Chapter 9- Muscles Flashcards
the scientific study of muscles is known as what?
myology
muscular tissue amount for approx. ___% of total body mass
45
What are 5 functions of muscles?
maintain posture and body position movement heat production guard orifices support visceral organs
What are the 4 properties of muscle tissue? describe them briefly
Excitability: ability to receive and respond to electrical or chemical stimuli
Contractility: ability to shorten forcibly when stimulated
Extensibility: ability to be stretched without damaging the tissue
Elasticity: ability to return to original shape after being stretched
Are muscles organs?
yes
what are some tissue types found in muscles?
connective tissue arteries/veins nerves lymphatics contractile muscle cells
Where do skeletal muscles attached?
attach to bone, skin, or fascia
What are some characteristics of skeletal muscle? (6)
- striated with light and dark bands
- voluntary control
- long, thin and multi-nucleated fibers
- arranged into packages that attach to and cover the bony skeleton
- contracts rapidly, but tire easily
- may exert great force
1 muscle fiber is equal to______
1 muscle cell
What is the main portion of the muscle called?
Belly (Gaster)
what is the Belly of the muscle attached to?
Then what is this attached to?
tendons; tendons are attached to bone
What is the deep fascia made of and what does it do?
made up of dense irregular CT around the muscle
holds it in place and separates it from other muscle
What is the subcutaneous fascia made up of and where is it located?
Loose CT beneath skin, surrounds several muscles
many muscle fibers are bundled together into groups called______
fascicles
fascicles can have anywhere from _____-_____ muscle cells (fibers)
10-100
several _______ make up a muscle
fascicles
What are the three parts of skeletal muscle CT? briefly describe them
Epimysium: surrounds the whole muscle
Perimysium: surrounds fascicles
Endomysium: separates individual muscle fibers (cells)
All CT extend beyond the muscle belly to form the_____
tendon
tendons may form thick flattened sheets called what?
aponeuroses
what are myoblasts?
embryonic cells that fuse to form muscle fibers
*this is why they are so long and multinucleate
Myoblasts that do not fuse become__________ cells. what do these cells do?
myosatellite cells
they assist in the repair of damaged cells
for the fiber structure of skeletal muscle, what is the name for the fiber cytoplasm?
sarcoplasm
for the fiber structure of skeletal muscle, what is the name for the plasma membrane of a fiber?
sarcolemma
what are transverse (T) tubules?
extensions of the sarcolemma into the sarcoplasm
What are myofibrils?
what do they do?
contractile organelles
they extend the length of fiber
what surrounds myofibrils?
what does it contain?
sarcoplasmic reticulum
contains calcium ions
*similar to ER
the functional unit of a myofibril is a …..
sarcomere
Sarcomeres are made up of______ and _____ filaments
thick and thin
the thick filament of sarcomeres is made up of what? describe it
Myosin
- twisted protein with globular heads
- 1.6 mu m long
- 500/thick filament
the thin filament of sarcomeres is made up of what? describe it
Actin -structural protein -coiled "beads" Regulatory Proteins -allow/prohibit attachment between actin and myosin -Tropomyosin -Troponin
Describe sarcomere ‘bands’ and the different types
Sarcomere ‘bands’ cause the striated appearance
A: entire thick filament range
I: only thin filaments
H: only thick filaments
Zone of overlap: both filaments
Describe sarcomere ‘lines’ and the different types
Divide and flank the sarcomere
Z: -the end of the sarcomere -made of actinin protein -anchor thin filaments M: -middle of the sarcomere -stabilize thick filaments
What are 3 structural proteins of sarcomeres? describe them
Titin: anchors a thick filament to a Z line; accounts for elasticity and extensibility
Nebulin: holds F actin together on thin filaments
Actinin: makes up Z line
Look at slide 24
:)
describe the sliding filament theory
As the actin slides over the myosin…
- zone of overlap enlarges
- H band shrinks
- I band shrinks
- A band remains the same
- The Z line moves closer to the A band
What is the motor unit of the neuromuscular junction?
neuron + all muscle cells stimulated by the neuron
What is the neuromuscular junction?
point of contact between the neuron and the muscle
What is the synaptic terminal of the neuromuscular junction?
end of axon that contacts motor end plate
What is the motor end plate of the neuromuscular junction?
point on muscle fiber that contacts synaptic terminal
What is the synaptic cleft?
gap between two neurotransmitters
What is a neurotransmitter?
chemical released into the synaptic cleft
in the case of the photo, Ach
Describe muscle contraction
Ach stored in synaptic vesicles
Impulse reaches end of neuron Ach released
Ach crosses gap & binds to receptors
Impulse travels through motor end plate down T-tubules to SR
Ca2+ ions diffuse out of SR into sarcoplasm
Ca2+ exposes the active site
Myosin then binds to active site
ATP is used and contraction occurs
Contraction continues as long as Ca2+ concentration is high
describe muscle relaxation
Ach decomposed by acetylcholinesterase (AChE) Ca ions transported back to SR Actin & myosin links broken Cross-bridges move back Active site is blocked once again
the tension produced by a muscle is determined by what 2 things?
the frequency of stimulation and the number of motor units stimulated
what is the All-or-None Law?
all fibers in a motor unit fully contract if stimulated
what is Recruitment?
steady increase in tension by increasing the number of contracting motor units
what is it called if a muscle never begins to relax?
Tetanus
What is muscle tone?
Why is it important?
Motor units contract randomly . There is tension but no movement. It can: -stabilize joints -hold objects in place -maintain posture
What is hypertrophy?
Constant, exhaustive stimulation that increases the number of organelles/proteins in a fiber; Overall enlargement of the muscles
what does hypertrophy increase?
mitochondria
glycolytic enzyme reserves
myofibrils
filaments within myofibrils
Do muscle fibers reproduce?
No
What is atrophy?
lack of constant motor neuron stimulation reduces organelles and proteins
What causes atrophy?
Age
Hormones
Lack of use
Nerve damage
is atrophy reversible?
yes if the fiber is not dead
Describe origin, insertion and Force
Origin: attachment site that does not move
Insertion: attachment site that moves
Force: tension
describe parallel muscles and give an example
Fascicles parallel to long axis
Unidirectional force
ie: Biceps brachii
describe convergent muscles and give an example
Fan shaped:
- multidirectional force
- versatility
- generates least amount of force
ie: Pectoralis major
describe pennate muscles and give an example
Feather shaped:
- fascicles oblique to long axis
- tendon passes through muscle
- greatest force
ie: deltoid
describe circular muscles and give an example
- Concentric fascicles around an opening
- Contraction decreases lumen diameter
ie: orbicularis oculi
rotation around one axis called what?
what movements does this allow?
Uniaxial
Rotation: atlantoaxial; pivot joints
Angular: knee, IP joints
Movement occurring along 2 axes is called what?
what movements does this allow?
Biaxial
Angular motions:
-flexion/extension and abduction/adduction
ie: ellipsoidal joint, radiocarpel, metacarpelphalange; caropmetacarpel (2-5)
describe multiaxial movement
what movements does this allow?
example?
- movement on all axes
- angular motion: same as biaxial
- rotation
- circumduction
ie: ball and socket
the main muscle causing directional force is called….
Agonist
The muscle that contracts to the main muscle causing directional force is called…
Antagonist
the muscle that assists/modifies movement is called….
Synergist
What is a fixator?
muscle that stabilizes elements associated with agonist
ie: deltoid stabilizes glenohumeral joint
What do lever systems do?
modify movements
Levers can change…. (4 things)
magnitude of force
speed
direction
distance of limb movement
What are the components of lever system?
Lever (L) = skeletal element
Effort (E) = applied force (AF)
Fulcrum (F) = joint
Resistance (R) = body part or object moved
What are the names of the three types of levers?
First, Second, and Third Class
Describe first class levers
teeter-totter/see-saw R opposite of E with central F Ex: neck extension E = neckextensors F = atlanto-occipital joint R = skull
Describe second class levers
wheel-barrow E opposite of F to move R Ex: plantar flexion E = calf F = MP joint R = weight of body
Describe third class levers
Shovel, broom E in between F and R Ex: elbow flexion E = biceps brachii F = elbow joint R = weight distal to joint
Describe fast fibers
- Fast acting; high energy requirements
- anaerobic
- large diameter
- densely packed myofibrils
- large glycogen reserves
- few mitochondria
- rapid, powerful brief contractions
Describe slow fibers
- More myoglobin; slower sustained contraction
- aerobic
- smaller diameter
- longer to contract
- contract for longer
describe Intermediate fibers
- Attributes of both fast and slow fibers
- similar to fast fibers
- greater resistance to fatigue
______ can change one muscle type to another
Exercise (or lack of)
What are 7 characteristics of smooth muscle?
attached to hair follicles in skin in walls of hollow organs & blood vessels nonstriated involuntary control contractions are slow and sustained Spindle shaped Very elastic
Do smooth muscles…
- ) Contract Slowly or Quickly?
- ) Resistant or Unresistant to fatigue?
Slowly
Resistant
What stimulates smooth muscles?
Nervous System
Hormones
Ions
Stretching
Describe Single-Unit smooth muscle
Where is it found?
- Many gap junctions
- Sheets of spindle-shaped cells
- Contract together (syncytial contraction)
ie: BV’s, digestive tract, respiratory tract, urinary tract
Describe Multi-Unit smooth muscle
Where is it found?
- No or few gap junctions
- Separate fibers; contract independently
- Only contract when stimulated by motor nerves
ie: walls of large BV’s, uterus, iris of eye
What are 5 characteristics of cardiac muscle?
striated in appearance involuntary control autorhythmic network of fibers with intercalated disks at ends found only in heart
