Human Nervous System Quiz

The Nervous System

• The nervous system is widely distributed in the body and involves most organs.
• It collects stimuli from the environment, transforms them into nerve impulses, and passes them to a large, highly organized reception and correlation area where they are interpreted.

Functions of the Nervous System

• Three principal functions: sensory input, integration, and motor output.
• All actions, thoughts, and emotions can be boiled down into these three functions.

Sensory Input

• Special senses:
  • Eyes: sight
  • Nose: smell
  • Tongue: taste
  • Ear: hearing
  • Skin: touch
• Nociception: pain receptor
• Temperature
• Stretch receptor (bladder)

Integration

• The nervous system processes sensory input and decides what to do about it.
• "Fight or flight" response.

Motor Output

• The response that occurs when the nervous system activates certain parts of the body.

Types of Nervous System

• Two main categories:
  • Central Nervous System (CNS): brain and spinal cord
  • Peripheral Nervous System (PNS): nerves

Divisions of Peripheral Nervous System

• Sensory Division (Afferent): picks up sensory stimuli
• Motor Division (Efferent): sends signals from the CNS to the rest of the body
  • Somatic: voluntary
  • Autonomic: involuntary
    • Sympathetic: fight or flight
    • Parasympathetic: heart beat, peristalsis (movement of intestine muscles)

Cells of the Nervous System

• Two main cells:
  • Neurons: receive stimuli and send signals
  • Glial cells: protect, nourish, insulate, and help neurons send signals

Types of Glial Cells

• Central Nervous System:
  • Astrocytes
  • Microglial cells
  • Ependymal cells
  • Oligodendrocytes
• Peripheral Nervous System:
  • Satellite cells
  • Schwann cells

Glial Cell Functions

• Astrocytes:
  • Most abundant glial cells
  • Anchor neurons to blood supply (capillaries)
  • Allow exchange of ions between neurons and capillaries
• Microglial cells:
  • Provide immune defense against invading microorganisms in the brain and spinal cord
• Ependymal cells:
  • Create, secrete, and circulate Cerebrospinal fluid (CSF)
• Oligodendrocytes:
  • Produce an insulating barrier called myelin sheath
• Satellite cells:
  • Surround and support neuron cell bodies
• Schwann cells:
  • Wrap around axons and produce an insulating barrier called myelin sheath

Neuron Characteristics

• Longest lived cells
• Irreplaceable (amitotic)
• Huge appetite: consume 25% of daily calories

Neuron Structure

• Soma (cell body):
  • Life support
  • Contains organelles (nucleus, mitochondria)
• Dendrites:
  • Pick up signals and convey them to the soma
• Axon:
  • Long extension
  • Transmit electrical impulses away from the cell body to other cells

Types of Neurons

• Based on processes:
  • Multipolar neuron: majority, three or more processes from the soma (axon and several dendrites)
  • Bipolar neuron: two processes from the soma (axon and one dendrite), found in retina of the eye
  • Unipolar neuron: one process, usually seen in sensory receptors
• Based on function:
  • Sensory (afferent) neurons: pick up sensory stimuli and send them towards the CNS
  • Interneurons (association neurons): transmit signals between sensory and motor neurons, live within the CNS
  • Motor (efferent) neurons: send signals from the CNS to the rest of the body (muscles or glands), mostly multipolar