Biology: Nervous System

• The Nervous System is a complex network of neurons and cells that carry messages to and from the brain and spinal cord to various parts of the body.
• Neuron


  The basic functional unit of the nervous system. It carries messages to

  and from the different parts of the body from one neuron to another.
• Dendrites


  Tree-like structures that extend away from the cell body to receive

  messages from other neurons
• Axon


  Is a tube-like structure that propagates the integrated signal to

  specialized endings
• Information from one neuron flows to another

  neuron across a synapse.
• A Nerve Impulse


  Is an electrochemical charge that travels from one end of a nerve cell to the next
• Myelin Sheath


  acts as an insulator to minimize dissipation of the electrical signal as it travels down the axon, greatly increasing the speed on conduction.
• Sensory Neurons


  Conduct information from the sensory receptors in the various parts of the body to the central nervous system. Most sensory neurons are pseudounipolar.
• True unipolar neurons are not found in the adult vertebrate

  nervous system. They are present in invertebrates.
• Motor Neurons


  Carry signals from the central nervous system to the specific body parts that carry out the response. The structure of this is multipolar.
• Interneuron


  Located in the CNS, they operate locally, meaning their axons connect only with nearby sensory or motor neurons. Concerned with thinking, learning, and memory.
• Brain (CNS)


  Part of the central nervous system that is contained in the cranial cavity of the skull.
• Meninges


  Membrane covering the brain and spinal cord.
• Cerebrospinal Fluid


  Tissue fluid of CNS. Carries nutrients to CNS neurons and removes waste products.
• Medulla Oblangata


  Regulates vital function of heart, blood pressure, and respiration. Reflex centers for coughing, sneezing, swallowing, vomiting.
• Pons


  Contains respiratory centers working with those in medulla.
• Midbrain


  Contains reflex centers for visual, auditory, and equilibrium.
• Cerebellum


  Concerned with movement and motor coordination. Functions below the level of conscious thought.
• Hypothalamus

  • Production of releasing hormones
  • Regulates body temperature
  • Regulates food intake and emotions
  • Regulates circadian rhythm
• Thalamus

  • Concerned with sensations
  • Awareness of pain or unpleasant sensation but inability to localize
  • Contributes to alertness, awareness, and memory
• Cerebrum

  • Largest part of the brain
  • With two hemispheres connected by corpus callosum
• Frontal Lobe

  • Voluntary movements
  • Social behavior, memory, judgement, and reasoning
  • Motor speech (Broca’s area)
• Parietal Lobe

  • General sensory area
  • Taste area
  • Speech area for thought before speech
  • Reading comprehension
• Temporal Lobe

  • Auditory area
  • Olfactory area
  • Wernicke’s area for sound interpretation
  • Understanding, language, memory
• Occipital Lobe

  • Visual area
  • Visual interpretation for color and spatial relationships
• Corpus Callosum


  Connects the two cerebral hemispheres.
• Association Areas


  -Present in all lobes, but not for motor or sensation

  -Abstract thinking, reasoning, learning, memory, sense of human

  -Personality
• Spinal Cord

  • Enclosed within the vertebral column
  • Transmits impulses to and from the brain
  • Communicates through the spinal nerves
• Peripheral Nervous System


  Consists of the cranial nerves and spinal nerves

  Is the connection between the central nervous system and the rest of the body
• The 31 Pairs of Spinal Nerves:

  8 Cervical

  12 Thoracic

  5 Lumbar

  5 Sacral

  1 Coccygeal
• Reflexes


  An involuntary response to a stimulus

  An automatic action stimulated by a specific change of some kind
• Reflex action does not involve the brain.
• Receptor (reflex arc)


  Detect a stimulus and generate impulses.
• Sensory Neuron (reflex arc)


  Transmit impulses from receptors to CNS.
• Central Nervous System (reflex arc)


  Information is processed with interneurons and/or more synapses in spinal cord.
• Motor Neurons (reflex arc)


  Transmit impulses from CNS to effectors.
• Effector (reflex arc)


  Performs response
• Withdrawal Reflex


  Painful or harmful situations will cause a body part to move away from the stimulus.
• Protective Reflex


  Brain knows the reflex has taken place and learns from the experience.
• Cranial Nerves

  • 12 pairs emerging from the brain
  • Concerned with vision, hearing, taste, smell, equilibrium, and many other functions