Chapter 49 Nervous Systems

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Chapter 49Nervous Systems

• Barbara Musolf
• Clayton State University
• AS Administration Building A 16-C
• 678-466-4851

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Objectives

• The organization of animals nervous systems
• The mechanism by which neurons transmit
  information
• Graded potentials
• Action potentials
• Neural circuits
• The specialization of function for different
  regions of vertebrate nervous system
• The role of the cerebral cortex

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Sensing and responding

• First types of sensing were in prokaryotes that
  detected changes in their environment through
  chemical senses.
• Chemotaxis helped to detect food
• Multicellular organisms had to communicated
  between cells
• The Cambrian explosion (500 mya) saw systems of
  neurons that included collection of sensory
  information to produce motor movement or some
  other response.

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Nervous systems are circuits of neurons

• Nerve nets
• Central nervous systems and nerve nets
• Central nervous system (brain and a chain of
  ganglia) and a peripheral nervous system
• Central nervous system (brain and spinal cord)
  and a peripheral nervous system

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Organization of nervous systems
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Information processing
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Neuronal structure
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The patellar reflexstretch reflex
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The patellar reflexstretch reflex

• A pull on the patellar ligament causes muscle to
  stretch
• Sensory information travels to spinal cord
• Sensory neuron contacts motor neuron and an
  interneuronintegration of neural information
• Motor neuron stimulates a contraction of the
  quadriceps muscle
• Interneuron inhibits motor neuron that stimulates
  hamstring muscle and hamstring relaxes.

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Glial cells

• Provide structural support
• Regulate ion and neurotransmitter concentrations.
• Regulate blood flow increasing flow to active
  neurons
• Helps form the blood-brain barrier.

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Glial cells
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Organization of vertebrate nervous system

• CNS
• Brain
• Spinal cord
• PNS
• Cranial and spinal nerves
• Ganglia

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Gray and white matter
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The PNS
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Autonomic nervous system
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Brain the brainstem

• Medulla oblongata regulates breathing, heart rate
  and blood vessels, swallowing, vomiting
• Decussation of the pyramids
• Pons regulates breathing centers in the medulla
• Midbrain receives sensory information on vision
  (superior colliculi) and hearing (inferior
  colliculi), integrates it and transmits it to
  forebrain regions.

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Reticular activating system

• RAS is made up of a diffuse network of neurons in
  the brainstem
• Controls arousal and acts as a filter for
  information going to cerebrum
• Midbrain may control arousal
• Medulla and pons may control sleep

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Cerebellum

• Functions in coordination
• Error checks movements during motor, perceptual
  and cognitive functions
• Involved in the learning and memory used in motor
  skills such as riding a bicycle.
• Involved in hand-eye coordination
• Involved in language processing

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Diencephalon

• Epithalamus includes the pineal gland, which is
  involved in sleep/wake cycles
• Thalamus is a major sensory relay center between
  incoming sensory signals and the cerebrum.
• Thalamus receives information from brain areas
  that regulate emotion and arousal
• Hypothalamus is involved in homeostatic functions
  through its control of endocrine systems.
• Regulates thirst, hunger, temperature, circadian
  rhythms, mating

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Cerebrum

• Basal nuclei are groups of neurons that function
  in the initiation and planning of motor movement.
• Limbic system plays a role in emotionpain,
  pleasure, fear, docility, affection and anger.
• The hippocampus functions in memory formation.
• Neocortex is the folded region of the brain made
  up of six layers of neurons.
• Folding increases the surface area of the brain.