Muscle and Nervous Tissues PDF

MUSCLE AND NERVOUS TISSUE Types of biological tissues 3 [email protected] TODAY WE WILL COVER: Describe the features of each muscle cell type and to identify each type histologically Describe organisation of myofilaments Describe the sarcomere and a motor unit Describe the general features of...

MUSCLE AND NERVOUS TISSUE Types of biological tissues 3 [email protected] TODAY WE WILL COVER: Describe the features of each muscle cell type and to identify each type histologically Describe organisation of myofilaments Describe the sarcomere and a motor unit Describe the general features of a neurone Describe neuroglia Describe and identify structural components of nerves Describe how nerve fibres supply skeletal muscles MUSCLE TISSUE One of the 4 main tissue types that composes vertebrate bodies Has 4 qualities: Excitability- the ability to respond to stimuli Contractibility- the ability to contract- i.e. shorten Extensibility – the ability to stretch without tearing Elasticity- ability to return to original shape Involuntary Striated Skeletal Cardiac Smooth Structural Features Skeletal Cardiac Smooth Muscle Cell Large and elongated Short and narrow Short and spindle shaped Location Skeletal / voluntary Heart and adjacent muscle large veins Vessels, organs, viscera Striation Yes Yes No Nucleus Many peripheral Single central Single central Cell-to-cell junctions none Intercalated discs Gap junctions Type of innervation somatic autonomic Autonomic Type of contraction All or none All or none Slow, partial Mitosis no no Yes Regeneration limited no yes Smooth muscle is unstriated, made of small fusiform cells closely packed together. Single nuclei that is centrally located. Found in the walls of hollow organs so sometimes known as visceral muscle. Under autonomic control is produces low level peristalsis to SMOOTH MUSCLE TISSUE Cardiac muscle is also striated due to dense arrangements on actin and myosin, and is cylindrical but with branches also It is autonomic control. The Vagus nerve and the sympathetic chain provide parasympathetic and sympathetic innervation to the cardiac muscle respectively and therefore the heart rate. (Visceral Motor Efferent) It has a unique cell to cell junction known as Intercalated Disks which allows cell to cell communication for a co-ordinated output. Single nuclei, based in the centre. CARDIAC MUSCLE TISSUE Skeletal muscle is a striated, cylindrical muscle under staining due to the dense arrangement of actin and myosin Each sketetal muscle cell is multinucleated due to being so large, pushed to the periphery It is under voluntary control – by general somatic efferent (GSE) fibres in the nerves It attaches to bones via tendons, muscles have to traverse a joint in order to have any action. Has Satellite Cells dispersed on the periphery to aid with recovery SKELETAL MUSCLE TISSUE Skeletal Muscle What causes contraction? Interactions between myofilaments What causes contraction? At rest – actin and myosin don’t touch Before they can – obstacles to over come Thin actin filaments slide past the thicker myosin, so they overlap more What causes contraction? Contraction requires - ATP and calcium – proteins can become unblocked Chemical energy to kinetic energy conversion Mitochondria makes ATP Sarcoplasmic reticulum loaded with calcium pumps – and stores calcium Action potential opens the calcium channels – calcium floods into the cell What causes contraction? Calcium binds with troponin Deforms tropomyosin, meaning the myosin heads can bind to the newly revealed sites on troponin ATP → ADP and P – releases energy Myosin head binds to actin What causes contraction? Calcium stops flooding in to the fibre - nerve impulse stops - calcium has been depleted Calcium unbinds from troponin Rigor Mortis “Bridge made” No ATP to unbind the myosin from the troponin Remains contracted – fixed in position Nervous System Complex network of neurones and associated support cells Anatomical location Function Motor vs Sensory Peripheral vs Central Autonomic vs Somatic NEURON STRUCTURE Neurons =Nerve cells, are specialised cells that conduct electrical impulses. All neurons have the same basic structure: Dendrites extend from the cell body. These are fairly short, with lots of branches, and they are the points at which nerve impulses are received by the cell. The “listening” part of the cell The cell body itself. Most of the cell bodies of neurons are in the central nervous system or arranged in the ganglia (which lie just outside the spinal cord) of the peripheral nervous system. The axon: a single nerve 'fibre' which transmits impulses to the distal end. Axons can be very long - around 1 metre and range in diameter. This is the “talking” part of the cell. NEURON STRUCTURE NEURON TYPES LOCATION OF CELL BODIES IN SPINAL CORD Supporting Cells - Glia Schwann Cells Produce lipid rich layer – myelin sheath PNS Satellite Cells Layer of small cuboidal cells PNS Oligodendrocytes Myelin in CNS CNS OLIGODENDROCYTES Microglia Engulf and destroy debris CNS MICROGLIA Ependymal Cells CNS Line ventricles of the brain EPENDYMAL CELLS Astrocytes Most numerous Cover surfaces Communicate between neuron and capillary Blood brain barrier – blood to brain They are involved in metabolic exchange between neurons and blood. CNS ASTROCYTES Neuromuscular Junction Richly innervated by motor neurons – originate at spinal cord or the brain stem Branch near the muscle and end on individual muscle fibres Neuromuscular junction / motor end plate