ANA Exam #3 Bulk Study

Excitation-contraction coupling

for a skeletal muscle fiber to contract, its membrane must first be excited (stimulated to fire an action potential)

Muscle Fiber Contraction

(image)

Acetylcholine (ACh)

neurotransmitter released at the NMJ

Triad

arrangement of a T-tubule with SR membranes on either side

Step 1

action potential arrives at neuromuscular junction

Step 2

ACh is released, binds to receptors and opens sodium ion channels, leading to an action potential in sarcolemma.

Step 3

action potentials travel along T-tubules

Step 4

thick and thin filament interaction leads to muscle contraction

muscle cells =

muscle fibers

Epimysium

muscle covering/fascia; connects to tendons, bones

Perimysium

covers Fascicles; blood vessels and nerves

All CT layers in muscles

loose CT, usually Reticular; all layers are connected (continuous)

Origin

connection of a muscle to the skeletal system; less moveable side; usually proximal

Insertion

Connection of a muscle to the skeletal system; more moveable side; usually distal

Direct attachments

Epimysium attaches directly to bone or cartilage; no tendon or aponeurosis; ex. brachialis, Gluteus Medius and Minimus origins

Indirect attachments

Epimysium connects to CT, then to bone; very common; stronger, can stretch, smaller to cross over joint; ex. insertions of gluteus medius and minimus, top of skull (aponeurosis, broad + flat)

Retinacula

Specialized structure of strong ligaments that holds tendons down; tendons would lift up (wrist) or slip out (ankle) without them.

Endomysium

covers muscle fibers

Synergists

muscles that work together to produce the same movement; ex. 4 quadriceps muscles → knee extension

Antagonists

opposite motions; muscles that work together to accelerate/decelerate; ex. biceps vs. triceps(elbow flexion/extension), hamstrings vs. quadriceps(knee flexion/extension)

Prime movers

the strongest/most important player in a group of synergists; ex. gluteus maximus (greatest extensor), rectus femoris (knee extension)

Fixator

Stabilizes a joint instead of producing movement; ex. gluteus medius contracting while standing on one foot

Circular fascicle arrangement

locations: external openings, ex. sphincters, facial muscles

Convergent fascicle arrangement

Broad origin, converging toward a single tendon

locations: pectoralis major, latissimus dorsi

Pennate

fibers branch off a long central tendon

purpose: strength due to multiple angles of pull on same tendon; does not shorten much

Unipennate

fibers branch off in one direction; ex. extensor digitorum longus

Bipennate

fibers branch off in 2 directions; ex. rectus femoris

multipennate

fibers branch off in multiple directions; ex. deltoid

Parallel

very long muscle fibers, can shorten well; not as strong as pennate muscles, less fibers in contact with tendons; ex. Sartorius

Fusiform

similar to parallel, but with enlarged central portion; can produce more force than parallel; ex. biceps brachii

Functional groups of muscles

synergists, antagonists, prime movers, fixators

Fascicles

Covered by Perimysium, together make up a muscle

Muscle fiber (muscle cell)

Covered by Endomysium; together make up a fascicle.

Sarcolemma

cell membrane; found under the endomysium of muscle fibers.

Myofilaments

together make up sarcomeres; contain protein fibers actin and myosin.

Muscles of the Gluteal Region

location: posterior hip

general actions: hip extension, abduction, rotation (medial and lateral), and stabilizing pelvis during locomotion (lifting of one limb when walking or running, etc.)

names: gluteus maximus, gluteus medius, gluteus minimus, tensor fasciae latae, (IT Band, not a muscle but in this region)

Illiotibial tract (IT band)

Thick CT, joins with fascia latae to affect the knee, provides partial insertion point for gluteus maximus; crosses hip and knee joint

Gluteus Maximus origin and insertion

Origin: posterior ilium, sacrum, and coccyx

Insertion: gluteal tuberosity, IT band

Gluteus Maximus actions

Primary = Hip extension (from a place of flexion)

Secondary = hip abduction, lateral/external rotation of hip

Crosses hip joint

Gluteus Medius origin/insertion

origin: Posteriur Ilium, below Iliac crest

Insertion: Greater trochanter of the Femur

Gluteus Medius actions

(same as minimus) Hip abduction, pelvis stabilization while walking (Trendelenburg’s sign), internal/medial hip rotation

crosses hip joint

Gluteus minimus origin/insertion

Origin: ilium, slightly inferior to medius site

Insertion: greater trochanter of the femur (same as medius)

Gluteus minimus actions

(same as medius) Hip abduction, pelvis stabilization during walking, internal/medial hip rotation

crosses hip joint

Tensor Fasciae Latae origin/insertion

Origin: Anterior superior iliac spine and Anterior iliac crest

Insertion: IT band

Tensor Fasciae Latae actions

locks knee into extension by tightening the IT tract, hip abduction, hip medial/internal rotation

Crosses: directly hip joint, by extension of IT band, knee joint

Anterior thigh muscles overview

Innervation: femoral nerve

Actions: knee extension, hip flexion

Posterior thigh muscles (AKA hamstrings) overview

3 muscles (medial to lateral): semimembranosus, semitendinosus, biceps femoris

innervation: sciatic nerve

Actions: knee flexion, hip extension

Crosses: hip and knee joints

Tight hamstrings = difficulty bending over, touching toes, walking, etc.; leads to back problems

Medial thigh muscles overview

hip stabilizers and adductors

Pectineus, adductor longus, gracilis, adductor brevis, adductor magnus

innervation: obturator nerve

Action: hip adduction

Iliopsoas (anterior thigh muscle)

made up of 2 muscles (iliacus, psoas major)

origin: T12-L5, Iliac fossa, lateral sacrum

insertion: lesser trochanter of femur

action: primary hip flexor

crosses: hip joint

Quadriceps Femoris (anterior thigh muscles) (origin/insertion)

4 headed muscle(RF, VL, VI, VM); most powerful in the body; quad-hamstring ratio (quads typically stronger than hams)

Origins: RF → at iliac/hip; Vl, VI, VM → at femur

Insertion: patella (tibial tuberosity)

Quadriceps Femoris actions

RF: Hip flexion, kne extension (ex. soccer kick)

VL (most powerful of the V’s): knee extension, knee stabilization

VI: knee extension

VM: knee extension, knee stabilization

VL & VM work together to keep Patella tracking (within its natural groove)

Sartorius (anterior thigh muscle)

longest muscle in the body

Origin: ASIS

Insertion: Proximal-medial tibia (pes anserine)

Actions: hip flexion, hip abduction, lateral/external rotation of hip

Crosses: hip joint primarily

Biceps Femoris (origin/insertion/actions)

has 2 separate heads (“bi”), lateral most hamstring

Short head origin: linea aspera of femur (doesn’t cross hip like other hamstrings)

Long head origin: Ischial tuberosity

Insertion: lateral condyle of tibia and head of fibula

Actions: knee flexion, hip extension, external rotation of the hip

Crosses: knee and hip

Semimembranosus (origin/insertion/actions)

Origin: ischial tuberosity

Insertion: medial condyle of Tibia

Actions: hip extension, knee flexion, internal/medial hip rotation (same as tend.)

Crosses: knee and hip joints

Semitendinosus

Origin: Ischial tuberosity (like memb.)

Insertion: medial, proximal tibia (pes anserine)

Actions: hip extension, knee flexion, internal/medial hip rotation (same as memb.)

crosses: knee and hip joints

Pectineus

innervated by femoral nerve

Origin: superior anterior edge of pubis

Insertion: inferior to lesser trochanter (posterior)

Actions: hip flexion, hip adduction

Crosses: hip joint

Adductor Longus

origin: near pubic symphysis

Insertion: linea aspera (posterior femur)

Action: adduction of hip

Crosses: hip joint

Gracilis

2nd longest muscle

Origin: inferior ramus of pubis, medial to adductor longus

Insertion: pes anserine

Action: hip adduction, knee flexion

Crosses: hip and knee joint

Adductor Brevis

Origin: inferior ramus of pubis (like Gracilis)

Insertion: linea aspera

Action: hip adduction

Crosses: hip joint

Adductor Magnus

(deep to brevis + longus)

Origin: ischial tuberosity

Insertion: linea aspera

Action: powerful hip adduction (ex. soccer kick)

crosses: hip joint

Shoulder joint complex

articulations: glenohumeral joint, sternoclavicular joint, acromioclavicular joint, and scapulothoracic joint

bones: scapula, humerus, sternum, clavicle

Glenohumeral joint

sternoclavicular joint

Acromioclavicular joint

Scapulothoracic joint

Elbow joint complex

articulations: humeroulnar, humeroradial, proximal radialulnar joint

bones: humerus, ulna, radius

proximal radialulnar joint

Hip Joint

bones: femur, pelvis (os coxa)

Knee Joint complex

articulations: femur-tibia, fibula-tibia, patella-femur

bones: Tibia, fibula, patella, femur

Fibrocartilage: medial and lateral menisci

Ankle joint complex

articulations: Talo-crural joint, Subtalar joint (talus-calcaneus)

bones: tibia, fibula, talus, calcaneus

subtalar joint

Muscle fiber

a long, thread-like, multinucleated cell filled with smaller subunits called myofibrils, which contain the protein filaments actin and myosin responsible for contraction

Fascicle

bundles of muscle fibers

myofibril

a long, rod-like organelle inside muscle cells that causes muscles to contract

sarcomere

the basic functional and contractile unit of striated muscle tissue

actin

tiny, flexible protein fibers inside cells that provide structural support and help the cell move; forms the thin filaments

myosin

a primary motor protein that forms the thick filaments within muscle fiber sarcomeres