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muscle directed stud
reg of contraction
| Question | Answer |
|---|---|
| Determinant of contractile force | the total contractile force is determined by the total number of cross-bridge it formed |
| what is the difference between amount of muscle use in cardiac and skeletal muscle | Cardiac muscle contact all at the same time as a one unit. Skeletal muscle can vary its amount of muscle to contract depending on the need of force |
| Which muscle has short duration and what is the importance of that? | Skeletal muscle has short contractile duration which make tetany possible. We can increase frequency of contraction to increase force. However, cardiac muscle has long duration which make tetany impossible. |
| difference between E-C coupling mechanism in cardiac and skeletal muscle | Cardiac muscle: calcium induce calcium release to activate RyRs. Skeletal muscle: Ca2+ independent activation of RyRs. with cardiac muscle, it is easier to influence the amount of Ca2+ release form SR. |
| what factor can be influenced inside the cardiac muscle, but not possible for Skeletal muscle? | Ca2+ release to cytosol. Since Cardiac muscle is Ca2+-induced-Ca2+ release mechanism, we can modift the process, and allow more or less ca2+ release to the cytosol |
| The factor determine the size of force generate by cardiac muscle | The amount of SR Ca2+ release to cytosol. Increasing SR Ca2+ release will increase size of force |
| mechanism to increase the SR Ca2+ storage | increase SERCA pump activity, decrease Ca ATPase and NA-CA exchanger activity, we can increase SR Ca2+ storage as now more CA2+ will be pump back to SR than pump out of cell |
| What is the effect of increasing SERCA pump activity on Ca2+ storage and on the contractile force? | Increase SERCA pump activity, increase CA2+ SR storage, Increase CA2+ release next time, Increase contractile storage |
| What does Increase SERCA pump activity has on the rate of relaxation? | Increase the rate of relaxation (quicker, less than to relax muslce) (increase subsequent force of contraction) |
| 2 mechanism to influence the contractile force of cardiac muscle | 1) SERCA pump activity to affect subsequence rate of relaxation and contractil force 2) size of Ca2+ trigger to influence the extend of SA Ca release |
| what is Ca2+ Trigger in Cardiac muscle contraction? | The trigger is the ECF Ca2+. As more ECF Ca2+ flow through the DHPR, more RyRs will open and allow greater release of Ca2+ from SR, Increase contractil force therefore. |
| which two neurotransmitter from symphathetic sysmstem control cardiac muscle contraction | Epinephrine and norepinephrine |
| How does Epinephrine and Norepinephrine affect cardiac muscle contraction | they bind to beta-adrengic receptor and increase cAMP which increase activation of PKA. PKA phosphorylation protein regulate SERCA pump and DHPR channel, which increase SR Ca2+ release and therefore increase contractile force |
| What receptor does epinephrine and norephinephrine bind to? | beta-adrengic receptor |
| how does skeletal muscle control contractile force generation? | 1) for single muscle fiber, increase frequency of contraction (twitch) 2) for whole skeletal muscle:, increase the number of motor unit recruited |
| For single muscle fiber, how does low frequency of contraction influence force produce? | 1) Low frequency, the force is summed by all the twitch while Ca2+ level is up and down. "Unfused contraction" |
| for single muscle fiber, how does high frequency of contraction influence force generated? | AT high frequency, there is high constant level of contraction, the summation of all the twitches will result in Tetany, contractil force increase and there is a CONSTANT elevation of Ca2+ level (fused contraction) |
| the relationship between motor unit and force generation in whole skeletal muscle | increase motor unit, increase force generated in whole skeletal muscle |
| in fine movement, do we recruit small or large motor unit? and are those motor unit slow or fast twitched? | For fine movement, we recruit small number of motor units, and these units are usually SLOW TWITCHED |
| in large movement, do we recruit small or large motor unit? and are those motor unit slow or fast twitched? | For large movement, we recruit large number of motor units, and these units are usually FAST TWITCHED |
| Tension | The force or "force of contraction" that acts to pull the 2 ends of a muscle toward each other and shortening the muscle |
| factor that affect tension developemnt | the muscle length affect tendsion development, it is more important for cardiac muscle, but not so much to skeletal muscle |
| what does Ernst Starling experiment prove? | Increase Ventricle pressure (Increase Ventricle volume) will enhance contractil shortening and thus increase contractile force |
| Physiological relationship of muscle length and contraction in cardiac muscle | increase muscle length will increase force of contraction in cardic muscle |
| what are the two types of muscle contraction | Isometric and Isotonic contraction |
| Isometric | Muscle can generation tension w/o shortening muscle length as muscle length is "fixed" |
| Isotonic | Muscle shortening while against a constant load |
| active tension | Total force (when muscle is stretched and stimulate) - passive tension (when muscle is stretched w/o stimulation) |
| When cardiac muscle can increase tension by increase length but skeletal muscle cant? | Resting cardiac muscle length is shorter than optimal length, therefore, increase lenght can increase cross-bridge formation and increae force. However, Resting skeletal muscle is already at optimal length, further increase length won't increase force. |
| Optimal length | optimal length is when there is max overlap of myosin and actin, therefore max cross-bridge formation and max force generation |
| What happen when the muscle length is too short or too long | Muscle length is too short, physical hinderance from actin and myosin overlap inhinbit cross-bridge formation. When the length is too long, there is no overlap and less cross-bridge formation |
| what does cardiac muscle has shorter resting length than skeletal muscle? | Cardiac muscle has more elastic fiber which will resist stretching and therefore it has shorter resting muscle length |
| length-tension relationship | the max tension occur at optimal muscle length where is optimal overlap of mysoin-actin filament (max cross bridge formation) |
| Load-velocity relationship | the light the weight (load), the higher the velocity of shortening muscle (faster contraction). Max load is where your muscle and bear weight but cant shorten anymore |
| relationship of cross-bridge formation with tension | Tension: there is no shortening, depending on number of STATIC cross bridge to balance the load. |
| Relationship of cross-bridge formation with velocity | Velocity include shortening of muscle length. Cross bridge need to participate in actual cycle (detachment, attachment and power strike). It depend on the number of SPARE cross-bridge available after those used to balance the load |
| load-velocity relationship with spare cross bridge | increase number of spare cross bridge, increase velocity of shortening (when we lift up a feather) |
| list 2 component for normal muscle contraction | 1) Isometric component (develope tension with constant muscle length) 2) Isotonic component (shortening muscle with constant load) |
| List activity of isotonic and isometric component during muscle contraction | 1) Isometric contraciton to develop tension 2) Isotonic contraction (shortening muscle) 3) isotonic relaxation (increase muscle length to put to object) 4)Isometric relaxation (to upload the weight) |
| 2 types of skeletal muscle fiber | Fast twitch and slow twitch skeletal muscle fibers |
| SLOW twitch muscle fiber | 1) red fiber (type I) 2) use oxidative metabolism(Use Oxygen to generate ATP) 3) fatigue resistant (less lactic acid accumulation) 4) slow contraction velocity (postural muscle) |
| Fast twitch muscle fiber | 1) White fiber type IIB 2) glycolytic metabolism (anaerobic) 3) easy fatigue (built up of latic acid) 4) fast contraction (muscle for speed) |
| What element determine the velocity of muscle contraction | Myosin ATPase activity. Different muscle type has different myosin isoform with slightly different ATPase activity. The faster the ATP hydrolysis, faster the cross-bridge cycle and increasing velocity of the contraction |
| arrange the rate of Myosin ATPase activity from high to low gastrocnemius, soleus, Lateral rectus, | Lateral rectus (highest rate of ATPase) > gastrocnemius > soleus |
| what are the 2 muscle receptor to sense muscle length and tension | 1) Muscle spindle 2) golgi tendon organs (GTOs) |
| location and funciton of muscle spindle | muscle spindle is found in the belly of muscle and can sense length changes in muscle |
| Location and function of Golgi tendon organs? | GTOs is found in the tendon which can sense muscle tension |
| what type of afferent and efferent neuron does muscle spindle has? | Afferent neuron (Type Ib and Type II) Efferent neuron (Gamma motor neuron) |
| What type of efferent neuron does muscle has to response with muscle contraction? | alpha motor neuron |
| What is the function of gamma motor neuron of muscle spindle | it will change the sensitivity of muscle spindle to length chnages |
| what is the importance of muscle spindle arrange to its function | the muscle spindle is arranged parallel to muscle fiber for sensing length changes easily |
| Describe how muscle spindle function | The muscle spindle will sense muscle stretch and then send AP along afferent neuron group Ia and II and increase spindle firing. |
| how does Golgi Tendon organ sense the tension | The tension develop in muscle exert on tendon where GTOs are located. The tension then squeeze the collagen which in turn on the nerve ending. Information is then sensed along Group Ib afferent |
| What afferent does Golgi tendon organ has? | Type Ib afferent |
| What the nerve ending of GTOs locate | the nerve ending of GTOs are interweaved with the collagen in tendon. |
| what is muscle spindle and GTOs response to streching ? (firing rate) | 1) Muscle spindle: increase firing 2) GTO: little or no change in firing rate |
| What is muscle spindle and GTOs response to tensino (contraction) (firing rate) | 1) Muscle spindle: firing drop to zero because during contraction it is at unloading state 2) GTOs: dramatically increasing in firing. |
| streching will increase active or passive tension? | Passive tension mostly |
| what factor determine Type Ia response to streching | Type Ia response mostly to the rate of stretching (velocity) but also slight to the absolute muscle length |
| What factor does Type II response to ? | Type II afferent only reponse to the absolute muscle length, it does not response to the velocity of stretching |
| what is the most important elastic component in cardiac muscle | titin. It provides the oppsing ofrce during stretch and restoring force during shortening |
| effect of norepinephrine and postivie inotropic agent (cardiac glycoside) has on myocartial contractility | it increases myocartial ontractility |
| gamma motor neuron's effect on muscle spindle | The gamma motor neuron shortens the length of muscle spindle and maintain its job of sending information about muscle length during Muscle contraction. |
| Does gamma motor neuron increase or decrease muscle spindle's sensitivity? | Increase |
| what is muscle spindle important for? | Sense position (Propriceptive sensation) |
| Myotatic reflex | A monosynaptic stretch reflex which a rapid stretch of muscle lead to contraction of the same muscle |
| what is purpose of myotatic reflex | to limit inappropriate muscle stretch |
| pathway of myotatic reflex | the rapid stretch muscle fire muscle spindle ==> send information along the afferent Ia neuron ==> Ia make a direct synpase with alpha motor neuron of same muscle in the spinal cord ==> contraction of same muscle |
| what cause the tenderpoint | The inappropriate activation of Gamma motor neuron which led to muscle shortening and increase muscle spindle sensitivity led to inappropriate strech reflex and then tenderpoint |
| How does counterstrain help to release tenderpoint | counterstrain reset the muscle spindle system following muscle strain (reduce inappropriate gamma activation and stretch reflex) |
| how does the myotatic reflex result in joint movement | 1) Ia afferent from muscle spindle activate alpha motor neuron of agonist muscle ==> contraction 2) it also synapse the inhibitory interneuron which inhibit the contraction of alpha motor neuron of antagonist muscle ==> relaxation |
| example of stretch reflex | Keen jerk (patella reflex) |
| inverse myotatic reflex | GTOs detect tension (contraciton) which trigger muscle reltaion |
| pathway of inverse myotatic reflex | GTOs detect tension from contraction, send information from Ib afferent to spinal cord where they synapse 2 interneuron. The inhibitory interneuron cause relaxation in agonist muscle while excitatory interneuron result in contraction of antagonist muscle |
| what is the difference between mytatic reflex and inverse myotatic reflex | Myotatic reflex involve muscle spindle and result in muscle contraction. Inverse myotatic reflex result in muscle relaxation and GTOs is involved |
| how many interneuron does myotatic reflex and inverse myotatic reflex synapse with | myotatic : 1 interneuron (inhibitory interneuron with antagonist)' Inverse myotatic reflex: 2 interneuron. (Excitatory interneuron with antagonist muscle and inhibitory interneuron with agonist msucle) |
| what is the reaction of agonist muscle in myotatic and inverse myotatic reflex | myotatic: agonist muscle contract. Inverse myotatic reflex: agonist muscle relax |
| what is the reaction of antgonist muscle in myotatic and inverse myotatic reflex | myotatic: antagonist muscle relax. Inverse myotatic reflex: antagonist muscle contract |
| which reflex does not involve muscle spindle or GTOs | flexor reflex |
| Flexor reflex | produced coordinated response in ipsilateral (the affected limb) and contraltaeral limb.-muscle spindle and GTOs are not invloved. -Excitatory and inihibitory interneuron are needed to coordinate the movement |
| in flexor reflex, which leg's flexor will be activated and extensor will be inhibited | The ipsilateral limb (affected limb), the withdrawal one |
| the purpose of stretch reflex test | we want to test if paitent has defect in sensory system (all sensory component in msucle), lower motor system (alpha motor neuron in muscle) or upper motor system (motor cortext and associated region and spainal cord) |
| if there is an decrease in reflex, what is the indicaiton? | there is problem with sensory system or lower motor system |
| what does hyperreflexia indicate | there is a loss of descending input from upper motor neurons to inihibit stretch reflex. Since there is no descending inhibitory sign, the reflex is uninhibited. |
| Bakinski sign | the extension of toe when the sole of foot is stroked. Usually seen in new born. Adult with loss of descending inihbitory input from upper motor system, will see extension of toe. |
| Tetanospasmin | the toxin produced by Clostridum tetani which cause tetanus infection. The toxin inhibit the inhibition input from the descending upper motor system to the alpha-motor neuron and result in muscle spasm. |
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powerbaby
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