Functional Organization of Nervous Tissue Chapter 11

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Functional Organization of Nervous
TissueChapter 11
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The Nervous System

• Components
• Brain, spinal cord, nerves, sensory receptors
• Responsible for
• Sensory perceptions, mental activities,
  stimulating muscle movements, secretions of many
  glands
• Subdivisions
• Central Nervous System (CNS)
• Peripheral Nervous System (PNS)

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Central Nervous System

• Consists of brain and spinal cord
• The structural functional center of the entire
  nervous system which integrates incoming pieces
  of information initiates an outgoing response

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Peripheral Nervous System

• All other nerves
• All pathways going toward and away from the CNS

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Nervous System Organization
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Concept Check

• What are the two divisions of the nervous system?
  What are their parts?
• CNS Brain Spinal Cord
• PNS nerves
• What are the functions of the CNS?
• Integrates incoming information initiates an
  outgoing response
• What is the function of the PNS?
• Conducts action potentials to and away from the
  CNS
• What are some functions of the Nervous system?
• Sensory perceptions, mental activities,
  stimulating muscle movement, secretions of many
  glands

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Cells of Nervous System

• Neurons or nerve cells
• Receive stimuli and transmit action potentials
• Organization
• Cell body or soma
• Dendrites input
• Axons output
• Neuroglia cells
• Support and protect neurons

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Types of Neurons

• Functional Classification
• Sensory or afferent action potentials toward CNS
  (receives stimuli could be a special sense
  organ)
• Motor or efferent action potentials away from
  CNS (attached to a muscle or gland)
• Interneurons or association neurons within CNS
  from one neuron to another

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Myelinated and Unmyelinated Axons

• Myelinated axons
• Myelin protects and insulates axons from one
  another
• Not continuous
• Nodes of Ranvier
• Impulse jumps from node to node
• Fast impulse
• Unmyelinated axons
• Slower impulse

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Electrical Signals

• Cells produce electrical signals called action
  potentials
• Transfer of information from one part of body to
  another
• Electrical properties result from ionic
  concentration differences across plasma membrane
  and permeability

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Nerve Impulses

• A wave of electrical fluctuation that travels
  along the plasma membrane due to changes in
  chemical concentrations.

Impulse
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Resting Potential Polarized
Action Potential Depolarized
Resting Potential Repolarized
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Resting Membrane Potential

• Characteristics
• Number of charged molecules and ions inside and
  outside cell nearly equal
• Concentration of K higher inside than outside
  cell- negative proteins in also, Na higher
  outside than inside
• At equilibrium there is very little movement of
  K or other ions across plasma membrane

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Action Potentials

• Series of permeability changes when a local
  potential causes depolarization of membrane
• Phases
• Depolarization
• More positive
• Repolarization
• More negative
• All-or-none principle
• Neuron will fire or it wont

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The Synapse

• Junction between two cells
• Electrical message transferred across the synapse
  by chemicals called neurotransmitters

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Concept Check

• What are the main parts of a neuron?
• Axon, dendrites, myelin sheath, synapse
• What are the three types of neurons and what do
  they do?
• Sensory (afferent)- action potential toward CNS ,
  Motor (efferent)- action potential away from CNS,
  Interneurons- within CNS from one neuron to
  another
• How does an impulse travel along an axon? What
  speeds it up?
• Jumps from node to node myelin
• How does a synapse work?
• Neurotransmitters transfer message across synapse

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Stimulus

• Any change in your environment.
• Temp, sound, smell
• You may or may not respond to a specific stimulus

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Reflex

• A predictable response to a stimulus which may or
  may not be conscious
• A reflex consists of either muscle contraction or
  glandular secretion
• Neurons involved in reflex
• Afferent neuron- sensory
• Interneuron
• Efferent neuron- motor

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Sensory Receptors

• In order for a stimulus to be detected, it must
  be strong enough to elicit an impulse
• It must be at the threshold level- the minimum
  stimulus to start an impulse
• The all-or-none response means that either a
  neuron will fire or it wont, there is no partial
  impulse
• Sensation- the brains interpretation of what the
  stimulus is

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Characteristics of Sensations

• Projection- brain refers a sensation to the point
  of stimulation
• Adaptation- loss of sensation even though the
  stimulus is still applied
• Afterimage- persistence of a sensation even
  though the stimulus is removed
• Referred pain- felt in the skin near or around
  the organ sending the impulse
• Phantom pain- sensation of pain in a limb that
  has been amputated

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Classification of Receptors

1. Mechanoreceptors- activated by mechanical stimuli
   or deformation of the receptor
2. Chemoreceptor- changing of the chemical
   concentrations around the body
3. Thermoreceptors- detect hot and cold
4. Nociceptors- any stimuli that can cause tissue
   damage sensation of pain
5. Photoreceptors- respond to light

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Somatic Sensespain, temperature and touch

• These sensations can be felt throughout the body,
  yet they are distributed unevenly through the
  skin
• Exteroceptors- sense receptors located on body
  surfaces
• Proprioceptors- found in the muscles and joints
• Visceroceptors- found in internal organs
• Nociceptors- pain receptors free nerve endings

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Review

• Meissners corpuscles- touch
• Krauses End Bulbs- touch
• Ruffinis corpuscles- continuous touch
• Pacinian corpuscles- deep pressure

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The Brain

• Parts/Functions
• Left vs Right Brain Activity??
• Dissection notespre-lab??