Chapter 5: Chemical Messengers Flashcards
Type of muscles that use direct communication through gap junctions
Cardiac & Smooth
Most common type of communication between secretory and target cells
Chemical messenger
Functional class of chemical messengers that are molecules locally produced and released
Cytokines
Functional class of chemical messengers that may act as a hormone, NT, or both
Neurohormones
Component of the Cytokine functional class of chemical messengers that contain growth and clotting factors
Paracrine
specific form of cell-cell communication in which a secretory cell produces a signal to induce changes in nearby/target cells, altering the behavior or differentiation of those cells
Paracrines
type of chemical messenger that transmits signals across a chemical synapse, such as a neuromuscular junction, from one neuron (presynaptic) to another “target” neuron (postsynaptic), muscle cell, or gland cell.
Neurotransmitters (NT)
chemical messengers that are secreted directly into the blood, which carries them to organs and tissues of the body to exert their functions
Hormones
What chemical property allows Testosterone and Prostaglandins to bind to receptors inside the cell?
Lipophilic
molecule that binds to a receptor
ligand
Paracrine ligands move by?
Diffusion
Hormone ligands move by?
Blood transport
How do hydrophilic messengers work?
- Endocrine cell secretes messenger by exocytosis
- Messengers dissolve into the blood vessel quickly
How do hydrophobic messengers operate?
- Endocrine Cell secretes by diffusion
- Binds to carrier proteins in the blood
time for a chemical to decrease concentration in half
messenger half-life
type of messengers that have a relative short life & example
dissolved in plasma
Insulin <10 min
type of messengers that have a relative long half-life & example
bound to plasma protein
Cortisol 1/2 life = 90 min
Process of producing response in target cell
Signal Transduction
Signal Transduction steps? (2)
- Messenger binds to receptor
- Binding results in a response
4 Components of Signal Transduction
- Specificity
- Brief & reversible binding
- Affinity- strength of binding
- Location
- Lipophobic ligands- cell membrane
- Lipophilic ligands- within cell
Strength of a target response depends on (3)
- Concentration of messenger (ligand)
- # of receptors/target cell
- Receptor affinity for messenger
Process by which the receptor number decreases on the target
May result from?
Effect on messenger?
Down-regulation
May result from excess messenger
Sensitivity to messenger decreases & Tolerance to messenger develops
Process by which the receptor number increases on the target cell
May result from?
Effects?
Up-regulation
May result from too little messenger
Sensitivity to messenger increases
chemical which binds to the receptor and mimics the normal response
agonist
chemical which binds to the receptor but does not result in a response; competes w/ the normal ligand and creates an opposite response
antagonist
2 mechanisms of signal transduction
Intracellular-mediated responses
Membrane-bound receptor-mediated responses
Name the 3 types of Membrane-bound receptor-mediated responses
Channel-linked receptor
Enzyme-linked receptor
G protein-linked receptor
Intracellular-mediated responses occur everywhere except?
Thyroid
5 Steps of Intracellular-Mediated Response of Signal Transduction
- Lipophillic messenger diffuses into cell
- Messenger enters nucleus and binds to a nuclear receptor
- Messenger binds to cytoplasmic receptor and enters nucleus
- Becomes a Hormone-receptor complex and attaches to DNA as Hormone Response Element (HRE)
- Produces mRNA
- Exits the nucleus to create ribosomes
- Final products are proteins
2 ways membrane-bound receptors respond to the target?
Movement of Ions
Phosphorylation of enzymes
Type of membrane-bound receptor-mediated response involving fast-ligand gated channels
Channel-Linked Receptors
When calcium enters the cell through an open channel, what occurs when it activates Calmodulin?
It activates a 2nd messenger Ca-Calmodulin –> activates enzymes –> Protein Kinase –> protein-P –> creates a response in the cell such as muscle contraction, altered metabolism/transport
How does an enzyme-linked receptor, such as Insulin, create a response in a cell?
- Messenger binds to an inactive Tyrosine kinase receptor
- Activating the tyrosine kinase receptor
- Addition of ATP to protein-Tyr –> protein-Tyr-P +ADP
- Creates a response in the cell such as alter metabolism/regulate protein synthesis
Type of membrane-bound receptor-mediated protein that involves slow ligand-gated channels
G protein-linked receptors
How does a G protein-linked receptor change electrical properties of a cell?
- Messenger binds to a receptor containing G protein (alpha+GDP,beta,gamma)
- GTP replaces GDP on alpha subunit
- alpha subunit+GTP separate from receptor & bind to slow- ligand-gated channel to allow ions to move in & out of cell
- Produces a change in electrical properties of the cell
What do G protein-linked receptors chemically activate?
Second Messengers
What is another name for a Second Messenger and how does it function?
Intracellular Messenger
1st messenger is triggered –> activates the G protein –> activates amplifier enzyme–> activates 2nd messenger production
How do 2nd Messenger Systems, cAMP, function?
- Messenger binds to a receptor containing G protein (alpha+GDP,beta,gamma)
- GTP replaces GDP on alpha subunit
- alpha subunit+GTP separate from receptor & bind to Adenylate Cyclase
- ATP replaces cAMP to activate PKA
- Protein+ATP replaces Protein+P+ADP
- Produces a response in the cell
What systems are responsible for long-distance communication?
Neural & Endocrine Systems
An endocrine target cell secretes ________ that enters the blood and spans a distance to the target
An endocrine target cell secretes hormone that enters the blood and spans a distance to the target
Type of cell that transmits signals
nerve cells
What is the difference between signal transmission via axons and via synapse?
Axons transmit signals within a neuron
Synapse provides a space for signal transmission between cells
signals of axon?
action potential
