unit 4: the nervous system

• the three major functions of the nervous system are:

  • receive sensory input
  • integration of output
  • motor output
• the nervous system receives sensory input by

  • gather info by monitoring stimuli from inside + outside the body
• the nervous system conducts integration of the input by

  • processing and interpreting sensory input to determine a response
• the nervous system conducts motor output by

  • carrying out response usually via muscle movement or secretion from glands
  • effector = the gland, muscle, or organ that changes in repsonse to the nervous system
• cells in the nervous system can be classified into two categories

  • neurons, which use electricity to transmit information across the cell for FAST communication --> main job of the nervous system
  • neuroglia or glial cells which support, repair, and protect neurons
• the three types of neurons can be classified into

  • sensory neurons
  • motor neurons
  • interneuron
• a sensory neuron detects changes and sends the info to the spine or brain
• a motor neuron sends signals from the spine or brain to the effector organ or muscle
• an interneuron passes info between other neurons and can further process or store information
• interneuron info

  • most stay within the brain or spine
  • connect sensory and motor neurons
  • can communicate w other interneurons
• information processing

  A) sensory input

  B) interneuron

  C) motor output

  
• nerve: bundles of sensory neurons and/or motor neurons that connect between similar parts of the body
• neurons are thin, so grouping together within connective tissue protects them from damage outside the spine + brain
• the two major parts of the nervous system are:

  • central nervous system (CNS) containing the brain and spinal cord
  • peripheral nervous system (PNS) includes all nerves outside of the CNS and connects the CNS to the rest of the body
• two subdivisions of the PNS

  • sensory (afferent) pathway: info going towards CNS
  • motor (efferent) pathway: impulses exit from CNS
• two subdivisions of motor pathway

  • somatic nervous system (SNS) describes a conscious control of skeletal muscles
  • autonomic nervous system (ANS) describes involuntary control of smooth/cardiac muscles + glands
• autonomic system divides into two parts

  • parasympathetic which describes actions actions related to resting, digestion and reproduction
  • sympathetic which stimulates "fight or flight" activities
• soma: cell body
• nucleus: metabolic center of the cell
• dendrites: 1+ more extensions of a nerve cell where impulses are received
• axon hillock: conducts impulses toward cell body / where the cell branches out to the axon
• axon: process that conducts nerve impulses away from the cell body
• myelin: a whitish, fatty substance found on long axons in the CNS which increases the speed of electrical impulses
• schwann cells: myelinated axons in the PNS
• axon terminal: branched end of an axon where neurtransmitters are stored in vesicles
• modes of ranvier: gaps between schwann cells
• label some essential parts

  A) cell body

  B) axon hillock

  C) axon

  D) nucleus

  E) axon terminal

  F) dendrite

  G) schwann cells

  H) nodes of ranvier

  
• large connections of cell bodies in the CNS are in clusters called nuclei
• small concentrations are called ganglia/ganglion found in the CNS and PNS
• myelinated nerve fibers/tracts in the CNS are called white matter
• unmyelinated fibers and cell bodies are called gray matter
• the three different types of neurons are

  • sensory (afferent) neurons
  • motor (efferent) neurons
  • association neurons / interneurons
• sensory neurons carry impulses from sensory receptors toward the CNS

  • nerve endings are pain and temperature receptors
  • meissner's corpuscle is a touch receptor
  • pacinian corpuscle is a deep touch receptor
  • proprioceptors receive info and cause stretch or tension in muscles
• motor (efferent) neurons

  • carry impulses from CNS to organs and muscles
• interneurons connect motor and sensory neurons
• label the reflex arc

  A) spine

  B) effector

  C) receptor region

  D) efferent neuron

  E) afferent neuron

  F) interneuron

  
• the three classifications of neurons are

  • unipolar
  • bipolar
  • multipolar
• a unipolar process describes a short, singular extension from the cell body
• a bipolar process describes a single axon and dendrite, very rare and only in sensory organs that acts as a receptor for cells
• a multipolar process describes several processes that extend from the cell body to the axon terminals, most common bc all motor neurons are multipolar