4th exam-Muscles

Question 1

force of contraction of a muscle varies due to

Answer 1

-nutrient and oxygen availability -frequency of stimulation -amount of stretch before contraction -numbers of muscle fibers contracting

Question 2

effect of amount of stretch before contraction on muscle contraction

Answer 2

-length-tension relationship

Question 3

force of contraction varies with

Answer 3

length of sarcomeres (amount of overlap between thick and thin filaments) before contraction

Question 4

sarcomere short

Answer 4

thick and thin filaments overlap too much before contraction; filaments are compressed and fewer myosin heads can make contact w actin molecules

Question 5

sarcomere long

Answer 5

thick and thin filaments overlap too little; few myosin heads can bind to actin

Question 6

sarcomere moderate

Answer 6

optimal condition

Question 7

skeletal muscle fibers are organized in

Answer 7

motor units

Question 8

all muscle fibers within a moor unit are simulated by a ____

Answer 8

single somatic motor neuron; so the muscle fibers contract in Unison

Question 9

force of contraction depends in part on

Answer 9

size and number of motor units, that are activated at a given time

Question 10

size of motor unit varies from

Answer 10

2-3000 muscle fibers; related to precision of movement

Question 11

process by which number of active motor units increases

Answer 11

motor unit recruitment; weaker motor units recruited first stronger units recruited last

Question 12

cardiac muscle has same arrangement of actin and myosin as

Answer 12

skeletal muscle

Question 13

individual muscle fibers are joined by

Answer 13

intercalated discs; gap junction allows muscle action potentials to “pass from one muscle fiver to the next”

Question 14

cardiac muscle can sustain contraction longer than

Answer 14

skeletal muscle

Question 15

contractile cardiac muscle fibers contract in response to stimuli from

Answer 15

auto rhythmic cardiac muscle fibers

Question 16

smooth muscle can sustain contraction longer than

Answer 16

skeletal muscle

Question 17

two types of smooth muscle

Answer 17

-visceral (single unit) smooth muscle -multi-unit smooth muscle

Question 18

visceral (single unit) smooth muscle is

Answer 18

more common -found in “arteries, veins, hollow organs” -muscle fibers are joined by gap junction so “all fibers contract as single unit

Question 19

multi-unit smooth muscle is

Answer 19

less common -found in “iris, ciliary body, large arteries, airways arrector pili -muscle fibers contract individually

Question 20

smooth muscle fibers include

Answer 20

-thick filaments -thin filaments -intermediate filaments

Question 21

smooth muscle “isnt striated” so thick and thin filaments are not arranged in

Answer 21

sarcomeres

Question 22

filaments are arranged by

Answer 22

attachment to dense bodies

Question 23

dense bodies attach to

Answer 23

sarcolemma

Question 24

thin filaments attach to

Answer 24

dense bodies

Question 25

intermediate filaments stretch between

Answer 25

dense bodies

Question 26

contraction of smooth muscle fibers

Answer 26

-sliding filament mechanism involving thick and thin filaments generate force -force is “transferred to intermediate filaments” -intermediate filaments “pull dense bodies together” -muscle fibers “twist and shorten”