Animal Movement

Question 1

Muscles

Answer 1

• Biological motors of the body
  
  • composed of multinucleated cells (fibers)
  • Use ATP generated through cellular respiration
  • use contractile proteins to generate force
• Striated muscle (appears stripped), in cardiac and skeletal muscle, actin and myosin in regular patterns
• Smooth muscle (appears uniform), in arteries, digestive and excretory systems, actin and myosin in irregular patterns

Question 2

Organization of Skeletal Muscle

Answer 2

• Muscle belly is the main chunk
• Muscle bundle contains fibers (cell)
• Composed of elongated cells that are embedded within connective tissue
• within the cell is myofibrils (striated)

Question 3

Myofibrils

Answer 3

• Proteins
• Thin (actin) filament
  
  • bound around each other with tropomyosin and troponin
• Thick (myosin) filament
  
  • two proteins wound with two globular heads

Question 4

Sarcomere

Answer 4

• Contractile unit of muscle
• the distance between to z-discs (backbone proteins)
• Actin is attached to the z-disc, titin connects myosin to the actin
  
  • each myosin is surrounded by six actins
• overlap of myosin and actin creates a dark colour in the middle of the sarcomere

Question 5

Sliding filament theory

Answer 5

• When muscle contract, actin and myosin overlap
• when muscles relax actin and myosin stretch
• length does not change, just degree of overlap

Question 6

Muscle Shortening

Answer 6

• Interactions between myosin and actin cause muscle fibers to shorten and produce force
• two heads of myosin bind to actin at specific cites to form cross-bridges

Question 7

Cross-Bridge Cycle

Answer 7

• Myosin head binds to ATP, leading to detachment from actin
• the myosin head catalyzes the hydrolysis of ATP forming ADP and P, cocking the myosin head back
• The myosin head binds to actin, forming a cross-bridge
• ADP and P are released producing a power stroker that generates force and causes the thin filament to slide with the thick one and shorten the sarcomere

Question 8

Motor Neuron endplate

Answer 8

• Motor neuron axons connect to muscle fibers
• a single neuron can connect to multiple fibers

Question 9

excitation contraction coupling

Answer 9

• Skeletal muscles are activated by impulses from nerves
• an action potential causes depolarization of the skeletal muscle cell
• depolarization causes the myosin binding sites to be available for actin binding
• depolarization leads to shortening
  
  • Ca2+ binds to troponin, causing movement of tropomyosin, exposing myosin sites

Question 10

force and velocity are inversely related

Answer 10

• muscles shorten fastest when there is little force
• at high contraction velocities, fewer cross-bridged form, reducing force
• large force production require slow velocity
• Muscle contractions can be shortening, lengthening (greater force) or isometric (velocity=0)
• superfast muscles have evolved rapid cross-bridge cycling (rattlesnakes rattle

Question 11

Muscle force depends on stimulation frequency

Answer 11

• an action potential from a motor nerve causes a muscle fiber to produce a twitch contraction with a slight delay in force
• Ca++ must be released from the SR, and then pumped back in

Question 12

Force summation and tetanus

Answer 12

• Muscle force sums to higher levels when action potentials stimulate the muscle at higher rates, reaching a tetanus (same response as the bacteria)

Question 13

Motor Units

Answer 13

• Same as a motor neuron and the cells it innervates
• Motor size determines how finely a muscle’s force can be controlled
• Depends on stimulation frequency, and the number of motor units activated

Question 14

fast-twitch glycolic fibers

Answer 14

• large diameter
• white, stained yellow
• generate more force than slow-twitch
• energy supplied by anaerobic glycolysis
• few mitochondria, capillaries or myoglobin
• develop force rapidly, fatigue quickly

Question 15

slow-twitch oxidative fibers

Answer 15

• small diameter
• red fibers
• develop force more slowly, resist fatigue
• Aerobic respiration and oxidative phosphorylation
• mitochondria well supplied with oxygen, surrounded by capillaries, contain myoglobin
• oxygen storage molecule, produces red colour

Question 16

Proportions of muscle fibers affect speed of predators and prey

Answer 16

• Cheetahs have glycolic fast twitch
• Antelopes have oxidative slow-twitch and specializes fast-twitch