Week 4

Question 1

myology

Answer 1

scientific study of muscle

Question 2

skeletal muscle

Answer 2

attaches to and moves the skeleton
contractile molecules organized into a striated pattern
under voluntary control

Question 3

smooth muscle

Answer 3

found in walls of hollow organs and blood vessels
contractile molecules not aligned
under involuntary control
connections between cells allow syncytium

Question 4

cardiac muscle

Answer 4

contractile molecules organized in striations
under involuntary control
connections between cells allow them to contract together
syncytium facilitates ejection of blood

Question 5

functions of skeletal muscle

Answer 5

Produce skeletal movement
2. Maintain posture and body position
3. Breathing – the diaphragm is a skeletal muscle
4. Stabilize joints
5. Support soft tissues – e.g support weight of organs
6. Generate heat to maintain body temperature

Question 6

criteria used to name muscles

Answer 6

shape
action
location
division
size relashonships
directions of the fibres

Question 7

fasciculi may:

Answer 7

run parallel to long axis of muscle (greater range of motion, less strength)
insert diagonally into a tendon running in the length of the muscle (smaller range of motion, greater strength)

Question 8

unipennate

Answer 8

all fasciculi insert on one side of a tendon (semimembranous)

Question 9

bipennate

Answer 9

fasciculi insert on both sides of tendon (rectus femurs)

Question 10

multipennate

Answer 10

convergence of several tendons- deltoid

Question 11

longitudinal skeletal muscle

Answer 11

fasciculi run parallel to the long axis of the muscle- sartious, rectus abdonimus

Question 12

radiate convergent skeletal muscle

Answer 12

fibres fan out from a single attachment- pectorals major

Question 13

prime mover

Answer 13

muscle whose contraction is primarily responsible for a particular movement

Question 14

antagonist

Answer 14

muscle that oppose one another upon contraction, antagonists are located on opposite sides of a joint

Question 15

fixators/stabalizers

Answer 15

muscles that immobilize a bone or joint near the origin of the prime mover so that the prime mover can act more efficiently

Question 16

gross anatomy of skeletal muscle

Answer 16

origin: less moveable end of a muscle, usually proximal
insertion: more moveable end of a muscle, usually distal
belly: widest portion of a muscle, between its origin and insertion

Question 17

connective tissue in skeletal muscle

Answer 17

three layers surround:
serve in part to maintain intramuscular pressure, augmenting force production
whole muscle: epimysium
bundles of muscle fibres (fasciculi) perimysium
muscle fibres: endomysium

Question 18

connective tissue

Answer 18

tendons are the extensions of connective tissue membranes beyond the end go the muscle
tendons transmit the force of contractile tissue to bone

Question 19

micro anatomy of skeletal muscle

Answer 19

a muscle cell is a muscle fibre
within each muscle cell/fiber are many myofibrils
each myofibril consists of a large array of contractile proteins arranged repeatedly in series
this gives skeletal muscle its striated patterns of light and dark areas or bands
each repeated array of contractile proteins is called a sarcomere

Question 20

myosin and actin

Answer 20

actin=thin, binding sites fr myosin
mysoin=thick, cross bridges extending from its thick central core

Question 21

sliding filament theory

Answer 21

when a muscle is activated the protruding cross bridges on myosin attach to actin and with the aid of ATP the cross bridge microstructure can rotate thus causing the thin actin filament to slide over myosin. this causes sarcomere to shorten

Question 22

blood supply for skeletal muscle

Answer 22

muscle force increaase= increase instramucualr pressure
occlusion can occur at 15-20% of max muscle force
complete occlusion at 505 of max force
rhythmic contraction and relaxation during exercise like running and cycling facilitate the maintenance of blood flow

Question 23

motor unit

Answer 23

consist of a motor unworn and all the muscle fibres that motor nueorns innervates
cell body located in spinal cord
axon intends from the spinal cord to the target muscle which may be a few mm away or a few feet away

Question 24

slow twitch and fast twitch

Answer 24

endurance athletes have higher than average slow twitch muscle fibres while power athletes have high proportions of fast twitch muscle fibres

Question 25

force control of a motor unit

Answer 25

if a single action potential travels down a motor neurone axon, the motor unit response is a twitch
if many action potentials travel down the axon at a rate faster than the twitch response time fo the motor unit then the mechanical force response will summate
at high motor neurone firing rates this effect an generate on average 5x the force of a single twitch (tetanus)

Question 26

maximally activated

Answer 26

when all motor units are activated at a high firing rate

Question 27

size principle of motor unit recruitment

Answer 27

as the muscle force requirement increases, larger motor units are recruited
slow twitch motor units with the lowest activation threshold are selectively recruited during light to moderate effort
faster and more powerful movements progressively activate fog motor units and then Fg motor units

Question 28

muscle length tension relationship

Answer 28

within the range of sarcomere lengths there is an optimal length at which provides for the greatest possible number of cross bridge formations

Question 29

muscle length tension relationship

Answer 29

longer or shorter than this optimal length the number of cross bridge formations is reduced and thus active force production is reduced

Question 30

concentric contraction

Answer 30

when the velocity is positive, then the muscle is shortening

Question 31

eccentric contraction

Answer 31

if the velocity is negative, then the muscle is lengthening

Question 32

isometric contraction

Answer 32

when the velocity of shortening is 0 there is no change in muscle length

Question 33

angle of muscle pull

Answer 33

muscles act on the bone about the joints to form a lever system
optimal position of the muscle and bone together that determines the maximum amount of tension that can be developed during a single contraction

Question 34

90 degrees muscle pull

Answer 34

at angles greater or lesser than 90 degrees the magnitude of the rotational component of the muscle pull force decreases
while the magnitude of the stabilizing component of the force increases

Question 35

3 factors that affect the expression of strength by a muscle

Answer 35

1. initial length of the muscle fibres
2. spread of shortening
3. angle of pull of the muscle on the bony skeleton

Question 36

sarcopenia

Answer 36

age related loss of skeletal muscle mass, strength and function

Question 37

prevention of sacropenia

Answer 37

strength training
hormonal therapy
dietary intervention
reduction in sedentary time