Anatomy Exam2 (pt. 2)

function of muscles

• generates tension (pulling force)

• movement

  • locomotion

  • movement of body parts

  • movement within body

• joint stabilization during movement of body

• maintenance of posture

• production of heat

contractility

property of muscle tissue that generates tension (pulling force)

excitability

property of muscle tissue that can be stimulated to contract by chemical or electrical signals

extensibility

property of muscle tissue that can be stretched beyond resting length without being damaged

elasticity

property of muscle tissue that returns to resting length after being stretched or contracting

skeletal muscle

• long cylindrical cells (myofibers)

• multinucleate

• striated

• generates conscious/voluntary actions

muscle fascicles

• contains bundles of muscle fibers (cells) within muscle

• surrounded by perimysium

myofibers/muscle fibers

• muscle cells

• runs entire length of muscle

• holds myofibrils

myofibrils

bundles of contractile protein within muscle fibers

Epimysium

dense connective tissue surrounding muscle

Perimysium

connective tissue surrounding bundles of muscle fibers

Endomysium

connective tissue surrounding each muscle fiber

motor unit

all muscle fibers innervated by single neuron; contract as a unit

large motor units

gross motor control

small motor units

fine motor control

tendon

connective tissue joining muscle to bone (or skin), usually card-like

aponeurosis

sheet-like tendon

origin

• stationary skeletal element, anchors muscle

• on limb: usually proximal

• ex) humerus

insertion

• movable skeletal element

• on limb: usually distal

• ex) ulna

primary action

insertion moves toward origin

secondary action

• origin moves towards insertion

• ex) cervical vertebrae (origin) and first two ribs (insertion)

heads 

• multiple origins

• more common for muscles to have multiple ____

• ex) biceps brachii has two heads

slips

multiple insertions

proximal insertion

placement of insertion where there is greater speed

distal insertion

placement of insertion where there is greater strength

antagonistic

one muscle or set of muscles having an opposite action of second muscle or set

synergistic

muscle performs same action

hyperplasia

increase in number of cell

hypertrophy

increase in cell size

hypertrophy growth

skeletal muscle grows by ___ of muscle fibers

circular

• fibers arranged in concentric rings

• ex) orbicularis oculi

parallel

• fibers oriented parallel to lines of force generated

• light load through long distance

• ex) bicep brachii

pennate

• fibers are oblique to force generated

• heavy load through short distance

• ex)muscle fibers at an angle

sarcolemma

cell membrane surrounding skeletal muscle

sacroplasm

cytoplasm of muscle cells

T-tubles

extensions of sacrolemma into muscle fiber

sacroplasmic reticulum

stores and releases Ca++

myofibril

bundle of protein filaments within muscle fiber

myoglobin

pigment that stores oxygen

actin

• thin filaments

• structural

• binding site for myosin

tropomyosin

• covers binding sites for myosin

troponin

• moves tropomyosin away from binding site

• activated by Ca++

sacromere

• z-line to z-line repeated

myosin

• thick filaments

• motor

• uses ATP for energy

• head binds to actin

• head pivots and pulls actin filaments clsoer together

titin

• provides elasticity

• aligns thick filaments

• runs from Z-line to Z-line

nebulin

• aligns thin filaments

relaxed

• tropomyosin blocks myosin binding on actin

• no Ca++ on troponin

• myosin NOT bind to actin

contraction

• AcH generates action potential along sacrolemma

• actional potential spreads down T-tubes

• Action potential triggers release Ca++ from sacroplasmic reticulum

• Ca++ binds to troponin

• troponin activates and pulls tropomyosin away from actin binding site

• myosin binds to actin, creating tension

generates tension (pulling force)

• myosin pulling the actin/thin filaments together

ATP

myosin doing the work and uses ___

slow twitch

• low force

• high endurance

• ex) posture

fast fatigue-resistance

• intermediate force

• intermediate endurance

• ex) walking, jogging

fast fatigable

• high force

• low endurance

• ex) sprinting, weight-lifting

fast twitch fibers

• eye and finger muscles 

neuromuscular junction

synapse between motor neuron and skeletal muscle fiber

acetylcholine

neurotransmitter released from somatic motor neuron

motor end plate

region of muscle fibers w/ acetylcholine receptors

smooth muscle

• regulated autonomically (involuntary)

• uninucleate

• not striated

• highly stretchable

• highly resistant to fatigue

  • contracts slowly

frontalis

elevates eyebrow

corrugator supercilii

depresses eyebrow medially

orbicularis oculi

closes eye

levator palpebrae superioris

elevates upper eyelid; opens eye

orbicularis oris

puckers lip

depressor anguli oris

depresses corner of mouth

zygomaticus major

elevates and retracts corner of mouth

risorius

retracts corners of mouth; tenses lip

levatator labii suprioris

elevates upper lip

buccinator

compresses cheeks

mentalis

• wrinkles chin

• protrudes lower lip

platysma

• tenses skin of neck

lateral pterygoid

• depresses mandible

• opens mouth

medial pterygoid

• elevates mandible

• closes mouth

masseter

• elevates mandible

• closes mouth

genioglossus

• protracts tongue

hyglossus

• retracts tongue 

digastric, mylohyoid

• swalling

superior rectus

elevates eye

inferior rectus

depresses eye

medial rectus

adducts eye

lateral rectus

abducts eye