histo nervous - karen

• EPITHELIAL TISSUE

  • Consisting of closely apposed cells without intervening intercellular substances.
  • Epithelia are avascular (no source of blood), but all epithelia "grow" on an underlying layer of vascular connective tissue.
• The connective tissue and the epithelium are separated by a basement membrane.
• The two layers of basement

  membrane are

  • basal lamina
  • lamina fibroreticularis
• Endothelium

  • the internal surfaces of blood and lymph vessels are lined by epithelium.
  • it is where epithelium lines the blood vessels and lymph

  vessels

  • considered as simple squamous
• Mesothelium it is where the epithelium lines the large internal

  cavities
• Simple Squamous Epithelium

  • This type is composed of a single layer of flattened, scale- or plate-like cells. It is quite common in the body.
  • Present in sites of Exchange as Nephrons & Lungs.
  • The nuclei of the epithelial cells are often flattened or ovoid, i.e. egg-shaped, and they are located close to the center of the cells.
• Simple Cuboidal Epithelium

  • Nuclei are round and centrally located.
  • occurs in the small excretory ducts of many glands, the tubules of the kidney and on the surface of the ovaries
  • Example: major salivary glands

  
• Simple Columnar Epithelium - The cells forming a simple

  columnar epithelium are taller than

  they are wide. usually located at

  the same height within the cells -

  often close to the base of the cells

  and are oval.

  
• simple columnar epithelium lines the internal surface of the

  gastrointestinal tract (GIT) from the cardiac of the stomach to the rectum
• Ciliated simple columnar

  epithelium lines the bronchi, uterus

  and oviducts.
• Cilia are specialized for transport

  of fluid or mucus.
• Cilia has a protective role. It is a

  surface modification in apical

  surface
• Microvilli - is also a surface modification found in apical surface

  Shorter and finer than cilia, it is not visible in compound microscope

  • Also called as brush border

  and are not considered as

  motile

  • Increase surface area
• Enterocytes

  The small intestines are lined by a simple columnar epithelium.
• Glycoproteins and glycolipids projects from the surface of microvilli.
• NERVOUS SYSTEM - Master control and communication

  system
• Three Overlapping Functions of the

  Nervous System

  • monitor changes
  • Processes and interprets
  • Dictates a response by activating effector organs
• Basic Divisions of the Nervous System

  • Central Nervous System (CNS)
  • Peripheral Nervous System (PNS)
• Central Nervous System (CNS)

  • Components: Brain and Spinal cord
  • Integrating and Command center
• Peripheral Nervous System (PNS)

  • Components: Nerves and Ganglia
  • Outside the CNS
  • Nerves extending from brain and spinal cord
  • Link all regions of the body to the CNS
• SENSORY INPUT AND MOTOR OUTPUT - Divided according to region they

  serve, divided into two functional division:

  • Somatic body region
  • Visceral body region (Autonomic Nervous System)
• four main subdivisions

  • Somatic sensory
  • Visceral sensory
  • somatic motor
  • visceral motor
• Somatic Sensory - General somatic senses receptors are widely spread

  • Afferent Division, Found in skin
  • Touch, pain, vibration, pressure, and temperature
  • Proprioceptive senses – detect stretch in tendons and muscle
  • Body sense – position and movement of body in space
  • Special somatic senses: Hearing, balance, vision, and smell
• Visceral sensory - Widely felt in digestive, urinary

  tracts, and reproductive organs

  (receptors), Can be considered under somatic

  sensory.

  General visceral senses

  • stretch, pain, temperature, nausea, and hunger
  • Digestive: abdominal pain and cramps
  • Urinary tract: painful urination (pyuria) and burning sensation
  • Reproductive organs: cramps and abdominal pain during menstruation

  Special visceral senses

  • taste
• Somatic motor - Regulation and control of

  contracting muscle

  • Often called “voluntary nervous

  system”

  • signals contraction of skeletal muscles
  • Under voluntary control
  • Efferent Division
• Visceral Motor

  • Often called “involuntary nervous system”
  • Regulates the contraction of smooth and cardiac muscle and gland secretion
  • Makes up autonomic nervous system
  • Controls function of visceral organs
• NERVOUS TISSUE - Cells are densely packed and

  intertwined. Two main cell types:

  • Neurons (principal cells)
  • Neuroglial cells
• Neurons

  • Transmit electrical signals
  • Response to stimulus or transmit impulses through irritability and conductivity functions
• Neuroglial cells

  • Supporting cells
  • Non-excitable
  • Surround and wrap neurons
• Neurons - Basic structural unit of the nervous system, Specialized cells conduct electrical impulses along the plasma membrane
• Special Characteristics of a Neuron

  • Longevity – can live and function for a lifetime
  • Do not divide – fetal neurons lose their ability to undergo mitosis; neural stem cells are an exception
  • High metabolic rate – require abundant oxygen and glucose
• Soma/Perikaryon - also known as the cell body

  • size varies from 5–140μm
  • Contains nucleus, organelles plus other structures
• Chromatophilic bodies - Most distinctive chromatophilic bodies: Nissl bodies are cytoskeleton granular masses and is a part of a well developed rough ER. It is responsible for the protein synthesis along with the Golgi bodies

  • Nissl bodies also synthesize the protein component of the neurotransmitters which are the chemicals used to communicate with other cells
  • Clusters of rough ER and free ribosomes
  • Stain darkly and renew membranes of the cell
• Neurofibrils - bundles of intermediate filaments

  • Form a network between chromatophilic bodies
  • Internal support for neurons It is the cytoskeleton of the neuron
  • Strengthens the synapses (point of contact between neurons)
  • Fix the diameter between dendrites and axons
• 3 types of Neurofibrils:

  • Microfilament
  • intermediate filament
  • microtubules
• Ganglia - clusters of cell bodies in PNS,

  • Nucleus/ nuclei part of

  ganglia in CNS
• Processes- Cytoplasmic Extensions

  Dendrites - carry impulses towards the CNS

  • Extensively branching from the cell body
  • Transmit electrical signals (graded potentials) toward the cell body
  • Chromatophilic bodies – only extend into the basal part of dendrites
  • Function as receptive sites
• Axons

  • Neuron has only one axon, but it can branch
  • Impulse generator and conductor
  • Transmits action potentials away from the cell body
  • No protein synthesis in axon because there is no nissl bodies present
  • Branches along length are infrequent
  • Outer covering is called neurilemmal sheath, while the inner covering is called the myelin sheath
  • Form branches in axon terminal called telodendria
  • it consists of collateral branches found at points of discontinuity in nodes of Ranvier
  • Undergo axonal transport which is the movement of substances along the length of axon
• Anterograde - a type of axonal transport and the movement of substance is from cell body towards the axon (most common axonal transport)
• Retrograde - another type of axonal transport and the movement of substance is from axon towards the cell body