Chapter 11: The Musculoskeletal System Flashcards
What are the 3 types of muscle?
- skeletal
- smooth
- cardiac
Sarcomeres are repeating units of ________ and ____________.
actin; myosin
____ fibers, also known as ____-________ fibers, have high myoglobin content and primarily derive their energy aerobically.
red; slow-twitch
____________ is an oxygen carrier that uses iron in a heme group to bind oxygen.
myoglobin
________ fibers, known as ________-________ fibers, contain much less myoglobin.
white; fast-twitch
Muscles that contract slowly, but can sustain activity, contain a predominance of ____ fibers.
red
Muscles that contract rapidly but fatigue quickly contain mostly ____ fibers.
white
Compared to skeletal muscle, smooth muscle is capable of more sustained contractions; a constant state of low-level contraction, as may be seen in the blood vessels, is called ________.
tonus
smooth muscle can contract without nervous system input in what is known as ____________ activity; the muscle cells contract in response to stretch or other stimuli
myogenic
Cardiac muscle has characteristics of what?
Both smooth and skeletal muscle types
Cardiac muscle cells are connected by ____________ ________, which contain many gap junctions.
intercalated discs
Gap junctions (connections between cytoplasm) in cardiac muscle allow for what?
Flow of ions directly between cells; allows for rapid and coordinated depolarization of muscle cells and efficient contraction
Starting at the ____________ node, depolarization spreads using conudction pathways to the ________________ node.
sinoatrial; atrioventricular
From the AV node, depolarization spreads to the ________ of ____ and its branches, and then to the ________ fibers.
bundle of His; Purkinje
The ________ nerve provides parasympathetic outflow to the heart and slows the heart rate.
vagus
____________ from sympathetic neurons or ____________ from the adrenal medulla binds to adrenergic receptors in the heart, causing increased HR and greater contractility.
norepinephrine; epinephrine
Epinephrine increases heart rate by doing what?
Increasing intracellular calcium levels within cardiac myocytes
Cardiac contraction, like all types of muscle, relies on ________.
calcium
The ____________ is the basic contractile unit of skeletal muscle.
sarcomere
Sarcomeres are made of ________ and ________ filaments.
thick; thin
The thick filaments are organized bundles of ____________, whereas the thin filaments are made of ________ along with 2 other proteins, which are?
myosin; actin; troponin and tropomyosin
acTin with a T for troponin and tropomyosin
Another protein, ________, acts as a spring and anchors the actin and myosin filaments together, preventing excessive stretching of the muscle.
titin
____-lines define the boundaries of each sarcomere.
Z-lines
The ____-line runs down the center of the sarcomere, through the middle of the myosin filaments.
M
The ____-band is the region containing exclusively thin filaments, whereas the ____-zone contains only thick filaments.
I; H
The ____-band contains the thick filaments in their entirety, including any overlap with thin filaments.
A
Sarcomere are attached end-to-end to form ____________.
myofibrils
Myofibrils are surrounded by a covering known as the ________________ ____________, a modified endoplasmic reticulum that contains a high concentration of Ca2+ ions.
sarcoplasmic reticulum
The ____________ is a modified cytoplsm just outside the sarcoplasmic reticulum.
sarcoplasm
The cell membrane of a myocyte is known as the ________________.
sarcolemma
What does the sarcolemma do?
Propagates an action potential and distributes AP to all sarcomeres
The sarcolemma distributes AP to all sarcomeres in a muscle using a system of ____________ ____________ that are oriented perpendicularly to the myofibrils.
transverse tubules
Each ____________, or muscle cell, contains many myofibrils arranged in parallel and can also be called a ________ ________.
myocyte; muscle fiber
Contraction starts at the ____________ ________, where the nervous system communicates with muscles via ________ ____________.
neuromuscular junction; motor neurons
The signal from the neuromuscular junction travels down the neuron until it reaches the ________ ____________, or ____________ ________.
nerve terminal (synaptic bouton)
At the nerve terminal, ____________ is released into the synapse.
acetylcholine
In the case of the neuromuscular junction, the nerve terminal can also be called the ________ ____ ________.
motor end plate
Acetylcholine binds to receptors on the ____________, causing depolarization.
sarcolemma
Each nerve terminal controls a group of myocytes. Together, the nerve terminal and its myocytes constitute a ________ ________
motor unit
Depolarization triggers an AP. What order does it pass through?
- Sarcolemma
- T-tubules
- Muscle tissues
- Sarcoplasmic reticulum
What happens after an action potential reaches the sarcoplasmic reticulum?
Ca2+ is released
After Ca2+ is released, what do they bind to? What happens next?
Troponin; since troponin is bound to tropomyosin, tropomyosin undergoes a confirmational change
What happens when tropomyosin changes?
Myosin-binding sites are exposed on the actin thin filament
What recocks the myosin head for the next actin-myosin cross-bridge cycle?
hydrolysis of ATP to ADP and Pi
The repetitive binding and releasing of myosin heads on actin filaments causing the sliding of the thin filament across the thick filament is known as what?
sliding filament model
Actin filaments are ________.
thin
“Acthin”
Acetylcholine is degraded in the synapse by the enzyme known as ________________.
acetylcholinesterase
Once acetylcholine is degraded, what happens?
- Signal terminates at neuromuscular junction
- Sarcolemma repolarizes
- Calcium release ceases
- SR takes up calcium from sarcoplasm
The ________ period is the time between reaching threshold and the onset of contraction.
latent
when AP spreads along muscle and allows Ca2+ to be released from SR
If a muscle fiber is exposed to frequent and prolonged stimulation, it will have insufficient time to relax. Contractions will combine and become stronger/prolonged. This is ____________ ____________.
frequency summation
When contractions become so frequent that the muscle is unable to relax at all, this is known as ____________.
tetanus
Slow-twitch muscle fibers have high levels of ____________.
mitochondria
What process do muscles use to make ATP? Why?
oxidative phosphorylation, because they have lots of mitochondria
There are two supplemental energy reserves in muscle. What are they?
- Creatine phosphateis
- Anaerobic glycolysis
____________ ____________ is created by transferring a phosphate group from ATP to creatine during times of rest. How is ATP created from this when muscles are being used?
creatine phosphate; the reaction can be reversed to quickly generate ATP from ADP
creatine + ATP <–> creatine phosphate + ADP
When muscles run out of oxygen during exercise, ____________ reserves are used to keep aerobic metabolism.
myoglobin
________-________ muscle fibers have fewer mitochondria and must rely on glycolysis and fermentation to make ATP under most circumstances.
fast-twitch
Sometimes, even ________-________ muscle fibers must switch to anaerobic metabolism and produce lactic acid, at which point the muscle begins to fatigue.
slow-twitch
(red fibers)
The difference between the amount of oxygen needed by muscles and the actual amount present is called what?
oxygen debt
After strenuous exercise, the body must metabolize all of the lactic acid it has produced. Most lactic acid is converted back into ____________, and enters what cycle?
pyruvate; citric acid cycle
The axial skeleton consists of what 4 parts?
- Skull
- Vertebral column
- Rib cage
- Hyoid bone
The appendicular skeleton consists of what?
- bones of limbs
- pectoral girdle
- pelvis
Bone is derived from?
embryonic mesoderm
Bone’s strength comes specifically from ____________ bone.
compact
What are the other types of bone besides compact bone?
- spongy
- cancellous
Spongy bone has bony spicules (points) known as ____________.
trabeculae
The cavities between trabeculae are filled with bone ____________, which can be red or yellow.
marrow
____ marrow is filled with hematopoietic stem cells.
red
________ marrow is composed of fat and is relatively inactive
yellow
Bones in the appendicular skeleton are typically ________ bones, and are characterized by cylindrical shafts called ____________ that swell at each end to form ____________, and terminate in ____________.
long; diaphyses, metaphyses, epiphyses
The epiphyses use their ________ cores to disperse force and pressure at joints.
spongy
At the internal edge of the epiphysis is an ____________ (growth) plate, which is a cartilaginous structure and the site of longitudinal growth.
epiphyseal
What happens to the epiphyseal plate during puberty?
closes and stops vertical growth
A fibrous sheath called the ____________ surrounds the long bone to protect it and serve as a site for muscle attachment.
periosteum
________ attach muscle to bone, ____________ attach bone to bone.
tendon; ligament
The strength of compact bone comes from the bone ________.
matrix
The organic components of bone matrix are?
- collagen
- glycoproteins
- other peptides
The inorganic components of bone matrix are?
- calclium
- phosphate
- hydroxide ions
What happens to the hydroxide ions in matrix?
They harden together to form hydroxyapatite crystals.
The bony matrix is ordered into structural units known as what?
osteons, or Haversian systems
Each osteon contains concentric circles of bony matrix called ____________ surrounding a central microscopic channnel.
lamellae
Longitudinal channels (axis parallel to bone) are known as ____________ ________
Haversian canals
Transverse channels (perpendicular to bone) are known as ____________ ____________.
Volkmann’s canals
Between lamellar rings are spaces called ____________, which house mature bone cells known as ____________.
lacunae; osteocytes
Lacunae are interconnected by tiny channels called ________________ that allow exchange of nutrients/wastes between osteocytes and Haversian/ Volkmann’s canals.
canaliculi
____________ build bone, and ____________ resorb it.
build; resorb
____________ hormone (released by glands of a similar name in response to low blood calcium) promotes resorption of bone.
parathyroid
____________ hormone (released by glands of a similar name in response to low blood calcium) promotes resorption of bone.
parathyroid
________ ____, which is activated by parathyroid hormone, also promotes the resorption of bone.
Vitamin D
p434
________________, released by the parafollicular cells of the thyroid in response to high blood calcium, promotes bone formation, lowering blood calcium levels.
calcitonin
Cartilage consists of a firm but elastic matrix called ________ that is secreted by cells called ____________.
chondrin, chondrocytes
Cartilage differs from bone how?
- avascular
- not innervated
Most bones are created by the hardening of cartilage into bone. This is called what?
endochondral ossification
Bones can also be formed through ____________ ____________, in which undifferentiated embryonic connective tissue (mesenchymal tissue) is transformed into, and replaced by, bone.
intramembranous ossification
____________ joints consist of bones that are fused together to form sutures.
immovable
Movable joints are strengthened by ligaments and consist of a ____________ ____________, which encloses the actual joint cavity.
synovial capsule
A layer of soft tissue called the ____________ secretes synovial fluid, which does what?
synovium; lubricates movement of structures in joint space.
The ____________ ____________ contributes to the joint by coating the articular surfaces of bones so that impact is restricted to the lubricated joint cartilage, rather than to the bones.
articular cartilage
The end of the muscle with a larger attachment to bone is called the ________.
origin
The end with the smaller attachment to bone is called the ____________
insertion
A ________ muscle decreases the angle across a joint.
flexor
An ____________ muscle increases or straightens this angle.
extensor
An ____________ moves a part of the body away from the midline.
abductor
take away, kidnap
An ____________ moves a part of the body toward the midline.
adductor
A ________ rotator rotates the axis of a limb TOWARD the midline.
medial
A ____________ rotator rotates the axis of a limb away from the midline.
lateral
A ____________ rotator rotates the axis of a limb away from the midline.
lateral
