Exam 3 Homework Questions
statements about excitation-contraction coupling
-Relaxation requires uptake of calcium ions by the sarcoplasmic reticulum. -Tropomyosin moves to expose myosin binding sites on actin. -Calcium ion is released from the sarcoplasmic reticulum. -Troponin binds calcium ion and signals tropomyosin to move
Which of the following would be a way that PTH could alter plasma levels
-increase osteoclasts -increase reabsoprtion of calcium in the kidney
what are some functions of the skeletal system
-maintain body temperature -produce movement -maintain posture -guard body entrances and exits
the periosteum contains
-sensory nerves -lymphatic vessels -blood vessels
Put the following steps of fracture repair into the correct order. 1. Extensive bleeding occurs. 2. An internal callus forms from a network of spongy bone. 3. Hematoma is formed to close off blood flow. 4. Remodeling continues by osteoblasts and osteoclasts leaving little evidence of the break. 5. Osteoblasts replace the central cartilage of the callus.
1,3,2,5,4
bone is composed of __percent bone
2
The following are important steps in the process of endochondral ossification. 1. Blood vessels grow around the edges of the cartilage and perichondrium differentiates into osteoblasts. 2. Capillaries and osteoblasts migrate to the epithyses forming the secondary ossification centers. 3. Chondrocytes enlarge and the surrounding matrix begins to calcify. 4. Remodeling continues and the shaft becomes thicker. 5. Blood vessels penetrate the cartilage and invade the central region forming the primary ossification center
3, 1, 5, 4, 2
The following are major steps in the process of intramembranous ossification. 1. Clusters of osteoblasts form osteoid that becomes mineralized. 2. Osteoblasts differentiate within mesenchymal connective tissue. 3. Spicules of bone radiate out from the ossification centers. 4. Mesenchymal cells aggregate.
4, 2, 1, 3
the region of the sarcomere containing the thick and thin filaments is the
A band
The muscle tissue in the meat would probably not become stiff after death if it still had enough
ATP
What molecule supplies the energy for a muscle fiber contraction?
ATP
The intestinal response to PTH secretion when calcium ion levels are low is that calcium is
Absorbed quickly
Define appositional growth
Appositional growth is an increase in bone diameter due to the addition of bone matrix at the bone's outer surface
The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur?
Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate (junctional folds of the sarcolemma) and sodium enters the cell.
Which of the following is formed by intramembranous ossification
Both the roof of the skull and the clavicle
How do calcium ions (Ca2+) in the sarcomere affect the contraction cycle?
By binding to troponin, Ca2+ causes it to shift position and move tropomyosin, exposing the binding sites on actin.
Elevated levels of calcium ion in the blood stimulates the secretion of the hormone
Calcitonin
Which of the following hormones is currently thought to decrease plasma calcium levels in pregnant women and children
Calcitonin
Which hormone works directly in the intestine to increase plasma calcium levels
Calcitriol
What event initiates the contraction cycle?
Calcium ions arrive within the zone of overlap.
What causes calcium to be released from the sarcoplasmic reticulum?
Calcium is released when an action potential reaches the triad
Endochondral ossification begins with the formation of a
Cartilage model
Define depolarization, and describe the events that follow it.
Depolarization is the when the inside of the cell becomes positive due to sodium ions rushing in. After depolarization, repolarization occurs when potassium ions rush out of the cell causing the inside of the cell to become negative again.
During intramembranous ossification, bone replaces which type of tissue
Embryonic or fibrous connective tissue
Which structure allows a bone to grow in length
Epiphyseal cartilages
What is the general function of an excitable membrane?
Excitable membranes permit rapid communication between different parts of a cell
List the steps involved in fracture repair, beginning just after the fracture occurs
Fracture hematoma formation, callus formation, spongy bone formation, compact bone formation
Compare gigantism with acromegaly
Gigantism results from an overproduction of growth hormone before puberty whereas acromegaly results from an overproduction of growth hormone after puberty
When cartilage is produced at the epiphyseal side of the metaphysics at the same rate as bone deposited in the opposite side, bones
Grow longer
Bill, age 15, is still growing, but his older sister Andrea, age 19, has stopped. What has changed in Andrea's bones?
Her epiphyseal plates have ossified
A hard ossified bone in an adult actually begins within the embryo as a miniature version composed of
Hyaline cartilage
the region of the sarcomere that always contains only thin filaments is the
I band
Which organ prevents calcium loss in response to PTH stimulation
Kidney
When the epiphyseal plate is replaced by bone
Long bones have reached their adult length
Which condition, due to excessive cartilage formation at the epiphyseal cartilages, results in individuals who are very tall, with long, slender limbs
Marfan syndrome
In intramembraneous ossification, which cells first cluster together and start to secrete the organic components of the matrix
Mesenchymal cells
What chemical changes most likely happen during aging to make meat regain its tenderness?
Myofilaments decompose and break down
The opening in the diaphysis through which blood vessels provide oxygen to osteons is named the ___ foramen
Nutrient
Cells of the perichondrium need to take on a new role as ossification begins. They will become
Osteoblasts and begin to deposit bone matrix
Identify the hormone that stimulates the release of calcium ions from bone matrix. Explain it's mechanism of action
Parathyroid hormone; increases osteoclasts break down of bone matrix
Which is true regarding events that occur at neuromuscular junctions?
The binding of acetylcholine molecules to the receptors alters the membrane's permeability.
Which of the following events must happen for the movement of the thin filament toward the M line (the center of the sarcomere)?
The myosin head binds to the active site on actin and pivots toward the M line.
What happens immediately after the myosin head binds to the active site on actin?
The myosin head pivots, moving the actin strand
The interaction between the contractile proteins repeats over and over during a single contraction of a muscle cell. Which of the following choices allows the repeated separation and reactivation of the myosin head?
The presence of ATP
As blood vessels extend into spaces left by dying chondrocytes, the models begin to ossify internally. Where does internal ossification begin?
The primary ossification center in the diaphysis
Explain why the propagation of action potentials along electrically excitable membranes occurs in only one direction
The refractory period prevents it from propagating back in the direction from which it began
Which of the following statements regarding the homeostasis regulation of blood calcium is FALSE?
The three main organs that serve as the site for the regulation of blood calcium levels are the bones, the intestines, and the pancreas.
Which of the following statements is not true about action potentials
They can travel in two directions
define aponeurosis
a broad collagenous sheet that connects skeletal muscle to a broad area on one or more bones
define tendon
a bundle of collagen fibers that connects a skeletal muscle to a bone
In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter?
acetylcholine (ACh)
Triggering of the muscle action potential occurs after
acetylcholine binds to chemically gated channels in the motor end plate membrane
A myosin head binds to which molecule to form a cross bridge?
actin
Myosin molecules form cross-bridges when they attach to __________.
actin
Which of the following proteins contains the active site involved in cross-bridge formation?
actin
The most important factor in decreasing the intracellular concentration of calcium ion after contraction is
active transport of calcium back into the sarcoplasmic reticulum.
What causes the vesicles inside a neuron to fuse with the plasma membrane?
an action potential in the neuron
What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell?
arrival of an action potential
What causes the myosin head to disconnect from actin?
binding of ATP
the central canal of an osteon contains
blood vessels
during appositional gorwth
bones grow wider
osteocytes are embedded in a dense matrix of hydroxyapatite. Which of the following describes how osteocytes receive nutrients?
by dissusion from nutrients released from, vessels in the central canal that travel through canaliculi
PTH promotes the formation of which hormone?
calcitriol
In response to action potentials arriving along the transverse tubules, the sarcoplasmic reticulum releases
calcium ions
___accounts for almost two-thirds of the weight of bone
calcium phosphate
___are stronger than steel when stretched
collagen fibers
describe the function of the medullary cavity
contains the red and yellow bone marrow
physical evidence that supports the sliding filament theory of muscle contraction include
decreased width of the H band during contraction
During the ________ phase of action potential development, voltage-gated sodium channels are open.
depolarization
ATP binding leads to which of the following actions?
detaching and resetting cross-bridges
the lining of the medullary cavity is called the
endosteum
Where does endochondral lengthening occur
epiphyseal line
What means of membrane transport is used to release the neurotransmitter into the synaptic cleft?
exocytosis
where is the articular cartilage found, and how is it nourished
found covering both epiphyseal portions of articulating bone and nutrients diffuse from synovial fluid within the joint
muscle fibers differ from "typical cells" in that muscle fibers
have many nuclei
as bone increase in diameter, what happens to the medullary cavity?
increases in diameter because bone matrix is removed by osteoclasts
remnants of oesteons, which have been almost completely recycled by osteoclasts are known as
intersitial lamellae
how is the H band distinguished from the other prominent structural features of the sarcomere
it is a lighter region that contains thick filaments, but no thin filaments
summarize the sliding filament theory
it is the process of sarcomere shortening caused by the sliding of thin and thick filaments past each other
why is the zone of overlap important region of the sarcomere
it is where the myosin heads can interact with the thin filaments
Myofibrils are __________.
made of a series of sarcomeres
The Na+/K+ ion pump is responsible for
maintaining the sodium/potassium concentration gradients constant.
Neurons and ________ have electrically excitable membranes that propagate action potentials.
muscle cells
interactions between actin and myosin filaments of the sarcomere are responsible for
muscle contraction
The neuromuscular junction is a connection between a neuron and a __________.
muscle fiber
determine the correct structural hierarchy of skeletal muscles from microscopic to gross levels
myofibril-fiber-fascle-muscle
__ are stem cells located between the endomysium and sarcolemma that function in the repair of damaged muscle tissue
myosatellite cells
Which of the following is involved in the power stroke?
myosin
Acetylcholine receptors are primarily located __________.
on the motor end plate
cells that secrete the organic components of the bone matrix are called
osteoblasts
___free calcium from bone to amintain blood calcium levels
osteoclasts
cells that are found in small depressions on the endosteal surfaces are the
osteoclasts
the lacunae of the osseous tissue contain
osteocytes
the most abundant cell type in bone is
osteocytes
____cells, which differentiate into osteoblasts, are located in the endosteum and inner cellular layer of the periosteum
osteogenic
the structural units of mature compact bone are called
osteons
Curare is a poison that prevents acetylcholine from binding to acetylcholine receptors. Which of the following is the most likely cause of death from curare exposure?
paralysis of skeletal muscles
nerves and blood vessels that service the muscle fibers are located in the connective tissues of the
perimysium
Which of the following is an ion that is more concentrated inside the cell than outside?
potassium
the advantage of having many nuclei in a skeletal muscle fiber is the ability to
produce large amounts of the muscle proteins needed for muscle contraction
Prior to the death of the cow that the meat came from, the living skeletal muscle cells used energy (hydrolyzed ATP) in order to
reactivate myosin heads
What causes the power stroke?
release of ADP and Pi
The role of acetylcholinesterase in the neuromuscular junction is to __________.
remove acetylcholine from the synaptic cleft
If potassium channels were blocked, the ________ phase of the action potential would not occur normally
repolarization
the repeating contractile unit of skeletal muscle fiber is the
sarcomere
Z lines define the edges of which of the following?
sarcomeres
Excitation-contraction coupling is the
sequence of processes that links the action potential to contraction.
since each myofibril is attached at either end of the muscle fiber, when the sarcomeres shorten, the muscle fiber
shortens
How is acetylcholine (ACh) removed from the synaptic cleft?
simple diffusion away from the synaptic cleft and acetylcholinesterase (AChE; an enzyme)
the type of bone that is adapted to withstand stresses that arrive from many directions is ___ bone
spongy
what best describes the sarcoplasmic reticulum
storage and release sites for calcium ions
The end of a neuron that contains acetylcholine-filled vesicles is called the __________.
synaptic terminal
where would calcium ions be predominately found
terminal cistera
The action potential on the muscle cell leads to contraction due to the release of calcium ions. Where are calcium ions stored in the muscle cell?
terminal cisterns (cisternae) of the sarcoplasmic reticulum
if osteoclast activity exceeds osteoblast activity in a bone, how will bone mass be affected
the bone mineral content will decrease and thus bone mass will decrease
Which of the following is greater?
the concentration of calcium ion in the sarcoplasmic reticulum of a resting muscle
membrane potential is
the electrical gradient of a cell
describe the connective tissue layers associated with skeletal muscle tissue
the epimysium surrounds the entire muscle; the perimysium divides the skeletal muscle into fasciles; the endomysium surrounds individual muscle fibers
An action potential in the muscle fiber causes __________.
the muscle fiber to contract
what special terms are used to describe the plasma membrane and cytoplasm of a skeletal muscle fiber
the plasma membrane is called the sarcolemma and the cytoplasm is called the sarcoplasm
What is the synaptic cleft?
the space between the synaptic terminal and the motor end plate
Myosin molecules form what part of the sarcomere?
thick filament
which structural features of spongy bone are oriented along stress lines and are cross-braced extensively?
trabeculae
The action potential is conducted into a skeletal muscle fiber by
transverse tubules
When the sarcomere is at rest, what is covering the active sites on actin?
tropomyosin
at rest, active sites on the actin are blocked by what
tropomyosin molecules
The binding of calcium to which molecule causes the myosin binding sites to be exposed?
troponin
When calcium is released inside a muscle cell, what does it bind to?
troponin
which thin filament-associated binds two calcium ions
troponin
at rest, the tropomysoin molecule is held in place by
troponin molecules
define transverse tubules
tubular extensions of the sarcolemma that extand into the sarcoplasm contracting the terminal cisternae of the sarcoplasmic reticulum
Inside a neuron, acetylcholine is contained within __________.
vesicles
When an action potential arrives at the axon terminal of a motor neuron, which ion channels open?
voltage-gated calcium channels
which of the following best describes the term "Z" line
where thin filaments are anchored
