Animal

• Components of mammalian nervous system

  • Central nervous system (brain and spinal cord)
  • Peripheral nervous system (sensory and motor neurones)
  • Autonomic nervous system (sympathetic and parasympathetic)
  • Somatic nervous system (voluntary control of skeletal muscles)
• Autonomic nervous system


  Controls homeostatic mechanisms and response to stress. Sympathetic and parasympathetic systems have opposing effects.
• Parts of the brain

  • Cerebrum
  • Cerebellum
  • Hypothalamus
  • Medulla oblongata
• Cerebrum


  Largest part of brain, involved in controlling vision, thinking, learning, emotions, and voluntary body control.
• If the brain perceives a threat, it stimulates the stress response involving adrenaline, triggering physiological changes to prepare the body to tackle the threat.
• Adrenaline


  Cannot cross the plasma membrane, so it must interact with cell surface receptors (adrenergic receptors). Binding activates a signalling pathway involving adenyl cyclase, cAMP, and kinase enzymes.
• Sinoatrial node


  Pacemaker of the heart, initiates the wave of electrical stimulation that causes the atria to contract.
• Accelerator nerve (sympathetic)


  Delivers higher frequency impulses to increase heart rate
• Vagus nerve (parasympathetic)


  Delivers lower frequency impulses to decrease heart rate
• Factors that increase heart rate

  • Low pH from high CO2, detected by chemoreceptors
  • Muscle movement detected by stretch receptors
  • Decrease in blood pressure detected by baroreceptors
  • Adrenaline release
• Tendons


  Non-elastic tissue connecting muscles to bones

  
• Ligaments


  Elastic tissue joining bones, determining range of movement at joints
• Joints


  Areas where two bones are attached, made of fibrous connective tissue and cartilage
• Skeletal muscles


  Muscles attached to bones, arranged in antagonistic pairs
• Antagonistic muscle pairs


  Pairs of muscles that pull in opposite directions, like flexors and extensors
• Components of skeletal muscle

  • Muscle fibres enclosed in sarcolemma
  • T-tubules in sarcolemma
  • Sarcoplasmic reticulum
  • Myofibrils with actin and myosin filaments
  • Sarcomeres

  
• Muscle contraction


  1. Action potential depolarises sarcolemma

  2. Ca2+ released from sarcoplasmic reticulum

  3. Ca2+ binds to troponin, exposing myosin binding sites on actin

  4. Myosin heads pull actin, shortening sarcomere

  5. ATP hydrolysis breaks myosin-actin cross-bridges

  
• Slow twitch muscle fibres

  • Adapted for slow, sustained contractions, contain many mitochondria and myoglobin, dark in colour
• Fast twitch muscle fibres


  • Adapted for rapid, intense contractions, have few mitochondria, lighter in colour
• Sources of ATP for muscle contraction

  • Oxidative phosphorylation (aerobic respiration)
  • Anaerobic respiration
  • Creatine phosphate