Neurons

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Neurons the Nervous System

• Chapter 2 The Brain and Behavior

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Todays Goal ? You will be able to.

• Identify the parts of a neuron and their
  functions in creating sending neural messages.

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Parts of the Neuron

• Neurons nerve cells
• Dendrites branch-like end of neuron which
  receives messages
• Cell body (soma) contains nucleus
• Axon long tail-like end of neuron which
  transmits (sends) messages

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• Myelin fatty substance that speeds up
  transmission of impulse
• Axon terminals/Terminal buttons contain
  neurotransmitters, release them during neural
  impulse
• Terminal buttons (axon terminal) bulb-shaped
  structure at end of axon

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Types of Neurons

• Sensory neurons send messages from sensory
  receptors to the spinal cord brain
• Motor neurons relay messages from brain spinal
  cord to muscles glands
• Interneurons transmits neural stimulus between
  sensory motor neurons (found only in Central
  nervous system)

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Simple Reflex Arc

• Communication goes directly from interneurons in
  spinal cord to motor neurons to move
  (reflexively) at the same time the info is going
  to the brain to be perceived

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Central v. Peripheral

• Central contains brain spinal cord
• Peripheral sensory motor neurons that
  transmit messages between brain and muscles
  glands

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Autonomic v. Somatic

• Somatic voluntary - controls purposeful body
  movements
• Autonomic involuntary automatic activities
• heartbeat, respiration, digestion, dilation of
  pupils, etc.

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Sympathetic v. Parasympathetic

• Sympathetic Fight-or-flight response
• Uses energy reserves to cope with stress or
  emergency
• Adrenaline!
• Parasympathetic Rest and digest
• Conserves builds up stored energy reserves

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Todays Goal ? You will be able to.

• Describe how neurons communicate to send messages
  in the brain and body

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The Synapse

• Synapse (synaptic cleft) gap between dendrites
  of one neuron and axon of another
• Receptor sites parts of dendrite which receive
  neurotransmitters
• Neurotransmitters chemical substances involved
  in sending neural impulses

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Neural Impulse electrochemical firing of a nerve
cell

• Resting potential electric potential when neuron
  not firing (-70 millivolts)
• Threshold level of stimulation required to
  trigger a neural impulse (excitatory inhibitory
  threshold)

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Neural Impulse electrochemical firing of a nerve
cell

• Action potential when a neuron fires the impulse
  (sends the message)
• Refractory period phase after firing an impulse,
  neuron will not fire
• All-or-none principle neuron will fire or not
  fire, no in-between

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Resting potential
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Synapses

• Excitatory neurotransmission increases the
  likelihood that postsynaptic neuron will fire
• Inhibitory neurotransmission decreases
  likelihood that postsynaptic neuron will fire

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Todays Goal ? You will be able to

• Discuss how the major neurotransmitters affect
  the body and ones behavior

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Substances that Affect Neurotransmitters

• Agonist similar to the NT, mimics its effects
• Antagonist inhibits the release of NT by sending
  neuron, or blocks receptor site for NT on
  receiving neuron

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Neurotransmitters

• Acetylcholine (ACh)
• EXCITATORY (sometimes inhibitory)
• Memory, muscle contractions, learning
• Malfunctions Alzheimers Disease

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Neurotransmitters

• Dopamine (DA)
• Reward/pleasure, movement, attention
• Malfunctions Too little ? Parkinsons, Too much
  ? Schizophrenia
• Serotonin
• Mood regulation, sleep and appetite regulation,
  concentration, learning
• Imbalance ? depression

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Neurotransmitters

• Norepinephrine
• Involved in autonomic nervous system
  (sympathetic) arousal
• Imbalances Depression, seizures
• GABA
• Function Reduce anxiety, relax for sleep
• Imbalance Anxiety disorders, tremors, insomnia
• Endorphins ? pain control