AnaphyLec

• Nervous tissue


  Comprised of neurons and neuroglia

  
• Nervous tissue


  • For internal communication through rapid electrical and chemical signals
  • Coordinating and controlling body activities and processes (e.g., muscle contraction, memory, reasoning)
• Neuron


  • The structural and functional units of the nervous system
  • Receive sensory inputs
  • Send motor commands to our muscles
  • Transform and relay electrical signals

  
• Parts of a neuron


  • Cell body (soma)
  • Dendrites
  • Axon
  • Myelin sheath
  • Node of Ranvier
  • Axon terminal
  • Synaptic end bulb

  
• Cell body (soma)


  Nutritional center of the neuron where macromolecules are produced
• Dendrites


  Receiving or input portion of a neuron, binds chemical messengers from other cells
• Axon


  Long, thin, cylindrical process that conducts and propagates impulses, called action potential, toward another neuron, muscle fiber or gland cell

  
• Myelin sheath


  Insulates the axon to help protect the neuron cell, contains myelinated fiber that speed up transmission of electrical impulses
• Node of Ranvier


  Periodic gap in the insulating sheath (myelin) on the axon of neurons that serves to facilitate the rapid conduction of nerve impulses
• Axon terminal


  Transmit electrical and chemical signal to other neuron cells and effector cells

  
• Synaptic end bulb


  Bulb-shaped structures at the tip of axon terminals, make the connection with the target cell at the synapse
• Structural classification of neurons


  • Unipolar (pseudounipolar)
  • Bipolar
  • Multipolar

  
• Functional classification of neurons


  • Sensory/afferent
  • Motor/efferent
  • Interneuron

  
• Neuroglia


  Supporting cells of neurons, smaller than neurons, 5 to 25 times more numerous, also generate action potential

  
• Neuroglia of the CNS


  • Astrocytes
  • Microglial cells
  • Ependymal cells
  • Oligodendrocytes

  
• Astrocytes


  Star-shaped under microscope, most numerous and largest of the neuroglia, support neurons, create blood-brain barrier, regulate growth and interconnection among neurons, maintain chemical environment for nerve impulses, involved in learning and memory

  
• Microglial cells


  Tiny cells that phagocytize foreign substances and remove dead cells, form a barrier between cerebral spinal fluid and the interstitial fluid, secrete cerebral spinal fluid
• Ependymal cells


  Form simple cuboidal epithelium, possess microvilli and cilia, line the ventricles of the brain and central canal of the spinal cord
• Oligodendrocytes


  Cells that occur in rows along nerve fibers, form and maintain the myelin sheath around the axons in the CNS

  
• Neuroglia of the PNS


  • Satellite cells
  • Schwann cells

  
• Satellite cells


  Provide support, regulate exchanges of materials between neural cell bodies and interstitial fluid
• Schwann cells


  Insulate axons with myelin in the periphery, wrap around a portion of only one axon segment, involved in nerve regeneration, support and maintenance, nutrient transport
• Myelination process


  1. Oligodendrocytes (in the CNS) and Schwann cells (in the PNS) form myelin sheath around axons

  2. Axons without myelin sheath are unmyelinated

  3. Myelin sheath is made of 70% lipid and 20-30% protein, main proteins are myelin basic protein, proteolipid protein, and cyclic nucleotide phosphodiesterase
• Functions of myelin sheath


  • Protection and structural support
  • Metabolic coupling
  • Action potential propagation
• Saltatory conduction


  Rapid transmission of nerve impulses along myelinated axons, where action potentials propagate by jumping from one node of Ranvier to the next
• Factors affecting speed of impulse propagation


  • Amount of myelination
  • Axon diameter
  • Temperature
• Right hemisphere is more on creativity, artistic, and musical skills, while left hemisphere is for logical reasoning and mathematical skills
• Meninges


  Protect and support the central nervous system, produce cerebrospinal fluid that protects the CNS tissue, acts as a shock absorber, and provides nutrients
• Layers of meninges


  • Dura mater
  • Arachnoid membrane
  • Pia mater
• Cerebrum


  Largest part of the brain, nerve center for sensory and motor activities, integrates sensory information, controls motor and sensory information, conscious and unconscious behaviors, feelings, intelligence, and memory
• Lobes of the cerebrum


  • Frontal lobe
  • Temporal lobe
  • Parietal lobe
  • Occipital lobe
• Frontal lobe


  Acts as the executive, responsible for motor function, language, and cognitive processes such as executive function, attention, memory, affect, mood, personality, self-awareness, and social and moral reasoning
• Temporal lobe


  Processes auditory stimuli, plays a significant role in hearing and visual-spatial perception, processes sensory information to retain memories, language, and emotions, contains the hippocampus which is responsible for storing memories, learning, and emotions

  
• Parietal lobe


  For awareness and processing of somatic sensation (e.g., touch, pain, temperature)
• Occipital lobe


  Contains the visual cortex
• Frontal Lobe


  • Acts as boss or the executive among the 3 lobes
  • For mental and physical actions
  • Responsible for motor function, language, and cognitive processes, such as executive function, attention, memory, affect, mood, personality, self-awareness, and social and moral reasoning
• The next 3 lobes are more on sensory functions
• Four major parts of the brain


  • Cerebrum
  • Diencephalon
  • Cerebellum
  • Brainstem
• Cerebrum


  • Largest brain division
  • Consists of telencephalon and diencephalon
  • Plays a role in processing information related to complex cognitive activities, sensory and associative functions, and voluntary motor activities
• Temporal Lobe


  • Process auditory stimuli
  • Plays a significant role in hearing, and visual-spatial perception
  • An essential part of the social brain, as it processes sensory information to retain memories, language, and emotions
  • Hippocampus resides here which is responsible for storing memories, for learning, and emotions