what are the three types of muscle and their function?
skeletal, cardiac, and smooth
muscles store energy to contract and relax, provide muscle tone, hold body fluids, regulate heat
What is muscle made of?
skeletal muscle tissue, nervous tissue, blood connective tisse
Connective tissue coverings...
enclose and sepparate muscle cells/fibers
the type of connective tissue that sepparate and provide structure to each muscle. they form tendons which connect the muscle to the bone
another type of connective tissue that connects muscles to bones
fascia > epimysium which surrounds the muscle, perimysium which sepparates the muscle into small compartments that holds the muscle fibers> which are covered by the endomysium
What is a muscle fiber?
a cell that makes the muscle contract when stiumulated, and then relaxes when the stimulation is over
What is the structure of a muscle fiber?
thin and elongated, covering the muscle
contains membrane and cytoplasm, also called the sacroplasm> which hold the protein filaments myofibrils, actin(thin) and myosin(thick) which produce bonds and striations
How do the filament bands connect?
the I bands, actin, connect to the Z line, myosin, and the A bands of myosin overlap the actin bands so both are always touching
What two structures are in the sacroplasm?
the T tube, or the transverse tubules and the sacroplasmic recticulum channels
the t tubes extend inwards and then open up to the outside and hold the excracellular fluid; once the muscle fiber is stimulated, the Ttube and the SR. initiate muscle conntraction
this axon extends form the brain/spinal cord and is connected to the muscle fiber, which only contracts when the motor neuron is stimulated
What is a neuromuscular junction?
the place where the motor neuron and the muscle fiber meet
Motor end plate
formed by the motor neuron and muscle fiber, the end of the muscle fiber is folded in so the motor neuron can project into the muscle fiber easily
chemicals stored in the motor neuron axons , once a nerve impulse reaches the brain or spinal cord and the neurotransmitter is released into the motor end plate a muscle contraction has begun
What is a motor unit?
the motor neuron and the muscle fiber it controls make up a motor unit, several muscle fiber movements make a contraction
is a type of neurotransmitter that can stimulate muscle contraction, this chemical is held at the end of the motor neuron axon
What is essentially happening during muscle contraction?
myosin and actin are interacting so that one is sliding past another, which shortens the muscle fiber making it pull on near by attachments (the shortening of the sacromere)
What other proteins are assosiated with actin when it wants to bind with myosin?
troponin and troponmyosin
What does ATPase do?
it breaks down ATP, ADD, and phosphate, which makes the myosin bind to the actin, releasing energy that puts the myosin brige in a 'cocked' position
Sliding filament model
the cycle of muscle contraction , sacromeres becoming shorter because cross bridges on the thin filaments, happens repeatedly as long as there is ATP and as long as muscle fibers are able to contract
this enzyme breaks down the acetylcholine that stimulated the contraction, preventing nerve impulses from continuously contracting the muscle fiber, found in the motor end plate
What do most contractions require?
ATP and acetylcholine
Steps of muscular contraction
nerve impulse>stimulates neurotrasnmitter> releases acetylcholine> message is carried into the cell membrane (sarcolemma) and through the t-tubes >sarcoplasmic reticulum> once muscle impulse is here, calcium ions are released into the sacroplasm> calcium ions bond w/ troponin> which connects with tropomyosin> expose the binding sites of actin> making actin and myosin bond by pulling on one another=muscle contraction
What two steps lead to relaxation?
1st= acetylcholine is decomposed by the enzyme acetylcholinesterase, preventing nerve impulses
2nd=calcium ion concentration decreases, back into the sarcoplasmic reticulum, breaking bonds between the actin and myosin
Energy sources for contraction
ATP, creatine phosphate, cellular respiration
main source of energy used for concentration, scince it is used for everyday life, it is in high demand, so it needs to be regenerated...
uses decomposed ATP and from creatine phosphate itself to transfer ADP into ATP, stores and creates atp
yeilds ATP, but really wants oxygen for the muscles to break down glucose in the mitochondria to make atp
How do muscles get oxygen and what two pigments carry them?
blood can go to the muscles carrying oxygen by hemoglobin, and myoglobin carry oxygen in blood that is required for muscular contraction
how does one obtain energy?
glucose is broken down > creating pyruvic acid>produces lactic acid > demands ATP and glucose to break down the lactic acid
the amount of oxygen required after physical exercise to convert accumulated lactic acid to glucose, it takes time to fix the debt because breaking down lactic acid into glucose takes time
when a muscle looses its ability to contract, this happens during stenuous activity, interruption in the muscles blood flow, lack of acetylochine in motor neuron, or from a large amount of lactic acid from aaerobic respiration. it lowers pH and muscle fibers wont respond to stimulation
an involentary reaction due to extracellular fluid surrounding muscle fibers/motor neurons trigger stimulation of the fiber
muscles provide the body with heat because muscles are such a large part of our body
blood also transports heat in muscles to other tissues to help the body maintain a healthy temp
the minimum stength to initiate a contraction; the motor neuron releases enough acetylcholine to bring the fiber to a threshold state
all or none response
once a muscle fiber contracts, the intensity of the stimulation doesnt matter, because contractions either occur or they dont, there is no half way or partial contraction
the machine that records muscle contractions or movements by connecting the fiber to a lever and tracing its pulling patterns
a single contraction that lasts a second and then relaxes (threshold, then relax)
the delay between the stimulation and the time it takes for a muscle to respond, which is followed by a period of contraciton and relaxation before it occurs again
a state where muscle fibers reach a point where they are unable to fully relax before the next stimulation
continuous, forceful muscular contraction without relaxation
when motor units in a given muscle contract with maximal tention (generally speaking, motor neurons control an area of motor units, making them all contract at once, but whole muscles dont respond like this because different motor neurons in the muscle have different threshold rates)
what factors effect the intensity of a muscle contraction?
twitches and increase recruitment of motor units, for example, smaller units respond to stimulation easily and earlier, while larger motor units respond later and more forcefully
summation and recruitment together produce this contraction of increasing strength which enables us to participate in everyday activities
a response to nerve impulses that originate from the spinal cord and stimulates muscle fibers, helps maintain posture-contracts when muscles appear to be at rest
they have myosin and actin like skeletal muscles, but are less organized, so they are not striated.
2 major types: visceral and multiunit
involentary, non striated,
occurs in sheets and is in the walls of hallow organs; these fibers can stimulate each other and display rhythmicity, responsible for moving subtances in the organs of their length (stomach)
smooth muscle, such as in the blood vessels and iris of the eye, fibers are separate rather then sheets
smooth muscle contraction similarities with skeletal muscle
uses myosin and actin, triggered by impulses and an increase in calcium ions, uses energy fro ATP
smooth muscle contraction differences from skeletal muscle
two neurotransmitters are used: acelycholine and norepinephrine (both stimulate and inhibate) hormones also affect s.m. they are slower to contract and relax but can maintain a forceful contraction longer with the given ATP
-also they change length: stomach walls with smooth muscle must change length, but can still maintain the pressure
only found near heart, involentary & striated
difference: muscle fibers are less developed and store less calcium, but the t tubes are longer allowing them to release more calcium in response to an impulse
twiches are longer due to the extracellular liquid
what are intercalated discs and what do they do?
they connect cardiac muscle and they help join cells to make contraction between cells stronger and they allow impulses to travel freely
also self exciting and rythmic
muscle movement depends on the type of joint the muscle is connected to and the way the muscle attaches to that joint
bones forming a movable joint, skeletal muscles connect to an immovable part of a joint and a movable part
this is the immovable part of the joint
the movable part of the joint, when a muscle contracts, the insertion moves to the orgin
decrease the angle
increase the angle
muscle that has the principal responsibility for a given movement or called the agonist
muscles that contract to assist the prime mover
muscles that resist the prime mover actions to cause movement in the opposite direction, however, antogonists and prime movers work together for a sucessful muscle movement
volentary, striated, superficial
three kinds of skeletal muscle fibers
red/slow, red/fast, and white/fast
contains myoglobin, contracts slowly, atp from mitochondira, small diameter and capillaries
contains myoglobin, the middle between red/slow and white/fast
no myoglobin, thicker diameter, fewer capillaries, contract quickly, fatigue easily atp from glycolysis