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Rita Garcia-Gonzalez The Nervous System Period: 3, ◦ These amines are…

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        Spinal Cord Jury: Damage to the spinal cord
        
        Symptoms: weakness, loss of bladder and bowel control, paralysis
        
        Treatment: (cannot be treated, if server spinal cord damage) bed rest, surgery, and medication to reduce swelling.
        
        Causes: Common in men ( age 15-35), weakened vertebral column, and fluid build - up around spinal cord
        
        Alzheimer's Disease: A form of dementia associated with age
        
        Symptoms: Memory loss and difficulty speaking, swallowing and/or walking
        
        Treatment: Incurable and Medication
        
        Causes: Age Over 60 and past head trauma
      - Autism: Brain disorder that makes it difficult to communicate
        
        Symptoms: Delay in learning to talk/noncumulative and repeat behavior
        
        Treatment: Medication and behavior management
        
        Causes: Mostly males, past medical issues, and Hereditary
      - Cerebrovascular Accident: Occurs when blood flow to a portion of the brain is halted.
        
        Symptom: Confusion and lost of memory and server headaches
        
        Treatment: Blood thinner, Hospitalization, and stroke rehabilitation
        
        Causes: Diabetes and Blood vessel bursts
- - - - Cocaine: Effects the dopamine transporters. Cocaine blocks these transporters, leaving dopamine trapped in the synaptic clef. This leads to dopamine binds again and again to the receptors overstimulating the cell.
        
        Active in the part of the brain controlling voluntary moments. This is they cocaine abusers are so fidgety and unable to stay still.
        
        LSD: Interferes with serotonin receptors by binding to them. LSD interacts with particular receptors, but not the same way. ISC may inhibilation and sometimes it may excite them.
        
        Affects the IC branch which is responsible for feeling of wakefulness and evoking a startle response to unexpected stimulus.
        
        Methamphetamine: Interferes with dopamine by mimicking them. Once meth enters, dopamine vesicles forced the dopamine molecules out. This causes transporters to work reverse, actively pumping dopamine out of the cell and into synapse.
        
        Its highly addictive and works directly on the brains reward pathway, making the user fell intense pleasure and exhilaration
        
        Marijuana: Mimics the anandamide and binds to cannabinoid receptors. Inhibition is turned off and dopamine is allowed to squirt into the synapse.
        
        It's involved in removing unnecessary short term memories. Responsible for slowing down movement, making us feel relaxed and calm.
        
        Alcohol: Interferes with Gaba receptors and makes them even more inhibitory. Alcohol makes gaba receptors even more inhibition then binds to glutamite receptors, preventing the glutamite from exciting the cell.
        
        Affects areas of the brain involved with memory formation, decisions making, and impulse control.
    - - Affects the mood, sleep, perception, and appetite. Ecstasy also indirectly interacts with the reward pathway.
    - - It affects the brain response to pain signals, stress and emotional attachment.
- - - - I. Central Nervous System (CNS): The CNS consists of the brain and the spinal cord. The Brain The adult brain is structurally organized into four major regions:
        
        Cerebral Hemispheres (Cerebrum): These form the superior part of the brain and account for 83% of the brain mass. Each hemisphere has three basic regions: ◦ Cerebral cortex (superficial gray matter). ◦ White matter (internal). ◦ Basal nuclei (deep within white matter
        
        The cerebral hemispheres are further divided into five lobes by sulci: ◦ Frontal lobe. ◦ Parietal lobe. ◦ Temporal lobe. ◦ Occipital lobe. ◦ Insula lobe (buried beneath portions of the frontal, parietal, and temporal lobes)
        
        3.Diencephalon: This region consists of three paired gray-matter structures: ◦ Thalamus. ◦ Hypothalamus. ◦ Epithalamu
        
        Brain Stem: This region consists of three sub-regions: ◦ Midbrain. ◦ Pons. ◦ Medulla oblongata (Medulla).
        
        Cerebellum The Cerebellum is located dorsal to the pons and medulla. It contains a thin cortex of gray matter and a distinctive treelike pattern of white matter called the arbor vitae
        
        Subdivisions of the Spinal Cord The spinal cord is protected by bone, meninges, and cerebrospinal fluid (CSF). In cross-section, it features a central core of gray matter surrounded by white matter.
        
        II. Spinal Cord Subdivisions The spinal cord exhibits a basic CNS pattern: a central cavity surrounded by gray matter, with white matter external to the gray matter. • Gray Matter (Core, H-shaped): ◦ Dorsal horns: Contain interneurons that receive somatic and visceral sensory input. ◦ Ventral horns: Contain some interneurons and somatic motor neurons. ◦ Lateral horns: Found only in the thoracic and superior lumbar regions, containing sympathetic neurons. ◦ Gray commissure: A bridge of gray matter connecting the masses on either side, enclosing the central canal. • White Matter (Columns/Funiculi): The white matter is divided into three columns on each side: ◦ Dorsal (posterior) funiculus ◦ Lateral funiculus ◦ Ventral (anterior) funiculus
      - Peripheral Nervous System (PNS)
        The Peripheral Nervous System (PNS) includes the spinal nerves, which attach to the spinal cord via 31 paired roots
        
        -8 cervical, 12 thoracic, 5 lumbar, 5sacral, 1coccygeal
  - - - Hypothalamus: The main visceral control and regulating center vital to homeostasis. Its functions include: ◦ Controlling the autonomic nervous system (e.g., blood pressure, heart rate, pupil size). ◦ Initiating physical responses to emotions (as part of the limbic system). ◦ Regulating body temperature, hunger, satiety, water balance, and thirst. ◦ Regulating sleep-wake cycles. ◦ Controlling endocrine system functions
      - Epithalamus: Contains the pineal gland, which secretes melatonin that helps regulate the sleep-wake cycle. D. Brain Stem The brain stem controls automatic behaviors necessary for survival. • Pons: Some nuclei help maintain the normal rhythm of breathing. • Medulla Oblongata: Contains critical centers: ◦ Cardiovascular center (adjusts heart contraction force/rate and blood vessel diameter for blood pressure regulation). ◦ Respiratory centers (generate respiratory rhythm and control the rate and depth of breathing). ◦ Other centers regulate vomiting, hiccupping, swallowing, coughing, and sneezing. E. Cerebellum The cerebellum processes input from the cortex, brain stem, and sensory receptors to provide precise, coordinated movements of skeletal muscles. It is also essential for balance and coordination and plays a role in thinking, language, and emotion.
      - II. Functional Roles of the Brain Regions
        
        A. Cerebral Cortex (The "Executive Suite") The cerebral cortex is the site of the conscious mind. Its functions include: • Consciousness and Sensation: The cortex is responsible for awareness, sensory perception, communication, memory storage, and understanding. • Motor Control: ◦ Motor areas control voluntary movement. ◦ The Primary motor cortex controls voluntary movement and exhibits somatotopy (mapping muscles of the body). ◦ The Premotor cortex helps plan movements, acts as a staging area for skilled motor activities, and controls learned, repetitious, or patterned motor skills.
        
        B. Cerebral White Matter and Basal Nuclei • Communication: Cerebral white matter is responsible for communication between cerebral areas, and between the cortex and lower CNS. • Movement Regulation: The basal nuclei influence muscle movements, regulate the intensity of slow or stereotyped movements, filter out incorrect/inappropriate responses, and inhibit unnecessary movements. They also play a role in cognition and emotion
        
        C. Diencephalon 1. Thalamus: Serves as the relay station for information coming into the cortex. It sorts, edits, and relays ascending input, mediating sensation, motor activities, cortical arousal, learning, and memory
        
        ◦ Broca’s area is the motor speech area that directs muscles of speech production and is active in planning speech. • Sensory Processing: Sensory areas are concerned with the conscious awareness of sensation. The Somatosensory association cortex integrates sensory input to allow for the understanding of an object, determining its size, texture, and relationship of parts. • Integration: Multimodal association areas receive inputs from multiple sensory areas, allowing us to give meaning to information received, store it in memory, tie it to previous experience, and decide on actions
      - III. Functional Brain Systems (Networks)
        
        Reticular Formation: This system governs brain arousal. Its motor function helps control coarse limb movements, and its autonomic centers regulate visceral motor functions (such as cardiovascular and respiratory control).
        
        Limbic System: This is the emotional or affective brain. It puts emotional responses to odors, allows us to react emotionally to things we consciously understand, and makes us consciously aware of emotional richness. The hippocampus and amygdaloid body play a role in memory
      - I. General Functions of the Central Nervous System (CNS) The CNS, consisting of the brain and spinal cord, performs overarching functions: • Communication and Reflexes: The spinal cord is the major reflex center where reflexes are initiated and completed, and it provides two-way communication to and from the brain and body. • Protection and Support: Cerebrospinal fluid (CSF) gives buoyancy to CNS structures, protects the CNS from blows and other trauma, and nourishes the brain and carries chemical signals.
- - - - Structure and Location:
        
        • Neuron Cell Bodies and Dendrites: These components are found within the gray matter. Specifically, the cerebral cortex (the superficial gray matter layer) is composed of neuron cell bodies, dendrites, glial cells, and blood vessels, but no axons.
        
        • Axons/Fibers: These are the primary component of white matter. In the cerebral white matter, these fibers are bundled into large tracts and are myelinated.
        
        • Motor Neurons: These are located in the spinal cord's ventral horns (somatic motor neurons) and lateral horns (sympathetic neurons/visceral motor). The axons of motor neurons form the ventral roots that exit the spinal cord. Destruction of ventral horn motor neurons and fibers of the pyramidal tract is associated with Amyotrophic Lateral Sclerosis (ALS).
        
        • Sensory Neurons: The cell bodies of sensory neurons are located in the dorsal root (spinal) ganglia, and their sensory input travels via the dorsal roots to the spinal cord.
      - Function (Specific Neuronal Structures):
        
        • Purkinje fibers originate in the cerebellum's cortex and synapse with the cerebellum
        
        The substantia nigra contains dopamine-releasing neurons. Degeneration of these neurons leads to Parkinson's disease.
        
        • Chemical variations in the brain environment can lead to uncontrollable neuron firings, which is prevented by the blood brain barrier.
        
        • An epileptic seizure involves a torrent of electrical discharges by groups of neurons.
      - The sources differentiate nervous tissue primarily based on the presence or absence of myelin:
        
        • Gray matter: This consists of short, nonmyelinated neurons and cell bodies.
        
        • White matter: This consists of myelinated and nonmyelinated axons. The white matter in the spinal cord and brain allows for communication between different parts of the spinal cord, and between the spinal cord and the brain.
      - Neuroglia (Glial Cells)
        
        Glial cells: These are a component of the superficial gray matter layer known as the cerebral cortex.
        • Ependymal cells: These are a type of neuroglial cell that lines the fluid-filled chambers (ventricles) of the brain. A layer of ependymal cells surrounds the capillaries of the choroid plexus, which produces cerebrospinal fluid (CSF).
    - - Functional Classification
        
        1. Sensory neurons (Afferent): These neurons transmit impulses from sensory receptors toward the CNS. Almost all sensory neurons are structurally unipolar, and their cell bodies are situated in ganglia in the Peripheral Nervous System (PNS).
        
        2. Motor neurons (Efferent): These neurons carry impulses from the CNS to effector organs (muscles and glands). Motor neurons are multipolar, and most of their cell bodies are located in the CNS (with the exception of some autonomic neurons).
        
        3. Interneurons (Association neurons): These neurons lie between motor and sensory neurons. They function to shuttle signals through CNS pathways. The vast majority of the body’s neurons (99%) are interneurons, and most are contained entirely within the CNS
        
        1. Multipolar neurons: These neurons have three or more processes, typically consisting of one axon and the rest being dendrites. They are the most common and major type of neuron found in the Central Nervous System (CNS).
        
        2. Bipolar neurons: These neurons have two processes: one axon and one dendrite. They are rare, found for example, in the retina and olfactory mucosa.
        
        3. Unipolar neurons: These neurons have one T-like process, which is also called pseudounipolar.
    - - Protection of the CNS (Meninges) The protective layers covering the CNS—the meninges—are primarily composed of connective tissue
        
        Components of the Nervous System
        
        Pia mater and a surrounding layer of ependymal cells enclose the choroid plexus, a cluster of capillaries that forms cerebrospinal fluid (CSF).
        • Within the cerebral cortex (the superficial layer of gray matter), the tissue is composed of neuron cell bodies, dendrites, glial cells, and blood vessels, but the sources do not explicitly mention connective tissue as a major component of this specific laye
        
        Dura mater is described as the strongest meninx.
        
        • Arachnoid mater is the middle layer, which has spiderweb-like extensions.
        
        • Pia mater is the innermost layer and is described as delicate connective tissue that clings tightly to the brain, following every convolution. The pia mater contains many tiny blood vessels that feed the brain.
        
        • The denticulate ligaments, which secure the spinal cord to the dura mater, are extensions of the pia mater
- - - - The spinal cord is enclosed within the vertebral column, beginning at the foramen magnum and usually ending at the L1 or L2 vertebra. It is protected by bone, meninges, and cerebrospinal fluid (CSF
      - Major Functions:
        
        • Two-way communication: Provides two-way communication pathways to and from the brain and the body.
        
        • Major reflex center: Reflexes are initiated and completed directly at the spinal cord level.
        
        Major Parts (Cross-sectional Anatomy):
        
        The spinal cord exhibits a basic CNS pattern: a central cavity surrounded by gray matter, with white matter external to the gray matter
      - 1. Gray Matter (Core): Located in the center, resembling a butterfly or the letter "H". The gray matter is divided into horns:
        
        ◦ Dorsal horns: Contain interneurons that receive somatic and visceral sensory input. ◦ Ventral horns: Contain interneurons and somatic motor neurons. The axons of these motor neurons exit the spinal cord via ventral roots. ◦ Lateral horns: Found only in the thoracic and superior lumbar regions, containing sympathetic neurons. ◦ Gray commissure: A bridge of gray matter that connects the two sides and encloses the central canal.
        
        2. White Matter (Outside): Consists of myelinated and nonmyelinated nerve fibers that allow communication between parts of the spinal cord, as well as between the spinal cord and the brain.
        
        ◦ The fibers run in three directions: ascending (sensory), descending (motor), and transverse. ◦ The white matter is divided into three columns, or funiculi, on each side: Dorsal (posterior), Lateral, and Ventral (anterior). Each column is composed of tracts of axons with similar destinations and functions.
        
        Associated Structures:
        
        • Spinal nerves: Formed by the fusion of the dorsal (sensory input) and ventral (motor neuron axons) roots. There are 31 paired roots attached to the spinal cord.
        • Cauda equina: A collection of nerve roots found at the inferior end of the vertebral canal.
    - - Diencephalon
        
        Consists of three paired gray-matter structures: the Thalamus, Hypothalamus, and Epithalamus, all enclosing the third ventricle
        
        The Thalamus is a relay station for information coming into the cortex; it mediates sensation, motor activities, cortical arousal, learning, and memory. The Hypothalamus is the main visceral control and regulating center vital to homeostasis. It controls the autonomic nervous system (e.g., blood pressure, heart rate), initiates physical responses to emotions, and regulates body temperature, hunger, thirst, sleep-wake cycles, and endocrine system functions. The Epithalamus contains the pineal gland, which secretes melatonin to help regulate the sleep-wake cycle
      - Brain Stem
        
        Consists of three regions: the Midbrain, Pons, and Medulla oblongata
        
        Controls automatic behaviors necessary for survival. The Midbrain contains visual reflex centers (superior colliculi) and auditory relay centers (inferior colliculi). The Pons contains nuclei that help maintain the normal rhythm of breathing. The Medulla Oblongata contains the cardiovascular center (adjusts heart rate/force and blood pressure) and respiratory centers (generate respiratory rhythm). It also regulates vomiting, swallowing, coughing, and sneezing.
      - Cerebral Hemispheres (Cerebrum)
        
        Forms the superior part of the brain, divided into five lobes (Frontal, Parietal, Temporal, Occipital, Insula). It includes the cerebral cortex (gray matter), internal white matter, and deep basal nuclei
        
        The Cerebral Cortex is the "executive suite" and the site of the conscious mind. Its functions include awareness, sensory perception, voluntary motor initiation, communication, memory storage, and understanding. It contains motor areas (control voluntary movement), sensory areas (conscious sensation awareness), and association areas (integrate diverse information). White matter facilitates communication between cerebral areas and between the cortex and lower CNS. Basal Nuclei influence muscle movements, play a role in cognition and emotion, regulate the intensity of slow or stereotyped movements, and filter out inappropriate responses
      - Cerebellum
        
        Located dorsal to the pons and medulla. Contains a thin cortex of gray matter
        
        Functions include processing input to provide precise, coordinated movements of skeletal muscles. It also plays a role in balance, coordination, thinking, language, and emotion.
- - - - Compare & contrast the autonomic nervous system
        
        The Autonomic Nervous System (ANS) is one of the two divisions of the motor (efferent) division of the Peripheral Nervous System (PNS).
        The ANS is characterized by its involuntary control, as it consists of visceral motor nerve fibers that regulate smooth muscle, cardiac muscle, and glands
        
        The ANS is further organized into two functional subdivisions that are generally antagonistic in action:
        
        Sympathetic subdivision.
        
        Parasympathetic subdivision
      - Reflex arc (major parts & functions)
        
        A reflex is a rapid, automatic response to a stimulus, where a particular stimulus always causes the same anticipated response. Reflexes operate over specific pathways called reflex arcs, which are the best example of serial processing in the nervous system (input travels along one pathway to a specific destination).
        
        A reflex arc consists of five essential components:
        
        1. Receptor: The site where the stimulus acts.
        
        2. Sensory neuron: Transmits the afferent impulse from the receptor toward the CNS.
        
        3. CNS integration center: This is the region within the CNS (brain or spinal cord) where the incoming sensory impulse is processed and interpreted, dictating the motor output.
        
        4. Motor neuron: Conducts the efferent impulse away from the CNS to an effector organ.
        
        5. Effector: The muscle fiber or gland cell that responds to the efferent impulse.
      - Neurotransmitters
        
        Neurotransmitters are often referred to as the language of the nervous system, with over 50 different types having been identified. Most neurons manufacture two or more neurotransmitters, which allows them to exert several influences. Neurotransmitters are classified based on their chemical structure and their function (effects and actions)
        
        Classification by Chemical Structure
        
        • Acetylcholine (ACh): This was the first neurotransmitter identified and is the best understood. It is released at neuromuscular junctions and is also utilized by many autonomic nervous system (ANS) neurons and some central nervous system (CNS) neurons. ACh is degraded by the enzyme acetylcholinesterase (AChE).
        
        • Biogenic Amines: This group includes:
        
        ◦ Catecholamines (Dopamine, Norepinephrine (NE), and Epinephrine), which are synthesized from the amino acid tyrosine
        
        ◦ Indolamines (Serotonin, derived from tryptophan, and Histamine, derived from histidine)
        
        • Amino Acids: Amino acids form all proteins, making it challenging to prove which ones function as neurotransmitters, though some are proven.
        
        • Peptides (Neuropeptides): These are strings of amino acids with diverse functions, such as endorphins (beta endorphin, dynorphin, and enkephalins), which act as natural opiates and reduce pain perception.
        
        • Purines: These monomers of nucleic acids affect both the CNS and PNS.
        
        • Gases and lipids: This group includes endocannabinoids, which act at the same receptors as THC (the active ingredient in marijuana).
        
        Classification by Function (Effects and Actions)
        
        The function of a neurotransmitter is grouped into effects and actions:
        
        • Effects: A neurotransmitter's effect is determined by the specific receptor it binds to, and it can be either excitatory (depolarizing) or inhibitory (hyperpolarizing), or both
        
        Actions
        
        ◦ Direct action: The neurotransmitter binds directly to and opens ion channels.
        
        ◦ Indirect action: The neurotransmitter acts through intracellular second messengers
- - - - Cranial nerves: Cranial nerves are components of the Peripheral Nervous System (PNS) that extend to and from the brain.
      - Spinal nerves: Spinal nerves are components of the Peripheral Nervous System (PNS) that extend to and from the spinal cord
        
        Key Structural Details:
        
        • Formation: A spinal nerve is formed by the fusion of two types of roots:
        
        ◦ Ventral roots: These are bundles of motor neuron axons that exit the spinal cord. ◦ Dorsal roots: These carry sensory input to the spinal cord.
        
        • Ganglia: The cell bodies of the sensory neurons are located in the dorsal root (spinal) ganglia.
        
        • Enlargements: Nerves that serve the upper and lower limbs emerge from areas of the spinal cord known as the cervical and lumbosacral enlargements.
        
        • Cauda Equina: This is a collection of nerve roots found at the inferior end of the vertebral canal, below where the spinal cord terminates (at the conus medullaris).
    - - The action potential (AP), also referred to as a nerve impulse in neurons, is the principal mechanism neurons use to send signals over long distances, and it does not decay over distance as graded potentials do. Action potentials are brief reversals of the membrane potential, involving a voltage change of approximately 100 mV, and they occur only in the axons of neurons and in muscle cells. The generation of an AP involves the sequential opening and closing of voltage-gated channels.
      - Steps in Generating an Action Potential
        
        Depolarization: Depolarizing local currents cause voltage-gated Na + channels to open, leading to an influx of Na + into the cell. If the depolarization reaches the threshold voltage (-55 to -50 mV), a positive feedback loop opens all Na + channels, resulting in a large AP spike where the membrane polarity jumps to +30 mV.
        
        Repolarization: The Na + channel inactivation gates close, causing Na + permeability to decline to the resting state, and the AP spike stops rising. Simultaneously, voltage-gated K + channels open, and K + exits the cell, causing the membrane to return to its resting membrane potential.
        
        Resting State: All gated sodium (Na + ) and potassium (K + ) channels are closed, maintaining the resting membrane potential (approximately -70 mV).
        
        Hyperpolarization: Some K + channels remain open, resulting in excessive K + efflux. This causes the inside of the membrane to become slightly more negative than the resting state, resulting in a slight dip below the resting voltage, and the Na + channels begin to reset.
      - AP conduction velocity varies widely:
        
        • Saltatory conduction: Occurs only in myelinated axons and is approximately 30 times faster. Myelin sheaths insulate the axon and prevent leakage of charge. APs are generated only at the myelin sheath gaps (where voltage-gated Na + channels are located), causing the electrical signal to jump rapidly from gap to gap.
        
        The refractory period is the time during which a neuron cannot trigger another AP because the voltage-gated Na + channels are open or inactivated, making the neuron unable to respond to a second stimulus. Damage to the myelin sheaths in the CNS, as seen in Multiple Sclerosis (MS), where myelin is destroyed and forms hardened lesions called scleroses, can cause impulse conduction to slow down and eventually cease.The refractory period is the time during which a neuron cannot trigger another AP because the voltage-gated Na + channels are open or inactivated, making the neuron unable to respond to a second stimulus. Damage to the myelin sheaths in the CNS, as seen in Multiple Sclerosis (MS), where myelin is destroyed and forms hardened lesions called scleroses, can cause impulse conduction to slow down and eventually cease.The refractory period is the time during which a neuron cannot trigger another AP because the voltage-gated Na + channels are open or inactivated, making the neuron unable to respond to a second stimulus. Damage to the myelin sheaths in the CNS, as seen in Multiple Sclerosis (MS), where myelin is destroyed and forms hardened lesions called scleroses, can cause impulse conduction to slow down and eventually cease.
        
        • Continuous conduction: Slow conduction that occurs in nonmyelinated axons