Phisio Exam 2 Review PDF

Aubriel Ruiz Oct. 8, 2024 Chapter 4: Neural Pathways 1. Resting Membrane Potential Resting potential: ~ -70 mV (range -40 to -90 mV). Positive outside, negative inside. Ion distribution: High [Na+] outside, high [K+] inside. Excitable tissues (nerve, m...

Aubriel Ruiz Oct. 8, 2024 Chapter 4: Neural Pathways 1. Resting Membrane Potential Resting potential: ~ -70 mV (range -40 to -90 mV). Positive outside, negative inside. Ion distribution: High [Na+] outside, high [K+] inside. Excitable tissues (nerve, muscle): Capable of changing their membrane potentials to generate signals. 2. Electrical States of Membranes Polarization: Any potential other than 0 mV. Depolarization: Less negative (closer to 0). Repolarization: Returning to resting potential after depolarization. Hyperpolarization: More negative than the resting potential. 3. Types of Signals Graded potentials: Short distance signals. Action potentials: Long distance, all-or-none signals. 4. Ion Permeability & Membrane Potential Depolarization: Positive ions (Na+) enter the cell. Repolarization: Positive ions (K+) leave the cell. Hyperpolarization: Further exit of positive ions (K+) or entry of negative ions (Cl-). 5. Graded Potentials Local, short-lived changes in membrane potential. Graded according to the strength and duration of the triggering event. Spread is decremental: They fade over short distances. Examples: Postsynaptic potentials, receptor potentials. 6. Action Potentials  Threshold (~ -55 mV): If reached, an action potential is triggered. Phases: 1. Depolarization: Na+ rushes into the cell (+30 mV). 2. Repolarization: K+ rushes out, restoring negative potential. 3. Hyperpolarization: K+ channels remain open slightly too long. Refractory period: Prevents another action potential from occurring too soon. 7. Conduction of Action Potentials Saltatory conduction: In myelinated axons, action potentials "jump" between Nodes of Ranvier, speeding up transmission. Myelin formation: ○ CNS: Oligodendrocytes. ○ PNS: Schwann cells. Larger axon diameter = faster conduction. 8. Synapses Electrical synapses: Rare, direct electrical coupling of cells. Chemical synapses: More common, involve neurotransmitter release across a synaptic cleft. Steps: 1. Action potential reaches presynaptic terminal. 2. Ca²⁺ influx triggers neurotransmitter release. 3. Neurotransmitters bind to receptors on postsynaptic membrane. 4. Can either excite (EPSP) or inhibit (IPSP) the postsynaptic neuron. 9. Neurotransmitters Chemical types: ○ Acetylcholine (ACh): Neuromuscular junctions. ○ Biogenic amines: Epinephrine, serotonin (emotion-related). ○ Amino acids: GABA (inhibitory), glycine. ○ Peptides: Endorphins (pain and digestion). Functionally: ○ Excitatory: Depolarizes postsynaptic cell. ○ Inhibitory: Hyperpolarizes postsynaptic cell. 10. Summation Temporal summation: Multiple signals from the same neuron over time.  Spatial summation: Signals from multiple neurons. 11. Drugs & Diseases Affecting Synapses Cocaine: Blocks dopamine reuptake. Parkinson’s disease: Dopamine deficiency. Strychnine: Blocks glycine, leading to overstimulation. Tetanus toxin: Prevents GABA release, leading to muscle rigidity. Key Concepts for Focus: Understand the phases of the action potential. Know how graded potentials differ from action potentials. Memorize ion movements during depolarization, repolarization, and hyperpolarization. Learn the steps involved in neurotransmitter release and synaptic transmission. Chapter 5: Central and Peripheral Nervous System Nervous vs. Endocrine Systems Nervous System: Sends electrical signals through specific pathways to skeletal muscles and exocrine glands. Rapid, precise, and short-lived effects. Endocrine System: Secretes hormones into the blood, targeting distant organs. Slower, long-lasting effects. Target Cells: Neurons affect specific cells via neurotransmitters. Hormones act on cells with specific receptors. Nervous System Overview Two main branches: 1. Central Nervous System (CNS): Brain and spinal cord. 2. Peripheral Nervous System (PNS): Includes sensory (afferent) and motor (efferent) divisions. The motor division includes: Somatic Nervous System: Controls skeletal muscles. Autonomic Nervous System: Controls smooth/cardiac muscles and glands, with sympathetic and parasympathetic branches. Neuron Types 1. Afferent Neurons: Carry signals to CNS from sensory receptors. 2. Efferent Neurons: Carry signals from CNS to muscles/organs. 3. Interneurons: Entirely within the CNS, connecting afferent and efferent neurons. Glial Cells Astrocytes: Support neurons, maintain the blood-brain barrier, repair brain injuries. Oligodendrocytes: Form myelin in CNS. Microglia: CNS immune defense, act as macrophages. Ependymal Cells: Line CNS cavities, help circulate cerebrospinal fluid (CSF). CNS Protection Meninges: Three layers surrounding the CNS: dura mater, arachnoid mater, and pia mater. Cerebrospinal Fluid (CSF): Cushions the brain and spinal cord, circulates in ventricles, drains into the blood through arachnoid villi. Blood-Brain Barrier: Selectively regulates substances entering the brain from blood. Spinal Cord Protected by vertebral column, divided into 31 segments with paired spinal nerves (cervical, thoracic, lumbar, sacral, coccygeal). Gray Matter: Contains neurons for basic reflexes (ventral, lateral, and dorsal horns). White Matter: Contains ascending (sensory) and descending (motor) tracts. Reflexes Reflex Arc Components: 1. Receptor (detects stimulus). 2. Afferent Pathway (transmits signal). 3. Integrating Center (in spinal cord). 4. Efferent Pathway (sends response). 5. Effector (executes response). Examples: Stretch reflex, deep tendon reflex, crossed extensor reflex. These highlights capture the main points for your understanding of the central and peripheral nervous systems, including neuron types, glial cells, CNS protection, and reflex mechanisms.  Chapter 6: PNS, Afferent Division, Special Senses Overview of the PNS The PNS includes nerve fibers that relay information between the CNS (central nervous system) and the body. The afferent division of the PNS transmits sensory information from the body to the CNS. ○ Visceral afferent: subconscious information from internal organs. ○ Sensory afferent: brings information to conscious awareness, including: Somatic sensations (skin, muscles, joints). Proprioception (body position). Special senses (vision, hearing, taste, smell). Perception Perception is the brain’s interpretation of external stimuli from sensory receptors. ○ Human perception does not mirror reality; it is a construct created by the brain. Sensory Receptors Receptors detect stimuli and send signals to the CNS. ○ Classified by stimulus type: Photoreceptors: detect light (vision). Mechanoreceptors: detect mechanical energy (touch, pressure). Thermoreceptors: detect temperature changes (heat, cold). Osmoreceptors: detect changes in body fluid solute concentrations. Chemoreceptors: detect chemicals (e.g., oxygen levels in blood). Nociceptors: detect pain and tissue damage. ○ Classified by location: Exteroceptors: outside body (e.g., skin). Interoceptors: inside body (e.g., organs). Proprioceptors: in muscles, joints (position sense). ○ Classified by structural complexity: Simple: modified dendrites. Complex: special sense organs (e.g., eyes, ears). Receptor Potential and Adaptation Receptor potential: A graded change in membrane potential caused by stimuli.  ○ Increased stimulus intensity leads to a larger receptor potential, which can trigger an action potential. Adaptation: Receptors can adjust to a sustained stimulus. ○ Tonic receptors adapt slowly or not at all (e.g., pain receptors). ○ Phasic receptors adapt quickly (e.g., Pacinian corpuscles for pressure/vibration). Pathways to the CNS Afferent pathways can be part of a reflex arc or travel to the brain via ascending pathways. Somatosensory pathways: transmit conscious sensory information. ○ First-order neurons relay information from receptors to the spinal cord. ○ Second-order neurons carry the signal to the thalamus. ○ Third-order neurons bring the information to the cerebral cortex. Sensory Acuity and Receptive Fields Acuity: The ability to discriminate sensory stimuli. ○ The smaller the receptive field, the greater the acuity. ○ Lateral inhibition enhances sensory acuity by suppressing neighboring signals. Pain Perception and Nociceptors Nociceptors detect and signal pain. ○ Mechanical receptors: activated by physical damage. ○ Thermal receptors: respond to extreme temperatures. ○ Polymodal nociceptors: respond to multiple damaging stimuli. Pain can be transmitted by fast fibers (A-delta, 30 m/s) or slow fibers (C fibers, 12 m/s). The brain processes pain signals through the somatosensory cortex, thalamus, and reticular formation. The brain has an analgesic system that modulates pain. Key Concepts for the Exam Be familiar with the types of receptors and how they respond to different stimuli. Understand the basic afferent pathway, including the role of first, second, and third-order neurons. Focus on the concepts of receptor adaptation and how different receptors behave. Review the pain pathways and how the brain interprets pain stimuli. This structure should help you review key concepts and stay focused on the most important points! Let me know if you'd like to expand on any area.  Chapter 7: PNS, Efferent Divison 1. Autonomic Nervous System (ANS) Overview: Innervates: Cardiac & smooth muscles, exocrine & endocrine glands. Neurotransmitters: Only two are used—acetylcholine (ACh) and norepinephrine. Nerve Pathway: Consists of two neurons: ○ Preganglionic fiber ○ Postganglionic fiber 2. Divisions of the ANS: Sympathetic Nervous System (SNS) ("fight or flight"): ○ Originates from thoracic and lumbar spinal regions. ○ Preganglionic fibers: Short ○ Postganglionic fibers: Long ○ Neurotransmitter: Norepinephrine (adrenergic) ○ Examples of responses: Dilated pupils, increased heart rate, inhibited digestion, increased glucose production. Parasympathetic Nervous System (PNS) ("rest and digest"): ○ Originates from cranial and sacral levels of the CNS. ○ Preganglionic fibers: Long ○ Postganglionic fibers: Short (terminate near organs) ○ Neurotransmitter: Acetylcholine (cholinergic) ○ Examples of responses: Slower heart rate, stimulated digestion, no glucose production from liver. 3. Dual Innervation: Most organs receive signals from both sympathetic and parasympathetic divisions for precise control. Exceptions: Most blood vessels and sweat glands are only innervated by sympathetic nerves. 4. Receptors: Cholinergic receptors (bind ACh): ○ Nicotinic receptors: Found in all autonomic ganglia (between pre- and postganglionic neurons). ○ Muscarinic receptors: Found in parasympathetic postganglionic neurons.  Adrenergic receptors (bind norepinephrine/epinephrine): ○ Alpha receptors: Generally excitatory (alpha 1) or inhibitory (alpha 2). ○ Beta receptors: Beta 1: Excitatory (mainly in the heart). Beta 2: Inhibitory (found in smooth muscles). 5. Drugs: Agonists: Mimic autonomic responses. Antagonists: Block autonomic responses. 6. Somatic Nervous System: Controls voluntary skeletal muscles. One neuron from spinal cord to muscle fiber. Neurotransmitter: Acetylcholine at the neuromuscular junction. 7. Neuromuscular Junction: Action potential reaches the axon terminal → voltage-gated calcium channels open. Calcium influx triggers ACh release by exocytosis. ACh binds to receptors on muscle fiber → sodium channels open → action potential generated in muscle fiber. Acetylcholinesterase breaks down ACh, stopping the signal. 8. Disruptions at Neuromuscular Junction: Toxins: Black widow venom increases ACh release; botulinum toxin blocks it. Curare: Blocks ACh receptors. Focus on understanding these points, especially how the sympathetic and parasympathetic divisions differ, and how neurotransmission works at the neuromuscular junction. Let me know if you need further clarification on any section! Chapter 8: Muscle Phisiology Muscle Structure and Function Muscles only contract and are grouped in opposition. Skeletal muscle fiber: large, elongated, cylinder-shaped cells containing myofibrils. Myofibrils contain thick filaments (myosin) and thin filaments (actin).  Sarcomere: Functional unit of muscle, spanning from one Z line to another. ○ A band: myosin and actin overlap. ○ H zone: middle of A band, no actin. ○ M line: center of A band. ○ I band: only actin. Proteins Involved in Contraction Thick filament: Myosin (with cross bridges and ATPase activity). Thin filament: Actin, troponin, tropomyosin. ○ Tropomyosin: Blocks actin-myosin interaction. ○ Troponin: Binds Ca²⁺ to move tropomyosin out of the way. Sliding Filament Mechanism Myosin binds to actin and pulls it inward (power stroke), shortening the sarcomere. Repeated cycles of cross-bridge attachment/detachment cause muscle contraction. ATP: Needed for myosin to detach from actin and repeat the process. Calcium (Ca²⁺) is essential for contraction; it binds to troponin to enable actin-myosin interaction. Excitation-Contraction Coupling Action potential in a somatic motor neuron triggers acetylcholine release at the neuromuscular junction. This initiates an action potential in the muscle fiber, spreading via T-tubules. Sarcoplasmic Reticulum (SR) releases Ca²⁺ into the cytosol. Ca²⁺ binds to troponin, allowing myosin to bind actin and contract the muscle. Muscle Relaxation Ca²⁺ is reabsorbed into the SR, allowing tropomyosin to block actin again. Motor Units A motor unit consists of one motor neuron and all the muscle fibers it innervates. ○ Small motor units: Delicate movements. ○ Large motor units: Coarse movements. Muscle tension depends on motor unit recruitment and fiber contraction. Muscle Twitch  Phases: Latent, contraction, and relaxation. Twitch summation: Rapid stimuli result in increased tension. Tetanus: Maximal, sustained contraction from rapid stimuli. Types of Contraction Isotonic: Muscle shortens as it lifts a load. Isometric: Muscle doesn't shorten; tension increases. Energy Sources for Contraction Creatine phosphate: Immediate source, short-term. Oxidative phosphorylation: Long-term, aerobic, in mitochondria. Glycolysis: Short-term, anaerobic, produces lactic acid. Muscle Fiber Types Slow oxidative (type I): Endurance, aerobic. Fast oxidative (type IIa): Intermediate. Fast glycolytic (type IIb): Short bursts, anaerobic. Muscle Fatigue Muscle fatigue: Decreased response to stimulation due to lactic acid, inorganic phosphate, or depleted energy. Central fatigue: CNS limits motor neuron activation (often psychological). Muscle Adaptation Endurance exercise enhances oxidative capacity. Resistance training increases muscle size and strength. Muscle atrophy occurs with disuse or denervation. Focus on understanding the sliding filament mechanism, excitation-contraction coupling, muscle twitch, and types of muscle contraction. Good luck studying!