Date post: | 18-Jan-2016 |
Category: |
Documents |
Upload: | conrad-mckinney |
View: | 220 times |
Download: | 0 times |
Ch 39.1 p.718
Ch 39.2 p.720
Ch 39.3 p.727
Skeleton UseProtectionSupportMovementStorage for ionsProduction of blood cells
Types of SkeletonsHydrostatic- “water standing”
can be fluid-filled gastrovascular cavityfound in Cnidaria and Platyhelminthes
analogy: stiff garden hose Organisms: worms, jellyfish, sea anemones, etc.
Earthworms-septa Muscle fibers at base of epidermal cells contract
body/tentacles shorten quickly=movement Muscular hydrostat-certain parts are helped to be
moved by “fluid contained within certain muscle fibers.” e.g. spider legs, elephant trunks
Exoskeleton- outerOrganisms: molluscs, arthropods, and
vertebrates Primarily for protection against outside predators
and environmentCalcium Carbonate shell in molluscs that can
grow with them. i.e. snails, clamsChitin, a “flexible nitrogenous polysaccharide”
in arthropods. i.e. insects allow for flexibility Arthropods must molt vulnerability (during the
waiting period while the new exoskeleton hardens and dries)
Endoskeleton- innerOrganisms: vertebrates and echinoderms e.g.
starfish Primarily for support and movement and protection
of vital organsSpicules and plates of calcium carbonateVertebrate endoskeleton=living tissueGrows with animal but molting is not neededCan support weight while leaving spaceJoints allow for complex movements
MovementMuscles = force by contractionTendons are what attach the muscles and
bonesBones = anchorage and levers change size
or direction of force by musclesLigaments are what connect bones and help
prevent dislocationNerves are what send messages from brain to
muscles to tell to contract and move at certain times and extents
JointsJunctions between bonesParts:
Cartilage-smooth tough tissue-bone friction reducer
Muscle-for bending, straighteningBones-lever, anchor, and forceSynovial fluid-joint lubricator Joint capsule-joint seal and holds in fluid
Like a bottle cap
Difference in MovementsHip joint
Movement in three planes Protraction/retraction, abduction/adduction, and
rotation
Knee JointHinge jointA lot of movement in one plane
Flexion/extension
What are Muscles? Muscles are bundles of tissue that are attached to bone
by tendons and are essential for movement Muscles provide the force for movement by working in
antagonistic pairs This means that when one muscle contracts, the other relaxes,
and vice versa Muscles are made of muscular tissue and involve three
types: Skeletal muscle, or striated voluntary muscle, is responsible
for posture, support, and movement. It also helps maintain homeostasis by keeping constant body temperature as well as releasing heat stored in the body by breaking ATP during contractions
Smooth muscle, or non-striated involuntary muscle, which contracts automatically. It is found in the digestive tract, respiratory tract, iris, and arrector pilli of the skin
Cardiac muscle, which is found specifically in the heart; it is responsible for heart contractions in order to pump blood to the rest of the body
Macroscopic Anatomy and Physiology There are about 700 different skeletal muscles in the body,
all of which make up about 40% of the body weight of an average human (point out some superficial muscles) Skeletal muscles attach to the skeleton by tendons Muscles shorten when the contract; they cannot lengthen
They can only push, not pull, and must therefore work in pairs (ask for volunteers)
Rapid stimuli can cause muscles to respond to subsequent stimuli without relaxing completely
(fishing pole analogy) Repeated stimulation causes increasing contraction until it
reaches the maximum sustained contraction, called tetanus
Even when they appear to be at rest, some muscles exhibit tone, which is when some of the fibers are still contracted
If all muscles went slack, people would just collapse
Microscopic Anatomy and Physiology Structure of skeletal muscles
Skeletal muscles are composed of bundles of muscle fiber, containing special components
The sarcolemma is a plasma membrane for muscle cells
The muscle fibers have modified endoplasmic reticulum, called sarcoplasmic reticulum, which serve as storage sites for calcium ions needed in contractions
The sarcoplasmic reticulum contains up to thousands of myofibrils, which are the part of the muscle fiber that contract
Myofibrils have light and dark bands (called striations) caused by the placement of protein filaments inside of contractile units called sarcomeres
Sarcomeres extend between two dark lines called “Z lines”
There are two types of filaments: thick, make of myosin, and thin, made of actin
The “I band” is light because it contains only actin
The darker “H zone” contains only myosin The “A band” contains overlapping actin and
myosin, so it is the darkest
Sliding Filament Model
Contracted muscle fibers show that sarcomeres within myofibrils are shortened When sarcomeres shortened, the actin slide
past the myosin and toward each other The “I band” then shortens and the “H zone”
basically disappears *NB: the sarcomere gets shorter, but the filaments
themselves remain the same length ATP supplies energy for the reaction; myosin
filaments are the ones that actually do the work and break down ATP to form cross-bridges that attach to and pull actin filaments to the center
ATP ATP provides the energy for muscle contraction
Although muscle cells contain myoglobin, an oxygen-storing molecule, cellular respiration does not necessarily supply all of the needed ATP
Therefore cells rely on phosphocreatine, a storage form of high-energy phosphate
Phosphocreatine does not directly participate in muscle contraction, but instead regenerates ATP in the following equation: creatine-P + ADP ---> ATP + creatine
*NB: Phosphocreatine and creatine phospate are the same After all of the phosphocreatine is used, the mitochondria will
then produce the required ATP for muscle contraction If not, then fermentation will occur, which causes the buildup of
lactate after a short period of time Hard breathing after exercise gathers the necessary oxygen to
complete the metabolism of lactate to restore cells to their original energy state (this is known as oxygen debt)
The lactate is transported to the liver, where about 20% of it is broken down into carbon dioxide and water to gain ATP in order to reconvert the remaining 80% of lactase into glucose
Muscle Innervation Muscle innervation refers to when muscles are stimulated to
contract by motor nerve fibers Nerve fibers have several branches that end in axon terminals that
lie very close to the sarcolemma; they are separated by a small gap called the synaptic cleft The entire region is called a neuromuscular junction
The terminals contain vesicles that hold the neurotransmitter ACh (acetylcholine), which is released when nerve impulses travel down the motor neuron and to the axon The ACh diffuses into receptors in the sarcolemma which
generates impulses that spread into the sarcoplasmic reticulum, causing the release of calcium ions
The calcium causes the sarcomere filaments to slide past one another, causing contraction of the sarcomere, resulting in myofibril contraction, then muscle fiber contraction, then contraction of the muscle itself
Once ACh is relased into the junction and created a response, it is removed
Acetylcholinesterase (AchE) breaks down ACh
Human Skeletal SystemCartilage included in most bones
Bibliography