HUBS M3 Nerves & Muscles

• Integrating and coordinating


  1. Senses environment

  2. Produces an appropriate response

  3. Matches sensory environment with our body's needs
• Sensory experience


  1. Integration

  2. Coordination

  3. Response
• Basic anatomical organisation of the nervous system

  • Brain
  • Spinal cord
  • Peripheral nerves & ganglia
• Composed of


  • Neurons
  • Glia
• Consists of


  • Central Nervous System (CNS)
  • Peripheral Nervous System (PNS) [including ENS]
• Cells of the nervous system: (i) Neurons (nerve cells)


  • Cells specialised for transmission of information
  • Four (4) morphological types
• Cells of the nervous system: (ii) Glia (Greek: glue)


  • Support for neurons
  • Five basic types - 4 in CNS, 1 in PNS
  • Each type has specific function
• Structural Components of Neurons

  • Cell body
  • Axon
  • Axon terminal(s)
  • Dendrites
• Cell bodies and axons are segregated

  • Nucleus (pl. = Nuclei)
  • Tract
  • Grey matter
  • White matter
  • Ganglion (pl = ganglia)
  • Nerve
• Functional components (zones) of Neurons

  1. Input zone

  2. Summation zone

  3. Conduction zone

  4. Output zone
• Axon hillock: Anatomical location where inputs are summated before action potential
• Specialised neuron morphologies


  • Multipolar
  • Bipolar
  • Unipolar
  • Anaxonic
• Action potential


  1. Inputs summated

  2. Action potential
• Cells of the nervous system

  • Specialised for specific tasks
  • So they look different
• Myelin sheath in the CNS

  Made by oligodendrocytes
• Information that travels into the CNS

  • Afferent
  • Ascending
• Morphological types of neurons

  • Multipolar
  • Bipolar
  • Unipolar
  • Anaxonic (axonless)
• Part of a neuron that makes the decision about whether to propagate an action potential in response to inputs

  Axon hillock
• Multipolar neurons


  • Multiple processes emanate from the cell body
• Bipolar neurons


  • Two processes emanate from the cell body
• Somatic


  The stuff we are aware of, have control over
• Unipolar neurons


  • One process emanates from the cell body, then branches into dendrite and axon
• Autonomic


  The stuff we are not aware of, have no control over
• Anaxonic (axonless) neurons


  • No distinct axon
  • All processes look alike
• Voluntary movement


  1. Two neurons between brain & effector

  2. Upper motor neuron

  3. Lower motor neuron
• Central Nervous System Glia

  • Astrocytes
  • Ependymal cells
  • Oligodendrocytes
  • Microglia
• Upper motor neuron


  • Cell body in brain, axon in spinal cord
  • Axon is myelinated

  
• Astrocytes


  • Supply nutrients to neurons
  • Ensheath blood capillaries
  • Injury response
• Lower motor neuron


  • Cell body in spinal cord, axon in spinal nerve
  • Axon is myelinated
• Ependymal cells


  • Immune cells of the CNS
  • Engulf microorganisms and debris
  • Line fluid-filled spaces of brain and spinal cord
• Neurotransmitter at neuromuscular junction

  Acetylcholine (ACh)
• Oligodendrocytes


  • Have cilia (hair-like processes) to circulate CSF
  • Support nerve fibres
  • Ensheath them with myelin
• Effector for somatic efferent division

  Skeletal muscle
• Autonomic nervous system


  • Involuntary control
  • Two divisions: Sympathetic and Parasympathetic
• Microglia


  • Supply nutrients to neurons
  • Ensheath blood capillaries
• Autonomic effectors


  • Smooth muscle, cardiac muscle, glands, adipose (fat) tissue
• Peripheral Nervous System Glia


  • Schwann cells
• Communication between autonomic neurons and effectors


  1. Three neurons between brain and effector

  2. Neuron #1: Cell body in brain, axon in CNS

  3. Neuron #2: Cell body in CNS, axon in PNS

  4. Neuron #3: Cell body in PNS, axon in PNS
• Schwann cells


  • Support peripheral nerve fibres
  • Ensheath them with myelin
  • Similar to oligodendrocytes (CNS)
• Pre-ganglionic neuron


  Cell body in CNS, axon extends in PNS, myelinated, synapse in autonomic ganglion, neurotransmitter = acetylcholine (ACh)