HMS: Muscular System Flashcards
Muscular System
Links the Nervous System & Skeletal System, and is responsible to generate the forces that move the human body.
Skeletal Muscle duties
Produce movement thru contraction
Stabilize the body
Assist w/ homeostasis by maintaining body heat.
Muscle Anatomy: Fascia
First layer of connective tissue that surrounds skeletal muscle and connects them to other muscles.
Muscle Anatomy: Epimysium
The layer of fascia that directly surrounds an entire muscle. Also called “deep fascia”
Muscle Anatomy: Fasicles
The largest bundles of fibers within a muscle.
Muscle Anatomy: Perimysium
The connective tissue that wraps each individual fascicle.
Muscle Anatomy: Endomysium
Each individual muscle fibers (myofibril) within a fascicle is wrapped by endomysium.
Muscle Anatomy: Sarcolemma
The plasma membrane that encases individual muscle fibers (myofibrils) w/i a fascicle.
Muscle Anatomy: Myofibrils
Each individual muscle fiber is made of cylindrical myofibrils, which is composed of overlapping myofilaments.
Muscle Anatomy: Cellular components
Sarcoplasm containing:
Glycogen (stored glucose)
Myoglobin (molecule that carries O2)
Mitochondria (powerhouse)
Muscle Anatomy: Myofilaments
The contractile components of muscle tissue, composed of:
Actin: Thin, stringlike filament
Myosin: Thick filament
Muscle Anatomy: Sarcomere
The functional unit of muscle system where muscle contraction occurs. A section of repeating Actin & Myosin.
Muscle Anatomy: Z-line
The ends of a each single sarcomere, where the next sarcomere meets.
Muscle Anatomy: Sketch a Sarcomere
Include:
Actin
Myosin
Z-line
Muscle Anatomy: Sketch a Myofibril
Include overlapping myofilament
Muscle Anatomy: Flowchart
Fascia: Surrounds & connects muscle sys
Muscle: Bundle of fascicles surrounded by deep fascia EPIMYSIUM connectv. tiss
Fascicle: Bundle of muscle fibers surrounded by PERIMYSIUM connect tiss
Muscle Fiber: Bundle of myofibrils surrounded by ENDOMYSIUM conect tis
Myofibril: A cylindrical shape of repeating Sarcomeres containing the Myofilaments, Actin & Myosin.
Muscle Anatomy: Tropomyosin
A protein structure located on the Actin filament that is responsible for myosin-binding sites along the Actin filament to prevent muscle contraction when muscle is in a relaxed state.
Muscle Anatomy: Troponin
A protein structure located on the Actin filament that provides binding site for tropomysin and calcium when a muscle needs to contract.
Neural Activation
The communication link between the Nervous System and the Muscular System.
Neuromuscular Junction
The communication site between Nervous & Muscular Systems. It is a synapse between the motor neuron and the muscle cell.
Motor Unit
One motor neuron and the muscle cell it innervates with.
Action Potential
A nerve impulse from the CNS that travels thru the PNS and across the neuromuscular junction into the muscle.
Neurotransmitter
Chemical messengers that cross the synapse between neuron & muscle and assist w/ nerve transmission. They are a translation of the nervous system’s electrical impulse that muscle cells can understand & act on.
Acetylcholine (ACh)
A neurotransmitter that helps the action potential cross the synapse into the muscle, which initiates the steps in muscle contraction.
Sliding Filament Theory
The act of the myofilaments Actin & Myosin sliding past one another to produce a muscle contraction, shortening the entire length of the sarcomere.
Excitation-Contraction Coupling: definition & flowchart
The steps in muscle contraction:
An Action Potential is released by CNS
The AP travels down the motor neuron, which is facilitated by sodium & potassium electrolytes, to the NM junct.
Acetylcholine (ACh) is released into the NM junction, which helps the AP cross the synapse into the muscle.
The AP travels into the muscle infrastr. stimulating the Sarcoplasmic Reticulum to release the electrolyte calcium.
Calcium is then released into the muscle, stimulating a chain of events resulting in Myosin heads binding to Actin.
The Myosin heads pull the Actin closer to the Sarcomere center, which slides the overlapping filaments past eachother, thus shortening the entire Sarcomere, known as the Power Stroke.
Power Stroke
Contraction of the muscles, in the myofilament Myosin uses ATP to bond with Actin.
Type 1 Muscle
Small motor units that innervate small muscle fibers and are fatigue resistant. Comprised of smaller muscles used to stabilize the body in slow long term contractions.
Able to do this b/c:
More mitochondria, capillaries & myoglobin. Increased o2 delivery.
Known as “red fibers” b/c o2.
Type 2 Muscles
Large motor units that innervate large muscle fibers and fatigue more quickly. They generate force quicker than Type 1. Comprised of larger muscles responsible for moving the body. Fast Twitch.
Fatigues quick due to less mitochondria, myoglobin & capillaries. “White fibers”
All or Nothing Principle
Motor units cannot vary the amount of force they generate; they either contract maximally or not at all. Hence, the overall strength of a muscle contraction will depend on the motor unit being recruited (whether the motor unit is small or large & the overall number of motor units that are activated at a given time).
Characteristics of muscles involved in fine motor skills vs. those involved in large powerful movements.
Fine motor skills: Each motor unit is assigned fewer muscle fibers to control.
Gross motor power: Each motor unit is assigned a larger amount of muscle fibers to control.
Type 2a & Type 2x
Type 2x: Truly “fast twitch” Fatigues quickest of all due to low oxidative capacity.
Type 2a: Fatigues less faster than Type 2x but still not as resistant as Type 1. Therefore, known as “Intermediate fast-twitch fiber”
Muscle Fiber Hierarchy
Type I: Most fatigue resistant b/c more energy related cellular organelles.
Type 2: Less resistant due to fewer energy related cellular organelles.
Separated into Type 2a & 2x. Since 2x fibers are the least fatigue resistant of all the fibers, 2a is described as “intermediate fast-twitch”
Muscle System life course
Peaks between 20 to 30 years old.
Stable from 30 to 50.
After age 50, mass is lost 1-2% per year. Strength is lost 1.5 to 5% per year.
Muscle Anatomy Chart
TBD
