Skeletal & Muscular Systems Flashcards
2 components of the skeleton:
cartilage and bone
cartilage
- type of CT that is softer and more flexible than bone
- chondrocytes are cells responsible for synthesizing cartilage
bone
-mineralized CT that can withstand physical stress
compact bone
-dense bone composed of structural units called osteons
structure of an osteon
-central microscopic channel called a Haversian Haversian canal surrounded by a number of concentric circles called lamellae
spongy bone
- less dense, consists of bony spicules (trabeculae)
- cavities b/w spicules filled with red (blood cell formation) or yellow bone marrow (infiltrated by adipose tissue)
osteoblasts
- synthesize new bone
- mature into osteocytes
osteoclasts
-bone is broken down and released into the blood
endochondral ossification
- existing cartilage is replaced by bone
- typically long bones
intramembranous ossification
-CT is transformed into and replaced by bone
pyramidal system
-provides rapid motor commands (voluntary) to skeletal muscle and other organs
extrapyramidal system
-somatic motor commands as a result of processing performed at the involuntary level
skeletal muscle
- responsible for voluntary movement and is innervated by the somatic nervous system
- striated
myofibrils
-embedded in the fibers, further divided into contractile units called sarcomeres
sarcoplasmic reticulum
-modified ER that envelopes myofibrils and stores calcium ions
sarcolemma
- cell membrane of a muscle fiber
- propagates an action potential and is connected to a system of transverse tubules
T system
-provides a channel for ion flow throughout the muscle fibers
sarcomeres
-composed of thin (actin) and thick (myosin) filaments
Z line
defines boundaries of a single sarcomere
M line
runs down the center of the sarcomere
I band
contains thin filaments only
H zone
contains thick filaments only
A band
spans the entire length of the thick filaments and any overlapping portions of thin filaments
neuromuscular junction
link b/w the nerve terminal and the sarcolemma of the muscle fiber
contraction
- once an action potential is generated, it is conducted along the sarcolemma and the T system into muscle fibers
- sarcoplasmic reticulum release calcium ions which bind to troponin C and initiates contraction
rigor mortis
several hours after death, all the muscles in the body contract and go rigid b/c of the absence of ATP
isotonic contractions
muscle shortens against a fixed load while tension remains constant
dynamic contraction
change in the length of the muscle with a corresponding change in tension
concentric contraction
type of dynamic concentration where the muscle fibers shorten and tension increases
eccentric contraction
type of dynamic contraction where muscle fibers lengthen and tension increases
isometric contraction
when both ends of the muscle are fixed and no change in length occurs, but tension increases
simple twitch
- response of a single muscle fiber to a brief stimulus at or above the threshold stimulus
- consists of a latent period, contraction period, and relaxation period (absolute refractory period)
temporal summation
-when fibers of a muscle are exposed to frequent stimuli, muscle cannot fully relax and contractions combine to become stronger and more prolonged
tetanus contraction
- contractions become continuous when the stimuli are so frequent that the muscle cannot relax
- stronger than a simple twitch
tonus
- state or partial contraction
- muscles are never completely relaxed
Cori cycle
-during strenuous activity, skeletal muscles convert lactic acid into glucose
smooth muscle
- involuntary actions
- innervated by ANS
- lack striations, posses one nucleus
cardiac muscle
-heart muscle
-striated
-one or two nuclei
involuntary, ANS
energy reserves
- creatine phosphate: in vertebrates, energy is temporarily stored in this compound
- myoglobin: maintains oxygen supply in muscles by binding oxygen tightly
