Introduction to Physiology PDF

INTRODUCTION Prof. Mohammed Al-Hariri 1  Objectives Homeostasis Transport across cell membrane Action Potential Muscle Autonomic Nervous System 2  Physiology is the study of body functions Homeostasis aG  The body is structurally org...

INTRODUCTION Prof. Mohammed Al-Hariri 1  Objectives Homeostasis Transport across cell membrane Action Potential Muscle Autonomic Nervous System 2  Physiology is the study of body functions Homeostasis aG  The body is structurally organized into a whole functional unit. Its levels of organization are represented as follows: organism (the whole body) body system organ tissue cell molecule atom (smallest, most specific)  The cell is the basic unit of life. Basic cell functions are: obtain food and oxygen perform chemical reactions eliminate carbon dioxide and wastes synthesize proteins and cell components control exchange of materials moving materials sensitive, responsive to environmental changes reproduction The body systems are: circulatory digestive respiratory urinary skeletal muscular integumentary immune nervous endocrine reproductive Cell Interstitial fluid Blood vessel Plasma Extracellular fluid Extracellular fluid ↑ ECF serves as an intermediary between the cells and external environment All exchanges and of H2O and other H2 O the fluid always constituents between added to the leaves the body the ICF and the body fluids always by way of the external word occur enters the ECF ECF through the compartment ECF first  I The ECF is the internal environment  ECF Chemical composition Volume Pressure Temperature pH Osmolarity  Maintenance of a relatively stable internal environment is termed homeostasis Body systems maintain homeostasis. They maintain a dynamic steady state in the internal environment  Homeostasis is essential for cell survival Homeostasis  Control of homeostasis Negative Positive feedback feedback Negative feedback Positive feedback opposes an initial amplifies an initial change. change. It maintains homeostasis An output is enhanced. A controlled variable A controlled variable moves in the opposite moves in the direction direction of an initial change of an initial change  Mechanism of Homeostasis Negative Feed back (Stimulus & Response are in opposite direction) 16  Mechanism of Homeostasis Positive Feed back (Stimulus & Response are in same direction) 17  The usual control system for homeostasis commonly operates through the negative feedback system  Positive feedbacks are usually deleterious > - & and dangerous &&  Disruption in homeostasis can lead to illness and death. Pathophysiology is the abnormal functioning of the body during disease Are there any barriers to transport across cell membrane? Se d. Cell Membranes are semi-permeable structures that prevent most common biological compounds from moving across them. Lipid bilayer Tight Charge difference between outside & inside  Difference in total water inside & outside cell (Body Fluid Compartments) Intracellular: Inside cell Extracellular: Outside cell 22  The ICF and the ECF are separated by the membranes of the body's cells. The protein components of these membranes give them substantial permeability to water while carefully controlling the permeability of selected ions. 23  Ionic composition Plasma membrane ECF ICF Cations: + charged ions Anions: - charged ions 24  Differences between ECF & ICF ECF ICF Cations: Anions: Cations: Anions: Na+ (142mmol/L)Cl- (108mmol/L) Cl- (4mmol/L) Na+ (14mmol/L) K+ (4.2mmol/L) HCO3- (24mmol/L) HCO3- (10mmol/L) K+ (140mmol/L) Mg2+ (0.8mmol/L) Phosphate ions Mg2+ (20mmol/L) Nutrients: Nutrients: O2, glucose, fatty acids, & High concentrations of proteins. amino acids. Wastes: CO2, Urea, uric acid, excess water, & ions. 25  Transport Across Cell Membrane 26  Going Downhill is easy!! 27  What is the problem in going Needs Energy!! uphill? 28  What is the difference between A and B ? 29  PASSIVE TRANSPORT > high to lov - Diffusion The process by which molecules move from areas of high concentration to areas of low concentration. Does not need ATP energy. When the molecules are equal throughout a space - it is called EQUILIBRIUM 30 Active Transport Movement of materials S against a concentration gradient. It requires Energy (ATP) It needs a carrier protein. 31  Transport Across Cell Membrane 32  Types of membrane transport 1. Diffusion 2. Active transport (passive transport)  Net movement across Net movement of a membrane that occurs molecules & ions across against conc gradient. a membrane from higher (to region of higher conc) to lower concentration.  Requires metabolic (down conc gradient) energy (ATP), & involves Does not require specific carrier proteins. metabolic energy. 33  Na+- K+ Pump (an example of active transport) Exp The pump actively pumps 3 Na+ outside and 2 K+ to the inside. As both Na+ and K+ are moved against concentration gradient therefore energy (ATP) is required. It uses a special carrier protein that has 3 receptor sites for Na+ inside and 2 K+ on the outside The function of this pump results in the presence of more positive charges in the ECF that is important in generation of membrane potential. Prevents equal distribution of ions, therefore it contributes to maintaining the concentration gradients directly responsible for the ion movements that generate most of the membrane potential 34 Facilitated Diffusion 35  Endocytosis Endocytosis is the process by which cells absorb molecules (such as proteins) by engulfing them. It is used by all cells of the body because most substances important to them are large polar molecules that cannot pass through the hydrophobic plasma or cell membrane. 36  Phagocytosis & Pinocytosis Sold Y small Phagocytosis is the cellular process of Pinocytosis is a form of endocytosis - & engulfing ~ solid particles by the cell in which small - particles are brought membrane into the cell 37  Exocytosis = The process by which a cell moves the contents of secretory vesicles out of the cell membrane # 38  Osmosis the net diffusion of water down its own &is concentration gradient. Temperature regulati  Human body is more or less like a thermoflask with a hot liquid inside Inside At outer is the surface is the temperature temperature of hot of cold liquid surroundings Core Temperature Surface Temperature (Around 37°C( (Highly Variable) The central core is the abdominal and thoracic organs, the CNS, & the skeletal muscles.  Skin and subcutaenous fat constitute the ‘surface’.  Why do we need to regulate: Core (Internal) body temperature To provide the optimum conditions for enzyme-catalysed reactions to be carried out.  Body Temperature Normal internal body temperature is 370C Temperatures above this: denature enzymes and blocks metabolic pathways Temperatures below this: slows down metabolism and affect the brain.  Skin temperature Core temperature Peripheral Central thermoreceptors thermoreceptors (in skin) (in hypothalamus, other areas of CNS, Hypothalamic thermoregulatory & abdominal organs) center Behavioral Motor Sympathetic Sympathetic adaptations neurons nervous system nervous system Skeletal Skin blood Sweat glands muscles vessels Muscle tone, Skin vaso- shivering constriction Sweating & vasodilation Control of Control of Control of Control of heat production heat production heat loss heat loss or heat loss  > - lost heat 47  Infection of inflammation https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcQb4_4Gy6PzEv7LXXhI1S93u5iuDx_Cu_kWq_aluBm4ajWBpVFFyvIssNS7 During fever the hypothalmic Neutrophils thermostat is “reset” at an elevated temperature. Endogenous pyrogen White blood cells produce Prostaglandins endogenous pyrogens. In response to this the Hypothalamic set point hypothalamus gets set to an abnormal temperature. Initiation of “cold response” All body mechanisms produce Heat production; heat loss heat to take body to new temperature. Body temperature to new set point = Fever  Action potential 49  # Carons - cons Membrane Membrane has no potential 50  Membrane Membrane has potential F zig Remainder of Separated charges Remainder of fluid electrically responsible for fluid electrically 51 neutral potential neutral  timeing in rest the I ~ be more Plasma membrane Inside of cell membrane is NEGATIVE RESTING MEMBRANE POTENTIAL 52  https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcRrin90oFnU7JvcJYRfEexkL7POhvfWdul6_dGdep1YVCYolx-iOE4u-9E 29 j 3 53  Membrane Potential The cell membrane has slightly more positive ions on the outside, and slightly more negative ions on the inside. This difference produces a voltage, called membrane potential across the cell membrane. j = - bi = 1S) %9 The membrane potential is called the Resting Membrane Potential (RMP ) when this potential is measured in a resting ( not excited ) cell. The membrane potential is measured in millivolts (mV ). - 1 mV = 1 / 1000 Volt. 1899 -) = Example: The RMP in neurons is –70 mv; 70 means potential difference between both sides is 70 mv and – ‘negative’ describes the inside of the => membrane which is more negative than the outside.  55 jj S Generation of Membrane Potential Two factors contribute to generation of membrane potential: – The unequal distribution of ions across the membrane (and their selective movement through the plasma membrane ). – The Na+ - K+ pump  What is a stimulus? is A stimulus (pl. stimuli) is a detectable change in the internal or external environment 2015 Anything that has a potential to cause excitability Two Types: – Threshold Stimulus – Subthreshold stimulus  Changes in Membrane Potential Potential) 19 No more Is potential THRESHOLD STIMULUS  Changes in Membrane Potential Ji Polarization: at membrane potential Depolarization: The membrane potential is reduced & from RMP, decreased or moved towards Zero mV. Repolarization: Return of the membrane potential to s RMP after being depolarized. Hyperpolarization: The membrane potential is greater than the RMP; i.e it is more negative than RMP.  Action Potential - resting Ps ! T. [51 P hopen 59  Triggering event Depolarization (decreased membrane potential) Positive-feedback cycle Influx of Na+ Opening of some (which further voltage-gated decreases membrane potential) Na+ channels  At resting potential At resting potential all Na+ and K+ channels are closed  The Na+ gates Na+ activation gate opens open and the Na+ movement inside Threshold reached the cell progressively decreases the internal negativity Depolarizing triggering event Action potential Action potential begins begins Action potential continues until 0 mV is Explosive Action potential begins depolarization; reached potential reaches 0 mV  Na+ inactivation gate begins to close K+ gate opens Continued inward movement of Na+ reverses the potential Peak of action with the inside becoming potential; positive and the outside potential reversed becoming negative as the action potential peaks  At the peak of action potential, the Na+ gates close jegts - - and the K gates open. + Entry of Na+ ceases and K+ starts to leave the cell. Repolarization begins Outward movement of K+ makes the inside progressively less positive and the outside less negative  Na+ inactivation gate opens; Na+ activation gate closes Continued outward movement pf K+ restores the resting Action membrane potential potential complete; after hyperpolarization begins Further outward movement pf K+ through the still-open K+ gates transiently hyperpolarizes the membrane  then the After K+ gates close, and hyperpolarization is complete; the membrane return to resting Returns to potential resting potential Threshold potential Resting potential  The Na+/K+ pump gradually restores the concentration gradients disrupted by action potentials. Sodium is pumped into the ECF. Potassium is pumped into the ICF.  Other characteristics of the action potential include: Sodium channels open during depolarization by positive feedback. When the sodium channels become inactive, the channels for potassium open. This repolarizes the membrane. As the action potential develops at one point in the plasma membrane, it regenerates an identical action potential at the next point in the membrane. Therefore, it travels along the plasma membrane undiminished. Structure Of Muscle  Muscle Cells ( fibers ) dixI They are specialized for contraction. = "X) , jjt N Through their ability to contract, muscle cells can shorten and develop tension ( force) Through shortening and tension development, muscle cells can produce movement and d do work. · Y Sarcolemma: The plasma membrane of the muscle cell. - - be & Is I " 8211 Myofibril: a cylindrical bundle of contracting filaments within the skeletal muscle cells. Sarcoplasmic Reticulum ( SR ): The ER of the muscle cell. It’s interconnecting tubules - surround each myofibril Si like the sleeve of a loosely knit sweater. Myofibrils: Composed of individual contractile proteins called myofilaments, thin and thick filaments. The arrangement of thick and thin filaments forms light and dark alternating bands ( striations ) along the myofibril → striated appearance. 73 - - ( - > - X activ % - ↓ jo -9 - 12 will is there be something * A he will - attach to It - -  Each thick Myosin filaments is composed forms the thick of several hundred filaments myosin molecules Myosin molecules  Thin filaments are composed of Actin Tropomyosin Troponin & Molecules Molecules Has three spherical in are thread like polypeptide shape proteins units Actin Troponin O Y gitTropomyosin  is+ The ‘A’ band consists of thick filaments along with the portions of the thin filaments that overlap on both ends of the thick filaments The lighter area in the middle of the O ‘A’ band is the ‘H’ zone where the thin filaments do not reach  - - allowa pinkangle g ↑ 79  Terminal button T tubule Surface membrane of muscle cell Acetylcholine- Lateral Acetylcholine gated cation sacs of channel sarcoplasmic reticulum Troponin Tropomyosin Actin Cross-bridge binding Myosin cross bridge  xs X 81  Neuromuscular Junction calsem the is importion more to threa action activ S 15 341 , E I & 82  Autonomic Nervous System 19 83  Autonomic Nervous System It is the division of the nervous system that regulates the activities of the smooth muscle, cardiac muscle and glands. It consists of Sympathetic Nervous System Parasympathetic Nervous system 84 30  gla ] E Sliva-Row Row Par high Fata- hartreat reat respiratory > - 85  Autonomic Nerve Pathways The pathway of the ANS is from the CNS to effector organ This pathway consists of a two neurons chain: The cell body of the first neuron lies in the CNS The cell body of the second neuron lies in a ganglion ( a group of neurons located outside the - CNS ) yout 86  Autonomic Nerve Fibers Preganglionic Fibers They have their cell bodies in the CNS (spinal cord and brain) Their axons are myelinated The axon terminals synapse with one or more postganglionic neurons Postganglionic Fibers They have their cell bodies in the autonomic ganglia Their axons are unmyelinated Axon terminals supply the effector organs 87 Neurotransmitters of Autonomic Nervous System Parasympatheti (Acetylcholine) = > - Acetylcholine ( ACh ) The nerve fibers which release ACh are called cholinergic fibers Sites of release of ACh: 1. All sympathetic preganglionic fibers (including sympathetic supply to adrenal medulla) 2. All parasympathetic preganglionic fibers 3. All parasympathetic postganglionic fibers 4. Few sympathetic postganglionic fibers which supply sweat glands, blood vessels of skeletal muscles, skin and external genitalia ACh is quickly inactivated, so the effect of stimulation of cholinergic fibers is short and local. Receptors for Ach. are called cholinergic receptors. They are two types a)Nicotinic receptors and b) Muscarinic receptors Acetylcholine is neurotransmitter of Parasympathetic system 88  Neurotransmitters of Autonomic Nervous System (Norepinephrine) Norepinephrine (also called Noradrenaline) It is released from most sympathetic postganglionic fibers The nerve fibers which release norepinephrine are called adrenergic fibers. break dawn slowly It is slowly inactivated, so the effect of stimulation of sympathetic adrenergic is longer and more widespread than that of parasympathetic Receptors for nor epinephrine are called Adrenergic Receptors. Adrenergic receptors are of two types Alpha (α) receptors Beta (β) receptors Nor epinephrine is neurotransmitter of Sympathetic system 89  & Differences between Sympathetic & Parasympathetic Nervous system Sympathetic Parasympathetic Origin of Thoracic and lumbar segments of Brainstem and sacral regions of preganglionic fibers spinal cord spinal cord (thoracolumbar outflow ) ( craniosacral outflow ) Length of fibers Preganglionic: Very short Preganglionic: Very long Postganglionic: Very Long Postganglionic: very short Synapse of Each preganglionic fiber synapses Each preganglionic fiber synapses preganglionic fibers with many postganglionic neurons with few postganglionic neurons on postsynaptic nerons Distribution Distributed throughout the body Limited to head and viscera of thorax, abdomen and pelvis Activity Mostly discharges during activity Discharges during rest and sleep (such as exercise and stress) mainly Response Generalized response in the body Localized response in certain organs se because of the wide distribution of supplied its fibers 90  Effect of Autonomic Nervous System Organs Sympathetic Parasympathetic Eye Dilation of pupil Constriction of pupil Sweat glands Increase secretion ------------------------ Lung Broncho-dilation jogts Broncho-constriction Heart ↑ Increase heart rate Decrease heart rate = Increase force of contraction n Stomach and Decrease motility and tone Increase motility and - > intestine Constrict sphincters tone & Relax sphincters Urinary bladder Relax the wall Contract the wall Contract the sphincter Relax the sphincter 91 92