PHYSIOLOGY LECTURE Dr. Mehmet Emin USLU, PhD
Each physiological system is composed of discrete organs, such as the liver, heart, lungs, and kidneys. These organs are made up of assemblages of cells known as tissues. Although there are many specialized cell types, there are only four kinds of tissues: epithelial muscle Connective nervous
Epithelial tissues are sheets of densely packed, tightly connected epithelial cells. Epithelial cells create boundaries between the inside and the outside of the body and between body compartments; they line the blood vessels and make up various ducts and tubules. epithelial cells in the deepest layer of the skin have a high rate of cell division, producing new cells that move progressively to the skin surface, die, and are shed.
cross section of the skin reveals the layering of cells, from the newly formed ones on the innermost germinal layer to the dead ones on the surface. Because of this appearance, the skin is called a stratified epithelium Some secrete hormones, milk, mucus, digestive enzymes, or sweat. Others have cilia that move substances over surfaces or through tubes. Epithelial cells can also provide information to the nervous system like Smell and taste receptors.
Muscle tissues consist of elongated cells that contract to generate forces and cause movement. Muscle tissues are the most abundant tissues in the body, and they use most of the energy produced in the body. All muscle cells contain long protein polymers called actin and myosin which interact to cause muscle cells to contract and exert force There are three types of muscle tissues Skeletal Cardiac Smooth
Skeletal muscles (so named because they mostly attach to bones) are responsible for locomotion and other body movements such as facial expressions, shivering, and breathing. Cardiac muscle makes up the heart and is responsible for the beating of the heart and the pumping of blood. Individual cardiac muscle cells are branched, and the interweaving of these branches gives heart muscle structural strength. Smooth muscle is responsible for involuntary generation of forces in many hollow internal organs such as the gut, bladder, and blood vessels. Skeletal muscles are under both voluntary and involuntary control. Cardiac and smooth muscles are under involuntary control; they are controlled by physiological regulatory systems.
CONNECTIVE TISSUES In contrast to densely packed epithelial and muscle tissues Connective tissues are generally dispersed populations of cells embedded in an extracellular matrix that they secrete The composition and properties of the matrix differ among types of connective tissues. Protein fibers are an important component of the extracellular matrix of connective tissue cells. The dominant protein in the extracellular matrix is collagen, which makes up about 25 percent of total body protein. Collagen fibers are strong and resistant to stretch,
Elastin is another type of protein fiber in the extracellular matrix of connective tissues. It is so named because it can be stretched to several times its resting length and then recoil. Fibers composed of elastin are most abundant in tissues that are regularly stretched, such as the walls of the lungs and the large arteries. Cartilage and bone are connective tissues that provide rigid structural support. In cartilage, a network of collagen fibers is embedded in a flexible matrix consisting of a protein carbohydrate complex, along with a specific type of cell called a chondrocyte.
Adipose cells form loose connective tissue that stores lipids. Adipose tissue, or fat, is a major source of stored energy. It also cushions organs, and layers of adipose tissue under the skin can provide a barrier to heat loss. Blood is a connective tissue consisting of cells dispersed in an extensive liquid extracellular matrix, the blood plasma.
NERVOUS TISSUES The two basic cell types in nervous tissues are neurons and glial cells Neurons come in many shapes and sizes, and all neurons encode information as electrical signals. These signals can travel over long extensions called axons to communicate with other neurons, muscle cells, or secretory cells through the release of chemicals called neurotransmitters. Neurons control the activities of most organ systems. Glial cells do not generate or conduct electrical signals, but they provide a variety of supporting functions for neurons. There are more glial cells than neurons in the nervous system.
Organs include more than one kind of tissue, and most organs include all four The wall of the gut is a good example. Its inner surface is lined with a sheet of columnar epithelial cells. Different epithelial cells secrete mucus, enzymes, or stomach acid. Beneath the epithelial lining is connective tissue. Within this connective tissue are blood vessels, neurons, and glands Concentric layers of smooth muscle tissue enable the gut to contract to mix food with digestive juices. Anetwork of neurons between the muscle layers controls these movements
HORMONES In multicellular animals, physiological control and regulation require information and cell-to-cell communication. Most intercellular communication is by means of chemical signals that bind to receptors. Hormones are chemical signals that are released by certain types of cells and that influence the activities of other cells at a distance
The information that animals use to develop, grow, and function comes from four major sources: the genome the endocrine system the immune system the nervous system. Information is encoded in the specificity of chemical signals and their receptors. there are also receptors in the nervous system that encode physical sources of information, such as temperature, pressure, and light. the nervous system uses electrical signals called action potentials to get information from place to place in the body.
endocrine system includes a variety of cells that produce and release hormonal chemical signals into the extracellular fluid. Endocrine cells secrete chemical signals; target cells have receptors for those signals. Chemicals secreted into the extracellular fluid diffuse locally and may diffuse into the blood. Endocrine signals that enter the blood are called hormones, and they can activate target cells far from their site of release Testosterone is an example of a hormone.
Some endocrine signals are released in such tiny quantities, or are so rapidly inactivated by enzymes, or are taken up so efficiently by local cells that they never diffuse into the blood in sufficient amounts to act on distant cells. Because these signals affect only target cells near their release site, they are called paracrines When a chemical signal influences the cell that secreted it, it has autocrine function. Hormones and paracrines can have autocrine functions as a means of providing negative feedback to control their rates of secretion
Some endocrine cells exist as single cells within a tissue. Hormones of the digestive tract, for example, are secreted by isolated endocrine cells in the walls of the stomach and small intestine. Many hormones, however, are secreted by aggregations of endocrine cells forming secretory organs called endocrine glands. The name endocrine reflects the fact that these glands secrete their products directly into the extracellular fluid, which they pass into the blood. In contrast, exocrine glands, such as sweat glands or salivary glands, have ducts that carry their products to the surface of the skin or into a body cavity such as the gut. A single endocrine gland may secrete multiple hormones.
Neurons, the cells of the nervous system, conduct information over long distances as electrical signals, but where a neuron communicates that information to another cell, be it another neuron, a muscle cell, or a secretory cell, itdoes so by releasing chemical signals called neurotransmitters. Most neurotransmitters act very locally and frequently act on the neuron that released them. Some eurotransmitters, however, diffuse into the blood and are therefore referred to as neurohormones. Pheromones are chemical signals that an animal releases into the environment to communicate information to other individuals of the same species.
IMMUNITY Animals have a number of ways of defending themselves against pathogens harmful organisms and viruses that can cause disease. These defense systems are based on the distinction between self the animal s own molecules and nonself, or foreign, molecules. The defensive response involves three phases: Recognition phase. The organism must be able to discriminate between self and nonself. Activation phase. The recognition event leads to a mobilization of cells and molecules to fight the invader. Effector phase. The mobilized cells and molecules destroy the invader.
There are two general types of defense mechanisms: Nonspecific defenses, or innate defenses, provide the first line of defense against pathogens. They typically act very rapidly, and include barriers such as the skin, molecules that are toxic to invaders, and phagocytic cells (phagocytes, such as macrophages) that ingest invaders. This system recognizes broad classes of organisms or molecules and gives a quick response, within minutes or hours. Most animals have nonspecific defenses.
Specific defenses are adaptive mechanisms aimed at specific pathogens. For example, a specific defense system can make an antibody protein that will recognize, bind to, and aid in the destruction of a certain virus if that virus ever enters the bloodstream. These systems recognize specific configurations of atoms in a molecule and are typically slow to develop and longlasting. Specific defense mechanisms are found in vertebrate animals.
REPRODUCTION Sexual reproduction is a nearly universal trait in animals, although many species can also reproduce asexually and some reproduce only asexually. Offspring produced asexually are genetically identical to one another and to their parents. Asexual reproduction is efficient because no time or energy is wasted on mating and every member of the population can convert resources into offspring. Asexually reproducingspecies are likely to be found in relatively constant environments where genetic diversity is less important for species success. Three common modes of asexual reproduction are budding, regeneration, and parthenogenesis
Many simple multicellular animals produce offspring by budding. New individuals form as outgrowths or buds from the bodies of older animals A bud grows by mitotic cell division, and the cells differentiate before the bud breaks away from the parent The bud is genetically identical to the parent, and it may grow as large as the parent before it becomes independent.
Sexual reproduction in animals consists of three fundamental steps: Gametogenesis: making gametes Spawning or mating: bringing gametes together Fertilization: fusing gametes
Gametogenesis occurs in the gonads, which are testes (singular testis) in males and ovaries (singular ovary) in females. The tiny gametes of males, the sperm, move by beating their flagella. The larger gametes of females, called eggs or ova (singular ovum), are nonmotile. Gametes are produced from germ cells, which have their origin in the earliest cell divisions of the embryo and remain distinct from all the other cells of the body (the somatic cells). Germ cells are sequestered in the body of the embryo until its gonads begin to form.
The germ cells then migrate to the developing gonads, where they take up residence and proliferate by mitosis, producing spermatogonia (singular spermatogonium) in males and oogonia (singular oogonium) in females. Spermatogonia and oogonia are diploid and multiply by mitosis. meiotic cell division reduces the chromosomes to the haploid number The spermatogonia and oogonia that enter meiosis are primary spermatocytes and primary oocytes. Although the steps of meiosis are similar in males and females, gametogenesis differs between the sexes.
DEVELOPMENT in animals that reproduce asexually, development proceeds without fertilization. in animals where fertilization does occur, it is preceded by critical events in the maturing egg that will influence subsequent development. The fusion of sperm and egg plasma membranes accomplishes several things: It sets up blocks to the entry of additional sperm. It stimulates ion fluxes across the egg membrane. It changes the egg s ph. It increases egg metabolism and stimulates protein synthesis. It initiates the rapid series of cell divisions that produce a multicellular embryo.
In most species, eggs are much larger than sperm. Egg cytoplasm is well stocked with organelles, nutrients, and a variety of molecules, including transcription factors and mrnas. The sperm is little more than a DNA delivery vehicle. Nearly everything the embryo needs during its early stages of development comes from the mother the sperm makes another important contribution to the zygote in most species a centriole. The centriole becomes the centrosome of the zygote, which organizes the mitotic spindles for subsequent cell divisions The centriole is also the origin of the primary cilia of cells, which are important in cell signaling, as we saw in the opening story about situs inversus.
Cytoplasmic factors in the egg play important roles in setting up the signaling cascades that orchestrate the major events of development: Determination Differentiation Morphogenesis The entry of the sperm into the egg stimulates rearrangements of the egg cytoplasm that introduce additional organization to the egg cytoplasm. This rearrangement establishes the polarity of the zygote, and when cell divisions begin, the informational molecules that will guide development are not divided equally among daughter cells.
NEURONS Nervous systems are composed of two types of cells: 1. nerve cells (neurons) 2. glial cells, (glia) Neurons are excitable: they can generate and transmit electrical signals,which are known as nerve impulses, or action potentials Many neurons have a long extension called an axon that enables them to conduct action potentials over long distances. Glia do not conduct action potentials; rather, they support neurons physically, immunologically, and metabolically. A nerve (as distinct from a neuron) is a bundle of axons that come from many different neurons. Many axons are wrapped by glia to electrically isolate them and increase their speed of conduction of action potentials.
Nervous systems can process information because their neurons are organized into neural networks. These networks include three functional categories of neurons 1. Afferent neurons carry sensory information into the nervous system. That information comes from specialized sensory neurons that transduce (convert) various kinds of sensory stimuli (e.g., light, heat, pressure) into action potentials. 2. Efferent neurons carry commands to physiological and behavioral effectors such as muscles and glands. 3. Interneurons integrate and store information and communicate between afferent and efferent neurons.
Animals that are more complex and actively move about in search for food and mates need to process and integrate larger amounts of information. Even earthworms fit this description, and their increased need for information processing is met by higher numbers of neurons organized into clusters called ganglia. Ganglia serving different functions may be distributed around the body, as in earthworms or squid In animals that are bilaterally symmetrical, ganglia frequently come in pairs, one on each side of the body. Also, as animals increase in complexity, some ganglia may become enlarged or fused together at the anterior end, forming a larger, centralized integrative center, or brain.
In vertebrates, most cells of the nervous system are found in the brain and the spinal cord, the sites of most information processing, storage, and retrieval The brain and spinal cord are called the central nervous system (CNS). Information is transmitted from sensory cells to the CNS and from the CNS to effectors via neurons that extend or reside outside the brain and the spinal cord neurons and their supporting cells are called the peripheral nervous system (PNS)
CIRCULATORY SYSTEM A circulatory system consists of a muscular pump (the heart), a fluid (blood), and a series of conduits (blood vessels) through which the fluid can be pumped around the body. Heart, blood, and vessels are also known collectively as a cardiovascular system Single-celled organisms serve all of their needs through direct exchanges with the environment The cells of large, mobile animals are supported by the extracellular fluid. All nutrients oxygen, fuel, essential molecules come from that fluid, and the waste products of cell metabolism go into it. Circulatory systems have muscular chambers, or hearts, that move the extracellular fluid around the body. In open circulatory systems, extracellular fluid is the same as the fluid in the circulatory system and is called hemolymph
Open circulatory systems are found in arthropods, mollusks, and some other invertebrate groups. In these systems, a muscular pump, or heart, helps move the hemolymph through vessels leading to different regions of the body In closed circulatory systems, a system of vessels keeps circulating blood separate from the interstitial fluid. Blood is pumped through this vascular system by one or more muscular hearts, and some components of the blood never leave the vessels
Closed circulatory systems have several advantages over open systems: 1. Fluid can flow more rapidly through vessels than through intercellular spaces and can therefore transport nutrients and wastes to and from tissues more rapidly. 2. By changing the diameter (hence resistance) of specific vessels, closed systems can control the flow of blood to selective tissues and organs to match their needs. 3. Specialized cells and large molecules that aid in transporting hormones and nutrients can be kept in the vessels but can drop their cargo in the tissues where it is needed.
Biomechanics has been defined as the study of the movement of living things using the science of mechanics Mechanics is a branch of physics that is concerned with the description of motion and how forces create motion. Forces acting on living things can create motion, be a healthy stimulus for growth and development, or overload tissues, causing injury. Biomechanics provides conceptual and mathematical tools that are necessary for understanding how living things move and how kinesiologyprofessionals might improve movement or make movement safer.
Kinesiology is the scholarly study of human movement Biomechanics is one of the many academic subdisciplines of kinesiology. Biomechanics in kinesiology involves the precise description of human movement and the study of the causes of human movement. By the time children are one, they are skilled walkers with little instruction from parents aside from emotional encouragement.
why and how the human body moves. Why are scholars from so many different academic backgrounds interested in animal movement? The applications of biomechanics to human movement can be classified into two main areas: the improvement of performance and the reduction or treatment of injury. Human movement performance can be enhanced many ways. Effective movement involves anatomical factors, neuromuscular skills, physiological capacities, and psychological/ cognitive abilities.
Movement safety, or injury prevention/ treatment, is another primary area where biomechanics can be applied Biomechanical studies help prevent injuries by providing information on the mechanical properties of tissues, mechanical loadings during movement, and preventative or rehabilitative therapies. The biomechanical study of auto accidents has resulted in measures of the severity of head injuries, which has been applied in biomechanical testing, and in design of many kinds of helmets to prevent head injury After amputation, prosthetics or artificial limbs can be designed to match the mechanical properties of the missing limb
Orthotics are support objects/braces that correct deformities or joint positioning, while assistive devices are large tools to help patient function like canes or walkers. Qualitative analysis of gait (walking) also helps the therapist decide whether sufficient muscular strength and control have been regained in order to permit safe or cosmetically normal walking
How the movement is analyzed falls on a continuum between a qualitative analysis and a quantitative analysis Quantitative analysis involves the measurement of biomechanical variables and usually requires a computer to do the voluminous numerical calculations performed. Even short movements will have thousands of samples of data to be collected, scaled, and numerically processed Qualitative analysis has been defined as the systematic observation and introspective judgment of the quality of human movement for the purpose of providing the most appropriate intervention to improve performance
Rigid-body mechanics, the object being analyzed is assumed to be rigid and the deformations in its shape so small they can be ignored. never happens in any material, this assumption is quite reasonable for most biomechanical studies of the major segments of the body
Mechanics is the branch of physics that studies the motion of objects and the forces that cause that motion. The science of mechanics is divided into many areas, but the three main areas most relevant to biomechanics are: rigid-body deformable-body fluids
Deformable-body mechanics studies how forces are distributed within a material, and can be focused at many levels (cellular to tissues/organs/ system) to examine how forces stimulate growth or cause damage. Fluid mechanics is concerned with the forces in fluids (liquids and gasses). A biomechanist would use fluid mechanics to study heart valves, swimming, or adapting sports quipment to minimize air resistance.
Rigid-body mechanics is divided into statics and dynamics Statics is the study of objects at rest or in uniform (constant) motion. Dynamics is the study of objects being accelerated by the actions of forces. Most importantly, dynamics is divided into two branches: kinematics and kinetics. Kinematics is motion description. In kinematics the motions of objects are usually measured in linear (meters, feet, etc.) or angular (radians, degrees, etc.) terms. Examples of the kinematics of running could be the speed of the athlete, the length of the stride, or the angular velocity of hip extension. Kinetics is concerned with determining the causes of motion. Examples of kinetic variables in running are the forces between the feet and the ground or the forces of air resistance.