The Nervous System Coordination, Integration, Control

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The Nervous SystemCoordination, Integration,
Control
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Key Concepts and Important Terms

• Nervous systems function in sensory input,
  integration, and motor output.
• The nervous system is composed of neurons and
  supporting cells.
• Membrane potentials arise from differences in ion
  concentrations between a cells contents and the
  extracellular fluid.
• An action potential is an all-or-none change in
  the membrane potential.
• Action potentials travel along an axon because
  they are self-propagating.
• Chemical or electrical communication between
  cells occurs at synapses.
• One neurotransmitter can produce different
  effects on different types of cells.
• The symmetry of the nervous system is correlated
  with body symmetry.
• Vertebrate nervous systems are highly centralized
  and cephalized.
• The vertebrate peripheral nervous system has
  several components differing in organization and
  function.
• The brainstem conducts data and controls
  automatic activities essential for survival.
• The cerebellum controls movement and balance.
• The thalamus and hypothalamus are prominent
  integrating centers of the forebrain.
• The cerebrum contains the most sophisticated
  integrating centers.

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QUIZ 1

• A. Enumeration.
• 1-2. Two types of cells in the nervous system.
• 3-5. Three types of nerve cells involved in a
  reflex arc.
• 6-7. Two trends in the evolution of the NS in
  animals.
• 8-9. Two trends in the evolution of the brain in
  vertebrates.
• B. Whats the difference?
• 10. axon vs. dendrite
• 11. depolarization vs. repolarization
• 12. saltatory conduction vs. conduction in an
  unmyelinated axon
• 13. brain vs. ganglion
• 14. transmission via gap junction vs.
  transmission via synapse
• 15. autonomic vs. somatic nervous system

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Functions of Nervous Systems
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Cells of the Nervous System

• Neurons
• Functional unit of the NS
• Transmit signals from one location to another
• Structure
• Large cell body
• Processes that conduct signals
• Dendrites
• Axons

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• 2. Glia
• Supporting cells
• Protect neurons
• Insulate neurons
• Provide structure
• Ex astrocytes, microglia, ependymal cells,
  oligodendrocytes, satellite and Schwann cells

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The Dendrite Song!

• Axons send outNeurotransmittersTo the dendrites
  all aroundAcross the synapseJumps the
  impulseNew ideas can now abound.
• StimulationIs what the brain needsTo make
  dendrites stretch and grow. New connectionsMake
  us smarterIn what we think and what we know.
• Use your dendrites,Use your dendrites,To
  connect throughout your brainTake in info,
  analyze it,Grow some new onesUnrestrained.

• (sung to the tune of "Clementine" sent in by Leah
  B., a graduate student in elementary education at
  Long Island Univ. Leah gives credit to Bruce
  Campbell for composing this song.)
• Use your dendrites,Use your dendrites,To
  connect throughout your brain.Take in info,
  analyze it,Grow some new onesUnrestrained.

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How are neurons organized?

• Three types of neurons
• Sensory neurons
• Interneurons
• Motor neurons
• Neural circuits form from any combination of two
  or more of these
• Convergent (many to one)
• Divergent (one to many)
• Reverberating (circular)
• Simplest Sensory and motor neurons reflex arc

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Electrical conduction of information

• Membrane potential
• Difference of charges across the plasma membrane
• Resting potential
• Resting cells are (-) inside and () outside
• Large amounts of Na outside the cell and K
  inside
• Action potential/impulse
• Rapid reversals in charges across the plasma
  membrane
• Caused by the exchange of ions across the
  membrane of the neuron
• Threshold level (-55mV) needed to stimulate
  neurons ALL-OR-NONE principle

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Saltatory conduction a faster way

• Depends on myelin sheaths coating an axon
• Impulses carried from node to node
• Advantages
• Saves on ATP/energy
• Increases the speed of conduction
• Multiple sclerosis demyelination of axons in the
  CNS

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Gap junctions and neurotransmittersCommunication
between neurons

• Gap junctions form continuous passages between
  some neurons
• Neurotransmitters cross the synapse to relay the
  impulse to another neuron or an effector

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stress hormone
sympathetic NS
mood, sexuality, metabolism
learning and memory
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Diversity of nervous systems

• Nerve cord thick bundle of nerves from the
  brain
• Ganglion mass of neurons in the PNS

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Vertebrate nervous systems

• Evolutionary trends
• Increase in overall brain size
• Compartmentalization of functions
• Increased development of the forebrain

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Vertebrate CNS

• Cephalized
• Centralized
• Integration and processing of information
• White matter axons in the CNS
• Gray matter cell bodies, dendrites,
  unmyelinated axons
• Central canal of the spinal cord
• Ventricles of the brain
• Cerebrospinal fluid (CSF)
• Meninges protective connective tissue

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Vertebrate PNS

• Transmits information to and from the CNS
• Components
• Both sensory and motor functions
• Paired cranial nerves (12)
• Paired spinal nerves (31)
• Ganglia
• Motor division
• Somatic nervous system
• Voluntary - signals to and from skeletal muscles
• Respond to external stimuli
• Autonomic nervous system
• Involuntary - Internal environment, smooth and
  cardiac muscles
• Sympathetic and parasympathetic divisions

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Actions of the parasympathetic and sympathetic
divisions of the ANS

• Sympathetic division
• Stimulation
• Energy generation
• Parasympathetic division
• Calming
• Rest and repair
• Often have antagonistic actions
• Cooperate to maintain homeostasis

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Structure and function of the vertebrate brain
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Integrating centers in the cerebrum

• Right and left cerebral hemispheres
• Cerebral cortex
• Highly developed and convoluted in mammals
• Lobes with sensory areas and association areas,
  frontal lobe with motor cortex
• Basal nuclei planning and learning movement
  sequences

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Other roles of the cerebral cortex

• Language and speech
• Brocas area
• Wernickes area
• Emotions
• Limbic system amygdala, hippocampus, and
  olfactory bulb
• Laughing, crying, aggression, feeding, and
  sexuality
• Memory and learning
• Short-term frontal lobe
• Long-term amygdala and hippocampus
• Neurons may make new connections
• Consciousness
• Emergent property based on activity in many areas
  of the cortex

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Drugs and the Nervous System
Drug Effect on the NS Effect on the Body
Alcohol (ethanol) CNS depressant Depends on dosage, FAS in babies
Stimulants Amphetamines Cocaine Caffeine Nicotine CNS and Sym division stimulant, more dopamine / adenosine/ norepinephrine / serotonin in the synapse Feelings of happiness and power, reduced fatigue, insomnia, psychosis, hallucinations, violent and aggressive behavior, tremors
Depressants Barbiturates CNS depressant, action potentials cannot be produced Reduce respiration, bp, heart rate, anesthetic
Opiates Heroin CNS depressant, mimic the effects of endorphins, stimulate pleasure center Analgesia, sedation, reduced respiration,
Hallucinogens /psychedelics Mimic the effects of serotonin Vivid colors, heightened emotions, increase in heart rate and bp
Marijuana Acts on cannabinoid receptors in the brain Altered sense of time and space, hallucinations
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