Physiology PDF Study Guide

Contents General and Cellular Physiology  1 Nerve Muscle Physiology  12 Neurophysiology : Part 1  20 Neurophysiology : Part 2  29 Respiratory Physiology : Part 1 ...

Contents General and Cellular Physiology  1 Nerve Muscle Physiology  12 Neurophysiology : Part 1  20 Neurophysiology : Part 2  29 Respiratory Physiology : Part 1  36 Respiratory Physiology : Part 2  43 Cardiovascular Physiology  49 om l.c Gastrointestinal Physiology  60 ai Renal Physiology  gm 68 3@ 12 Endocrine Physiology  78 ir0 av Reproductive Physiology, Exercise Physiology and ag m Regulation of Body Temperature  88 | w ro ar M © © M ar ro w | m ag av ir0 12 3@ gm ai l.c om  General & Cellular Physiology 1 GENERAL & CELLULAR PHYSIOLOGY ----- Active space ----- Homeostasis 00:00:10 Claude Bernard : Coined the term milieu interieu (Internal environment). Walter Cannon : Coined the term homeostasis. Maintenance of homeostasis : Control systems Negative feedback Positive feedback Feed-forward om l.c Increase followed by decrease : Increase followed by increase : Anticipatory changes : ai Eg. Baroreceptor reflex. Eg. CLAPS gm No stimulus. 3@ Clotting. Example : 12 Ca entry into sarcoplasmic - Thinking about ir0 av reticulum. exercising ↑ RR & ↑ HR. ag LH surge. - Body temperature. m | Action potential. w ro Parturition. ar M Shock. © Assessment of effectiveness of negative feedback : Gain = Correction Error left after feedback Error left + Not a good control system. O error left Gain is infinity (Role of kidneys in regulating BP). Cell Membrane 00:09:00 Physiology Revision v4.0 Marrow 8.0 2024  2 Physiology ----- Active space ----- Membrane Lipids : Phospholipids : Phosphatidylcholine/Lecithin/Dipalmitoyl phosphatidylcholine (DPPC) : Present in surfactant. Sphingomyelin : Present in nerve & surfactant. - Lecithin - sphingomyelin ratio : L ≥2 Adequate fetal lung maturity. S Phosphatidylserine (PS) : - Inner surface of cell membrane. - If expressed outside : Eat-me signal Cell undergoes apoptosis. Phosphatidylinositol : Second messenger. Cardiolipin : Mitochondria of heart. Glycolipids : om l.c Types Site Significance ai Cerebrosides CNS gm - 3@ Gangliosides GIT GM-1 gangliosides : Receptors for cholera toxin Fragment B. 12 ir0 av Sterols : Cholesterol (Fluidity buffer) Maintains membrane fluidity. ag m Characteristics of fluidity : | w ro Increased fluidity Decreased fluidity ar M Effect on health Good Bad © Type of fatty acids Unsaturated (Essential) Saturated (Trans) Linoleic acid. Stearic acid. Linolenic acid. Palmitic acid. Arachidonic acid. (Abundant in junk food). Examples Omega-3 fatty acids : Abundant in fish. Membrane Proteins : Transmembrane proteins : Cystic fibrosis transmembrane conductance regulator (CFTR) : Chloride channel. Mutation : Cystic fibrosis. Physiology Revision v4.0 Marrow 8.0 2024  General & Cellular Physiology 3 Peripheral proteins : ----- Active space ----- Cell Protein Diseases due to mutations RBC Spectrin Elliptocytosis (Biconcave disc) Ankyrin Spherocytosis Skeletal muscle Dystrophin Duchenne muscular Dystrophy (DMD) Lipid anchored proteins/GPI anchored protein : Present in RBC only. Examples : CD55 & CD 59 Mutation : Paroxysmal Nocturnal Hemoglobinuria (PNH). Cell Organelles  00:20:10 om l.c ai gm 3@ 12 ir0 av ag m | w Endoplasmic reticulum : ro ar M Rough ER Smooth ER © Granulations + due to ribosomes - Biosynthesis of proteins. Drug detoxification Along with chaperones, aid (By CYP450 in liver). Functions in protein folding. Calcium storage. ER-associated degradation : Steroid biosynthesis. Destruction of misfolded proteins. (Adrenal gland, liver, testis, ovary) Golgi apparatus : Two ends : Cis end/receiving end : Receives protein Post translational modification Vesicles. Trans end/releasing end : Releases vesicles. Lysosomes : Aka suicidal bags/residual bodies. Involved in acid mediated destruction. Enzymes : Acid phosphatase, acid hydrolase. Autophagy : During starvation. Physiology Revision v4.0 Marrow 8.0 2024  4 Physiology ----- Active space ----- Peroxisomes : AKA microbodies. Functions : - Oxidation of long chain & very long chain fatty acids. - Generation & degradation of H2O2 by catalase. - Synthesis of plasmalogens. Peroxisomal disorders : Zellweger syndrome, Refsum disease. Mitochondria : Derived from ovum (Maternal inheritance). Human mitochondrial DNA : Circular dsDNA (16,500 base pairs). Mitochondrial DNA mutations : - > 10 times the rate for nuclear DNA. - Affects organs with high metabolic requirements : om Skeletal muscle, CNS, liver. l.c ai Nucleus : gm Contain blue prints for DNA : Chromosomes. 3@ 12 DNA + histones = Chromatin : Repeating structural unit called nucleosomes. ir0 Nuclear pore complex : Regulates movement of substances in (Importins) & out av ag (Exportins). m | MARKER ENZYMES w ro Cell organelle Marker enzyme ar M © Cell membrane Na+- K+ ATPase Endoplasmic reticulum Glucose-6-phosphatase Golgi apparatus Galactosyl transferase Lysosomes Acid phosphatase Peroxisomes Catalase Mitochondria ATP synthase Nucleus RNA polymerase Cytoskeletal Filaments 00:32:55 Types : Microtubules : Size : Largest. Microtubules Physiology Revision v4.0 Marrow 8.0 2024  General & Cellular Physiology 5 Types ----- Active space ----- kinesin : Tubulin : Dynein : Forward axonal transport Helps in movement of Reverse axonal transport. (Cell body Synapse). chromosomes during (Synapse Cell body) cell division. Motility of cilia (Lung), Microtubule inhibitor drugs : sperm, fallopian tubes. Vincristine, vinblastine , colchicine (Rx : Cancer). Microfilaments : Intermediate filaments : Size : Small Most abundant & Types : Actin & myosin. act as tumor markers. Function : om l.c - Muscle contraction : Sliding filament theory. ai - Cell motility : By actin polymerisation. gm 3@ Eg : Tumbling motility in listeria. 12 ir0 av Microfilaments Intermediate filament ag m Filament Tissue Marker for | w ro Epithelial tissue Epithelial carcinoma Keratin ar Liver (Mallory-Denk bodies) Alcoholic liver disease M © Desmin Muscle Rhabdomyosarcoma Vimentin Connective tissue (Fibroblasts) Mesenchymal tumors Glial fibrillary acidic protein (GFAP) Astrocytes Astrocytoma Lamin Nucleus Progeria (Premature aging) Cellular Junctions 00:40:37 Cell Cell Tight junction Zonula adherens Desmosome Gap junctions Focal adhesions Hemidesmosomes Basal lamina Physiology Revision v4.0 Marrow 8.0 2024  6 Physiology ----- Active space ----- Cell Junctions Protein Characteristics & Clinical importance Cell - Cell junctions Calcium dependent linkages. Zonula adherens Cadherins Linked to actin. Linked to intermediate filaments. Seen in areas of mechanical stress : Skin, Desmoglein. uterine cervix. Desmosomes Antibodies against desmoglein Desmocolins. Pemphigus Vulgaris Occludin - Mutation in claudin Zonula occludens Claudin Familial hypomagnesemia with hypercalciuria & nephrocalcinosis om Connexon Abundant in heart. l.c ai Gap junctions (1 Connexon = Mutations in connexin Cardiac arrythmia. 6 connexins) gm Charcot-Marie-Tooth disease. 3@ Cell basal lamina junctions 12 ir0 Hemidesmosomes - Linked with intermediate filaments av Focal adhesions - Linked with actin ag m | w ro Cellular Messenger & Receptors ar 00:46:47 M © Cellular Messengers/Hormones : Class Examples Tyrosine Catecholamines : - Epinephrine. Amino acid derivatives - Norepinephrine. - Dopamine. Large protein hormones : Protein hormones 51 AA : Insulin. 84 AA : Parathormone. Steroid hormones : Aldosterone, cortisol. Cholesterol derivatives Estrogen, progesterone. Testosterone. Vitamin derivatives Vitamin A & D Physiology Revision v4.0 Marrow 8.0 2024  General & Cellular Physiology 7 Hormone Receptors : ----- Active space ----- Hormone : 1st messenger Hormone Extracellular/cell membrane receptor (Majority of protein hormones) 2nd messenger Nuclear receptor Intracellular receptor Cytoplasmic receptor (Majority of steroid hormones) Types : om Extracellular Intracellular l.c ai gm Cell membrane receptors : Cytoplasmic receptors : Nuclear receptors : 3@ 12 G-Protein coupled Steroid hormone receptors Estrogen receptor. ir0 receptors (Inactive state) in cytoplasm. Vitamin A : Retinoic av ag Receptor tyrosine Hormone + receptor (Inactive) acid receptor (RAR). m kinase (Insulin) Progesterone | w Cytokine family (GH, Activated complex receptor. ro ar Leptin, Erythropoietin) Enters Thyroid hormones. M © Nucleus Examples : - Glucocorticoid receptor. - Mineralocorticoid receptor. - Androgen receptor. - Vitamin D receptor. G protein - coupled receptors (GPCRs) : AKA 7 transmembrane/serpentine receptors. Heterotrimeric : 3 subunits (Alpha, beta, gamma). Mechanism of action : Inactive GPCR Hormone binds α subunit separates Activates GPCR Secondary messengers enters GPCR - Mechanism Physiology Revision v4.0 Marrow 8.0 2024  8 Physiology ----- Active space ----- Second Messengers : 2nd messenger Hormone Function Vasopressin (V2) Water reabsorption cAMP Glucagon Metabolism Secretin Electrolyte (HCO3-)secretion Vasopressin (V1), Endothelin vasoconstriction Calcium Oxytocin Uterine contraction (IP3 - DAG) - Exocytosis Nitric oxide Vasodilatation cGMP Natriuretic peptides Relaxation Membrane Transport Processes 00:58:55 om Passive & Active Transport : l.c ai Passive (No ATP) gm Active (ATP) 3@ Simple diffusion Facilitated diffusion 12 ir0 av ag m | w ro ar M © Types Characteristics Fick’s law : Diffusion - Directly proportional : Membrane surface area, Passive Simple diffusion concentration gradient. transport - Inversely proportional : Membrane thickness. Example : Diffusion of gases in lungs. Facilitated diffusion Carrier proteins : GLUT, aquaporins. Primary Pumps : ATPases active transport Active Cotransporter (Same direction) : SGLT, Na+ I- symporter. transport Exchangers (Opposite direction) : Cl- HCO3- exchanger. Secondary Vesicular transport : Require calcium active transport - Exocytons (SNARE proteins). - Endocytosis (Clathrin, cubilin) Physiology Revision v4.0 Marrow 8.0 2024  General & Cellular Physiology 9 Osmosis : ----- Active space ----- Diffusion of water. Movement : ↑ water concentration/ ↓ Water concentration/ ↓ solute content ↑ solute content Osmolarity (mOsm/L) : 2 x Na+ + 0.055 x Glucose + 0.36 x Blood urea nitrogen (meq/L) (mg/dL) (mg/dL) Concept Of Saturation Kinetics : Saturation kinetics ) Followed by : nite efi - Active transport. Rate (Ind of ion - Facilitated diffusion. rat transport tu sa om Not followed by : Simple diffusion. No l.c ai Concentration of substance gm 3@ Membrane Potentials 01:09:40 12 ir0 Resting Membrane Potential (RMP) : av ag Mechanism : Intracellular ↑ K+ concentration + Extracellular ↓ K+ concentration m | w ro Passive diffusion of k+ out the cell ar M © ↑ Intracellular negative charge (RMP) Hyperkalemia : ↑ Extracellular k+ (↓ diffusion) Depolarized cell (↑ +ve) ↑ Excitable. Hypokalemia : ↓ Extracellular k+ (↑ diffusion) Hyperpolarized cell (↓ +ve) ↓ Excitable. Values : Cell RMP Neuron -70 mV Skeletal muscle -90 mV Cardiac ventricle Sinoatrial node -60 to -40 mV Cajal cell (GIT) (Restless MP : Oscillatory RMP Pre-Botzinger complex as they are pacemakers). Physiology Revision v4.0 Marrow 8.0 2024  10 Physiology ----- Active space ----- Equilibrium Potential : No ion movement. Key : Co E : Equilibrium Nernst equation : Ex = ± 61 log x : Ion Ci Values : Co : Extracellular concentration Ci : Intracellular concentration lon Equilibrium potential Na+ + 60 mV K+ -90 mV Cl - -70 mV (RMP of neuron) Ca2+ + 130 mV Gibbs Donnan Effect : Presence of non-diffusible protein (Anions) affect the distribution of diffusible ions. om X (Inside) M Y (Outside) l.c ai K+ K+ gm Diffusible 3@ Cl- Cl- 12 ir0 Proteins (Anions) Non diffusible av ag m | Cellular Fluids w 01:18:27 ro ar Classification : M Total body water (42 L) : 60% of total body weight © 1/3rd Extracellular fluid (ECF) 2/3rd Intracellular fluid (ICF) (14 L) (28 L). Interstitial fluid Plasma (10.5 L). (3.5 L). Fluid Indicators : Volume Indicators Total body water Deuterium, Tritium Extracellular fluid (ECF) Inulin, sucrose, mannitol Plasma volume (PV) Albumin, Evan’s Blue dye Blood volume (BV) = PV/(1 - Hematocrit) Chromium tagged RBCs Interstitial fluid = ECF - PV Nil Intracellular fluid = TBW - ECF Nil Physiology Revision v4.0 Marrow 8.0 2024  General & Cellular Physiology 11 Dominant Solutes/Ions : ----- Active space ----- ECF ICF Dominant cations Na+ K+ > Mg2+ Dominant anions CI- Phosphates, protein anions Water Loss : Types Sensible water loss Insensible water loss (100 ml/day) (600-700 ml/day) Sweating. Skin. Lungs. om Darrow Yannet Diagram : l.c ai Normal Darrow Yannet diagram. gm 3@ 12 300mOsm/L ir0 (Normal osmolarity) av ag m Y axis 2/3rd 1/3rd | w ro ar M X axis © Normal Darrow Yannet diagram Excessive NaCl intake Hypertension. Volume Osmolarity key : ECF ↑ ↑ Normal ICF ↓ ↑ Disease Darrow Yannet diagram : Hypertension Physiology Revision v4.0 Marrow 8.0 2024  12 ----- Active space ----- NERVE MUSCLE PHYSIOLOGY Nerve  00:00:11 Cells in central nervous system : Neurons : Functional unit. Glial cells : Supporting cells. 1 neuron : 10 glial cells. Glial Cells Classification : Macroglia Microglia om l.c ai gm 3@ 12 ir0 av Macroglia : ag m Astrocytes : | w - Blood-brain barrier. ro ar - Produce neurotrophins : Nourishment for neurons. M © - Synaptic clearing : Takes up excess K+ & neurotransmitters. Oligodendrocytes : CNS Myelination. Schwann cells : PNS Myelination. Microglia : Phagocytosis. Structure of Neuron : (Receiving end) Axon Cell body Node of Ranvier : No myelin. Na+ channels. Conduction Physiology Revision v4.0 Marrow 8.0 2024  Nerve Muscle Physiology 13 Myelin : ----- Active space ----- Lipid component : Sphingomyelin. Protein component : Myelin basic protein. Autoantibody target in multiple sclerosis Demyelination. Use : ↑ Nerve conduction velocity. Factors Affecting Nerve Conduction Velocity (NCV) : Axon diameter : Directly proportional to NCV. Myelination :↑NCV. Temperature : Directly proportional to NCV. ↑Axonal resistance/↓membrane capacitance : ↑NCV. Nerve Action Potential : Phase 1 : Local potential (Slow Na influx) om (-70 mV -55 mV). l.c Phase II : Depolarisation (Opening of voltage gated Na ai channel, fast Na influx). gm Phase III : Repolarisation (K+ efflux). 3@ Phase IV : Hyperpolarisation (Cl- influx & slow closure of K+ 12 channels). ir0 av ARP : From threshold to initial 1/3rd of repolarization. ag Inactivation of Na+ channels. m Second stimulus No response. | w RRP : ro From 1/3rd of repolarization to end of action potential. ar M Second stimulus (Maximum strength). © Action potential Response Classification of Nerve Fibres : Erlanger & Gasser Classification Lloyd Hunt Classification Fiber Diameter Conduction (Only sensory fibres) Myelin Functions type (μm) velocity (m/s) Muscle spindle (Proprioception) 1a Aa Maximum Golgi tendon organ 1b a Motor neurons - Ab + Touch, pressure II Ag Motor to muscle spindles (g motor neuron) - Ad Fast/First pain III B Pre-ganglionic autonomic - C - Minimum Slowest Slow/second pain, Postganglionic sympathetic IV Physiology Revision v4.0 Marrow 8.0 2024  14 Physiology ----- Active space ----- Nerve Injury : Wallerian/Distal degeneration Retrograde/Proximal degeneration Usually begins within 24 hrs after injury Within 36 hours of injury Axon degeneration Myelin sheath Nucleus pushed to periphery degeneration Debris cleared by Destruction of Nissl bodies (RER) Chromatolysis macrophages & Schwann cells Nerve Regeneration : Slow process : Begins after 96 hours of injury. Rate : 1 - 3 mm/day. Identification test : Tinel’s sign : On tapping area over injured nerve Tingling sensation present Nerve is regenerating. om Skeletal Muscle l.c 00:25:12 ai Functional unit : Sarcomere (Between 2 Z lines) gm Proteins Actin. 3@ Myosin. 12 Structure of a sarcomere : ir0 H band : Non-overlapping av part of myosin ag Z line (Boundary) I band (Actin) m | Nebulin : Myomesin (Attaches myosin w ro Regulates length to M-line) ar of actin a-actinin M (Attaches actin to Z-line) © Myosin Actin Titin : Extends from Z to M line M line Feature : Elasticity A-band (Myosin) Skeletal muscle proteins : Contractile proteins Supportive proteins Regulatory proteins Relaxation proteins Titin Ca2+ pump : Actin Troponin Desmin Sarcoplasmic reticulum Myosin Tropomyosin Dystrophin Calcium ATPase (SERCA) Physiology Revision v4.0 Marrow 8.0 2024  Nerve Muscle Physiology 15 Neuromuscular Transmission : ----- Active space ----- Action potential (resting membrane potential = -70mV) Na+ influx & K+ efflux Blockers/Toxins : α-motor neuron 1. Tetradotoxin : (1) Potential drops to -40mV. Present in pufferfish. Na+ 2. Dendrotoxin (2) K+ Sensed by Ca2+ channels 3. Conotoxin (3) 4. Botulinium toxin : Neurotransmitter Ca2+ Ca2+ influx - Blocks release of Ach. - Flaccid paralysis. Exocytosis of Ach vesicles Acetylcholine Ac Ac Ac (Ach) vesicle h h h Ach binds to nicotinic Ach receptors. (4) Ach Ach Ach Nicotinic Ach receptor activated om Na+ influx l.c ai gm Creates end plate potential 3@ Voltage gated Na+ channel 12 K+ channel Summation of crossing threshold ir0 Voltage gated Ca2+ channel av Nicotinic Ach receptor Action potential ag m Muscle contraction. | w Diseases : ro ar Lambert Eaton Myasthenia Syndrome (LEMS) : M © Autoantibodies against voltage gated Ca2+ channels. Myasthenia gravis : Autoantibodies against Nicotinic Ach receptor. Skeletal Muscle Calcium Channels : Dihydropyridine receptor (DHPR) Mechanical interaction. Ryanodine receptor (RYR) Release Ca2+ Contraction. Overactive RYR Malignant hyperthermia. SERCA : Ca2+ storage Muscle relaxation. Physiology Revision v4.0 Marrow 8.0 2024  16 Physiology ----- Active space ----- Molecular Mechanisms of Muscle Contraction : 3. Cross bridge formation 1. Binding of ATP to myosin head 2. ATP hydrolysis Actin-myosin interaction Actin Actin Actin Has ATP ADP+Pi ADP+Pi Myosin Myosin Myosin ATPase Ca2+ head head head activity 45° 90° 90° Myosin Myosin Myosin 5. Detachment of myosin head from 4. Power stroke : Sliding of myosin actin triggered by new molecule of ATP head. Releases ADP+Pi Actin Power stroke Actin ATP Myosin ADP+Pi Myosin om head head l.c 45˚ ai Myosin gm Myosin 3@ 12 ir0 Properties of Skeletal Muscles : av ag Length tension relationship : Tension ∝ actin - myosin overlap. m | Actin myosin overlap Tension generated Image w ro Myosin ar Actin Point D Absent No tension M © No overlap Maximum tension Point B & C Optimal (Tmax) Optimal overlap Present, but not Point A Less tension optimal Not optimal overlap B C A Tension D Length Length tension graph Physiology Revision v4.0 Marrow 8.0 2024  Nerve Muscle Physiology 17 Skeletal muscle fibre types : ----- Active space ----- Type II fibres Characteristics Type I fibres Type II a Type II b Color Red Red White Myoglobin content + High + High - Absent Diameter Small Large Large Myosin ATPase (Contraction) Slow Fast Fast O2 storage + + - Aerobic pathway Pathway to generate ATP Aerobic or anaerobic pathway Anaerobic pathway (Glycolysis) (Oxidation) Recruitment order First Second Last Activities best suited Sitting Standing Running Stimulation of muscle : om Continuous Stimulation of muscle l.c ai State of sustained contraction gm Sustained contraction 3@ (No relaxation) 12 Complete tetanus ir0 Tetanic contraction. av 1 ag Tetanising Frequency (Tf) : Contraction period m | w Cardiac & Smooth Muscle  ro 00:53:28 ar M Cardiac Muscle : © Features : Striated, involuntary. Functional syncytium : Synchronized contraction. - D/t Intercalated disk containing cardiac gap junctions & C onnexins (Protein). Calcium-induced calcium release (CICR) : Induces Calcium from intracellular source. Calcium from extracellular source release Phospholamban : Inhibits SERCA Inhibits Ca2+ Storage Affects relaxation. Absence of tetanisation : ARP RRP Major part of contraction in ARP No summation possible AP No tetany (Evolutionary adaptation). Contraction Action potential Physiology Revision v4.0 Marrow 8.0 2024  18 Physiology ----- Active space ----- Smooth Muscle : Features : Involuntary. Types : - Single unit (Well developed gap junction). - Multi unit. Dense bodies + (Z lines - ). Calcium binding proteins : Calmodulin (Troponin - ). Exclusive properties : - Plasticity. - Latch bridge mechanisms : Sustained contraction using ↓ATP in GIT. Locations : Single unit smooth muscle : GIT, uterus, urinary bladder, ureter. om Multi unit smooth muscle : Iris, ciliary body, piloerector muscle. l.c ai Control of smooth muscles : gm No well defined neuromuscular junction regulated by ANS. 3@ 12 Varicosities : Contain neurotransmitters Ach & norepinephrine ir0 (High activity of smooth muscles). av ag Synapse en passant : One neuron innervates multiple smooth muscle cells. m | Synaptic Transmission  w 01:00:53 ro ar Types : M © Electrical : Chemical : Mediated by chemical/NT Mediated by gap junctions (Connexin protein) Fast mode Slow mode Post Synaptic potentials (PSP) : Excitatory PSP Inhibitory PSP Post-synaptic neruron More positive More negative membrane potential Fast Na+/Ca2+ influx Cl- influx, K+ efflux Slow ↓K+ efflux ↑K+ efflux Physiology Revision v4.0 Marrow 8.0 2024  Nerve Muscle Physiology 19 Regulation : Feedback inhbition. α motor neuron ----- Active space ----- Function : Controls a motor neuron firing. - Glycine + Renshaw cell neuron Skeletal muscle Feedback inhibition Neurotransmitters 01:08:03 NT Location Function Other points Botulinium toxin : Inhibits release Neuromuscular junction, nucleus Muscle contraction, of ACh Acetylcholine basalis of Meynert REM sleep. Receptors : Nicotinic (NMJ) & muscarinic (GIT) om Activates reticular l.c Norepinephrine Locus coeruleus activating system - ai gm State of arousal 3@ 1. Nigrostriatal pathway : Motor control 12 Basal ganglia. ir0 av 2. Mesolimbic : ag Dopamine a. Ventral a. Reward centre - m tegmental area b. Addiction | w b. Nucleus accumbens ro ar 3. Tuberoinfundibular Inhibits prolactin M Raphe nucleus Maintains wakeful state © Serotonin - Platelets Platelet aggregation Histamine Hypothalamus Arousal - Glutamate Hippocampus, sub thalamic nucleus. Learning & memory Major excitatory NT in brain Major inhibitory NT Tetanospasmin (Bacterial toxin) GABA - Hyperpolarisation Inhibits GABA Spastic paralysis Both inhibitory and excitatory NT Glycine Renshaw cells in spinal cord Inhibit a motor neuron Antagonist : Strychnine Nitric oxide Hippocampus Learning & memory Gaseous NT Produced by enzymatic Carbon Pain processing & - degradation of heme monoxide olfaction. Gaseous NT Physiology Revision v4.0 Marrow 8.0 2024  20 ----- Active space ----- NEUROPHYSIOLOGY : PART 1 Sensory physiology General senses : Special senses : Touch, pain etc. Vision, hearing, olfaction, taste etc. General Senses 00:00:33 Receptors : Touch receptors : Meissner corpuscle Merkel cells Pacinian corpuscle Ruffini endings om Level Superficial Deep l.c ai Sensation Discriminatory touch, stroking Texture, edges (Braille) Pressure, vibration Skin stretch gm Adaptation Rapid Slow Rapid Slow 3@ 12 ir0 av Appearance ag m | w ro Pain receptors : Free nerve endings of A delta & C fibers. ar M A Delta fibers C fibers © Type of pain First pain (Fast) Second pain (Slow) Myelination Present Absent Tract Neospinothalamic tract (Newer) Paleospinothalamic tract (Very old) Neurotransmitter Glutamate Substance P Gate control theory of pain (Melzack & Wall) : “Non-painful sensations can override & ↓painful sensations.” Mechanism : + Pain + Aδ/C fibers + Projection neuron in spinal cord via thalamus Sensory cortex. (SUbstantia gelatinosa) - Massage/Transcutaneous + Aβ fibers + Inhibitory neuron in electrical nerve stimulation spinal cord (TENS) Physiology Revision v4.0 Marrow 8.0 2024  Neurophysiology : Part 1 21 Note : ----- Active space ----- 1. Pain relief in acupuncture : Activation of endogenous Releases opioid analgesic system in Endogenous morphine Pain relief. periaqueductal gray matter (Endorphins) 2. Allodynia : Non-painful stimulus causing painful sensation. Somatosensory Pathways : Dorsal column pathway Anterolateral pathway Sensation Proprioception, touch, vibration Pain, temperature Distribution in spinal cord Ipsilateral (I/L) Contralateral (C/L) Level of crossing over At medulla At spinal cord Brown-Séquard syndrome : Hemisection of spinal cord. I/L loss of proprioception, touch, vibration (Dorsal column senses). om C/L loss of pain & temperature (Anterolateral column senses). l.c ai Sensory Homunculus : gm 3@ Ventral posterolateral (VPL) nucleus Projected to S ensory cortex (Represented 12 (Thalamic nucleus for touch & pain) by sensory homunculus) ir0 av ag m Cortical plasticity : | Encroachment of a cortical area by a neighboring cortical area Basis for w ro phantom limb. ar M © Weber-Fechner law : Magnitude of sensation felt ∝ Log intensity of initial stimulus. Minimum Maximum Size of area ∝ Degree of usage Physiology Revision v4.0 Marrow 8.0 2024  22 Physiology ----- Active space ----- Vision 00:17:01 Retina : Cell Type Characteristics Receptors of night vision. Rods More sensitive to light. Receptors of day vision/colour vision. Cones ↑in foveal region. Receives signals from rods and cones and makes Bipolar cells connection with ganglion cells. Only output cell of retina (Their axons are the optic nerve) Ganglion cells Only retinal cell capable of producing action potential. Connects rods and cones. Horizontal cells Sharpens the signal by lateral inhibition. om Purely depolarising cells of retina. l.c Amacrine cells Connects ganglion cells. ai gm Sharpens the signal by lateral inhibition. 3@ Supporting glial cells. Muller's cells/Retinal glial cells 12 No role in vision. ir0 av ag m Rods | w ro ar Cones M © Bipolar cell Muller's cell Horizontal cell Amacrine cell Ganglion cells DIrection of light Physiology Revision v4.0 Marrow 8.0 2024  Neurophysiology : Part 1 23 Physiology of Vision : ----- Active space ----- a) Dark state : b) Light reflex : II cis retinal light + Light cGMP dependent cGMP dependent Na+ channel open All trans retinal + Na+ channel closes (Funny current channel) Na+ Transducin No influx of Na+ + Phosphodiesterase Degrades cGMP K+ K+ om Rod in dark state : Depolarisation Rod in light state : Hyperpolarisation l.c Lateral Geniculate Body : ai Retina Lateral geniculate body (LGB) in thalamus gm 3@ 12 Contains 6 layers. ir0 av Magnocellular layer (Contains large cells) ag Parvocellular layer (Contains small cells) m | w Magnocellular pathway Parvocellular pathway Koniocellular pathway (Minor) : ro ar Origin Layers 1 and 2 of LGB Layers 3, 4, 5, 6 of LGB Originates from K cells. M Termination Layer 4 of visual cortex Layer 4 of visual cortex Detection of blue colour. © Color vision Function Eye movements Finer details Both LGBs receive stimuli from both eyes : I/L eye : Layers 2, 3, 5. C/L eye : Layers 1, 4, 6. Visual Cortex : Thalamus Visual cortex/Striate cortex/Striae of Gennari. Area 17, 18, 19. In calcarine sulcus of occipital lobe. Colour vision : Pathway : Retina (Cones) Thalamus (Parvocellular pathway) Visual cortex. Retinal cones : L cone M cone S cone Wavelength Long Medium Short Detects Red Green Blue Defect causes Protanopia Deuteranopia Tritanopia Physiology Revision v4.0 Marrow 8.0 2024  24 Physiology ----- Active space ----- Hearing 00:31:37 Cochlea : Bony cochlear wall Scala Media (IHC) Organ of corti Scala vestibuli Cochlear duct (OHC) Tectorial membrane Reissner’s Basilar membrane membrane Scala tympani Spiral ganglion CN VIII Cochlear (Cochlear division) Organ of corti Hair cells : Receptors for hearing. Smallest hair cell : Stereocilium. Covered by tectorial membrane. Tallest hair cell : kinocilium. All hair cells bend Depolarisation Measured as om towards kinocilium (D/t influx of K+) otoacoustic emissions. l.c ai gm 3@ Basilar membrane : 12 ir0 Base Apex av Size Broad Narrow ag m Close to Oval window Helicotrema | w Sensitive to ↑Frequency sound waves ↓Frequency sound waves ro ar Auditory Pathway : M © Mnemonic : ECOLI MA. CN Eight Cochlea Superior Olivary nucleus Lateral lemniscus Inferior colliculus (Sound direction process) (Sound direction process) Auditory cortex (In superior temporal/Heschl gyrus of temporal lobe) Medial geniculate body (Thalamus) Olfaction 00:39:35 Receptors : Bipolar neurons (Combine to form CN 1). Location : Olfactory epithelium in upper part of nose. Olfactory epithelium : Contains bipolar neurons, sustentacular cells (Supporting cells), basal stem cells (↑Regenerative capacity). Physiology Revision v4.0 Marrow 8.0 2024  Neurophysiology : Part 1 25 Olfactory bulb : ----- Active space ----- Receives information from olfactory epithelium. Contains : Excitatory cells Inhibitory cells Types Mitral cells, tufted cells Periglomerular cells, granule cells Neurotransmitter Glutamate GABA Higher centres : Function Olfactory cortex Conscious discrimination of odor. Orbitofrontal cortex Amygdala Processing of emotions evoked by smells. Entorhinal cortex Processing of memories evoked by smells. Taste om 00:42:40 l.c Basic taste sensations in humans ai gm 3@ Sweet Sour Bitter Salty Umami (Recent addition) : 12 ir0 Produced by MSG. av Receptor for taste : ag m Receptor type Receptors | w ro Salty Epithelial sodium channel (ENaC) ar Ionotropic Sour ENaC, HCN channels, TRP channels M © Sweet T1R2, T1R3 Bitter Metabotropic (G Protein coupled) T2R Umami mGluR4, T1R1, T1R3 Pathway : Anterior 2/3rd of tongue Posterior 1/3rd of tongue Palate, pharynx Chorda tympani branch Glossopharyngeal Vagus of facial nerve nerve nerve Medulla : Nucleus Tractus Solitarius (Taste integrating centre) Ventral posteromedial nucleus of thalamus (VPM) Taste cortex : Anterior insula, frontal operculum. Physiology Revision v4.0 Marrow 8.0 2024  26 Physiology ----- Active space ----- Motor Physiology  00:45:55 Motor pathway (Descending) : Motor cortex Spinal cord (Alpha & gamma motor neurons) Skeletal muscle. Motor Cortex : Primary motor cortex Premotor cortex Supplementary motor cortex Location Precentral gyrus : Frontal lobe Anterior to precentral gyrus - Brodmann area 4 6 6 Bimanual coordination for Function Execution of motor movements Orient the body for movement complex tasks Motor Tracts : om l.c ai gm 3@ 12 ir0 av ag m | w Pyramidal tracts Motor cortex ro ar Lateral M corticospinal © tract Lateral motor pathway