Chap 26 The Skeletal and Muscular Systems Flashcards
The muscular system and the skeletal system function…?
together
What does the muscular system provide?
motion
How does the muscular system provide motion?
muscle cells contract when stimulated by the nervous system
What does the skeletal system provide?
adds a firm supporting structure that muscles pull against
What are the organs of the vertebrate skeleton?
bones
What are the two categories bones are grouped in?
axial skeleton
appendicular skeleton
What is the axial skeleton?
surrounds the central axis of the body
What is the appendicular skeleton?
consists of the appendages and the bones that support them
What does the axial skeleton do?
shields soft body parts (e.g. skull, ribs, vertebrae)
What does the appendicular skeleton do?
consists of limbs
What does the vertebrate skeleton feature?
a central backbone
What protects and supports the spinal cord?
the vertebral column
What protects the heart and lungs, and is attached to the vertebral column?
ribs
What happens to the vertebral column in scoliosis?
it curves to the side
What provides useful clues to past events?
bones
What can bones reveal about the past?
gender of a person
illnesses
evolution
What are the different functions of bones?
support and protection
bones connected to muscles provide movement
bone mineral supply calcium and phosphorus to the rest of the body
blood cells form at the marrow inside the bones
Where do bones produce new blood cells?
in the marrow
What is the marrow cavity?
a space occupying the center of the bone shaft
What is a nursery for blood cells and platelets?
red bone marrow
What replaces red marrow in adult limb bones?
yellow bone marrow
What is yellow bone marrow unable to do?
produce blood (but it can revert to red marrow if necessary)
What do bones contain?
nerves
blood vessels
cartilage
T/F bones are living organs.
True
Canals throughout the bone house what?
veins
arteries
nerves
Besides bone, what is the other main connective tissue in the skeleton?
cartilage
Where is cartilage located?
covering the ends of bones
What does cartilage consist of?
mostly tough, elastic proteins
Cartilage resists what?
breakage and stretching (even when bearing great weight)
Cartilage can also act as an excellent?
shock absorber
Where does the skeleton begin?
cartilage
What happens to bone and a fetus develops?
bone tissue replaces cartilage
What continues to happen to the bone as the person matures?
bones continue to develop after birth as the bone matrix becomes materialized
In children, where does bone growth continue?
at growth plates made of cartilage
Where do bones meet?
at a joint
What are tendons?
tough bands of connective tissue that attach bone to muscle
What are ligaments?
similar to tendons and attach bone to bone
What is a joint?
an area where two bones meet, allowing for movement
Bones are surrounded by what, that allows bones to move against each other without friction?
fluid-filled capsule of fibrous connective tissue
Bones help regulate what?
calcium homeostasis
The body maintains calcium homeostasis under the control of what?
hormones
How does the body maintain calcium homeostasis?
by constantly shuttling calcium between blood and bone
What is calcium vital for?
muscle contraction
blood clotting
the activity if certain enzymes
What is osteoporosis?
the loss of calcium from bone tissue, which weakens the bone
Muscles have multiple what in the body?
functions
The human muscular system includes more than …. , which carry out various functions in addition to voluntary movement?
600 skeletal muscles
Which muscles are involuntary, and thus are not typically considered part of the muscular system?
smooth muscle
cardiac muscles
What are the different functions of muscles?
voluntary movement
control of body openings
maintain posture
communication
maintain body temperature
Muscles have what?
a hierarchical organization
What is a muscle?
an organ enclosed in connective tissue, nourished by blood vessels, and controlled by nerves
Muscles contain many what, made of thick and thin filaments?
myofibrils
Myofibrils are made up of what?
filamentous contractile proteins, actin and myosin
Thin filaments have which protein?
actin
Thick filaments have which protein?
myosin
Actin and myosin do what next to each other?
slide past each other
According to what, a muscle cell contracts when thin filaments slide between thick ones?
sliding filament model
What are the basis of muscle movements?
interactions described in the sliding filament model
Each long myofibril is divided in chunks, or function units called?
sarcomeres
What happens to sarcomeres when a muscle cell contracts?
sarcomeres become shorter
The motion that occurs as the contractile proteins slide past each other shortens each sarcomere without changing what?
the lengths of the thick or thin filaments
What makes the sliding motion possible?
ATP
What is step 1 of allowing the sliding motion?
actin and myosin filaments are near each other but not touching
What is step 2 of allowing the sliding motion?
the muscle cell has received an impulse from the nervous system, myosin binds to actin, forming cross bridges
What is step 3 of allowing the sliding motion?
the cross bridge changes shape from straight to bent. This “power stroke” pulls on the actin filament
What is step 4 of allowing the sliding motion?
ATP binds to the cross bridges, which causes them to separate from the actin binding sites
What is step 5 of allowing the sliding motion?
hydrolysis of ATP provides the energy to return myosin to its straight conformation
What stimulate muscle contraction?
motor neurons
What do motor neurons do?
send impulses from the central nervous system to muscle cells, causing them to contract
One motor neuron typically what?
synapses with several muscle cells, forming motor units that all contract together
What allows actin and myosin to interact?
calcium ions
What is step 1 in allowing actin and myosin to interact?
neurotransmitters cause opening of ion channels in the muscle cells
What is step 2 in allowing actin and myosin to interact?
this causes accumulation of calcium ions in the cytosol
What is step 3 in allowing actin and myosin to interact?
calcium ions change the shape of the thin filaments, allowing the myosin heads to bind to actin
Muscle cells have several ways to produce what?
ATP
What is the first way ATP can be produced?
ATP is generated in aerobic respiration and during muscle activity
What is the second way ATP can be produced?
ATP can be directly replenished with the help of a molecule called creatine phosphate
What is the third way ATP can be produced?
when the creatine phosphate supply is depleted, aerobic respiration continues to produce ATP as long as muscles are receiving enough oxygen
What is the fourth way ATP can be produced?
otherwise, the cells switch to fermentation, an anaerobic pathway of ATP production that generates lactic acid as a byproduct
What are the two types of muscle fibers?
slow-twitch
fast-twitch
What are slow-twitch fibers?
small, use energy slowly, have high endurance
What are fast-twitch fibers?
large, use bursts of energy, tire quickly
The proportion of muscle fibers influences what?
athletic performance
People with a high proportion of slow-twitch fibers excel at what?
endurance sports
People with a higher proportion of fast-twitch fibers excel at what?
short, fast events
The proportion of muscle fibers is influenced by what?
genetics and exercise
What do genes determine in muscles?
the fast/slow twitch ratio
Is is possible to alter the fast/slow twitch ratio through exercise?
yes
Exercise also does what to muscles?
increases the size of muscle cells
increases the efficiency of muscle metabolism
increases the blood flow to muscles
increases bone strength
