Physiology Revision 1 PDF

Physiology Revision 1 01 1 PHYSIOLOGY REVISION 1 ----- Active space ----- Homeostasis...

Physiology Revision 1 01 1 PHYSIOLOGY REVISION 1 ----- Active space ----- Homeostasis 00:01:55 Maintenance of homeostasis : Control Systems Negative feedback Positive feedback Feed-forward Increase followed by Increase followed Anticipatory changes decrease by increase Example : Thinking Example : Examples: (CLAPS) about food increases Baroreceptor reflex. Clotting. salivary secretions. Ca entry into sarcoplasmic reticulum. LH surge. Action potential. Parturition. Shock. Assessment of effectiveness of negative feedback : Gain = Correction/Error left : Correction : The reduction offered by the feedback mechanism. Error : The difference of the corrected value from the normal value. a. If error left : Not a good control system. b. Zero error : Gain is infinity (Role of kidneys in regulating BP : Baroreceptors act first → kidney excretes large volumes of urine). Very high gain : -33 → Regulation of body temperature. Cellular Physiology 00:13:10 Cell membrane : Three components : Proteins (55%), lipids (45%) and carbohydrates (5%). Based on functional importance : Fluid mosaic model. Fluid : lipid ; Mosaic : protein. Physiology Revision 1.0 Marrow 6.5 2023  2 01 Physiology ----- Active space ----- 1. Lipid bilayer : The “Fluid” part of the model. Three types : Phospholipids, glycolipids, and sterols. a. Phospholipids : Phosphatidylcholine (Lecithin : Major component of surfactant). Sphingomyelin (Minor component of surfactant). Phosphatidylserine : Usually intracellular (Acts as a signal for apoptosis when presented externally). Phosphatidylinositol (IP3) : Acts as a second messenger. Cardiolipin : Exclusive to human heart in mitochondria. Anticardiolipin Ab seen in Syphilis. b. Glycolipids : Cerebrosides : Abundant in CNS. Gangliosides : Abundant in GIT. Fragment B of GM1 Ganglioside : Receptor for cholera toxin in GIT. c. Sterols : Cholesterol : Maintenance of membrane fluidity (Fluidity buffer). Increase in fluidity Decrease in fluidity (unsaturated FAs) (saturated FAs) Linoleic acid Stearic acid Linolenic acid Palmitic acid Arachidonic acid Omega 3 FAs (Fish) 2. Membrane proteins : a. Transmembrane proteins (integral membrane proteins) : Present across the cell membrane. Can be of multiple types : Receptors : G-protein coupled receptor. Pumps : Na+ K+ ATPase. Channel : Cystic fibrosis transmembrane regulator (CFTR) → Codes for Cl- channel. Physiology Revision 1.0 Marrow 6.5 2023  Physiology Revision 1 01 3 b. Peripheral proteins : Present peripherally on the cell membrane. ----- Active space ----- Exclusively abundant in RBCs and skeletal muscle : RBCs : Spectrin and Ankyrin. Skeletal muscle : Dystrophin. c. Lipid anchored proteins : Require lipids for their attachment. Exclusively abundant in RBCs. Prevent RBCs from hemolysis : CD 55, CD 59. b a c Cell organelles 00:27:44 1. Endoplasmic reticulum (ER) They are of two types : a. Rough ER : Granulated d/t presence of ribosomes on surface. Function : Aid in the biosynthesis of proteins. Along with chaperones (Aid in protein folding) : Heat shock proteins ER-associated degradation : Destruction of misfolded proteins (Eg., prion proteins). b. Smooth ER : No granulations. Functions : Drug detoxification in the liver. Calcium Storage in muscle : Sarcoplasmic reticulum. Steroid biosynthesis in adrenal gland, liver, testis, ovary. Physiology Revision 1.0 Marrow 6.5 2023  4 01 Physiology ----- Active space ----- 2. Golgi apparatus: Has 2 ends : Cis end receives protein Trans end releases vesicles Function : Post translational modification : Glycosylation (Addition of carbohydrate side chain). Sorting of proteins : Adding mannose-6-phosphate (By enzyme phosph transferase) Deficiency of phosphotransferase : Inclusion cell disease (I cell disease). 3. Lysosomes: Responsible for destruction of bacteria by phagolysosome formation. Acid mediated destruction (Acid lipase, acid hydrolase). During starvation, can destroy mitochondria to release energy : Autophagy. 4. Peroxisomes : Function : Generation and degradation of hydrogen peroxide (H2O2) by catalase. Oxidation of fatty acids : Long chain (16–22 carbons), very long chain (24–26 carbons), and branched chain fatty acids. Peroxisomal disorders : Zellweger syndrome, Refsum disease. 5. Mitochondria: Derived from the ovum (i.e., maternal inheritance). Human mitochondrial DNA : Circular dsDNA (16,500 base pairs). Mutations in mitochondrial DNA : > 10 times the rate for nuclear DNA. Affects organs with high metabolic requirements (Skeletal muscle, brain liver, heart). 6. Nucleus : The blue prints for DNA : Chromosomes. DNA + Histones = Chromatin : Has repeating structural unit called nucleosomes Substances can move to and from the nucleus through nuclear pore complex (NPC). Proteins of NPC : Exportins : Move substances out of the nucleus. Importins : Move substances into the nucleus. Physiology Revision 1.0 Marrow 6.5 2023  Physiology Revision 1 01 5 7. Cytoskeleton : ----- Active space ----- Maintains structural integrity of the cell. Types : Intermediate Microfilaments Microtubules filaments a. Microtubules : Kinesin : Forward axonal transport (cell body → synapse). Dynein : Reverse axonal transport (synapse → cell body), used by Rabies, Polio, C.tetani. Motility of Cilia (Lung), sperm, fallopian tubes (Absence : Kartagener’s/ immotile cilia syndrome). Tubulin : Helps in movement of chromosomes during division. Microtubule inhibitor drugs : Vincristine, vinblastine, colchicine. b. Microfilaments : Exclusive to skeletal muscle. Actin and myosin. Function : Muscle contraction : Sliding filament theory. Cell motility : By actin polymerisation (Eg., L. monocytogens → Tumbling motility). C. Intermediate filaments → Act as tumor markers : Filaments Tissue Marker for Epithelial tissue Epithelial carcinomas Keratin Liver (Mallory-Denk Alcoholic Liver Disease Bodies) Desmin Muscle Sarcomas Connective tissue Vimentin Mesenchymal tumors (fibroblasts) Glial fibrillary acidic Astrocytes Astrocytomas protein (GFAP) Lamin Nucleus Progeria (premature aging) Physiology Revision 1.0 Marrow 6.5 2023  6 01 Physiology ----- Active space ----- 8. Cell junctions : They allow for communication between cells. They can be classified as : a. Cell-cell junctions : Tight junctions Zona adherens Desmosomes Gap junctions b. Cell-basement membrane junctions : Hemidesmosomes Focal adhesions Cell - cell junction Protein Related disorder Occludin Zona occludens Familial hypomagnesemic hyper- (Tight junctions) Claudin calciuria. Zona adherens Cadherin Desmosomes Desmoglein Pemphigus Gap junctions (abundant in Connexin heart) 9.Hormone receptors : Types Extracellular Intracellular Cell membrane recep- Cytoplasmic receptors : Nuclear receptors : tors : Glucocorticoid receptor. Estrogen Receptor G- Protein coupled Mineralocorticoid Vitamin A : Retinoic receptors receptor. acid receptor (RAR) Receptor tyrosine Androgen receptor. Progesterone kinase (Insulin) Vitamin D receptor. receptor Cytokine receptor Thyroid hormones. family (GH, Prolactin, Leptin, Erythropoietin) Physiology Revision 1.0 Marrow 6.5 2023  Physiology Revision 1 01 7 G-Protein coupled receptors : ----- Active space ----- 7 trans-membrane domains. 3 subunits (Alpha, beta, gamma). The second messenger systems activated through coupling of hormone receptor complexes : 2nd messenger Hormone Function Vasopressin (V2) Water reabsorption cAMP Epinephrine (beta) Metabolism Secretin Electrolyte secretion Vasopressin (V1) vasoconstriction Calcium Oxytocin Uterine contraction TRH Exocytosis Of TSH Nitric oxide Dilatation cGMP Natriuretic peptides Relaxation Membrane Transport Processes 01:04:54 1. Simple Diffusion → Fick’s law : Directly proportional to concentration, area of membrane, lipid solubility. Inversely proportional to membrane thickness, size of particle. 2. Facilitated diffusion : Carrier or channel proteins (GLUT, Aquaporins). 3. Primary active transport : Pumps (ATPases). 4. Secondary active transport : Co-transporter : SGLT , Na+ I-- symporter, Na+ K+ 2Cl- Co-transporter. Exchanger : Cl- HCO3- exchanger. Vesicular transport : a. Exocytosis (SNARE) , endocytosis (Clathrin) b. Both require Ca2+. Passive (no ATP) Active (ATP) Simple diffusion Facilitated diffusion Physiology Revision 1.0 Marrow 6.5 2023  8 01 Physiology ----- Active space ----- Saturation kinetics : Membrane Potentials 01:14:56 1. Resting Membrane potential (RMP) The inside of a cell is always negative. Cause : Passive diffusion of K+ ions out of a cell. Cell RMP Neuron -70mV Skeletal muscle -90mV Cardiac ventricle Sinoatrial node -60 to -40mV Cajal cell (GIT) (Restless MP : Oscillatory RMP as they are Pre- Botzinger complex pacemakers). 2. Equilibrium potential : Potential at which there is no ion movement. Nernst equation : Equilibrium potential of an ion = ± 61 log Outsise concentration Inside concentration Important ions and their equilibrium potentials : Ion Equilibrium potential Na+ +60mV K+ -90mV Cl- -70mV ( RMP of neuron) Ca2+ +130mV Physiology Revision 1.0 Marrow 6.5 2023  Physiology Revision 1 01 9 Gibbs-Donnan Effect : ----- Active space ----- The presence of non-diffusible ions affects the distribution of diffusible ions : Na+, K+, Cl-. The GD effect is always d/t proteins (Non-diffusible). Cellular Fluids 01:20:50 1. Classification: Total Body weight (60kg) Total body water (60%) Solid Mass (40%) 42 Lts 1/3rd ECF 2/3rd ICF 14 Lts 28 Lts Interstitial Plasma fluid 3.5 Lts 10.5 Lts 2. Fluid indicators : Indicators (Indicator dilution Volume principle) Total Body Water Deuterium, Tritium Extracellular fluid (ECF) Inulin, Sucrose Radiolabelled Albumin Plasma Volume (PV) Evan’s Blue dye Blood volume (BV) Chromium tagged RBCs = PV/(1 - Hematocrit) Interstitial fluid Nil = ECF - PV Intracellular fluid Nil = TBW - ECF Physiology Revision 1.0 Marrow 6.5 2023  10 01 Physiology ----- Active space ----- 3. Darrow - Yannet diagrams : Normal osmolarity = 300mOsm/L. Volume → X - axis. Osmolarity → Y- axis. Example 1 : SIADH → gain of water. Example 2 : Excessive NaCL intake → Hypertension. Physiology Revision 1.0 Marrow 6.5 2023  Physiology Revision 2 02 11 PHYSIOLOGY REVISION 2 ----- Active space ----- Nerve muscle physiology 00:00:15 Nerve physiology : Two types of cells in central nervous system : 1. Nerve cells or neurons. 1 neuron : 10 glial cells 2. Glial cells or glia. Types of neuroglia : 1. Central Nervous System : i. Ependymal cells : Secrete CSF. ii. Oligodendrocytes : Myelination in CNS (multiple neurons - 1 : 30). iii. Astrocytes : Blood Brain barrier. iv. Microglia : Phagocytosis. 2. Peripheral Nervous System : i. Satellite cells : Cushioning effect to neurons. ii. Schwann cells : Myelination in PNS (multiple neurons - 1 : 1). Structure of neuron : Myelin : Lipid : Sphingomyelin. Protein : Myelin basic protein (autoantibody target in multiple sclerosis → demyelination). Use : Fastens conduction velocity, insulation. Physiology Revision 1.0 Marrow 6.5 2023  12 02 Physiology ----- Active space ----- Nerve action potential : 00:09:18 Phase 1 : Local potential (slow Na influx) (-70 → -55 mV). Phase II : Depolarisation (opening of volt age gated Na channel, fast Na influx). Phase III : Repolarisation (K+ efflux). Phase IV : Hyperpolarisation (Cl- influx). ARP : Depolarization & 2/3rd repolarization RRP : 1/3rd of repolarization to end of action potential. Erlanger & Gasser classification Loyd Hunt classification Fiber Myelin Diame- Conduction Functions type ter (um) velocity (m/s) Aα Maximum Muscle spindle (Proprioception) 1a Golgi tendon organ 1b α motor neurons - Aβ + Touch, pressure II Aγ Motor to muscle spindles (γ - motor neuron) Aδ Fast pain III B Pre-ganglionic autonomic - C - Mini- Slowest Slow pain, Postganglionic 1V mum sympathetic Nerve Injury : Axon : M/C site of nerve injuries. Wallerian/distal degeneration Retrograde/proximal degeneration Usually begins within 24-36 hrs after within 48 hours of injury injury Axon degeneration → Myelin sheath Nucleus pushed to periphery. degeneration → Debris cleared by Destruction of Nissl bodies → Chromatolysis. macrophages & Schwann cells Physiology Revision 1.0 Marrow 6.5 2023  Physiology Revision 2 02 13 Nerve regeneration : ----- Active space ----- Starts within 96 hours of the injury (slow process). Tinel sign : Tingling sensation on tapping injuried nerve (positive in regener- ating nerve). Skeletal muscle 00:27:58 Sarcomere : Functional unit of muscle. Area between two Z lines. Skeletal muscle proteins : Contractile Supportive proteins Regulatory Relaxation proteins proteins protein Actin. Titin (elastic like Tropomyosin. Calcium channel Myosin. spring). Troponins. protein (SERCA pump Calcium channels Desmin (Intermediate activation → (Dihydropyridine, filament) : Structural relaxation). ryanodine support. receptors). Dystrophin. Alpha actin (attaches actin to Z line). Myomesin (attaches myosin to M line). Nebulin (molecular ruler). Physiology Revision 1.0 Marrow 6.5 2023  14 02 Physiology ----- Active space ----- Neuromuscular junction (NMJ) 00:35:21 Steps of neuromuscular transmission : Step Disorder 1. Opening of voltage gated Na+ channels → Blocked by tetradotoxin (Puffer fish) → Na+ influx (Voltage : -70 → -40 mV) Muscle paralysis 2. Opening of voltage gated Ca2+ channels Lambert Eaton syndrome : Antibodies to Ca2+ → Ca2+ influx channels → Muscle weakness 3. Exocytosis of neurotransmitters (acetyl- Blocked by Botulinium toxin choline) 4. Attach to nicotinic-ACh receptor Myasthenia gravis : Antibodies to nicotinic-Ach receptors → Muscle weakness 5. Na+ influx into motor end plate → Depolarization → DHPR receptor activation → Acti- vates Ryr receptors (mechanical interaction) → Release of Ca2+ → Muscle contraction. Molecular mechanism of muscle contraction : 00:39:50 Sliding filament theory : Applied aspect : After death d/t No ATP → Myosin head remains attached → Rigor mortis. Physiology Revision 1.0 Marrow 6.5 2023  Physiology Revision 2 02 15 During this processs, muscle length + tension changes. ----- Active space ----- Between point B & C, actin & myosin have optimal magnitude of overlap (sarcomere length : 2.0-2.2 microns) allowing maximum tension to be generated. Fibers of skeletal muscle : Characteristics Type I fibers Type II fibers Type II a Type II b Features Slow, oxidative Fast, oxidative, glycolytic Fast, glycolytic Myoglobin content Present Present Absent Color Red Red White Myosin ATPase activity Slow Fast Fast Diameter Small Large Large Glycolytic capacity Moderate High Highest Oxidative capacity High Moderate Low (glycolysis) Recruitment order Function/activities Posture Walking Sprinting/running Cardiac & smooth muscle 00:52:30 Cardiac muscle : Striated, involuntary. Intercalated disc with cardiac gap junctions (functional syncytium). Proteins : Connexins. Calcium Induced calcium release (CICR) : Calcium from extracellular source → Induces calcium from intracellular source (sarcoplasmic reticulum). Smooth muscle : Involuntary. Single unit (gap junctions present, found in GI tract) & multi-unit (gap junctions negative, found in blood vessels). Dense bodies present, Z lines absent. Calmodulin : Calcium binding protein. Physiology Revision 1.0 Marrow 6.5 2023  16 02 Physiology ----- Active space ----- Plasticity : No titin, no elasticity. Latch bridge mechanism : Can be maintained in a state of sustained contraction with a little use of ATP (energy efficient). Synaptic graded potentials 00:56:30 Excitatory post-synaptic Inhibitory post-synaptic potential (EPSP) potential (IPSP) Post- More positive More negative synaptic neuron membrane potential Fast Na+ or Ca2+ influx Cl- influx Slow K+ efflux reduced K+ efflux increased Neuronal networks : Physiology Revision 1.0 Marrow 6.5 2023  Physiology Revision 2 02 17 Neurotransmitters (NT) 01:04:28 ----- Active space ----- NT Location Function Other points Acetylcholine Neuromuscular Muscle contraction, Botulinium toxin : junction, nucleus REM sleep. Inhibits release of basalis of Meynert ACh. Receptors : Nicotinic (NMJ) & muscarinic (GIT). Norepinephrine Locus coeruleus Activates reticular activating system → awake state Dopamine 1. Basal ganglia 1. Motor nuclear control. (Nigrostriatal pathway). 2. Mesocortical : 2a. Reward centre. a. Ventral tegmental area. b. Nucleus 2b. Addiction. accumbens. 3. Tuberoinfundib- 3. Inhibits prolactin ular Serotonin Raphe nucleus, GI Arousal, peristalsis, tract, platelets. platelet aggregation. Histamine Hypothalamus Arousal Glutamate Hippocampus, sub Learning & memory Major excitatory NT in thalamic nucleus. brain GABA Hyperpolarisation (Cl- Major inhibitory NT Influx) Glycine Renshaw cells in Inhibit α motor neuron Both inhibitory and spinal cord excitatory NT. Antagonist : Strychnine Nitric oxide Hippocampus Learning & memory Gaseous NT Carbon Learning, memory, Produced by monoxide pain processing & enzymatic olfaction. degradation of heme by Heme oxygenase. Gaseous NT. Physiology Revision 1.0 Marrow 6.5 2023  18 03 Physiology ----- Active space ----- PHYSIOLOGY REVISION 3 General senses 00:00:30 Touch receptors : Meissner’s Pacinian corpuscle Merkle’s cell Ruffini corpuscle endings Gentle tapping. Pressure. Sustained Joint capsule Low frequency High frequency pressure. receptor. vibration. vibration. Braille reading Skin stretch. Rapidly Largest by blind people. Slow adapting. adapting. receptor. Slow adapting. Rapidly adapting. Pain receptors : Location : Free nerve endings of A-δ & C fibers. Slowly adapting. A-δ fibres C fibers Responsible for 1st pain (Fast) Responsible for 2nd pain (Slow) Neospinothalamic tract Paleospinothalamic tract Release glutamate Release substance P Gate control theory of pain :. Normally : A-δ & C fibers → Projection neurons → Thalamus → Sensory cortex. During massage → A-β fibers activated → Inhibit projection neurons (substantia gelatinosa) → Inhibit pain. Somatosensory pathways : Dorsal column pathway Anterolateral pathway Myelinated (fast) Unmyelinated (slow) Carries : Carries : Proprioception (A-α fibers). Pain. Touch & Vibration. Temperature. Ascends on the same side. Ascends on opposite side. Crossing over at medulla Crossing over at spinal cord. Thalamus (Ventroposterolateral nucleus) → Sensory cortex (Post central pari- etal cortex → Brodmann area 3, 1 & 2). Physiology Revision 1.0 Marrow 6.5 2023  Physiology Revision 3 03 19 Brown Sequard syndrome : ----- Active space ----- Hemisection of spinal cord. Ipsilateral (I/L) loss of dorsal column senses. Contralateral (C/L) loss of anterolateral pathway senses. Sensory homunculus : Body parts represented on sensory cortex based on extent of usage : a. Max : Lips, thumb. b. Min : Hip, trunk, back. Special senses 00:15:48 Vision : Retina → Thalamus (lateral geniculate body) → Visual cortex. Retinal cells Characteristics Rods Max number (120 million) Receptors for dim vision (night vision). Cones Around 6 million. Colour & day light vision. Bipolar cells Relay b/w rods, cones to ganglion cells. Ganglion cells Continues as optic nerve (Only output cell). Horizontal cells Connects rods & cones. Amacrine cells Connects bipolar & ganglion cells. Muller cells Retinal glial cells (No role in vision). Rods : Dark state Rods : Light state Funny current channels (cGMP 11-cis retinal Light All trans retinal→ dependent Na+ channels) Activates transducin (G protein receptor) → Activates phosphodiasterase→ Degrades cGMP → Close Na+ channels. Depolarisation. Hyperpolarization. More neurotransmitter release. Decreased neurotranmitter release Physiology Revision 1.0 Marrow 6.5 2023  20 03 Physiology Lateral geniculate body : ----- Active space ----- Magnocellular pathway Parvocellular pathway Origin Layers 1 & 2 Layers 3, 4, 5, 6 Termination Layer 4 of visual cortex Layer 4 of visual cortex Movement of eyes, detect Function Detects colour vision, finer details depth & flickers 2, 3 & 5 : Recieves from I/L eye. 1, 4 & 6 : Recieves from C/L eye. Visual cortex : Brodmann area 17, 18 & 19 of calcrine cortex of occipital lobe. Striations due to myelinated fibers (striate cortex or stria of gennari). Colour vision : Red : L cone. Green : M cone. Blue : S cone. Cones → LGB (parvocellular pathway)→ Visual cortex (blobs) → Perception. Hearing : Cochlea : Endolymph Surrounds scala media. K+ rich Perilymph Surrounds scala vestibuli & tympani. Na+ rich Organ of corti : Outer hair cells are numerous, easily prone to damage & ototoxic drugs. Tallest hair cell : Kinocilia. Progressive small hairs : Stereocilia. Hair cells bending to kinocilia : Depolarisation (K+ influx). Measured as otoacoustic emissions (kemp waves). Auditory pathway : (Mnemonic : ECOLIMA) Eighth nerve → Cochlear nuclei → Olivary nucleus (superior)→ Laternal lemniscus → Inferior colliculus→ Medial geniculate body → Auditory cortex (Area 41/Heschl’s gyrus). Physiology Revision 1.0 Marrow 6.5 2023  Physiology Revision 3 03 21 Olfaction : ----- Active space ----- Olfactory receptors : Location : Roof of nasal cavity. Bipolar neuron. Olfactory bulb has 4 cells : Mitral Excitatory (releases glutamate) Tufted Periglomerular Inhibitory (releases GABA) Granule Olfactory nerve piercing Cribriform plate Olfactory receptors → Olfactory bulb→ Thalamus (dorsomedial nucleus) → Olfactory cortex. Central area Function Olfactory cortex (orbitofrontal cortex) Smell perception Amygdala Interrelation b/w smell & emotion Entorhinal cortex Interrelation b/w smell & memory Taste : 5 basic states : Sweet. Sour. Bitter : Alkaloids & poisons. Salt. Umami : Produced by MSG (Mono Sodium Glutamate). Pathway : Anterior 2/3 rd tongue Posterior 1/3 rd tongue Palate, pharynx Chorda tympani branch of Glossopharyngeal nerve Vagus nerve facial nerve Medulla (nucleus tractus solitarius) Ventral posteromedial nucleus of thalamus Taste cortex : Anterior insula, frontal operculum Physiology Revision 1.0 Marrow 6.5 2023  22 03 Physiology ----- Active space ----- Laws & senses in sensory physiology 00:46:48 1. Doctrine of specific nerve energies (muller’s doctrine ) : Receptors are specific for a specific sensation. Ex : Pacinian → Touch, Free nerve endings → Pain. 2. Bell Magendie law : Dorsal roots : Sensory. Ventral roots : Motor. 3. Law of projection : Cortex projects sensations to receptor location. Ex : Phantom pain. 4. Weber-Fechner law : Magnitude felt ∝ Log of intensity of stimulus. Motor physiology 00:50:35 Neurons & tracts Location Upper motor neurons Brain : Cortex, brain stem Lower motor neurons Spinal cord : A-α, A-γ neurons Pyramidal tract Lateral & anterior component of corticospinal tract Extrapyramidal tract Originates from brainstem Vestibulospinal, tectospinal, rubrospinal, reticulospinal tract Decerebrate rigidity Decorticate rigidity Fingers flexed, forearms pronated & Upper extremities flexed against upper extremity extended chest Extensor rigidity Lesion of CST CST & rubrospinal tract lesion Intact rubrospinal tract Overactivity of reticulospinal tract Physiology Revision 1.0 Marrow 6.5 2023  Physiology Revision 3 03 23 Muscle spindles : ----- Active space ----- 1. Nuclear bag fibers : Dynamic component. Static component. 2. Nuclear chain fibers : Static component. Sensory supply : Primary (group Ia) endings Secondary (group II) endings Annulospiral endings Flower spray endings Innervates all fibers of bag & chain Innervates only static component Motor supply : γ- motor neuron. Stretch & Inverse stretch reflex : Characteristics Stretch reflex Inverse stretch reflex Receptor Muscle spindle Golgi tendon organ Detects muscle length Muscle tension Afferant Group IA & II endings Group Ib Center Spinal cord Spinal cord Efferent α-motor neuron α-motor neuron Effect Contraction Relaxation Reason for the effect α-motor neuron activated α-motor neuron inhibited No. of synapses Single : Monosynaptic Two : Disynaptic involved Other name Myotatic reflex Lengthening reaction Regulation of stretch reflex : γ- motor neurons stretches periphery of spindle → Activates afferant central portion of spindle. Sensitivity of stretch reflex ↑. Withdrawal reflex : Polysynaptic reflex. Flexion of I/L limb away from stressor. Extension of C/L limb. I/L activation of flexors & inhibition of extensors. C/L activation of extensors & inhibition of flexors. Reason : Reciprocal innervation. Physiology Revision 1.0 Marrow 6.5 2023  24 04 Physiology ----- Active space ----- PHYSIOLOGY REVISION 4 Cerebellum 00:00:21 Motor brain part (efferent). Function of cerebellum : Start-stop signaling (co-ordination of motor activity). 3 parts of cerebellum 4 cerebellar deep nuclei 5 cells of cerebellum Spinocerebellum Dentate Purkinje cells (co-ordination) Emboliform Stellate cells Inhibitory Vestibulocerebellum Fastigial Excitatory Golgi cells (balance & equilibrium) Globose Basket cells Neocerebellum Granule cells (excitatory) (planning) Afferents to cerebellum : Climbing fibers Mossy fibers Originate in the inferior olivary nucleus Originate from cell bodies in the spinal cord & (olivocerebellar). brain stem (Spinocerebellar). + + + Granule cells Deep nuclei Purkinje cells (inhibitory) (excitatory) + - + Thalamus & motor cortex Deep nuclei Stellate, basket, + - Golgi cells (inhibitory) Motor movement Motor movement - Purkinje cells NOTE : Granule cells firing can also be + controlled by its inhibition through Golgi cells. Deep nuclei escapes + Features of cerebellar disease : Next motor movement 1. Decomposition of movement 2. Hypotonia 7. Dysdiadochokinesia 3. Pendular knee jerk 8. Rebound phenomenon 4. Ataxia 9. Dysarthria 5. Dysmetria 10. Nystagmus 6. Intention tremor Note : Resting tremor seen with basal ganglia lesions Physiology Revision 1.0 Marrow 6.5 2023  Physiology Revision 4 04 25 Basal ganglia 00:09:11 ----- Active space ----- Always inhibitors (even at rest) Inhibits both voluntary + involuntary movements. Lesions : Predominantly involuntary movements. Nuclei : Input nuclei (use GABA) output nuclei (use GABA). major excitatory nuclei : Use glutamate Use dopamine Lesions in subthalamic nuclei : Sudden violent contractions of one large joint (hemiballismus). Pathways : Direct → Activated → Facilitates movements. Caudate and putamen (striatum) - GABA GPi + Motor nucleus of thalamus (ventral anterior nucleus) + Motor cortex + + Movement Indirect → Activated → Inhibits motors movements Caudate and putamen (striatum) - GPe + Subthalamic nucleus + + GPi Motor nucleus of thalamus (ventral anterior nucleus) - - Motor cortex - Movement Physiology Revision 1.0 Marrow 6.5 2023  26 04 Physiology ----- Active space ----- Thalamus 00:18:39 Olfaction (dorsal median nucleus) Memory (Papez circuit) Motor nucleus General senses (touch, pain, temperature) Hearing Vision Hypothalamus 00:20:42 Nuclei Function Anterior Heat environment Posterior Cold environment Lateral Feeding centre (Orexin) Ventromedial Satiety centre Suprachiasmatic Regulates circadian rhythm Supraoptic ADH (mainly) Paraventricular Oxytocin (mainly) Ventrolateral Sleep centre preoptic nucleus Mamillary bodies Memory Regulation of body temperature : Heat Cold Anterior hypothalamus → Sweating Posterior hypothalamus → Shivering + Thirst sensation (osmoreceptors) + frequency of Micturition + Vasodilation (to dissipate heat). + Vasoconstriction (conserve heat) Feed forward control system : Skin temperature → Anticipated by hypothalamus → Prevents of core temperature Physiology Revision 1.0 Marrow 6.5 2023  Physiology Revision 4 04 27 Learning & Memory : ----- Active space ----- Memory Declarative/ explicit memory Nondeclarative/ implicit memory Semantic memory (for facts) Episodic memory (for events) Skills memory/ procedure Involves anterior temporal Involves Hippocampus, memory. cortex, prefrontal cortex medial temporal lobe, neocortex Ex : Driving Hippocampus : Short term memory to Long term memory. Repetition (revision) → Synaptic strengthening → Long term potentiation (LTP). Lesions : Anterograde amnesia (cannot form long term memories). No role in storage of memories. Their procedural & skill memories are intact. Mammillary bodies : Memory (part of Papez circuit). Lesions : Wernicke Korsakoff psychosis (confabulation - honest lying). Lesion at Anterior nucleus of thalamus → Loss of recent memories. Basal Forebrain (Nucleus basalis of Meynert) : Acetylcholine Reduced Ach → Alzheimer’s disease. Amygdala : Emotions & memory. Entorhinal cortex : Smell & olfactory memory. Language & Speech : Supramarginal gyrus Angular gyrus Broca’s area Wernicke’s area Primary Auditrory cortex Physiology Revision 1.0 Marrow 6.5 2023  28 04 Physiology ----- Active space ----- Broca’s area Wernicke’s area Arcuate Angular gyrus fasciculus Located in inferior Located at superior Bundle Area 39 frontal gyrus. temporal gyrus. connecting Brodmann’s area 44. Brodmann’s area 22. Broca’s & Motor speech area Word understanding & Wernicke’s Vision & speech (word formation). comprehension. areas. inter-related. Sensory speech area. Lesion : Reduced Lesion : Tremendous Lesion : Lesion : Anomic speech output problem in understanding Conduction aphasia (can’t (Broca’s aphasia). + fluent aphasia aphasia say what they (Wernicke’s aphasia). see). Fluids in brain 00:36:07 Cerebral blood flow (CBF) : For nutrition. Around 750 ml/min or 15% of cardiac output. O2 consumption : 20% of the total body resting O2 consumption. Regulation : 1. Autoregulation → Blood flow constant inspite of changes in pressure (65-140 mm Hg). 2. Hypercarbia → CBF 3. Hypothermia : of body temperature by 10C → cerebral blood flow by 7% (therapeutic hypothermia : Useful in neurosurgical procedures to reduce cerebral blood loss). Cerebrospinal fluid (CSF) : Volume : 150 ml Rate of CSF production : 550 mL/day CSF turn over per day : 3.7 times. Normal CSF pressure : 70-180 mm H20 (elevated pressure → Hydrocephalus) Chloride, magnesium, sodium CSF > Plasma Osmolality, Bicarbonate ions CSF = Plasma Glucose(2/3 plasma), proteins rd of CSF < Plasma CSF marker : β2-Transferrin (useful in CSF otorrhea, CSF rhinorrhea). Physiology Revision 1.0 Marrow 6.5 2023  Physiology Revision 4 04 29 Sleep 00:41:26 ----- Active space ----- EEG waves : EEG wave Frequency Characteristics Alpha wave 8 – 13 Hz Resting/ relaxed state. Eyes closed, not sleeping. Generated from occipital, parietal cortex. Beta wave 14 – 30 Hz Wide awake, attentive. Generated from frontal cortex. Theta wave 4 – 7 Hz NREM sleep (minor). Generated from hippocampus (memory). Delta wave/ < 4 Hz NREM sleep (major sleep wave). slow wave (minimum) Gamma wave 30–80 Hz (max) Focused attention. Sleep stages : NREM (Non rapid eye movement) sleep/ slow-wave sleep : Stage 1 : Non-specific theta waves. Stage 2 : K-complex & sleep spindles (8-13 hz ) Stage 3 & 4 : Delta waves (major waves of NREM). REM Sleep : PGO (ponto-geniculo-occipital) spikes → Eye ball movements seen. Both in males & females : Genital organ enlargement during sleep. Characteristic for REM : Beta wave (wakefulness + REM sleep) → Paradoxical sleep. Neurotransmitters in sleep : Wakefulness Neurotransmitters involved promoting brain areas Neurotransmitter NREM REM Cholinergic nuclei of Acetylcholine (REM ON pons-midbrain junction neurons → ACh → Sleep). Locus coeruleus Norepinephrine Raphe nuclei Serotonin Tuberomammillary Histamine nuclei Lateral hypothalamus Orexin (mutation : Narcolepsy). Physiology Revision 1.0 Marrow 6.5 2023  30 04 Physiology ----- Active space ----- Parasomnias : Disorders of NREM Disorders of REM Sleep talking. Nightmares. Sleep walking/Somnambulism. Narcolepsy. Teeth grinding/Sleep bruxism (NREM Meomory of stage 2 - emotionally deprived children). dream -ve. Nocturnal enuresis. Nightterrors. Note : Memory of the dream is present in night mares (REM) but absent in night terrors (NREM). Physiology Revision 1.0 Marrow 6.5 2023  Physiology Revision 5 05 31 PHYSIOLOGY REVISION 5 ----- Active space ----- Respiratory physiology 00:00:15 Airway generations : Weibel model (23 generations). Trachea → bronchi → bronchioles → terminal bronchioles (0) (16) alveolar sacs alveolar ducts respiratory bronchioles (23) Conducting airways (1-16) : First 16 generations. Contain cilia → ciliary movement d/t Dynein clears sputum. Dynein absent in Kartagener’s syndrome. Ciliary immotility : Cystic fibrosis. Has 2 stem cells : Basal cells & Clara cells (for lung regeneration & repair). Have smooth muscle. Agents that modify Bronchial smooth muscle activity: Bronchoconstriction Bronchodilation Parasympathetic system : ACh, Methacholine. Sympathetic system : β2 ag- Histamine. onists. Leukotriene (most potent). NO(Nitric oxide). Alveolar airways (17-23) : 2 types of pneumocytes : Type I : Large, flat, occupies more surface area, less numerous. Type II : Small, more numerous, produce surfactants (stored as lamellar bodies), act as stem cells. Composition of surfactants Surfactant lipids Surfactant proteins Major : Lecithin/dipalmitoyl phosphatidyl choline (DPPC) SP-A. Minor : Sphingomyelin. SP-B. L/S ratio is used to assess fetal lung maturity (normal SP-C. is ≥ 2). SP-D. Physiology Revision 1.0 Marrow 6.5 2023  32 05 Physiology ----- Active space ----- Functions of surfactants : Reduce surface tension → prevents alveolar collapse. SP-A & SP-D : Role in lung immunity. Production of surfactant : Accelerated by Inhibited by Cortisol (steroids). Insulin (inhibits cortisol) thus Infants of diabetic mothers T3, T4. are more prone to Hyaline membrane disease. Long term inhalation of 100% O2. Occlusion of main bronchus. Occlusion of one pulmonary artery. Smoking. Mechanics of breathing 00:12:15 Boyle’s Law : P ∝ 1/V 1. Intrapleural pressure : 2. Intra alveolar pressure : + 1 mm Hg -2.5 mm Hg -2.5 mm Hg Expiration Inspiration Expiration 0 mm Hg Inspiration -6 mm Hg - 1 mm Hg 3. Transpulmonary pressure = Alveolar pressure - Intrapleural pressure. (TAP : T = A - P). Lung compliance: Hys ation V Ins resis tion ir Exp te pira P Physiology Revision 1.0 Marrow 6.5 2023  Physiology Revision 5 05 33 Hysteresis : Difference b/w the pressure volume curves during inspiration & ----- Active space ----- expiration. It happens d/t surface tension forces. Compliance : Slope of the curve. = ΔV/ΔP = 200 mL/cm H2O. Note : For a given change in pressure, change in volume is more during expiration. Lung Compliance in air filled Vs saline filled lung : Saline filled Air filled Volume Pressure In saline filled lungs → no air-fluid interface → no surface tension → no hysteresis. Equilibrium volume(FRC) : The volume at which the 2 opposing forces (expanding force & collapsing force) are at equilibrium. Minimal volume : The volume of air remaining in the lungs after complete collapse. Compliance of chest wall (A), lung (B) and combined compliance (C). 1 Compliance in various diseases : ↑ compliance : Hyperinflation. Seen in COPD. ↓ compliance : Stiff lung. Seen in restrictive lung diseases (pulmonary fibrosis, interstitial lung disease). Physiology Revision 1.0 Marrow 6.5 2023  34 05 Physiology ----- Active space ----- Spirometry : Dynamic measurements : Flow volume curve. B A : TLC. B : Peak expiratory flow rate (PEFR). C : RV. A → B : Effort dependent part (air from A C trachea & bronchi). 6 4 2 0 B → C : Effort independent part (air from medium & small airways) - affected in COPD. FEV1, FVC and FEV1/FVC ratio can be measured from the graph. Note : Dog leg pattern/scooped out pattern : Seen in COPD. Miniature version of normal graph : Seen in restrictive lung diseases. Flow volume curves Physiology Revision 1.0 Marrow 6.5 2023  Physiology Revision 5 05 35 Spirometry cannot measure : These can be measured using : ----- Active space ----- 1. RV. 1. Helium dilution technique. 2. FRC. 2. Nitrogen washout technique. 3. TLC. 3. Body plethysmography (most practical). Ventilation : 00:38:30 Tidal volume (VT) = 500 mL. Dead space (VD) = 150 mL (air in conducting airways). Alveolar ventilation (VA) = 350 mL. VA/min = (VT-VD) x Respiratory rate(12). = 4.2 L/min. VD/VT = 30% (% of air which goes unexchanged). Dead space ventilation : Not used for gas exchange. 3 types : 1. Anatomical dead space (ADS). 2. Alveolar dead space (Alv DS). 3. Total dead space (ADS + Alv DS) : Physiological dead space. Measurement of ADS : Single breath N2 method/Fowler method. Measurement of physiological dead space : Bohr’s equation. PACO2 : Alveolar CO2. PECO2 : Expired CO2. VD : Physiological dead space. VT : Tidal volume. Bohr’s equation Perfusion : Pulmonary circulation (~5.5L/min) is unique as its response to hypoxia is pulmo- nary vasoconstriction. Mechanism : Hypoxia → Inhibits outward K+ current → K+ accumulation inside cell Vasoconstriction Opens Ca2+ channel Depolarisation causing Ca2+ influx Physiology Revision 1.0 Marrow 6.5 2023  36 05 Physiology ----- Active space ----- Lung zones : PA : Alveolar pressure. Pa : Arterial pressure. PV : Venous pressure. Blood flow distribution in the lung Blood flow Pressure Driving blood flow Minimal (d/t compression of PA ≥ Pa > PV blood vessels). Intermittent blood flow Pa > PA > PV (Waterfall effect). Middle Highest(Continuous blood flow) Pa > PV > PA Ventilation perfusion ratio (V/Q) : Alveolar ventilation(V) : 4.2 L/min. Pulmonary blood flow(Q) : 5.5 L/min. V/Q = 0.8 (in middle). It is more at apex (3.3) & less at base (0.6). V/Q = 0 (V=0) V/Q = Infinity (Q=0) Shunt blood (physiological). Anatomical dead space. Foreign body causing airflow obstruction. Pulmonary embolism. Diffusion of gases 00:53:32 Fick’s law governs the diffusion of gases in lung. Vgas : Diffusion of gas. A : Area. P1-P2 : Pressure difference. T : Thickness. CO : Gas of choice for measuring diffusion capac Physiology Revision 1.0 Marrow 6.5 2023  Physiology Revision 5 05 37 Normal value of DLCO (Diffusion Capacity of Lungs for CO2) = 25 mL/min/mm Hg. ----- Active space ----- ↓ DLCO ↑ DLCO ↓ membrane area : Emphysema. Polycythemia. ↑ thickness : Pulmonary fibrosis. Exercise. Anemia. Oxygen dissociation curve : X ift It is a sigmoid curve. t sh al rm Lef P50 : Partial pressure at which % ift No sh ht saturation of Hb with O2 is 50%. Rig P50 = 27 mm Hg. P50 Y Left/upward shift (Haldane effect) Right/downward shift (Bohr effect) Loading of O2 leading to unloading of Release of O2/ Unloading at CO2. Causes : tissue. Causes : Hypocarbia. Hypoxia. Alkalosis. Hypercarbia. Fetal Hb. Acidosis. CO poisoning. ↑ 2,3 DPG. Stored blood. High altitude. CO2 transport : AE : Anion exchanger. Chloride shift is aka Hamburger phenomenon : Buffered For each HCO3- that exits, a by HCO3- Cl- enters. Cl- shift Physiology Revision 1.0 Marrow 6.5 2023  38 05 Physiology ----- Active space ----- Regulation of respiration 01:07:39 Neural control : Brain area Function Pre Botzinger complex Pacemaker : Initiates respiration. Pneumotaxic center Limits inspiration (inhibits apneustic center). Controls respiratory rate. Apneustic center Prolongs inspiration. Dorsal Respiratory Generates RAMP signal for smooth Group (DRG) rise in tidal volume during inspiration. Ventral Respiratory Controls forceful expiration during Group (VRG) exercise. (Mnemonic - DIVE : D → Inspiration, V → Expiration) Chemical control : Central chemoreceptors Peripheral chemoreceptors Location Ventral surface of medulla. Carotid & aortic bodies. Sensitive to pCO2 in blood (As CO2 can ↓ pO2(Hypoxia) cross BBB & generate H+ Have oxygen sensors ions) (glomus cells). Direct stimulation by Rise in H+ ions in CSF. - Common stimuli to both chemoreceptors : Rise in H+ ions. Physiology Revision 1.0 Marrow 6.5 2023  Physiology Revision 5 05 39 Asphyxia : Rise in pCO2 & H+, fall in pO2. ----- Active space ----- Chemoreceptor activation Hyperventilation ↓ pCO2 ↓ H+ ↑ pO2 Pulmonary reflexes : Reflex Stimulus Receptor Afferent Effect Hering-Breuer Overstretch Pulmonary Large Inhibits inflation reflex. of lung. stretch myelinated inspiration. (Prevent injury) (TV = 1500 receptors (slow vagal fibres. ↑ duration of mL) adapting) expiration. Hering-Breuer Deflation. Pulmonary Large Inhibits deflation stretch myelinated expiration. reflex.(Prevent receptors (slow vagal fibres. ↓duration of collapse) adapting). expiration The paradoxical Lung Pulmonary Increase in lung reflex of head. inflation. stretch inflation. receptors. Responsible for first breath of newborn. J receptor Pulmonary Juxtapulmonary Unmyelinated Rapid reflex. edema, receptors vagal C fibres. breathing. pulmonary Bradycardia. congestion. Hypotension. Physiology Revision 1.0 Marrow 6.5 2023  40 05 Physiology ----- Active space ----- Periodic breathing patterns Cheyne Stokes Biot's breathing Kussmaul's breathing Apneustic spasm breathing (acidotic breathing) Seen in : Seen in : Seen in : Seen in : 1. Sleep (normal). 1. Injury to Diabetics. Midpontine lesion 2. CCF. Medulla. with vagus cut. 3. Uremia. 2. Meningitis. Types of hypoxia 01:24:24 Hypoxic Anemic Stagnant Histotoxic Features hypoxia hypoxia hypoxia hypoxia Due to Low arterial Reduced O2 Decreased Decreased ability pO2 content of blood flow of cells to use blood to tissues oxygen Arterial pO2 Decreased Normal Normal Normal Arterial Hb Normal Decreased Normal Normal content Peripheral Stimulated Not stimulated Stimulated Stimulated chemoreceptor (As dissolved O2 stimulation is normal) Example High altitude CO poisoning Ischemia Cyanide poisoning Environmental physiology 01:27:13 High altitude : Acclimatisation : Physiological compensatory response to high altitude. High altitude is a low pressure state. Hypoxia in high altitude ↑ ventilation ↑ EPO → ↑RBC Angiogenesis ↑ diffusion of ↑ O2 utility (earliest) production (↑ vascularity) gases by cells (cellular acclimatisation) Physiology Revision 1.0 Marrow 6.5 2023  Physiology Revision 5 05 41 Deep sea : ----- Active space ----- High pressure state → Gases are compressed. Decompression sickness/Caisson’s disease/Dysbarism/Diver’s palsy : Seen during rapid ascent to sea level → N2 gets decompressed & released out as bubbles. Clinical features : N2 narcosis. Bends (pain in joints). Chokes. Air embolism → death. Rx : Slow ascent → slow decompression → no bubbles. Space physiology : It is a state of microgravity. Positive G Negative G When an individual is subjected to When an individual is subjected to positive G, blood is pushed toward the negative G, blood is pushed toward the lowermost part of the body. head end. Venous pooling in lower limbs. ↑ Venous return : ↑ CO. ↓ Cerebral pressure : Unconsciousness. Congestion of head & neck vessels. ↓ Blood flow to eye : Black out. Hyperemia of eye : Red out. Physiology Revision 1.0 Marrow 6.5 2023  42 06 Physiology ----- Active space ----- PHYSIOLOGY REVISION 6 Cardiac action potentials 00:00:28 SA (Sino Atrial) nodal potential : SA node : Pacemaker & responsible for chronotropy. Ca2+ influx through L type Ca2+ Phase 0 Depolarisation channels. Phase 3 Repolarization Due to k+ efflux. 0 3 Decrease in k+ efflux. Prepotential Na+ influx through funny 4 4 Phase 4 (Pacemaker channels. potential) Ca2+ influx through T type Ca2+ channels. Effect of sympathetic & parasympathetic nervous system on SA nodal potential : Sympathetic nervous system Parasympathetic nervous (SNS) system (PNS) Increases Heart rate (HR). Decreases HR. Increases slope of prepotential Decreases slope of prepotential phase. phase. Ventricular action potential : Ventricles → Responsible for inotropy (contractility). Phase 0 Early depolarisation Due to Na+ influx. Phase 1 Early repolarisation Due to k+ efflux. 1 2 Phase 2 Plateau k+ efflux = Ca2+ influx through L type Ca2+ channels. 0 3 Phase 3 Late repolarisation Continuation of k+ efflux. Phase 4 Resting Membrane Na+ - k+ ATPase pump 4 Potential (RMP) Physiology Revision 1.0 Marrow 6.5 2023  Physiology Revision 6 06 43 Conducting system of the heart 00:08:26 ----- Active space ----- 1. SA node : Dominant pacemaker. Generates impulse at highest rate (100/min). 2. AV node : AV nodal delay (physiological). SA Node A-V Node A-V bundle Gatekeeper of heart. Left Slowest conduction velocity (0.04 m/s). bundle Inter branch 3. Bundle of His. Nodal Right pathways 4. Left & Right bundle branch. bundle branch 5. Purkinje fibres : Max. no. of gap junctions with connexins. Fastest conduction velocity (4 m/s). Purkinje fibres ECG 00:11:02 ECG waveforms : Wave Cause Duration (sec) P wave Atrial Depolarisation. 0. 10 QRS Complex Ventricular Depolarisation. 0. 08 to 0. 10 T Wave Ventricular repolarisation. 0. 2 U wave Purkinje fibre repolarisation. - Papillary muscle repolarisation. PR ST segment segment PR interval QT interval R R R T T T P P P PR U U U segment Q S ST segment Q S Q S RR interval ECG segments : Segments Extent Denotes PR segment From to the end of P wave to the Physiological AV nodal delay. beginning of QRS complex. ST segment End of QRS complex to the beginning Plateau phase of ventricular action of T wave. potential. Isoelectric line (J point). Note : Physiology : No current flow. Pathology : Injury current in MI (leads to ST elevation/depression). Physiology Revision 1.0 Marrow 6.5 2023  44 06 Physiology ----- Active space ----- ECG intervals : Intervals Extent Normal value Denotes/ Uses PR interval From the onset of P wave 0. 12 to 0. 20 S Atrioventricular (AV) conduction to the beginning of QRS time. complex. QT interval From the onset of Q wave 0. 35 to 0. 43 S Ventricular depolarization + to the end of T wave. repolarization events. RR interval Interval between two 0. 6 to 1 S HR = 1500/no. of small squares successive R waves. between two R waves. If PR interval > 0.20 seconds → Heart block. Jugular Venous Pressure (JVP) Waveforms 00:19:17 a c v y x JVP waveforms Corresponds to a wave Right atrial contraction (atrial systole). Bulging of tricuspid valve into right atrium during right ventricular c wave contraction. x descent Right atrial relaxation. v wave Venous filling (atrial diastole). y descent Venous emptying of right atrium into right ventricle. Cardiac cycle 00:21:21 Cardiac cycle duration → 60/Heart Rate → 0.8 seconds. Atrial Ventricular Systole (short) 0. 1 s 0. 3 s Diastole (long) 0. 7 s 0. 5 s Ventricular systole : Isovolumic contraction (IVC) Mitral and Aortic valves are closed. Rapid ejection Slow ejection Volume remains same & pressure phase (RE) phase (SE) → opening of the aortic valve. Physiology Revision 1.0 Marrow 6.5 2023  Physiology Revision 6 06 45 End systolic volume (ESV) : Volume of blood remaining in vent