Neuroscience and Behavior

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Neuroscience and Behavior
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Types of Neurons
Types of Neurons
Sensory
Motor
Interneurons
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Sensory Neurons

• INPUT From sensory organs to the brain and
  spinal cord

Brain
Sensory Neuron
Drawing shows a sensory neuron
Spinal Cord
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Motor Neurons

• OUTPUT From the brain and spinal cord, to the
  muscles and glands

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Interneurons

• Interneurons carry information between other
  neurons only found in the brain and spinal cord

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Parts of a Neuron
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The Cell Body
Contains the cells nucleus

• round, centrally located structure
• contains DNA
• controls protein manufacturing
• directs metabolism
• no role in neural signaling

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Dendrites

• Information collectors
• Receive inputs from neighboring neurons
• Inputs may number in thousands
• If enough inputs, the cells AXON may generate an
  output

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Axon

• The cells output structure
• One axon per cell, 2 distinct parts
• tube-like structure
• branches at end that connect to dendrites of
  other cells

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Myelin Sheath

• White fatty casing on axon
• Acts as an electrical insulator
• Not present on all cells
• When present, increases the speed of neural
  signals down the axon

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How Neurons Communicate

• Neurons communicate by means of an electrical
  signal called the Action Potential
• Action Potentials are based on movements of ions
  between the outside and inside of the cell
• When an Action Potential occurs, a molecular
  message is sent to neighboring neurons

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All or None Law

• This is the principle that a neuron is either
  sufficiently stimulated and an action potential
  occurs or the neuron is not sufficiently
  stimulated and the action potential does not
  occur.
• In other words, the neuron cant fire just a
  little bit--it either sends a message or it
  doesnt

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Action Potential Within a Neuron
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Resting Potential

• At rest, the inside of the cell is at -70
  microvolts
• With inputs to dendrites, the inside becomes more
  positive
• If resting potential rises above the sensory
  threshold, an action potential starts to travel
  from cell body down the axon
• Figure shows resting axon being approached by an
  action potential

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Repolarization follows

• After the action potential passes, the inside of
  the axon returns to a negative voltage
• This is called repolarization

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Neuron to Neuron

• Axons branch out and end near dendrites of
  neighboring cells
• Axon terminals are the tips of the axons
  branches
• A gap separates the axon terminals from dendrites
• Gap is called the synapse or synaptic gap

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Neurotransmitter Release

• Action Potential causes vesicle to open

• Neurotransmitter released into synapse

• Locks onto receptor molecule in postsynaptic
  membrane
• Reuptake occurs when, after sending a message,
  the neurotransmitters are taken back into the
  presynaptic neuron

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Excitatory and Inhibitory Messages

• Excitatory messageincreases the likelihood that
  the postsynaptic neuron will activate
• Inhibitory messagedecreases the likelihood that
  the postsynaptic neuron will activate

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Locks and Keys

• Neurotransmitter molecules have specific shapes

• Receptor molecules have binding sites

• When NT binds to receptor, ions enter

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Types of Neurotransmitters

• Acetylcholine
• Serotonin
• Norepinephrine
• Dopamine
• Endorphins
• GABA

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Acetylcholine (Ach)

• Found in neuromuscular junctions
• Involved in muscle movements
• Involved in learning and memory

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Disruption of Acetylcholine Functioning

• Curareblocks ACh receptors
• paralysis results
• Nerve gases and Black Widow spider venom too
  much ACh leads to severe muscle spasms and
  possible death

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Disruptions in ACh Functioning

• Cigarettesnicotine works on ACh receptors
• can artificially stimulate skeletal muscles,
  leading to slight trembling movements

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Alzheimers Disease

• Deterioration of memory, reasoning, and language
  skills
• Symptoms may be due to loss of ACh neurons

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Serotonin

• Involved in sleep
• Involved in depression
• Prozac works by keeping serotonin in the synapse
  longer, giving it more time to exert an effect

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Norepinephrine

• Arousal
• Fight or flight response
• Depression and stress

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Dopamine

• Involved in movement, attention, and learning
• Dopamine imbalance also involved in schizophrenia
  
• Loss of dopamine-producing neurons is cause of
  Parkinsons disease

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Parkinsons Disease

• Results from loss of dopamine-producing neurons
  in the substantia nigra
• Symptoms include
• difficulty starting and stopping voluntary
  movements
• tremors at rest
• stooped posture
• rigidity
• poor balance

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Parkinsons Disease

• Treatments
• L-dopa
• transplants of fetal dopamine-producing
  substantia nigra cells
• adrenal gland transplants
• electrical stimulation of the thalamus has been
  used to stop tremors

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Endorphins

• Control pain and pleasure
• Released in response to pain
• Morphine and codeine work on endorphin receptors
  involved in healing effects of acupuncture
• Runners high feeling of pleasure after a long
  run is due to heavy endorphin release

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GABA

• Inhibition of brain activity
• Implicated in anxiety disorders
• Huntingtons disease involves loss of neurons in
  striatum that utilize GABA
• Symptoms
• jerky involuntary movements
• mental deterioration

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Summary

• Neuron structure
• Action potentials
• Synapse
• Neurotransmitters
• Receptors and ions

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Parts of the Nervous System

• Central Nervous System (CNS)
• Brain and spinal cord
• Peripheral Nervous System (PNS)
• Carries messages to and from CNS

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Sympathetic and parasympathetic divisions of the
nervous system
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Endocrine System

• Pituitary glandattached to the base of the
  brain hormones affect the function of other
  glands
• Adrenal glandshormones involved in human stress
  response
• Gonadshormones regulate sexual characteristics
  and reproductive processes--testes in males,
  ovaries in females

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Brain

• Developing Brain
• Brainstem
• Hindbrain
• Midbrain
• Forebrain
• Limbic system
• Cortex

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Developing Brain

• Neural tubebeginning of nervous system develops
  at 2 weeks after conception
• Neurogenesisdevelopment of new neurons

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Hindbrain

• cerebellum
• medulla
• reticular formation
• pons

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Cerebellum

• Coordinated, rapid voluntary movements
• e.g., playing the piano, kicking, throwing, etc.
• Lesions to cerebellum
• jerky, exaggerated movements
• difficulty walking
• loss of balance
• shaking hands

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Medulla

• Breathing
• Heart rate
• Digestion
• Other vital reflexes
• swallowing
• coughing
• vomiting
• sneezing

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Reticular Formation

• Network of neurons in the brainstem (and
  thalamus)
• Sleep and arousal
• Attention

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Pons

• Helps coordinate movements on left and right
  sides of the body
• e.g., postural reflexes which help you maintain
  balance while standing or moving

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Midbrain

• Smallest region of the brain
• Involved in processing auditory and visual
  sensory signals
• Contains the substantia nigra where there is a
  large concentration of dopamine producing neurons
• Implicated in movement disorders such as
  Parkinsons disease

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Forebrain Structures

• Cortex
• Limbic System

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Lobes of the Cortex

• Frontal lobelargest lobe, produces voluntary
  muscle movements, involved in thinking, planning,
  emotional control
• Temporal lobeprimary receiving area for auditory
  information
• Occipital lobeprimary receiving area for visual
  information
• Parietal lobeprocesses somatic information

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The Limbic System

• Thalamus
• Hypothalamus
• Amygdala
• Hippocampus

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Thalamus

• Relay station in brain
• Processes most information to and from higher
  brain centers

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Hypothalamus

• Contains nuclei involved in a variety of
  behaviors
• sexual behavior
• hunger, thirst
• sleep
• water and salt balance
• body temperature regulation
• circadian rhythms
• role in hormone secretion

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Hypothalamus and Hormones

• Hypothalamus releases hormones or releasing
  factors which in turn cause pituitary gland to
  release its hormones

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Amygdala and Emotion

• Identify emotion from facial expressions

Amygdala damage makes this task difficult
(click on picture to advance photos)
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Hippocampus

• Large sea-horse shaped structure imbedded in
  the temporal lobes
• Plays a role in the formation of new memories

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Cortical Specialization

• Localizationnotion that different functions are
  located in different areas of the brain
• Lateralizationnotion that different functions
  are processed primarily on one side of the brain
  or the other

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Language and the Brain

• Aphasiapartial or complete inability to
  articulate ideas or understand language because
  of brain injury or damage
• Brocas areaplays role in speech production
• Wernikes areaplays role in plays in
  understanding and meaningful speech

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Split brain operationprocedure used to reduces
recurrent seizures of severe epilepsy Corpus
callosumthick band of axons that connects the
two cerebral hemispheres
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