nervous system

• Nervous System


  Cellular network that mediates information processing and regulates response to stimuli

  
• Nervous system


  • Information processing (brains and ganglia)
  • Specialized nervous tissue (Neurons and glia)
  • Action potentials
  • Synapses

  
• Sensory neurons


  Detect external and internal stimuli

  
• Interneurons


  Receive and integrate sensory information
• Motor neurons


  Relay messages from interneurons and trigger effectors (muscles or glands)

  
• Membrane potential


  Voltage (difference in electrical charge) across the plasma membrane
• Resting potential


  Membrane potential of a neuron not sending signals
• Action potential


  Massive change in membrane voltage due to rapid changes in ion concentrations
• Action potential


  1. Initial depolarization

  2. Voltage gated Na+ channels open

  3. Voltage gated K+ channels open

  4. Membrane potential undershoots and resting potential reestablished

  
• Nervous system organization


  Vertebrate nervous system

  
• Action potential conduction


  • Unidirectional
• Refractory period


  Temporary inactivation of Na+ channels after an action potential
• Central nervous system (CNS)


  • Brain and spinal cord
  • Spinal cord conveys information to and from the brain
  • Spinal cord can produce reflexes independent of the brain

  
• Axons


  • Speed of action potential increases with diameter
  • Myelin sheaths greatly increase speed of action potentials
• Peripheral nervous system (PNS)


  • Nerves and ganglia
  • Sensory and motor neurons relaying messages to and from brain and spinal cord

  
• Calcium signalling releases neurotransmitters
• Afferent neurons


  • Transmit information to the CNS
• Efferent neurons


  • Transmit information away from the CNS
• Excitatory postsynaptic potentials 


  Depolarizations that bring the membrane potential toward threshold

  
• Inhibitory postsynaptic potentials

  Hyperpolarizations that move the membrane potential farther from threshold

  
• Efferent systems


  • Motor system: voluntary; carries signals to skeletal muscles
  • Autonomic nervous system: generally involuntary; regulates smooth and cardiac muscles

  
• Summation of postsynaptic potentials


  EPSPs and IPSPs are 'summed' to generate (or not generate) an action potential
• Cerebellum


  • Coordinates movement and balance
  • Receives sensory information about position of joints and muscles
  • Regulates motor function i.e. hand-eye coordination
• Neurotransmitters


  • Can be excitatory, inhibitory, or both
  • Can trigger 'feelings'
  • Can be mimicked
  • Can be manipulated
• Diencephalon and brainstem


  • Diencephalon: thalamus, hypothalamus, pituitary
  • Brainstem: midbrain, pons and medulla oblongata
  • Direct information between spinal cord and cerebrum; regulate homeostasis, hunger, thirst, social and sex behaviors and 'fight or flight' response; HPE axis

  
• Neurotransmitter 'removal'


  1. Reuptake

  2. Enzymatic degradation
• Limbic system


  • Includes regions of diencephalon, brainstem and cerebrum
  • Functions in emotion, memory, learning, fear motivation, behavior, and olfaction

  
• Neuronal communication between the brain and the muscles of the leg is best conceptualized as electrical and chemical signaling

  
• Cerebrum


  • Four 'lobes': frontal, temporal, occipital and parietal
  • Functions in awareness, language, cognition, memory, and consciousness

  
• Cerebrum: somatosensory cortex and motor cortex


  • Cerebrum receives input from sensory organs, including touch, and sends output signals in response
  • Thalamus (limbic system) directs different types of input to distinct locations in the cerebrum

  
• Cerebrum: brain lateralization


  • Left hemisphere: language, math, logical operations
  • Right hemisphere: pattern recognition, spatial relations, nonverbal thinking
  • Communicate through the corpus callosum
• Neural plasticity


  The ability of neurons to strengthen (or weaken) connections with experience
• Learning and memory


  Are the result of neural plasticity
• Memory formation


  • Mediated by the hippocampus (limbic system)
  • Short-term memory: involves neurons in hippocampus
  • Long-term memory: involves neurons in hippocampus and cerebrum
  • Consolidation of memory is thought to occur during sleep
• Disorders of the nervous system

  • Schizophrenia
  • Depression
  • Drug addiction
  • Alzheimer's disease
  • Parkinson's disease