Chapter 11 and 12

• Fatigue


  The decreased capacity to do work and the reduced efficiency of performance that normally follows a period of activity
• Mechanisms underlying fatigue


  1. Acidosis and ATP depletion due to either increased ATP consumption or decreased production

  2. Decreased effectiveness of Ca2+ on actin and overall less Ca2+ release from the sarcoplasmic reticulum

  3. Oxidative stress leading to build up of excess reactive oxygen species (ROS) causing breakdown of proteins, lipids, or nucleic acids and triggering interleukin (IL)-6, a mediator of inflammation

  4. Local inflammatory reaction with presence of immune system intermediates increasing perception of pain as a signal to protect tissues from further damage
• Muscle Hypertrophy


  Increase in size, number of myofibrils, sarcomeres, nuclei from satellite cells, mitochondria, and blood vessels
• Training the Muscles


  1. Better neuromuscular coordination

  2. Improved metabolism

  3. Increased circulation

  4. More efficient respiration

  5. Increase in connective tissues

  6. Greater capacity for heart to pump blood
• Isometric contraction


  Increases the tension in the muscle without changing its length
• Isotonic contraction


  Has a constant amount of tension while decreasing the length of the muscle
• Concentric contraction


  Isotonic contraction in which muscle tension increases as the muscle shortens
• Eccentric contraction


  Contraction in which tension is maintained in a muscle, but the opposing resistance causes the muscle to lengthen
• Muscle Tone


  Constant tension produced by muscles of the body over long periods of time, responsible for keeping the back, legs, head, and abdomen in position
• Effects of Aging


  • Reduction in muscle mass
  • Slower response time for muscle contraction
  • Reduction in stamina
  • Increased recovery time
  • Fast-twitch muscle fibers decrease in number more rapidly than slow-twitch fibers
  • Fewer action potentials produced in muscle fibers
  • Decrease in the number of motor neurons
  • Decrease in the density of capillaries in skeletal muscles
• Effects of Exercise


  • Intense anaerobic exercise increases muscular strength and mass, causing fast twitch muscle fibers to enlarge more
  • Aerobic exercise increases vascularity and causes slow-twitch muscle fibers to enlarge more
  • Aerobic training can convert some fast-twitch fatigue-prone fibers to fatigue-resistant fibers
  • Type I muscle fibers cannot be converted to type II, and vice versa
  • Unused muscle atrophies, but severe atrophy can lead to an irreversible decrease in muscle fibers and paralysis
  • Training increases muscle strength through increased size and number of motor units
• Heat is released as some energy during muscle contraction, contributing to normal body temperature
• Visceral smooth muscle


  More common type of smooth muscle, found in digestive, reproductive, and urinary tracts
• Multiunit smooth muscle


  Occurs in sheets, small bundles, and single cells in various configurations
• Cardiac muscle


  Adjacent cells join to form branching muscle fibers by specialized cell-to-cell attachments called intercalated disks
• After exercise, increased metabolism from recovery oxygen consumption helps keep body temperature elevated, but sweating and vasodilation speed heat loss to maintain normal range
• The central nervous system (CNS) consists of the brain and spinal cord, while the peripheral nervous system (PNS) consists of nerves, ganglia, and receptors

  
• Sensory division of PNS

  Carries information from receptors to the CNS

  
• Motor division of PNS


  Carries commands from the CNS to effectors
• Nervous system


  Uses electrical and chemical signals to control body functions
• Endocrine system


  Uses chemical signals to control body functions
• Functions of the Nervous System

  • Regulates and coordinates functions to maintain homeostasis
  • Composed of neurons and glial cells
  • Neurons send electrical signals using axons
  • Nerves are collections of axons
  • Cranial nerves originate from the brain, spinal nerves from the spinal cord
  • Ganglia are clusters of neuron cell bodies outside the CNS
  • Plexuses are bundles of nerves outside the CNS
  • Glial cells serve supportive functions for neurons

  
• Functions of the Nervous System

  • Maintaining homeostasis
  • Receiving sensory input
  • Integrating information
  • Controlling muscles and glands
  • Establishing and maintaining mental activity
• Central Nervous System (CNS)


  Receives information from and sends information to the body

  
• Peripheral Nervous System (PNS)


  Detects stimuli and sends information to the CNS, then communicates messages from the CNS to the body

  
• The sensory division of the PNS transmits electrical signals from receptors toward the CNS, while the motor division transmits signals from the CNS to effector organs

  
• Somatic Nervous System


  The voluntary division of the motor system that allows conscious control of skeletal muscles
• Autonomic Nervous System


  The involuntary division of the motor system that regulates activities without conscious control, such as cardiac and smooth muscle contractions and gland secretions
• Sympathetic Division


  Readies the body for physical activity, the "fight-or-flight" division
• Parasympathetic Division


  Regulates resting functions like digestion and slowing heart rate, the "rest-and-digest" division
• Enteric Nervous System


  Consists of neuronal networks within the digestive tract wall
• The nervous system is composed of an estimated 100 billion neurons
• Autonomic nervous system (ANS)


  Involuntary division of the motor division that regulates activities without our conscious control such as contractions of cardiac muscle and smooth muscle and secretions by certain glands
• Major subdivisions of the ANS


  • Sympathetic division
  • Parasympathetic division
• Sympathetic division


  Readies the body for physical activity, also called the fight-or-flight division
• Parasympathetic division


  Regulates resting functions, such as digesting food or slowing the heart rate, also called the rest-and digest division
• Enteric nervous system (ENS)


  Third division of the nervous system consisting of neuronal networks within the wall of the digestive tract
• There are two cell types that make up the nervous system: neurons and glial cells
• There are an estimated 100 billion neurons in our body, yet glial cells account for over half of the brain's weight, and there can be 10 to 50 times more glial cells than neurons in various parts of the brain
• Neurons


  • They are the electrically excitable cells of the nervous system
  • There are three parts to most types of neuron: (1) a neuron cell body, (2) dendrites, and (3) a single axon