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what do you know about Involuntary movements? (Hint 3 points)
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Terms in this set (61)
Cardiac Muscle - length ? - Type of nucleus ? - Appearance? (2 features) -location? - Control ? -Function ?Length: 50-100 μm Mono-nucleated mainly (<5 nuclei per muscle fibre) Appearance: Branched, striated Location: Lining of the heart Control: Self-contractible (i.e. without neural input), involuntary, autonomic NS, no direct conscious control • Function: Responsible for maintaining rhythmic heart-beat and blood flow.Smooth Muscle - length ? - Type of nucleus ? - Appearance? (3 features) -location? (4 places) - Control ? -Function ? (4 functions)Length: 30-200 μm Mono-nucleated, centrally placed nucleus Appearance: Spindle shaped, tapered ends, non-striated Location: Lining of the respiratory, cardiovascular, digestive and reproductive tract Control: Involuntary, autonomic NS Function: fluid transport; valves; dilation/constriction of pupils; arrector pili attached to hair folliclesAre there any Other Muscle Functions ?YES 1- Maintain posture and body position - skeletal muscles function almost continuously with fine adjustments to maintain posture and upright stance against the downward pull of gravity. • 2- Stabilize joints - as well as causing movement of the joints and skeleton, muscles strengthen and stabilise these joints. 3- Generate Heat - during contraction muscles generate heat as they contract which plays an important role in maintaining a constant body temperature in endothermic animals - this is the reason why we shiver when we are cold!Skeletal Muscle Anatomy 1-Name the membrane wrap each muscle ? 2- What is "the fibre bundles" called?1-Endomysium 2- Fascicles..Continued 3- What is the membrane covering Fascicles called? 4-What is the membrane covering bundles of fascicles called?3- perimysium 4- epimysium to form the muscle itself..Continued 5- What are the functions of the three membranes + what is type of tissue found in them ? 6- Tell me about blood vessels/capillaries?5- are tough connective tissue sheaths that 1- hold the muscles together and 2- also transfer force generated by the muscles to the tendons and skeletal fixation points 6- Within the muscle there is a vast network of blood vessels with capillaries forming a net like arrangement to supply the oxygen and nutrients needed and carry away the CO2 and metabolic waste...Continued 7- what's the benefit from having a net-like capillary ? 8- Does the skeletal muscle have nerve supply ?7- The net-like capillary structure allows changes is shape as the muscle contracts and extends. 8- YEEES, because the skeletal muscle requires nerve stimulation, each muscle fibre receive a nerve ending that controls its activity...Continued 9- What is the cell wall called, where is it located ? and where do the nuclei lie? 10- myofibrils ?? what are they and what is their function ?9- Each skeletal muscle fibre is a single-cell, that contains many nuclei along its length. ####The cell wall (sarcolemma) lies within the endomysium and the nuclei lie on the under surface of the sarcolemma#### 10- Within the fibre and along its length are a series of complex organelles called myofibrils. These myofibrils are the contractile units of the cell. They occupy most of muscle cell volume...Continued 11- Describe the muscle fibre structure. (2 features) 12- What is meant by Sarcomere?11-In a skeletal muscle the muscle fibre (cell) has an elongated structure and is multinucleated (many nuclei per cell). 12- In striated muscle, the muscle cell has a 'striped' appearance (the striations). These 'stripes' can also bee seen as a repeated pattern along each myofibril *** each repeated section of the myofibril is called a Sarcomere****..Continued 13- what are "myofilaments" and are they made up of? 14- What are the two types of filaments and what each contains ? 15- what can the interaction between these types lead to ?13- each sarcomere is made of an arrangement of different filaments called myofilaments which are made up of the contractile proteins of the cell. 14-There are two types of myofilament. The Thick filaments contain myosin molecules and the thin filaments contain actin. 15-It is the interaction of these two filaments that causes them to slide past each other and results in the shortening of the muscle.Describe the sarcomere structure? LONG ANSWER ( Hint: Z-disc, M-line, thick and thin filaments, hexagonal array) How many thin filaments is each thick filament surrounded by ?1- Within each myofibril each sarcomere is bounded at each end by a Z-disc. 2- The actin thin filaments protrude from the Z-disc in both directions forming a hexagonal array of filaments. Thin-filaments from the neighboring Z-discs protrude towards each other but not meet in the middle. 3- In the middle of each sarcomere, midway between each Z-disc pair is the M-line and 4- from this M-line myosin thick-filaments protrude in both directions **with each thick filament laying within the hexagonal array of the thin filaments (i.e. each myosin filament is surrounded by 6 thin-filaments.)** Additional : each thin filament surrounded by 3 thick filaments ( GOOGLE).A)What are the dark- and light-bands defined by? ( 2 things) B) LIST the bands and their locations. (I.A.H)A) The dark- and light-bands of the sarcomere (and hence those of the muscle fibre are defined by the type of filaments and the degree of overlap of the filaments across the length of the sarcomere. B) Light "I" band - the region around the Z-disc beyond the end of the thick filaments (i.e. only the thin-filaments) Dark "A" band - the region occupied by the thick-filaments ( so thick and thin filaments overlap) "H" zone - the region around the M-line where the thick-filaments are present but there is no thin-filament overlap (M-line is where thick filaments linked by accessory proteins. )Neural stimulation 1- What stimulus causes the muscle to contract ? 2- How are all muscle fibres stimulated at the same time? 3- What happens when these synapses receive a nerve impulse ? 4- what happens next ???? Hint : LOCAL depolarization, wall, T-TUBULES and what it ensures ???????1-Activity of motor-neurons is the stimulus that causes contraction of muscles. 2- Each muscle fibre (cell) has a synapse from the associated motor-neuron so that all muscle fibres are stimulated at the same time. 3-.On receiving a nerve impulse these synapses release the neurotransmitter acetylcholine into the synaptic-cleft of the neuromuscular junction. 4- This causes local depolarization of the sarcolemma resulting in an action potential that travels along the cell, but also into the middle of the cell via tubes that project from the sarcolemma into the middle of the cell (T-tubules). **This ensures that all myofibrils are stimulated at the same time.**...Continued 5- How Ca+ ions are released ? (REASON OF THE RELEALSE ) What does this release lead to ? 6- Summarise all the steps. Hint : 6 steps5- s the action potential travels into the cell it causes the endoplasmic reticulum to release calcium ions (Ca2+ ). **It is this release of this Ca2+ that triggers the myofibrils to contract.** 6- 1.A motor neuron fires an action potential (AP) down its axon. 2. The motor neuron's axon terminal releases acetylcholine (ACh) into the synaptic cleft. 3.ACh binding causes a local depolarization triggers an AP in the sarcolemma. 4.AP in sarcolemma travels down T tubules. 5. Sarcoplasmic reticulum releases Ca2+ 6. Ca2+ stimulates contraction.Myofilament structures 1- Describe thin filament structure. 2-Describe this filament structure. 3-Explain Sliding Filament Model.See page 13. 1- contains many myosin molecules whose heads protrude at opposite ends of the filament. 2-Consists of two strands of actin subunits twisted into a helix + two types of regulatory proteins ( troponin, tropomyosin ). 3-The thin-filaments and thick-filaments are made up of different protein structures that are configured in such a way that the myosin heads of the thick-filament can attach (bind) to the thin-filament and then the myosin heads rotate towards the tail of the protein in order to pull on the thin-filament. This process pulls the two sets of thin-filaments towards the M-line in the middle of the sarcomere - much like the process of using your hands to pull a rope towards you.. This process happens in each of the filaments and pulls the two Z-lines together thus shortening the sarcomere. This process happens simultaneously in all the myofibrils within the muscle fibre, and across other muscle fibres within that muscle.How Calcium triggers contraction??Within the thin-filament there are myosin binding sites on the actin molecules. However, in the 'resting' state these binding sites are 'blocked' by the tropomyosin. In the previous section we saw that stimulation of the neuromuscular junction ultimately results in release of Ca2+ ions from the sarcoplasmic reticulum. This Ca2+ binds to the troponin molecules which causes a change in shape of the troponin and tropomyosin which then allows the myosin thick-filament to bind to these binding sites on the thin-filament. See page 14Actin/myosin contraction cycle List the steps of actin/myosin contraction cycle. (Hint: 4 steps).1- Myosin heads hydrolyze ATP and become reoriented and energised. 2- Myosin heads bind to actin forming crossbridges 3- Myosin heads rotate towards the center of the sarcomere (power stroke). 4- As myosin heads bind ATP, the crossbridges detach from actin.Actin/myosin contraction cycle In what conditions does the cycle continue ? ( Hint: 2 conditions)1- ATP is available 2- Level of Ca+ ions in the sarcoplasm is high.What's meant by Power stroke?The ADP and the Pi are released from the myosin head and the energy stored in the 'cocked' head is released as it returns to its lower-energy state. It is in this stage that the myosin pulls the actin filament towards the M-line. see page 16What's rigor mortis ?If ATP is no longer available (e.g. following death) then the attached myosin heads will not be able to detach which will result in the muscle being in a permanent state of contraction - rigor mortis.Cardiac Muscle Appearance? initiated by? kind of connection? regulated by ?• Striated, involuntary muscle • Initiated by pacemaker cells in sino-atrial node • Direct electrical connection between neighbouring cells • Waves of contraction spread across heart • Regulated by autonomic nervous systemCardiac Muscle Can you explain how this muscle works?Atria contract first Force blood into ventricles Electrical signal travels to atrioventricular node and purkinje cells Ventricles contract and expel blood Repeating cycleSmooth Muscle Where is it found ? Type of connection ? What layers can it be found in ?• Forms walls of hollow visceral organs (gut, stomach, blood vessels, airways) & muscles controlling iris dilation • Direct electrical connections between cells (gap junctions) • Involuntary muscles • Contract spontaneously when stretched • Mostly found in two layers: - Longitudinal - Circumferential • Arrangement allows peristalsisEnergy Source for Muscle What are the three ways by which muscle can produce ATP??1.High energy molecules of creatine phoshphate (CP) are stored in muscles and can be used to rapidly convert ADP to ATP by a process called Direct Phosphorylation. This process, along with the initial stores of ATP allows rapid contractions and maximum muscle power over a period of about 15 seconds (e.g. in a 100m sprinter). At the end of the contractions the creatine phosphate stores are replenished as the muscle rests. 1 ATP molecule is generated per creatine phosphate molecule. QR 2.As the CP and ATP stores are depleted, if the contraction continues glucose (obtained from the blood or breakdown of glycogen stores in the muscle) undergoes glycolysis which produces two ATP molecules per glucose molecule. If the oxygen supply is depleted then this process is 'anaerobic' and lactic acid is produced. This process is relatively fast, but the build up of lactic acid is partially responsible for muscle soreness during and immediately after intense exercise. 3.During rest and light/moderate exercise aerobic respiration can take place where glucose and oxygen can combine to produce ATP (along with carbon dioxide and water). This is a very efficient process (about 32 ATP molecules per glucose molecule) but a slow process.Rules of Skeletal Muscle Activity 1- do skeletal muscles meet cross at any point ?? 2- In relation to joint crossed, where the bulk of the skeletal muscle lies?? 3- How many attachment each skeletal muscle has ? 4- Can skeletal muscles push ?? 5- Does the skeletal muscle insertion move to the insertion during contractions ??1-With a few exceptions, all skeletal muscles cross at least one joint. ( both stabilise that joint and cause movement of the joint when required.) 2- Typically, the bulk of a skeletal muscle lies proximal (nearer the body, this means that the muscle doesn't have to move its own mass) to the joint crossed. 3- All skeletal muscles have at least two attachments: the origin and the insertion. 4- Skeletal muscles can only pull; they never push. 5- NOOOO. During contraction, a skeletal muscle insertion (the distal attachment) moves toward the origin (proximal attachment).What's the purpose of skeletal muscles ?TO MOVE A JOINTIn lever, the work done is equal to ???work done = force x distance movedWhat kind of movement produced by Power lever ? and is it an advantage ??small powerful movements; mechanical advantageWhat kind of movement produced by Speed lever ? and is it an advantage ??fast large movements; mechanical disadvantageFirst-class lever What's the arrangement of the elements in this type ? Advantage or disadvantage ??load-fulcrum-effort Depending on the position of the fulcrum relative to the effort and load these can have a mechanical advantage (fulcrum nearer the load) or a mechanical disadvantage (fulcrum nearer the effort). Here the posterior neck muscles lift the weight of the facial skeletonSecond-class lever What's the arrangement of the elements in this type ? Advantage or disadvantage ??fulcrum-load-effort has a mechanical advantage, The nearer the load is to the fulcrum the greater the advantage (a larger load can be moved over a shorter distance). In this example the whole body weight can be raised by contracting the calf muscle upward on the heel.Third-class lever What's the arrangement of the elements in this type ? Advantage or disadvantage ??load-effort-fulcrum Mechanical disadvantage (Ideal for fast, large movements) Flexing the forearm by the biceps brachii muscle is an example of a 3 rd class lever. The effort is exerted on the proximal radius of the forearm close to the elbow joint (fulcrum). The distance over which the muscle contracts is much shorter than the distance over which the load is moved (the load is at the distal end of the forearm)What do we mean by Agonist ??muscles responsible for producing a specific movement ***CONTRACT***What do we mean by Antagonist ?opposes or reverses a particular movement (can also provide resistance to agonist contraction) ***Extend, Relax***When is the function of synergists ?act alongside agonists/antagonists (e.g. immobilise bones/joints so that agonists can act [fixators]; e.g. stabilise wrist while making fist so that wrist doesn't bend)Motor units 1- What is it a motor unit and what is made of?A motor unit is the functional unit of the motor system and consists of one motor neuron and all the muscle fibres it innervates. The number of muscle fibres in a motor unit may vary considerably (from 4 to several hundred). IMP: Generally speaking muscles that control fine movement (e.g. those in the fingers) have smaller motor units with fewer fibres. The larger weight bearing muscles (e.g. hip muscles) have larger motor units with many more muscle fibres in the unit (but also contain smaller ones as well).2-How many motor neurons innervate a muscle fiber?? 3-What does the answer of 2 mean?2- The muscle fibres associated with a single motor unit are spread throughout the muscle rather than in one place and ***generally each fibre is innervated by only one motor neuron in only one place.*** 3-This means that stimulation of a single motor unit produces a weak but uniform contraction of the muscle as a whole.List the 4 factors affect the Force of muscle contraction?- Degree of Muscle stretch - Frequency of stimulation - Number of muscle fibres recruited - Size of the muscle fibres.Length-tension relationship A) What does the force generated by each sarcomere depend on ? B)What is this thing(the answer of A) linked to ? (hint: active and passive force )A) For each sarcomere the force generated depends on the length of the sarcomere B).. which is linked to the degree of overlap of the thick and thin filaments (active force generation) and the degree of stretch of the connection (passive force)Length-tension relationship C) what happens in cases of fully starched?? D) what happens in cases Filament overlapping?? E) what's the other case active force decreases ?C)Fully stretched: Little overlap of the thick and thin filaments (little active force generation) Connection fully stretched (high passive force) D) Filament overlap: Large overlap of the thick and thin filaments (high active force generation) Connection not stretched (little passive force) E)Further decrease in sarcomere length, overlap between thin filaments interfere with crossbridge formation (decrease in active force generation)Muscle twitch 1) What are the 3 phases of muscle contraction ?Muscle contraction has three phases: -Latent period (Over the first few milliseconds the muscle cross bridges begin to cycle but muscle tension is not yet measurable) - Contraction (the muscle tension increases.) - Relaxation(the contraction Ca2+ ions are pumped back into the sarcoplasmic reticulum and the number of active cross bridges declines and the force generated by the muscle decreases)2) Give an example of the muscle contraction which is rapid and brief. 3)Give an example of muscles that contract more slowly and remain contracted for longer?2)the extraocular eye muscles 3) gastrocnemius and soleus muscles of the calfFrequency of stimulation List the four cases. Hint, Individual, Temporal, Unfused, FusedA single stimulation of a muscle produces a single twitch response. If this is repeated after the relaxation period has finished then a second twitch occurs that is distinct and shows the same maximal tension (a). If the stimuli are closer together in time and the muscle has not had time to fully relax then a second twitch is 'added' to the first resulting in a higher maximum tension (b) - this is example of temporal summation. If the stimuli are more rapid still (c) then the contractions overlap further and rapidly reach a (fluctuating) plateau (unfused tetanus) and do not increase further. If the stimulation is more rapid still then the contractions fuse at a maximum level (fused tetanus - d). (NO relaxation between stimuli). During this tetanic contraction the sarcoplasmic Ca2+ level stay high and the muscle never has chance to relax.Fibre recruitment 1-Define Thresholds stimulus. 2-Define Maximal stimulus.1-When the stimulus is below threshold there is no motor unit activation or contraction. Once the stimulus reaches threshold some of the motor units respond and muscle fibres of those motor units contract (BELOW THIS POINT NO CONTRACTIONS) 2- As the stimulus level increases more and more motor units respond and the number of muscle fibres that contract increases. Once all motor units are active then maximum tension is reached and @@@@@@ a further increase in stimulation doesn't result in a further increase in tension.@@@@@Size principle 1- What is the general principle in the process of recruitment of motor units? 2- What happens if the stimulus increase? 3- Why large fibres only stimulated for powerful contractions?1- There is a general principle in the process of recruitment of motor units in that the motor units with the smallest muscle fibres are activated first. 2- As the stimulus increases (or continues) the larger fibre units 'join in' and contract with the largest fibres only being stimulated for the most powerful contractions. 3-This allows for the same muscle to carry out small delicate movement as well as large powerful movements.Muscle fibre types 1- What type is good for sustainable contraction? 2-What type is good for fast contraction ? 3- What are type 2 types used for?1- Muscles that don't need to contract quickly but need to sustain the contraction contain slow-twitch fibres 2-Muscles that need to act quickly, but only for a short period of time contain fast twitch fibres. 3- Type IIa - enough aerobic activity to resist fatigue for a few minutes Type IIb - anaerobic catabolism, use glycogen as an energy source, forms lactic acidMotor unit types 1- What are the properties of motor units mainly determined by ? 2-Are all muscle fibres of the same type ?? 3- What are the 3 properties of motor units? 4- What are the 3 categories ??1-..the muscle fibres 2-All muscle fibres in the same motor unit are of the same type. 3- - Speed of contraction - Size/strength of contraction - Fatigue resistance/endurance 4- Type S, Type FR, Type FFType S Motor units 1-Talk about contraction force and size and the connection of this type with fatigue. 2-What type of fibers connected to this ? 3-When is it recruited ?1- Slow contraction (50-110ms twitch time) - `slow' myosin Small force (<20g tetanic tension) - `few' muscle fibres/MU Resistant to fatigue (oxidative metabolism, many mitochondria, good blood supply) 2- Type I muscle fibres 3- Recruited first during contractionType FR Motor units 1-Talk about contraction force and size and the connection of this type with fatigue. 2-What type of fibers connected to this ? 3-When is it recruited ?1-Fast fatigue resistant (FR) Fast Contraction time (25- 45ms)→ "fast" myosin isoform Intermediate force (20-60g tetanic tension) - intermediate number of muscle fibres/MU Resistant to fatigue (oxidative metabolism) 2- Type IIA muscle fibres 3-Intermediate recruitment orderType FF Motor units 1-Talk about contraction force and size and the connection of this type with fatigue. 2-What type of fibers connected to this ? 3-When is it recruited ?1-Fast fatiguable (FF) Very fast contraction (<10ms) → "Fast" myosin isoform • High force(50-150g) → many, large muscle fibres / MU • Fatigue easily (anaerobic metabolism, glycogen store, few mitochondria) 2-Type IIB muscle fibres 3-Recruited last during contractionWhat is the function of myoglobin?It is the protein that stores oxygen within the muscle fibres.