Lecture 3 PSY100 + Readings.docx

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School of Environment
Stephen Scharper

Lecture 3: Biological Functions Genes and the Environment - Nature and nurture are entwined - Cannot separate genetic influences from environmental influences - Work together to determine human behaviour - Epigenetics: changes in gene expression because of non-genetic influences Twin studies & Adoption studies - Study of impact of genetic vs. environmental influences - Monozygotic vs. dizygotic twins - Monozygotic twins raised together vs. apart o ‘shared genes’ and ‘shared’ environment less similar than raised apart o Whereas those twins that were raised apart were very similar in many aspects Heredity vs. Heritability Heredity – genetic transmission from parents to offspring Ex. Sally inherited blue eyes from mom Heritability – estimate of genetic portion of variation in some certain trait - Within certain population, not individuals Behaviour is determined by many factors - Single cause explanation may be accurate but incomplete - Behaviour governed by complex network of interacting factors o Heredity o Biology o Environment o Culture The Nervous System - Body’s electrochemical communication circuitry - 1 cm3 = 50 million nerve cells 1) Central Nervous System (CNP) - Spinal cord & brain 2) The Peripheral Nervous System - Sends info to CNS and responds to messages from CNS - Perform certain behaviours, make bodily adjustments Somatic nervous system (SNS) - Concerning external environment - Controls function that are under conscious voluntary control Ex. Voluntarily move muscle - Mainly motor neurons – efferent pathway sending signals from brain to muscles CNS ▯ muscles/skin/joints - Sensory neurons send signals to brain o Muscle/skin/joints ▯ CNS (sensory neurons, afferent pathway) Autonomic nervous system (ANS) - Internal environment - Glands/internal organs  CNS (somatosensory neurons) - CNS  glands/internal organs (motor neurons) 2 types of signals travel from CNS  glands/internal organs o Opposing function of sympathetic system but they work in complementary o Chronic activation of either system can lead to health problem Ex. High blood pressure, heart/kidney fail – sympathetic Low blood pressure, depression – parasympathetic 1) Sympathetic division o Prepares body for action o Can be activated by many things 2) Parasympathetic division o Returns body to normal state Spinal Cord - Connects brain to peripheral nervous system Neurotransmitters - Chemical substances that carry signals from one neuron to another - Stored vesicles (small packages) inside terminal buttons - Action potentials cause vesicles to fuse to presynaptic membrane (membrane of neuron that is sending the signal) - Release contents into synapse – received by postsynaptic receptors on the postsynaptic membrane (membrane of neuron that’s receiving signal Common neurotransmitter - Acetylcholine Paralyze muscles (botox) Motor control over muscles Learning, memory, sleeping, dreaming Monoamines - Epinephrine Adrenaline… - Norepinephrine Arousal, alertness - Serotonin Emotional states, impulsiveness Low levels = sadness, food cravings, anxious behaviours Selective serotonin reuptake inhibitors (SSRI) – block serotonin reuptake so more serotonin to bind with postsynaptic neurons treats depression, etc. - Dopamine Motivation, rewards, movement Ex. Eating when hungry activate dopamine receptors so exp as pleasure - GABA Inhibits synapse, lack of GABA = epilepsy Ex. alcohol - Glutamate Excitatory transmitter, opens sodium gates How Drugs Work Agonist 1) Enhance neurotransmitters’ action by o Increasing release of neurotransmitters o Blocking re-uptake of neurotransmitter o Mimicking a neurotransmitter 2) Inhibit by o Blocking release of NT o Destroying in synapse o Mimicking (& blocking neurotransmitter binding) E.g. Beta blockers, botox The Brain: From the Bottom Up Spinal Cord Connects brain to peripheral nervous system - coordinates each reflex – sensation to action - carry sensory info the brain & signals from brain to body - grey matter: cell bodies - white matter: axons & myelin sheaths Cortical structures ▯ complex mental activity Subcortical structures ▯ emotion and basic drives Cerebellum ▯ movement Brain Stem ▯ survival The Brain Stem - Controls basic life sustaining functions of autonomic nervous system - Breathing, digestion, heart rate - Network of neurons: Reticular formation ▯ alertness, sleep • Medulla oblongata • Pons • Midbrain The Cerebellum - Needed for coordinated movement and balance The Subcortical Structures - Master regulatory structure
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