Principles of Physiology Lecture Notes PDF

 Physiology study of how animals and plants work (Knut Schmidt-Nielsen) focuses on the function of tissues, organs, and organ systems in multicellular organisms. Physiology is an Integrating Science How did a system evolve? What were the survival advantages for this feature...

 Physiology study of how animals and plants work (Knut Schmidt-Nielsen) focuses on the function of tissues, organs, and organ systems in multicellular organisms. Physiology is an Integrating Science How did a system evolve? What were the survival advantages for this feature? How does ontogeny reflect evolution? integrative science – brings together everything known about an animal’s function to create an integral picture of how an animal operates in its environment  Physiologist study the structure and function of the various parts of animals and plants; how these parts work together to allow organims to perform their normal behaviours and respond to their environment. design experiments - learn about the control and regulation of processes within groups of cells and how the combined activities of these cell groups affect the function of the animal. Diversity - hallmark of physiology meeting the demands of survival has resulted in numerous evolutionary variations on the basic theme of life Unifying themes of physiological processes obey physical and chemicals laws regulated to maintain internal conditions and trigger an appropriate response physiological state of an animal is part of its phenotype, which arises as the product of the genetic make-up, or genotype, and its interaction with the environment.  Comparative Physiology o species are compared in order to discern physiological and environmental patterns Environmental Physiology o examines oragnisms in the context of the environments they inhabit (evolutionary adaptations) Subdisciplines of Physiology Evolutionary Physiology o techniques of evolutionary biology and systematics are used to understand the evolution of organisms from physiological viewpoint, focusing on physiological markers rather than anatomic markers Developmental Physiology o how physiological processes unfold during the course of organism development from embryo through larva or fetus to adulthood Subdisciplines of Physiology Cell Physiology o vital information on the physiology of the cells themselves, which can be used to understand the physiological responses of tissues, organs, and organ systems Central Themes in Physiology 1. Structure/Function Relationships Function is based on structure – form fits function at all the levels of life, from molecules to organisms – Knowledge of a structure provides insight into what it does and how its works – Conversely, knowing the function of a structure provides insight about its construction  This structure-function relationship is clear in the aerodynamic efficiency in the shape of bird wing. ◦ A honeycombed internal structure produces light but strong bones. ◦ The flight muscles are controlled by neurons that transmit signals between the wings and brain. ◦ Ample mitochondria provide the energy to power flight.  Some plants within a population exhibit variation in leaf structure. Deer prefer a diet of smooth leaves over hairy leaves. Plants with Structure/Function hairy leaves reproduce more than other plants in the population. Relationships Generations later, most plants within the population have hairy leaves, as smooth leaves are selected against. Organism Organ system Organ and Cellular Macromolecular Molecular level level Tissue levels level level level 0.2 mm 20 µm 2 µm 200 nm 20 nm 2 nm 0.2 nm Cells Molecules Organelles Atoms biological function at each level of organization depends on the structure of that level and the levels below 2. Adaptation, Acclimatization, and Acclimation Physiology of an organism is very well matched to the environment it occupies, thereby ensuring its survival Adaptation o evolution through natural selection leading to an organism whose physiology, anatomy, and behavior are matched to the demands of its environment o generally irreversible;  a physiological process is adaptive - present at high frequency in the population because it results in a higher probability of survival and reproduction than alternative processes. physiological and anatomic adaptations - genetically based, passed on from generation to generation (DNA) and constantly shaped and maintained by natural selection Some plants within a population exhibit variation in leaf structure. Deer prefer a diet of smooth leaves over hairy leaves. Plants with hairy leaves reproduce more than other plants in the population. Generations later, most plants within the population have hairy leaves, as smooth leaves are selected against. Acclimatization a physiological, biochemical, or anatomic change within an individual animal during its life that results from an animal’s chronic exposure in its native habitat to new, naturally occurring environmental condition animal in migrate to high altitude Acclimation refers to the same process as acclimatization when the changes are induced experimentally in the laboratory or in the wild by an investigator animal placed in hypobaric chamber o both are reversible Variation, change, and evolution  The tendency of organisms to regulate and maintain relative internal stability  Claude Bernard (1872) ◦ French pioneer of modern physiology ◦ The milieu interieur ◦ “Constancy of the internal environment is the condition of free life” ◦ the ability of animals to survive in often stressful and varying environments directly reflects their ability to maintain a stable internal environment.  Walter B. Cannon (1871-1945) oextended notion of internal consistency to the organization and function of cells, tissues and organs o “Homeostasis” – tendency towards internal stability (1929 – Nobel Price) oThe evolution of homeostasis and the physiological systems that maintain it were essential factors in allowing animals to venture from relatively “physiologically friendly” environments and invade habitats more hostile to life processes.  Insulin and glucagon are antagonistic hormones that help maintain glucose homeostasis pancreas has clusters of endocrine cells called islets of Langerhans with alpha cells that produce glucagon and beta cells that produce insulin Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Hypoinsulinism: diabetes mellitus  hereditary factors and obesity play a role in its development  high blood sugar levels – sugar excreted in the urine  symptoms: excessive urination and excessive thirst  if severe: fat substitutes for glucose as major fuel source → production of acidic metabolites → life threatening lowering of blood pH  Type I diabetes mellitus (insulin-dependent diabetes)  autoimmune disorder  usually appears in childhood  treatment: insulin injections  Type II diabetes mellitus (non-insulin-dependent diabetes)  usually due to target cells having a decreased responsiveness to insulin  usually occurs after age 40 – risk increases with age  accounts for over 90% of diabetes cases Euryhaline animals can survive large fluctuations in external osmolarity  Some aquatic invertebrates in temporary ponds lose almost all their body water and survive in a dormant state  This adaptation is called anhydrobiosis Dehydrated tardigrade 4. Feedback – Control Systems regulatory processes that maintain homeostasis in the cells and multicellular organisms depend on feedback feedback – return of information to a controller that regulates a controlled variable feedback – occurs when sensory information about a particular variable (e.g. temperature, pH, salinity) is used to control processes in the cells, tissues, and organs that influence the internal level of that variable Negative feedback systems and loops Pathway Example – Stimulus Low pH in negative duodenum feedback – a S cells of duodenum loop in which secrete secretin ( ) the response Endocrine cell reduces the Blood vessel initial stimulus Target Pancreas cells Response Bicarbonate release Positive feedback Pathway Example systems and loops Stimulus Suckling + Sensory neuron positive Hypothalamus/ posterior pituitary feedback - Positive feedback where the Neurosecretory cell Posterior pituitary stimulus leads to Blood secretes oxytocin ( ) an even greater vessel response Target Smooth muscle in cells breasts Response Milk release 5. Conformity and Regulation when an organism is confronted with changes in its environment (e.g. changes in oxygen availability or salinity), it can respond in one or two ways: conformity or regulation oconformers – environmental challenges induce internal body changes that simply parallel the external conditions (unable to maintain homeostasis) e.g. osmoconformers – shark, starfish Oxyconformers – annelid worms oregulators – biochemical, physiological, behavioral, and other mechanisms to regulate their internal environment over a broad range of external environmental changes (maintain homeostasis) Osmoregulators – maintain ion concentrations of body fluids above environmental levels when placed in dilute water vice versa Osmoregulation is based largely on controlled movement of solutes between internal fluids and the external environment