BIO102H Exam 3

local regulator

A secreted molecule that influences cells near where it is secreted

hormone

in multicellular organisms, one of many types of secreted chemicals that are formed in specialized cells, travel in body fluids, and act on specific target cells in other parts of the body, changing the target cells’ functioning. Hormones are thus important in long-distance signaling.

reception

The binding of a signaling molecule to a receptor protein, activating the receptor by causing it to change shape

transduction

A process in which phages (viruses) carry bacterial DNA from one bacterial cell to another. When these two cells are members of different species, transduction results in horizontal gene transfer

signal transduction pathway

A series of steps linking a mechanical, chemical, or electrical stimulus to a specific cellular response

response

In cellular communication, the change in a specific cellular activity brought about by a transduced signal from outside the cell. In feedback regulation, a physiological activity triggered by a change in a variable

ligand

A molecule that binds specifically to another molecule, usually a larger one

G protein-coupled receptor (GPCR)

A signal receptor protein in the plasma membrane that responds to the binding of a signaling molecule by activating a G protein. Also called a G protein-linked receptor

G potein

A GTP-bonding protein that relays signals from a plasma membrane signal receptor, known as a G protein-coupled receptor, to other signal transduction proteins inside the cell

ligand-gated ion channel

A transmembrane protein containing a pore that opens or closes as it changes shape in response to a signaling molecule (ligand), allowing or blocking the flow of specific ions; also called an ionotropic receptor

protein kinase

An enzyme that transfers phosphate groups from ATP to a protein, thus phosphorylating the protein

phosphorylation cascade

A series of chemical reactions during cell signaling mediated by enzymes (kinases), in which each kinase in turn phosphylates and activates another, ultimately leading to the phosphorylation of many proteins

protein phosphatase

An enzyme that removes phosphate groups from (dephosphorylates) proteins, often functioning to reverse the effect of a protein kinase

second messenger

A small, nonprotein, water-soluble molecule or ion, such as a calcium ion or cyclic AMP, that relays a signal to a cell’s interior in response to a signaling molecule bound by a signal receptor protein

cyclic AMP (cAMP)

cyclic adenosine monophosphate, a ring-shaped molecule made from ATP that is a common intracellular signaling molecule (second messenger) in eukaryotic cells. It is also a regulator of some bacterial operons

endocrine system

The internal system of communication involving hormones, the ductless glands that secrete hormones, and the molecular receptors on or in target cells that respond to hormones; functions in concert with the nervous system to effect internal regulation and maintain homeostasis

nervous system

The fast-acting internal system of communication involving sensory receptors, networks of nerve cells, and connections to muscles and glands that respond to nerve signals; functions in concert with the endocrine system to effect internal regulation and maintain homeostasis

reflex

An automatic reaction to a stimulus, mediated by the spinal cord or lower brain

endocrine glands

A gland that secretes hormones directly into the interstitial fluid, from which they diffuse into the bloodstream

hypothalamus

The ventral part of the vertebrate forebrain; functions in maintaining homeostasis, especially in coordinating the endocrine and nervous system; secretes hormones of the posterior pituitary and releasing factors that regulate the anterior pituitary

negative feedback

A form of regulation in which accumulation of an end product of a process slows the process; in physiology, a primary mechanism of homeostasis, whereby a change in a variable triggers a response that counteracts the initial change

positive feedback

A form of regulation in which an end product of a process speeds up that process; in physiology, a control mechanism in which a change in a variable triggers a response that reinforces or amplifies the change

pancreas

A gland with exocrine and endocrine tissues. The exocrine portion functions in digestion, secreting enzymes and an alkaline solution into the small intestine via a duct; the ductless endocrine portion functions in homeostasis, secreting the hormones insulin and glucagon into the blood

pituitary gland

An endocrine gland at the base of thee hypothalamus; consists of a posterior lobe, which stores and releases two hormones produced by the hypothalamus, and an anterior lobe, which produces and secretes many hormones that regulate diverse body functions

posterior pituitary

An extension of the hypothalamus composed of nervous tissue that secretes oxytocin and antidiuretic hormone made in the hypothalamus; a temporary storage site for these hormones

anterior pituitary

A portion of the pituitary that develops from non-neural tissue; consists of endocrine cells that synthesize and secrete several tropic and nontropic hormones

oxytocin

A hormone produced by the hypothalamus and released from the posterior pituitary. It induces contractions of the uterine muscles during labor and causes the mammary glands to eject milk during nursing

antidiuretic hormone (ADH)

A peptide hormone, also known as vasopressin, that promotes water retention by the kidneys. Produced in the hypothalamus and released from the posterior pituitary, ADH also functions in the brain

epinephrine

A catecholamine that, when secreted as a hormone by the adrenal medulla, mediates “fight-or-flight” responses to short-term stresses; also released by some neurons as a neurotransmitter; also known as adrenaline

regulator

An animal for which mechanisms of homeostasis moderate internal changes in a particular variable in the face of external fluctuation of that variable

conformer

An animal for which an internal condition conforms to (changes in accordance with) changes in an environmental variable

interstitial fluid

The fluid filling the spaces between cells in most animals

homeostasis

The steady-state physiological condition of the body

set point

In homeostasis in animals, a value maintained for a particular variable, such as body temperature or solute concentration

stimulus

In feedback regulation, a fluctuation in a variable that triggers a response

sensor

In homeostasis, a receptor that detects a stimulus

thermoregulation

The maintenance of internal body temperature within a tolerable range

endothermic

Referring to organisms that are warmed by heat generated by their own metabolism. This heat usually maintains a relatively stable body temperature higher than that of the external temperature

ectothermic

Referring to organisms for which external sources provide most of the heat for temperature regulation

countercurrent exchange

The exchange of a substance or heat between 2 fluids flowing in opposite directions. For example, blood in a fish gill flows in the opposite direction of water passing over the gill, maximizing diffusion of oxygen into and carbon dioxide out of the blood

lysozyme

An enzyme that destroys bacterial cell walls; in mammals, found in sweat, tears, and saliva

phagocytosis

A type of endocytosis in which large particulate substances or small organisms are taken up by a cell. It is carried out by some protists and by certain immune cells of animals (in mammals, mainly macrophages, neutrophils, and dendritic cells)

Toll-like receptor (TLR)

A membrane receptor on a phagocytic white blood cell that recognizes fragments of molecules common to a set of pathogens

neutrophil

The most abundant type of white blood cell. Neutrophils are phagocytic and tend to self-destruct as they destroy foreign invaders, limiting their life span to a few days

macrophage

A phagocytic cell present in many tissues that functions in innate immunity by destroying microorganisms and in acquired immunity as an antigen-presenting cell

natural killer cell

A type of white blood cell that can kill tumor cells and virus-infected cells as part of innate immunity

cytokine

Any of a group of small proteins secreted by a number of cell types, including macrophages and helper T cells, that regulate the function of other cells

interferon

A protein that has antiviral or immune regulatory functions. For example, interferons secreted by virus-infected cells help nearby cells resist viral infection

complement system

A group of about 30 blood proteins that may amplify the inflammatory response, enhance phagocytosis, or directly lyse extracellular pathogens

inflammatory response

An innate immune defense triggered by physical injury or infection of tissue involving the release of substances that promote swelling, enhance the infiltration of white blood cells, and aid in tissue repair and destruction of invading pathogens

histamine

A substance released by mast cells that causes blood vessels to dilate and become more permeable in inflammatory and allergic responses

lymphocyte

A type of white blood cell that mediates immune responses. The two main classes are B cells and T cells

thymus

A small organ in the thoracic cavity of vertebrates where maturation of T cells is completed

T cells

The class of lymphocytes that mature in the thymus; they include both effector cells for the cell-mediated immune response and helper cells required for both branches of adaptive immunity

B cells

The lymphocytes that complete their development in the bone marrow and become effector cells for the humoral immune response

antigen

A substance that elicits an immune response by binding to receptors of B cells, antibodies, or T cells

antigen receptor

The general term for a surface protein, located on B cells and T cells, that binds to antigens, initiating adaptive immune responses. The antigens on B cells are called B cell receptors, and the antigen receptors on T cells are called T cell receptors

epitope

A small, accessible region of an antigen to which an antigen receptor or antibody binds; also called an antigenic determinant

heavy chain

One of the 2 types of polypeptide chains that make up an antibody molecule and B cell receptor; consists of a variable region, which contributes to the antigen-binding site, and a constant region

light chain

One of two types of polypeptide chains that make up an antibody molecule and B cell receptor; consists of a variable region, which contributes to the antigen-binding site, and a constant region

antibody

A protein secreted by plasma cells (differentiated B cells) that binds to a particular antigen

major histocompatibility complex molecule (MHC)

A host protein that functions in antigen presentation. Foreign MHC molecules on transplanted tissue can trigger T cell responses that may lead to rejection of the transplant

antigen presentation

The process by which an MHC molecule binds to a fragment of an intracellular protein antigen and carries it to the cell surface, where it is displayed and can be recognized by a T cell

effector cell

A lymphocyte that has undergone clonal selection and is capable of mediating an adaptive immune response

plasma cell

The antibody-secreting effector cell of humoral immunity. Plasma cells arise from antigen-stimulated B cells

memory cell

One of a clone of long-lived lymphocytes, formed during the primary immune response, that remains in a lymphoid organ until activated by exposure to the same antigen that triggered its formation. Activated memory cells mount the secondary immune response

clonal selection

The process by which an antigen selectively binds to and activates only those lymphocytes bearing receptors specific for the antigen. The selected lymphocytes proliferate and differentiate into a clone of effector cells and a clone of memory cells specific for the stimulating antigen

primary immune response

The initial adaptive immune response to an antigen, which appears after a lag of about 10-17 days

secondary immune response

The adaptive immune response elicited on second or subsequent exposures to a particular antigen. The secondary immune response is more rapid, of greater magnitude, and of longer duration that the primary immune response

humoral immune response

The branch of adaptive immunity that involves the activation of B cells and that leads to the production of antibodies, which defend against bacteria and viruses in body fluids

cell-mediated immune response

The branch of adaptive immunity that involves the activation of cytotoxic T cells, which defend against infected cells

helper T cell

A type of T cell that, when activated, secretes cytokines that promote the response of B cells (humoral response) and cytotoxic T cells (cell-mediated response) to antigens

antigen-presenting cell

A cell that upon ingesting pathogens or internalizing pathogen proteins generates peptide fragments that are bound by class II MHC molecules and subsequently displayed on the cell surface to T cells. Macrophages, dendritic cells, and B cells are the primary antigen-presenting cells

cytotoxic T cells

A type of lymphocyte that, when activated, kills infected cells as well as certain cancer cells and transplanted cells

immunization

The process of generating a state of immunity by artificial means. In active immunization, also called vaccination, an inactive or weakened form of a pathogen is administered, inducing B and T cell responses and immunological memory. In passive immunization, antibodies specific for a particular pathogen are administered, conferring immediate but temporary protection

monoclonal antibodies

Any of a preparation of antibodies that have been produced by a single clone of cultured cells and thus are all specific for the same epitope

allergen

An antigen that triggers an exaggerated immune response

autoimmune disease

An immunological disease in which the immune system turns against self

human immunodeficiency virus (HIV)

The pathogen that causes AIDS (acquired immune deficiency syndrome)

cell body

The part of a neuron that houses the nucleus and most other organelles

dendrite

One of usually numerous, short, highly branched extensions of a neuron that receive signals from other neurons

axon

A typically long extension, or process, of a neuron that carries nerve impulses away from the cell body toward target cells

synapse

The junction where a neuron communicates with another cell across a narrow gap via a neurotransmitter or an electrical coupling

neurotransmitter

A molecule that is released from the synaptic terminal of a neuron at a chemical synapse, diffuses across the synaptic cleft, and binds to the postsynaptic cell, triggering a response

glia

non-neuronal cells of the nervous system that support, regulate, and nourish neurons; they also insulate neuron axons and remove pathogens and dead cells

sensory neuron

A nerve cell that receives information from the internal or external environment and transmits signals to the central nervous system

interneuron

An association neuron; a nerve cell within the central nervous system that forms synapses with sensory and/or motor neurons and integrates sensory input and motor output

motor neuron

A nerve cell that transmits signals from the brain or spinal cord to muscles or glands

central nervous system (CNS)

The portion of the nervous system where signal integration occurs; in vertebrate animals, the brain and spinal cord

peripheral nervous system (PNS)

The sensory and motor neurons that connect to the central nervous system

nerve

A fiber composed primarily of the bundled axons of neurons

membrane potential

The difference in electrical charge (voltage) across a cell’s plasma membrane due to the differential distribution of ions. Membrane potential affects the activity of excitable cells and the transmembrane movement of all charged substances

resting potential

The membrane potential characteristic of a nonconducting excitable cell, with the inside of the cell more negative than the outside

sodium-potassium pump

A transport protein in the plasma membrane of animal cells that actively transports sodium out of the cell and potassium into the cell

ion channels

A transmembrane protein channel that allows a specific ion to diffuse across the membrane down its concentration or electrochemical gradient

equilibrium potential

(Written E subscript ion) The magnitude of a cell’s membrane voltage at equilibrium, calculated using the Nernst equilibrium

gated ion channel

A gated channel for a specific ion. The opening or closing of such channels may alter a cell’s membrane potential

voltage-gated ion channel

A specialized ion channel that opens or closes in response to changes in membrane potential

hyperpolarization

A change in a cell’s membrane potential such that the inside of the membrane becomes more negative relative to the outside. Hyperpolarization reduces the chance that a neuron will transmit a nerve impulse

depolarization

A change in a cell’s membrane potential such that the inside of the membrane is made less negative relative to the outside. For example, a neuron membrane is depolarized if a stimulus decreases its voltage from the resting potential of negative 70 mV in the direction of zero voltage