Week 1 - Homeostasis and the Cell (Updated September 16th) - Biology Past Paper

**Week 1 - Homeostasis and the Cell (Updated September 16th)** **Lesson 1 of 4: Introduction to Physiology and Homeostasis** **Overview** - **Focus on physiology\'s role in maintaining homeostasis.** - **Review of cell structure, particularly the cell membrane.** - **Exploration of how me...

**Week 1 - Homeostasis and the Cell (Updated September 16th)** **Lesson 1 of 4: Introduction to Physiology and Homeostasis** **Overview** - **Focus on physiology\'s role in maintaining homeostasis.** - **Review of cell structure, particularly the cell membrane.** - **Exploration of how membranes control ion and molecule movement.** **Key Questions** 1. **What is the definition of physiology?** - **Study of how systems (brain, heart, lungs, etc.) function in living organisms.** - **Explores mechanisms for controlling internal environments despite external changes.** - **Involves genetics, anatomy, biochemistry, biophysics, and cell biology.** 2. **What is the definition of homeostasis?** - **Maintenance of stable internal conditions regardless of external environment.** - **Dynamic process requiring constant monitoring and response to changes.** - **Key variables include:** - **Body temperature** - **Blood sugar levels** - **Blood pH** - **Oxygen and carbon dioxide levels** - **Blood pressure** - **Electrolyte balance** - **Water balance** 3. **Difference between internal and external environment?** - **Internal Environment: Constantly interacts with the external environment (e.g., digestive system, lungs, kidneys).** - **External Environment: Includes all substances not absorbed through cell membranes.** 4. **Components of a negative feedback loop?** - **Sensors, control center, and effectors.** - **Function: Detect changes and enact responses to maintain homeostasis.** 5. **How do negative feedback loops maintain homeostasis?** - **Regulate variables to stay within normal ranges.** - **Mechanisms turn off once ideal levels are reached.** 6. **Difference between positive and negative feedback loops?** - **Negative Feedback: Shuts off the mechanism when ideal levels are reached.** - **Positive Feedback: Amplifies changes until an external event occurs (e.g., childbirth contractions).** 7. **Organizational hierarchy of the body?** - **Atoms → Macromolecules → Organelles → Cells → Tissues → Organs → Organ Systems → Organisms.** - **Each level contributes to maintaining homeostasis.** **Key Takeaways** - **Physiology is essential for understanding how body systems work together to maintain homeostasis.** - **Negative feedback loops are vital for this process.** - **Understanding the structure and function of cells is crucial for learning physiology.** **Success Criteria** - **Ability to explain organizational hierarchies and mechanisms governing homeostasis using correct terminology.** - **Self-assessment through questioning and teaching others.** **Lesson 2 of 4: Body Fluids Compartments** **Overview** - **Focus on the composition and distribution of body fluids in maintaining homeostasis.** **Key Questions** 1. **Chemical composition of intracellular fluid, interstitial fluid, and plasma?** - **Intracellular fluid (67% of body fluid) has high K+ and protein concentration.** - **Interstitial fluid has a higher Na+, Cl-, and Ca++ concentration outside the cell.** - **Plasma is the liquid component of blood.** 2. **Ions distribution across a cell membrane?** - **High concentration of Na+, Cl-, and Ca++ outside; high K+ concentration inside.** - **Maintained by the cell membrane and Na+/K+ pump.** 3. **Differences in chemical composition of fluids?** - **The cell membrane regulates ion movement, keeping distinct compositions between compartments.** 4. **Permeability of the lipid bilayer?** - **Critical for maintaining homeostasis by controlling what enters and exits the cell.** 5. **Functions of membrane proteins?** - **Cell Identity Marker** - **Cell Surface Receptor** - **Ion Channel** - **Transporters** - **Enzymes** - **Cell-Cell Adhesion Proteins** 6. **Ways substances cross membranes?** - **Simple Diffusion: Movement from high to low concentration.** - **Facilitated Diffusion: Requires transport proteins, no energy.** - **Pumps: Move molecules against concentration gradients, requiring energy.** - **Endocytosis: Engulfing large molecules into the cell.** - **Exocytosis: Packaging large molecules in vesicles for release.** **Summary** - **Different body compartments have unique ion distributions, but solute concentrations are similar.** - **Membrane proteins play vital roles in maintaining cell function and transporting substances.** **Lesson 3 of 4: Osmosis** **Overview** - **Focus on water movement across cell membranes.** **Key Questions** 1. **What is osmosis?** - **Movement of water across a semi-permeable membrane down its concentration gradient.** 2. **Factors affecting water movement across membranes?** - **Permeability of the membrane, solute concentration, and pressure gradient.** 3. **Units of osmosis?** - **Osmolality: Osmoles per kg of water.** - **Osmolarity: Osmoles per liter of water.** 4. **Differences between isotonic, hypertonic, and hypotonic solutions?** - **Isotonic: No net movement of water.** - **Hypertonic: Water moves out of cells, causing them to shrink.** - **Hypotonic: Water moves into cells, causing them to swell.** 5. **Factors affecting the rate of movement through the cell membrane?** - **Concentration gradients, electrical gradients, molecule solubility, size, surface area, and membrane composition.** **Summary** - **Osmosis is a passive process that affects cellular function.** - **Tonicity is essential for determining water movement in cells, impacting clinical treatments.** **Lesson 4 of 4: Resting Membrane Potential** **Overview** - **Focus on the electrical charge across cell membranes at rest.** **Key Questions** 1. **What is resting membrane potential and its significance?** - **Electrical charge difference across the membrane, typically around -70 mV.** - **Essential for nerve communication and muscle contraction.** 2. **Forces acting on ions distributed across a cell?** - **Concentration gradients and electrical gradients create an electrochemical gradient.** 3. **Electrochemical equilibrium potentials for Na+ and K+?** - **K+: typically around -90 mV; Na+: around +60 mV.** 4. **Function of the Na+/K+ pump?** - **Actively transports Na+ out and K+ into the cell to maintain ion gradients.** **Summary** - **Resting membrane potential is crucial for cellular functions.** - **Electrochemical gradients influence ion movement, critical for nerve and muscle function.** - **The Na+/K+ pump is vital for maintaining ion distributions and membrane potential.** **Week 2 - Excitable Cells (Updated Sept. 18)** **Lesson 1 of 4: The Excitable Cells of the Nervous System** **Overview** - **Focus on the structure of excitable cells in the nervous system and their communication.** - **Understanding how information propagates from one neuron to another, enabling actions like typing or jumping.** **Learning Questions** 1. **What is an excitable cell and how is it different from a non-excitable cell?** - **Excitable Cells: Can generate action potentials (e.g., neurons, muscle cells).** - **Non-excitable Cells: Do not generate action potentials.** 2. **What is the anatomy of a neuron?** - **Soma: Cell body containing the nucleus and organelles.** - **Dendrites: Projections that receive signals from other neurons.** - **Axon: Transmits action potentials away from the soma.** - **Axon Terminals: Release neurotransmitters to communicate with other cells.** - **Myelin Sheath: Insulating layer around the axon that speeds up transmission.** - **Schwann Cell: Cell that produces myelin and maintains neuron health.** - **Nodes of Ranvier: Gaps in the myelin sheath rich in ion channels, facilitating rapid conduction.** 3. **What are voltage-dependent or voltage-gated sodium and potassium channels?** - **Channels that open in response to changes in membrane potential, essential for action potential generation.** 4. **What is an action potential?** - **An electrochemical impulse generated by depolarization of the neuron.** 5. **How do excitable cells communicate through action potentials?** - **Action potentials propagate along the neuron, enabling communication with adjacent cells.** 6. **What are the main components of an action potential?** - **Depolarization: Na+ channels open, allowing Na+ to enter, making the inside of the cell more positive.** - **Repolarization: K+ channels open, allowing K+ to exit, returning the cell to a more negative state.** - **Hyperpolarization: The cell becomes more negative than the resting potential, making it harder to trigger another action potential.** - **Resting Stage: Resting membrane potential is restored (-70 mV).** **Key Concepts** - **Resting Membrane Potential (RMP): Maintained by sodium, potassium, and calcium distributions across the cell membrane.** - **Salty Banana Analogy: Refers to the higher concentration of K+ inside the cell and Na+ outside.** **Phases of Action Potential** 1. **Threshold: A stimulus must reach -55 mV to trigger an action potential.** 2. **Depolarization: Na+ influx raises the membrane potential, driving it towards +35 mV.** 3. **Repolarization: K+ efflux returns the potential towards resting levels.** 4. **Hyperpolarization: Membrane potential dips below resting level, entering the relative refractory period.** 5. **Resting State: RMP restored.** **Important Notes** - **Voltage-Gated Channels: Open due to voltage changes; Na+ channels open first during depolarization.** - **Absolute Refractory Period: No new action potential can occur; Na+ channels are inactive.** - **Relative Refractory Period: A stronger stimulus is needed to generate another action potential due to hyperpolarization.** **Lesson 2 of 4: Propagation of an Action Potential** **Overview** - **Focus on how action potentials propagate along neurons.** **Learning Questions** 1. **What is the structure of a neuron? (Refer to Lesson 1 for details)** 2. **What is the direction in which an action potential propagates?** - **From dendrites → soma → axon → axon terminals.** 3. **What is saltatory conduction and why is it advantageous?** - **Saltatory conduction occurs in myelinated neurons where action potentials jump between nodes of Ranvier, significantly speeding up transmission.** 4. **What is the all-or-nothing principle of an action potential?** - **An action potential either occurs fully or not at all once the threshold is met.** 5. **What determines the direction of propagation of an action potential?** - **The refractory periods prevent backward propagation, ensuring unidirectional flow.** **Key Concepts** - **Myelination vs. Unmyelination: Myelinated axons conduct action potentials faster due to saltatory conduction.** - **AP Propagation: Depolarization increases the likelihood of an action potential; hyperpolarization decreases it.** **Lesson 3 of 4: Neurons and Glial Cells** **Overview** - **Explore the types of cells in the brain and their relationships to neurons, including pathologies.** **Learning Questions** 1. **What are glial cells?** - **Non-neuronal cells that support and protect neurons, comprising about 90% of the brain.** 2. **What are different types of neurons present in the brain?** - **Bipolar Neurons: Two processes; found in the retina.** - **Unipolar Neurons: One process; sensory neurons in peripheral nerves.** - **Multipolar Neurons: Many dendrites; most common in the CNS.** 3. **What are some of the functions that glial cells perform?** - **Provide support, nutrients, insulation, and defense for neurons.** 4. **How do different pathologies impact the nervous system?** - **Multiple Sclerosis (MS): Autoimmune disease that damages myelin, interrupting action potential propagation.** **Key Concepts** - **Central Nervous System (CNS): Comprises the brain and spinal cord.** - **Peripheral Nervous System (PNS): Connects CNS to muscles and organs.** - **Neuronal Connections: Essential for processing information and forming communication networks.** **Lesson 4 of 4: The Brain** **Overview** - **Focus on the anatomical and functional structures of the brain and their roles in communication.** **Learning Questions** 1. **Contrast and compare the central and peripheral nervous systems.** - **CNS: Brain and spinal cord; PNS: Nerves to muscles and organs.** 2. **What are the functional and anatomical regions of the brain?** - **Contains multiple lobes with specific functions, connected via gyri and sulci.** 3. **What are the two main types of brain cells?** - **Neurons and glial cells.** 4. **What are some pathologies that can impact cell-to-cell communication in the brain?** - **Conditions like MS affecting myelination.** **Key Concepts** - **Brain Facts:** - **Contains 10-100 billion cells, weighing about 1.5 kg.** - **Action potentials can travel at speeds up to 300 m/s.** - **Basic Structures:** - **Cerebral hemispheres, gyri, sulci, and key regions responsible for various functions (e.g., motor control, sensory processing).** - **Pituitary Gland: Regulates endocrine functions and hormones, communicating long-distance signals throughout the body.** **Week 3 - Synaptic Transmission and the NMJ (Updated Oct. 2)** **Lesson 1 of 4: Synaptic Transmission** **Overview** - **Focus on how neurons communicate with each other using neurotransmitters at the synapse.** **Learning Questions** 1. **What is a synapse?** - **The site where neurons communicate; it can be electrical (direct ion exchange) or chemical (release of neurotransmitters).** 2. **What are the different components of the synapse?** - **Pre-synaptic Neuron: Transmits information towards the synapse.** - **Synaptic Cleft: Small space between neurons.** - **Post-synaptic Neuron: Receives information from the synaptic cleft.** 3. **What are the events at the chemical synapse?** - **Action potential (AP) reaches the axon terminal.** - **Voltage-gated Ca²⁺ channels open; Ca²⁺ enters the cell.** - **Synaptic vesicles fuse with the pre-synaptic membrane, releasing neurotransmitters.** - **Neurotransmitters bind to receptors on the post-synaptic membrane.** 4. **What are the fates of neurotransmitters at the synapse?** - **Bind to post-synaptic receptors.** - **Diffuse out of the synapse.** - **Be broken down by enzymes.** - **Be reabsorbed into the pre-synaptic neuron for recycling.** 5. **How does the release of neurotransmitters end at the synapse?** - **Enzymatic degradation or reuptake into the pre-synaptic neuron.** **Key Concepts** - **Chemical Synapse: Neurotransmitters are released to communicate; different from electrical synapses that use direct ion exchange.** - **Neurotransmitters: Chemicals that bind to receptors on the post-synaptic neuron, leading to depolarization or hyperpolarization.** **Lesson 2 of 4: Excitatory and Inhibitory Synapses** **Overview** - **Focus on how neurons integrate information and how neurotransmitters influence action potential generation.** **Learning Questions** 1. **What are graded potentials?** - **Changes in membrane potential that vary in magnitude and can lead to action potentials.** 2. **What are the differences between EPSPs and IPSPs?** - **EPSPs (Excitatory Post-Synaptic Potentials):** - **Depolarizing, bring neuron closer to action potential.** - **Localized and graded.** - **Summable; required to reach threshold for action potential.** - **IPSPs (Inhibitory Post-Synaptic Potentials):** - **Hyperpolarizing, move neuron away from action potential.** - **Localized and graded.** - **Summable; prevent action potential.** 3. **What is unique about graded potentials that allows them to elicit an action potential?** - **Graded potentials can sum together (temporal or spatial summation) to reach the threshold at the axon hillock.** 4. **What is spatial and temporal summation?** - **Temporal Summation: Multiple EPSPs from the same synapse over time.** - **Spatial Summation: Multiple EPSPs from different synapses occurring simultaneously.** 5. **What are the main types of neurotransmitters, with examples?** - **Acetylcholine: Muscle control, excitatory (CNS and PNS).** - **Catecholamines (e.g., epinephrine, norepinephrine, dopamine): Excitatory.** - **Serotonin: Inhibitory (mood regulation).** - **Glutamate: Excitatory (memory).** - **GABA: Inhibitory (CNS).** - **Neuropeptides (e.g., endorphins): Inhibitory (pain relief).** **Key Concepts** - **Threshold for Action Potential: Achieved when the sum of EPSPs exceeds the threshold at the axon hillock.** - **All-or-Nothing Response: An action potential is generated only if the threshold is met.** **Lesson 3 of 4: The Neuromuscular Junction** **Overview** - **Focus on the site where neurons communicate with skeletal muscle.** **Learning Questions** 1. **What are the events at the neuromuscular junction (NMJ)?** - **AP propagates to the axon terminal.** - **Voltage-gated Ca²⁺ channels open; Ca²⁺ enters.** - **Synaptic vesicles fuse and release acetylcholine (ACh).** - **ACh binds to receptors on the muscle cell, causing depolarization.** 2. **What are the modes of chemical transmission at the synapse?** - **Release of neurotransmitters (e.g., ACh) that bind to receptors and trigger cellular responses.** 3. **What do we mean by end-plate potential?** - **Depolarization of the muscle cell membrane caused by ACh binding to nicotinic receptors.** 4. **What are the ways that acetylcholine communicates information in the body?** - **Acts on ligand-gated nicotinic receptors for fast transmission and on muscarinic receptors for slower transmission.** **Key Concepts** - **Acetylcholine: Key neurotransmitter at the NMJ that depolarizes muscle cells.** - **Nicotinic vs. Muscarinic Receptors:** - **Nicotinic receptors are ionotropic (fast response).** - **Muscarinic receptors are metabotropic (slower response through G-protein activation).** **Lesson 4 of 4: Pathology of the NMJ** **Overview** - **Focus on myasthenia gravis and its impact on the neuromuscular junction.** **Learning Questions** 1. **What is myasthenia gravis?** - **A chronic autoimmune neuromuscular disease characterized by weakness in skeletal muscles due to antibodies blocking nicotinic receptors.** 2. **What are the effects at the neuromuscular junction?** - **Decreased number of functional nicotinic receptors, leading to muscle weakness.** 3. **What are the symptoms of myasthenia gravis?** - **Muscle weakness, fatigue, especially in muscles that control eye and eyelid movement.** 4. **What are the therapeutic approaches to myasthenia gravis?** - **Administration of acetylcholinesterase blockers to increase ACh availability at the NMJ.** **Key Concepts** - **Antibody Action: Antibodies against nicotinic receptors reduce ACh binding, leading to muscle weakness.** - **Therapeutic Goal: Improve neuromuscular transmission by prolonging ACh action in the synaptic cleft.** **Week 4 - Skeletal Muscle** **Lesson 1 of 4: Structure of Skeletal Muscle** **Overview** - **Focus on the structure of the skeletal muscle cell and its components that allow movement.** **Learning Questions** 1. **What are the structural components of the skeletal muscle?** - **Answer: Skeletal muscle consists of muscle fibers, myofibrils, sarcomeres, and connective tissue layers.** 2. **What is the difference between the thick and the thin myofilaments?** - **Answer: Thick myofilaments are primarily composed of myosin, while thin myofilaments are mainly composed of actin.** 3. **What is a sarcomere?** - **Answer: The sarcomere is the basic contractile unit of muscle fibers, defined by the Z-lines and containing thick and thin filaments.** 4. **What happens to the sarcomere during a muscle contraction?** - **Answer: The sarcomere shortens as thick and thin filaments slide past each other during contraction.** **Neuromuscular Junction Review** - **Motor neuron releases acetylcholine (ACh) at the neuromuscular junction, eliciting an action potential in the muscle cell, leading to contraction.** **Structure of Skeletal Muscle** - **Skeletal muscle is organized into bundles for uniform contraction and maximal power generation.** **Skeletal Muscle Bundles** - **A whole muscle (e.g., bicep) is made of bundles called fascicles, which contain muscle cells (muscle fibers).** - **Muscle fiber characteristics:** - **Long and cylindrical (1-12 cm in length).** - **Striated appearance (banding pattern).** - **Multinucleated with many mitochondria.** **Structure of Skeletal Muscle Fiber** - **Sarcolemma: Plasma membrane of the muscle cell.** - **Transverse Tubules (T-tubules): Indentations in the sarcolemma.** - **Sarcoplasmic Reticulum (SR): Network surrounding myofibrils; terminal cisternae store calcium.** - **Triad: T-tubules and terminal cisternae.** **Myofibrils** - **Composed of myofilaments (proteins) that give skeletal muscle its striated appearance.** - **Thin Myofilament:** - **Composed of actin, tropomyosin, and troponin.** - **Actin: Globular proteins forming helical strands.** - **Tropomyosin: Covers myosin binding sites at rest.** - **Troponin: Complex that binds calcium and regulates tropomyosin position.** **The Sarcomere** - **Contractile unit of myofibrils made of alternating thick and thin filaments.** - **Divided into bands/zones:** - **Z-line: Structural proteins separating sarcomeres.** - **M-line: Support for thick myofilaments.** - **I-band: Thin myofilaments only.** - **A-band: Thick myofilaments with varying overlap with thin.** - **H-band: Distance between two thin myofilaments.** **Lesson 2 of 4: Sliding Filament Theory and Excitation-Contraction Coupling** **Overview** - **Relationship between muscle cell excitation and contraction.** **Learning Questions** 1. **What is the sliding filament theory?** - **Answer: The sliding filament theory explains that muscle contraction occurs when thin and thick filaments slide past each other, shortening the sarcomere.** 2. **How does excitation-contraction coupling occur?** - **Answer: It occurs when an action potential leads to calcium release from the sarcoplasmic reticulum, enabling cross-bridge formation and contraction.** 3. **What is the role of calcium in muscle contraction?** - **Answer: Calcium binds to troponin, causing tropomyosin to move and expose myosin-binding sites on actin filaments.** 4. **What role does ATP play in excitation-contraction coupling?** - **Answer: ATP binds to myosin, allowing the myosin head to detach from actin and re-cock for another contraction cycle.** 5. **What happens during rigor mortis?** - **Answer: Rigor mortis occurs after death due to lack of ATP, preventing detachment of actin-myosin cross-bridges and causing muscle stiffness.** **Sliding Filament Theory** - **Sarcomere shortens during contraction due to increased overlap of thin and thick myofilaments.** - **Power Stroke: Myosin head binds to actin and pulls thin filaments toward the M-line.** **Excitation-Contraction Coupling** - **Occurs when an action potential leads to calcium release from the sarcoplasmic reticulum, enabling cross-bridge formation and contraction.** **Role of ATP in Excitation-Contraction Coupling** - **ATP binds to myosin head, breaking the actin-myosin cross-bridge and allowing the cycle to continue.** - **ATP Hydrolysis: Activates the myosin head for binding to actin.** **Rigor Mortis** - **Occurs after death due to lack of ATP:** - **No ATP = No detachment of actin-myosin cross-bridges.** - **Calcium remains available, leading to muscle stiffness.** **Lesson 3 of 4: The Motor Unit and Graded Muscle Contractions** **Overview** - **How a muscle generates power through motor unit recruitment and twitch summation.** **Learning Questions** 1. **What is a motor unit?** - **Answer: A motor unit comprises a motor neuron and all muscle fibers it innervates.** 2. **What is a muscle twitch?** - **Answer: A muscle twitch is a contraction in response to one action potential, lasting 10 ms to 100 ms.** 3. **How does the muscle generate power through motor unit recruitment and twitch summation?** - **Answer: The muscle generates more power by recruiting additional motor units and summing individual twitches for a stronger overall contraction.** 4. **What is muscle tetanus?** - **Answer: Muscle tetanus is a sustained contraction resulting from rapid stimulation, where twitches combine without relaxation.** **Motor Unit** - **Comprises a motor neuron and all muscle fibers it innervates.** - **One action potential in the motor neuron leads to action potentials in all innervated muscle fibers.** **Muscle Twitch** - **A contraction in response to one action potential; lasts 10 ms to 100 ms.** - **Phases of a muscle twitch:** - **Latent Period: Delay before tension is measured.** - **Contraction Period: Tension generation through cross-bridge cycling.** - **Relaxation Period: Return to normal length.** **Grading Muscle Contraction** - **Increased muscle contraction force through motor unit recruitment and twitch summation.** - **Motor Unit Recruitment: More motor units are activated with increased load.** - **Motor units fire asynchronously to ensure smooth muscle contractions.** **Summation** - **Increased action potential frequency leads to muscle twitches stacking up:** - **Unfused Tetanus: Partial relaxation occurs between twitches.** - **Complete Tetanus: No relaxation; sustained contraction occurs.** **Lesson 4 of 4: Integration Lecture - Lab Activity** **Lab Activity** - **Use the video \"Laboratory exercise - EMG\" to answer the following questions:** 1. **Where were the electrodes placed and why?** - **Answer: The electrodes were placed on the skin over the muscle to detect electrical activity during contraction.** 2. **Why did the muscle respond at 3 mAmp but not at 1 mAmp?** - **Answer: The muscle responded at 3 mAmp because it reached the threshold needed to generate an action potential, while 1 mAmp was too weak.** 3. **Did the mAmp value change after frequency increase?** - **Answer: Yes, increasing the frequency typically led to greater muscle tension or response.** 4. **What happened to twitches with increased frequency? Explain in terms of contraction and relaxation.** - **Answer: As frequency increased, twitches became stronger and less relaxed, leading to a more sustained contraction.** 5. **Was complete tetanus reached? Justify.** - **Answer: Yes, complete tetanus was reached if the muscle maintained a steady contraction without visible relaxation.** 6. **What happened to muscle tension with further frequency increase?** - **Answer: Muscle tension increased with further frequency increases until a plateau was reached.** **Summary Questions** - **Reflect on the muscle movement captured in technology and its implications for various fields, including healthcare and entertainment.** **Week 5 - Somatic Motor and Autonomic Nervous Systems (Oct. 7)** **Lesson 1 of 4: Somatic Motor System** **Overview** - **Focus on brain areas that coordinate movement.** **Learning Questions** 1. **What is the somatic motor system?** - **Answer: The somatic motor system is responsible for voluntary muscle movements and reflexes.** 2. **What is the basic structure and organization of the somatic motor system?** - **Answer: It includes the motor cortex, spinal pathways, motor neurons, and muscle receptors.** 3. **What is the role of the corticospinal tract in movement?** - **Answer: The corticospinal tract transmits motor signals from the brain to the spinal cord, influencing voluntary muscle movements.** **The Somatic Motor System** **Basic Structure and Organization** - **Neurons communicate with muscles to perform voluntary movements.** - **Involves areas of the brain responsible for activating muscles, spinal tracts sending information to muscles, and muscles sending sensory information back to the brain.** **Somatic Motor System Defined** - **Also called the somatic nervous system, part of the peripheral nervous system (PNS).** - **Coordinates voluntary movement in response to the environment.** - **Main function: allows movement and control of skeletal muscles.** - **Involves motor neurons with cell bodies in the central nervous system (CNS) that communicate with skeletal muscle at the neuromuscular junction.** **Components of the Somatic Motor System** - **Motor Cortex: Includes the supplementary motor area, premotor area, and primary motor cortex.** - **Basal Ganglia** - **Spinal Pathways** - **Motor Nerves to Muscles** - **Muscle Receptors** **Brain Areas Responsible for Activation and Control of Muscles** - **Motor Cortex** - **Premotor Cortex** - **Supplementary Motor Area** - **Primary Motor Cortex** - **Motor Homunculus** - **Primary Somatosensory Cortex** **Knowledge Check** - **Match brain regions with their functions:** - **Directs motor behavior and behavioral decisions** - **Programs motor sequences and fine motor control** - **Activates appropriate muscles to perform an action** - **Map of the body** **Lesson 2 of 4: Muscle Spindles and the Reflex Arc** **Overview** - **Discusses how skeletal muscle fibers respond to the brain to inform it about their position and ability to perform actions.** **Learning Questions** 1. **What is proprioception?** - **Answer: Proprioception is the ability to sense the position and movement of the body.** 2. **What are muscle spindles and Golgi tendon organs?** - **Answer: Muscle spindles detect changes in muscle length and rate of stretch, while Golgi tendon organs sense muscle tension.** 3. **What is alpha-gamma coactivation?** - **Answer: Alpha-gamma coactivation is the simultaneous activation of alpha and gamma motor neurons to ensure accurate muscle spindle function during contraction.** 4. **What is the reflex arc?** - **Answer: The reflex arc is a neural pathway that controls a reflex action, involving sensory input and motor output without direct involvement of the brain.** 5. **How would you describe the stretch reflex?** - **Answer: The stretch reflex is a rapid response to muscle stretch that causes contraction of the muscle and inhibition of its antagonist.** **Muscle Receptors** - **Proprioception: The ability to sense the position of limbs.** - **Muscle Spindles: Detect muscle stretch, length, and rate of change. Located between skeletal muscle fibers; serve a protective role by sensing overstretch.** - **Golgi Tendon Organs: Detect muscle tension. Located at muscle-tendon junction; protect from overload during forceful activities.** **Muscle Spindles** - **Composed of 6-8 specialized intrafusal fibers that signal changes in length and velocity.** - **The sensory region of muscle spindles stretches during whole muscle stretching, triggering action potentials that send signals back to the brain.** **Golgi Tendon Organs** - **Located between muscle fibers and tendon; signal load or force applied to the muscle.** - **Trigger action potentials in response to muscle tension.** **Alpha-Gamma Coactivation** - **Sensory Innervation of Muscle Spindles:** - **Primary Afferents (Ia): Information about length changes and velocity.** - **Secondary Afferents (II): Information about changes in length only.** - **Gamma Motor Neurons: Innervate intrafusal fibers; keep muscle spindle sensitive to stretch.** **Knowledge Check** - **Describe the roles of:** - **Primary afferens: Sends information about muscle length changes and velocity to the CNS.** - **Secondary afferens: Provides information about muscle length only.** - **Gamma motor neuron: Maintains sensitivity of the muscle spindle by innervating intrafusal fibers.** - **Alpha motor neuron: Innervates extrafusal muscle fibers to produce muscle contractions.** - **Muscle spindle: Detects muscle stretch and sends sensory feedback to the CNS.** - **Golgi tendon organ: Senses muscle tension and prevents excessive force.** **The Reflex Arc** - **Involves afferent pathways (sensory) and efferent pathways (motor) that enable rapid response without brain involvement.** - **Components of the reflex arc include sensory receptors, sensory neurons, interneurons, motor neurons, and effector organs (e.g., skeletal muscle).** **The Stretch Reflex** - **Example of a reflex arc; occurs when tapping the patellar tendon:** - **Stretching of muscle triggers action potential in sensory neuron.** - **Afferent neuron synapses onto motor neuron in the spinal cord.** - **Quadriceps contract while hamstring relaxes (reciprocal innervation).** **Lesson 3 of 4: Cerebellum and the Limbic System** **Overview** - **Examines the cerebellum and limbic system\'s role in movement, conditioning, homeostasis, pleasure, pain, and motivation.** **Learning Questions** 1. **What is the cerebellum and its role in integrating information?** - **Answer: The cerebellum processes sensory input and motor commands to coordinate movement and maintain balance.** 2. **What are the components of the limbic system?** - **Answer: The limbic system includes structures such as the amygdala, hippocampus, and hypothalamus, which are involved in emotion and memory.** 3. **How is body temperature regulated?** - **Answer: Body temperature is regulated through mechanisms controlled by the hypothalamus, responding to internal and external temperature changes.** **The Cerebellum** - **Integrates motor information from the motor cortex and proprioceptors to ensure accurate limb movement and corrections.** - **Plays a role in learning new muscle movements and vestibular ocular reflex (VOR).** **The Limbic System** - **Emotional center of the brain; coordinates autonomic, hormonal, and motor effects.** - **Components include the hypothalamus, which regulates homeostasis and hormone release.** **Knowledge Check** - **Identify the function of different structures in the limbic system.** **The Hypothalamus** - **Regulates body temperature, food intake, cardiovascular functions, and emotional behaviors.** - **Functions through negative feedback control mechanisms.** **Temperature Control** - **The hypothalamus detects temperature changes and initiates mechanisms (sweating, vasodilation) to return to set point (\~37°C).** - **In case of fever, the set point rises to combat infections, leading to mechanisms that conserve heat (shivering, vasoconstriction).** **Lesson 4 of 4: Autonomic Nervous System (ANS)** **Overview** - **Focuses on the autonomic nervous system, which monitors the body\'s internal environment.** **Learning Questions** 1. **What are the divisions of the ANS?** - **Answer: The ANS has two main divisions: the sympathetic division (SYN) and the parasympathetic division (PSYN).** 2. **What are the similarities and differences between the two divisions of the ANS?** - **Answer: Both divisions have preganglionic and postganglionic neurons, but they differ in functions and neurotransmitters used.** 3. **What are the neurotransmitters involved in signaling in the two divisions of the ANS?** - **Answer: The main neurotransmitter for the sympathetic division is norepinephrine, while the parasympathetic division primarily uses acetylcholine.** 4. **What are the functions of the two divisions of the ANS?** - **Answer: The sympathetic division prepares the body for \"fight or flight\" responses, while the parasympathetic division promotes \"rest and digest\" activities.** **Overview of the Nervous System** - **Consists of the CNS (brain and spinal cord) and PNS (nerves to muscles and organs).** - **PNS divided into somatomotor (voluntary movement) and autonomic (involuntary control).** **Divisions of the ANS** - **Sympathetic Division (SYN): Activates fight or flight functions (increases heart rate, blood pressure, and airway dilation).** - **Parasympathetic Division (PSYN): Responsible for rest and relaxation functions (slows heart rate, promotes digestion).** **Organization of the ANS** - **Maintains homeostasis through sensory receptors in viscera sending information to the CNS.** - **The hypothalamus acts as a control center, sending commands via efferent pathways to target organs.** **Common Characteristics of Motor Pathways** - **Both divisions have preganglionic neurons in the CNS, autonomic ganglia, postganglionic neurons, and target organs.** **Differences in Motor Pathways** **Sympathetic Division (SYN)** **Parasympathetic Division (PSYN)** --------------------------------------------------------- --------------------------------------------------- **Nerves exit spinal cord in thoracic/lumbar regions** **Nerves exit at brain stem/lower sacral region** **Short preganglionic neuron** **Long preganglionic neuron** **Ganglion closer to CNS** **Ganglion closer to target organ** **Longer unmyelinated postganglionic neuron** **Shorter unmyelinated postganglionic neuron** **Main neurotransmitters: norepinephrine, epinephrine** **Neurotransmitter: acetylcholine** **Neurotransmitters of the ANS** - **Acetylcholine (ACh): Released by preganglionic neurons in both divisions; binds to nicotinic receptors in ganglia and muscarinic receptors in target organs.** - **Norepinephrine: Predominantly used in the sympathetic division, with exceptions in sweat glands.** **Knowledge Check** - **Match structures of the ANS with their characteristics.**