Nervous

• 2 MAJOR DIVISIONS:

  CENTRAL NERVOUS SYSTEM (CNS)

  • consist of the BRAIN and SPINAL CORD

  PERIPHERAL NERVOUS SYSTEM (PNS)

  • consists of all the nervous tissues outside the CNS (nerves and ganglia)
  • Functions to link the CNS with the various parts of the body.
• NEURONS

  • AKA: nerve cells
  • Receive stimuli, conduct action potentials, and transmit signals to the other neurons or effector organs.
  • 3 PARTS OF A NEURON

  1. CELL BODY
  2. AXONS
  3. DENTRITES
• CELL BODY

  • Contains a single nucleus
• AXON

  • A single long cell process extending from the neuron cell body.
  • Can be surrounded by a highly specialized layer cells called the myelin sheath
• DENDRITES

  • Are short, often highly branching cytoplasmic extensions that are tapered from their bases at the neuron cell body to their tip.
  • receive information from other neurons or from sensory receptors and transmit the information toward the neuron cell bod
• GLIAL CELLS

  • AKA: NEUROGLIA
  • Are the primarily supportive cells of the CNS and PNS
  • DO NOT CONDUCT action potentials
  • More numerous than neurons
  • Retain the ability to divide
• FIVE TYPES OF GLIAL CELLS

  • ASTROCYTES
  • EPENDYMAL
  • MICROGLIA
  • OLIGODENDROCYTES
  • SCHWANN CELLS
• SCHWANN CELLS

  DESCRIPTION

  • Single cells surrounding axons

  FUNCTION

  • Form myelin sheaths around axons or enclose unmyelinated axons in the PNS
• OLIGODENDROCYKES

  DESCRIPTION

  • Cells with processes that can surround several axons

  FUNCTION

  • Cell process form myelin sheaths around axons or enclose unmyelinated axons in the CNS
• MICROGLIA

  DESCRIPTION

  • Small, mobile cells

  FUNCTION

  • Protect CNS from infection
  • become phagocytic in response to inflammation
• EPIDYMAL

  DESCRIPTION

  • Epithelial-like

  FUNCTION

  • Lines ventricles of the brain and central canal of the spinal cord
  • circulate cerebrospinal fluid (CSF)
  • Some form choroid plexuses, which produce CSF
• ASTROCYTES

  DESCRIPTION

  • Highly Branched

  FUNCTION

  • Provides structural suppor
  • Regulate neuronal signaling
  • Contribute to blood brain barrier
  • Help with neural tissue repair
• MYELIN SHEATHS

  • Are specialized layers that wrap around the axons of some neurons.

  MYELIN

  • is an excellent insulator that prevents almost all ion movement across the cell membrane

  MYELINATION

  • of an axon increases the speed and efficiency of action potential generation along the axon.
• SPINAL CORD

  • Extends from the foramen magnum at the base of the skull to the second lumbar vertebrae.

  Spinal nerves

  • communicate between the spinal cord and the body.
• Spinal nerves communicate between the spinal cord and the body.
• BRAINSTEM

  • Connects the spinal cord to the remainder of the brain.
  • Consist of the:

  – medulla oblongata

  – pons

  – midbrain
• MEDULLA OBLONGATA

  • The most inferior portion of the brainstem and is continuous with the spinal cord.
  • Extends from the level of the foramen magnum to the pons.
  • contains the ascending and descending nerve tracts.
  • Contains discrete nuclei with specific functions, such as regulation of the heart rate and blood vessel diameter, breathing, swallowing, vomiting, coughing, sneezing, balance and coordination
• PONS

  • found superior of the medulla
  • Contains ascending and descending nerve tracts, as well as several nuclei.
  • some of the nuclei in the pons relay information between the cerebrum and the cerebellum.
  • Several nuclei of the medulla oblongata extendminto the lower part of the pons, so functions such as breathing, swallowing and balanced are controlled in the lower pons, as well as in the medulla oblongata.
  • Other nuclei in the pons control functions such as chewing and salivation
• MIDBRAIN

  • the smallest region of the brainstem
  • The dorsal part of the midbrain consist of four mounds called colliculi.
  • The midbrain contains nuclei involved in coordinating eye movements and controlling pupil diameter and lens
  • INFERIOR COLLICULI -Major relay centers for the auditory nerve pathways in the CNS
  • SUPERIOR COLLICULI -Involved in visual in visual reflexes and receive touch and auditory input.
• DIENCEPHALON

  THALAMUS

  the largest part of the diencephalon

  • consists of cluster of nuclei and is shaped somewhat like a yo-yo, with two large, lateral parts connected in the center by a small interthalamic adhesion.
  • The thalamus influences mood and registers an unlocalized, uncomfortable perception of pain
• DIENCEPHALON

  EPITHALAMUS

  • small area superior and posterior to the thalamus.
  • Consists of a few small nuclei, which are involved in the emotional and visceral response to odors, and the pineal gland.
  • PINEAL GLAND - An endocrine gland that may influence the onset of puberty and may play a role in controlling some long term cycles that are influenced by the light/dark cycle.
• DIENCEPHALON

  HYPOTHALAMUS

  • most inferior part of the diencephalon
  • Contains several nuclei that are very important in maintaining homeostasis.
  • plays a central role in the control of body temperature, hunger and thirst.
  • Plays a major role in controlling the secretion of hormones from the pituitary gland.

  INFUNDIBULUM - extends from the floor of the

  hypothalamus to the pituitary gland.

  MAMMILLARY BODIES - Externally visible swellings on the posterior portion of the hypothalamus and are involved in emotional response and in memory.
• DIENCEPHALON

  • the part of the brain of the brain between the brainstem and the cerebrum.
  • main components are the thalamus, the epithalamus, and the hypothalamus.
• CEREBELLUM

  • Internally, consists of gray nuclei and white nerve tracts.
  • Cerebellum is involved in maintaining balance and mmuscle tone and in coordinating fine motor movement.
  • If damaged, muscle tone decreases, and fine motor movements become very clumsy.