Nervous Tissue

• What types of neurons are involved with the special senses?

  Sensory neurons for smell, vision, hearing, balance, taste
• What do motor neurons control in the face?

  Muscles of the face, jaw, tongue
• Which muscles do motor neurons control related to the larynx and pharynx?

  Muscles of the larynx and pharynx
• What sensations do sensory neurons provide from the face?

  Sensation from face, oral/nasal cavity, teeth
• What do autonomic neurons regulate?

  Secretion of glands and contraction of smooth muscles
• What carries the axons of neurons that innervate head structures?

  Cranial nerves
• How many cranial nerves are there?

  Twelve cranial nerves
• Where do cranial nerves emerge from?

  Midbrain, pons, and medulla

  
• What is the most relevant cranial nerve for dentistry?

  Trigeminal nerve (cranial nerve V)
• How many main branches does the trigeminal nerve have?

  Three main branches

  
• What are the branches of the trigeminal nerve?

  Ophthalmic, maxillary, mandibular

  
• What do the ophthalmic and maxillary branches mainly contain?

  Axons of sensory neurons
• What does the mandibular branch contain?

  Motor, sensory, sympathetic, and parasympathetic axons
• Where are the cell bodies of trigeminal nerve motor neurons located?

  In the trigeminal motor nucleus of the pons
• Where are the cell bodies of trigeminal nerve sensory neurons located?

  In the trigeminal ganglion outside the brain
• What is the role of postganglionic sympathetic neurons in the trigeminal nerve?

  Regulate smooth muscle and gland function
• Where are the cell bodies of postganglionic sympathetic neurons located?

  In the superior cervical ganglion
• Where are the cell bodies of preganglionic parasympathetic neurons located?

  In the superior salivatory nucleus of cranial nerve VII
• What is the diameter range of Aα fibres?

  13 - 20 µm
• What is the conduction speed of Aβ fibres?

  35 - 75 m/sec
• What factors affect axon potential conduction velocity?

  Nerve fibre diameter and myelin sheath thickness

  
• What type of axons do postganglionic sympathetic neurons resemble?

  C-fibres
• What type of axons do preganglionic parasympathetic neurons resemble?

  Aδ-fibres
• What cells myelinate axons outside the CNS?

  Schwann cells

  
• What are the two types of Schwann cells?

  Myelinating and non-myelinating Schwann cells
• What do myelinating Schwann cells do?

  Form the myelin sheath around axons

  
• What do non-myelinating Schwann cells do?

  Wrap around non-myelinated axons

  
• What myelinates axons in the CNS?

  Oligodendrocytes
• What is the composition of the myelin sheath?

  Over 70% lipids and specific proteins
• What is the role of Schwann cells in axon metabolism?

  Provide essential metabolites to axons

  
• What neurotrophic factors do Schwann cells synthesize?

  NGF, BDNF, and GDNF
• What role do Schwann cells play in axon regeneration?

  Promote regrowth of axons after damage
• What is the structure of cell membranes?

  Phospholipid bilayer isolating cytosol from fluid
• What do ion channels control?

  Flow of ions across the phospholipid bilayer
• What opens ion channels?

  Binding of ligands or voltage changes
• How do individual ions move across the membrane?

  From high concentration to low concentration
• Where are sodium ions more concentrated?

  Outside the cell
• What is the term for the fluid inside a cell?

  Cell cytosol
• What do ion channels control?

  The flow of ions across the membrane
• What type of proteins are ion channels?

  Large multi-domain proteins