Biological Basis of Behavior

• NT = neurotransmitter, AP = action potential, NS = nervous system

Heredity vs. Environment

• Evolutionary psychology studies how natural selection influences behavior.
• Heredity (nature) = how genes influence behavior.
• Environment (nurture) = how outside situations influence behavior (e.g., school).
• Nature vs. Nurture: The answer is both.
  • Twin/Adoption Studies:
    • Genetics: Identical twins have a higher percentage of developing the same disease.
    • Environment: Identical twins raised in different environments show differences.

Nervous System

• Central NS: Brain and spinal cord.
• Peripheral NS: Rest of the NS - relays to Central NS.
  • Somatic NS: Voluntary movement, has sensory and motor neurons.
  • Autonomic NS: Involuntary organs (heart, lungs, etc.) - contains the:
    • Sympathetic NS: Fight/flight (generally activates, exception: digestion).
    • Parasympathetic NS: Rest/digest (generally inhibits, exception: digestion).

Neuron and Neural Firing

• Neuron: Basic cell of the NS.

  • Dendrites: Receive incoming NTs.
  • Axon: AP travels down this.
    • Myelin Sheath: Speeds up AP down axon, protects axon.
  • Synapse: Gap between neurons.

• Sensory neurons: Receive sense signals from the environment and send signals to the brain.

• Motor neurons: Send signals to move - end signals from the brain.

• Interneurons: Cells in the spinal cord/brain responsible for the reflex arc.

• Reflex arc: Important stimuli skip the brain and route through the spinal cord for immediate reactions (e.g., hand on a hot flame).

• Glial Cells: Support cells-give nutrients and clean up around neurons

• Neurons Fire with an Action Potential:

  • Ions move across the membrane, sending an electrical charge down the axon.
    • Resting potential: Neuron maintains a -70mv charge when not doing anything.
    • Depolarization: Charge of neuron briefly switches from negative to positive - triggers the AP.
    • Threshold of depolarization: Stimulus strength must reach this point to start the AP (+40).
    • All or nothing principle: Stimulus must trigger the AP past its threshold but does not increase the intensity or speed of the response (flush the toilet).
    • Refractory period: Neuron must rest and reset before it can send another AP (toilet resets).

Neurotransmitters (NT)

• Chemicals released in the synaptic gap, received by neurons, and classified as excitatory (increase APs) or inhibitory (decrease APs).
  • GABA: Major inhibitory NT.
  • Glutamate: Major excitatory NT (glutes excite you!).
  • Dopamine: Reward (short term) & fine movement - in the hypothalamus, associated with addiction.
  • Serotonin: Moods (long-term), emotion, sleep - in the amygdala, too little associated with depression.
  • Acetylcholine (ACh): Memory and movement - in the hippocampus, associated with Alzheimer's.
  • Norepinephrine: Sympathetic NS - too little associated with depression.
  • Endorphins: Decrease pain.
  • Substance P: Pain regulation (abnormality increases pain and inflammation).

Hormones:

• If not in the nervous system, it's a hormone.

Psychoactive Drugs

• Depressants: Decrease NS activity (alcohol).
• Stimulants: Increase NS activity (caffeine & cocaine).
• Hallucinogens: Hallucinations and altered perceptions (Marijuana).
• Opioids: Relieve pain (endorphin agonists) (heroin).
• Tolerance: Needing more of a drug to achieve the same effects.
• Addiction: Must have it to avoid withdrawal symptoms.
• Withdrawal: Symptoms associated with sudden stoppage.

The Brain

• Cerebellum: Movement, balance, coordination, procedural memory (walking a tightrope balancing a bell).

• Brainstem/Medulla: Vital organs (HR, BP, breathing).

• Reticular activating system: Alertness, arousal, sleep, eye movement.

• Cerebral Cortex: Outer portion of the brain - higher-order thought processes - includes the limbic system, lobes, corpus callosum.

  • Limbic System:
    • Amygdala: Emotions, fear.
    • Hippocampus: Episodic and semantic memory (if you saw a hippo on campus, you'd remember it!).
    • Hypothalamus: Reward/pleasure center, eating behaviors - link to endocrine system, homeostasis.
    • Thalamus: Relay center for all but smell.
      • Pituitary gland: Talks with the endocrine system and hypothalamus - release hormones.
        • Oxytocin: Love, bonding, childbirth, lactation.
        • Adrenaline: Fight/flight.
        • Leptin: Makes you full (stops hunger).
        • Ghrelin: Makes you hungry (turns you into a gremlin).
        • Melatonin: Sleep.

• Agonist: Drug that mimics a NT.

• Antagonist: Drug that blocks a NT.

• Reuptake: Unused NTs are taken back up into the sending neuron (antidepressants cause reuptake inhibition (block reuptake) - treatment for depression).

Lobes

• Frontal Lobe: Decision-making, planning, judgment, movement, personality, language, executive function - includes the:
  • Prefrontal cortex: Front of the frontal lobe - executive function.
  • Motor Cortex: Back of the frontal lobe - map of our motor receptors - controls skeletal movement.
• Parietal Lobe: Sensations and touch, controls association areas - includes:
  • Somatosensory Cortex: Map of our touch receptors.
• Temporal Lobe: Hearing and face recognition, language.
• Occipital Lobe: Vision.