Unit 3 Biological Bases of Behavior PDF

. Unit 3: Biological Bases of Behavior This unit focuses on the biological influences on behavior, including neural communication, the brain and nervous system, genetics, and endocrine system functions. I. Neural Communication Neurons are the building blocks of the nervous system. They transmit...

. Unit 3: Biological Bases of Behavior This unit focuses on the biological influences on behavior, including neural communication, the brain and nervous system, genetics, and endocrine system functions. I. Neural Communication Neurons are the building blocks of the nervous system. They transmit electrical and chemical signals to communicate with other neurons, muscles, and glands. A. Structure of a Neuron ​ ​ Dendrites: Branch-like extensions that receive messages from other neurons. ​ ​ Cell Body (Soma): The neuron’s life-support center; contains the nucleus. ​ ​ Axon: A long fiber that carries messages away from the cell body toward other neurons or muscles. ​ ​ Myelin Sheath: A fatty layer that covers the axon to speed up neural impulses. ​ ​ Axon Terminals: Contain vesicles that release neurotransmitters into the synapse. ​ ​ Synapse: The tiny gap between neurons where neurotransmitters cross. B. Neural Firing (Action Potential) ​ ​ Resting Potential: The neuron is inactive (-70mV), with more negative ions inside than outside. ​ ​ Action Potential: A brief electrical charge that travels down the axon when the neuron fires. It happens when: ​ ​ 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. II. Neurotransmitters & Their Functions Neurotransmitters are chemical messengers that cross synapses and influence behaviors. Neurotransmitter Function Associated Disorders Acetylcholine (ACh) Muscle movement, learning, ↓ Linked to Alzheimer’s memory disease Dopamine Reward, motivation, ↑ Linked to schizophrenia, ↓ movement, attention Parkinson’s disease Serotonin Mood, hunger, sleep, arousal ↓ Linked to depression Norepinephrine Alertness, fight-or-flight ↓ Linked to depression, ↑ response anxiety GABA (Gamma-Aminobutyric Inhibitory neurotransmitter ↓ Linked to seizures, anxiety Acid) (calms the brain) disorders Glutamate Excitatory neurotransmitter, ↑ Linked to migraines, memory seizures Endorphins Pain relief, pleasure Released in response to pain or exercise ​ ​ Agonists: Drugs that mimic or increase neurotransmitter effects (e.g., morphine mimics endorphins). ​ ​ Antagonists: Drugs that block neurotransmitters (e.g., botulin blocks ACh, causing paralysis). III. Nervous System Organization The nervous system controls bodily functions and behavior through neurons, neurotransmitters, and neural networks. A. Central Nervous System (CNS) ​ ​ Brain: Processes information and coordinates responses. ​ ​ Spinal Cord: Connects brain to the body and handles reflexes. B. Peripheral Nervous System (PNS) ​ ​ Connects the CNS to the body through sensory and motor neurons. ​ ​ Two Main Divisions: ​ 1.​ Somatic Nervous System: Controls voluntary movements (skeletal muscles). ​ 2.​ Autonomic Nervous System (ANS): Controls involuntary functions (heart rate, digestion). ​ ​ Sympathetic Nervous System: Activates the fight-or-flight response (increases heart rate, releases adrenaline). ​ ​ Parasympathetic Nervous System: Activates rest-and-digest functions (slows heart rate, conserves energy). IV. The Brain & Its Functions The brain is divided into different regions responsible for various functions. A. The Brainstem (Oldest Part of the Brain) Controls basic life functions. ​ ​ Medulla: Regulates heartbeat, breathing, blood pressure. ​ ​ Pons: Helps with sleep, movement coordination. ​ ​ Reticular Formation: Controls arousal and alertness. B. The Limbic System (Emotions & Memory) ​ ​ Thalamus: The brain’s relay station (directs sensory information to the cortex). ​ ​ Hypothalamus: Regulates hunger, thirst, body temperature, emotions, and reward. Also controls the pituitary gland. ​ ​ Amygdala: Processes fear and aggression. ​ ​ Hippocampus: Forms new memories (damage can cause amnesia). C. The Cerebral Cortex (Higher Thinking & Consciousness) Divided into four lobes: Lobe Function Key Area Frontal Lobe Decision-making, planning, Motor Cortex, Prefrontal problem-solving, movement Cortex Parietal Lobe Touch, spatial awareness Somatosensory Cortex Occipital Lobe Vision Visual Cortex Temporal Lobe Hearing, language Auditory Cortex processing ​ ​ Broca’s Area: Speech production (damage = difficulty speaking). ​ ​ Wernicke’s Area: Language comprehension (damage = word salad). D. Hemispheric Specialization ​ ​ Left Hemisphere: Language, logic, math. ​ ​ Right Hemisphere: Spatial abilities, creativity, face recognition. ​ ​ Corpus Callosum: Connects the two hemispheres. ​ ​ Split Brain: When the corpus callosum is severed (used to treat epilepsy). V. Endocrine System (Hormones & Behavior) The endocrine system works alongside the nervous system but uses hormones instead of neurotransmitters. A. Major Glands & Hormones  Gland Hormone Function Pituitary (Master Gland) Growth Hormone Controls other glands Thyroid Thyroxine Metabolism Adrenal Adrenaline (Epinephrine) Fight-or-flight response Pancreas Insulin Regulates blood sugar Gonads (Ovaries & Testes) Estrogen, Testosterone Sexual development ​ ​ Hormones vs. Neurotransmitters: ​ ​ Neurotransmitters work faster but are short-term. ​ ​ Hormones work slower but last longer. VI. Genetics & Behavior ​ ​ Genotype vs. Phenotype: ​ ​ Genotype = genetic makeup. ​ ​ Phenotype = observable traits. ​ ​ Twin Studies: Help determine the influence of nature (genes) vs. nurture (environment). ​ ​ Heritability: The extent to which genetic differences contribute to individual differences. Key Studies in Unit 3 ​ ​ Phineas Gage (frontal lobe damage → personality change). ​ ​ Split Brain Research (Sperry & Gazzaniga) (hemispheric specialization). ​ ​ Twin Studies (Bouchard) (nature vs. nurture).