A&P I Unit 1 Introduction 2023-2024 PDF

WHAT DO WE MEAN with “ANATOMY”? Greek or Latin: Ana: Up. Tomia: Cutting. “Science that studies body structures and the relationships among them.” ©Copyright Universidad Europea. Todos losderechos reservados WHAT DO WE MEAN with “PHYSIOLOGY”? “It is the science that studies thevital functions of...

WHAT DO WE MEAN with “ANATOMY”? Greek or Latin: Ana: Up. Tomia: Cutting. “Science that studies body structures and the relationships among them.” ©Copyright Universidad Europea. Todos losderechos reservados WHAT DO WE MEAN with “PHYSIOLOGY”? “It is the science that studies thevital functions of living organisms.” ©Copyright Universidad Europea. Todos losderechos reservados WHAT DO WE MEAN with “HISTOLOGY”? “Science that studies the microscopic structure of tissues.” A tissue is a: • Group of similar cells that usually have a similar embryological origin and are specialized for a particular function. AND • The extracellular components around the cells (extracellular matrix). ©Copyright Universidad Europea. Todos losderechos reservados LEVELS OF STRUCTURAL ORGANIZATION Atoms Organs Systems Molecules C ells Tissues ORGANISM ©Copyright Universidad Europea. Todos losderechos reservados LEVELS OF STRUCTURAL ORGANIZATION Cellular Cell Structural and functional unit of living organisms. It is the smallest unit of life that c an replicate independently. Growth - C ommon c harac teristics: Reproduc tion Relation Energy produc tion LEVELS OF STRUCTURAL ORGANIZATION Tissues & organs Tissues: groups of similarly specialized cells and the substances surrounding them that usually arise from a common ancestor and perform certain special functions. Organ: structures of definite form that are composed of two or more different tissues and have spe cific functions. ©Copyright Universidad Europea. Todos losderechos reservados LEVELS OF STRUCTURAL ORGANIZATION Systems and organism Systems: related organs with a common function. They work in a coordinated way & they perform a specific biological function. Organism: human body. ©Copyright Universidad Europea. Todos losderechos reservados BASIC VITAL PROCESSES Metabolism is the sum of all c hemic al proc esses that oc c ur in the body, including c atabolism and anabolism. Responsiveness is the ability to dete ct and respond to c hanges in the external or internal environment. Movement inc ludes motion of the whole body, individual organs, single c ells, or even organelles inside c ells. ©Copyright Universidad Europea. Todos losderechos reservados BASIC VITAL PROCESSES • Growth refers to an increase in size and complexity, due to an increase in the number of cells, size of cells and/or increase in the amount of interstitial fluid between c ells. • Differentiation is the change from an unspecialized state to a specialized state. • Reproduction refers either to the formation of new cells for growth, repair, or replacement, or the production of a new individual. ©Copyright Universidad Europea. Todos losderechos reservados HOMEOSTASIS From Greek homos (ὅμος) which means "similar", and estasis (στάσις) "position” or ”estate of stability”. “Homeostasisis the ability of a living system (body or c ell) to maintain the equilibrium in its internal environment”. Thanks to the constant interaction of the body’s many regulatory processes certain conditions are kept stable within a narrow value range” ©Copyright Universidad Europea. Todos losderechos reservados HOMEOSTASIS Homeostasis is the maintenance of the variables in the internal medium (pH, temperature, concentration of ions and molecules - oxygen, carbon dioxide, glucose-, volume...) in a dynamic equilibrium. ©Copyright Universidad Europea. Todos losderechos reservados FACTORS THAT INFLUENCE HOMEOSTASIS • Internal: stress, exerc ise, immune response … – Ac c umulation of waste produc ts from metabolic reactions. • External: heat, c old, c hanges in partial pressure of oxygen, infections… • Physiologic al disruptions in the internal medium (extrac ellular fluid) are usually mild & temporary. • A permanent lack of homeostasis leads to disease. ©Copyright Universidad Europea. Todos losderechos reservados PROPERTIES OF HOMEOSTASIS 1. Both the nervous and endocrine systems are equally important in maintaining regulatory mechanisms. 2. Tonic level of activity: there is a basal level of activity that can be slightly modified either up or down. 3. Antagonic control: if a factor can revert a change towards an homeostatic state in one direction, there will be another factor or factors with opposite effects. 4. Chemical signals can have different effects on different tissues. ©Copyright Universidad Europea. Todos losderechos reservados A CLOSER LOOK INTO HOMEOSTASIS Organism in homeostasis External c hange Internal c hange Equilibrium lost (Loss of homeostasis) Mechanisms of compensation Lack of compensation Disease ©Copyright Universidad Europea. Todos losderechos reservados Compensation Health BODY FLUIDS: HOMEOSTATIC FLUIDS Maintaining volume and composition of fluids is essential for life. ©Copyright Universidad Europea. Todos losderechos reservados BODY FLUIDS: HOMEOSTATIC FLUIDS “Multicellular organisms are immersed in external medium. Their c ells are immersed in an internal medium through which they communicate with the exterior (take nutrients and eliminate waste). The internal medium is continually renovated by blood.” (C laude Bernard, 1850) Extracellular fluid (ECF) is Claude Bernard’s “internal medium.” ©Copyright Universidad Europea. Todos losderechos reservados BODY FLUIDS: HOMEOSTATIC FLUIDS TYPES OF LIQUID COMPARTMENTS For the body’s c ellsto survive, the c omposition of the surrounding fluidsmust be kept c onstant at all times. ICF ECF= Plasma +IF ©Copyright Universidad Europea. Todos losderechos reservados BODY FLUIDS: HOMEOSTATIC FLUIDS TYPES OF LIQUID COMPARTMENTS Intracellular fluid (ICF): inside body cells. Extracellular fluid (ECF): outside body c ells.  Interstitial fluid (IF): EC F filling the narrow spac es between c ells of tissues. Also called intercellular fluid, tissue fluid or body’s internal environment. Proper function of body cells depends on precise regulation of IF. Exchange of nutrients and waste. It includes the lymph.  Plasma.  Transcellular fluid: fluids from the synovial, peritoneal, pericardial, intraocular spaces and cerebrospinal fluid. Its composition may differ from the IF and the plasma. ©Copyright Universidad Europea. Todos losderechos reservados BODY FLUIDS: HOMEOSTATIC FLUIDS TYPES OF LIQUID COMPARTMENTS 60 %of the body weight is water, 2/3correspond to intracellular fluid and 1/3 is extracellular fluid. ©Copyright Universidad Europea. Todos losderechos reservados BODY FLUIDS: HOMEOSTATIC FLUIDS IMPORTANT INFORMATION: 1. Chemical composition is DIFFERENT between ECF and ICF (solutes distribute differently among the fluid compartments). 2. TOTAL concentration of solutes (OSMOLARITY) is the same. In homeostasis, fluid c ompartments have the same osmolarity (isosmotic) which is 300 mOsm/L. ©Copyright Universidad Europea. Todos losderechos reservados BODY FLUIDS: HOMEOSTATIC FLUIDS COMPOSITION and OSMOTIC contribution Plasma (mOsm/L of H2O) Interstitial (mOsm/L of H2O) Intracellular (mOsm/L of H2O) Fluid compartments are chemically different. Fluid compartments are electrically balanced. During homeostasis, fluid compartments are isosmotic (300 mOsm/L) among themselves. ©Copyright Universidad Europea. Todos losderechos reservados Fluid compartments are under osmotic equilibrium (NOT under CHEMICAL EQUILIBRIUM) . The c ell membrane is semipermeable. • Water moves freely from one side to the other and contributes in maintaining the osmolarity. • Solutes could be non permeant (NP) or permeants (P). ©Copyright Universidad Europea. Todos losderechos reservados OSMOSIS Movement of water Important: if water moves through the plasma membrane (osmosis) and the volume of the ICF changes, cell functions c an be dramatically altered. Depending on the amount and nature of solutes dissolved in it, a solution might behave as: ©Copyright Universidad Europea. Tod os losderechos reservados REGULATION of HOMEOSTASIS Maintaining the internal equilibrium All functions that take place within our organism aim at keeping a constant internal medium. Homeostasis means maintaining the different variable conditions of the internal medium within constant limits, in a dynamic equilibrium (pH, temperature, ion concentration, oxygen, carbon dioxide, glucose, volume...). ©Copyright Universidad Europea. Todos losderechos reservados REGULATION of HOMEOSTASIS General principles: body control mechanisms. • Any disruption that changes a controlled condition is called a stimulus. O rga nism in homeosta sis Internal c ha nge External c ha nge • A feedback system is a cycle of events in whic h information about the status of a condition is continually monitored and reported to and controlled by a c entral c ontrol region. ©Copyright Universidad Europea. Todos losderechos reservados Equilibrium lost (Loss of homeostasis) Mechanisms of c ompensa tion COMPONENTS OF THE REFLEX RESPONSE Bringing it back to our body • Stimulus: c hanges in temperature, pressure, pH… that ac tivate a pathway. • Sensor or receptor (sensory receptor): monitors changes in a controlled condition. Receptors: • Taste, smell, touc h… • Thermoreceptors, noc ic eptors, baroreceptors. • C entral and peripheral. Threshold: value below which the feedback loop is not activated. • Afferent pathway: c onnects the sensory receptor with the c ontrol centre. - Nervous system: afferent neurons. -Endoc rine system: the endoc rine c ells ac ts as both receptor and integration c entre. ©Copyright Universidad Europea. Todos losderechos reservados COMPONENTS OF THE REFLEX RESPONSE • Control (integration) centre: sets the range of values within whic h a controlled condition should be maintained, evaluates the input it receives from the receptors, and generates output commands when they are needed. • Efferent pathway: output signal (c hemic al or electric al). • Nervous system: efferent neurons. • Endoc rine system: hormones. • Effector: a body structure that receives efferent information from the control centre and produces a response or effect that changes the c ontrolled c ondition. • Response: • C ellular response. • Systemic response. ©Copyright Universidad Europea. Todos losderechos reservados REGULATION OF A REFLEX RESPONSE Nervous and endocrine control Nervous reflex Endocrine reflex Signal Electrical + chemical (neurotransmitters) Specificity Each neuron ends on a Most of the cells in the single target cell or on a organism are exposed to the limited number of hormone. Response depends neighbouring cells. on the presence of receptors. Onset of effects Very fast. Slow. Duration of effects Short. Long. Intensity Related to the frequency Related with the amount of of the nerve impulse. secreted hormone in blood. Chemical (hormones) Both mechanisms work together to restore the equilibrium. ©Copyright Universidad Europea. Todos losderechos reservados MODULATION OF A REFLEX RESPONSE • Negative feedbac k: • If a response reverses the original stimulus, it is a negative feedbac k system. • Positive feedbac k: • If a response enhances the original stimulus, it is a positive feedbac k system. • Anticipation. ©Copyright Universidad Europea. Todos losderechos reservados MODULATION OF A REFLEX RESPONSE NEGATIVE FEEDBACK • Most frequent mechanism. •RESPONSIBLE FOR HOMEOSTASIS. KEEPING THE Homeostatic mechanisms. •The response reverses a change in a controlled condition. E.g. blood pressure  The activity of the effector produces a result (a drop in blood pressure) that opposes the stimulus (an increase in blood pressure). ©Copyright Universidad Europea. Todos losderechos reservados MODULATION OF A REFLEX RESPONSE POSITIVE FEEDBACK • Not as frequent. •The response favours the change that started it. •The stimulus triggers a positive signalling loop that will continue until an external factor stops it. ©Copyright Universidad Europea. Todos losderechos reservados MODULATION OF A REFLEX RESPONSE ANTICIPATION •A response is initiated before the stimulus appears. •“Preparation” of the body in anticipation to a new stimulus. • E.g.: salivation. ©Copyright Universidad Europea. Todos losderechos reservados