

Question 17

What is the Terminal Cisternae?

Answer 17

• Part of the sarcoplasmic reticulum
• this is where calcium is stored and is released when the action potential travels down the muscle

Question 18

What is the Transverse Tubule?

Answer 18

• Connection point between sarcolemma and the interior portion of muscle fiber

Question 19

What is the triad?

Answer 19

• 2 terminal cisternae
• 1 Transverse tubule

Question 20

What is Glycoside?

Answer 20

• Filled with glycogen (stored glucose)

Question 21

What are myofilaments?

Answer 21

• Contractile proteins
• Contain Actin and Mysoin

Question 22

What is Actin?

Answer 22

• Thin myofilament
• Contains 2 regulatory proteins that try to keep myosin from binding

Question 23

What is Myosin?

Answer 23

• Thick myofilament
• Has myosin head that tries to connect to Actin

Question 24

What makes up the cytoskeleton?

Answer 24

• Actin and Myosin

Question 25

What is the Sarcoplasm?

Answer 25

• Cytoplasm

Question 26

• What are Myofibrils?

Answer 26

• Contractile Units composed of myofilament

Question 27

What is a sacromere?

Answer 27

-Functional unit of muscle fiber (Skeletal Muscle)

Question 28

What do the several mitochondria in the muscle fiber do?

Answer 28

• Creates ATP by using the glucose

Question 29

What is a muscle twitch?

Answer 29

• Response of a muscle to a single brief threshold stimulus
• Single Contraction
• Graded response

Question 30

What are the three phases of a twitch?

Answer 30

• Latent Period
• Period of Contraction
• Period of Relaxation

Question 31

What is the Latent Period?

Answer 31

• Muscle recevies message from the neuron to start the contraction
• AKA excitation-contraction coupling

Question 32

What is the period of contraction?

Answer 32

• Cross bridge forms
• Increase in tension of the muscle

Question 33

What is the period of relaxation?

Answer 33

• Decrease in tension
• Up take of calcium in sarcoplasmic reticulum

Question 34

What is a motor unit?

Answer 34

• Neuron that connects with multiple muscle fibers
• 1 neuron can activate MULTIPLE muscle fibers
• More motor units, more strength, more muscle fibers

Question 35

What causes graded muscle responses?

Answer 35

• Increase in Frequency of the stimulation OR
• Increase in motor units that are stimulated

Question 36

What is an unfused (incomplete) tetanus?

Answer 36

• another stimulus is applied before the muscle relaxes causing more tension resulting in unfused tetanus

Question 37

What is a fused (complete) tetanus?

Answer 37

• Higher stimulus frequencies resulting in no relaxation at all between the stimuli

Question 38

What is the maximal stimulus?

Answer 38

• stimulus strength that it cannot go over no matter how many motor neurons are activated;;;;;

Question 39

What are the steps for a skeletal muscle contraction?

Answer 39

• 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

Question 40

When does the latent period stop and period of contraction begin?

Answer 40

• Latent period ends when Terminal cisternae releases Ca2+ into the sarcoplasma
• This is where period of contraction begins

Question 41

What are the two regulatory proteins found on actin?

Answer 41

• Tropomyosin
• Troponin

Question 42

What does Tropomyosin do?

Answer 42

• Long regulatory protein that blocks the binding site for myosin on Actin
• Long thread

Question 43

What does troponin do?

Answer 43

• Ca2+ binds to troponin and moves tropomyosin away from myosin
• If Ca2+ doesnt bind then myosin head will bind to actin

Question 44

What is the sliding filament theory?

Answer 44

• a muscle fiber contracts when myosin filaments pull actin filaments closer together and thus shorten sarcomeres within a fiber

Question 45

What is the steps of the cross-bridge cycle?

Answer 45

• 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

Question 46

What is the steps of the period of relaxation?

Answer 46

• 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