Bio Unit 1 Lesson 7

Intercellular Communication

the ways cells send, receive, and respond to information from other cells. Cells cannot function independently of one another. They must coordinate their activities to maintain the body's internal environment and carry out normal physiological processes.

Gap Junctions

specialized structure that forms a communication channel between neighboring cells. These channels allow certain substances to move directly from the inside of one cell into an adjacent cell. provide a direct route between the cells.

What can pass through a gap junction?

The pores of gap junctions are very small, so they allow relatively small substances to pass between neighboring cells.

ions, sugars, amino acids, Other small molecules involved in cellular metabolism and signaling

Connexins

individual protein subunits that form the channel.

Connexons

structures formed from six connexin proteins. A connexon in one cell membrane can align with a connexon in an adjacent cell membrane to form a complete channel between the two cells.

Why gap junctions matter

Gap junctions allow cells to exchange ions and other small molecules without requiring each cell to release a separate chemical messenger into the surrounding environment.

Intercalated discs

specialized structures found between cardiac muscle cells. They contain cell junctions, including gap junctions, that allow electrical signals to spread between neighboring cells.

These structures help coordinate the heart's contractions.

How can intercalated discs be regulated

regulated through phosphorylation and dephosphorylation. These processes can influence the activity of proteins and help regulate gap-junction communication.

Phosphorylation

Adding a phosphate group to a molecule

Dephosphorylation

Removing a phosphate group from a molecule

Membrane nanotubes/ tunnelling nanotubes

thin structures formed from the plasma membrane that connect cells. have a larger pore diameter than gap junctions.

What can membrane nanotubes transfer

Because their pore diameter is larger than that of gap junctions, membrane nanotubes can allow the transfer of larger cellular components, including: nucleic acids, small organelles, other cellular components

Mechanosignal transduction

the conversion of a mechanical stimulus into a cellular response. a physical force acts on a cell and triggers chemical, metabolic, or other physiological changes inside that cell. Instead of a chemical messenger arriving from another cell, the signal begins with a physical stimulus.

Endothelial cells

the cells lining the inside of blood vessels.

Shear stress

a force that acts parallel to a surface as fluid flows along it

Atherosclerosis

the buildup of plaque in artery walls, which can harden and narrow the arteries.

hypertension

High blood pressure can increase mechanical forces acting on blood vessel walls and may contribute to processes associated with vascular damage and atherosclerosis.

Mechanosignal transduction SIMPLE

A physical force acts as a stimulus and produces a cellular response.

Indirect intercellular communication

occurs when cells use chemical messengers to communicate with target cells.A chemical messenger is released by a cell and interacts with a target cell that has the appropriate receptor.The messenger may travel only a short distance or may travel through the bloodstream to reach a distant target.

autocrine communication

a cell releases a chemical messenger that acts back on the same cell that produced it.

Paracrine Signaling

occurs when a cell releases a chemical messenger that acts on a nearby cell.

endocrine signalling

ravels through the bloodstream to affect more distant target cells.

Trophoblast cells

cells involved in the development of the placenta and its interactions with maternal tissues. These cells release signals that help regulate processes associated with pregnancy, including maternal–fetal nutrient exchange.

Neurotransmitter

chemical messenger that transmits a signal between a neuron and another target cell.

indirect communication

Neurotransmitters can communicate: From one neuron to another neuron. From a neuron to another type of target cell.

synapse

a specialized site where a neuron communicates with a target cell.

. Presynaptic neuron

the cell sending the signal. Its axon carries the electrical signal toward the axon terminal, where neurotransmitters are released.

Synaptic cleft

the small, fluid-filled space between the presynaptic cell and the postsynaptic cell. Neurotransmitters cross this gap by diffusion. Although an axon can be very long, the synaptic distance across which the neurotransmitter travels is very short.

Postsynaptic cell

receives the signal.

It has receptors that bind the neurotransmitter and trigger a response.

may be another neuron or another type of target cell.

Apoptosis

programmed cell death, a regulated process through which cells die.

Neurotransmitter shutoff mechanisms

Reuptake and Degradation

Reuptake

A neurotransmitter is taken back up into a cell, helping remove it from the synaptic cleft.

Degradation

A neurotransmitter is broken down, terminating its signaling activity.

Hydrophilic Chemical Messengers

Hydrophilic messengers are water-soluble and generally do not cross the lipid bilayer of a cell membrane easily. (ex. insulin, epinephrine, serotonin)

Hydrophilic messengers

typically stored in secretory cells before being released.

binds to receptors (cell surface)

stored in secretory cells

dissolve in plasma

difficult to cross target-cell membrane

activates intracellular signalling and second messengers

exocytosis

the process by which a cell releases substances when a vesicle fuses with the plasma membrane.

Hydrophobic Chemical Messengers

nteract more readily with lipids and generally do not dissolve well in the watery environment of blood plasma.(ex. steroid hormones, sex hormones- estrogen n testosterone, cortisol)

Hydrophilic messengers

on demand. (limited storage)

need to bind to carrier proteins to travel through blood plasma

easier to cross the target-cell membrane

receptor location inside the cell

can directly influence gene expression through intracellular receptors

Up-regulation

ncreasing the amount of a receptor or increasing its availability.

Down-regulation

decreasing the amount or availability of a receptor.

second messengers

a molecule inside the cell that relays or spreads a signal initiated by a chemical messenger outside the cell.