Intro to Muscles Flashcards
What are the 3 types of muscle tissue? What are the 4 properties of muscles?
Skeletal, Smooth, Cardiac
Excitability (respond to stimulation), Contractility (shorten/ pull), Extensibility (contract over different lengths), Elasticity (regain original length)
What are the 3 major characteristics of muscles?
Skeletal muscles are somatic structures (voluntary control)
Skeletal muscles are innervated by spinal nerves or cranial nerves (from brainstem)
Skeletal muscles are contractile organs that attach directly/ indirectly onto bones
Their contraction produces motion of the body
What are the 5 major functions of skeletal muscle?
- Produce movement at joints of skeleton (via tendons or muscle fibres attaching into bones)
- Maintain posture and body position (even at rest, contract to stabilize)
- Support soft tissues (abdominal wall and pelvic floor muscles support viscera)
- Regulate orifices (sphincters)
- Maintain body temp (SM contraction generates heat)
What are the structures of skeletal muscle going from largest to smallest? What are the 3 sheaths of connective tissue found in it?
Muscle organ, muscle fascicle, muscle fiber
Perimysium (interface between muscle fascicle and BV)
Epimysium (covers muscle organ)
Endomysium (covers fiber)
What is the structure of the muscle fibre?
Has many myofibrils inside of it (functional unit), interspersed between them are many mitochondria
Has sarcoplasmic reticulum which stores Ca+ for muscle contraction
T junctions spread depolarization deep into the fibril
What is the basic contractile unit of the myrofibril/muscle? What is its structure?
Sarcomere
Myofibril has the M line in the center and the Z lines that are on the outsides of the sarcomere
Interdigitation of thick (myosin, M line) and thin (actin) filaments
What are the three bands on the sarcomere? What happens at rest and during contraction?
H band: contains thick filaments (myosin), with M line
I band: contains thin filaments only (actin), with Z line
A-band: contains thick and thin filaments (zone of overlap, contains the H band)
REST: all bands at rest, no contractions
CONTRACTION: width of H and I bands decrease, width of A band increases
What happens with Ca+ during muscle contraction?
Ca+ increases (from sarcoplasmic reticulum), and cross bridging between thick and thin filaments and pivoting of myosin heads towards the M-line
What are the 3 steps in nerve stimulation and muscle contraction?
- Each muscle cell (fibre) is innervated by a motor neuron (nerve cell)
- When the neuron fires, it signals the muscle cell to contract
- Contraction is all or none phenomenon, muscle cell either contracts fully or does not contract at all
What is a motor unit?
A motor neuron innervates many muscle cells, and all the muscle cells controlled by single motor neuron is called a motor unit
The amount of muscle tension produced depends on the # of motor units that are stimulated
What are slow skeletal muscle fibers?
Red (due to lots of mitochondria and myoglobin)
Narrow diameter, resistant to fatigue, less powerful contractions
ATP produced by mitochondria through aerobic metabolism
Extensive network of capillaries (because need O2, aerobic)
Enlarged soleus muscle in leg of long distance runner
What are fast skeletal muscle fibers?
White, large diameter, rapid contraction, powerful contractions, fatigue rapidly
ATP generated by anaerobic glycolysis (use stored glycogen, not O2)
Enlarged gastrocnemius muscle in sprinter
What are the 4 types of muscle fascicle organization?
Parallel, convergent, circular, pennate
What are parallel muscles?
Fascicles are parallel to long axis of muscle, most common
Muscle is flat band or spindle shaped
Spindle has central portion (belly)
During contraction, muscle gets shorter and belly gets wider
Exert great force because all fascicles pull in same direction
EXAMPLES: biceps brachii, rectus abdominus
What are convergent muscles?
Fan shaped, fascicles originate over wide area but converge at common attachment site
Direction of pull can be changed by varying which fascicles contract
Do not exert as much force because not all fascicles pull in same direction
EXAMPLES: pectoralis major, trapezius
What are circular muscles?
Fibers concentrically arranged around opening or recess (form sphincters)
Contraction of muscle reduces diameter of opening
EXAMPLES: orbicularis oculi and oris
What are pennate muscles?
Tendons run through body of muscle, fascicles form oblique angle relative to tendon
Contain more muscle fibres than parallel muscle of same size (generate more force)
Unipennate (muscle fibers on one side of tendon, extensor digitorum)
Bipennate (muscle fibers on both sides of tendon, rectus femoris)
Multipennate (tendon branches within the muscle, deltoid)
How are muscles named?
According to :
Structure or shape of muscle (deltoideus=triangular, maximus=large, brevis=short)
Specific region of body (carpi=wrist, abdominis= abdomen)
Attachment sites
Relationship to other muscles
Action of the muscle (flexor)
What is an example of a muscle named by shape/location?
Rectus abdominis (straight, abdomen)
Trapezius (trapezoid)
Deltoid (triangular)
What is a muscle named by attachment site?
Sternocleidomastoid (sternum, clavicle, mastoid)
What is a muscle named by action, attachment sites, and location?
Flexor digitorum superficialis (flexion, fingers, superficial)
Flexor digitorum profundus (flexion, fingers, deep)
How to muscles attach and move?
Attach on individual bones or soft tissue, usually cross at least one joint, pull one bone towards another so that movement produced at the joint
Can stabilize a joint so other muscles can act and produce movement
What are the 3 sites that are significant when talking about muscle attachment
Action: type of movement
Insertion: muscle attachment to moveable bone
Origin: muscle attachment to stationary bone
What are the three types of primary muscle actions?
- Agonist: prime mover, contraction produces a particular movement
- Synergist: assists prime mover in performing an action
- Antagonist: opposes the movement of an agonist
What are the 4 structures in a muscle movement system?
Lever: rigid structure, moves on fulcrum, moves weight
Fulcrum: fixed point
Weight: the thing being moved
Force: required to move weight generated by muscle contraction
What is involved in a first class lever? (locations, advantage and drawback, common?)
Fulcrum is located between the muscle force (F) and the weight
Increases range and speed of movement BUT requires larger force
Not many examples in body
What is involved in a second class lever?
Weight is located between muscle force and fulcrum
Increases force but at the expense of range/speed of motion
Not many examples in the body
What is involved in a third class lever?
Force applied is between weight and fulcrum
Increase range and speed of movement at the expense of force
MOST common in the body
Can there be a difference between muscle action and muscle function? What is an example?
YES
Action of the lesser gluteal muscles- abduction of thigh at hip joint
Function of the lesser gluteal muscles - keep pelvis from tilting down on unsupported side (swinging of leg) while walking
