* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Human Anatomy and Physiology
Survey
Document related concepts
Homeostasis wikipedia , lookup
Embryonic stem cell wikipedia , lookup
Biochemical cascade wikipedia , lookup
Hematopoietic stem cell wikipedia , lookup
Artificial cell wikipedia , lookup
Cellular differentiation wikipedia , lookup
Cell culture wikipedia , lookup
Microbial cooperation wikipedia , lookup
Human embryogenesis wikipedia , lookup
State switching wikipedia , lookup
Neuronal lineage marker wikipedia , lookup
Adoptive cell transfer wikipedia , lookup
Cell theory wikipedia , lookup
Transcript
Human Anatomy and Physiology Mei-Lan Ko 2011 Sep 20th 1 Ch 1: A framework for human physiology 2 The scope for human physiology Physiology: how living organisms work Interest in function & integration Molecular biology Genome Disease: pathophysiology Disruption of homeostasis 3 Mechanism and causality Mechanist view: Physical and chemical laws Integration Causal chains: long, multiple Vitalism: Vital force 4 A Society of cells Cell: the simplest structural unit A complex multicelluar organism can be divided and still retain the functions characteristic of life Cellular functions Specialized cells: 200 kinds Muscle cell: to generate the mechanical forces Nerve cell: to initiate and conduct electric signals Epithelial cell: for the selective secretion and absorption of ions and organic molecules Connective-tissue cell: for connecting, anchorig, supporting 5 Tissue An aggregate of a single type of specialized cell Muscle tissue, nerve tissue, epithelial tissue, connective tissue Extracelluar fluid (matrix) consisting: fibers and other protein Functions: 1): a scaffold for cellular attachments (packing) 2): transmit to the cells information (adhesion/recognition) Organ: composed of the 4 tissues Organ system: 10 organ systems In vitro, in vivo 6 7 8 9 Muscle Cells and Tissues 3 types of muscle cells: 10 Cardiac Smooth Skeletal involuntary voluntary Muscle cells with be covered in depth in Ch 9 Neurons and Nervous Tissue A Neuron nervous tissue: 11 A collection of neurons brain or spinal cord a nerve a cell of the nervous system is specialized to initiate, integrate and conduct electrical signals to other cells Axons from many neurons are packaged together along with connective tissue to form Neurons, nervous tissue, and the nervous system will be covered in Chapter 6. Epithelial cells and epithelial tissue Epithelial cells are specialized for the selective secretion and absorption of ions and organic molecules, and for protection. cuboidal (cube-shaped), columnar (elongated), squamous (flattened) and ciliated. Epithelial tissue form from any type of epithelial cell. Epithelia may be arranged 12 in single-cell thick tissue, called a simple epithelium, or a thicker tissue consisting of numerous layers of cells, called a stratified epithelium. The type of epithelium that forms in a given region of the body reflects the function of that particular epithelium. For example, inner surface of the main airway, the trachea, consists of ciliated epithelial cells (see Chapter 13). Epithelial cells and epithelial tissue 13 Epithelia are located at the surfaces that cover the body or individual organs the inner surfaces of the tubular and hollow structures within the body. Epithelial cells rest on an extracellular protein layer called the basement membrane. The side of the cell anchored to the basement membrane is called the basolateral side; the opposite side, which typically faces the interior, is called the apical side. the two sides of all the epithelial cells in the tissue may perform different physiological functions. In addition, the cells are held together along their lateral surfaces by extracellular barriers called tight junctions boundaries between body compartments and to function as selective barriers regulating the exchange of molecules. Epithelial Cells Epithelial tissue (= epithelium) Forms barrier separates body from external environment lines hollow organs forms glands Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 2.1c Figure 1-2 15 Connective tissue cells and connective tissue Connective tissue cells connect, anchor, and support the structures of the body Types of connective tissues include: 16 Loose Connective Dense Connective Blood Cartilage Adipose What surrounds the cells? the extracellular fluid and extracellular matrix (ECM) ECM consists of a mixture of proteins, polysaccharides, and in some cases, minerals The matrix serves two general functions: The proteins of the extracellular matrix consist of fibers 17 (1) It provides a scaffold for cellular attachments (2) it transmits information, in the form of chemical messengers, to the cells to help regulate their activity, migration, growth, and differentiation. ropelike collagen fibers rubberband-like elastin fibers a mixture of nonfibrous proteins that contain carbohydrate. 18 Organs and Organ Systems Organs are composed of multiple tissue types (example: blood vessels have layers of smooth muscle cells, endothelial cells and fibroblasts). Organ systems contain multiple organs that work together (example: the urinary system has the kidney, ureters, urethra, bladder). 19 Organ systems Circulatory Respiratory Digestive Urinary Musculoskeletal Immune Nervous Endocrine Reproductive integumentary 20 21 Internal environment Equal to the extracellular fluid Homeostasis Internal environment: relative constancy changes: small within narrow limits Activities of cells Minimal requirements for maintaining individual integrity and life Perform specialized activities: maintaining the stable internal environment 22 23 Cell: intracelluar fluid (2/3) Extracellular fluid (1/3) Surrounding cells: interstitial fluid: 80% X(1/3) Inside blood vessels: plasma: 20% X(1/3) 24 25 Compartmentalization Membrane: intra & extracellular fluid Cellular walls of Capillaries: interstitial fluid & plasma 26 Figure 1-3 ICF ISF plasma organs internal environment 27 external environment Exchange and communication are key concepts for understanding physiological homeostasis. Homeostasis: a defining Features of physiology Defined: a state of reasonably stable balance between the physiological variables Dynamic process Time-averaged meannormal baseline value Eg: hormone in blood 24-hour urine sample 28 Blood glucose levels increase after eating Levels return to their set point via homeostasis dynamic constancy. Figure 1-4 29 Figure 1-5 (e.g., decreased room temperature causes increased heat loss from the body, which leads to a decrease in body temperature, etc.) 30 System Controls Feedback loops or systems are a common mechanism to control physiological processes. A positive feedback system (also called a feed forward) enhances the production of the product. A negative feedback system shuts the system off once the set point has been reached. 31 Figure 1-6 Negative Feedback “Active product” controls the sequence of chemical reactions 32 by inhibiting the sequence’s rate-limiting enzyme, “Enzyme A.” General characteristic of homeostatic control systems Steady state Equilibrium Variable: no change Input of energy (+) Variable: no change Input of energy (-) Feedback Negative : cortisol Positive: sodium channel 33 Resetting of set points Eg: fever, decrease in iron during infecton A rhythmical basis every day Multiple systems control a single parameter Feedforward regulation Anticipates changes in a regulated variable to reduces the amount of deviation from the set point.學習的結果 Eg: temperature sensitive nerve cells in the skin 34 A strategy for exploring homeostasis (see Tables 1-2 & 1-3) • Identify the internal environmental variable. example: concentration of glucose in the blood • Establish the “set point” value for that variable. example: 70 to 110 mg glucose/dL of blood • Identify the inputs and outputs affecting the variable. example: diet and energy metabolism 35 36 37 Components of homeostatic control systems Reflexes Basic reflex Learned reflex Local homeostatic responses Stimulus ( ext or internal environment) →alteration of cell activity Occur in the area of stimulus Eg: tissue injury 38 Reflexes A reflex is a specific involuntary The pathway mediating a reflex is known as the reflex arc. stimulus, receptor, afferent (incoming) pathway, integration center, efferent (outgoing) pathway, and effector. The pathway the signal travels between the receptor and the integrating center is known as the afferent pathway. The pathway along which information travels away from the integration center to the effector is known as the efferent pathway An integrating center 39 often receives signals from many receptors, some of which may respond to quite different types of stimuli. the output of an integrating center reflects the net effect of the total afferent input; it represents an integration of numerous bits of information. Nerve system Endocrine gland Nerve fiber Blood borne messenger Muscle gland 40 41 Non-nerve Reflexes Almost all body cells can act as effectors in homeostatic reflexes. two specialized classes of tissues 42 muscle and gland that are the major effectors of biological control systems. Glands: the effector may be a hormone secreted into the blood A hormone is a type of chemical messenger secreted into the blood by cells of the endocrine system (see Table 1–1) Hormones may act on many different cells simultaneously because they circulate throughout the body. Intercellular Chemical Messengers Intercellular communication Hormone blood Hormone secreting cells target cells neurotransmitter Nerve cells effector Neurotransmitter paracrines 43 Chemical Messengers • Chemical messengers participate not only in reflexes, but also in local responses. • Communication signals in three categories • Endocrine: signal reaches often-distant targets after transport in blood. • Paracrine: signal reaches neighboring cells via the ISF. • Autocrine: signal affects the cell that synthesized the signal. 44 Paracrine/autocrine agents Synthesized by cells extracellular fluid Not into the blood stream Local negative effect: often serve to oppose the effects induced locally by the neurotransmitter or hormone 45 46 Points to Remember A neuron, endocrine gland cell, and other cell types may all secrete the same chemical messenger. a particular messenger may function as a neurotransmitter, as a hormone, or as a paracrine/autocrine substance. Example: Norepinephrine is a neurotransmitter in the brain and is also produced as a hormone by cells of the adrenal glands. 47 Other Types of Cell Communication two important types of chemical communication between cells that do not require secretion of a chemical messenger. 48 Gap junctions (physical linkages connecting the cytosol between two cells) allow molecules to move from one cell to an adjacent cell without entering the extracellular fluid. Juxtacrine signaling is the chemical messenger not actually being released from the cell producing it, but rather is located in the plasma membrane of that cell. When the cell encounters another cell type capable of responding to the message, the two cells link up via the membrane-bound messenger. Processes related to homeostasis Adaptation Favor survival in specific environments Change in genetic endowment Acclimatization The improved functioning of an already existing homeostatic system No change in genetic endowment Increase capacity to withstand change ↑cell: number, size, sensitivity Reversible( except developmental acclimatization) 49 Biological rhythms Circadian rhythm Activating homeostatic mechanisms at times before challenge occur Most: internally driven Environmental factors provide the timing cues for entrainment Free running rhythm: no environment factors Jet lag: to reset the internal clock phase-shift rhythms Hypothalamus: pacemaker of body rhythms To pineal gland melatonin 50 asleep Figure 1-10 A full analysis of the hormone cortisol requires not only knowledge of the signals that cause its synthesis and secretion but also consideration of biological rhythms. 51 asleep What have biological rhythms to do with homeostasis? They add an anticipatory component to homeostatic control systems and in effect are a feed-forward system operating without detectors. The negative-feedback homeostatic responses are corrective responses. They are initiated after the steady state of the individual has been perturbed. Biological rhythms enable homeostatic mechanisms to be utilized immediately and automatically by activating them at times when a challenge is likely to occur but before it actually does occur. 52 Balance in the Homeostasis of Chemical Substances in the Body Many homeostatic systems regulate the balance between addition and removal of a chemical substance from the body. Two important generalizations concerning the balance concept: 53 (1) During any period of time, total-body balance depends upon the relative rates of net gain and net loss to the body; (2) the pool concentration depends not only upon the total amount of the substance in the body, but also upon exchanges of the substance within the body. Figure 1-11 54 Some of the potential inputs and outputs that can affect the “pool” of a material (like glucose) that is a dynamically regulated physiological variable. Figure 1-12 Sodium homeostasis: Consuming greater amounts of dietary sodium initiates a set of dynamic responses that include greater excretion of sodium in the urine. Though not shown here, the amount excreted would likely exceed the amount ingested until the “set point” is restored. 55