Neurons: The Basic Elements of Behavior PDF

**CH.2** Mod.5 \-- Neurons: The Basic Elements of Behavior **[THE STRUCTURE OF A NEURON:]** **Neurons**: Basic nerve cells of the nervous system. - **Components**: - **Cell body**: Contains the nucleus with hereditary material. - **Glial cells**: Support neurons by providing nour...

**CH.2** Mod.5 \-- Neurons: The Basic Elements of Behavior **[THE STRUCTURE OF A NEURON:]** **Neurons**: Basic nerve cells of the nervous system. - **Components**: - **Cell body**: Contains the nucleus with hereditary material. - **Glial cells**: Support neurons by providing nourishment, insulation, repair, and general support. **Neuron Characteristics**: - **Communication**: Neurons communicate with other cells and transmit information across long distances. - **Direction of messages**: Messages (impulses) move in one direction. - **Electrical Impulses**: Messages are electrical in nature and move in one direction (from dendrites to axon). **Neuron Structure**: - **Dendrites**: Cluster of fibers that receive messages from other neurons. Look like tree branches. - **Axon**: Long, slim extension that carries messages to other neurons. It can be up to 3 feet long. - **Terminal buttons**: Small bulges at the end of the axon that send messages to other neurons. **Myelin Sheath**: - Protective coating around axon made of fat and protein. - **Function**: Increases the speed of electrical impulses. - **Thick myelin**: Found in axons carrying urgent information (e.g., pain messages from a hot stove). **Study alert**:Remember that dendrites detect messages from other neurons; axons carry signals away from the neuron. **[HOW NEURONS FIRE:]** **All-or-None Law** - Neurons are either **on or off**, with no in-between state. - Similar to pulling a gun trigger: neurons either fire completely or not at all. **1. Resting State** - **Negative electrical charge** inside the neuron: approximately **−70 millivolts**. - Caused by more **negatively charged ions inside** than outside the neuron. **2. Triggering an Action Potential** - A message arrives, and **positively charged ions** rush into the neuron. - The charge inside the neuron changes momentarily from **negative to positive**. - When the positive charge reaches a critical level, the neuron fires, triggering an **action potential**. **Action Potential** - Definition: **An electrical impulse** that travels along the axon. - Process: - Positive ions enter the neuron, changing the charge in the axon from **negative to positive**. - The action potential moves like a **flame along a fuse**. - After the impulse passes through a section of the axon, positive ions are **pumped out**, restoring the section\'s charge to **negative**. **Voltage Changes During Action Potential** - Normal resting charge: **−70 millivolts**. - During action potential: charge increases to **+40 millivolts**. - Afterward: charge briefly becomes more negative than the resting state before returning to normal. **3. Firing Limitations** - After firing, the neuron enters a **refractory period**: - **Absolute refractory period:** The neuron cannot fire again immediately. - **Relative refractory period:** The neuron can fire again but requires a **stronger stimulus**. **Key Points** - The **action potential** allows neurons to transmit signals. - The process is **unidirectional**: dendrites → cell body → axon → terminal buttons. - **Restoration of resting state** ensures the neuron is ready to fire again. **[Speed of transmission]** - The speed at which an action potential travels along an axon is determined by the: - Axon's size. - Thickness of the myelin sheath. - Neurons differ in terms of: - Quickness of an impulse moving along the axon. - Potential rate of firing. The intensity of a stimulus determines how much of a neuron'spotential firing rate is reached. [ **Mirror Neurons**] **Mirror neurons**: specialized neurons that fire not only when a person enacts a particular behavior but also when they simply observe another individual carrying out the same behavior. - The discovery of mirror neurons suggests that humans' capacityto imitate others may be an inborn behavior. - It also helps explain how and why humans have the capacity to understand others' intentions. **[WHERE NEURONS MEET : BRIDGING THE GAP]** - **Synapse and Neurotransmitters** - **Synapse**: Space between two neurons where the axon of the sending neuron communicates with the dendrite of the receiving neuron using chemical messages. - **Neurotransmitters**: Chemicals that carry messages across the synapse to the dendrite (or sometimes the cell body) of a receiving neuron. - **Chemical Communication** - **Inside neurons**: Messages are transmitted electrically. - **Between neurons**: Messages are transmitted chemically. - **Synaptic gap bridging**: Neurotransmitters travel from the terminal button of one neuron's axon to the receptor site of another neuron's dendrite. - **Neurotransmitter Specificity** - each neurotransmitter has a unique configuration that allows it to fit into a specific receptor site on a receiving neuron. - Successful communication happens **only if** the neurotransmitter fits precisely into the receptor site. **Study alert**: Messages [inside neurons] are transmitted in e*lectrical* form, whereas messages traveling [between neurons] travel via [chemical] means - **Types of Chemical Messages** - - - - - - - - - - **Preventing Constant Stimulation or Inhibition** - If neurotransmitters stayed in the synapse: - Receiving neurons would experience **constant stimulation** or **constant inhibition**. - This would make effective communication impossible. - **Solution**: - **Enzymes deactivate** the neurotransmitters. - **Reuptake**: Terminal button reabsorbs neurotransmitters for recycling. - **Reuptake** - Process where neurotransmitters are reabsorbed by the terminal button, like a vacuum cleaner sucking up dust. - Prevents synaptic clogging and allows the neuron to reuse neurotransmitters. - Happens in milliseconds. - **SSRIs and Psychological Disorders** - **SSRIs (Selective Serotonin Reuptake Inhibitors)**: - Delay the reuptake of serotonin neurotransmitters, keeping them active longer in the synapse. - Help reduce depression symptoms. - Understanding the reuptake process has led to the development of effective treatments for psychological disorders.  **[MAJOR NEUROTRANSMITTERS:]**  **[APPROFONDIMENTI]**.A Health-Care Provider How might your understanding of the nervous system help you explain the symptoms of Parkinson's disease to a patient with the disorder? As a health-care provider, understanding the nervous system is essential to explaining **Parkinson's disease (PD)** to a patient. Here\'s how this knowledge can help you explain the disorder and its symptoms clearly and empathetically: ### 1. Understanding Parkinson\'s Disease Parkinson's disease is a **neurodegenerative disorder** that primarily affects the **nervous system**, particularly the area of the brain called the **substantia nigra**, which is responsible for producing **dopamine**. - **What happens in the brain?** - The **substantia nigra**, part of the brain that controls movement, progressively loses cells that produce **dopamine**, a neurotransmitter critical for smooth, coordinated movements. - Dopamine acts as a chemical messenger that transmits signals between brain areas responsible for initiating and controlling voluntary movement. ### 2. Explaining Symptoms You can use your understanding of the nervous system to explain **why specific symptoms occur**, connecting them to the loss of dopamine and its effects on the brain and body. - **Motor Symptoms** (caused by reduced dopamine levels): - **Tremors**: Dopamine helps regulate fine motor control, so its loss leads to involuntary shaking, usually starting in one hand. - **Bradykinesia (slowness of movement)**: Without enough dopamine, the brain struggles to send signals to the muscles, making movements slower and harder to initiate. - **Rigidity (muscle stiffness)**: Muscles may feel tight or resistant to movement because of disrupted communication between the brain and motor neurons. - **Postural Instability**: The loss of dopamine affects balance and coordination, increasing the risk of falls. - **Non-Motor Symptoms** (caused by broader nervous system effects): - **Cognitive changes**: Dopamine also plays a role in other brain functions, so patients may experience memory issues, slowed thinking, or depression. - **Autonomic dysfunction**: The autonomic nervous system, which regulates involuntary functions like digestion and blood pressure, may be disrupted, leading to constipation or low blood pressure. - **Sleep disturbances**: The nervous system\'s role in sleep regulation may also be impaired. ### 3. Using Analogies for Clarity To make this information relatable: - Compare dopamine to a **\"messenger\"** or a **\"fuel\"** for the brain\'s movement control system. Without enough dopamine, it\'s like trying to drive a car with very little gas---the movements are slower, less smooth, and harder to control. - The **brain circuits** involved in movement are like a highway, and dopamine is the signal that tells the cars (messages to muscles) to move smoothly. When dopamine is low, the traffic slows or gets stuck. ### 4. Reassurance and Empathy - Explain that while Parkinson's disease is chronic, treatments (like medications or physical therapy) aim to **increase dopamine levels** or manage symptoms, improving quality of life. - Reassure the patient that their symptoms are a result of the brain's natural processes, and emphasize that with proper care, they can still lead a fulfilling life. By explaining Parkinson's disease in connection with the nervous system, you empower the patient to better understand their condition and how their brain and body are affected. **Mod. 6 \-- The Nervous System and the Endocrine System:** **Communicating Within the Body** **[THE NERVOUS SYSTEM]** **Da aggiungere** Controls **reflexes** (automatic, involuntary responses to stimuli).(spinal cors) Connects the CNS to the body\'s extremities. (PNS)  **Sympathetic Division:** - Activates during emergencies ("fight-or-flight response"). - Increases heart rate, sweat, goosebumps, and redirects energy to respond to threats.  **Parasympathetic Division:** - Calms the body after emergencies. - Slows heart rate, reduces sweating, restores pre-crisis state. Study alert: components of the central and peripheral nervous systems **The major functions of the autonomic nervous system.** - The sympathetic division acts to prepare certain organs of the body for stressful situations - the parasympathetic division acts to calm the body after the emergency has passed. **Reflexes and Types of Neurons** - **Reflex:** - Involves **three types of neurons**: 1. **Sensory (afferent) neurons:** Transmit information from the body's perimeter to the CNS/brain. 2. **Motor (efferent) neurons:** Transmit information from the CNS/brain to muscles and glands. 3. **Interneurons:** Coordinate between sensory and motor neurons in the spinal cord. **[ENDOCRINE SYSTEM:]** **Endocrine System Overview** - A **chemical communication network** that sends messages throughout the body via the bloodstream.**(study alert)** - Secretes **hormones**, which regulate the body\'s functioning and growth. - Influences---and is influenced by---the nervous system. **Hormones** - Chemicals that **circulate through the blood** and regulate various functions. - Similar to neurotransmitters but differ in speed and transmission mode: - **Neural messages**: Measured in milliseconds, travel through specific lines. - **Hormonal messages**: May take minutes and travel throughout the body. - Hormones affect only **cells tuned to the appropriate hormonal message** (specific receptors). **Pituitary Gland (\"Master Gland\")** - A **key component of the endocrine system**, located near and regulated by the hypothalamus. - Controls the functioning of the rest of the endocrine system. - Secretes hormones responsible for: - **Growth** (abnormalities cause unusual height variations). - **Emotional reactions**, sexual urges, and energy levels. **Thyroid Gland** - **Regulates metabolism** by controlling the rate at which the body uses energy. - Secretes **thyroxine (T4)** and **triiodothyronine (T3)**, which influence energy levels, body temperature, and growth. **Parathyroid Glands** - Regulate **calcium levels** in the blood and bones. - Secretes **parathyroid hormone (PTH)**, which increases calcium levels when too low. **Pancreas** - Regulates **blood sugar** levels. - Secretes **insulin** (lowers blood sugar) and **glucagon** (raises blood sugar). - Key player in **metabolism** and energy balance. **Adrenal Glands** - Secrete hormones involved in the **stress response** and regulation of **metabolism**. - Produce **adrenaline** and **cortisol**, which increase heart rate and energy during stress. - The adrenal cortex also secretes **aldosterone**, which helps regulate sodium and water balance. **Hypothalamus** - **Regulates the endocrine system** via the pituitary gland. - Controls **hunger**, **thirst**, **temperature regulation**, and **circadian rhythms**. - Coordinates the **fight-or-flight** response via the sympathetic nervous system. **Connection to the Nervous System** - Though separate, the endocrine system is closely **linked to the hypothalamus**, forming a bridge between neural and hormonal communication. **[mod.7 \-- the brain]** **[MACHINES/INSTRUMENTS TO STUDY THE BRAIN]** - **EEG (Electroencephalogram):** Records electrical activity in the brain through electrodes on the scalp. It\'s used to monitor brain wave patterns and diagnose disorders like epilepsy and learning disabilities. - **fMRI (Functional Magnetic Resonance Imaging):** Uses magnetic fields to create detailed 3D images of brain structures and activity, tracking blood flow to identify active brain areas. It\'s used for diagnosing conditions like strokes and Alzheimer\'s and helps in brain surgery planning. - **PET (Positron Emission Tomography):** Shows biochemical activity in the brain by injecting a radioactive substance. It highlights active regions and is useful for detecting tumors, memory issues, and other brain abnormalities. - **TMS (Transcranial Magnetic Stimulation):** Uses magnetic fields to temporarily disrupt brain activity in specific regions. It helps understand brain functions and is being explored for treating disorders like depression and schizophrenia. **[THE CENTRAL CORE:OUR OLD BRAIN]** - **Central Core (Old Brain):** - Controls [basic survival] functions ([breathing, eating, sleeping]) - Similar across all vertebrates - Evolution traced back 500 million years - **Hindbrain(base of the skull) contains:** - **Medulla:** Controls critical body functions (breathing, heartbeat) - **Pons:** Transmits motor information, coordinates muscle movement, and regulates sleep - **Cerebellum:** Controls bodily balance, coordinates muscle movement, and helps with intellectual functions (sensory analysis, problem solving) - **Reticular Formation:** - Nerve network from the medulla through the pons, midbrain, and forebrain - Regulates arousal, awareness, and sleep-wake cycle - Filters stimuli to allow undisturbed sleep - **Thalamus:** - Relay station for sensory information (sight, hearing, touch) - Sends information to higher brain regions and integrates info to medulla and cerebellum - **Hypothalamus:** - Maintains homeostasis (steady internal environment, body temperature, nutrient balance) - Regulates behaviors critical to survival (eating, self-protection, sex) **[THE LYMBIC SYSTEM:BEYOND THE CENTRAL CORE]** - **Limbic System:** - Controls emotions, self-preservation, and basic functions (eating, aggression, reproduction) - Involved in learning, memory, and the experience of pleasure - Consists of structures like the **amygdala** and **hippocampus** - Sometimes called the \"animal brain\" due to similarities with other mammals\' brains - **Amygdala:** - Involved in **fear** and **aggression** - Injury can alter behavior - **Hippocampus:** - Plays a key role in **learning** and **memory** - Removal or damage can impair the ability to learn new information and recall past events - **Pleasure Centers:** - The limbic system contains areas that generate pleasure when stimulated - **Electric stimulation** in these areas produces intense feelings of pleasure - Similar electrical stimulation in humans has been described as intensely pleasurable, similar to **sexual orgasm** - **Impact of Injury or Stimulation:** - Injury to the limbic system can dramatically alter behavior - Electrical stimulation can cause compulsive behaviors ### [The motor area of the cortex] - **Function:** Responsible for voluntary body movements. - **Mapping:** Each part of the motor area corresponds to a specific body part. - **Research Findings:** - The **motor cortex** is organized somatotopically (each body part has a corresponding area in the cortex). - Larger areas of the motor cortex are dedicated to **precise, delicate movements** (e.g., facial expressions, finger movements). - Smaller areas control **larger-scale movements** with less precision (e.g., movement of the knee, hip). - The **motor area** is involved not only in producing movement but also in **directing complex body postures** [The Sensory Area of the Cortex:] - **Function:** Processes sensory input from different parts of the body. - includes **three regions**: - one that corresponds primarily to body sensations **/somatosensoryvisual areaauditory area/** - **Somatosensory Area (Parietal Lobe):** - **Corresponds to body sensations** like touch and pressure. - The more **brain tissue** dedicated to a specific body part, the **greater the sensitivity** in that part of the body. - **Example:** Fingers, which require fine sensory control, are allocated more brain area than less sensitive parts. - The sensory map of the body in the brain is represented in an unusual way - **Auditory Area (Temporal Lobe):** - Responsible for the sense of **hearing**. - **Electrical stimulation** of the auditory area produces sounds like **clicks** or **hums**. - Certain **locations** in the auditory area respond to specific **pitches** (frequency of sound). - **Visual Area (Occipital Lobe):** - Responsible for the sense of **sight**. - **Electrical stimulation** of the visual area leads to experiences like **flashes of light** or **colors**. - **Input from the eyes** is processed in this area, and more brain area is devoted to the **sensitive** parts of the retina. - Different parts of the retina correspond to specific parts of the **visual cortex** (again, with more brain area for more sensitive areas). **Study alert:** - **Motor Area Mapping:** - **Larger regions** of the motor cortex control **fine movements**. - **Smaller regions** handle less detailed actions. - **Sensory Area Mapping:** The sensory area is also **somatotopically mapped**, where the size of each body part in the sensory map corresponds to the **sensory sensitivity** of that body part. For example: - **Fingers** and **lips** have large portions of the sensory area dedicated to them because of their high **sensitivity to touch**. - The sensory area for **less sensitive areas** (like the back) is much smaller. ### [The Association Areas of the Cortex:] - **Function:** Involved in **higher mental processes** such as: - **Thinking**, **language**, **memory**, **speech**. - Also controls **executive functions**, which include: - **Planning**, **goal setting**, **judgment**, **impulse control**. - Make up a large portion of celebral cortex - **Key Example:** **Phineas Gage**, a railroad worker who survived an explosion that drove an iron rod through his skull, is a classic case. The injury likely affected the **association areas**, leading to significant **personality changes**. Before the accident, he was responsible and cautious, but after the injury, he became reckless and impulsive. - **Impact of Damage to Association Areas:** - **Injuries** to the association areas can lead to **changes in personality**, affecting moral judgment, emotional processing, and impulse control. - **Cognitive abilities** such as reasoning, calculation, and memory can remain intact even with damage to these areas. - **Aphasia (language disorders) due to association area damage:** - **Broca's Aphasia**: Difficulty **speaking**---patients have trouble forming words but may understand language. - **Wernicke's Aphasia**: Difficulty **understanding others\' speech** and producing meaningful speech (e.g., fluent but nonsensical speech). **[THE SPECIALIZATION OF THE HEMISPHERES:TWO BRAINS OR ONE?]** **The Hemispheres of the Brain** - The brain is divided into two hemispheres: left and right, controlling opposite sides of the body. - **Left Hemisphere**: - Controls the right side of the body. - Processes information sequentially (one step at a time). - Focuses on verbal tasks: speaking, reading, reasoning, etc. - **Right Hemisphere**: - Controls the left side of the body. - Processes information globally (as a whole). - Specializes in nonverbal tasks: spatial relationships, music, pattern recognition, emotional expression. **Lateralization** - **Lateralization**: The dominance of one hemisphere in specific functions, like language processing in the left hemisphere for most people. - The degree of specialization varies: - **Right-handed people**: Language processing mainly in the left hemisphere. - **Left-handed/ambidextrous people**: Language processing more likely in the right hemisphere or split between both hemispheres. **Brain Function Interdependence** - Despite specialization, both hemispheres work together (interdependently). - The differences in specialization between hemispheres are not significant. - If a person loses function in one hemisphere (e.g., after injury), the other hemisphere may compensate, especially in younger individuals. **Study alert**: Although the hemispheres of the brain specialize in particular kinds of functions, the degree of specialization is not great, and the two hemispheres work interdependently. **Brain Theory by Stephen Kosslyn** - An alternative theory suggests the primary difference is not between the hemispheres but between the upper and lower halves of the brain: - **Top-brain system**: Specializes in planning and goal-setting. - **Bottom-brain system**: Processes sensory information. **Key Takeaways:** - The left and right hemispheres specialize in different tasks but work together. - The differences in hemisphere functions are not absolute, and brain compensation is possible in cases of injury. - Research continues into lateralization differences across genders and cultures. **[THE SPLIT-BRAIN]** - **Split-brain** patients have had their corpus callosum severed (usually as a treatment for severe epilepsy). - This procedure stops seizures but causes coordination issues between the two hemispheres. - Experiments with split-brain patients show the hemispheres function independently: - When an object is touched with the right hand (processed by the left hemisphere), patients can name it. - When touched with the left hand (processed by the right hemisphere), patients cannot name it aloud but can identify it. **[APPROFONDIMENTI]** -An Office Worker Could personal differences in people's specialization of right and left hemispheres be related to occupational success? For example, might a designer who relies on spatial skills have a different pattern of hemispheric specialization than does a lawyer? Sì, le differenze personali nella specializzazione emisferica (o lateralizzazione) del cervello possono influenzare le abilità cognitive che sono rilevanti per determinate occupazioni, il che potrebbe a sua volta influire sul successo professionale. ### La lateralizzazione emisferica: - **Emisfero sinistro**: Associato a funzioni analitiche, logiche, linguistiche, matematiche e sequenziali. È spesso dominante per il linguaggio e il ragionamento analitico. - **Emisfero destro**: Associato a funzioni creative, spaziali, visive e intuitive. È importante per le capacità artistiche, la percezione spaziale e l\'elaborazione globale. ### Differenze nelle professioni: - **Designer (emisfero destro dominante)**: - Un designer potrebbe avere una specializzazione nell\'emisfero destro, che facilita abilità come la percezione spaziale, la creatività e l\'interpretazione visiva. Queste capacità sono fondamentali per il lavoro di progettazione e design. - L\'emisfero destro potrebbe anche essere più attivo nel riconoscere schemi e generare nuove idee. - **Avvocato (emisfero sinistro dominante)**: - Un avvocato potrebbe fare maggiore affidamento sull\'emisfero sinistro, che supporta il linguaggio, il ragionamento logico e la capacità di elaborare dettagli complessi in modo analitico. - L\'emisfero sinistro facilita anche il pensiero sequenziale, utile per costruire argomentazioni legali e analizzare prove. ### Influenza sul successo professionale: - Le persone che sfruttano appieno la specializzazione emisferica in linea con i requisiti della loro professione potrebbero avere un vantaggio naturale. - Tuttavia, il successo professionale dipende anche da altri fattori, come la capacità di integrare le abilità di entrambi gli emisferi. Ad esempio: - Un designer deve comunicare le sue idee (funzione dell\'emisfero sinistro). - Un avvocato potrebbe aver bisogno di pensiero creativo per risolvere problemi complessi o presentare un caso in modo innovativo (funzione dell\'emisfero destro). ### Conclusione: Sebbene la specializzazione emisferica possa influenzare le predisposizioni naturali, lo sviluppo di competenze in entrambi gli emisferi e la capacità di integrarli sono fondamentali per il successo professionale in qualsiasi campo. **-Differences Between Males and Females, Cultures** Research suggests subtle differences in brain lateralization patterns between males and females and across cultures \- **Hemispherectomy Case** - In extreme cases, such as hemispherectomy, one hemisphere is removed, and the other can often compensate. - Example: Christina Santhouse, who had her right hemisphere removed, later completed a master\'s degree in speech pathology.