Nervous System PDF

Nervous System 1. Introduction to the Nervous System ▪ Brainstem: Controls vital Definition:...

Nervous System 1. Introduction to the Nervous System ▪ Brainstem: Controls vital Definition: The nervous system is a functions complex network of specialized cells (heart rate, (neurons and glial cells) that coordinates the breathing) and body's actions and responses by relays signals transmitting signals between different parts between the of the body. brain and Functions: spinal cord. o Control and Regulation: Maintains ▪ Spinal Cord: Transmits homeostasis by regulating internal signals to and from the brain; processes. contains reflex centers. o Communication: Enables Peripheral Nervous System (PNS): communication between different o Components: All nerves outside the body parts through electrical and CNS, including cranial nerves (12 chemical signals. pairs) and spinal nerves (31 pairs). o Integration: Processes sensory o Functions: Connects the CNS to information and generates limbs and organs, facilitating appropriate responses communication. Somatic Nervous System: Controls 2. Major Divisions of the Nervous System voluntary movements through skeletal muscles. Central Nervous System (CNS): Autonomic Nervous System: o Components: Regulates involuntary functions. ▪ Brain: The control center for ▪ Sympathetic Nervous processing information and System: Activates "fight or coordinating responses. flight" responses during ▪ Regions of the stress. Brain: ▪ Parasympathetic Nervous ▪ Cerebrum: System: Activates "rest and Largest part, digest" activities, promoting responsible for relaxation and conservation higher brain of energy. functions (thinking, memory, CNS: Brain emotion). 1. Cerebrum ▪ Cerebellum: The largest part of the brain, divided into two Coordinates hemispheres (left and right) and further divided into movement lobes. and balance; important for Frontal Lobe: motor o Functions: learning.  ▪ Executive functions o Coordination of voluntary (planning, reasoning). movements (balance and posture). ▪ Motor control (voluntary o Motor learning (fine-tuning movements). movements). ▪ Speech production (Broca's o Regulation of muscle tone. area). o Integration of sensory information for ▪ Personality and emotional smooth execution of movements. regulation. 3. Brainstem Parietal Lobe: Connects the brain to the spinal cord and regulates o Functions: vital functions. ▪ Processing sensory Midbrain: information (touch, o Functions: temperature, pain). ▪ Visual and auditory reflexes ▪ Spatial awareness and navigation. (e.g., turning the head toward a sound). ▪ Integration of sensory input ▪ Regulation of motor control (e.g., recognizing objects by (involvement in dopamine touch). pathways). Temporal Lobe: Pons: o Functions: o Functions: ▪ Auditory processing (hearing). ▪ Relays information between the cerebrum and ▪ Memory formation cerebellum. (hippocampus). ▪ Regulation of sleep and ▪ Language comprehension respiratory functions. (Wernicke's area). Medulla Oblongata: ▪ Emotion regulation o Functions: (amygdala). ▪ Control of autonomic Occipital Lobe: functions (heart rate, blood o Functions: pressure, breathing). ▪ Visual processing ▪ Reflex centers for coughing, (interpreting visual sneezing, and swallowing. information). 4. Diencephalon ▪ Recognition of shapes and colors. Located beneath the cerebrum and above the brainstem. 2. Cerebellum Thalamus: Located at the back of the brain, beneath the o Functions: cerebrum. Functions:  ▪ Relay station for sensory Cerebrum: Higher cognitive functions, information (except smell) to sensory processing, motor control, the cerebral cortex. emotional regulation. ▪ Regulation of consciousness, Cerebellum: Coordination, balance, and sleep, and alertness. fine motor skills. Hypothalamus: Brainstem: Autonomic functions, reflexes, and basic survival functions. o Functions: Diencephalon: Sensory relay, homeostasis, ▪ Regulation of homeostasis and circadian rhythms. (temperature, hunger, thirst). Limbic System: Emotions, memory ▪ Control of the endocrine processing, and motivation. system (via the pituitary gland). Basal Ganglia: Motor control and learning of routines/habits. ▪ Regulation of circadian rhythms. 5. Limbic System 3. Cranial Nerves A complex set of structures located beneath the The 12 pairs of cranial nerves are essential for cerebrum. various sensory and motor functions: Amygdala: 1. Olfactory Nerve (I): Smell. o Functions: 2. Optic Nerve (II): Vision. ▪ Processing emotions (fear, 3. Oculomotor Nerve (III): Eye movement, pleasure). pupil constriction. ▪ Involvement in memory and 4. Trochlear Nerve (IV): Eye movement. emotional responses. 5. Trigeminal Nerve (V): Sensation from the Hippocampus: face, chewing. o Functions: 6. Abducens Nerve (VI): Eye movement. ▪ Critical for memory formation 7. Facial Nerve (VII): Facial expressions, and spatial navigation. taste, salivary glands. ▪ Involved in learning and 8. Vestibulocochlear Nerve (VIII): Hearing contextual memory. and balance. 6. Basal Ganglia 9. Glossopharyngeal Nerve (IX): Taste, swallowing, salivary glands. A group of nuclei located deep within the cerebral hemispheres. 10. Vagus Nerve (X): Heart rate, digestive tract, and parasympathetic control. Functions: 11. Accessory Nerve (XI): Shoulder and neck o Regulation of voluntary motor movement. movements and procedural learning. 12. Hypoglossal Nerve (XII): Tongue o Involvement in habit formation and movement. reward processing. Summary of Brain Functions 4. Spinal Nerves There are 31 pairs of spinal nerves categorized by o Axon Terminals (Synaptic region: Boutons): End of the axon where neurotransmitters are released into Cervical Nerves (C1-C8): Control head, the synaptic cleft. neck, diaphragm, arms. Thoracic Nerves (T1-T12): Control trunk and abdominal muscles. 6. Neurotransmitters Lumbar Nerves (L1-L5): Control lower Definition: Chemical messengers released back and legs. by neurons to transmit signals across synapses. Sacral Nerves (S1-S5): Control pelvis and legs. Mechanism of Action: Coccygeal Nerve (Co1): Innervates the o Neurotransmitters are released from tailbone area. the presynaptic neuron into the synaptic cleft. o They bind to receptors on the 5. Structure of Neurons postsynaptic neuron, generating Types of Neurons: excitatory or inhibitory postsynaptic potentials. o Unipolar Neurons: One process extending from the cell body, Examples: commonly found in sensory o Acetylcholine: Involved in muscle pathways. activation and memory. o Bipolar Neurons: Two processes o Dopamine: Affects mood, reward (one axon and one dendrite); pathways, and motor control; typically involved in sensory implicated in Parkinson’s and functions (e.g., vision). addiction. o Multipolar Neurons: Many o Serotonin: Regulates mood, sleep, dendrites and a single axon; most and appetite; low levels are common type, found in motor and associated with depression. interneurons. o Norepinephrine: Involved in arousal Main Parts: and the fight or flight response. o Cell Body (Soma): Contains the nucleus, cytoplasm, and organelles (e.g., mitochondria, ribosomes). 7. Reflex Formation o Dendrites: Receive signals from Definition: A reflex is an automatic, other neurons; contain receptors for involuntary response to a stimulus that neurotransmitters. involves a reflex arc. o Axon: Long projection that conducts Components of a Reflex Arc: electrical impulses (action potentials) away from the cell body. 1. Receptor: Detects the stimulus (e.g., pain, pressure). ▪ Node of Ranvier: Gaps in 2. Sensory Neuron: Transmits the the myelin sheath where signal from the receptor to the spinal action potentials are cord. regenerated, facilitating rapid signal transmission. 3. Interneuron (in spinal cord): Processes the information and  connects sensory and motor of Ranvier to another, increasing the neurons (may be absent in simple speed of transmission. reflexes). 4. Motor Neuron: Sends the signal 9. Protective Structures from the spinal cord to the effector (muscle or gland). Meninges: Three protective membranes surrounding the brain and spinal cord: 5. Effector: The muscle or gland that responds to the motor neuron signal o Dura Mater: Tough outer layer; (e.g., muscle contracts). provides protection and structure. Example of a Reflex: The knee-jerk reflex o Arachnoid Mater: Middle layer; (patellar reflex) involves tapping the patellar web-like and contains cerebrospinal tendon, which stretches the quadriceps fluid (CSF). muscle, causing a quick contraction. o Pia Mater: Delicate inner layer; closely adheres to the surface of the brain and spinal cord. 8. Action Potential Cerebrospinal Fluid (CSF): Definition: An action potential is a rapid change in the membrane potential of a o Functions: Cushions the brain, neuron, allowing the transmission of provides nutrients, removes waste, electrical signals along the axon. and acts as a barrier against infection. Phases of Action Potential: 1. Resting Potential: The neuron is at rest (-70mV), with higher 10. Diseases and Disorders concentrations of Na⁺ outside and K⁺ inside the cell. Multiple Sclerosis (MS): An autoimmune disorder that damages the myelin sheath, 2. Depolarization: A stimulus causes disrupting communication between neurons. Na⁺ channels to open, allowing Na⁺ to flow into the neuron, making the Alzheimer’s Disease: A progressive inside more positive (up to +30mV). neurodegenerative disorder characterized by memory loss and cognitive decline due 3. Repolarization: Na⁺ channels close, to neuron death and plaque formation. and K⁺ channels open, allowing K⁺ to flow out, returning the membrane Parkinson’s Disease: A movement potential to a negative value. disorder caused by the loss of dopamine- producing neurons in the substantia nigra, 4. Hyperpolarization: The membrane leading to tremors and rigidity. potential becomes more negative than resting potential due to excess K⁺ outflow. 11. Diagnostic Tools 5. Return to Resting Potential: The Electroencephalogram (EEG): Measures sodium-potassium pump restores electrical activity of the brain; useful for the original concentrations of Na⁺ diagnosing epilepsy and sleep disorders. and K⁺. Magnetic Resonance Imaging (MRI): Propagation of Action Potential: Provides detailed images of brain o Action potentials propagate along structures; helps detect tumors, lesions, and myelinated axons through saltatory other abnormalities. conduction, jumping from one Node  Computed Tomography (CT) Scan: Uses X-rays to create cross-sectional images; helpful in identifying bleeding or structural changes. 12. Conclusion Importance of the Nervous System: Essential for survival, enabling organisms to perceive their environment, respond to stimuli, and maintain homeostasis. Future Directions: Ongoing research aims to better understand the complexities of the nervous system, including the development of therapies for neurodegenerative diseases and mental health disorders.