Musculoskeletal (theory) Flashcards
three muscle tissue types
- skeletal muscle
- cardia muscle
- smooth muscle
muscle tissue properties
- excitability
- contractility
- extensibility
- elasticity
excitability
responds to stimuli
ex… nerve innervation
contractility
muscle’s ability to shorten
extensibility
to contract over a range of resting lengths
elasticity
ability to rebound to its original length
SKM functions
- skeletal movement –> pulling on tendons to move bones
- maintain posture –> stabilize the joints
- soft tissue support –> of the visceral organs
- regulate material entrance and exit
- maintain body temp
regulate material entrance and exit
there is SKM to voluntarily control…
1. swallowing
2. defecation
3. urination
body temp maintanance
the contraction of muscles can produce heat
ex… we shiver to maintain our body heat
gross anatomy
the study of the muscles and associated structures as a whole…
- muscle organization
- connective tissue associated with muscles
- nerves innervating muscles
- blood vessels associated with muscles
microscopic anatomy of the muscle
studying the components of a muscle
- myofibrils
- myofilaments
- sarcomeres
sarcomeres
the smallest unit of muscle contraction
made up of overlapping actin and myosin
parallel to the long axis of the cell
muscle connective tissue
all connective tissue associated with skeletal muscle is dense tissue…
- epimysium
- perimysium
- endomysium
epimysium
surrounds the entire muscle
perimysium
divides the muscle into fascicles, blood vessels reside in the perimysium
endomysium
surrounds the individual muscle fibers, surrounds myofibrils
myofibrils
surrounded by epimysium
responsible for contraction and are attached to the sarcolemma
myofilaments
makes up the myofibrils, made up of thick and thin filaments
tendons
connects muscle to bone
the epimysium, perimysium, and endomysium converge to form tendons
aponeuroses
connects muscle to muscle
nerve innervation
penetrates the epimysium
NTs are released onto receptors of the muscle (NMJ)
multiple sclerosis
attack of the myeline sheaths resulting in weakened muscle contractions
myasthenia gravis
destruction of muscle receptors for acetylcholine
blood vessels innervation
parallel to the nerves that innervate the epimysium
branch networks to accommodate flexion and extension
sarcolemma
muscle tissue plasma membrane, gets depolarized first when ACh acts on receptor
sarcoplasm
muscle cell cytosol
order of depolarization
- sarcolemma
- t tubules
- sarcoplasmic reticulum
t tubules
junctions in the sarcolemma that reach into the muscle and neighbor the sarcoplasmic reticulum
myosatellite cells
stem cells to help recover damaged muscle cells, these are lost over time
muscle cell striations
made up of overlapping actin and myosin filaments
sarcoplasmic reticulum
surrounds the myofibrils
contains Ca2+
Ca2+ on troponin
binds troponin C
myosin
thick filaments
actin
thin filaments
Z line
where myosin filaments attach to via titin
also where actin filaments are directly attached
I band
just actin and titin
A band
overlap between actin and myosin filaments
H band
just the myosin filaments and the M line
M line
where the myosin filaments attach to
muscle organization (largest to smallest)
- skeletal muscles
- muscle fascicles
- muscle fibers
- myofibrils
- sarcomeres
- myofilaments
- actin and myosin
actin composition
actin consists of G actin and F actin
G actin
globular molecules that contain the active site for myosin
tropomyosin covers the active site and is held in place by troponin
troponin types
- I –> for heart attacks
- T –> non specific
- C –> what Ca2+ binds to
myosin head hydrolysis
ATP is hydrolyzed in the globular heads of myosin
hypocalcemia
when Ca2+ falls below 7 g/dL causing convulsions
specifically convulsions of the laryngeal muscles –> can’t breath
sliding filament theory (what shortens, lengthens, stays the same)
- H band and I band get smaller
- zone of overlap gets bigger
- sarcomeres get smaller
- A band remains constant
ACh esterase
breaks down ACh to relax the muscle
shwann cells
form myeline sheaths on the PNS
mitochondrion role in the NMJ
moves vesicles of ACh closer to the terminal end of the axon
muscle contraction
- NT release onto receptors
- depolarize sarcolemma
- SR releases Ca2+
- Ca2+ binds troponin
- tropomyosin roles revealing active site
- myosin binds
- ATP hydrolysis and release to cause pivot motion
- ATP binds myosin again to release them
motor units
- precise control –> less muscle innervation
- imprecise control –> more innervation
muscle tension
the level of contraction depends on the amount of motor units involved
this is because individual contractions are all or nothing so the combination of multiple fibers contracting to completion influences the level of contraction
muscle tone
muscle tension when relaxed
ex… standing up
muscle spindles
special cells monitored by sensory nerves to control muscle tone
hypertrophy
muscle enlargement due to increased exercise
- increase mitochondria number
- increase spindle activity
- increase glycolytic enzyme concentration
- increase glycogen reserves
- increase myofibril numbers
muscle atrophy
discontinued muscle use
hyperplasia
an increase in the number of cells NOT due to hypertrophy
ex… cancer
three major fiber types
- fast fibers
- intermediate fibers
- slow fibers
fast fibers
-white
-easily fatigued
-less mitochondria
-fast contractions
-large diameter
slow fibers
-red
-has more myoglobin
-more mitochondria
-NOT easily fatigued
-slow reactions
intermediate fibers
-pink
mix of fast and slow fiber characteristics
muscle classification (arrangement)
- parallel
- convergent
- pennate
-unipennate
-bipennate
-multipennate - circular
parallel fibers
fascicles are parallel to the longitudinal axis
ex.. biceps brachii and rectus abdominus
convergent fibers
all fibers meet at one point
ex.. pectoralis major
pennate fibers
form an oblique angle to the tendon
looks like a feather
unipennate
ex… extensor digitorum
bipennate
ex… rectus femoris
multipennate
ex… deltoid muscle
circular muscles
form concentric rings
ex… orbicularis oculi and orsi
origin and insertion
muscles are often named based on their points of origin and insertion
origin = muscle is stationary
insertion = muscle is movable
action
what the muscle does when contracted
- flexor
- extensor
- abductor
four types of primary action
- primer movers
- antagonists
- synergists
- fixators
prime movers
responsible for the main movement
ex… biceps brachii
antagonists
opposes the prime movers
ex… triceps brachii
synergists
help the prime movers
ex… latissmus dorsi and teres major
fixators
stabilization of a joint with the help of both prime movers and antagonists
ex… flexor and extensor muscles of the outstretched hand
levers and pulleys
lever = the force of a muscle contraction being exerted over a bone and pivoting at a fulcrum point, opposed by a force of gravity
pulleys = a tendon stretched over a bone that sets the origin of contraction far away from the site of action
first class lever
the fulcrum (J) sits between the applied force (AF) and the resistance force (RF)
ex… moving head up and down
second class
the resistance force (RF) sits between the applied force (AF) and the fulcrum (J)
ex… standing on your tip toes
third class
the applied force (AF) sits between the resistance force (RF) and the fulcrum (J)
ex… flexing the lower arm
pulley (lateral malleolus)
the fibularis longus contracts and pulls the foot down (plantar flexion) and can cause outward motion (eversion)
pulley (patella)
the quadriceps muscles contract causing extension of the leg
