Chap 2 - Biology Perspective

• Neuron


  The basic cell that makes up the nervous system and receives and sends messages within that system
• Neuron


  • Dendrites: branch-like structures that receive messages from other neurons
  • Soma: the cell body / core of the neuron, responsible for maintaining the life of the cell
  • Axon: long, tube-like structure that carries the neural message to other cells
  • Axon terminals: rounded areas at the end of the branches at the end of the axon. Responsible for communicating with other nerve cells
• Myelin


  Fatty substances produced by certain glial cells that coat the axons of neurons to insulate, protect, and speed up the neural impulse
• Resting Potential


  The state neuron when not firing a
• Generating the Message Within the Neuron: The Neural Impulse

  1. Ions: charged particles

  2. Diffusion: the process of ions moving from areas of high concentration to areas of low concentration

  3. Resting potential: the state of the neuron when not firing a neural impulse

  4. Action potential: the release of the neural impulse consisting of a reversal of the electrical charge within the axon

  5. All-or-none: a neuron either fires completely or does not fire at all
• The Neural Impulse Action Potential: Voltage is graphed at a given axonal node over 2 to 3 milliseconds (thousandths of a second). From an initial resting state, enough stimulation is received that the threshold of excitation is reached and an action potential is triggered. The resulting rapid depolarization, repolarization, brief hyperpolarization, and return to resting potential coincide with movement of sodium and potassium ions across the cell membrane.
• Neurotransmission: Sending The Message To Other Cells

  1. Synaptic vesicles (consists neurotransmitter): sac-like structures found inside the axon terminal containing chemicals

  2. Sodium triggered Synaptic Vesicles, arrived to the edges, dissolve

  3. Message from Axon terminal to Dendrites

  4. Neurotransmitter: chemical found in synaptic vesicles which, when released, has an effect on the next cell
• The Synapse


  The nerve impulse reaches the axon terminal, triggering the release of neurotransmitters from the synaptic vesicles. The molecules of neurotransmitter cross the synaptic gap to fit into the receptor sites that fit the shape of the molecule, opening the ion channel and allowing sodium ions to rush in.
• Synapse/Synaptic Gap


  Microscopic fluid-filled space between the rounded areas on the end of the axon terminals of one cell and the dendrites or surface of the next cell
• Receptor Sites


  Three-dimensional proteins on the surface of dendrites or certain cells of the muscles and glands, which are shaped to fit only certain neurotransmitters
• Neurotransmission: Neurons must be turned ON and OFF


  • Excitatory synapse: Turn on next cell, neurotransmitter that causes the receiving cell to fire
  • Inhibitory synapse: Stop action of the cell, neurotransmitter that causes the receiving cell to stop firing
• Some Neurotransmitters and Their Functions

  • Acetylcholine (ACh): Excitatory or inhibitory; involved in arousal, attention, memory, and controls muscle contractions
  • Norepinephrine (NE): Mainly excitatory; involved in arousal and mood
  • Dopamine (DA): Excitatory or inhibitory; involved in control of movement and sensations of pleasure
  • Serotonin (5-HT): Excitatory or inhibitory; involved in sleep, mood, anxiety, and appetite
  • Gamma-aminobutyric acid (GABA): Major inhibitory neurotransmitter; involved in sleep and inhibits movement
  • Glutamate: Major excitatory neurotransmitter; involved in learning, memory formation, nervous system development, and synaptic plasticity
  • Endorphins: Inhibitory neural regulators; involved in pain relief
• Neurotransmission: Leftover neurotransmitter


  1. Reuptake: process by which neurotransmitters are taken back into the synaptic vesicles

  2. Enzyme: complex protein that is manufactured by cells, remove extra neurotransmitter

  3. Enzymatic degradation: process by which the structure of a neurotransmitter is altered so it can no longer act on a receptor
• Dopamine is removed from the synapse by reuptake sites.


  Cocaine (yellow dots) acts by blocking dopamine reuptake sites, allowing dopamine to remain active in the synapse longer.
• Parts of the Brain

  • The cerebral hemispheres
  • The cortex
  • The limbic system
  • The hindbrain
  • Lobes and cortical areas
• The Hindbrain (lower part of the brain)


  • Medulla: first large swelling at the top of the spinal cord, forming the lowest part of the brain. Responsible for life-sustaining functions such as breathing, swallowing, and heart rate
  • Pons: larger swelling above the medulla that connects the top of the brain to the bottom. Plays a part in sleep, dreaming, left–right body coordination, and arousal
  • Reticular formation (RF): area of neurons running through the middle of the medulla and the pons and slightly beyond. Responsible for selective attention
  • Cerebellum: part of the lower brain located behind the pons. Controls and coordinates involuntary (heart rate), rapid, fine motor movement
• The Limbic System (Central part of the brain)

  • Thalamus: part of the limbic system located in the center of the brain. Relays sensory information from the lower part of the brain to the proper areas of the cortex, processes some sensory information before sending it to its proper area
  • Hypothalamus: small structure in the brain located below the thalamus and directly above the pituitary gland. Responsible for motivational behavior (basic human drive) such as sleep, hunger, thirst, and sex
  • Hippocampus: curved structure located within each temporal lobe. Responsible for the formation of long-term declarative memories. Leads to Anterograde Amnesia (unable to form new memory) and Retrograde Amnesia (forgot all about the past)
  • Amygdala: brain structure located near the hippocampus. Responsible for fear responses and memory of fear. Leads to inability to recognize/interpret fear, poor communication, and aggressive behaviour
  • Cingulate cortex (outer layer of brain): the limbic structure actually found in the cortex. Plays important roles in cognitive and emotional processing
• The Cortex (outer layer)

  • Corticalization: wrinkling of the cortex. Allows a much larger area of cortical cells to exist in the small space inside the skull
  • Cerebral hemispheres: the two sections of the cortex on the left and right sides of the brain
  • Corpus callosum: thick band of neurons that connects the right and left cerebral hemispheres
• Lobes and Cortical Areas of the Brain

  • Occipital lobe: section of the brain located at the rear and bottom of each cerebral hemisphere containing the visual centers of the brain
  • Parietal lobes: located at the top and back of each cerebral hemisphere containing the centers for touch, taste, and temperature sensations
  • Motor cortex: in the frontal lobe, controls the voluntary muscles of the body
  • Somatosensory cortex: located in the parietal lobe just behind the motor cortex, receives information about the sense of touch and body position
  • Temporal lobes: areas of the cortex along the sides of the brain, starting just behind the temples, containing the neurons responsible for the sense of hearing and meaningful speech (language)
• Temperature sensations


  Processed in the somatosensory cortex, an area of neurons running down the front of the parietal lobes
• Somatosensory cortex


  • Responsible for processing information from the skin and internal body receptors for touch, temperature, and body position
• Lobes and Cortical Areas of the Brain

  • Motor cortex
  • Somatosensory cortex
• Motor cortex


  Controls the voluntary muscles of the body, with cells at the top controlling muscles at the bottom and vice versa. Body parts are represented according to the number of cortical cells devoted to that part.
• Somatosensory cortex


  Receives information about the sense of touch and body position, organised in a similar manner to the motor cortex
• Lobes and Cortical Areas of the Brain

  • Temporal lobes
  • Primary auditory cortex
  • Auditory association cortex
• Temporal lobes


  Areas of the cortex along the sides of the brain, containing the neurons responsible for the sense of hearing and meaningful speech (language)
• Primary auditory cortex


  Processes auditory information from the ears
• Auditory association cortex


  Identifies and makes sense of auditory information
• Lobes and Cortical Areas of the Brain

  • Frontal lobes
  • Motor cortex
• Frontal lobes


  Areas of the cortex located in the front and top of the brain; responsible for higher mental processes, decision making, and the production of fluent speech such as logical reasoning and abstract thinking
• Motor cortex


  Rear section of the frontal lobe; responsible for sending motor commands to the muscles of the somatic nervous system
• Association areas


  Areas within each lobe of the cortex responsible for the coordination and interpretation of information, as well as higher mental processing
• Broca's aphasia


  Condition resulting from damage to Broca's area (usually in left frontal lobe), causing the affected person to be unable to speak fluently, to mispronounce words, and to speak haltingly
• Wernicke's aphasia


  Condition resulting from damage to Wernicke's area (usually in left temporal lobe), causing the affected person to be unable to understand or produce meaningful language
• Cerebrum


  The upper part of the brain consisting of the two hemispheres and the structures that connect them
• Split-Brain Research


  Study of patients with severed corpus callosum, involving sending messages to only one side of the brain to demonstrate right and left brain specialization
• Left side of the brain

  Seems to control language, writing, logical thought, analysis, and mathematical abilities. Processes information sequentially and enables one to speak.
• Right side of the brain

  Controls emotional expression, spatial perception, recognition of faces, patterns, melodies, and emotions. Processes information globally and cannot influence speech.
• Functions of left and right brain do not influence handedness
• Specialization of the Two Hemispheres

  • Left Hemisphere
  • Right Hemisphere