MCAT Biology The Musculoskeletal System

The Musculoskeletal System

Skeletal Muscle

responsible for voluntary movement, innervated by somatic nervous system. Multinucleated formed with individual muscle cells fuse into long rods

Red fibers

slow twitch fibers, high myoblobin contant and derive energy areobically

White fibers

fast twitch, contain less myoglobin

Smooth muscle

responsible in voluntary action, contracted ANS, single nucleus, stritation cannot be seen but contain actin and mysin, more sustained contractions

Cardiac muscle

smooth and skeletal muscle, contraction involuntary and innervated by ANS, appears striated, connected by intercalacted discs

Sacromeres

arrangement of actin and myosin into repeating units

Myoglobin

An oxygen carrier that uses iron in a group to bind oxygen

Tonus

constant state of low level contraction

Gap junctions

connections between the cytoplasm of adjacent cells, allowing for flow fo ions directly between cells

Z line

define the boundaries of each sacromere

M line

runs down the center of the sacromere, through the middle myosin filaments

I band

is the region containing exclusively thin filaments

H zone

contains only thick filaments

A band

contains the thick filament in their entirety

Sacroplasm

modified cytoplasm located outside the sacromere

Sacrolemma

cell membrane of a myocyte

Single twitch

response of a single muscle fiber to a brief stimulus at or above threshold

Latent period

time between reaching threshold and the onset of contraction

Requency summation

contraction combine, become stronger and more prolonged

Retanus

contraction become so frequent muscle is unable to relax at all

Oxygen debt

difference bewteen amount oxygen needed by muscles and amount present

Periosteum

fibrous sheath that surrounds long bone to protect it and serve site for muscle attachments

Tendons

attach muscle to bone

Ligaments

hold bone together at joints

Exoskeletons

encase whole organism, seen in arthropods

endoskeletons

Skeletons that are internal

Axial skeleton

Skull, vertebral column, rib cage, hyoid bone, provides basic central framework for body

appendicular skeleton

bones of limbs, the pectoral girdle and pelvis

Harversian canals

longitudinal channels

Volkmans canals

transverse canals

Osteoblasts

cuild bone

Osteoclasts

resorb bone

Endochondral ossification

process of creating bones by hardening cartilage into bone

Intramembranous ossification

undifferentiated embryonic connective tissue transformed and replaced by bone

Immovable joints

consist of bones that are fused together to form sutures

movable joints

permit bones to shift relative to one another

articular cartilage

contributes to the joint by coating the articular surfaces of the bones so that impact is restricted to the lubriacrated joint cartilage rather than bones

origin

the end of the muscle with larger attachment to the bone

insertion

the smaller attachment to the bone

antagonistic pairs

one relaxes the other contracts

synergistic

working together accomplish same function

flexor

muscle decreases angle across joint

extensor

increases, straightens the angle

Abductor

moves body part away from midline

adductor

moves body part toward midline

medial

rotate axis of limb toward midline

lateral

rotate axis of limb away from midline