Muscular Anatomy Flashcards
Properties of Muscle
What are some of the properties of skeletal muscle?
- Striations - skeleteal, cardiac muscle not smooth muscle
- multiple nuclei
- Voluntary - skeletal
- Individual cells will be long and cylindrical shaped
Muscle
muscle fibers -bundles of muscle fibers how we infer to myocytes
fascicles - bundle of individual muscle fibers
Connective Tissue in Muscle:
Endo Mysium: wrapping individual muscle fibers - loose connective tissue
Pari Mysium: wraps bundles of muscle fibers - combination of endo and epi
Epi Mysium: wraps the entire musclemy
All of these mysium end up being connected which is important to distributing force we generate when we contradict a muscle. If we didn’t we could tare the muscle in half.
All connective tissue feeds into the tendon, ligament attaches bone to bone, a tendon attaches muscle to bone. Dense regular connective tissue
Muscular Nerovascular Supply
Muscles have rich supply of blood vessels and nerves
- Uses a lot of oxygen and ATP
- Blood vessels and nerves enter/exit a muscle in the middle of its length
At what level would you classify an individual muscle (cellular -> organism) - every individual muscle is an organ
Cellular Anatomy of a Muscle Fiber
Multinucleate
- Plasma Membrane = Sarcolemma - another term in relation to muscle
- Full of myofibrils -
the muscle fiber it self is cytoplasm is filled with myofibrils and pushes the nuclei at the edge of the cell
By having the same dna in all different nuclei = making speicfic proteins that are needed within a muscle fiber, you can generate that mRNA from the DNA from all five of those different nuclei, make protein from all those different copies. Benefit speeding up process and efficiency
What organelles would you find in abundance within muscle fibers? Mitochondria for ATP
What kind of inclusion body do you think would be in abundance within muscle fibers?
-Gyclosomes - bundle of glycocen energy source (sugar molecules) doesn’t dissolve in water
T-tubules and Sacroplasmic Reticulum
Sarcoplasmic Reticulum (blue tubes) (Network)
- organelle throughout the muscle fiber and repository of calcium
Calcium critical for muscle contraction
T tubule - Have opening near the surface of the muscle fiber and travel deep down in the muscle fiber. During the muscle contraction there is a electrical signal that is generating just beneath the sarcolemma which is ultimately what causes calcium to be released from the sarcoplasmic reticulum. If the signal only stayed along the edges of the cells, just along the sacrolemma that would mean the calcium along the edges would get released, but calcium wouldn’t get release deep within the muscle fiber.
Extension of the sacrolemma tubes deep down within the muscle fiber that makes sure that electrical signal gets deep within the muscle fiber and causes calcium to be released within the depths of the muscle fibers.
What is myofibril
Bundles of protein known as actin and myosin (thicker filament).
When we contract a muscle these globular heads of the myosin attach to the actin. They swivel and pull actin towards the center “M line” causes the actin and myosin to slide together
each muscle fiber is full of myofibril each muscle as a whole has ton of muscle fibers in them
Giant muscle - full of fascicles which are bundles of muscle fibers and then within those individual muscle fibers we have tons and tons of myofibrils and within those myofibrils, we have tons and tons actin and myosin which what attach and allows are muscles to shorten during a contraction
So why are bigger muscles stronger?
Actin and myosin - they’re not generating new muscle fibers (no mitosis, no regeneration)
We see hypertrophy - overgrowth of muscle. individual muscle cells increasing their size bc they’re being filled with more mybrofibrils and we know that mybrobils means there’s more actin and myosin in there. Overall a stronger muscle,
Muscle Fibers types
3 different types of muscle fibers found within the body type 1 (slow oxiative) - slow twitch muscle in relation how quickly they can activate, small amount of force, fatigue resistance, lots of mitochondria type 2b (Fast Glycolytic) - Bigger, generate way more force and fast twitch and mysoin is able to grab onto actin swivel quickly, can't hold onto maximum muscle force very long, receive ATP by breaking down sugar molecules in glycolysis, Type 2a (Fast Oxidative) - somewhat fatigue resistance, but can hold muscle contraction for ten mins, some mitochondria and using oxygen to generate force
Muscle Fiber Types
All muscles contain a mixture of the three fibers types, but the ratios are different between muscles
What muscles do you think have more type I (slow oxidiative) muscle fibers? Type 2b (fast glycolytic) Type 2 a (fast oxiative?
- Slow oxidiative - eye lid muscle, posture muscles,
- Type 2 b (fast glycolytic) - Calf muscles, explosive movements
- Type 2a - most of our muscle fibers are sitting in the type 2 a
Think about athletic records held by males and females. Do you think there are any sex differences in the muscle fibers composition of males and females?
Ultra marathon - females have a higher composition of higher amount of slow oxidative muscle fibers
Do you think that training can alter our muscles fiber composition?
-We can switch type 2a & 2b but cannot switch from type 1 and type 2.
Muscle fibers across the lifespan
Muscle fibers number is determined prior to or shortly after birth
distribution (I vs IIa vs IIb) is complete by 1 year of age
Muscle mass peaks in women btwn 16-20 years and men 18-25
Muscle mass can begin to decline as early as 25 years of age
By about 30 years of age, strength declines 8-10% per decade
Strength and endurance decline less rapidly in physically active individuals
Pictures of muscle fibers
type 1 lighter
Type 2 stain dark
more connective and fat tissue in 67 y/o female
alot more type 1 fibers
with aging there is a prefertial loss of type 2 muscle fibers
Reduction in muscle fiber size and decreases strength
Increase of Adipose tissue and connective Tissue within our muscles
Changes in muscle with aging
Sacropenia: age-related, involuntary loss of muscle mass and strength
Do you think that sarcopenia is the only cause of decreased strength with aging?
No, but depends how active you are.
We can’t prevent sacropenia but we can slow it down
What causes muscles fibers to contract?
Where are the motor neuron cells bodies located?
Motor cortex send axons down through the spinal cord to synapse w/ motor neurons in the Ventral Horn of the spinal cord those neurons in the ventral horn of the spinal cord they send their axons out to innervate our muscles
Neuromuscular junctions with the muscle fiber, special name for the synapse.
Motor Units
A motor units consists of 1 motor neurons and all of the muscle fibers it innervates
motor units are variable in size
Why would you want some motor units to be large and others to be small?
About control - larger motor units in big muscles like Gluteus Maximus
Finger tips or eyelids muscle we want smaller motor units on point motions, less power
We can only do that if we control a few muscles fibers for each motor neuron.
