C11 - Nervous System & Nervous Tissue Pt.1

Define Nervous System

The master controlling and communicating system of body

How do cells communicate?

• Via electrical and chemical signals

  1. Rapid and specific

  2. Usually cause almost immediate responses

List and explain the basic functions of the nervous system

1. Sensory input

   • information gathered by sensory receptors about internal and external changes

2. Integration

   • Processing and interpretation of sensory input

3. Motor output

   • Activation of effector organs (muscles and glands) produces a response

Explain the structural and functional divisions of the nervous system

1. Central Nervous System (CNS)

   • Brain and spinal cord of dorsal body cavity

   • Integration and control center

   • Interprets sensory input and dictates motor output

2. Peripheral Nervous System (PNS)

   • The portion of nervous system outside CNS

   • Consists mainly of nerves that extend from brain and spinal cord

     • Spinal nerves to and from spinal cord

     • Cranial nerves to and from brain

Explain the functional sub-divisions of the PNS

1. Sensory (afferent) division

   • Somatic sensory fibers → convey impulses from skin, skeletal muscles, and joints to CNS

   • Visceral sensory fibers → convey impulses from visceral organs to CNS

2. Motor (efferent) division

   • Transmits impulses from CNS to effector organs

     1. Muscles

     2. Glands

   • Two divisions

     1. Somatic nervous system

     2. Autonomic nervous system

Explain the functional sub-sub-divisions of the Motor (Efferent) Division

1. Somatic Nervous System

   • Somatic motor nerve fibers conduct impulses from CNS to skeletal muscle

   • Voluntary nervous system → conscious control of skeletal muscles

2. Autonomic Nervous System

   • Consists of visceral motor nerve fibers

   • Regulates smooth muscle, cardiac muscle, and glands

   • Involuntary nervous system

   • Two functional subdivisions

     1. Sympathetic

     2. Parasympathetic

Explain the functional sub-sub-sub-divisions of the Autonomic Nervous System

1. Sympathetic

   • Puts tour body’s systems on alert

2. Parasympathetic

   • Carries signals that relax those systems

Overview of Structural and Functional Divisions of the Nervous System

List and define the two principal cell types in Nervous Tissue

1. Neuroglia (glial cells)

   • Small cells that surround and wrap delicate neurons

2. Neurons (nerve cells)

   • Excitable cells that transmit electrical signal

List the types of neuroglia and their functions

1. Astrocytes

2. Microglial cells

3. Ependymal cells

4. Oligodendrocytes

Explain the function of Astrocytes

Neuroglia (glial cells)

• STRUCTURE

  • Most abundant, versatile, and highly branched of glial cells

  • Cling to neurons, synaptic endings, and capillaries

• FUNCTION

  1. Support and brace neurons

  2. Play role in exchanges between capillaries and neurons

  3. Participate in information processing in brain

Explain the function of Microglial cells

Neuroglia (glial cells)

• STRUCTURE

  • Small, ovoid cells with thorny processes that touch and monitor neurons

  • Migrate toward injured neurons

• FUNCTION

  1. Can transform to phagocytize microorganism and neuronal debris

Explain the function of Ependymal cells

Neuroglia (glial cells)

• STRUCTURE

  • Range in shape from squamous to columnar

  • Line the central cavities of the brain and spinal column

  • May be ciliated → cilia beat to circulate CSF

• FUNCTION

  1. Produce cerebrospinal fluids (CSF)

  2. Form permeable barrier between CSF in cavities and tissue fluid bathing CNS cells

Explain the function of Oligodendrocytes

Neuroglia (glial cells)

• STRUCTURE

  • Branched cells

• FUNCTION

  1. Processes wrap CNS nerve fibers, forming insulating myelin sheaths in thicker nerve fibers

Define Neuron

• aka Nerve cell→ Structural units of nervous system

• Large, highly specialized cells that conducts impulses

• All have cell body and one or more processes

List the special characteristics of Neurons

1. Extreme longevity (lasts a person’s lifetime)

2. Amitotic, with few exceptions

3. High metabolic rate → requires continuous supply of oxygen and glucose

Describe Neurons important structural components, and relate each to a functional role

1. Cell body (soma)

   • Biosynthetic center of a neuron

2. Dendrites (Neuron process)

   • Branching neuron process that serves as a receptive, or input region

   • Transmits an electrical signal TOWARD the cell body

3. Axon (Neuron process)

   • Carries action potentials AWAY fro the neuron cell body

   • Efferent process

   • The conduction portion of a neuron

Explain the structure and function of Neuron Cell Body

aka Perikaryon or Soma

• STRUCTURE

  • Contains spherical nucleus with nucleolus

  • Some contain pigments

• FUNCTION

  • Biosynthetic center of neuron

    • Synthesizes proteins, membranes, chemicals

    • Rough ER (chromatophliic substances, or Nissi bodies)

Differentiate between a nucleus and ganglion and nerve and a tract 

Explain the importance of the myelin sheath and describe how it is formed in the peripheral and central nervous systems

Classify neurons by structure and by function