Chapter 46 Flashcards
What are the three main types of skeletal systems in animals?
hydrostatic skeletons; exoskeletons; endoskeletons
Where are hydrostatic skeletons found primarily? (3)
in soft-bodied terrestrial invertebrates; soft-bodied aquatic invertebrates; squids
Give two examples of soft-bodied terrestrial invertebrates.
earthworms; slugs
Give an example of a soft-bodied aquatic invertebrate.
jellyfish
The fluid-filled central cavity of animals bearing hydrostatic skeletons is supported by what two muscles?
circular muscles; longitudinal muscles
What are circular muscles?
muscles repeated in segments and run the length of the body
What are longitudinal muscles?
muscles that oppose the action of the circular muscles
Which muscles oppose the action of circular muscles?
longitudinal muscles
Describe the locomotion process in earthworms.
anterior circular muscles contract as locomotion begins; this presses on inner fluid; front of body is forced to become thin as the body wall extends forward
What are chaetae?
short, bristle-like structures found on the underside of a worm’s body
What happens to chaetae as circular muscles act?
as circular muscles act, the chaetae are pulled up close to the body and lose contact with the ground, which results in a backward wave of contraction
As the backward wave of contraction in worms continues, what happens?
anterior circular muscles relax and longitudinal muscles take over which allows chaetae to re-establish contact with the ground
Why is chaetae re-gaining contact with the ground important?
it prevents that body section from slipping backwards
In essence, in worms, what is the order of muscle contraction for body movement?
locomotion proceeds as waves of circular muscle contractions are followed by waves of longitudinal muscle effects
What are exoskeletons?
rigid, hard case that surrounds the body
Arthropod exoskeletons are made of
chitin
Other than in arthropod exoskeletons, where can chitin be found?
in the cell walls of fungi and protists
What acts as the skeletal framework for arthropod?
the chitinous exoskeleton
In order to grow, what must an arthropod do to its exoskeleton?
molt it periodically
Molting gives exoskeleton-bearing organisms the disadvantage of
being vulnerable whenever they molt their exoskeleton
What are limitations of exoskeletons? (3)
chitinous framework isn’t as strong as a bony one; ratio between SA of tubules and volume of body overwhelms respiratory system; muscles are confined in size/power
In what organisms are endoskeletons found? (2)
vertebrates; echinoderms
Give two examples of echinoderms.
sea urchins; sand dollars
Echinoderms have skeletons made of
calcite (crystalline form of calcium carbonate)
Give an example of an animal that has a totally cartilaginous skeleton.
sharks
Differentiate between chitin and bone/cartilage.
bone/cartilage are living tissues
T/F: Bone and cartilage can change and remodel themselves in response to injury or stress.
Yes, bone can do so, and to a lesser extent, so can cartilage
What is the main component in vertebrate skeletons?
bone
When did bone first appear?
520 million years ago
Bone is found in all vertebrates except
cartilaginous fishes
In intramembranous development, bones form
within a layer of connective tissue
Give examples of intramembranous mones in the human body. (2)
exterior of skull; jaw
During embryonic development, the dermis is formed largely of (2)
mesechyme; collagen fibers
What is mesenchyme?
loose tissue consisting of undifferentiated mesenchyme cells + other related cells
Undifferentiated mesenchyme cells differentiate to become (in the context of bone development)
osteoblasts
Osteoblasts are derived from
undifferentiated mesenchyme cells
How do osteoblasts arrange themselves?
arrange themselves along collagenous fibers and begin to secrete the enzyme alkaline phosphatase
What is hydroxyapatite?
a crystalline configuration of calcium phosphate salts resulting from the secretion of alkaline phosphatase
What does the enzyme alkaline phosphatase do?
promotes the creation of hydroxyapatite
Undifferentiated mesenchyme cells can differentiate to become what three types of cells?
fibroblasts; chondroblasts; osteoblasts
Fibroblasts differentiate to become
collagen (fibrous tissue)
Chondroblasts differentiate to become
chondrocytes
Osteoblasts differentiate to become
osteocytes
Osteocytes differentiate to become
osteoclasts
What are chondrocytes?
cartilage cells
When does an osteoblast become an osteocyte?
if it becomes trapped in the bone matrix it is constructing, it becomes an osteocyte (bone cell)
Osteocytes reside in spaces called
lacunae
What are osteoclasts?
bone-removing cells
Where are osteoclasts derived from?
fusion of monocytes (white blood cells)
Describe the relative amounts of collagen and hydroxyapatite in bone.
bone contains roughly equal volumes of collagen and hydroxyapatite
What percentage of bone weight is made up of hydroxyapatite?
about 65%
What are canaliculi?
canals extending from lacunae
What cells live in lacunae?
osteocytes
What is the purpose of canaliculi?
promote intercellular communication because the starburst-like extensions of each osteocyte contact their neighbors
T/F: osteoclasts are mononucleate cells.
FALSE, osteoclasts are multi-nucleate cells
Where can endochondrally-developed bones be found in the body?
found deeper in the body because they form the body’s architectural framework
Give examples of endochondrally-developed bones. (6)
vertebrae; ribs; shoulder bones; pelvis bones; long bones of limbs; internal skull bones
Endochondral bones begin as
tiny, cartilaginous models that have the rough shape of bones
Bone added to the outside of the model is produced
in the fibrous sheath that envelopes the cartilage
Describe the fibrous sheath that envelopes the cartilage and adds bone to the outside of the model. (3)
tough; made of collagen fibers; contains undifferentiated mesenchyme cells
What do osteoblasts do in the fibrous sheath that envelopes the cartilage and adds bone to the outside of the model? (2)
osteoblasts arise from the undifferentiated mesenchyme and sort themselves along the fibers in the deepest part of the sheath; bone forms between sheath and cartilaginous matrix
As outer bone is formed, what happens to interior cartilage?
interior cartilage begins to calcify
What is the calcium source for the calcification of interior cartilage as outer bone forms?
the calcium source is the cartilage cells themselves because the cartilaginous tissue breaks down
What is the periosteum?
blood vessels from the sheath
How does growth in bone thickness occur?
by adding additional bone layers just beneath the periosteum
The mammalian humerus is formed of
a slender shaft with widened ends, called epiphyses
What are epiphyses?
widened ends found on bones like the mammalian humerus
What are found within the epiphyses?
epiphyseal growth plates, which separate the epiphyses from the shaft itself
As long as the bone is growing, epiphyseal growth plates are composed of
cartilage
How are epiphyseal growth plates involved in bone elongation? (3)
during growth of long bone, cartilage of growth plates actively grows in lengthwise direction to thicken plate; growth pushes epiphyses farther away from shaft; cartilage calcification encroaches onto growth plate so that bony portion of shaft elongates
Growth in bone length in humans usually ceases by
late adolescence
T/F: growth in bone width is ceased after puberty.
False, growth in width still occurs by bone addition beneath the periosteum
What are vascular bones?
endochondral bones that retain internal blood vessels after completing development
Vascular bone is found in what non-mammalian species? (2)
reptiles; amphibians
Cellular bones contain
osteocytes
T/F: cellular bones can also be vascular.
true, cellular bones can be vascular
T/F: cellular bones are metabolically inactive
false, cellular bones are metabolically active
Avascular bones are found in what species? (2)
fish; birds
Describe avascular bone. (3)
does not contain osteocytes; fairly inert; surface periosteum can repair bone with mesenchyme cells
What is another name for avascular bone?
acellular bone
Bones like the endochondral long bones contain a cavity called
the medullary cavity
Where is the medullary cavity found?
bones like the endochondral long bones
In many vertebrates, the medullary cavity contains
bone marrow, which is important for manufacturing red and white blood cells
If the medullary cavity contains red/white blood cells, it is called the
marrow cavity
Give an example of species whose medullary cavity does not contain marrow.
Light-boned birds
T/F: all medullary cavities contain marrow.
False, not all medullary cavities contain marrow
How do birds produce red blood cells if their medullary cavities don’t contain marrow?
they depend on stem cells to produce RBCs
Bone falls into what three categories?
compact bone; medullary bone; spongy bone
Where is compact bone found?
outer surface
Where is medullary bone found?
medullary cavities
Describe spongy bone.
honeycomb structure; typically forms the epiphyses inside a thick shell of compact bone
Which two types of bone contribute to bone strength?
compact and spongy bone
Medullary cavities are lined with thin tissues called
the endosteum
What is the endosteum?
thin tissue that lines the medullary cavities that doesn’t contain collagen fibers but does contain other stuff like mesenchyme cells
Vascular bone has a special internal organization called
the Haversian system
Endochondral bone is constructed of concentric layers called
Haversian lamellae
Where are Haversian lamellae found?
beneath the outer basic layers
What are Haversian canals?
narrow channels that contain concentric tubes
Haversian canals may contain
nerve fibers
Haversian canals always contain
blood vessels that keep osteocytes alive even though they’re stuck in the bony matrix
What kind of blood vessels can be found in the Haversian canals? (3)
arterioles; venules; capillaries
What are Sharpey’s fibers?
collagen fibers that connect periosteum to bone
T/F: exercise and frequent muscle use can not only alter muscles, but can alter blood vessels, strengthen skeletal frame, etc.
true
T/F: remodeling occurs only in some bones
false, remodeling is known for all bones
Bone remodeling can be considered as what kind of feedback system, and why?
negative feedback system, because stress promotes thicker bones, which reduce the amount of stress that can affect itself, which reduces the need for thickness
What are the effects of osteoporosis?
loss of bone mineral density
Osteoporosis primarily affects
postmenopausal women
What is a treatment for osteoporosis?
weight-lifting, which stimulates bone deposition
What is another name for joints?
articulations
What is another name for articulations?
joints
What are the four basic joint movement patterns?
ball-and-socket; hinge; gliding; combination
Give an example of a ball-and-socket joint.
the hip: the upper leg bone forms the ball and the pelvis is the socket
Describe the movement of the ball-and-socket joint.
can perform universal movement in all directions, plus twisting of the ball
What is the simplest type of joint?
hinge joint
Give an example of a hinge joint.
knee
The knee is what kind of joint?
hinge joint
Describe the movement of the hinge joint.
restricted to rotate forward or backward, but not side-to-side
Where can gliding joints be found? (2)
found in skulls of some nonmammalian vertebrates; found in lateral vertebral projections of vertebrates including mammals
Describe the gliding joint in vertebral projections.
the projections can slip along the undersurface of the posterior projection, which gives stability and flexibility to the vertebral column
What are combination joints?
joints that have characteristics of two or more joint types
Give an example of a mammalian combination joint.
the mammalian jaw, which allows both rotation and side-to-side sliding
What are the two means of bone attachment?
muscle fibers may connect directly to the periosteum; sheets of muscle may be connected to bone by a tendon
What is a tendon?
dense connective tissue cord that attaches to the periosteum
The origin of muscle attachment remains
relatively stationary during a contraction
What is the opposite end of the origin of muscle attachment?
insertion
The quadriceps muscles counter the movement of which muscles?
leg flexor muscles (hamstrings)
Each muscle contains a bundle
of 4 to 20 elongated structures called myofibrils
Each myofibril contains
thick and thin myofilaments
Describe the hierarchy of muscle structures.
skeletal muscle > muscle fibers > muscle fiber cell > myofibril > myofilaments
Describe the appearance of myofilaments under a microscope.
they have alternating light and dark bands
What gives skeletal muscle fibers their striped appearance?
the alternating light and dark bands of myofibrils
What are A bands?
thick myofilaments stacked together that produce the dark bands
Thick myofilaments stack together to produce
dark bands called A bands
Thin filaments are found in
the light bands called I bands
I bands contain
thin filaments
Each I band in a myofibril is divided
in half by a protein disk called the Z lin
What is the Z line?
protein disk that divides the I band in myofibrils in half
What is anchored to Z lines?
thin filaments
What is a sarcomere?
the repeating unit from Z line to Z line
What is the smallest unit of muscle contraction?
the sarcomere
The sarcomere is the smallest
unit of muscle contraction
What is the name for the center of the A band?
the H band
What is the H band?
the center of the A band
Draw out the structure of a repeating sarcomere in relaxed and contracted muscles.
pg. 970 in book
Describe the placement of the thick/thin filaments relative to the A band in relaxed and contracted muscles.
in a relaxed muscle, the thick and thin filaments are on either side of the A band but don’t extend all the way to the center; in a contracted muscle, the thick and thin filaments overlap on each side of the A band
Describe the color of the H band.
lighter than the areas on each side of the A band
T/F: myofilaments shorten during contraction.
FALSE, they don’t shorten, the thick and thin filaments slide relative to each other
What happens to the H band during maximal contraction?
the H band disappears entirely
What happens to the I bands during contraction?
I bands become narrower
What happens to the Z line during contraction?
Z lines are brought closer together
Each thick filament is composed of
many subunits of myosin packed together
The myosin protein is composed of
two subunits, each shaped like a golf club that twist around each other
Each thin filament is composed of
actin proteins arranged into two fibers twisted into a double helix
Myosin is a member of what class of protein?
motor proteins
What do motor proteins do?
convert chemical energy in ATP into mechanical energy
What cycle converts chemical energy in ATP into mechanical energy?
the cross-bridge cycle
What is an individual cross-bridge?
link between a myosin head and an actin molecule
Describe the cross-bridge cycle. (6)
myosin hydrolyzes ATP into ADP+Pi; ADP+Pi remain bound to myosin head which is now energized; myosin binds to actin to form cross-bridge and releases Pi; myosin pulls thin filament towards center of sarcomere in the power stroke; ADP is lost; myosin binds to a new molecule of ATP and is displaced from actin
What is the power-stroke? (2)
when the myosin head pulls the thin filament towards the center of the sarcomere; also when it returns to its original conformation and releases Pi+ADP
What happens in rigor mortis?
the cell can’t produce any ATP and therefore the cross-bridge cycle isn’t broken, which causes muscle stiffness
Describe a relaxed muscle in the context of myosin, ADP, and Pi.
the myosin heads are in the activated conformation bound to ADP and Pi but are unable to bind to actin because the binding site is blocked
What blocks the myosin-actin binding site on the actin molecule?
tropomyosin
Tropomyosin is what type of filament?
thin filament
What is troponin?
a regulatory protein complex that holds tropomyosin and actin together
What does tropomyosin do?
blocks the myosin-actin binding site
The regulatory interactions between troponin and tropomyosin are controlled by
Ca2+ concentrations in the muscle fiber cytoplasm
Describe tropomyosin when Ca2+ levels are low.
When Ca2+ levels are low, tropomyosin inhibits cross-bridge formation
Describe tropomyosin when Ca2+ levels are high.
Ca2+ binds to troponin, which alters its conformation and moves the troponin-tropomyosin complex, which exposes the myosin-actin binding site
Where do muscle fibers store Ca2+?
sarcoplasmic reticulum
What is the sarcoplasmic reticulum?
a modified endoplasmic reticulum that stores Ca2+ in muscle fibers
What happens to a muscle fiber membrane when the muscle fiber is stimulated to contract?
the muscle fiber membrane becomes depolarized
What are transverse tubules?
invaginations of the cell membrane that transmit muscle fiber depolarizations to the SR
Depolarization of the T tubules causes
the SR to release Ca2+, which diffuses into the myofibrils and binds to troponin, allowing contraction
The involvement of Ca2+ in muscle contraction is called
excitation-contraction coupling
Motor neurons that stimulate skeletal muscles are called
somatic motor neurons
The synapses between neurons and muscle cells are called
neuromuscular junctions
T/F: each human muscle fiber has only a single synapse with a branch of an axon.
true
What is the neurotransmitter used for muscle contraction?
acetylcholine
How does the Ca2+ return to the SR?
via a membrane protein using energy from ATP hydrolysis in active transport fashion
What is a motor unit?
set of muscle fibers innervated by all the axonal branches of a motor neuron, including the motor neuron itself
Why is the division of muscle into motor units advantageous?
allows a finer degree of control
What is recruitment?
cumulative increase of numbers and sizes of motor units to produce a stronger contraction
What is summation?
cumulative response of an electric shock after another electric shock of a muscle
What is tetanus?
sustained contraction
Skeletal muscle fibers can be divided on the basis of their contraction speed into
slow-twitch and fast-twitch fibers
Give an example of a human fast-twitch fiber.
muscles in the eye
Give an example of a human slow-twitch fiber.
soleus muscle in the leg
Describe slow-twitch fibers. (4)
rich capillary supply; numerous mitochondria; numerous aerobic respiratory enzymes; high concentration of myoglobin
Which protein is abundant in slow-twitch fibers?
myoglobin
Myoglobin is abundant in which fiber?
slow-twitch fibers
What is the color of myoglobin?
red
What is another name for slow-twitch fibers
red fibers
Which fiber can sustain action of a long period of time without fatigue?
slow-twitch fibers
Describe fast-twitch fibers. (5)
fewer capillaries; fewer mitochondria; not much myoglobin; high glycogen content; many glycolytic enzymes
What is another name for fast-twitch fibers?
white fibers
How do fast-twitch fibers respire?
anaerobically
Skeletal muscles at rest obtain most of their energy from
the aerobic respiration of fatty acids
In what time period to skeletal muscles respire anaerobically?
for the first 45 to 90 seconds of moderate-to-heavy exercise
What is aerobic capacity?
maximum rate of oxygen consumption in the body
What is muscle fatigue?
use-dependent decrease in the ability of a muscle to generate force
Short-term fatigue has been shown to occur because of
a buildup of Pi from the breakdown of creatine phosphate
Long-term fatigue has been shown to occur because of
depletion of glycogen
What adaptation improves physical endurance?
any adaptation that spares the use of muscle glycogen
Does endurance training increase muscle size?
no, endurance training does not increase muscle size
When is muscle enlargement produced?
by frequent periods of high-intensity exercise like weight-lifting
What is another name for type I muscle fibers?
slow-twitch fibers
What is another name for type II muscle fibers?
fast-twitch fibers
What is hypertrophy?
increased cell size
Resistance training increases
the thickness of fast-twitch fibers (muscles don’t grow by cell division)
Locomotion requires what two mechanisms?
propulsive mechanism and control mechanism
What is appendicular locomotion?
locomotion that is produced by appendages that oscillate
What is axial locomotion?
bodies that undulate, pulse, or undergo peristaltic waves
Large animals undergo what two types of locomotion?
appendicular or axial locomotion
How does aquatic mammal locomotion differ from fish locomotion?
waves pass from top to bottom instead of side to side
What is another name for top-to-bottom flexing?
dorsoventral flexing
How do mollusks locomote?
by secreting a mucus that they glide along using a muscular foot
How many times has convergent evolution of flying occurred?
4 times - 1 in insects, 3 in vertebrates
Describe air pressure around a wing.
top of the wing has lower pressure, bottom of the wing has higher pressure
