muscle function Flashcards
What are the three main types of skeletons?
endoskeletons (internal hard parts)
- sponges, echninoderms, bertabrates
Exoskeletons (external hard parts)
- most molluscs, arthropods
Hydrostatic skeletons (lack hard parts)
- fluid help under pressure in a closed body compartment
- most cnidarians, flatworms, nematodes, annelids
Skeletal muscles do what?
work in antagonistic pairs
activity coordinated by nervous system
Hydrostatic skeleton do what?
muscles used to change shape of fluid filled compartments, controlling animal;s form and movement
What is peristalsis?
movement produced by rhythmic waves of muscles contractions from front to back
alternating contractions of circular and longitdudinal muscles
What is the muscle hierarchy of longitudinal units?
1 muscle = several muscle fibres bundles
1 muscle bundle= several muscle fibers
What is 1 muscle fibre made of?
1 muscle fibre has several myofibrils
what is 1 myofibril made of?
1 muscle myofibril has several actin and myosin filaments, arranged in end to end sacromeres
What happens when muscles contract?
Think filaments (myosin) move past think filaments (actin) –> sliding-filament model
filaments remain the same length, but the sarcomeres shorten
muscle contraction cycles need what?
actin binding site on myosin
myosin binding site on actin
ATP
Ca2+
Control of the contraction cycle:
at rest what happens?
myosin binding sites on actin are blocked by tropomyosin
Control of the contraction cycle:
what happens when at AP comes along?
an AP in a motor neuron induces the release of acetylcholine into the neuromuscular junction
Control of the contraction cycle:
the AP releases what ion?
opens voltage gated Ca2+ channels in the sarcroplasmic reticulum releasing Ca into cytosol
Control of the contraction cycle:
Ca released into cytosol does what>?
ca binds to troponin; tropomyosin is pulled off myosin binding sites
ca is pumped back into the sacroplasmic reticulum
Energetics in muscle contraction what is needed?
During the contraction cycle ATP is needed
it is needed to puymp Ca from cytosol back into the SR
What are the four soures of ATP?
ATP pool in muscle fibre
creatine phosphate
glycolisis
oxydative phosphorylation
how is ATP produced from ATP pool in muscle fibres?
only enough for a few contractions (not produced)
how is ATP produced from creatine phosphate?
phosphagen (energy storage) of vertebrates
supplies phosphate group to ADP
how is ATP produced from glycolysis?
splitting of glucose into pyruvate
glucose stored as glycogen
how is ATP produced from oxidative phosphorylation?
production of ATP using energy derived from the redox reaction of an electron transport chain
IN MITOCHONDRIA THE POWER HOUSE OF THE CELL YOU GOT THAT ALEXXXXX
nervous control of muscle tension
What is a motor unit?
motor neuron and all the muscle fibres it controls
each muscle fibres (cell )synapse with only one motor neuron, but each motor neuron can synapse with many muscle fibres
What determines the regulation of contraction strength?
total number of active motor units
number of activated small or large motor units
nervous control of muscle tension:
what are the two ways that the nervous system produces graded contractions?
Varying number of fibres that contract
- recrutment of multiple motor neurons results in stronger contraction
- recruitment of large motor units result in stronger contractions
varying rate at which fibers are stimulated
- a twitch results from a single action potential in a motor neurons
- rapid delivered action poteintials produce graded contractions by sumation
What is tetanus?
maximal, sustained contraction of a skeletal muscle, caused by a very high frequency of APs
What are the two sources of ATP of skeletal muscle fibres?
classified by ATP source and speed of contraction
Oxidative fibers
Glycolytic fibers
What are Oxidative fibres?
rely mostly on aerobic respiration to make ATP
many mitochondria rich blood supply large amounts of myoglobin
dark meat in poultry and fish
glycolytic fiber?
glycolysis primary source of ATP
less myoglobin than oxidative fibers, tires more easily
light meat in poultry and fish
What are the two muscle fibres that are responsible for the speed of contraction?
slow twitch muscles
fast twitch fibers
slow twitch muscle fibres are what?
contract more slowly but sustain longer contractions
ALL oxidative
Fast twitch muscle fibres?
contract more rapidly but sustain shorter contractions
either glycolutic or oxidative
some fast glycolytic fibres can develop into fast oxidative fibres
most skeletal muscles contain both slow and fast twitch muscles in varying ratios
what is the fastest vertebrate muscle?
surrounded swin bladder in male toadfish
produces characteristics mate call
can contract and relax 200x per second
Cardiac muscles?
striated cells electrically connected by intercalated disks
can generate action potentials without neural input
smooth muscles
found mainly in walls of hollow organs like digestice tract
contactions relatively slow and may be initiated by the muscles themsevels or by stimulation from autonomic nervous system
