Muscular system Flashcards
about how many muscles are there in the human body?
~650
what are myocytes?
-muscle cells/fibers that are primarily used for contraction
about how much of the body’s mass is myocytes?
~33%
Cardiac muscle
-makes up the myocardial walls
-striated
-has an intercalated disc network in the myocardium
purpose of the intercalated disc network
allows the fibers in the myocardium to collectively contract as a functional syncytium.
Each cardiac muscle fiber has….
Each fiber contains
-1 or 2 centralized nuclei,
-sarcoplasmic reticulum and transverse tubule network,
-an extensive number of mitochondria
where is smooth muscle found?
the walls of body parts such as the bronchial airways, stomach, alimentary canal, and blood vessels
what is the function of smooth muscle?
responsible for events such as the movement of food through digestive organs, emptying the bladder and bowel, and controlling the diameter of the blood vessel
smooth muscle is innervated by the ___________
autonomic nervous system
smooth muscle
-not striated
-involuntary
-contracts slowly in a wave-like manner
-have a less abundant blood supply, yet smooth muscle generates its metabolic energy needs primarily through oxidative pathways.
smooth muscle contains
-one centralized nucleus per fiber,
-no transverse tubules,
-a poorly developed sarcoplasmic reticulum network,
-contains more mitochondria than skeletal muscle cells.
function of skeletal muscle
-attach to bones and are responsible for the movement of bony levers
-produce more subtle movements such as facial expressions.
-controls posture, joint stability, and heat production.
85% of the heat produced in the body results from _____________
muscle contraction
features of skeletal muscle
-striated appearance
-prominent fascicles,
-contracts voluntarily
-Each muscle fiber contains many peripheral nuclei.
- fibers contain a robust sarcoplasmic reticulum and transverse tubular network
-with a moderately vascular supply.
-able to contract quick and forcefully.
what is skeletal muscle innervated by?
the somatic nervous system
A muscle’s origin (proximal) is typically ___________ to its insertion
superior
function of the muscle origin
serves as the foundation or base of bony attachment where the muscles contracts and pulls from to produce movement at the joint.
muscle insertion (distal)
-the point of bony attachment of the muscle
- where the movement at the joint will occur.
The bicep contracts and pulls from its __________ to cause flexion of the elbow at its _________.
-origin, insertion
what are the types of muscle?
-parallel
-convergent
-pennate
-fusiform
-spiral
-circular
Parallel Muscle
- arranged with the fascicles directed towards the long axis of the muscle
-comprise the majority of skeletal muscles in the body
-ex: sartorius
When muscle fibers are arranged _________ to the line of pull, the range of movement is more but the contraction force is _______
-parallel, less
Convergent Muscle
-also known as triangular
-muscles are where the origin (the attachment to a fixed bone, usually the proximal attachment) is wider than the point of insertion.
-allows for maximum force production
-ex: pectoralis major
Fusiform muscle
-have fibers within the muscle bellow that are arranged parallel to one another
-ex: biceps brachii
Spiral muscle
-the muscle fibers are twisted in arrangement close to their insertion
-ex: latissimus dorsi
Circular muscle
-have their fibers arranged in a circular fashion and, when contracted, will close the opening they regulate
-ex: orbicularis oris and oculi
-responsible for closing the mouth and eye
Pennate muscle
- have fibers oriented at an angle to the muscle’s line of pull and rotate as they shorten.
-there is uni-, bi-, and multi-
Ex: rectus femoris and deltoid
Rotating shortening creates a more oblique angle such that the fraction of force directed along the muscle’s line of pull ___________ throughout its contraction.
decreases
The ________ amount of pennation results in a ________ capacity for force production.
greater, greater
uni-pennate muscle
-has muscle fibers arranged on one side of the tendon
-ex: extensor digitorum longus
bi-pennate muscle
-has fibers on two sides of a tendon
-ex: rectus femoris
multi-pennate muscle
-has its fascicles arranged in a feather-like arrangement
-deltoid
the greater amount of _________ reduced the extent of muscle damage imposed by forced-lengthening (eccentric) contractions
pennation
why do the deltoids get less sore than the pectoralis major?
The deltoid is a multi-pennated muscle, while the pectoralis major is a convergent muscle. More pennation = less muscle damage from eccentric contractions
Each muscle is surrounded by fibrous connective tissue called ____________
deep fascia
what covers the deep fascia?
a less dense superficial fascia and adipose tissue
What’s underneath the deep fascia?
-the epimysium
epimysium
another layer of less dense connective tissue surrounding the muscle
Within the epimysium, the muscle is composed of a number of ___________
fascicles
fascicles
- bundles of muscle fibers
Each fascicle is surrounded by the _____________
perimysium
perimysium
a layer of connective tissue
Underneath the endomysium, each fiber is covered with a basement membrane or _________ and underneath this layer resides the _________
-basal lamina
-sarcolemma
sarcolemma
-the cell membrane under the basal lamina
Within each muscle fiber is contained a number of __________ and within each __________ resides a number of __________
- Myofibrils
- myofibril
- myofilaments
What are the two different myofilaments?
-myosin
-troponin
Thick filament myofilament
a thick filament composed of the hexameric contractile protein, myosin, which consists of two myosin heavy chain (MHC) and four myosin light chains (MLC).
what does the hexameric protein consist of?
-2 mysoin heavy chain (MHC)
-4 myosin light chains (MLS)
thin filament myofilament
the thin filament composed of the contractile protein actin and the regulatory proteins, troponin, and tropomyosin.
function of troponin
-operates as a trimer, consisting of the three sub-unit proteins known as Troponin C, Troponin I, and Troponin T.
The myofibrils are aligned sequentially with ______________
-sarcomeres
sarcomeres
-intervening units that myofilaments reside in
-the contractile unit of the muscle
how is muscle plasticity governed?
-it is governed by the phenotype of the muscle which allows it to transition in its metabolic and functional capacity
What determines a muscle’s phenotype?
-by the diversity of muscle fibers that it contains
what makes phenotypes different?
-differences in structural, metabolic, and functional characteristics of the muscle fibers
What are the different muscle fiber types?
-slow-twitch (type I, slow-oxidative)
-fast-twitch (type II)
Fibers that are type II are either type IIa (_____________) or type IIx (______________)
-fast-oxidative-glycolytic
-fast-glycolytic
a muscle fiber’s functional and structural capability is contingent on its _________________
-metabolic capacity
Which muscle fiber types are large?
fast-twitch type IIA and fast twitch type IIX
which fiber type has the largest force production
fast twitch type IIX
which fiber type is the quickest to fatigue?
fast twitch type IIX
which fiber type is the slowest to contract?
slow twitch type I
which fiber type has the most mitochondria?
slow twitch type I
Which fiber has a moderate amount of capillaries?
fast twitch type IIA
which fiber type has the most myoglobin? the least?
most - slow twitch type I
least - fast twitch IIX
which fiber type has the lowest ATPase level?
slow twitch type I
Which fiber type has the lowest oxidative capacity?
fast twitch IIX
myoglobin
oxygen carrier within the muscle fiber
Type I muscle fiber
contain:
- high amount of myoglobin and mitochondria
-high oxidative enzyme activity, and triglyceride storage
-high capillary density
-
The ability for the type I fiber to primarily rely on _____________ metabolically makes it effective at endurance types of exercise
oxidative metabolism
why does type I muscle fiber have a slower contraction speed, lower ability to produce force, and lower hypertrophy potential?
-because it is innervated by alpha-2 motor neurons
Type IIx fibers are highly __________ due their sparse amount of mitochondria and oxidative enzymes.
anaerobic
How do type IIx fibers get energy?
they contain a high amount of creatine phosphate, creatine kinase, myosin ATPase, and glycolytic enzyme activity
-high amount of glycogen storage
pros and cons of type IIX fibers
pros:
-very fast contracting
-high amount of force production
-large potential for hypertrophy
cons:
-fatigues quickly
Why are type IIa fibers referred to as intermediate fibers?
because they possess metabolic and functional capacities that place them between those of type I and type IIx fibers.
Why are type IIa fibers considered oxidative-glycolytic fibers?
-they possess a higher amount of mitochondria and oxidative enzymes than type IIx, but less than type I
-possess a high amount of anaerobic and glycolytic enzymes, but less than type IIx.
Can I change my muscle fiber type to more fast-twitch with training so they are more suitable for bodybuilding?
-With the type of resistance training that physique athletes utilize, there can by some slow to fast transition in phenotype meaning a relatively small number of slow-twitch fibers can transition metabolically and functionally to fast twitch fibers. this won’t be significant though
What happens to type IIa muscle fibers during endurance training?
-when large amounts of endurance training is done, the type IIa fibers will be recruited
-Over time, the type IIa fibers will undergo increases in their oxidative metabolic capacities and begin to behave metabolically and functionally like type I fibers
slow to fast phenotype transition
-when someone is doing more anaerobic-type training program such as sprinting which will recruit mostly type IIx and some of type IIa fibers,
-over time with this type of training the type IIa fibers can adapt and undergo increases in their anaerobic capacity so that metabolically and functionally, they begin to behave as type IIx fibers.
motor unit
An alpha motor neuron and all the muscle fibers it innervates
why does the maximum force development and rate of force production increase after strength training?
increased recruitment gain in the spinal motor neuron pool
If an alpha motor neuron innervates 25 muscle fibers in a muscle when this nerve is activated, then all 25 of these fibers will _______________
contract
Sprinting will generate the recruitment of mainly _________ motor units
type II
endurance running will recruit mainly ______________ motor units
type I
what motor units does heavy lifting primarily recruit?
-mostly type IIa since the contraction velocity is not rapid and explosive,
What controls the intensity or magnitude of the muscular force to be generated?
It is controlled by the voluntarily evoked neurological signal generated within the primary motor area
-this affect the number of motor units recruited to overcome external resistance and produce movement of the joint.
The amount of force a muscle produces during a voluntary contraction is directly contingent upon what?
upon the number of motor units that are activated and the rates at which these motor units discharge action potentials to produce muscle fiber contraction.
The process of motor unit recruitment is
the governing process for the gradation of muscular force generation.
