Muscle Tissue and Nervous Tissue.docx

Muscle Tissue They have 4 qualities: Excitability (respond to stimulus) Contractability (ability to contract, shorten) Extensibility (ability to stretch without tearing) Elasticity (can return to original shape) Skeletal Large and elongated Located on skeletal - Voluntary muscle due to Somatic inne...

Muscle Tissue They have 4 qualities: Excitability (respond to stimulus) Contractability (ability to contract, shorten) Extensibility (ability to stretch without tearing) Elasticity (can return to original shape) Skeletal Large and elongated Located on skeletal - Voluntary muscle due to Somatic innervation (General somatic efference) fibres in nerve Attaches via tendons to move joints Satellite cells present on periphery to aid recovery Has striation – due to dense arrangement of actin + myosin Nucleus located peripherally - multi-nucleated No cell-to-cell junctions Can contract only fully Cannot undergo mitosis, so regeneration is limited Cardiac Short and Narrow Located at Heart and adjacent large veins Striated – due to myosin and actin is also cylindrical and branched Single central nucleus Intercalated discs for cell-to-cell junctions – allows for coordinated contraction Autonomic control – due to vagus nerve and sympathetic chain allows for parasympathetic and sympathetic movement to control heart rate (visceral motor efferent) All or none contraction No Mitosis or regeneration Smooth Short and spindle shaped Located at vessels organs and viscera (found in walls of hollow organs) No striation – made of small fusiform cells Single central nucleus Gap junctions for cell-to-cell junctions Autonomic innervation (don’t need to think to use) Slow, partial contraction Able to do mitosis and regenerate What causes contraction? Interactions between myofilaments Sarcomere – made up of actin strand, myosin strands and titin strands At rest actin and myosin don’t touch When contracted – thin actin slides past thicker myosin, so they overlap Contraction require ATP and calcium (so proteins can become unblocked) Chemical energy to kinetic energy Sarcoplasmic reticulum is loaded with calcium pumps and stores calcium - so when action potential opens calcium floods cell This calcium floods into cell and binds to Tropin Thus, deforming tropomyosin allowing myosin to bind to new site on Tropin Myosin heads bind to actin What stops contraction? Calcium stops flooding of fibre (action potential close) Calcium gets depleted – nerve impulses stop Calcium unbinds from Tropin Rigor Mortis diseases – no ATP to bind to myosin from Tropin therefore remains contracted Nervous Tissue Neurons: Dendrites, extend from cell body fairly short but have lots of branches – they receive nerve impulses Cell body mainly located at CNS or in Ganglia (just outside spinal cord) of PNS Axon, single nerve fibre transmits impulse to distal end (can be very long) Types of Neurons: Multipolar neuron – has long axon with presynaptic terminals at 1 end and perikaryon on other side with dendrites attached to it Bipolar neuron – has presynaptic terminals at CNS (at one end) with the Perikaryon in the middle of axon and dendrites at another end Pseudo-unipolar neuron – Has PNS terminals and CNS terminals either end with a perikaryon attached like a droplet Unipolar neuron – same as multipolar neuron however no dendrites at perikaryon instead in the middle of axon. Spinal Cord: Made up of White matter located on the outer circumference and grey matter located centrally – also has spinal ganglion located on the outside the white matter Glia – provide support, nutrition, insulation and help with signal transmission Central Nervous System (CNS) Astrocytes – supports + regulate ions Microglial cells – immune defence Ependymal cells – line cavity (ventricles of brain) Oligodendrocytes – wrap and insulate (forms myelin sheath) Peripheral Nervous System (PNS) Satellite cells – surround neuron cell bodies, small cuboidal cells Schwann cells – Insulate, forms myelin sheath (Myelin Sheath – Lipid rich layer) Neuromuscular junction Lots of motor neurons originate at spinal cord or brain stem Branch near muscle and end at individual muscle fibre