A&P TEST III

What are the three types of muscle?

Skeletal, cardiac, smooth

Characteristics of skeletal muscle

Moves bones

Sriated, alternating light and dark bands (striations) under microscope

Mainly voluntary

Many also controlled subconsciously

Characteristics of cardiac muscle

Found in walls of heart

Involuntary

Contraction is relaxation and initiated by node tissue called “pacemaker”

Characteristics of smooth muscle

Walls of hollow internal structures, skin, blood vessels, airways, and many organs

No striations

Involuntary

What is excitability?

Ability to respond to stimuli

What is contractility?

Ability to contract forcefully when stimulated

Extensibility

Ability to stretch without being damaged

Elasticity

Ability to return to an original length

Endomysium

Encloses individual muscle fibers and separates it from another one

Perimysium

Encloses fascicles (group of 10-100 or more fibers and separating them into bundles)

Epimysium

The outermost layer encircle the whole muscle, protect and strengthen skeletal muscle

Fascia

Dense sheet or broad band of irregular connective tissue that surrounds muscles. It holds muscles and allows free movement.

Tendon

All three connective tissues make the cord like structure, called tendon which attach a muscle to a bone

Aponeurosis

Broad, flattened tendon

Myofibril

Thread-like protein which extends from ends of muscle

Muscle fiber is created by

Fusion of myoblasts

Do myoblasts continue to undergo cell division after fusion?

No

Which cells do continue to undergo cell division after birth?

Satellite cells

What is dystrophin?

Maintains shape of myofibril

What is sarcomere bounded by?

Z-disc to Z-disc

What is thin band?

Actin

What is thick band?

Myosin

What constitutes the A zone?

Myosin

What is titin?

Supports myosin

What is the I band?

Only actin

What is the H zone

Actin and myosin

Myosin

Thick filament which functions as motor protein and can achieve motion

Convert ATP to motion

Having two heads and one tail

Actin

Thin filaments which provide a site where a myosin head can attach

Tropomyosin and troponin are also part of the thin filament

What happens when Ca binds to tropomyosin

Tropomyosin and troponin move to expose myosin binding sites on actin

What happens after tropomyosin and myosin move?

ATP in myosin head breaks down (lysis) and creates crossbridge

Contractile proteins

Myosin and actin generate force during contraction

Regulatory proteins

Troponin and tropomyosin help switch the contraction process on and off

Structural proteins

Titin and dystrophin keep thick and thin filaments in proper alignment and link the myofibrils to the sarcolemma and extracellular matrix

The contraction cycle

Excitation

Sarcoplasmic reticular contains CA to return back to the SR, decreasing calcium ion levels

Inside the SR, molecules of calcium binding protein called calsequestrin bind to the CA to be sequestrated or stored within the SR

Concentration of Ca is 10,000x higher in SR than in cytosol in a relaxed muscle fiber

As the Ca level in the cell drops, myosin-binging sites are covered tropomyosin and the muscle relaxes

What is the neuromuscular junction?

Motor neurons have a thread like axon that extends from the brain or spinal cord to a group of muscle fibers

What is a synapse

Region where communication occurs between somatic motor neuron and muscle fiber

What is the synaptic cleft

Region where communication occurs between a somatic motor neuron and a muscle fiber

What is a synaptic cleft

Gap that separates the nerve cell from the muscle cell

What is a neurotransmitter

Chemical released by the initial cell communicating with the second cell

What is the synaptic vesicle

Sacs suspended within synaptic end bulb containing neurotransmitter

Motor end plate

The region of the muscle cell membrane opposite the synaptic end bubbles which contain acetylcholine

What kind of channel is NA

Ligand gated

What kind of channel is K?

Leak

What is ATP needed for

Power the contraction cycle and pump Ca into the SR

What are the ways muscle fibers create ATP

Creatine phosphate, anaerobic cellular respiration (break down of glycogen), and aerobic cellular respiration (presence of oxygen)

What is muscle fatigue?

Inability of muscle to maintain force of contraction after prolonged activity

Factors that contribute to muscle fatigue

Inadequate release of calcium from SR

Depletion of creative phosphate

Insufficient oxygen

Depletion of glycogen and other nutrients

Buildup of location acid and ADP

Failure of the motor neuron to release enough ACH

Twitch contraction

Brief contraction of all the muscle fibers in a motor unit in response to a single action potential

Latent period

A brief delay between the stimulus and muscular contraction

The action potential sweeps over the SR and Ca is released from SR

Contraction period

Ca binds to troponin

Myosin binding sites on actin are exposed

Cross bridges form

Relaxation period

Ca is transported back into the SR

Myosin-binding sites are covered by tropomyosin

Myosin heads death from actin

Tension decreases

Refractory period

The period of loss excitability

Skeletal has refractory of 5 miliseconds

Cardiac has refractory of 300 milliseconds

Muscle tone

Tension 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 tone

Muscle tone keeps skeletal muscles firm

Isotonic contraction

The tension developed remains constant while muscle changes its length

Used for body movements and for moving objects

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

Holding a book steady using an outstretched arm

Red muscle fibers

Have a high myoglobin content

Appear darker

Contain more mitochondria, more energy stores

Supplied by more blood capillaries

White muscle fibers

Have a low content of myoglobin, less mitochondria, less blood supply

Apply lighter

Three muscle fiber classifications

Slow oxidative fibers, fast oxidative-glycolytic fibers, fast glycolytic fibers

Slow oxidative fibers

Smallest in diamter

Least powerful

Sark red

Aeorobic

Slow speed of contraction

Prolonged contractions

Endurance type

Fast-oxidative

Intermediate diameter

Large amounts of myoblobin

Dark red

Generate ATP aerobic

Moderately high resistance

Generate some ATP anaerobic

Faster

Walking and sprinting

Fast glycolytic

Fastest

Largest in diameter

Low myoglobin

Few mitochondria

White

Generate ATP by glyocolysis

Fatigue quickly

Weightlifting or throwing ball

Types of Fibers

Most muscles are mixture of all three types of muscle fibers

Proportions vary, depending on the action of the muscle, the person’s training regimen, and genetic factors

Postural muscles of neck, back, and legs have SO fibers

Muscles of shoulders and arms have FG fibers

Leg muscles have large numbers of both SO and FOG fibers

Intercalated discs

Unique to cardiac

Connects ends of cardiac muscle fibers

Allow muscle APs to spread from one to another

Cardiac muscle tissue contracts when stimulated by what

Its own rhythmic muscle fibers (node)

What respiration does cardiac muscle depend on

Aerobic

Requries lactic acid produced by skeletal muscle fibers to make ATP

How are APs spread in smooth muscle

Gap junctions

How are smooth muscles stimulated?

Neurotransmitter/hormone, or autonomic signals

Anatomy of smooth muscle

Thick and thin filaments

Not arranged with orderly sarcomeres

No regular pattern

Lack T tubules

Dense bodies

Dense bodies

Thin filaments attach to structures called dense bodies which function similar to Z-discs in skeletal muscle

Filaments pull on dense bodies causing a shortening of muscle fiber

Physiology of smooth muscle

Contractions last longer

Initiated by Ca

Ca move slowly out of the muscle fiber delaying relaxation

Able to sustain long-term muscle tone

Important in gastrointestinal tract and walls of blood vessels

What do smooth muscles respond to?

APs from autonomic, stretching, hormones, changes in pH, oxygen, and CO2

Hyperplasia

Increase in number of fibers (unusual)

Smooth muscles in uterus retain capacity for vision and can grow by hyperplasia

Hypertrophy

Enlargement of existing cells

Satellite cells divide slowly and fuse with existing fibers to grow muscle and repair

Cardiac muscle can undergo hypertrophy (like in athletes) due to increased workload

What term-layer does muscle come from?

Mesoderm

Cardiac and smooth are from migrating mesoderm cells

Aging in muscle

Loss of muscle mass

Decrease in strength

Slowing of muscle reflexes

Loss of flexibility

Largest muscle

Gluteus maximus

Muscle behind neck

Levator scapulae

Muscle of thigh

Adductor Magnus and tensor tympani

Muscle of calf

Fivularis longus (top) and fibulas braves (bottom) of fibia

Muscle of abdomen

Transversus abdominus

Muscle of arms

Biceps and tibialis anterior

What is origin of muscle

Non-moveable part

What is the fleshy part of muscle?

Belly

What is moveable part of muscle?

Insertion

What is origin, insertion, and action of biceps brachia?

Origin is scapula, radius is insertion, action is pronate and flex arm

Origin, insertion, and action of triceps brachia

Scapula is origin, upper and lateral posterior sites of humerus and posterior surface of humerus. Insertion is back of olecranon process of ulna. Action is straighten

What is a lever?

Rigid structure that can move around a fixed point is called a lever.

Point of movement (fulcrum) is acted on by two different forces: effort (muscle) and load (resistance)

First class lever

Fulcrum (atlanto-occipital joint)

Load (facial bones)

Effort (muscles of the back of neck

Second class lever

Compares with wheelbarrow.

Fulcrum (metatarsophalangeal joints)

Effort (gastrocnemius)

Whole body weight is resistance

Third class lever

Fulcrum (elbow joint)

Effort (biceps brachii)

Load (bones of hand)

What is coordination of moving muscles?

Agonist )prime mover ) and antagonist (stretches or yields)

EX. Brachialis is prime mover and agonist is triceps brachia

What is synergistic muscle

Muscles used to aid of assist in movement (biceps move with brachialis)

What is the fixator?

Synergist muscle used to steady or fix the proximal joints of prime mover

EX. shoulder stabilizes for the forearm flexors

Muscles of mastification

Masseter, temporalis, medial and lateral pterygoid

Orbicularis oris

Mouth

Muscles of facial expression (muscle to skin)

Orbicularis oris

Orbicularis oculi

Occipitofronatlis

Zygomaticus major

Zygomaticus minor

Buccinator

Bells Palsy

Facial paralysis wherein person is unable to wrinkle forehead, close eye, or pucker lip on the affected side

What moves eyeball

Extraocular muscle

Muscle of chest

Pectoral’s major and minor

Anterior abdominal muscle group

Latissimus dorsi

Biceps brachii

Diaphragm

Trapezius

Deltoid