Nervous system

• Nervous system


  Brain, Spinal Column
• Central Nervous System (CNS)


  Brain, Spinal cord
• Peripheral Nervous System (PNS)


  Peripheral sensory and motor nerves
• Neurons


  Nerve cells
• Neuroglial


  Supporting cells
• The nervous system is divided into two; the Central Nervous System (CNS) and Peripheral Nervous System (PNS)
• Central Nervous System


  • Site of processing; responsible for responding to sensory input and forming appropriate response for the motor output
  • Responsible for thought, movement, emotion, breathing, heart rate, hormones, body temperature
• Spinal cord


  • Responsible for sending sensory information from the body to the brain
  • Sending motor commands from the brain to body
  • Coordination of basic reflexes (not all stimuli is processed in the brain)
• Cerebrospinal fluid


  Fluid that bathes the brain and spinal cord; Provides protective cushion around the CNS; Produced in choroid plexus of brain; Vehicle for delivering nutrients to the brain and removing waste; Flows between the cranium and spine to regulate changes in pressure
• Sympathetic division


  Mobilises body systems; Flight or fight responses
• Parasympathetic division


  Conserves energy; Rest and digest responses
• Somatic Nervous System


  Controls voluntary movement
• Autonomic Nervous System


  Controls involuntary responses
• Neurons


  Building blocks of the nervous system; Reception of stimuli and transmission of impulses through physical and electrical forms; They respond to stimuli; can conduct signals; Nourishment and oxygen is provided by neuroglial cells
• Neuron structure


  • Cell body (soma) houses the nucleus, organelles, and ribosomes; Responsible for running life-sustaining processes
  • Dendrites - series of highly branched outgrowths; Receive incoming information from other neurons; Increase the cell's capacity to receive signals
  • Axons - long processes that extend from the cell body; Carry outgoing signals to target cells; Impulses from neural body towards dendrites or cell body of next neuron
• Axon components


  • Axon Hillock - Bridge between soma and axon; Depolarization along the dendrites must reach "threshold potential" at the AH order for an AP propagation
  • Collaterals - Allows neurons to connect with multiple synaptic targets
  • Axon Terminal - Site of the release of neurotransmitter
• Myelin sheath


  Insulating layer around nerves made up of protein and lipid; Myelinated neurons present in white matter in the brain and spinal cord; Aids in neurotransmitter release along the length of an axon; Allows electrical impulses to transmit quickly and efficiently in a process "saltatory conduction"
• Nodes of Ranvier


  Regions in the axon of myelinated neuron that are not insulated by myelin
• Neuroglia


  Supports cells that nourish neurons, insulate its axons, and regulate extracellular fluid (ECF) surrounding neurons
• Types of neuroglia


  • Oligodendrocytes
  • Ependymal cells
  • Astrocytes
  • Microglial cells
  • Schwann cells
  • Satellite cells
• Resting membrane potential


  Outside of cell is more + (Na+), Inside of cell is more - (K+); Leak ion channels (K+ channels) are always open
• Action potentials


  Electricity that cause depolarization and repolarization; Change resting membrane potential by activating gated ion channels; Local current - movement of Na+ which causes inside of cell to be more positive (depolarize); If enough Na+ enters then threshold is reached and more Na+ channels open; Once threshold is reached all or none law applies; Action potentials continue until Na channels close, K+ channels open, and repolarization occurs
• Synapse


  Specialized junction between two neurons which alters the electrical and chemical activity of the other
• Electrical synapse


  Presynaptic and postsynaptic neurons are joined by gap junctions; Allows local current to flow directly from one neuron to another; Impulse travels without delay or loss of signal strength
• Chemical synapse


  Signals are transmitted across a synaptic cleft by means of chemical neurotransmitter; Action potential at the synaptic terminal of the axon triggers influx of Ca2+; Synaptic vesicles with neurotransmitter fuse with presynaptic membrane; Neurotransmitters released in the synaptic cleft bind to receptors on the postsynaptic membrane; Ion channels open resulting influx of ions across postsynaptic membrane
• Presynaptic neurons are the ones that conduct signal towards the next synapse
• Postsynaptic neurons are the ones that conduct signal away the next synapse
• Postsynaptic


  The ones that conduct signal away the next synapse
• Synapse


  The specialized junction between two neurons which alters the electrical and chemical activity of the other
• BASED ON IMPULSE DIRECTION


  • PRESYNAPTIC NEURONS
  • POSTSYNAPTIC NEURONS
• BASED ON MEDIUM


  • ELECTRICAL SYNAPSE
  • CHEMICAL SYNAPSE
• Electrical Synapse


  • Allows local current to flow directly from one neuron to another; impulse travels without delay or loss of signal strength
• Chemical Synapse


  1. Action potential at the synaptic terminal of the axon triggers influx of Ca2+

  2. Synaptic vesicles with neurotransmitter fuse with presynaptic membrane

  3. Neurotransmitters released in the synaptic cleft bind to receptors on the postsynaptic membrane

  4. Ion channels open resulting influx of ions across the postsynaptic membrane
• Neurotransmitters


  • ACETYLCHOLINE
  • NOREPINEPHRINE
  • SEROTONIN
  • DOPAMINE
  • GAMMA AMINOBUTYRIC ACID
  • GLYCINE
  • ENDORPHINS
• ACETYLCHOLINE


  CNS synapses, ANS synapses, neuromuscular junctions
• NOREPINEPHRINE


  Select CNS synapses, some AND synapses
• SEROTONIN


  CNS synapses
• DOPAMINE


  Select CNS synapses, some AND synapses
• GAMMA AMINOBUTYRIC ACID


  CNS synapses, Inhibitory
• GLYCINE


  CNS synapses, Inhibitory