Hormonal Signalling and Cell Communication

These flashcards cover the fundamental vocabulary and concepts of cell signaling, including communication types, receptor classes, stages of signaling, and second messenger pathways as presented in the lecture.

Cell signaling

The process by which cells receive, interpret, and respond to extracellular stimuli to maintain homeostasis and perform specialized functions.

Ligand

An extracellular chemical that acts as a signaling molecule by binding to a specific protein on a target cell.

Receptors

Specific proteins on the target cell membrane or within the cell that recognize and bind to ligands.

Autocrine communication

A type of local signaling where the signaling cell and the target cell are the same or of a similar cell type.

Paracrine communication

Chemical signaling that allows cells to locally coordinate activities with neighboring cells over relatively short distances.

Endocrine communication

Long-distance signaling where hormones produced by endocrine glands travel via the blood to act on distant target cells.

Neurotransmitter

A signaling molecule of the paracrine form that carries information from one nerve cell to another nerve cell, muscle, or tissue, such as acetylcholine or dopamine.

Neurohormone

A chemical substance, such as Oxytocin or $ADH$, released by a nerve cell directly into the blood to be transported to distant target cells.

Cytokines

Signaling proteins secreted by the immune system and some non-immune cells into the $ECF$ that help control inflammation.

Hydrophilic signals

Chemical signals that cannot enter the cell and must act through surface receptors.

Hydrophobic signals

Chemical signals that can enter the cell to bind with intracellular receptors on the nucleus to initiate protein synthesis.

Reception

The first stage of cell signaling where a cell detects a signaling molecule binding to a receptor protein.

Transduction

The second stage of cell signaling where the binding of a ligand initiates a pathway of enzymatic steps.

Response

The final stage of cell signaling where a signal triggers a specific cellular activity, such as activating an enzyme or altering gene expression.

Ion-channel linked receptors

Transmembrane proteins, such as $nAchR$ or $GABA_A$, that can be opened or closed by changes in membrane potential or ligand binding.

Second messengers

Intracellular molecules like $cAMP$, $IP_3$, $DAG$, and $Ca^{2+}$ that participate in signal transduction pathways after a ligand binds to a receptor.

$cAMP$ pathway

A G-protein linked system where Adenylyl Cyclase catalyzes the conversion of $ATP$ to cyclic $AMP$ to activate protein kinase A.

Phosphodiesterase

An enzyme that inhibits the $cAMP$ pathway.

Phospholipase C (PLC)

An effector protein activated by G-proteins ($Gq$) that cleaves $PIP_2$ into the second messengers $IP_3$ and $DAG$.

Inositol triphosphate (IP3)

A second messenger that diffuses into the cytoplasm and binds to ligand-gated channels in the $ER$ to release Ca^{2+.

Diacylglycerol (DAG)

A second messenger that remains in the plasma membrane and activates Protein kinase C ($PKC$).

Calmodulin

An intracellular protein that becomes active when bound to $Ca^{2+}$, subsequently activating other effector proteins.

Tyrosine kinase receptor (TKR)

An enzyme-linked receptor that transfers a phosphate group from $ATP$ to tyrosine residues on specific intracellular proteins.

Signal amplification

A process where a single extracellular chemical messenger leads to a cascading increase in the number of activated molecules within the cell.