Biological Perspective

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Biological Perspective

• Chapter 2

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Nervous System
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Structure of a Neuron

• Neurons - basic nervous system cell receives and
  sends messages within that system.
• Parts of a Neuron
• Dendrites - branch-like structures that receive
  messages from other neurons.
• Soma - cell body of the neuron.
• Axon - long tube-like structure that carries the
  neural message to other cells.

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Other types of Brain Cells

• Glial cells - grey fatty cells that
• provide support for neurons to grow on around,
• deliver nutrients to neurons,
• produce myelin to coat axons,
• Myelin - fatty substances that coat the axons of
  neurons to insulate, protect, and speed up the
  neural impulse.
• clean up waste products and dead neurons

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Neural Impulses

• A neuron fires an impulse when it receives a
  signal from a sense receptor (stimulated by
  pressure, heat, or light, for example) or from an
  adjacent neuron.
• This impulse is called an action potential. Its
  a brief electrical charge that travels down the
  axon.

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Neural Impulses (contd)

• Neurons generate electricity from chemical
  events.
• These action potentials are generated by the
  movement of positively charged atoms. They move
  in and out of small channels in the axons
  membrane as the signal travels down the axon.
• This is an all-or-nothing responsea neuron
  either fires or doesnt fire.

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Neural Communication

• Where the axon terminal of one neuron meets the
  dendrites of the next neuron is called the
  synapse.
• Neurons dont actually touch one another there
  is a microscopic synaptic gap.

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Neural Communication (contd)

• As the action potential reaches the axons end,
  neurotransmitters (chemical messengers) are
  released from the synaptic knob of an axon.
• These neurotransmitters cross the synaptic gap
  and bind to receptor sites on the dendrites of
  the next neuron.

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Neural Communication (contd)

• Each neurotransmitter has specific receptor sites
  on the receiving neuron, and the neurotransmitter
  fits its site like a key into a lock.
• The neurotransmitter unlocks tiny channels at the
  receiving site, which allows excitatory or
  inhibitory ions to enter the receiving neuron.
• Excess neurotransmitters are reabsorbed into the
  sending neuron, and this is called reuptake.

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Altering Neurotransmission

• Drugs affect communication at the synapse by
  exciting or inhibiting neuron firing.
• Agonists serve an excitatory function by
  mimicking a specific neurotransmitter (thereby
  activating the receiving neuron) or blocking its
  reuptake (causing more of the neurotransmitter to
  be present).
• Antagonists serve an inhibitory function by
  blocking neurotransmitters (thereby preventing
  the receiving neuron from being activated), or
  diminishing their release.

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Neurotransmitters

• Acetylcholineinfluences muscle action, learning,
  and memory vital to muscle movement.
• GABAinhibitory binds to receptor sites affected
  by tranquilizers, alcohol.
• Serotoninsleep, mood, appetite related to
  depression.

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Neurotransmitters (contd)

• Dopaminetoo littleParkionsons too
  muchschizophrenia.
• Endorphinsone kind of neurotransmitter short
  for endogenous morphine, meaning natural opiate
  produced in the body.

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Nervous System
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Central Nervous System

• CNS composed of the brain and the spinal cord.
• Spinal cord - a long bundle of neurons that
  carries messages to and from the body to the
  brain that is responsible for very fast,
  lifesaving reflexes.

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Reflex Arc Three Types of Neurons

• Sensory neuron - carries information from the
  senses to the central nervous system.
• Motor neuron - carries messages from central
  nervous system to muscles of body.
• Interneuron - a neuron found in the center of the
  spinal cord receives information from sensory
  neurons and sends commands to muscles through
  motor neurons.

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Peripheral Nervous System

• Peripheral nervous system (PNS) - all nerves and
  neurons that are not contained in the brain and
  spinal cord but that run through the body itself
  divided into the
• Somatic nervous system
• Autonomic nervous system

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Somatic Nervous System

• Somatic nervous system - consists of nerves that
  carry information from the senses to the CNS and
  from the CNS to the voluntary muscles of the
  body.
• Sensory pathway - nerves coming from the sensory
  organs to the CNS consisting of sensory neurons.
• Motor pathway - nerves coming from the CNS to the
  voluntary muscles, consisting of motor neurons.

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Autonomic Nervous System

• Autonomic nervous system (ANS) - consists of
  nerves that control all of the involuntary
  muscles, organs, and glands.
• Sympathetic division (fight-or-flight system) -
  part of the ANS that is responsible for reacting
  to stressful events and bodily arousal.
• Parasympathetic division - part of the ANS that
  restores the body to normal functioning after
  arousal and is responsible for the day-to-day
  functioning of the organs and glands.

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The Brain

• Recall that the brain is part of the Central
  Nervous System.
• The brain is central to everything that we do
  the mind is what the brain does.
• How do we study the brain?
• Clinical studies
• EEGs
• CT, MRI, and PET scans

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Brain Structures

• As species evolved, newer parts of the brain
  developed over older, more primitive ones.
• What are the most primitive parts of our brain?
• What are the most advanced parts of our brain?

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Lower-Level Brain StructuresThe Brainstem

• Brainstem is the oldest, most basic and central
  part of the brain, responsible for survival
  tasks.
• What happens if you have damage to your
  brainstem?
• Medulla
• Pons
• Reticular Formation
• Cerebellum

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Lower-Level Brain StructuresThe Limbic System

• Limbic system is a system of neural structures
  associated with emotions (fear, aggression), as
  well as the hunger and sexual drive.
• Composed of the thalamus, hypothalamus,
  hippocampus, and amygdala.

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Limbic System (contd)

• Thalamuslies in center of brain what happens if
  damaged?
• Hypothalamuslies below thalamus controls the
  pituitary gland, so what happens if damaged?

• Hippocampuswhat happens when there is damage to
  this area of the limbic system?
• Amygdalaimportant in regulating aggression and
  fear, so what happens if damaged?

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Cerebral Cortex

• Cerebral cortex is the surface layer of the
  brain, mostly interconnected neural cells.
• Cerebral cortex is wrinkled all over the surface,
  which allows for more surface area in the small
  space of our skulls, and thus, more neurons.

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Frontal Lobes

• When are your frontal lobes fully developed?
• What happens if you suffer damage to frontal
  lobes?

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Parietal Lobes

• Where are your parietal lobes?
• What happens with damage to parietal lobes?

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Occipital Lobes

• Where are your occipital lobes?
• What happens with damage to occipital lobes?

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Temporal Lobes

• Where are your temporal lobes?
• What happens with damage to temporal lobes?

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Association Areas

• Aphasia means impairment in use of languagecan
  be impairment in speaking or understanding.
• Brocas areadamage to this area causes what?
  Where is it?
• Wernickes areadamage to this area causes what?
  Where is it?
• Spatial neglectcaused by damage to association
  areas in right hemisphere (will cause left-side
  neglect).

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Splitting the Brain

• The corpus callosum is the band of neural fibers
  that connects the two hemispheres and facilitates
  communication between them.
• What happens if you cut the corpus callosum?

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Endocrine System

• Interconnected with nervous system, and is
  another communication system.
• Glands of the endocrine system secrete hormones,
  which serve as chemical messengers. Hormones
  originate in one tissue, but travel through the
  bloodstream, so they can affect other tissues,
  even brain.

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Endocrine Glands

• Pituitary gland - located in the brain secretes
  human growth hormone and influences all other
  hormone-secreting glands (also known as the
  master gland).
• Pineal gland - located near the base of the
  brain secretes melatonin.
• Thyroid gland - located in the neck regulates
  metabolism.
• Pancreas - endocrine gland that controls the
  levels of sugar in the blood.

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Endocrine Glands (contd)

• Gonads - sex glands secrete hormones that
  regulate sexual development and behavior, as well
  as reproduction.
• Ovaries - the female gonads.
• Testes - the male gonads.
• Adrenal glands - located on top of each kidney
  secrete over 30 different hormones to deal with
  stress, regulate salt intake, and provide a
  secondary source of sex hormones affecting the
  sexual changes that occur during adolescence.