Physiological/Biological Psychology Chapter 1-3 PDF

**PHYSIOLOGICAL/BIOLOGICAL PSYCHOLOGY\ ** **What is Physiology?\ ** - It is the scientific study of functions and mechanisms in a living system. It focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out chemical and physical functions in a livin...

**PHYSIOLOGICAL/BIOLOGICAL PSYCHOLOGY\ ** **What is Physiology?\ ** - It is the scientific study of functions and mechanisms in a living system. It focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out chemical and physical functions in a living system. **What is Psychology?\ ** - It is the study of mind and behavior. Its subject matter includes the behavior of humans and nonhumans, both conscious and unconscious phenomena, and mental processes such as thoughts, feelings, and motives. **What is Physiological Psychology?\ ** - It investigates human behavior, emotion, thoughts, perception, learning memory and all other elements of psychology in terms of biological structures (different regions of the brain) and physiological processes **PHYSIOLOGICAL/BIOLOGICAL PSYCHOLOGY\ ** - Physiological psychology (also known as biological psychology or behavioral neuroscience) is a branch of psychology that studies the relationship between the brain, nervous system and behavior. It focuses on\ how physiological processes-such as neural activity, brain structure, neurotransmitters, and hormones-affect mental processes and behavior. **What is the role of Physiological Psychologists?\ ** - They investigate how different brain regions are involved in functions like perception, learning, memory, emotion and movement. They also explore how changes in brain chemistry and physiology can influence psychological\ states, such as mood, motivation and mental health conditions. **Key areas of interest in Physiological Psychology include:** - **Neuroanatomy:** The study of the structure of the brain and nervous system. - **Neurochemistry:** Examines the chemical processes within the brain, including neurotransmitters and hormones. - **Neurophysiology:** Focuses on the functioning of neurons and how they communicate. - **Behavioral Neuroscience:** Looks at how brain function relates to behavior and cognitive processes. **WHY IS IT IMPORTANT IN PSYCHOLOGY?\ ** 1. Psychology studies the behavior of an individual. 2. The behavior of an individual is governed by the changes in the body. 3. The changes in the body are profoundly affected by the main provider of information throughout the body which is the brain. 4. The subject is important to be able to understand how small changes in the brain relates to the differences in the actions of an individual more precisely in the person's behavior. **IMPORTANCE\ ** - Physiological psychology is crucial in the broader field of psychology for several reasons: **REASONS:\ ** - **Understanding Biological Basis of Behavior:** It provides insights into how brain structures and functions underpin behaviors, emotions, and cognitive processes. This helps in comprehending why certain behaviors occur and how mental states are linked to physiological processes. - **Advancing Mental Health Treatment: **By understanding the biological mechanisms behind mental health conditions (such as depression, anxiety, or schizophrenia), physiological psychology can contribute to developing more effective treatments and interventions. For instance, it helps in identifying how neurotransmitter imbalances affect mood and cognition, guiding the development of pharmacological treatments. - **Informing Neuroscience Research: **It bridges the gap between psychology and neuroscience, contributing to our knowledge of how different brain regions are involved in various psychological functions. This interdisciplinary approach enhances our understanding of brain function and its relationship with behavior. - **Enhancing Educational and Cognitive Strategies:** Insights from physiological psychology can inform educational practices and cognitive training by revealing how brain development and function affect learning and memory. For example, understanding how stress impacts cognitive performance can lead to better strategies for managing academic pressures. - **Contributing to Basic Science Knowledge:** It enriches our fundamental understanding of how biological processes such as neuroplasticity (the brain\'s ability to reorganize itself) and hormonal changes influence behavior and cognition. This basic knowledge is essential for advancing both theoretical and applied psychology. - **Guiding Rehabilitation and Recovery:** In clinical settings, knowledge from physiological psychology helps in designing rehabilitation programs for individuals with brain injuries or neurological disorders. Understanding the brain\'s capacity for recovery and adaptation informs therapeutic practices. **BIOLOGICAL EXPLANATIONS OF BEHAVIOR\ ** - Biological explanations of behavior fall into four categories: *physiological,* *ontogenetic, evolutionary,* and *functional* (Tinbergen, 1951). **THE FOUR CATEGORIES:\ \ Physiological Explanation\ ** - relates a behavior to the activity of the brain and other organs. It deals with the machinery of the body---for example, the chemical reactions that enable hormones to influence brain activity and the routes by which brain activity controls muscle contractions. **Ontogenetic Explanation\ ** - describes how a structure or behavior develops, including the influences of genes, nutrition, experiences, and their interactions. **For example, males and** **females differ on average in several** **ways. Some of those differences can** **be traced to the effects of genes or** **prenatal hormones, some relate to** **cultural influences, many relate** **partly to both, and some await** **further research.\ ** - **ONTOGENETIC\ ** - \"**Ontogenetic**\" refers to the development and changes that occur in an individual organism over its lifespan, from conception through to maturity and aging. This term is used in various fields such as biology, psychology, and developmental science to describe the process of growth and development of an organism. **Here are Key Aspects of Ontogeny:\ ** 1. **Developmental Stages** - includes the prenatal and postnatal development 2. **Physical Growth** - Refers to changes in size, shape, and function of the body. This includes the development of motor skills, sensory systems, and physical health. 3. **Cognitive and Emotional Development** - intellectual abilities and emotions 4. **Behavioral Changes** - learning, socialization, and adaptation to environmental demands. 5. **Genetic and Environmental** **Influences** - heredity and environmental factors (experiences, culture, and up bringing) **Evolutionary Explanation\ ** - An evolutionary explanation reconstructs the evolutionary history of a structure or behavior. It aims to understand how a particular structure or behavior in an organism evolved over time. This approach reconstructs the evolutionary history by examining how traits or behaviors have developed, adapted, and changed through different stages of evolutionary history. **Functional Explanation\ ** - A functional explanation describes why a structure or behavior evolved as it did. It provides insight into the adaptive reasons behind a trait or behavior, Example: In most bird species, only the male sings. He sings only during the reproductive season and only in his territory. The functions of the song are to attract females and warn away other males. **CAREER OPPORTUNITIES\ \ ** ** ** **THE USE OF ANIMALS IN RESEARCH** - Animals are used in many kinds of research studies, some dealing with behavior and others with the functions of the nervous system. - Given that most biological psychologists and neuroscientists are primarily interested in the human brain and human behavior, why do they study nonhumans? Here are four reasons: 1. **The underlying mechanisms of behavior are similar across species and sometimes easier to study in a nonhuman species.\ ** - The brains and behavior of nonhuman vertebrates resemble those of humans in their chemistry and anatomy, but are smaller and easier to study 2. **We are interested in animals for their own sake.\ ** - Humans are naturally curious. We would love to know about life, if any, elsewhere in the universe, regardless of whether that knowledge might be useful. Similarly, we would like to understand how bats chase insects in the dark, how migratory birds find their way over unfamiliar territory, and how schools of fish manage to swim in unison. **How bats chase insects in the dark?** - Bats chase insects in the dark using echolocation, a highly effective biological sonar system. By emitting high-frequency sound waves and listening to the returning echoes, bats can detect, locate, and capture insects even in complete darkness. This ability allows them to thrive in nocturnal environments where visual cues are limited or nonexistent. **How migratory birds find their way over unfamiliar territory?** - migratory birds navigate over unfamiliar territory through a sophisticated interplay of celestial cues (sun and stars), magnetic fields, visual landmarks, olfactory signals, social learning, and internal biological rhythms. These mechanisms allow them to traverse vast distances and reach their destinations with remarkable accuracy, despite the challenges of unfamiliar landscapes and changing conditions. **How schools of fish manage to swim in unison?** - Schools of fish manage to swim in unison through a combination of sensory feedback, behavioral synchronization, and hydrodynamic interactions. Their ability to follow simple rules, use sensory cues, and maintain group cohesion allows them to move as a single, coordinated unit, offering benefits such as predator evasion and improved energy efficiency. This remarkable coordination is a result of evolutionary pressures and adaptations that enhance their survival in complex aquatic environments. 3. **What we learn about animals' sheds light on human evolution\ ** - By examining the lives, behaviors, and genetics of animals, researchers can piece together the complex puzzle of human evolution, shedding light on how we came to be the species we are today. 4. **Legal or ethical restrictions prevent certain kinds of research on humans.\ ** - For example, investigators insert electrodes into the brains of rats and other animals to determine the relationship between brain activity and behavior. They also inject chemicals, extract brain chemicals, and study the effects of brain damage. Such experiments answer questions that investigators cannot address in any other way, including some questions that are critical for medical progress. **THE CELLS OF THE NERVOUS SYSTEM\ ** - **Neurons and glia** are two fundamental types of cells in the nervous system, each playing distinct yet complementary roles in brain function. **Neurons\ ** - **Function:** Neurons are the primary cells responsible for transmitting information throughout the nervous system. They communicate via electrical impulses and chemical signals. - Structure: A typical neuron has three main parts: - **[Cell Body (Soma)]**: Contains the nucleus and other organelles, responsible for maintaining the cell\'s health. - **[Dendrites:]** Branch-like structures that receive signals from other neurons. - **[Axon]:** A long, thin projection that transmits signals away from the cell body to other neurons, muscles, or glands. The axon can be covered by a myelin sheath, which speeds up signal transmission. - Types: Neurons are classified based on their function (sensory, motor, interneurons) or structure (unipolar, bipolar, multipolar). **PARTS OF A NEURON:\ ** **DENDRITES** -- Receive signals from other neuron cells.\ **CELL BODY** -- Contains the cell nucleus.\ **NUCLEUS** -- Contains the genetic material (chromosomes) of the neuron cell.\ **AXON** -- Conducts electrical impulses along the neuron cell.\ **MYELIN SHEATH** - Insulates the axon to help protect the neuron cell & speed up transmission of electrical impulses.\ **AXON TERMINAL** - Transmits electrical & chemical signals to other neuron cells & effector cells **\ Types of Neurons According to Structure\ ** **\ Glia (Glial Cells)\ ** - **Function:** Glial cells support and protect neurons. They do not transmit signals like neurons but are essential for overall nervous system health and function. - **Types of Glial Cells:** - **Astrocytes:** Star-shaped cells that provide structural support, regulate the blood-brain barrier, and maintain the chemical environment for neurons. - **Oligodendrocytes (in the CNS) and Schwann Cells (in the PNS):** Produce the myelin sheath that insulates axons, enabling faster signal transmission. - **Microglia: **Act as the brain\'s immune cells, removing waste and protecting against pathogens. - **Ependymal Cells:** Line the ventricles of the brain and spinal cord, helping produce and circulate cerebrospinal fluid.   - The adult human brain contains approximately **[86 billion neurons]** (Herculano-Houzel, Catania, Manger, & Kaas, 2015). The exact number varies from person to person. - We now take it for granted that the brain is composed of individual cells, but the idea was doubtful as recently as the early 1900s. Until then, the best microscopic views revealed little detail about the brain. Observers noted long, thin fibers between one cell body and another, but they could not see whether a fiber merged into the next cell or stopped before it. In the **[late 1800s]**, **Santiago Ramón y Cajal **used\ newly developed staining techniques to show that a small gap separates the tip of a neuron's\ fiber from the surface of the next neuron. The brain, like the rest of the body, consists of individual cells. **Santiago Ramón y Cajal a Pioneer of Neuroscience (1852--1934)** - He was a Spanish physician and scientist considered to be the founder of modern neurobiology. He was the first to report with precision the fine anatomy of the nervous system. His findings were central in the elaboration of the neuron doctrine. - Cajal demonstrated that the nervous system was made up of individual cells (neurons, term coined by Waldeyer) connected to each other by small contact zones (synapses, term coined by Sherrington). The 3 anatomical structures previously described as separate by Deiters --- the cell body, the axis cylinder (the axon)\ and the protoplasmic processes (dendritic arborizations)--- were actually all part of an individual nerve cell. **THE STRUCTURE OF A NEURON** - A **motor neuron**, with its soma in the spinal cord, receives excitation through its dendrites and conducts impulses along its axon to a muscle. - A **sensory neuron** is specialized at one end to be highly sensitive to a particular type of stimulation, such as light, sound, or touch. - **Dendrites** are branching fibers that get narrower near their ends. (The term dendrite comes from a Greek root word meaning "tree." A dendrite branches like a tree.) The dendrite's surface is lined with specialized synaptic receptors, at which the dendrite receives information from other neurons. - The greater the surface area of a dendrite, the more information it can receive. Many dendrites contain dendritic spines, short outgrowths that increase the surface area available for synapses - The cell body, or soma (Greek for "body"; plural: somata), contains the nucleus, ribosomes, and mitochondria. Most of a neuron's metabolic work occurs here. Cell bodies of neurons range in diameter from 0.005 millimeter (mm) to 0.1 mm in mammals and up to a millimeter in certain invertebrates. In many neurons, the cell body is like the dendrites--- covered with synapses on its surface. - The **axon** is a thin fiber of constant diameter. (The term axon comes from a Greek word meaning "axis.") The axon conveys an impulse toward other neurons, an organ, or a muscle. Axons can be more than a meter in length, as in the case of axons from your spinal cord to your feet. The length of an axon is enormous in comparison to its width, and in comparison, to the length of dendrites.  **OTHER TERMS ASSOCIATED WITH NEURONS\ ** Other terms associated with neurons are afferent, efferent, and intrinsic. - An [**afferent** **axon**] brings information into a structure. - An [**efferent** **axon** ]carries information away from a structure. - If a cell's dendrites and axon are entirely contained within a single structure, the cell is an interneuron or intrinsic neuron of that structure. For example, an intrinsic neuron of the thalamus has its axon and all its dendrites within the thalamus  **NOTES**: Every sensory neuron is an afferent to the rest of the nervous system, and every motor neuron is an efferent from the nervous system. Within the nervous system, a given neuron is an efferent from one structure and an afferent to another.\ \ **THE BLOOD - BRAIN BARRIER** - Although the brain, like any other organ, needs to receive nutrients from the blood, many chemicals cannot cross from the blood to the brain (Hagenbuch, Gao, & Meier, 2002). The mechanism that excludes most chemicals from the vertebrate brain is known as **the blood--brain barrier.\ ** - The blood-brain barrier (BBB) is essential for several reasons, primarily related to the protection and maintenance of the brain\'s highly sensitive environment. Here\'s why the BBB is crucial: 1\. **Protection from Harmful Substances** - **Toxins and Pathogens:** The BBB prevents potentially harmful substances in the blood, such as toxins, bacteria, and viruses, from entering the brain tissue. The brain is particularly vulnerable to damage because neurons, once damaged, often cannot regenerate. The BBB acts as a defensive shield, ensuring that only certain molecules can pass through. - **Blood-Borne Chemicals:** Many chemicals circulating in the blood could disrupt brain function if they reached the brain. The BBB restricts these chemicals, maintaining the brain\'s chemical stability. 2\. **Regulation of the Brain\'s Microenvironment\ ** **Homeostasis:** Neurons in the brain require a very stable environment to function correctly. Fluctuations in ion concentrations, pH levels, and other factors can impair neuronal activity. The BBB tightly regulates the passage of ions, nutrients, and other substances to maintain this stability, ensuring optimal conditions for nerve signal transmission. - **Controlled Nutrient Supply:** The BBB allows essential nutrients like glucose and amino acids to enter the brain through specialized transport mechanisms, while preventing potentially harmful substances from crossing. This ensures that the brain gets the nutrients it needs without being exposed to harmful substances. 3\. **Prevention of Neurotoxicity** - **Blood-Borne Neurotoxins:** Certain substances in the blood, even those that are harmless elsewhere in the body, can be toxic to the brain. The BBB helps prevent these substances from entering the brain, protecting neurons from damage. - **Immune Response Modulation:** While the immune system protects the body from infections, an uncontrolled immune response can be harmful. The BBB regulates the entry of immune cells and antibodies into the brain, preventing excessive inflammation that could damage neural tissue. 4\. **Isolation of Neurotransmitter Systems\ ** - **Separation from Peripheral Neurotransmitters:** Neurotransmitters like adrenaline and serotonin are present in both the brain and the peripheral nervous system. The BBB prevents peripheral neurotransmitters from affecting brain function, ensuring that neurotransmitter signaling within the brain remains precisely regulated. 5\. **Facilitation of Brain Function and Cognitive Processes\ ** - **Neuronal Sensitivity: **Neurons are extremely sensitive to changes in their environment. The BBB ensures that these cells are not exposed to fluctuations in the blood\'s composition, which could disrupt cognitive processes such as memory, learning, and decision-making. 6\. **Minimization of Immune System Interaction** - **Protection from Autoimmunity:** The brain is considered an \"immune-privileged\" site, meaning that the immune system\'s access to the brain is limited. The BBB helps maintain this status, reducing the risk of autoimmune attacks on brain tissue. - In summary, the blood-brain barrier is vital for protecting the brain from external threats, maintaining a stable environment for neural function, and ensuring that the brain operates efficiently and safely. Without the BBB, the brain would be vulnerable to a wide range of dangers that could impair its ability to function properly.  **NOURISHMENT OF VERTEBRATE NEURONS\ ** - Most cells use a variety of carbohydrates and fats for nutrition, but vertebrate neurons depend almost entirely on **glucose**, a sugar. - For certain other chemicals, the brain uses **active** **transport**, a protein-mediated process that expends energy to pump chemicals from the blood into the brain. Chemicals that are actively transported into the brain include glucose (the brain's main fuel), amino acids (the building blocks of proteins), purines, choline, a few vitamins, and iron (Abbott, Rönnback, & Hansson, 2006; Jones & Shusta, 2007). Insulin and probably certain other hormones also cross the blood--brain barrier, at least in small amounts, although the mechanism is not yet known (Gray, Meijer, & Barrett, 2014; McNay, 2014) **The Nerve Impulse** - A nerve impulse, also known as an action potential, is an electrical signal that travels along the axon of a neuron, enabling communication between neurons and other cells, such as muscles or glands. - A nerve impulse is like a quick electrical message that moves along a neuron's long, skinny part (called the axon). This message helps neurons talk to each other and also to muscles and glands. - The cell membrane keeps a difference in electrical charge between the inside and outside of the cell. This difference is called polarization. Inside the cell, it\'s a bit more negative compared to the outside. This happens because there are negatively charged proteins inside. This voltage difference is known as the resting potential. - All parts of a neuron are covered by a membrane about **8 nanometers (nm) thick**. That is about one ten-thousandth the width of an average human hair. The membrane is composed of two layers (free to float relative to each other) of phospholipid molecules (containing chains of fatty acids and a phosphate group). Embedded among the phospholipids are cylindrical protein molecules through which certain chemicals can pass. - When at rest, the membrane maintains an electrical gradient, also known as **polarization**---a difference in electrical charge between the inside and outside of the cell. The electrical potential inside the membrane is slightly negative with respect to the outside, mainly because of negatively charged proteins inside the cell. This difference in voltage is called the **resting** **potential.\ ** - Here is the illustration showing the series of events involved in the transmission of a nerve impulse along a neuron. The image depicts the stages of resting membrane potential, depolarization, propagation of the action potential, repolarization, return to resting state, and saltatory conduction in a myelinated axon.  **\ ** 1. **Resting Membrane Potential\ ** 1. **Polarization**: At rest, a neuron has a negative electrical charge inside its membrane compared to the outside, typically around -70 millivolts (mV). This difference in charge is called the resting membrane potential. 1. **Ion Distribution**: The resting membrane potential is maintained by the distribution of ions across the neuron\'s membrane, particularly sodium (Na⁺) and potassium (K⁺) ions. *[There are more Na⁺ ions outside the cell and more K⁺ ions inside the cell.]* 1. **Sodium-Potassium Pump**: This pump actively transports 3 Na⁺ ions out of the neuron and 2 K⁺ ions into the neuron, using energy from ATP. This action maintains the concentration gradients of Na⁺ and K⁺ and contributes to the negative charge inside the cell. **The Sodium and Potassium Gradient for a resting membrane**  **2. Generation of an Action Potential\ ** - Depolarization: When a neuron is stimulated by a signal (e.g., from another neuron or a sensory input), voltage-gated Na⁺ channels open, allowing Na⁺ ions to rush into the cell. This influx of positive ions causes the membrane potential to become less negative, or depolarize. If the depolarization reaches a certain threshold (around -55 mV), an action potential is triggered. - Rapid Depolarization: Once the threshold is reached, more Na⁺ channels open, leading to a rapid influx of Na⁺ and a further increase in the membrane potential, typically reaching around +30 to +40 mV. **3. Propagation of the Action Potential** - All-or-None Principle: The action potential follows an all-or-none principle, meaning that once the threshold is reached, the action potential will occur fully and propagate along the entire length of the axon. - Local Current Flow: As the action potential occurs at one point on the axon, it generates a local current that depolarizes the adjacent section of the membrane, triggering an action potential in that section. This process continues along the length of the axon, propagating the nerve impulse. **Propagation of an Action Potential\ ** **4. Repolarization** - Closing of Na⁺ Channels: After the peak of the action potential, Na⁺ channels close, and voltage-gated K⁺ channels open. - K⁺ Efflux: K⁺ ions flow out of the neuron, causing the membrane potential to return to a negative value, a process called repolarization. - Hyperpolarization: Sometimes, the membrane potential temporarily becomes more negative than the resting potential, known as hyperpolarization, because K⁺ channels close slowly, allowing more K⁺ to leave the cell. **5. Return to Resting State\ ** - Restoration of Ion Balance: After the action potential, the sodium-potassium pump and other ion channels restore the original distribution of Na⁺ and K⁺, returning the neuron to its resting membrane potential. - Refractory Period: During this period, the neuron is temporarily unable to generate another action potential. There are two phases: - Absolute Refractory Period: The neuron cannot fire another action potential, no matter how strong the stimulus. - Relative Refractory Period: A stronger-than-normal stimulus is required to generate another action potential. **6. Saltatory Conduction (in Myelinated Neurons)\ ** - Myelin Sheath: In myelinated neurons, the axon is covered by a myelin sheath, which acts as an insulator and speeds up the conduction of the nerve impulse. - Nodes of Ranvier: The myelin sheath is interrupted at intervals by gaps called nodes of Ranvier. The action potential \"jumps\" from node to node, a process called saltatory conduction, which is much faster than the continuous conduction in unmyelinated axons. **7. Synaptic Transmission\ ** - Reaching the Axon Terminal: When the action potential reaches the end of the axon (axon terminal), it triggers the release of neurotransmitters from synaptic vesicles into the synaptic cleft (the gap between neurons). - Communication with the Next Cell: These neurotransmitters cross the synaptic cleft and bind to receptors on the postsynaptic cell (another neuron, muscle cell, or gland), initiating a response in the next cell and continuing the communication process. **SYNAPSES\ ** - Synapses connect neurons in the brain to neurons in the rest of the body and from those neurons to the muscles. - Synapses are the crucial junctions where communication occurs between neurons or between a neuron and another type of cell, such as a muscle or gland cell. This communication is essential for all nervous system functions, including movement, sensation, thought, and emotion. **1. Type of Synapse\ ** A. **Chemical synapse:** 1. A chemical synapse involves chemical neurotransmitters (chemical messengers) such as acetylcholine by the axon terminal of a presynaptic neuron. 2. The chemical messengers released in a synaptic cleft move towards the receptor located at the dendrite of a postsynaptic neuron. B**. Electrical synapse:\ ** 1. Electrical synapse involves the transfer of nerve impulses via ions and small metabolites. 2. Electrical synapses are composed of gap junctions (intracellular aggregates permitting the direct cell to cell transfer). 3. It generates an action potential to be transferred further. **So, in summary:** - Chemical synapses use chemical messengers to send signals, with a little delay. - Electrical synapses pass signals directly using tiny electric charges, which is much faster **Properties of Synapses** **A. Chemical Synapse:** - Imagine two neurons (nerve cells) trying to talk to each other. They don\'t\ actually touch but are separated by a tiny gap called a synaptic cleft. - When the first neuron (presynaptic neuron) wants to send a message, it\ releases special chemicals called neurotransmitters into this gap. - These neurotransmitters float across the gap and attach to specific spots\ (receptors) on the second neuron (postsynaptic neuron). - Once they attach, they pass the message along, and the second neuron\ knows what to do, like sending the message further along. **B. Electrical Synapse:** - In an electrical synapse, neurons are so close that they are almost\ directly connected through special channels called gap junctions. - These gap junctions allow tiny electric signals (like small ions) to pass\ straight from one neuron to the next, kind of like flipping a switch. - This way, the message gets passed on really fast because it doesn\'t need\ to wait for chemicals to do the job. - Found in specialized locations: - Heart - Smooth muscle - Pulp of the tooth - Retina of the eye - **Excitatory Synapses:** Increase the likelihood of the post-synaptic neuron firing an action potential (e.g., glutamate as a neurotransmitter). - These are like a \"go\" signal. They make it more likely for the next neuron to send a message forward. - **Excitatory** = Go - **Inhibitory Synapses:** Decrease the likelihood of the post-synaptic neuron firing (e.g., GABA as a neurotransmitter). - These are like a \"stop\" signal. They make it less likely for the next neuron to send a message. - **Inhibitory** = Stop **3. Plasticity** - **Short-Term Plasticity:** Changes in synaptic strength over short periods (milliseconds to\ minutes), such as facilitation or depression. - This is like a quick change in how strong a signal is between\ neurons. It lasts just a short time, like when you quickly get better at something but only for\ a little while. - **Long-Term Plasticity:** Persistent changes in synaptic strength, such as Long-Term\ Potentiation (LTP) or Long-Term Depression (LTD), which are key for learning and memory. - This is a lasting change in how strong the signal is. It's like when you\ learn something new and remember it for a long time. - **[Short-term plasticity]** is a temporary change, and **[long-term plasticit]y** is a lasting change in how\ neurons talk to each other. **How Do Synapses Change Their Strength?** When a neuron sends a signal, it goes through these three steps: 1. **Neurotransmitter Release:** The first neuron releases chemical messengers (neurotransmitters) into the gap between neurons. 2. **Binding to Receptors: **These neurotransmitters then attach to special spots (receptors) on the next neuron. 3. **Opening Ion Channels:** This attachment opens tiny doors (ion channels) in the second neuron, letting*\ *electrical signals pass through. **Changing Synaptic Strength:** Synapses can become stronger or weaker by adjusting two things: 1. **Amount of Neurotransmitter Released: **The signal becomes stronger if more neurotransmitters are released. If less is released, the signal becomes weaker. 2. **Number of Receptors:** If there are more receptors on the second neuron, it can catch more neurotransmitters, making the signal stronger. Fewer receptors mean a weaker signal.  Both of these changes affect how much electrical current flows through the neuron, which in turn changes the strength of the signal between the two neurons. This process is how synapses adjust and adapt, making the brain more flexible and capable of learning. **4. Synaptic Transmission** - **Presynaptic Mechanisms: **Involves neurotransmitter release from vesicles, modulated by factors like\ calcium concentration and vesicle availability. - **Postsynaptic Mechanisms: **Involves receptor binding and subsequent cellular responses, such as ion\ channel opening or second messenger cascades. **Synaptic Transmission:** - **Presynaptic Mechanisms:** This is what happens in the first neuron. It releases tiny chemicals\ (neurotransmitters) from little storage bubbles (vesicles) into the gap between neurons. The release is\ controlled by things like how much calcium is around and how many of those storage bubbles are\ available. - **Postsynaptic Mechanisms:** This is what happens in the second neuron. The released chemicals\ (neurotransmitters) stick to specific spots (receptors) on the second neuron. When they stick, it causes\ changes in the cell, like opening tiny doors (ion channels) or starting other processes inside the cell. - So, the first neuron sends the message, and the second neuron receives it and reacts. **In a clearer view:\ ** 1. **A Nerve Signal Arrives**: The neuron gets a message and gets ready to pass it on. 2. **Calcium Channels Open**: Little doors in the neuron open, letting calcium ions rush in. 3. **Neurotransmitters Are Released**: The calcium causes tiny bubbles (vesicles) full of neurotransmitters to move to the edge of the neuron and pop, releasing the neurotransmitters into the gap between neurons (the synaptic cleft). 4. **Neurotransmitters Bind to Receptors:** These neurotransmitters float across the gap and attach to special spots (receptors) on the next neuron. 5. **Ion Channels Open:** When the neurotransmitters bind, they open more tiny doors (ion channels) on the next neuron, allowing ions to flow in. 6. **New Signal Is Generated**: If enough ions flow in, the next neuron gets excited and sends the signal forward. - In short, the signal jumps from one neuron to the next by releasing chemicals and opening doors to pass the message along. **5. Integration** - **Temporal Summation:** Integration of multiple signals arriving at a synapse in rapid succession. This is like when one neuron sends several quick messages in a row to another neuron, and the signals add up. - **Spatial Summation:** Integration of signals arriving simultaneously from multiple synapses on the same\ neuron. This is when signals from different neurons arrive at the same time on one neuron, and those signals add up. In short: - **Temporal Summation** = Signals adding up over time. - **Spatial Summation** = Signals adding up from different places.  **6. Synaptic Delay\ ** - Time taken for a signal to be transmitted across a synapse. This is the short amount of time it takes for a signal to pass from one neuron to another across a tiny gap called a synapse. It usually takes between 0.5 and 2 milliseconds. **7. Specificity\ ** - Synaptic Specificity: Synapses form between specific neurons and at specific sites, ensuring precise communication networks within the brain. It means that neurons connect with each other in very particular ways. This ensures that messages are sent to the right places in the brain, creating precise communication networks. **The Sequence of Chemical Events at a Synapse** **\ ** 1\. The neuron synthesizes chemicals that serve as neurotransmitters. It synthesizes the smaller neurotransmitters in the axon terminals and synthesizes neuropeptides in the cell body. 2\. Action potentials travel down the axon. At the presynaptic terminal, an action potential enables calcium to enter the cell. Calcium releases neurotransmitters from the terminals and into the synaptic cleft, the space between the presynaptic and postsynaptic neurons. 3\. The released molecules diffuse across the narrow cleft, attach to receptors, and alter the activity of the postsynaptic neuron. Mechanisms vary for altering that activity. 4\. The neurotransmitter molecules separate from their receptors. 5\. The neurotransmitter molecules may be taken back into the presynaptic neuron for recycling or they may diffuse away. 6\. Some postsynaptic cells send reverse messages to control the further release of neurotransmitter by presynaptic cells.