FINALS

• Special Functional Characteristics of Muscle

  • Excitability - respond to stimuli
  • Contractility - shorten and generate pulling force
  • Extensibility - stretch with contraction of opposing muscle
  • Elasticity - recoil passively after stretch
• Types of Muscle Contractions

  • Isotonic - Concentric Contraction (shortening of muscles)
  • Isotonic - Eccentric Contraction (lengthening of muscles)
  • Isometric - muscle contracts but does not shorten
• Types of Muscle Tissue

  • Skeletal
  • Cardiac
  • Smooth

  
• Skeletal Muscle


  • Attach to and move skeleton
  • 40% of the body weight
  • Fibers are multinucleated
  • Visible striations
  • Voluntary movement

  
• Structure of Skeletal Muscle

  1. Myofibril -> muscle fiber -> muscle fascicle -> skeletal muscle (organ)

  2. Sarcoplasm - the cytoplasm of skeletal muscle

  3. Sarcolemma - the plasma membrane, forms deep tubular invaginations -> t-tubules

  4. Sarcoplasmic Reticulum - a modified smooth ER

  5. Triad - t-tubules and sarcoplasmic reticulum

  6. Myofibrils - muscle fiber is composed of contractile proteins

  7. Sarcomeres - the segment that divides the myofibrils, contractile / functional units of a muscle

  8. Myofilaments - thick filaments (myosin), thin filaments (F-actin), alternating thick and thin filaments

  9. Z-line / disc - marks the sarcomere boundary
• Muscle Proteins


  • Contractile Proteins - actin and myosin, generate force during contraction
  • Regulatory Proteins - troponin and tropomyosin, switch the contraction process on or off
  • Structural Proteins - titin and dystrophin, provide elasticity and extensibility, links the myofibrils to the sarcolemma
• During Contraction


  1. Thick and thin filaments slide past each other

  2. I-band -> shortens

  3. A-band -> length remains constant

  4. 1 Z-disc comes close to another Z-disc
• Molecular Basis of Contraction

  • Ca++ binds to troponin, myosin heads bind to actin, creating cross bridges
  • Cross bridges -> pulls on thin filaments, sarcomere shortens
  • Ca++ goes back into sarcoplasmic reticulum, contraction stops
• Types of Skeletal Muscle

  • Type I - red / slow
  • Type IIA - red / fast
  • Type IIB - white / fast
• Type I - red / slow


  • Color: red
  • Contraction time: slow
  • Oxidative capacity: high
  • Mitochondrial density: high
  • Resistance to fatigue: high
  • Major storage fuel: fatty acids
  • Metabolic pathway: aerobic
  • Force production: low
  • Typical use: posture, low-level contraction
• Type IIA - red / fast

  • Color: white
  • Contraction time: fast
  • Oxidative capacity: high
  • Mitochondrial density: high
  • Resistance to fatigue: medium
  • Major storage fuel: glycogen, creatine phosphate
  • Metabolic pathway: both
  • Force production: medium high
  • Typical use: speed, strength, power
• Type IIB - white / fast


  • Color: white
  • Contraction time: very fast
  • Oxidative capacity: low
  • Mitochondrial density: low
  • Resistance to fatigue: low
  • Major storage fuel: glycogen, creatine phosphate
  • Metabolic pathway: anaerobic
  • Force production: very high
  • Typical use: short, fast, bursts of power
• Cardiac Muscle


  • Found only in heart wall
  • Myocardium
  • Striated
  • Involuntary
• Layers of the Heart

  1. Pericardium - outermost layer, consists of 2 thin fibrous protective layer that contains fluid to protect them from friction

  2. Myocardium - middle layer, contains the heart muscle

  3. Endocardium - innermost layer, lines the heart
• General Concepts of Cardiac Muscle

  • Bundles form thick myocardium
  • Cardiac muscle cells -> single cells not called fibers
  • Autorhythmicity - muscle cells beat separately even without any stimulations, each cell
  • Involuntary activation
  • Very fatigue resistant
• Ultrastructure of Cardiac Muscle

  • T-Tubules - larger, located at the Z-disc
  • Sarcoplasmic Reticulum - poorly defined, contributes to the dyad
  • Dyads - consists of one t-tubule and one sarcoplasmic reticulum
• Function of Cardiac Muscle

  Provide the contractile activity of the heart
• Conduction System of the Heart

  1. Sinoatrial Node - pacemaker, Node of Keith and Flack, located below the epicardium at the junction of the superior vena cava and right atrium, function: regulates heart rate and rhythm

  2. Atrioventricular Node - Node of Tawara, Located below the endocardium, on the lower part of the interatrial septum, functions: delays cardiac impulses from SA node to allow atria to contract and empty the contents first, relays cardiac impulses to the atrioventricular bundle

  3. Atrioventricular Bundle of His - bundle of fibers located within the septum of the heart, function: carries cardiac impulses down the septum to ventricles via the Purkinje fibers

  4. Left and Right Bundle Branches - functions: carries nerve impulses, right: cause contraction of of right ventricle, left: cause contraction of of left ventricle

  5. Purkinje Fibers - modified cardiac muscle cells, located at the AV Bundle of His, specialized for conduction, large, pale, filled with glycogen, function: trigger waves of contraction through both ventricles simultaneously
• Smooth Muscle


  • Found in hollow visceral organs
  • No visible striations
  • Involuntary
• General Concepts and Structure of Smooth Muscle

  • Muscles -> spindle-shaped cells
  • One central nucleus
  • Grouped into sheets
  • No striations (no sarcomeres and t-tubules)
  • Does not always require a nervous signal - can be stimulated by stretching or hormones
  • Cells - linked by numerous gap junctions
  • Myofibrils - non-straited
  • Myofilaments - not distinct
  • Involuntary - cannot consciously control movement
  • Contraction - very slow and sustained, very fatigue resistant
• Function of Smooth Muscle

  Alter the activity of various body parts to meet their specific needs - contraction of the urinary bladder, peristalsis -> move food through the intestines, peristaltic movement to move feces down the digestive tract, contraction of smooth muscle in the trachea and bronchi -> decreases the size of the airways, constriction and dilation of blood vessels -> regulates blood pressure, constriction, accommodation, and dilation of pupil, uterine contraction during birthing, expulsion of glandular contents, arrector pili muscle -> causes goosebumps, needed for thermoregulation
• Molecular Basis of Smooth Muscle Contraction

  • Interaction of sliding actin and myosin filaments is similar with skeletal muscle
  • Contractions are initiated by the calcium-activated phosphorylation of myosin rather than calcium binding to troponin
  • Intracellular calcium binds with calmodulin, which then binds and activates myosin light-chain kinase
  • Calcium-calmodulin-myosin light-chain kinase complex phosphorylates myosin initiating contraction and activating the myosin ATPase
• Nervous System


  • Group of organs brought together for the purpose of making us react to the environment
  • Formed by nerve cells (neurons) and supporting cells (glial cells)
  • Comprises of central NS and peripheral NS
• Three Major Functions of the Nervous System

  • Sensory - monitors internal and external environment through presence of receptors
  • Integration - interpretation of sensory information
  • Motor - response to information processed through stimulation of effectors
• Two Anatomical Divisions of the Nervous System

  • Central Nervous System - consists of brain and spinal cord, responsible for integrating, processing, and coordinating sensory data and motor commands
  • Peripheral Nervous System - consists all the neural tissue outside CNS (cranial, spinal and peripheral nerves), ganglia -> small group of nerve cells outside CNS
• Division of the Peripheral Nervous System

  • Somatic Nervous System - controls skeletal muscle contraction
  • Autonomic Nervous System - provides automatic regulation of smooth muscle, cardiac muscle, glands, and adipose tissue, parts: sympathetic - fight / flight, parasympathetic - relaxed
• Sensory Division of the Peripheral Nervous System

  • Somatic Sensory Receptors - provide position, touch, pressure, pain, and temperature sensations
  • Special Sensory Receptors - provides sensations of smell, taste, vision, balance, and hearing
  • Visceral Sensory Receptors - monitors internal organs
• Receptors


  Sensory structures that detect changes in the internal or external environment
• Effectors


  Target organs whose activities changes in response to neural commands
• Histology of Nervous Tissue

  • Neurons / Nerve Cell - processing, transfer, and storage of information
  • Neuroglia / Glial Cell - support, regulation and protection of neurons
• Neuron Structure


  1. Cell Body - also called perikaryon / soma, contains the nucleus and mitochondria, ribosomes, and other organelles, primarily a tropic center / nutritive center and genetic center of a neuron

  2. Dendrites - stimulated by environmental changes or the activities of other cells, elongated processes extending from soma, specialized in receiving stimuli from the environment, from the sensory epithelial, or from other neurons at unique sites (synapses)

  3. Axon - conducts nerve impulses (action potential) towards synaptic terminals, specialized in generating and conducting nerve impulses to other cells (nerve, muscle or glands), axon hillock -> starts at this short pyramid-shaped initial segment, myelinated axons -> axons surrounded by the myelin sheath, Nodes of Ranvier -> unmyelinated gaps left when myelin laid down in segments (internodes) along the axon

  4. Synaptic Terminal / Synapse - unique sites in the neuron that send stimuli, area where neuron communicates with another cell (muscle cell, another neuron attached or close to it)
• Types of Synapse


  • Pre-synaptic Cell - neuron that sends message
  • Postsynaptic Cell - neuron that receives message
  • Synaptic Cleft - small gap that separates pre-synaptic membrane and postsynaptic membrane
  • Synaptic Knob - synaptic terminals or terminal buttons, expanded portion of axon of presynaptic neuron, contains vesicles of neurotransmitters
• Neuron Classification: Structural
• Tic terminals


  Specialized in generating and conducting nerve impulses to other cells (nerve, muscle or glands)
• Axon hillock


  Starts at this short pyramid-shaped initial segment
• Myelinated axons


  • Axons surrounded by the myelin sheath
  • Presence of myelin speeds up the transmission of action potentials along the axon
• Nodes of Ranvier


  • Unmyelinated gaps left when myelin laid down in segments (internodes) along the axon
• Synaptic Terminal / Synapse


  • Unique sites in the neuron that send stimuli
  • Area where neuron communicates with another cell (muscle cell, another neuron attached or close to it)
• Types of synapse


  • Pre-synaptic Cell
  • Postsynaptic Cell
  • Synaptic Cleft
  • Synaptic Knob
• Synaptic Knob

  • Expanded portion of axon of presynaptic neuron
  • Contains vesicles of neurotransmitters