A&P: Muscular System Flashcards
List the 5 functions of the Muscular System
MMMSG
- Movement
- Maintain posture/body position
- Maintain body temp
- Support soft tissue
- Guard entrances and exits (ex: Sphincters)
Cardiac muscle is composed of ______ cells called ______ that are joined together by _______ ________
individual
cardiomyocytes
intercalated disks
What is the main function of intercalated disks in cardiac muscle?
they are gap junctions which allow electrical impulses to travel to each cariomyocyte in order to contract in sync
List 3 types of muscle
Skeletal Muscle
Cardiac Muscle
Smooth Muscle
Explain why cardiac muscle cells, unlike skeletal muscle cells, do not get fatigued
Cardiac muscle cells have more mitochondria compared to skeletal muscle cells, so they rely exclusivley on aerobic respiration to generate energy (aerobic respiration = LOTS ATP MADE)
Compare the 3 muscle types: Skeletal, Cardiac, and Smooth muscle
Include: Cell/Fiber Shape, Number of nuclei, Presence of Striations, Control)
Skeletal Muscle:
Cell/Fiber Shape
- Tubular
Number of nuclei
- Multinucleated
Presence of Striations
- Striated
Control
- Voluntary
Cardiac Muscle:
Cell/Fiber Shape
- Branches
Number of nuclei
- Uninucleated
Presence of Striations
- Striated (intercalated disks)
Control
- Involuntary
Smooth Muscle:
Cell/Fiber Shape
- Spindle-shaped
Number of nuclei
- Uninucleated
Presence of Striations
- Non-striated
Control
- Involuntary
List the skeletal muscle organization from largest to smallest. Include which structures are covered by what type of fascia.
-
Skeletal Muscle (Epimysium)
-> Muscle Fascicle (Perimysium)
-» Muscle fiber/cell (Endomysium)
-»> Myofibrils
-»» Myofilaments - arranged into Sarcomeres
-»»> Actin (thin filament)
-»»> Myosin (thick filament)
What type of fascia ties adjacent muscle fibers together?
Endomysium
At the end of each muscle, the _____ fibers of all three layers come together to form a bundle called a ______
collagen
tendon
Tendons are bands of ____ fibers that attach muscle to the _____ of bone
collagen
periosteum
What is defined at the cell membrane of a muscle fiber?
sarcolemma
What is defined at the cytoplasms of a muscle fiber?
sarcoplasma
What is the sarcoplasmic reticulum?
It is the ER of a muscle fiber that stores Calcium during relaxation (also releases Calcium into sarcoplasma when stimulated by an AP)
What is the structural and functional unit of skeletal muscle?
sarcomere
What two proteins make up the sarcomere?
actin
myosin
What do a narrow network of tubules, T-tubules, allow for?
T-tubules allow for an AP to move through the skeletal muscle cell/fiber
How does the distance between Z lines change during muscle contraction?
Distance between Z lines/disks are reduced
Does the H zone change during muscle contraction? If yes, how so?
Yes, H zone consists of 100% myosin, so when actin gets pulled towards the M line, there is more overlap between myosin and actin. Therefore, the H band will shorten.
Does the A band change during muscle contraction? If yes, how so?
No, the A band measures the entire length of mysoin. When muscle contracts, the length of the sarcomere will shorten BUT the length of the filaments (actin and myosin) do NOT change. Therefore, the A band remains the same length during muscle contraction.
Be able to draw a complete sarcomere with appropriate disks/bands. Label each disk/band
check answer in Muscular System notes
Know what each of these bands measure/fxn:
M line
H band
A band
I Band
Z disks
- M line: anchors down myosin
- H band: measures 100% myosin; NO overlap
- A band: measures entire length of myosin; varying overlap with actin
- I band: measures 100% actin; bisected by Z disks
- Z disks: bisects I band
What is the region where the end of a neuron meets a muscle fiber
neuromusclular junction
Which neurotransmitter triggers contraction?
Acetylcholine (ACh)
The permeability of ____ ions on the muscles surface at the NMJ changes when ACh is released into the synapse.
Sodium (Na+)
Explain how a muscle contraction occurs. If it helps, draw it out. Include information about the sliding filament theory.
1) AP reaches axon terminal of motor neuron
2) ACh released into NMJ
3) ACh binds to receptor on sarcolemma of skeletal muscle cell
4) Na+ diffuses into skeletal muscle cell -> more Na+ diffuses in = skeletal muscle cell AP STARTS
5) AP travels along sarcolemma down to the T tubules
6) AP activated receptors on T tubules and extracellular Ca2+ diffuses in -> intracellular Ca2+ increases
7) Coupled receptor on SR membrane stimulated to release Ca2+
8) Ca2+ diffuses out of SR and into sarcoplasma (process known as Ca2+ induced Ca2+ released mechanism)
9) Ca2+ that was released from the SR (intracellular) will bind to troponin and initiates contraction (sliding filament theory)
CA2+ USED FOR CONTRACTION COMES FROM SR NOT EXTRACELLULARLY
10) Ca2+ binds to troponin (which sits on top of tropomyosin)
11) Triggers shift in position of tropomyosin to expose myosin binding sites on actin
12) ADP + Pi = will attach to actin -> Pi falls off from myosin head = power stroke = muscle contraction
What enzyme will be present in the NMJ when a signal from a motor neuron ends? (Hint: What would stop a muscle contraction)
Acetylcholinesterase, so that it can degrade/break down ACh in the synapse to stop muscle contraction
Define a motor unit
all of the muscle fiber controlled by a single motor neuron
Describe the relationship between the size of a motor neuron and control of movement
If a motor neuron controls a SMALL amount of muscle fibers = precise movement
Ex: eye movement
If a motor neuron control a LARGE amount of muscle fibers = movement does not need to be as precise
Ex: leg muscles
Define muscle tone
resting tension of skeletal muscle (contractions dont cause enough for movement)
Define: Atrophy
Decrease in muscles mass, size, and strength that occurs when they arent used
What are isotonic contractions?
Muscular contraction that changes muscle length
What are the two types of isotonic contractions? How do they differ? Include example
Concentric: contraction that shortens a muscle (Ex: lifting object off the desk/bicep curl)
Eccentric: contration where the muscle length increases (Ex: lower bicep curl)
What is isometric contraction?
Include example
Muscle tension increases by the muscle does not change length
(Ex: Plank)
What type of contraction is important for maintaining posture, standing, sitting?
Isometric contraction
Compare and Contrast the differece between fast fibers and slow fibers. Include: Time for contraction, number of mitrochondria, endurance.
Fast Fibers
Time For Contraction:
- Contract VERY quickly
Number of Mitochondria
- Fewer mitochondria
Endurance:
- Fatigue
Slow Fibers
Time For Contraction:
- Contract VERY slowly
Number of Mitochondria
- More mitochondria
Endurance:
- DO NOT fatigue
Compare origin from insertion
Origin = attachment site that does NOT move during contraction
Insertion = attachment site that moves during contraction
Define: Agonist (Prime Mover)
Include example
muscle whose contraction is mainly responsible for producing a particular movement
Ex: biceps are agonist during a bicep curl
Define: Antagonist
Include example
muscle whose action oppose the movement produced by another muscle
Ex: triceps are antagonist to the bicep during a bicep curl
Define: Synergist
Include example
a muscle that contract to help the prime mover
Ex: brachialis during bicep curl
Define: Fixator
Include example
synergist that stabilize the origin of a prime mover by preventing the movement of another joint
ex: shoulder muscles stabalize the shoulder joint during a bicep curl
Be able to label the most important muscles on a diagram. Refer to notes
For answers, refer to Muscular System notes
What are the three processes that muscles use to obtain energy?
aerobic CR
anaeorbic CR
Creatine phosphate breakdown
Describe: Aerobic CR.
Include: What is broken down, What is produced, What is required, Where in the cell does it take place/end?
- Glucose is broken down into LOTS of ATP
- Process requires Oxygen and produces CO2 and Water
- Begins in cytoplasm and ends in mitochondria
Describe: Anaerobic CR.
Include: What is broken down, What is produced, Where in the cell does it take place/end?
- Glucose is broken down in few ATP (AKA glycolysis) and byproduct include lactic acid
- Glucose is broken down in the cytoplasm
- Oxygen is NOT used
glc -> lactic acid + ATP (few)
What causes muscle pain when exercising?
When the body moves to anaerobic CR for energy, it produces lactic acid as a by product. This increase in lactic acid causes muscle pain.
How does Creatine Phosphate relate to the muscular system?
It generates ATP by donating Phosphate group (from Creatine Phosphate) to ADP to form ATP
