Lecture 5: Muscles as Systems for Motion and Support

Question 1

cardiac muscle

Answer 1

one of the two types of involuntary muscle … makes up the walls of the heart chambers … the name is due to its location

Question 2

smooth muscle

Answer 2

one of the two types of involuntary muscle … typically found in the walls of hollow organs (such as the stomach, the bladder, the uterus, and the walls of blood vessels) but also found in other locations (such as the tiny muscles in the skin that give us goosebumps or in the iris of the eye to cause the pupil to dilate or constrict) … the name is due to the internal appearance of the cells in this type of muscle

Question 3

skeletal muscle

Answer 3

the only type of voluntary muscle … moves the bones of the skeleton through its attachments … the name is due to its function

Question 4

muscle memory

Answer 4

a voluntary muscle activity generated subconsciously through a defined and coordinated series of neural pathways based on the pattern of a repetitive action … stored in the brain (rather than the muscle) … voluntary because a thought activates the sequence … the brain (not the muscle) stores the pattern

Reflex activity uses many of the same neurons and the same nerves but operates on shorter pathways.

Question 5

reflex

Answer 5

a voluntary muscle activity that uses many of the same neurons and nerves as muscle memory but operates on shorter pathways … the two types are 1) innate (grasping) and 2) learned (protective actions and withdrawal actions)

Question 6

muscle tissue differentiation

Answer 6

muscle tissue is differentiated 1) by their microscopic structure and 2) by whether we can voluntarily control them … this corresponds to their relationship with the nervous system (there are distinct divisions of the nervous system related to the control of voluntary
muscle versus the subconscious control of involuntary muscle)

Question 7

voluntary muscle

Answer 7

its action can be directly or consciously controlled by thought … these are the skeletal muscles

Question 8

involuntary muscle

Answer 8

its action cannot be directly consciously controlled by thought … these are the cardiac and smooth muscles

Question 9

isometric contraction

Answer 9

when a muscle contracts but stays the same length

Question 10

isotonic contraction

Answer 10

when a muscle changes length
1) concentric phase - when the muscle actively shortens when generative force
2) eccentric phase - when the muscle actively lengthens under tension

Question 11

seven main functions of skeletal muscle

Answer 11

1) to move body parts
2) to communicate (spoken written and nonverbal)
3) to remain in a specific still position (from muscle contraction, i.e., for postural muscles)
4) to help stabilize joints
5) to govern the outlets of the urinary and
digestive systems (internal smooth muscle are involuntary)
6) to produce heat (up to 85% of normal body heat is due to the action of skeletal muscles since the reactions that occur within the muscles generate heat as a by-product)
7) to regulate glycemic control (through exercise, which helps to maintain good blood
sugar by using glucose and improving the body’s use of and sensitivity to insulin)

Question 12

skeletal muscles as individual organs (concept rather than definition)

Answer 12

each muscle is considered an individual organ (organs are composed of multiple tissue types) … skeletal muscle tissue has some connective
tissues within it (to work and for stability), which become one with the tendons at either end of the muscle (the tendons that connect muscle to bone don’t disappear; they spread out throughout the muscle and compartmentalize it into bundles of related muscle cells that act as a unit)

Question 13

skeletal muscle parts

Answer 13

muscles come in different sizes and shapes, which have names and relate to the action of that muscle … all skeletal muscles have:
- muscle’s belly
- fascicle > muscle cell > myofibril > sarcomere
- blood vessels/nerves
- connective tissue (epimysium, perimysium, endomysium)
- tendon(s)

Question 14

muscle’s belly

Answer 14

a component of a skeletal muscle … the fleshy mass within the epimysium that is between the tendons (or attached to one tendon) that includes blood vessels and the fascicle, with their muscle cells and myofibril

Question 15

sarcomere

Answer 15

a component of a skeletal muscle … a division of a myofibril divided by Z-disc with A-bands (of actin filiments and myosin) and I-lines (of actin filiments and titen) in between

Question 16

myofibril

Answer 16

a component of a skeletal muscle … a basic rod-like organelle of a muscle cell contained in muscle cells (myofibers) … is actually what creates a contraction

Question 17

muscle cell / myofiber

Answer 17

a component of a skeletal muscle … hold strands of myofibril together … because it can be quite long, can have multiple nuclei …

Question 18

fascicle

Answer 18

a component of a skeletal muscle … a group of muscle cells wrapped together by perimysium … gives a skeletal muscle its grain, a striated appearance of directionality that helps indicate a muscle’s action

Question 19

muscle connective tissue

Answer 19

a component of a skeletal muscle … epimysium surrounds the muscle’s belly, which includes the fascicle and blood vessels, and connects to the tendon or tendons … perimysium surrounds the fascicle … endomysium surrounds the muscle cell

Question 20

tendon

Answer 20

a component of a skeletal muscle … attaches a muscle’s belly to bone … generally, each muscle has a tendon of attachment at either end

Question 21

muscles (concepts rather than definition)

Answer 21

between 600 and 800 muscles in the body … .
the grain (striated appearance) shows directionality that is very helpful in
understanding a muscle’s action … knowing where a muscle is relative to a joint is key to knowing its action … joint movements have partners, i.e., the biceps brachii and the triceps brachii … frequently several muscles work together to move a bone … muscles must contract and generate tension, but they don’t necessarily have to shorten, nor does that force have to cause movement

Question 22

agonist (prime mover)

Answer 22

primary muscle for a given movement

Question 23

synergist

Answer 23

muscle that aids agonist and stabilizes an action

Question 24

antagonist

Answer 24

muscle that must relax in order for an agonist and its synergists to act

Question 25

fixator (stabilizer)

Answer 25

specialized synergist that stabilizes the origin of an agonist to better facilitate the agonist’s action

Question 26

tendons (concepts rather than definition)

Answer 26

generally, most muscles have a tendon of attachment at either end … the tendon of attachment to the bone that the muscle does not move is called the muscle’s origin / superior attachment / proximal attachment … the tendon of attachment to the bone that the muscle moves is known as its insertion / inferior attachment / distal attachment (the position names change because the role of a given muscle can change depending on body position) … some fusiform muscles, i.e., the biceps brachii have two origins

Question 27

intrinsic muscle

Answer 27

muscle located within or situated deeper in a structure, i.e., the hand or foot

Question 28

extrinsic muscle

Answer 28

muscle located superficially in a structure, i.e., the muscles in the forearm that control the hand

Question 29

muscle naming (concepts rather than definition)

Answer 29

• by location, i.e., biceps brachii (the brachium is the arm region, between shoulder and elbow)
• number of heads (bellies), i.e., triceps and biceps
• direction of their cells and, as a result, the direction of their fascicles, or grain, i.e., the external oblique has obliquely oriented
  fibers and the orbicularis oris is a circular (orb-shaped) muscle around the mouth
• the relative size, such as gluteus maximus and gluteus minimus
• the shape, i.e., the deltoid , which is relatively triangular shaped like the Greek letter delta
• the action, i.e., such as the levator scapulae, which elevates the scapula
• the origin and insertion, such as sternocleidomastoid, named for its attachments to the sternum, clavicle, and mastoid process behind the ear.

Question 30

root: sacro

Answer 30

flesh

Question 31

root: myo

Answer 31

muscle