Biology and Behavior: Influences on Behavior

Introductions

• Presenter: Iman
• Topic: Influences on Behavior
• Focus: Chemical controls, hereditary, and environmental factors

Chemical Controls (Neurotransmitters)

• Over 100 neurotransmitters identified
• Focus on 7 key neurotransmitters for the MCAT

Acetylcholine

• Found in: Central & peripheral nervous systems
• Functions:
  • Peripheral: Transmit nerve impulses to muscles
  • Central: Linked to attention and arousal

Epinephrine and Norepinephrine

• Classification: Catecholamines and monoamines (biogenic amines)
• Functions:
  • Controlling alertness and wakefulness
  • Primary transmitters of the sympathetic nervous system (fight-or-flight response)
• Distinct Roles:
  • Norepinephrine: Acts locally, associated with depression (low levels), anxiety, and mania (high levels)
  • Epinephrine: Secreted from adrenal medulla, acts systemically as a hormone

Dopamine

• Role: Movement and posture
• High Concentration Area: Basal ganglia
• Implications: Found in high concentrations in basal ganglia. Imbalances linked to schizophrenia (Dopamine Hypothesis)
• Condition Details: Too much/lack of dopamine sensitivity tied to hallucinations, delusions, agitation

Serotonin

• Classification: Monoamine or biogenic amine
• Functions: Regulating mood, eating, sleeping, dreaming
• Implications:
  • Oversupply linked to manic states
  • Undersupply linked to depression

GABA, Glycine, Glutamate

• GABA:
  • Produces inhibitory postsynaptic potentials
  • Stabilizes neural activity
  • Causes hyperpolarization of postsynaptic membrane
• Glycine:
  • Inhibitory neurotransmitter in the central nervous system
  • Increases chloride influx, leading to hyperpolarization
• Glutamate:
  • Excitatory neurotransmitter

Peptide Neurotransmitters (Neuropeptides)

• Role: More complex chain of events in postsynaptic cell
• Key Example: Endorphins (natural painkillers)
  • Actions similar to morphine or other opioids

Endocrine System

• Communication: Uses hormones (chemical messengers)
• Comparison to Nervous System: Slower, hormones travel through bloodstream

Hypothalamus

• Links endocrine and nervous systems
• Regulates pituitary gland's hormonal function
• Control through paracrine release into hypophyseal portal system

Pituitary Gland

• Nickname: Master gland
• Location: Base of the brain
• **Divisions: Anterior and Posterior Pituitary
• Functions:
  • Anterior pituitary releases hormones regulating endocrine gland activities
  • Controlled by hypothalamus
  • Secretes hormones into bloodstream**

Adrenal Glands

• Location: Top of kidneys
• Divisions: Adrenal medulla and adrenal cortex
• Functions:
  • Adrenal Medulla: Releases epinephrine and norepinephrine
  • Adrenal Cortex: Produces corticosteroids (e.g., cortisol), sex hormones like testosterone and estrogen

Gonads

• Female: Ovaries
• Male: Testes
• Function: Produces sex hormones (testosterone in males, estrogen in females)
  • Increases libido
  • Contributes to mating behavior and sexual function

Genetics and Behavior

• Inheritance: Behavioral traits can be inherited just like physical traits
• Species-specific behaviors: e.g., Mating behaviors

Types of Behavior

• Innate Behavior: Genetically programmed, observable across all species members
• Learned Behavior: Develops through experience and environment

Adaptive Value

• Contribution to species' evolutionary fitness
• Results in adaptations via natural selection

Nature vs. Nurture

• Nature: Genetic influence on behavior
• Nurture: Environmental and experiential impact
• Consensus: Behavior results from genetics and environment interaction

Research Methods

• Family Studies: Identify genetic similarity; however, environmental factors are also shared
  • Example: Schizophrenia higher in children of schizophrenics
• Twin Studies: Compare monozygotic (identical) and dizygotic (fraternal) twins
  • Identical twins raised apart exhibit more similar traits than fraternal twins raised together
• Adoption Studies: Compare adopted children to biological and adoptive parents
  • Traits like IQ and criminal behavior have heritable components

Conclusion

• Both genetics and environment significantly shape behavior
• Relative influence varies by trait, with some traits being more genetically influenced and others more environmentally influenced

Next Steps

• Next Video: Final objective on development
• Engagement: Questions, comments, concerns encouraged