Muscles Flashcards
Muscle tissue is divided into:
skeletal
cardiac
smooth
Skeletal muscle is attached to:
the skeletal system and allows us to move
Structure of skeletal muscle
muscle fibers
connective fibers
nerves
blood vessels
Functions of skeletal muscle
produce skeletal movement
maintain body position
support soft tissues
guard body openings
maintain body temperatures
Muscles that are opposite of each other
antagonistic
muscles that cause the same action
synergists
Muscle fascicle
bundles of muscle fibers that are the basic building blocks of skeletal muscles
muscle fibers
fundamental unit of muscle tissue that contract to enable muscle movement. They are responsible for all voluntary movement and help control the physical forces within the body
Myofibrils
long contractile fibers, groups of which run parallel to each other
Thick myofiliments
protein complexes made up of hundreds of myosin molecules that are the primary component of muscle contraction
Thin myofiliments
protein strands that are made up of actin
Epimysium
exterior collagen layer connected to deep fascia and separates muscles from surrounding tissues
Perimysium
surrounds muscle fiber bundles (fascicles) and contain blood vessels and nerve supple to fascicles
Endomysium
surrounds individual muscle fibers and contain capillary and nerve fibers that contact muscle cells
also contains satellite cells that repair damage
Endomysium, perimysium, and epimysium come together at:
the ends of muscles to form connective tissue attachment to bone matrix
Tendon shape
like a bundle
Aponeurosis shape
flat like a sheet
Skeletal muscle cells are:
long
develop through fusion of mesodermal cells
contain hundreds of nuclei
Sarcolemma
the cell membrane of a muscle cell
surrounds the sarcoplasm
A change in transmembrane potential:
begins contractions
Transverse tubules (T tubules)
transmit action potential through cells and allow entire muscle fibers to contract simulateously
Sarcomeres
structural units of myofibrils that form strips or striated pattern
M line
the center of a band at midline of the sarcomere
I bands
light, thin filaments composed of actin
Z lines
the center of the I bands
H zone
area around the M line that has thick filaments but no thin filaments
Titin
strands of protein from tips of thick filaments to the Z line
Transverse tubules encircle the:
sarcomere near the zones of overlap
Ca2+ released by:
sarcoplasmic reticulum causes thick and thin filaments to interact
Sarcoplasmic reticulum
membranous structure surrounding each myofibril that help transmit action potential to myofibrils
hold onto calcium
Muscle contraction caused by:
free Ca2+ into the sarcoplasm and triggers contraction
What are the 4 filament proteins
F actin
Nebulin
Tropmyosin
troponin
F actin
2 twisted rows of globular G actin & the active sites on G actin strands that bind to myosin
Nebulin
holds F actin strands together
Tropomyosin
is double strand that prevents actin-myosin interaction
Troponin
a globular protein that binds tropomyosin ti G actin and is controlled by Ca2+
Myosin molecule is made up of:
a tail and head
Myosin tail
binds to other myosin molecules
Myosin head
made of 2 globular protein subunits and reaches the nearest thin filament
Sliding filament theory
a muscle fiber contracts when myosin filaments pull actin filaments closer together and thus shorten sarcomeres within a fiber
aka contraction
Level 1 (skeletal muscle)
skeletal muscle surrounded by epimysium and contains muscle fascicles
Level 2 (muscle fascicle)
muscle fascicle surrounded by perimysium and contains muscle fibers
Level 3 (muscle fiber)
muscle fiber surrounded by endomysium and contains myofibrils
Level 4 (myofibril)
myofibril surrounded by sarcoplasmic reticulum and consists of sarcomeres (z line to z line)
Level 5 (sarcomere)
sarcomere contains thick and think filaments
Neural stimulation of sarcolemma:
happens at neuromuscular junction and causes excitation-concentration coupling
excitation-concentration coupling
a series of events that links a muscle cell’s action potential to its contraction
Cisternae of SR release:
Ca2+ that triggers interaction of thick and thin filaments consuming ATP and producing tension
Action potential
a rapid change in the voltage across a cell membrane, which is a nerve signal that allows cells to communicate with each other
The synaptic terminal:
releases the neurotransmitter acetylcholine (ACh) into the synaptic cleft
Synaptic cleft
the gap between synaptic terminal and motor end plate
Acetylcholine or ACh travels:
across the synaptic cleft, binds to membrane receptors on sarcolemma and causes sodium-ion rush into sarcoplasm that is quickly broken down by acetylcholinesterase (AChE)
Action potential generated:
by increase in sodium ions in sarcolemma, travels along the T tubules and leads to excitation-contraction coupling
Excitation-contraction coupling requires:
myosin heads to be in a “cocked” position - or loaded by ATP energy
1st step of the contraction cycle
exposure of active sites of F actin of the thin filament
2nd step of the contraction cycle
formation of the cross-bridges due to interaction of actin filaments with myosin heads forming cross-bridges that pivot and produce motion
3rd step of the contraction cycle
the pivoting of myosin heads
4th step of the contraction cycle
detachment of the cross-bridges
5th step of the contraction cycle
reactivation of myosin
Contraction duration depends on:
duration of neural stimulus and number of free calcium ions in sarcoplasm availability of ATP
Relaxation happens when:
Ca2+ concentration falls
Ca2+ detaches from troponin
Active sites are recovered by tropomyosin
Sarcomeres remain contracted
Rigor mortis
a fixed muscular contraction after death that is caused when ion pumps cease to function and calci builds up in the sarcoplasm
Isotonic contraction
a muscle contraction that involves a change in muscle length while maintaining the same tension
Isometric contraction
a muscle contraction that occurs when a muscle generates force without changing its length
The heavier the resistance of a muscle:
the longer it takes for shortening to begin and the less the muscle will shorten
Muscle relaxation
after contraction a muscle returns to resting length by elastic forces, opposing muscle contractions, or gravity
Elastic forces (muscle relaxation)
the pull of elastic elements such as tendons or ligaments that expands the sarcomeres to resting length
Opposing muscle contractions (muscle relaxation)
reverse the direction of the original motion that work as opposing skeletal muscle pairs
ex biceps and triceps
Gravity (muscle relaxation)
can take place of opposing muscle contraction to return a muscle to its resting length
Sustained muscle contraction uses:
a lot of ATP energy
Adenosine triphosphate (ATP)
the active energy molecule
Creatine phosphate (CT)
the storage molecule for excess ATP energy in a resting muscle
What two ways do cells produce ATP?
aerobic metabolism and anaerobic glycolysis
Aerobic metabolism
primary energy source of resting muscle that breaks down fatty acids
Aerobic respiration occurs with oxygen and releases more energy but more slowly.
Aerobic metabolism produces how many ATP molecules per glucose molecule?
34 ATP
Anaerobic glycolysis
is the primary energy source for peak muscular activity that breaks down glucose from glycogen stored in skeletal muscle
Anaerobic glycolysis produces how many ATP molecules per glucose molecule?
2 ATP
Muscle fatigue
when muscles can no longer perform a required activity
What are the results of muscle fatigue?
depletion of metabolic reserves
damage to sarcolemma and SR
low pH due to lactic acid
muscle exhaustion and pain
Recovery period
the time required after exertion of muscles to return to normal
Cori cycle
the removal and recycling of lactic acid
The liver converts lactic acid to:
pyruvic acid
Fast fibers
contract quickly
have large diameter
large glycogen reserves
few mitochondria
strong contractions
fatigue quickly
ex: body builders
Slow fibers
slow to contract
slow to fatigue
have high oxygen supply
contain myoglobin
ex: long-distance runners
myoglobin
red pigment that binds to oxygen
intermediate fibers
mid-sized
low myoglobin
have more capillaries than fast fibers
slower to fatigue
Muscle hypertrophy
muscle growth from heavy training
Muscle atrophy
lack of muscle activity that reduces muscle size, tone, and power
Anaerobic endurance
use fast fibers, fatigue quickly with strenuous activity
ex: 50-meter dash or weight lifting
Aerobic endurance
prolonged activity that require more oxygen and nutrients
7 characteristics of cardiocytes
small
single nucleus
have short, wide t tubules
no triads
SR with no terminal cisternae
are aerobic
have intercalated disks
Intercalated discs
specialized contact points between cardiocytes
Intercalated discs link:
heart cells mechanically, chemically and electrically, the heart functions like a single, fused mass of cells
Cardiac tissue is controlled by what type of cells?
pacemaker cells through electricity
Smooth muscle is found in:
blood vessels
reproductive and glandular systems
digestive and urinary symptoms
integumentary system
8 characteristics of smooth muscle cells
long, slender, and spindle shaped
single, central nucleus
no T tubules, myofibrils or sarcomeres
have no tendons
have scattered myosin fibers
myosin fibers have more heads per thick filament
have thin filaments attached to dense bodies
Parallel muscle fibers
fibers parallel to the long axis of muscle
ex: biceps brachii
Parallel muscle contract __ %
30%
Convergent muscle fibers
broad area that converges on attachment site where muscle fibers pull in different directions
ex: pectroralis muscles
Pennate muscle fibers
muscle fibers that are arranged at an angle to the muscle’s line of action, similar to the way the bristles of a feather are arranged
ex: rectus femoris
Circular muscle fibers
open and close to guard entrances of the body
ex: sphincters
Fulcrum
fixed point
Applied force
the force exerted by a muscle when it contracts
Resistance
an external force or load that causes muscles to contract
First class levers
Resistance - fulcrum - applied force
ex: raising head OR seesaw
Second class levers
fulcrum - resistance - applied force
ex: wheelbarrow or calf raises
Third class levers
fulcrum - applied force - resistance
the most common lever in the body
ex: bicep curl
Muscle origin
the point where a muscle attaches to a bone that remains stationary during contraction
Muscle insertion
the point where a muscle attaches to a bone, tendon, or connective tissue that moves when the muscle contracts
Origin is usually ___ to insertion?
proximal
Agonist muscle
the primary muscle that contracts to move or rotate a bone at a joint. It’s also known as the prime mover
Antagonist muscle
a muscle that performs the opposite action of another muscle
Synergist muscle
smaller muscle that assists a larger agonist and helps start motion or stabilize origin of agonist
Rectus
straight
Transversus
across body
oblique
angle
Longus
long
longissimus
longest
teres
long and round
brevis
short
magnus
large
major
larger
maximus
largest
minor
small
minimus
smallest
