An Introduction To The Human Body

1. An Introduction To The Human Body Biology 1611 Anatomy & Physiology I

2. Anatomy and Physiology Defined Through a study of anatomy and its subdivisions, the body may be examined at different levels of structural organization: Anatomy may be defined as the study of structure and the relationships among structures. Subdivisions of anatomy include surface anatomy, gross anatomy, systemic anatomy, regional anatomy, radiographic anatomy, developmental anatomy, embryology, cytology, and pathological anatomy A study of physiology deals with how body parts function: the structure of a part determines its function. Physiology is the study of how body structures function. Subdivisions of physiology include cell physiology, systems physiology, pathophysiology, exercise physiology, neurophysiology, endocrinology, cardiovascular physiology, immunophysiology, respiratory physiology, renal physiology, and reproductive physiology.

3. Levels of Organization The chemical level includes atoms, the smallest units of matter that participate in chemical reactions, and molecules, two or more atoms joined together. Cells are the basic structural and functional units of an organism. Tissues consist of groups of similarly specialized cells and the substances surrounding them that usually arise from a common ancestor and perform certain special functions. Organs are structures of definite form that are composed of two or more different tissues and have specific functions. Systems consist of related organs that have a common function. The human organism is a collection of structurally and functionally integrated systems; any living individual. The systems of the human body are the integumentary, skeletal, muscular, nervous, endocrine, cardiovascular, lymphatic, respiratory, urinary, and reproductive.

4. Palpation Techniques Three noninvasive techniques of palpation, auscultation, and percussion are used to assess certain aspects of body structure and function. In palpation the examiner feels body surfaces with the hands; an example would be pulse and heart rate determination. In auscultation, the examiner listens to body sounds to evaluate the functioning of certain organs, as in listening to the lungs or heart. In percussion, the examiner taps on the body surface with the fingertips and listens to the resulting echo

5. Characteristics of the Living Human Organism All living things have certain characteristics that distinguish them from nonliving things. Among the life processes in humans are metabolism, responsiveness, movement, growth, differentiation, and reproduction. Metabolism is the sum of all chemical processes that occur in the body, including catabolism and anabolism. Responsiveness is the ability to detect and respond to changes in the external or internal environment. Movement includes motion of the whole body, individual organs, single cells, or even organelles inside cells. Growth refers to an increase in size and complexity, due to an increase in the number of cells, size of cells, or both. Differentiation is the change in a cell 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.

6. An autopsy is a postmortem examination of the body and dissection of its internal organs to confirm or determine the cause of death. A necropsy is an autopsy performed on an animal. Homeostasis is a condition of equilibrium in the body�s internal environment produced by the ceaseless interplay of all the body�s regulatory processes. For the body�s cells to survive, the composition of the surrounding fluids must be precisely maintained at all times. Fluid inside body cells is called intracellular fluid. Fluid outside body cells is called extracellular fluid (ECF) and is found in two principal places. ECF filling the narrow spaces between cells of tissues is called interstitial fluid, intercellular fluid, or tissue fluid. ECF in blood vessels is termed plasma. Since ECF is in constant motion throughout the body and also surrounds all body cells, it is often called the body�s internal environment.

7. Control of Homeostasis Homeostatic imbalances occur because of disruptions from the external or internal environments. Homeostasis is regulated by the nervous system and endocrine system, acting together or independently. The nervous system detects changes and sends nerve impulses to counteract the disruption. The endocrine system regulates homeostasis by secreting hormones. Whereas nerve impulses cause rapid changes, hormones usually work more slowly.

8. Feedback Systems�Terms A feedback system is a cycle of events in which information about the status of a condition is continually monitored and fed back (reported) to a central control region. Any disruption that changes a controlled condition is called a stimulus. A feedback system consists of three basic components: A receptor monitors changes in a controlled condition and sends input in the form of nerve impulses or chemical signals to a control center. The control center sets the range of values within which a controlled condition should be maintained, evaluates the input it receives from the receptors, and generates output commands when they are needed. An effector is a body structure that receives output from the control center and produces a response or effect that changes the controlled condition. If a response reverses the original stimulus, the system is a negative feedback system. If a response enhances the original stimulus, the system is a positive feedback system.

9. Negative Feedback Systems A negative feedback system reverses a change in a controlled condition. Homeostasis of Blood Pressure (BP): Negative Feedback. If a stimulus (stress) causes blood pressure (controlled condition) to rise, pressure-sensitive cells (baroreceptors) in certain arteries send impulses (input) to the brain (control center). The brain sends impulses (output) to the heart (effector), causing the heart rate to decrease (response) and return of blood pressure to normal (restoration of homeostasis). The activity of the effector produces a result, a drop in blood pressure, that opposes the stimulus, an increase in blood pressure.

10. Positive Feedback Systems A positive feedback system tends to strengthen or reinforce a change in one of the body�s controlled conditions. Normal childbirth provides a good example of a positive feedback system. When labor begins, the uterus is stretched (stimulus) and stretch-sensitive nerve cells in the cervix of the uterus (receptors) send impulses (input) to the hypothalamus (control center). The hypothalamus causes the release of oxytocin (output) which stimulates the uterus (effector) to contract more forcefully (response). Movement of the baby�s head down the birth canal causes further stretching, the release of more oxytocin, and even more forceful contractions. The cycle is broken with the birth of the baby. The positive feedback system reinforces a change in a controlled condition.

11. Homeostatic Imbalances�Terms Disruption of homeostasis can lead to disease and death. Disorder is a general term for any derangement of abnormality of function. Disease is a more specific term for an illness characterized by a recognizable set of signs and symptoms. A local disease is one that affects one part or a limited region of the body. A systemic disease affects either the entire body or several parts. Symptoms are subjective changes in body functions that are not apparent to an observer; e.g., headache or nausea. Signs are objective changes that a clinician can observe and measure; e.g., fever or rash.

12. Homeostatic Imbalances�Terms Diagnosis is the art of distinguishing one disease from another or determining the nature of a disease; a diagnosis is generally arrived at after the taking of a medical history and the administration of a physical examination.

13. Aging & The Human Body Aging is characterized by a progressive decline in the body�s responses to restore homeostasis. These changes such as crinkled skin, gray hair and loss of bone mass are apparent in all body systems.