Muscle structure and function

crossbridges

myosin connecting to actin

when is tension generated

when crossbridges are formed

no crossbridges formed and no generation of active tension occur unless

there is an overlap of actin and myosin

the greater amount of crossbridges

the greater amount of forces generated in sarcomere

what is the amount of active force a muscle can produce dependent on

the length of a muscle

active insufficiency

diminished ability of a muscle to produce or maintain active tension

when does active insufficiency occur

when a muscle has shortened to a point where no further/no additional crossbridges can occur

when can multi-articular muscles not produce an adequate amount of force to complete movement across all joints

the total amount of rotation of all the joints it crosses

concentric

muscle produces force as it shortens

concentric examples

biceps while bringing hand to mouth, elbow flexion

eccentric

muscle produces force as it lengthens

eccentric examples

deltoid while lowering arm down the side, elbow extension

how does the nervous system recruit/activate motor neurons

as needed depending on the demands of the task

motor neurons differ

in size

motor neurons are connected with muscle fibers

of different contractile units

motor neurons could increase

number, size, stimulus

the amount of active force a muscle can produce is

highly dependent on the length of the muscle

which of the following muscles would be most likely to experience active insufficiency

muscle that crosses 3 joints

passive tension in a muscle

directly proportional to extent of elongation of the muscle

in an attempt to increase active muscle force production, the nervous system can

increase rate of stimulation of motor units, recruit larger motor units, recruit additional motor units

the deltoid muscle (prime mover for shoulder flexion) is active ____ when reaching overhead

concentric

the muscle controlling extension of the elbow as occurs while lowering a coffee cup down after taking a sip is ______ which is active _____

biceps, eccentric

for a joint to be able to be PASSIVELY rotated through its full range of motion it requires

normal extensibility/ flexibility of muscles

you are able to passively rotate your patient’s joint through a full and normal range of motion. However, she is unable to actively rotate the joint at all. all of the following could cause this EXCEPT

shortening/contracture of joint capsule

all of the following are true about skeletal muscle function EXCEPT

typically acts with greater leverage compared to external forces

which of the following statements regarding active force production in a muscle are true

active tension is generated anytime a crossbridge is formed, amount of force is directly proportional to number of crossbridges formed, no active force can be produced unless there is some overlap of actin and myosin

which of the following factors could affect muscle activation and function

sincerity of effort by the person, fear of movement after surgery, pain