Biological Psychology PDF Introductory Psychology I Fall 2024

Introductory Psychology I Fall 2024 The Neuron Learning objectives Learn the major components of the neuron and understand their function Explain the major steps of the action potential and how they help neurons communicate via the synapse Understand what a neurotransmitter is,...

Introductory Psychology I Fall 2024 The Neuron Learning objectives Learn the major components of the neuron and understand their function Explain the major steps of the action potential and how they help neurons communicate via the synapse Understand what a neurotransmitter is, and explain the function of a variety of major neurotransmitters The problem: How can an animal sense and interact with its surrounding environment? The solution: The nervous system Two major components: Central nervous system – Brain & spinal cord Peripheral nervous system – Motor and sensory neurons These two systems work together to help an animal sense physical attributes of their environment (i.e. sensation and perception), and to respond to these sensations (i.e. behaviour) Biological organization Anatomy of the neuron Axon Terminal Oligodendrocyte Anatomy of the neuron Cell body (soma): Centre of neuron; builds new cell components Dendrites: Branchlike extensions that receive information Axons: “Tails” that transit information Axon terminal: Knob at the end of the axon containing synaptic vesicles filled with neurotransmitters Myelin sheath: An insulated covering around the axon that increases the speed of neuronal transmission, formed by oligodendrocytes in the brain Glial cells Play a support role in the brain Astrocytes: Star shaped glial cells that provide structural support and increase reliability of neuronal transmission Oligodendrocytes: Promote new connection and produce myelin sheath around axons Neurons are arranged into a network Resting potential Membrane potential when the neuron is not being stimulated or inhibited ~-70 mV Action potential Electrochemical impulse travelling down the axon membrane that results in neurotrasmitter release Requires stimulation to threshold of excitation (~55mV) The action potential signals for neurons to communicate – it is an all or nothing response Triggered by a change in charge inside the axon passed the threshold amount, depolarization occurs Neuron quickly repolarized In between firings, there is a very brief absolute refractory period Neurons can fire 100 to 1,000 times per second The action potential is controlled by the cell membrane Mylenation allows for action potentials to send faster signals Neurons are arranged into a network Neurotransmitters (NTs) Chemical messengers that allow neuron to neuron communication Synapse (synaptic cleft) Space between neurons through which NTs travel The synapse allows two (or multiple) neurons to communicate z z The signal sent to the post-synaptic neuron can cause an excitatory response (EPSP) Or inhibit it (IPSP) Neurotransmitters Some NTs excite while others inhibit cells Each NT has a specific role and function in brain and body function New associations are made in the brain through the connection of two or more neurons at the synapse (neurogenesis and neuroplasticity) Glutamate An amino acid, it is the most common excitatory neurotransmitter in the mammalian brain It increases the likelihood of neurons firing GABA (Gamma-Aminobutyric Acid) An amino acid, and is the main inhibitory neurotransmitter in the mammalian brain It decrease the likelihood of neurons firing Acetylcholine Acetylcholine influences arousal, selective attention, sleep and memory Neurons that connect to muscles release acetylcholine to trigger movement Dopamine Motor function Centrally involved in the sensation of “pleasure” Important for motivation Dopamine overload? Norepinephrine Associated with physiological arousal and stress “Fight or Flight” response Serotonin Regulates intestinal function and energy allocation Regulation of emotions Psychoactive drugs Drugs that interact with neurotransmitters systems Agonists enhance receptor site activity (e.g., Drugs that mimic neurotransmitters, like opiates) Antagonists decrease receptor site activity (e.g., Drugs that block the receptor sites of neurotransmitters, like antipsychotics) Neural Plasticity Neural plasticity describes the nervous system’s ability to change Neurons change in four ways during development and learning Growth of dendrites and axons Synaptogenesis Pruning Myelination Once we reach adulthood, neurogenesis decreases sharply, but we can sometimes recover partially from brain injury and illness via plasticity  Why doesn’t the brain heal in the same way that other tissues can? “Neurons don’t undergo mitosis in the same way that other cells do.” Okay…... But why don’t neuron’s divide in the same way as other cells? Likely a trade-off between healing capacity and stability/complexity Connections between neurons in the brain need to be very stable and precise… the capacity to divide might just screw that up  Linking it all together Whether or not a neuron fires (sends a message) is determined by electrical impulses Neurons send messages to one another via chemicals These chemicals influence the probability of neighbouring neurons firing To the best of our knowledge, the complex interplay between these interactions is the mechanism that underlies our thoughts, feelings, and behaviour! Introductory Psychology I Fall 2024 The Nervous System Learning Objectives List the major structures of the cortex, limbic system, and brain stem, and describe each of their functions Explain four major methods used to study the brain, and describe what each method can teach us Compare the mechanism of a hormone to that of neurotransmitters, and describe the function of 3 major endocrine organs The central nervous system Consists of the brain and spinal cord Brain controls many important functions related to behaviour Spinal cord connects brain to peripheral nerves and plays important role in sensation and motor ability The brain: a network of around 100 billion neurons 15% of cardiac output 20% total oxygen use 25% of glucose use A simplified view of the brain The hindbrain BASIC SURVIVAL Regulation of heart, breathing Typically very consistent and rigid in responses to stimulus The limbic system Memory and emotions The cerebral cortex THINKING Decision making Creativity Language “Seat” of consciousness Voluntary movements Humans have the largest brain:body size ratio Variation in brain size A fly brain consists of ~338,000 neurons A honeybee brain has ~850,000 neurons A mouse brain has ~10 billion neurons A human brain has ~86 billion neurons!. honey bee  They also have the most cortical neurons out of all land animals Estimated 16 billion – 21 billion A deeper dive into the CNS CNS Protection from external damage The CNS is protected by three layers of meninges The cerebral ventricles, fluid-filled pockets, also serve to protect the CNS Ventricles are filled with cerebrospinal fluid (CSF) Cerebral Cortex Majority of the forebrain is composed of the cerebral cortex Can be divided into four lobes, each associated with a different function Divided into two hemispheres, where each hemisphere has the same four lobes Corpus Callosum Consists of two cerebral hemispheres connected by the corpus callosum which allows communication between them Some functions “lateralized”, but ultimately the two sides work together Frontal Lobes (in front of central sulcus) Assist in motor function, language, memory Monitor and organize most other brain functions (executive functioning) Broca’s area is involved in speech production Prefrontal cortex is responsible for responsible for thinking, planning, and language Parietal Lobe Specialized for touch and perception Contains the somatosensory cortex, which is sensitive to pressure, pain, and temperature Communicates information to the motor cortex every time we reach, grasp, or move our eyes Motor and somatosensory cortices The body is mapped onto the motor cortex Motor involved in voluntary movement, somatosensory in tactile sensation and perception (touch)  Temporal Lobe Lower part of the cerebral cortex, it plays a role in hearing, understanding language Contains the auditory cortex and Wernicke’s area, which is responsible for speech comprehension Occipital Lobe Specialized for vision Located at the back of the brain Basal Ganglia Two sets of structures buried inside the cortex that helps control movement Damage can contribute to Parkinson’s disease Limbic System The emotional centre of the brain that also has a role in smell, motivation, and memory Hypothalamus regulates and controls internal bodily states; controls the pituitary gland Thalamus relays information from the sense organs to primary sensory cortex Amygdala plays a key role in fear, excitement and arousal Hippocampus plays a role in spatial memory; damage causes inability to form new memories  Quick break – consider the following case Patient gets into car accident, and enters a 5-week coma When he awakens, he recognizes his parents, but claims they are imposters Otherwise lucid, rational, and emotionally stable. But this delusion persisted for 2 years! Delusion limited to visual contact – when the patient spoke to his parents on the phone, he didn’t think they were impostors. A neurologist suspects damage related to the FFG and/or amygdala. Where might the damage be specifically? Fusiform face gyrus (in temporal lobe) Neurons in the FFG respond to Amygdala assess the faces. emotional significance of a stimulus Brain Stem Located at the very back of the brain Connects the cerebral cortex and spinal cord Performs some basic bodily functions Serves as a relay station between the cortex and rest of the nervous system Cerebellum plays a predominant role in our sense of balance and enables us to coordinate movement and learn motor skills Pons connects cortex to cerebellum and triggers dreams Medulla regulates breathing, heartbeat, and other vital functions Midbrain contributes to movement, tracking of visual stimuli, and reflexes triggered by sound Spinal Cord The thick bundle of nerves that conveys signals between the brain and the body Sensory nerves carry information from body to the brain, motor nerves carry information from brain to the rest of the body Also contains interneurons, which allow reflexes to happen Peripheral Nervous System Nerves that extend outside the CNS Divided into two branches Somatic nervous system conveys information from the CNS to the muscles in the body, controlling and coordinating voluntary movement Autonomic nervous system controls the involuntary actions of our internal organs and glands; has two divisions Autonomic Nervous System Sympathetic division is engaged during a crisis or after actions requiring fight or flight Parasympathetic division controls rest and digestion When one is activated, the other is inactive How can we study the brain? Lesion studies Damage, removal, or lesion of part of the brain In non-human animals, intentional removal of a brain area is called ablation Trans Magnetic Stimulation (TMS) Electrical stimulation and single cell recording Electrical stimulation of specific brain area, observe functional outcome Recording the activity of a single neuron to determine function Structural neuroimaging Allow us to non-invasively observe the structure of the human brain Can detect structural abnormalities X-ray CT, MRIs Functional neuroimaging Allows us to view which areas of the brain are functioning Electrical impulses (EEG) Oxygen in blood supply (fMRI) Endocrine System Is a system of glands and hormones controlling the secretion of blood- borne chemical messengers Hormones are molecules that are released by a cell and bind to a receptor, usually on another cell, and often in a different gland/organ Pituitary Gland Controlled by the hypothalamus In turn, controls the other glands in the body Releases hormones that influence growth, blood pressure, and other functions Included in these hormones is oxytocin, which is responsible for numerous reproductive functions, implicated in maternal and romantic love Adrenal Glands Located on top of the kidneys Emergency centre, releases adrenaline and cortisol during states of emotional arousal Adrenaline boosts energy production in muscle cells, restricts it in others Cortisol regulates blood pressure and cardiovascular function, as well as the use of proteins, carbohydrates and fats Sexual Reproductive Glands Testes in males and ovaries in females Both sexes manufacture testosterone and estrogen Introductory Psychology I Winter 2024 Evolution and Genetics True or False? 1.) Evolution acts on individuals FALSE 2.) Adaptive evolution leads to “better,” or “more complex” forms FALSE 3.) Adaptive evolution is a random process FALSE Let’s start by clearing our minds of what we know about evolutionary theory… Misconception #1 Misconception: Evolution acts on individuals Correction: Individuals do not evolve, populations do! Misconception # 2 Misconception: Adaptive evolution is progressive, leading to “better” or “more complex” species Correction: evolution does not necessarily lead to more complex forms, species only adapt to what is most fit for their environment – in fact, some traits may adapt to simpler forms depending on what is fit Misconception #3 Misconception: Adaptations evolve by random chance Correction: Mutations arise randomly, but the process of adaptive evolution (natural selection) is anything but random! Learning Objectives Define evolution from a biological perspective Describe how a gene’s expression influences phenotype Explain why mutations are the ultimate source of all genetic variation List and explain Darwin’s three conditions of natural selection What is DNA? DNA is a molecule that consists of 4 distinct nucleotides (A, G, C, and T) These nucleotides act as a “code” that instructs a cell to produce proteins These protein influence everything about the organism, ranging from how it looks to how it behaves!  Genes and alleles We all have the same genes But, we have different alleles Different alleles = different proteins = different traits! Since we have two sets of chromosomes, we have two copies of each gene How is DNA stored? Chromosomes  Gene expression?: From genes to behaviour All expressed biological Environment traits (phenotypes) are influenced in part due to genetics and the environment DNA inside the nucleus is transcribed into RNA RNA is translated by ribosomes in the cell into proteins Each protein has a specific function that contributes to determine every trait expressed by Phenotype an organism. This expressed trait is called a phenotype Expression of alleles Different alleles are expressed in different ways depending on the number of copies: Homozygous Heterozygous Or depending on the interaction between the proteins that the alleles produce: Dominant Recessive Homozygous vs Heterozygous Homozygous: two copies of the same allele for a given gene Heterozygous: two different alleles for a given gene homozygous heterozygous homozygous Genotype: Dominant vs Recessive Dominant expression: Always expressed, even with one copy Recessive expression: Only expressed when two copies present homozygous heterozygous homozygous Genotype: Phenotype: Let’s assume red is dominant and orange is recessive A biological definition of evolution Evolution: A change in the frequency of an allele or genotype in a population over time Generation 1 Generation 2  A biological definition of evolution Evolution: A change in the frequency of an allele or genotype in a population over time Gene: a distinct sequence of heritable DNA Allele: unique copy of a gene (or a gene variant) Genotype: the genetic constitution of an organism (the allele(s) the organism has) Phenotype: The observable expression of a trait (e.g., eye colour, aggression) Phenotypic evolution: A change in the frequency of alleles, resulting in a change in the distribution of phenotypic traits in a population Quick break Blue eyes are recessive to brown eyes Could two parents with brown eyes produce a child with blue eyes? If so, explain how this could be possible Where do new alleles come from?: Mutations A novel genetic difference between parents and offspring At the molecular level, mutations represent a “mistake” that occurs during DNA replication Mutations arise randomly And mutations are the ultimate source of all variation How is DNA inherited? Gregor Mendel 1822-1884 Inheritance and selection understood for centuries, but not their mechanisms Darwin’s theory of natural selection Voyage of the Beagle (1831-1836) Origin of Species (1859) Natural selection: the differential survival and reproduction of individuals due to differences in traits. Natural selection Natural selection: the differential survival and reproduction of individuals due to differences in traits Adaptation: Adaptations increase the ability to survive and reproduce compared to individuals without the trait Hence, natural selection leads to the evolution of adaptations Three conditions of natural selection 1.) Individuals within the population must vary in phenotypic traits 2.) At least some of the variation must have a genetic basis (i.e., is heritable) 3.) This variation must influence reproductive success in terms of survival or reproduction Variation Differences in quantifiable traits between individuals Individuals vary in phenotypic traits both within and across species Variation provides the “raw material” for evolution Heritability The proportion of variation in a trait that is due to genetic differences We now know that genes are the mode of all inheritance Survival and reproduction Survival means nothing if successful reproduction cannot occur But, traits that increase survival typically improve reproductive success More opportunity Sexual selection  Darwin’s theory of sexual selection Why do certain species have traits that apparently have no survival benefit, and in some cases are even costly for survival? Why do males and females of the same species tend to differ in some traits? Sexual selection: a mode of natural selection in relation to sex (i.e. reproductive success) Mate choice and competition Mate choice: Members of one sex choosing mates of the opposite sex Competition: Two members of the same sex competing for access to mates The sex that produces eggs is usually choosier when selecting a mate The sex that produces sperm usually engages in more intense competition for mates Inclusive fitness Inclusive fitness refers to the fact that an organism’s fitness is also influenced by the reproductive success of their relatives This is because relatives share a predictable amount of alleles This can explain the evolution of behaviours related to altruism, cooperation, and parental care