muscles Flashcards
4 types of muscle
- visceral (smooth)
- skeletal (striated)
- cardiac
- myoepithelium cells/ myoid cells
visceral (smooth) muscle
- contracts spontaneously/ autonomic nerves
- usually involuntary
- internal organs
skeletal (striated) muscle
- nervous stimulation, usually voluntary
- usually in partly contracted state (tone)
- produce most of body heat in body
cardiac muscle
intermediate, continuous contraction
myoepithelium
cells found in mammary glands; squeeze out milk
myoid cells
found in testes; move semen around
functions of muscle
- produce movement
- restrain movement
- support joints
- produce heat (significant only in endothermic animals)
muscle fibers can be
slow twitch (type 1) or
fast twitch (type 2)
based on contraction time to peak tension
slow twitch muscles/ fibers
- high nedurance
- aerobic; rich blood supply, many mitochondria, much myoglobin “red meat”; use ocygen constantly to remain tone
- comparatively small and weak
- postural +/- propulsive
high twitch muscles/ fibers
- sporadic; low endurance (1-30mins)
- anaerobic ; use intrinsic glycogen store, build up lactic acid and oxygen debt
- used infrequently; rapid burst of activity
- comparatively large and strong
- mainly propulsive
- types IIa, IIx and IIb
muscles names according to
function, position, direction of fiber, shape and form
fascia
connective tissue associated with muscle; tough fibrous tissue
muscles are separated by
fascia; connective tissue
deep fascia
immediately around muscles, continues as tendons at ends of muscle
superficial fascia
loose, under the skin (fascia binds skin to muscle underneath)
deep fascia (aka epimysium) continue at end of muscle to form
tendons
tendons are usually _____ than muscles
thinner
tendons attach to
bone (ex tuberosities and tubercles)
aponeurosis
a broad flat tendon
do tendons have elasticity
some; stores energy for locomotion
____ are stronger than bone
tendons
v strong!!!!
tendons may be associated with
bursae, tendon sheaths or sesamoid bones
bursae
synovial structure between tendon and bone, reduce friction
tendon sheath
an extension of bursae that wrap completely around tendon
sesamoid bones;
bones developed in tendons
origin of muscles
least movement; usually proximal
insertion of muscles
most movement, usually distal
muscles exert force by
contraction of individual muscle fibers
total force of muscle =
sum of indiivudal fibers = cross-sectional area of muscle
more muscle fibers=
greater muscle strength
does length of muscle correlate with strength
no
bigger the muscle fibers =
greater the muscle strength
if muscle A’s diameter is twice the diameter of muscle B, then the cross sectional area of muscle A will be 4x greater than that of muscle B and so
muscle A is 4x stronger than muscle B (even if they are the same length)
long fibers
Greater length (but not necessarily strength) of contraction (muscles can contract about half their size ex if fibers are 30cm than muscle can contract about 15cm further)
short fibers
Shorter length
Lighter, no point being longer if not needed
fusiform muscle
- Fibers concierge on tendon
- Muscle is spindle-shaped thin-round-thin
- Length for length has greatest contractile
Pennate muscle
- Long tendon attachment at an angle
- Powerful due x section but less range of movement
- Cross section is slightly at an angle too (in pic its the solid black line)
- Less contractile length but more strength
- Uni-, bi- multi-pennate
____ may divide muscles
tendons
example clavicular tendon divides brachiocephalic muscle into 3 parts
tendinous inscriptions example
- rectus abdominis (abs) tendinous inscriptions give the 6 pack look
- Muscle fibers run up and down and the tendinous inscription cut across middle (horizontal) (when you exercise muscle get bigger but tendons don’t)
muscle growth and repair
- New fibers not normally formed post-natal;
- Increase in muscle size: increase in size of fibers but not the number of fibers
- After damage, new muscle fibers can form BUT usually connective tissue invades first
how many arteries per muscle
Usually 2+ arteries to a muscle but anastomoses usually incomplete (arteries don’t join together, so if you damage one, you do need to worry about blood supply in that area because one artery one supply blood to whole muscle)
tendons blood supply
poor supply; no hemorrhage if cut but slow healing
nerves usually follow
blood vessels (veins/ arteries)
- Motor, pain, proprioception, stretch, etc
- No motor nerves to tendons
