Biological influences on behavior: Neural Communication

• Biological influences on behavior, including neural communication, the brain and nervous system, genetics, and endocrine system functions are the focus.
• Neurons are the building blocks of the nervous system that transmit electrical and chemical signals to communicate with other neurons, muscles, and glands.

Structure of a Neuron

• Dendrites are branch-like extensions that receive messages from other neurons.
• Cell Body (Soma) serves as the neuron's life-support center and contains the nucleus.
• Axon is a long fiber that carries messages away from the cell body toward other neurons or muscles.
• Myelin Sheath is a fatty layer that covers the axon to speed up neural impulses.
• Axon Terminals contain vesicles that release neurotransmitters into the synapse.
• Synapse is the tiny gap between neurons where neurotransmitters cross.

Neural Firing (Action Potential)

• Resting Potential: The neuron is inactive at -70mV, with more negative ions inside than outside.
• Action Potential: A brief electrical charge that travels down the axon when the neuron fires.
• Threshold is reached when excitatory signals outnumber inhibitory signals.
• Depolarization: Sodium (Na+) rushes in, making the inside more positive.
• Repolarization: Potassium (K+) moves out, restoring the negative charge.
• Refractory Period: A brief time where the neuron cannot fire again until it resets.
• All-or-None Principle: A neuron either fires at full strength or doesn't fire at all.

Neurotransmitters & Their Functions

• Neurotransmitters are chemical messengers that cross synapses and influence behaviors.
• Acetylcholine (ACh) impacts Muscle movement, learning, memory, and a lack can be linked to Alzheimer's disease
• Too much Dopamine is linked to schizophrenia, and too little is linked to Parkinson's disease. Dopamine impacts Reward, motivation, movement, and attention
• Serotonin impacts mood, sleep, hunger and arousal. Low levels can be linked to depression
• Norepinephrine impacts alertness, fight-or-flight response and low levels can be linked to depression, and high levels linked to anxiety
• GABA (Gamma-Aminobutyric Acid) as an Inhibitory neurotransmitter that calms the brain. Low levels can be linked to seizures, and anxiety disorders
• Glutamate serves as an Excitatory neurotransmitter, impacting memory/ High levels can be linked to migraines and seizures.
• Endorphins impact pain relief, and pleasure and are Released in response to pain or exercise
• Agonists are drugs that mimic or increase neurotransmitter effects (e.g., morphine mimics endorphins).
• Antagonists are Drugs that block neurotransmitters (e.g., botulin blocks ACh, causing paralysis).

Nervous System Organization

• The nervous system controls bodily functions and behavior through neurons, neurotransmitters, and neural networks.
• The Central Nervous System (CNS) includes the brain, which processes information and coordinates responses.
• The Spinal Cord connects the brain to the body and handles reflexes.
• The Peripheral Nervous System (PNS) connects the CNS to the body through sensory and motor neurons.
• The Somatic Nervous System controls voluntary movements (skeletal muscles).
• Autonomic Nervous System (ANS) controls involuntary functions (heart rate, digestion).
• The Sympathetic Nervous System activates the fight-or-flight response by increasing heart rate and releasing adrenaline.
• The Parasympathetic Nervous System activates rest-and-digest functions by slowing heart rate and conserving energy.

The Brain & Its Functions

• The brain is divided into different regions responsible for various functions.
• The Brainstem controls basic life functions
• Medulla regulates heartbeat, breathing, and blood pressure.
• Pons helps with sleep and movement coordination.
• The Reticular Formation controls arousal and alertness.
• The Limbic System impacts Emotions & Memory
• The Thalamus serves as the brain's relay station and directs sensory information to the cortex.
• The Hypothalamus regulates hunger, thirst, body temperature, emotions, and reward. It also controls the pituitary gland.
• The Amygdala processes fear and aggression.
• The Hippocampus Forms new memories; damage can cause amnesia.
• The Cerebral Cortex impacts Higher Thinking & Consciousness, and is divided into four lobes:
  • The Frontal Lobe impacts Decision-making, planning, problem-solving, and movement. Its key areas are in the Motor Cortex and Prefrontal Cortex
  • The Parietal Lobe impacts Touch and spatial awareness, and its key area is in the Somatosensory Cortex
  • The Occipital Lobe impacts Vision, and its key area is in the Visual Cortex
  • The Temporal Lobe impacts Hearing and language processing and its key feature is in the Auditory Cortex
    • Broca's Area: Speech production; damage results in difficulty speaking.
    • Wernicke's Area: Language comprehension; damage results in word salad.

Hemispheric Specialization

• The Left Hemisphere is associated with language, logic, and math.
• The Right Hemisphere is associated with spatial abilities, creativity, and face recognition.
• The Corpus Callosum connects the two hemispheres.
• A Split Brain occurs when the corpus callosum is severed which is used to treat epilepsy.

Endocrine System (Hormones & Behavior)

• The endocrine system works alongside the nervous system but uses hormones instead of neurotransmitters.
• Major Glands & Hormones
  • The Pituitary (Master Gland) releases Growth Hormone and controls other glands
  • The Thyroid releases Thyroxine, and impacts Metabolism
  • The Adrenal releases Adrenaline (Epinephrine) impacting Fight-or-flight response
  • The Pancreas releases Insulin and Regulates blood sugar
  • The Gonads (Ovaries & Testes) release Estrogen and Testosterone impacting sexual development
  • Neurotransmitters work faster but are short-term, whileHormones work slower but last longer.

Genetics & Behavior

• The Genotype is one's genetic makeup
• The Phenotype is one's observable traits.
• Twin Studies help determine the influence of nature (genes) vs. nurture (environment).
• Heritability marks the extent to which genetic differences contribute to individual differences.

Key Studies

- Phineas Gage (frontal lobe damage leading to personality change).
- Split Brain Research (Sperry & Gazzaniga) impacting hemispheric specialization.
- Twin Studies (Bouchard) impacting nature vs. nurture.