Chapter 10 - Muscular Tissue Flashcards
(3) types of muscular tissue
skeletal
cardiac
smooth
skeletal muscle
moves?
striated?
voluntary/involuntary?
moves bones
striated
works in voluntary manner but also controlled **subconsciously **
**Cardiac **Muscle
found where?
striated?
voluntary/involuntary action?
found **only **in walls of the heart
striated
involuntary
**Smooth **Muscle
located?
striated?
involuntary/voluntary action?
located in **walls of hollow internal structure **(blood vessels, airways & many organs)
lacks striations
usually involuntary
Functions of **Muscular Tissue **(4)
1) producing body movements
2) stabilizing body positions
3) moving substances within body
4) generating heat
Properties of Muscular Tissue (4)
1) electrical excitability
2) contractibility
3) extensibility (stretch)
4) Elasticity (can return to normal length)
Skeletal Muscle Tissue
connective tissue components
Fascia
Epimysium
Perimysium
Endomysium
Fascia
Dense sheet or broad band of irregular connective tissue that surrounds muscles
(3) layers of connective tissue extend from fascia to protect & strengthen skeletal muscle
1) Epimysium
2) Perimysium
3) Endomysium
1) Epimysium
The outermost layer of dense irregular connective tissue
circles entire muscle
2) Perimysium
Separates 10-100 muscle fibers into bundles called fascicles
3) Endomysium
penetrates interior of each fasicle & seperates individual muscle fibers from one another (mostly reticular fibers)
Tendon
cord that attached muscle to a bone
Aponeurosis
connective tissue elements extend as broad flat sheet
(broad flattened tendon)
Neurons that stimulate skeletal muscle to contract are ____________motor neurons
The axon of a somatic motor neuron typically ____________many times, with each ___ extending to a different skeletal muscle fiber
somatic
branches
branch
The ____________of skeletal muscle fibers is set before you are born
(most of these cells last a lifetime)
number
Muscle growth occurs by?
**muscular hypertrophy **- an enlargement of existing muscle fibers
What can stimulate hypertrophy?
**Testosterone **& **Human Growth Hormone **
what cells retain the capacity to regenerate damaged muscle fibers ?
satellite cells
The plasma membrane of a muscle cell
sarcolemma
Tiny invaginations of sarcolemma
Tunnel in from the plasma membrane
Muscle action potentials travel through
Transverse (T Tubules)
the cytoplasm of a muscle fiber
includes glycogen used for synthesis of ATP and a red-colored protein called ____ which binds oxygen molecules
Sarcoplasm
Myoglobin
**Myoglobin **& oxygen?
protein that binds oxygen and releases it when it is needed for ATP production
Thread like structures within the sarcoplasm which have a contractile function
myofibrils
membranous sacs which encircles each myofibril
Sarcoplasmic reticulum
dilated end sacs that butt against T-tubules from both sides
Stores calcium ions (Ca++)
& releases to trigger muscle contraction
terminal cisterns of
Sacoplasmic Reticulum
**(myo)filaments **
smaller protein structures within myofibrils that function in the contractile process
**thin **and thick
(2 **thin **for every thick)
compartments of arranged filaments
basic functional unit of a myofibril
Sarcomeres
(extend from one Z disc to another)
Narrow plate-shaped region of dense protein material
Separate one sarcomere from the next
Z discs
Thick and thin filaments overlap one another but the extent of overlap depends on?
whether muscle is contracted, relaxed or stretched
Darker middle part of sarcomere that extends entire length of thick filaments & includes parts of thin filaments that overlap thick filaments
A band
Zone of Overlap
toward each end of A band where thin & thick filaments lie side by side
lighter, less dense area of sarcomere that contains **thin **but no thick filaments
Z discs passes through center of each
I band
center of each A band which contains **thick **but no thin filaments
H zone
M line
supporting proteins that hold thick filaments together in H zone
Myofibrils are built from (3) kinds of proteins
1) contractile
2) regulatory
3) structural
Contractile proteins (2)
1) Myosin
2) Actin
Myosin
thick filaments
Functions as a motor protein (can achieve motion)
Convert ATP to energy of motion
Projections of each myosin molecule protrude outward (myosin head)
Actin
Thin filaments
**actin molecules **provide a site where a myosin head can attach
Myosin
head vs tail.
head - shaped like 2 golf clubs & protrude outward towards thin filaments
**tail - **point toward M line in center of sarcomere
Other parts of thin filaments other than actin
Tropomyosin and troponin are also part of the thin filament
In relaxed muscle
Myosin is blocked from binding to **actin. **Why?
How do can muscle contractions occur?
**WHY? - ** because trands of tropomyosin cover the myosin-binding sites (held in place by troponin)
Calcium ion binding to troponin moves tropomyosin away from myosin- binding sites
Allows muscle contraction to begin as myosin binds to actin
Structural Proteins (2)
1) Titin
2) Dystrophin
1) Titin
stabilize position of myosin
accounts for much of the elasticity & extensibilituy of myofibrils
2) Dystrophin
links thin filaments to sarcolemma
Sliding Filament Mechanism
myosin heads attach to and “walk” along thin filaments at both ends of sarcomere
**pulling thin filaments toward center of sarcomere **
Z discs come closer together & sarcomere shortens leading to shortening of entire muscle
** Length–Tension Relationship **
___ of muscle contraction depends on __ of ___
forcefulness of muscle contraction depends on length of sarcomeres
When muscle fiber is stretched,
what happens to **overlap **and **tension (forcefulness) **?
LESS overlap between thick & thin filaments
tension is diminished
When a muscle fiber is shortened,
what happens to filaments and tension?
filaments are compressed (thick filaments crumple as they are compressed against Z discs)
fewer myosin heads make contact with thin filaments
**tension **is diminished
Neuromuscular Junction
synapse between a somatic motor neuron & a skeletal muscle fiber
Where communication occurs between a somatic motor neuron and a muscle fiber
synapse
Gap that separates the two cells
synaptic cleft
Chemical released by the initial cell communicating with the second cell
neurotransmitters
sacs suspended within the synaptic end bulb containing molecules of the neurotransmitter ______
Synaptic Vesicles
contain** acetylcholine (Ach) **
The region of the muscle cell membrane opposite the synaptic end bulbs that contains Acetylcholine receptors
Motor End Plate
The tension or force of muscle cell contraction varies and is dependant on (4)
1) The rate at which nerve impulses arrive (impulses/sec) - frequency of stimulation
2) The amount of stretch before contraction
3) The nutrient and oxygen availability
4) The size of the **motor unit **
Motor Units consists of a __ ___ and the __ __ it stimulates
motor neuron
muscle fibers
The axon of a motor neuron branches out forming __ ___ with different muscular fibers (about 150)
neuromuscular junctions
Control of precise movements consist of **many small motor units **
How many muscle fibers per motor unit for:
1) voice production muscles
2) muscle controlling eye movement
3) muscles in arm & leg
1) 2-3
2) 10-20
3) 2000-3000
The total ____________of a contraction depends on the size of the motor units and the **number that are activated **
strength
A small amount of ____________in the muscle due to weak contractions of motor units
Small groups of motor units are alternatively active and inactive in a constantly shifting pattern to sustain muscle ____________ to keep skeletal muscle firm
tautness (tension)
tone
(2) types of contractions
1) isotonic
2) isometric
**Isotonic **Contraction
tension developed remains constant while the muscle changes its length
Used for body movements and for moving objects
*ie. Picking a book up off a table *
Isometric Contraction
The tension generated is not enough for the object to be moved and the muscle does not change its length
tension **increases **without a change in muscle length
Holding a book steady using an outstretched arm
(2) types of isotonic contraction
1) concentric
2) eccentric
**concentric **isotonic contraction
tension generated is great enough to overcome resistance of object to be moved, muscle **shortens **& pulls on another structure to produce movement & to reduce angle at a joint
**eccentric **muscle contraction
length of muscle **increases **
Muscle fibers vary in their content of ___
**myoglobin **- red-coloured protein that binds oxygen in muscle fibers
Red Muscle Fibers
skeletal muscle fibers that have a **high myoglobin content **
- appear darker (dark meat in chicken legs & thighs)
contain **more mitochondria **
supplied by more blood capillaries
White Muscles Fibers
Have a low myoglobin content
Appear lighter (white meat in chicken breasts)
Muscle fibers contract at different speeds, and vary in how quickly they fatigue.
Muscle fibers are classified into (3) main types based on structural & functional characteristics.
1) Slow oxidative (SO) fibers
2) **Fast oxidative-glycolytic (FOG) **fibers
3) Fast glycolytic **(FG) **fibers
1) Slow oxidative (SO) fibers
diameter size?
power?
appearance?
generate ATP by?
speed of contraction?
time until fatigue?
for what activities?
smallest
least powerful
dark red (more myoglobin)
mainly aerobic cellular respiration
slow contraction speed (last 100-200 msec)
very resistant to fatigue
capable of prolonged, sustained contractions for many hours
adapted for **maintaining posture, aerobic, endurance-type **activities (running marathons)
2) Fast oxidative-glycolytic (FOG) fibers
diameter?
contains? appearance?
generates ATP by?
resistance to fatigue?
speed of contraction?
contribute to which activities?
**intermediate **diameter size
lots of myoglobin & many **blood capillaries **
**aerobic cellular respiration **but also anaerobic glycolysis
moderately high resistance to fatigue
**faster **contraction speed ( < 100 msec)
walking & sprinting
3)** Fast glycolytic (FG) **fibers
diameter?
strength?
contains? appearance?
generates ATP by?
resistance to fatigue?
adapted for?
**largest **
most powerful contractions
low **myoglobin, fewbloodcapillaries&mitochondria**
white in colour
mainly by **glycolysis **
fibers contract strongly & quickly
fatigue quickly
intense anaerobic movements of short duration (weight lifting)
Most muscles are a mixture of all 3 types of muscle fibers
Proportions vary, depending on ….(3)
1) action of the muscle
2) the person ’s training regimen
3) genetic factors
Postural muscles of the neck, back, and legs have a high proportion of ____________fibers
slow-oxidative (SO)
Muscles of the shoulders and arms have a high proportion of ____________fibers
**Fast-Glycolytic (FG) **