Biological Psychology: The Nervous System - Neurons

BIOLOGICAL PSYCHOLOGY The Use of Animal In Research Biological Approach Why do they study nonhumans? Biological Psychology – the study of the physiological,...

BIOLOGICAL PSYCHOLOGY The Use of Animal In Research Biological Approach Why do they study nonhumans? Biological Psychology – the study of the physiological, 1. The underlying mechanisms of behavior are similar across species evolutionary, and developmental mechanisms of behavior and and sometimes easier to study in a nonhuman species. experience. The term biological psychology emphasizes that the goal 2. We are interested in animals for their own sake. Humans are is to relate biology to issues of psychology. naturally curious. Neuroscience includes much that is relevant to behavior but also 3. What we learn about animals sheds light on human evolution. includes more detail about anatomy and chemistry. 4. Legal or ethical restrictions prevent certain kinds of research on humans. Three Main Points to Remember: 1. Perception occurs in your brain. LESSON 2.1 2. Mental activity and certain types of brain activity are, so far as we THE NERVOUS SYSTEM can tell, inseparable (monism as opposed to dualism). NEURONS - receive information and transmit it to other cells. They 3. We should be cautious about what is an explanation and what is are specialized cells found in the nervous system. not. THE STRUCTURES OF ANIMAL CELL BIOPSYCHOLOGY 1. Membrane - A structure that separates the inside of the cell from Physiological Psychology - Studies the neural mechanisms of the outside environment. behavior through the direct manipulation and recording of the 2. Protein Channel - It permits a controlled flow of water, oxygen, brain in controlled experiments. sodium, potassium, calcium, chloride, and other important chemicals inside the cell. Psychopharmacology - Similar to physiological psychology except 3. Nucleus - Central processing body of the cell. It is the structure that it focuses on the manipulation of neural activity and that contains the chromosomes. behavior with drugs. 4. Mitochondrion - The structure that performs metabolic activities, providing the energy that the cell uses for all activities. Neuropsychology - The study of the psychological effects of brain 5. Ribosomes - The sites within a cell that synthesize new protein dysfunction in human patients; patients with brain dysfunction molecules (building blocks of the cell). resulting from disease, accident, or neurosurgery. 6. Endoplasmic Reticulum - A network of thin tubes that transport newly synthesized proteins to other locations. Psychophysiology - Studies the relation between physiological activity and psychological processes in humans using THE STRUCTURES OF NEURON noninvasive methods. Motor Neuron - A motor neuron, with its soma in the spinal cord, receives excitation through its dendrites and conducts impulses along Cognitive Neuroscience - Study the neural bases of cognition, a its axon to a muscle. term that generally refers to higher intellectual processes such as Sensory Neuron - A sensory neuron is specialized at one end to be thought, memory, attention, and complex perceptual processes. highly sensitive to a particular type of stimulation, such as light, sound, or touch. Comparative Psychology - Comparative psychologists compare the behavior of different species in order to understand the evolution, THE STRUCTURES OF NEURON genetics, and adaptiveness of behavior. 1. Dendrites - They have synaptic receptors that receives information from other neurons; more surface are, more information. Biological Explanations to Behavior 2. Cell Body / Soma - It contains the nucleus, ribosomes, and Physiological Explanation mitochondria. ▪ It relates a behavior to the activity of the brain and other organs. It 3. Axon - The axon conveys an impulse toward other neurons, an deals with the machinery of the body. organ, or a muscle. A neuron can only have one axon. ▪ The chemical reactions that enable hormones to influence brain 4. Myelin Sheath - It covers the axons, which speeds up the activity and the routes by which brain activity controls muscle transmission. It has interruptions known as nodes of Ranvier. contractions. 5. Presynaptic Terminal - The swelling end part of axon. They release chemicals that cross through the junction between that Ontogenetic Explanation neuron and another cell. ▪ It describes how a structure or behavior develops, including the 6. Synapses- These are the junctions between the axon of a neuron influences of genes, nutrition, experiences, and their interactions. and a dendrite of another neuron. ▪ Males and females differ on average in several ways. Some of 7. Efferent Neuron - It carries information away from a structure. those differences can be traced to the effects of genes or prenatal Every motor neuron is an efferent from the nervous system. hormones, some relate to cultural influences, many relate partly to Efferent (E) = Exit both. 8. Afferent Neuron - It brings information into a structure. Every sensory neuron is an afferent to the rest of the nervous system. Evolutionary Explanation Afferent (A) = Admit ▪ The characteristic features of an animal are almost always 9. Interneuron - If a cell's dendrites and axon are entirely contained modifications of something found in ancestral species. within a single structure. ▪ Bat wings are modified arms, and porcupine quills are modified hairs, and humans evolved to use tools occasionally. GLIA (or neuroglia), the other components of the nervous system, perform many functions. Functional Explanation Glia outnumber neurons in the cerebral cortex, but neurons ▪ It describes why a structure or behavior evolved as it did. outnumber glia in several other brain areas. ▪ Dominant male with many offspring spreads all his genes, including some that may have been irrelevant to his success or even SEVERAL TYPES OF GLIA disadvantageous. 1. Astrocytes - An astrocyte helps synchronize closely related neurons, enabling their axons to send messages in waves. SODIUM-POTASSIUM PUMP Astrocytes are therefore important for generating rhythms. The sodium-potassium pump is a protein complex, repeatedly 2. Microglia - Act as part of the immune system, removing viruses transport three sodium ions out of the cell while drawing two and fungi from the brain. They remove dead or damaged neurons or potassium ions into it. weak synapses. It helps maintain the electrical gradient. 3. Oligodendrocytes - Found in the brain and spinal cord. They build It is an active transport that requires the myelin sheaths that surround and insulate certain vertebrate energy. axons. 4. Schwann Cells - Found in the periphery of the body. They build ACTION POTENTIAL the myelin sheaths that surround and insulate certain vertebrate - The resting potential remains stable until the neuron is stimulated. axons. When stimulated, messages sent by axons are called action 5. Radial Glia - Guide the migration of neurons and their axons and potentials. dendrites during embryonic development. - An action potential is a rapid depolarization of the neuron. - Stimulation of the neuron past the threshold of excitation triggers a (2) BLOOD-BRAIN BARRIER nerve impulse or action potential. WHY DO WE NEED A BLOOD-BRAIN BARRIER? Unlike any other cells in the body, nerve cells are not easily PROPAGATION OF ACTION POTENTIAL replaceable. To minimize the risk of irreparable brain damage, the - is the term used to describe the transmission of the action body lines the brain's blood vessels with tightly packed cells that keep potential down the axon. out most viruses, bacteria, and harmful chemicals. - the action potential does not directly travel down the axon. Neurotransmitters HOW DOES IT WORK? Capillary walls in the brain joined so tightly that they block viruses, 2.3 bacteria, and other harmful chemicals from passage. TYPES AND FUNCTIONS OF NEUROTRANSMITTERS No special mechanism is required for small, uncharged molecules THE SEQUENCE OF CHEMICAL EVENTS AT A SYNAPSE such 02, CO2, and fat-soluble molecules. Neurotransmitters – one of the chemical messengers that transmit For other chemicals, the brain uses active transport, a signals across synapses(gaps) between neurons (nerve cells) in the protein-mediated process that expends energy to pump chemicals brain and throughout the nervous system. from the blood into the brain. The Sequence of Chemical Events at the Synapse: 1. The neuron synthesizes chemicals that serve as neurotransmitters. Nourishment of Vertebrate Neurons It synthesizes the smaller neurotransmitters in the axon terminals and Most cells use a variety of carbohydrates and fats for nutrition, but synthesizes neuropeptides in the cell body.. vertebrate neurons depend almost entirely on glucose, a sugar. 2. Action potentials travel down the axon. At the presynaptic terminal, The liver makes glucose from many kinds of carbohydrates and an action potential amino acids, as well as from glycerol, a breakdown product from fats. enables calcium to enter the cell. Calcium releases neurotransmitters To use glucose, the body needs vitamin B1, thiamine. from the terminals and into the synaptic cleft, the space between the presynaptic and 2.2 postsynaptic neurons. THE NERVE IMPULSE 3. The released molecules diffuse across the narrow cleft, attach to NERVE IMPULSE - The electrical message that is transmitted down receptors, and alter the activity of the postsynaptic neuron. the axon of a neuron in a response to stimulus. Mechanisms vary for altering that activity. The impulse does not travel directly down the axon but is regenerated 4. The neurotransmitter molecules separate from their receptors. at points along the axon. 5. The neurotransmitter molecules may be taken back into the presynaptic neuron for recycling or they may diffuse away. THE RESTING POTENTIAL - The resting potential of a neuron refers 6. Some postsynaptic cells send reverse messages to control the to the state of the neuron prior to the sending of a nerve impulse. further release of neurotransmitters by presynaptic cells. POLARIZATION Sequence of Chemical Events at a Synapse The membrane of a neuron maintains an electrical gradient, also 1. Synthesis - The neuron synthesizes neurotransmitters—small known as polarization a difference in the electrical charge inside and ones in the axon terminals, neuropeptides in the cell body. outside of the cell. 2. Release - Action potentials travel down the axon, triggering The electrical potential inside the membrane is slightly negative with calcium influx and neurotransmitter release into the synaptic cleft. respect to the outside, mainly because of negatively charged proteins 3. Binding - The neurotransmitters diffuse across the cleft and bind inside the cell. This difference in voltage is called the resting to receptors on the postsynaptic neuron, altering its activity. potential. 4. Separation - The neurotransmitter molecules detach from the It has a typical level of -70millivolts (mV) but it varies from one receptors. neuron to another. 5. Reuptake or Breakdown - Some neurotransmitters are reabsorbed by the presynaptic neuron for recycling, while others At rest, the membrane maintains an electrical polarization or a diffuse away or are broken down. difference in the electrical charge of two location (inside and outside) 6. Regulation - Some postsynaptic neurons send reverse signals to INSIDE OF THE CELL regulate further neurotransmitter release. slightly negative mainly because of negatively charge proteins. Example: SSRIs (Selective Serotonin Reuptake Inhibitors) block OUTSIDE OF THE CELL serotonin reuptake, increasing its levels to treat depression. slightly positive due to positively charged proteins. The membrane is selectively permeable, allowing some chemicals Types of Neurotransmitters & Their Functions to pass more freely than others. 1. Amino Acids Sodium, potassium, calcium and chloride pass through channels Glutamate – Most abundant neurotransmitter; promotes neural in the membrane. excitation. GABA (Gamma-Aminobutyric Acid) – Inhibitory neurotransmitter the “stress hypothesis” of the etiology of depression. that reduces excitability, promotes relaxation, and prevents overstimulation. Hormones are chemicals secreted by glands into the bloodstream, Glycine – Works with GABA to inhibit excessive neural activity, affecting distant target cells. especially in spinal reflexes. Neurotransmitters function like a telephone signal (direct, fast 2. Monoamines communication). Acetylcholine (ACh) – Essential for nerve-to-muscle Hormones function like a radio broadcast (widespread, slower communication and memory. effects). Serotonin (5-HT) – Regulates mood, emotional states, hunger, and sleep. The Stress Hypothesis Dopamine (DA) – Involved in pleasure,reinforcement learning, and Focuses on overactivity in the motor control. Hypothalamic-Pituitary-Adrenal (HPA) Axis leading to excessive Epinephrine (Adrenaline) – Triggers the stress hormones (cortisol). fight or flight response. Chronic stress can cause immune suppression, digestive Norepinephrine (Noradrenaline) – Works with epinephrine in the issues, heart disease, and mental health disorders (anxiety, fight or flight response, also involved in attention and arousal. depression). 3. Neuropeptides (Neuromodulators) Dysregulation – in some individuals, particularly those with anxiety, Endorphins – Reduce pain perception and enhance well-being. depression, or trauma-related disorders, the feedback mechanisms Substance P – Involved in pain transmission. may be impaired, leading to persistent stress hormone production Oxytocin – Affects reproduction, social bonding, and childbirth; and maladaptive responses to stress. often called the "love hormone." 4. Purines - – purines, like adenosine and ATP, function as HPA Axis & Stress Response neurotransmitters by modulating neural activity, particularly in 1. Initial Reaction: sleep-wake cycles, arousal, and energy metabolism. Stress activates the sympathetic nervous system → adrenal l Adenosine – Inhibits neural activity, promotes sleep, and dilates medulla releases epinephrine & norepinephrine → triggers fight or blood vessels. flight. ATP (Adenosine Triphosphate) – Acts as an excitatory 2. Secondary Reaction (HPA Activation): o Hypothalamus releases neurotransmitter, involved in energy transfer and synaptic signaling. Corticotropin-Releasing Hormone (CRH) → stimulates the pituitary gland. Biological Implications of Neurotransmitters 3. Hormone Release: Serotonin plays a major role in mood disorders. Pituitary Gland releases Adrenocorticotropic Hormone (ACTH) into the bloodstream. Permissive Hypothesis: When serotonin is low, other 4. Cortisol Production: neurotransmitters fluctuate more, leading to mood instability. ACTH binds to receptors in the adrenal cortex, leading to cortisol Monoamine Hypothesis: Imbalances in serotonin, dopamine, and release. norepinephrine contribute to disorders like depression and anxiety. 5. Regulation: High cortisol levels trigger a negative feedback loop, signaling the hypothalamus & pituitary gland to stop CRH and ACTH production → Homeostasis is restored. NEUROTRA FUNCTION EXCESS DEFICIENCY NSMITTER LEADS TO LEADS TO HPA Axis Dysfunction & Chronic Stress ​ Prolonged stress keeps the HPA axis overactivated, Acetylcholine muscle muscle alzheimer’s causing: action, spasms disease, learning parkinson’s ​ Elevated cortisol levels (linked to anxiety, depression, memory disease PTSD). ​ Weakened cortisol response to acute stress (body Dopamine pleasure, schizophrenia parkinson’s struggles to return to normal). learning, , addiction disease, Key Takeaways emotion anxiety, Neurotransmitters - Fast-acting, direct depression messengers for nerve communication. Hormones: Slow-acting, widespread Serotonin mood, sleep, ADHD anxiety, mood messengers regulating bodily functions. appetite disorders Imbalances in neurotransmitters & hormones contribute to mental health disorders. Norepinephri fight or flight anxiety depression Chronic stress disrupts the HPA axis, causing prolonged high ne response cortisol levels and associated health problems. GABA inhibits sleep/eating anxiety, 3.1 overactivy disorder tremors, Structure of the Nervous System insomia 1. Nervous System Overview Central Nervous System (CNS) – Composed of the brain and Glutamate excitatory migraines, spinal cord. signaling seizures, Peripheral Nervous System (PNS) – Connects the CNS to the rest manic episodes of the body. Somatic Nervous System (SNS) – Controls voluntary movements and sensory input. Hormones & Endocrine System Definition & Function Autonomic Nervous System (ANS) – Regulates involuntary functions. Endocrine System - Most attention has shifted away from ▪ Sympathetic NS – "Fight-or-flight" a focus on neurotransmitters to the endocrine system and (increases heart rate, breathing). ▪ Parasympathetic NS – → Third ventricle → Fourth ventricle. "Rest-and-digest" (slows heart rate, digestion). CSF (Cerebrospinal Fluid) – Cushions and supports the brain. Hydrocephalus – Condition where excessive CSF leads to brain 2. Spinal Cord & Its Components swelling. Communicates with the body via sensory and motor nerves. Dorsal Root Ganglia – Clusters of sensory neuron cell bodies outside the spinal cord. Gray Matter – "H-shaped" region with neuron cell bodies & BRAIN REGION FUNCTION dendrites. White Matter – Myelinated axons that send signals throughout the Medulla Controls breathing, heart rate, reflexes CNS. AUTONOMIC NERVOUS SYSTEM Pons Connects hemispheres, controls motor functions SYMPATHETIC NERVOUS SYSTEM A network of nerves that prepare the organs for a burst of vigorous activity. Sympathetic axons prepare the organs for “fight or flight,” Cerebellum Coordinates movement, balance, motor learning such as by increasing breathing and heart rate and decreasing digestive activity. Tectum processes visual and auditory Releases norepinephrine information PARASYMPATHETIC NERVOUS SYSTEM The “rest and digest” system, facilitates vegetative, non emergency Substantia Nigra produces dopamine, controls responses. Its function is generally the opposite of sympathetic movement activities. Releases acetylcholine. Thalamus sensory relay station 3. Major Brain Divisions Basal Ganglia controls movement, motivation, The brain consists of three main parts: and habits 1. Hindbrain – Medulla, Pons, Cerebellum. 2. Midbrain – Tectum, Tegmentum, Colliculi, Substantia Nigra. Limbic System regulates emotion, memory, 3. Forebrain – Cerebral Cortex, Thalamus, Basal Ganglia, Limbic and motivation System. 4. Hindbrain (Basic Life Functions) Hypothalamus regulates hormones, hunger, Medulla and temperature Controls involuntary functions like breathing, heart rate, and reflexes. Hippocampus essential for memory and Communicates with the body via 12 pairs of cranial nerves. spatial navigation Pons Bridges the two brain hemispheres and allows cross-body control: Left brain → Right body Right brain → Left body Key Takeaways Cerebellum The nervous system is divided into the CNS (brain & spinal Coordinates movement, balance, and cord) and PNS (nerves). timing. The hindbrain controls basic survival functions. Damage affects motor control and The midbrain is responsible for sensory rhythm perception. processing and movement. 5. Midbrain (Relay & Sensory Processing) The forebrain handles higher cognitive Tectum – The "roof" of the midbrain. functions, emotions, and voluntary Superior Colliculus – Vision processing. actions. Inferior Colliculus – Auditory processing. The limbic system plays a role in Tegmentum – Contains motor pathways. emotions, memory, and motivation. Substantia Nigra – Produces dopamine (essential for movement). CSF protects and nourishes the brain, Damage → Parkinson’s disease. but excessive buildup can cause 6. Forebrain (Cognition & Emotions) hydrocephalus. Cerebral Cortex – Outer layer of the brain, responsible for: thinking, The 12 cranial nerves control sensory decision-making, problem-solving. and motor functions, including vision, hearing, swallowing, and Thalamus – Sensory relay station (except for smell). heart rate. Basal Ganglia – Controls movement, motivation, habits. 7. Limbic System (Emotions & Memory) 3.2 Amygdala – Processes fear and emotional responses. The Parts of the Cerebral Cortex Hypothalamus – Regulates hunger, thirst, temperature, hormones. 1. Overview of the Cerebral Cortex Pituitary Gland – Produces hormones affecting stress, growth, The cerebral cortex is the outermost metabolism. layer of the brain, responsible for higher mental functions such as Hippocampus – Essential for memory formation and spatial perception, thinking, and decision- making. navigation. Though only a few millimeters thick, it accounts for nearly half the 8. Cranial Nerves (12 Pairs) brain's weight. The 12 cranial nerves originate from the brainstem and control The folds and wrinkles (gyri and sulci) increase its surface area, various sensory and motor functions. allowing more neurons to process vast amounts of information. 9. The Ventricles & Cerebrospinal Fluid (CSF) The cortex consists of gray matter, composed mainly of neurons, Ventricles – Four interconnected, fluid- filled cavities in the brain. lacking the myelin insulation found in white matter. Lateral ventricles (left & right) 2. The Four Lobes of the Cerebral Cortex o Walter Freeman, a doctor with no surgical training, performed A. Occipital Lobe (Vision) crude lobotomies using tools like ice picks and electric drills. Location - At the back of the brain. o Lobotomies fell out of favor in the 1950s with the introduction of Function - Processes visual information,including: psychiatric medications. Mapping the visual world (spatial reasoning, visual memory). Recognizing faces and objects. Damage to the Occipital Lobe: Can cause blindness or visual impairments (e.g., blind spots). Right hemisphere damage → left visual field blindness. Lobe Main Functions Damage can Cause B. Parietal Lobe (Touch & Spatial Processing) Occipital Lobe Visual processing, Blindness, Virtual Location - Between the occipital lobe and the central sulcus. recognizing faces, Distortions Function - spatial reasoning Processes sensory input from touch, muscle stretch, and joint receptors. Parietal Lobe Touch, body Sensory loss, Primary Somatosensory Cortex (Postcentral Gyrus): awareness, spatial difficulty with ▪ Contains four bands of cells that receive simultaneous sensory coordination movement information: coordination ▪ Two bands → light touch. ▪ One band → deep pressure. Temporal Lobe Hearing, langage, Language ▪ One band → combination of both. comprehension, disorders, memory Helps with spatial awareness and body coordination. memory loss, emotional disturbances C. Temporal Lobe (Hearing, Language, & Memory) Location - On the sides of the brain, near the temples. Frontal Lobe Decision-making, Impulsivity, poor Functions: planning, motor judgement, speech control, personality and movement Primary Auditory Cortex – issues Processes sound information. Language Comprehension & Production. Prefrontal Cortex Complex thinking, Lack of foresight, Memory Formation & Learning (verbal & visual memory). personality, impulsivity, Plays a role in emotion and motivation. executive personality Disorders Related to Temporal Lobe functioning changes Damage: Klüver - Bucy Syndrome (KBS): ~ Rare disorder causing memory loss and behavioral problems. Key Takeaways ~ Some patients may develop compulsive eating habits or The cerebral cortex is the outermost layer of the brain and is hypersexuality. responsible for higher cognitive functions. Severe Damage: May lead to seizures and dementia. It consists of four major lobes: o Occipital Lobe → Vision processing. D. Frontal Lobe (Thinking, Planning, & Movement) o Parietal Lobe → Sensory input and spatial awareness. Location - At the front of the brain, behind the forehead. o Temporal Lobe → Hearing, language, and memory. Functions: o Frontal Lobe → Thinking, decision-making, and movement. o Behavioral control & impulse inhibition. The prefrontal cortex is the last brain area to mature and is crucial o Decision-making & abstract reasoning. for decision-making, personality, and impulse control. o Attention & working memory. Lobotomies were historically used to treat mental illnesses but o Executive functioning (e.g.,multitasking, organization). became obsolete after the introduction of psychiatric medications. o Motor control (including speech and facial movements). 3. The Prefrontal Cortex (Decision-Making & Personality) The prefrontal cortex develops last and is responsible for complex cognition. Functions: o Planning & problem-solving. o Personality & social behavior. o Decision-making & risk assessment. o Orchestration of thoughts and actions based on internal goals. Damage to the Prefrontal Cortex: o Impaired delayed - response tasks (remembering and responding to information after a pause). o Impulsive decision-making due to inability to assess long-term consequences. 4. Prefrontal Lobotomy (Historical Medical Practice) What is a Prefrontal Lobotomy? o A surgical procedure that damaged or cut connections in the prefrontal cortex to alter behavior. o Used in the early-to-mid 20th century to treat mental illnesses like schizophrenia and severe mood disorders. Walter Freeman & the Lobotomy Procedure: