Musculoskeletal System 2 PDF

HCSC1001 Medical Sciences for Audiology Week 3: Musculoskeletal system 2 Dr Nisha Valand [email protected] Muscle Tissue  Muscle Types – Skeletal: Responsible for locomotion, facial expressions, posture, respiratory mo...

HCSC1001 Medical Sciences for Audiology Week 3: Musculoskeletal system 2 Dr Nisha Valand [email protected] Muscle Tissue  Muscle Types – Skeletal: Responsible for locomotion, facial expressions, posture, respiratory movements, other types of body movement. Voluntary. – Smooth: Walls of hollow organs, blood vessels, eye, glands, skin. Some functions: propel urine, mix food in digestive tract, dilating/constricting pupils, regulating blood flow. In some locations, autorhythmic. Controlled involuntarily by endocrine and autonomic nervous systems. – Cardiac: Heart: major source of movement of blood. Autorhythmic. Controlled involuntarily by endocrine and autonomic nervous systems.  Muscle Cell Terminology Muscle related words – have a prefix of ‘Myo’ or ‘Sarco’ muscle Greek for flesh Muscle cell = myocyte or myofibre Muscle cell cytoplasm = sarcoplasm Muscle cell membrane/plasmalemma = sarcolemma Endoplasmic reticulum = sarcoplasmic reticulum (SR)  A typical (non muscle) cell Muscle Cell Components Cell membrane – sarcolemma Cytoplasm – sarcoplasm Nuclei, organelles… Skeletal muscle cell Full of myofibrils – actin/myosin Many mitochondria https://opentextbc.ca/biology/chapter/19-4-muscle-contraction-and-locomotion/ Extensive endoplasmic reticulum – sarcoplasmic reticulum  Cardiac muscle cells Skeletal muscle cells & wiseGEEK.org Smooth muscle cells  Common Features of All Muscles Actin and myosin – generate force for contraction Calcium ions – needed for activation of http://exchange.smarttech.co m/details.html?id=14ac310a- f789-4c9b-97d8- 32778d779446 contraction http://www.broughtonfc.co.uk/ Supply of ATP – generated via respiration: Aerobic oxidative respiration Anaerobic glycolytic respiration Stimulation – need an action potential from a neurone http://www.nvo.com/scullari/unitii/  Smooth muscle cells Small – 100-200 µm in length Spindle shaped cells arranged into sheets Less regularly organised No striations Single nucleus Sheets of smooth muscle cells arranged in sheets perpendicular to each other Scanvet.com Blood vessels: regulates lumen diameter – contributes to maintenance of blood pressure  Slower contraction rate - longer duration than cardiac or skeletal muscle  Cardiac muscle cells Continually contracts at a steady rate Can contract without stimulation – myogenic Involuntary muscle – autonomic nervous system (ANS) Branched cells Microscopic Anatomy - Cardiomyocytes Small - 100 µm in length Uni- or bi-nucleated Striated Intercalated disks Aerobic oxidative metabolism Adapted from drsvenkatesan.wordpress.com/wikipedia A B Cell membrane C Water-filled channel Marieb 10th Ed. pg330 Scanvet.com  Skeletal muscle cells Skeletal Muscle >40% Body 640 muscles Body movement Attached to the skeleton via tendons Large cells Voluntary control Sporadic and continual contraction https://healthsciencetechnology.wikispaces.com/Muscular+System  A single muscle cell Myofilaments: Actin and Myosin Marieb 10th Ed. Pg301  Striations: overlapping ACTIN & MYOSIN Sarcomere myofilaments nicerweb.com Myofibre/myocyte - muscle cell containing myofilaments Myofilament: Contractile units called SARCOMERES Sarcomere Skeletal muscle cell Contraction https://opentextbc.ca/biology/chapter/19-4-muscle-contraction-and-locomotion/ SLIDING FILAMENT THEORY  Muscle Cell Function: Contraction Actin and Myosin make up ~90% of muscle protein Thin filament Thick filament http://www.crossfitinvictus.com/blog/muscle-contraction-really-cool-protein-called-myosin/  Actin Actin subunits (“G actin”) G actin subunits polymerise into long, filamentous or “F actin” Two intertwined actin filaments Active sites to which myosin head attaches in contraction Regulatory proteins Tropomyosin → stabilise actin Troponin → binds actin, tropomyosin and calcium Marieb, figure 9.3  Myosin Rod-like tail attached by flexible hinge to two globular heads Tail – two intertwined helices Globular heads link thick and thin filaments in contraction Cross bridges → motors (force) Actin and ATP-binding sites Intrinsic ATPase activity Marieb, figure 9.3 Actin and Myosin Interaction http://imgur.com/gallery/DaGwMo2/comment/378891276 Neuromuscular junction Neuromuscular junction Muscles need to move to prevent atrophy Think… Rigor mortis NMJ = synapse between a motor neurone and skeletal muscle fibre Requires energy Synapses branch off (bouton) over specialised regions of muscle (end plates) Neuromuscular junction – Overview Each myofibre receives its own branch of the nerve fibre An action potential travels down the motor neuron towards the muscle This triggers the release of a neurotransmitter, which diffuses across the synapse and triggers muscular contraction Neuromuscular junction – Overview Space between neuron and muscle is called ”synaptic cleft” Indents called junctional folds Contain ligand-gated ion channel receptors for Ach AP travels down the neuron it causes Ach release into cleft Binds to receptors Ion channels open Causes depolarisation "excitatory post-synaptic potential” Voltage gated sodium channels open to transmit AP down the muscle Transfer across Chemical Synapses Presynaptic neuron 1. Action potential arrives at axon terminal 2. Voltage-gated Ca2+ channels open Ca2+ and Ca2+ enters the axon terminal Ca2+ Ca2+ Ca2+ 3. Ca2+ entry causes synaptic vesicles to Synaptic cleft fuse with presynaptic membrane and to release neurotransmitter by exocytosis Synaptic vesicles 4. Neurotransmitter diffuses across the Postsynaptic neuron synaptic cleft and binds to specific receptors on the postsynaptic membrane Ion movement Enzymatic Graded potential degradation Reuptake Diffusion away 5. Binding of neurotransmitter opens ion from synapse channels resulting in graded potentials, i.e. receptor potential 6. Neurotransmitter effects are terminated by reuptake through transport proteins, enzymatic degradation, or diffusion away from the synapse Reading The Skeleton: Pages 207-214 Bones of the head: Pages 233 - 244 Joints: Pages 296-297 Muscle and Muscle tissue : Pages 313-352