Cell communication

Direct contact

Direct contact

communication through cell junctions; signaling substances and other material dissolved in the cytoplasm can pass freely between adjacent cells; animal cells: gap junction; plant cells: plasmodesmata

Antigen presenting cells

communicate to T cells through direct contact

Local Regulators

a secreting cell will release chemical messages(local regulators/ligands) that travel a short distance through the extracellular fluid; ex: paracrine(local) signaling. synaptic signaling

Paracrine signaling

secretory cells release local regulators(ie growth factors) via exocytosis to an adjacent cell

Synaptic signaling

occurs in animal nervous systems; neurons secrete neurotransmitters; diffuse across the synaptic cleft which is the space between the nerve cell and target cell

Long distance signaling

animals and plants use hormones for this; plants release hormones that travel in the plant vascular tissue or through the air to reach target tissues; animals use the endocrine signaling; ex: insulin

Reception

ligand binds to receptor; the detection and receiving of a ligand by a receptor in the target cell

Transduction

signal is converted; the conversion of an extracellular signal to an intercellular signal that will bring about a cellular response; signal is amplified

Response

a cell process is altered; the final molecule in the signaling pathway converts the signal to a response that will alter a cellular process; ex: protein that can alter membrane permeability (cytoplasmic response), enzyme that will change a metabolic process (cytoplasmic response), protein that turns genes on or off (nuclear response)

receptor

macromolecule that binds to a signal molecule(ligand)

plasma membrane receptors

most common type of receptor involved in signal pathways, binds to ligands that are polar, water-soluble and are large; ex: g protein coupled receptors(GPCRs), Ligand-gated ion channels

intercellular receptors

found in the cytoplasm or nucleus of target cell; binds to ligands that can pass through the plasma membrane; ie hydrophobic molecules; steroid and thyroid hormones, gasses like nitric oxide

signal transduction pathway

influence how a cell responds to its environment; they can result in changes in gene expression and cell function; can alter phenotypes or result in cell death

second messengers

small, non-protein molecules and ions help relay the message and amplify the response; cyclic AMP(cAMP) is a common ___

G protein coupled receptors

largest category of cell surface receptors; important in animal sensory systems ; binds to a G protein that can bind to GTP, which is an energy molecule similar to ATP

ion channels

located in the plasma membrane; important in the nervous system; receptors that act as a “gate” for ions; when a ligand binds to the receptor, the gate opens or closes allowing the diffusion of specific ions; initiates a series of events that lead to a cellular response.

set points

values for various physiological conditions that the body tries to maintain; has a normal range for which it can fluctuate; ex: body temperature; set point: 98.6 f, normal range: 97 f to 99 f

homeostasis

the state of relatively stable internal conditions; organisms detect and respond to a stimulus; think: balance; the body maintains this through feedback loop

stimulus

a variable that will cause a response

receptor/sensor

sensory organs that detect a stimulus. this information is sent to the control center (brain)

effector

muscle or gland that will respond

response

changes (decreases or increases) the effect of the stimulus

negative feedback loop

the most common type of feedback mechanism; this type of feedback reduces the effect of the stimulus; ex: sweat, blood sugar, breathing rate

positive feedback loop

this type of feedback increases the effect of a stimulus; ex: child birth, blood clotting, fruit ripening