The Need to Communicate I: How Cells talk to each other Flashcards
What are chemical signals?
Chemical signals are proteins or other molecules produced by a sending cell, are often secreted from the cell and released into the extracellular space.
How do cells detect signals?
In order to detect a signal (that is, to be a target cell), a neighbouring cell must have the right receptor for that signal. When a signalling molecule binds to its receptor, it alters the shape or activity of the receptor, triggering a change inside of the cell.
What are signalling molecules called?
Signalling molecules are often called ligands, a general term for molecules that specifically bind to other molecules (such as receptors).
What happens to the message carried by the ligand?
The message carried by a ligand is often relayed through a chain of chemical messengers inside the cell. Ultimately, it leads to a change in the cell, such as alteration in the activity of a gene or even the induction of a whole process, such as cell division.
Example of complex cell communication
The hypothalamus (which is a gland in the brain) activates the sympathetic nervous system and the adrenal-cortical system by releasing CRF.
Types of cell signalling
Synaptic or neural signalling
Endocrine or hormone signalling
Synaptic Signalling
In which nerve cells transmits signals. This process is named for the synapse, the junction between two nerve cells where signal transmission occurs.
When the sending neuron fires, an electrical impulse moves rapidly through the cell, travelling down a long, fibre-like extension called an axon. When the impulse reaches the synapse, it triggers the release of ligands called neurotransmitters, which quickly cross the small gap between the nerve cells. When the neurotransmitters arrive at the receiving cell, they bind to receptors and cause a chemical change inside of the cell (often, opening ion channels and changing the electrical potential across the membrane).
Endocrine signalling
When cells need to transmit signals over long distances, they often use the circulatory system as a distribution network for the messages they send. In long-distance endocrine signalling, signals are produced by specialized cells and released into the bloodstream, which carries them to target cells in distant parts of the body. Signals that are produced in one part of the body and travel through the circulation to reach far-away targets are known as target cells.
Names of structures of neurons
Dendrites
Soma (cell body)
Axon
Myelin Sheath
Nodes of Ranvier
Axon terminals
Terminal Button
Gilial Cells
Dendrites
Dendrites: Branched like structure that are shorter and numerous than axon that receive signals from other neurons (as they contain receptors) to send an electrical signal cross the axon. In sensory neuron, dendrites are extremely long whereas motor neurons have small dendrites.
Soma
The soma is the cell body (the core of the neuron). Its function is to maintain the cell and keep the neurone functioning. It is enclosed by a membrane for protection and allows interaction with its environment. It contains a nucleus which produce genetic information allowing protein synthesis. The proteins are vital for neuron function.
Axon
The axon (the nerve fibre) is a tail-like structure that joins the cell body at a junction called the Axon Hillock. The function of the axon is to carry signals away from cell body to the terminal button in order to transmit electrical signals to the other neurons. Vary in size e.g. 0.1 mm to 3ft. Covered by a fatty substance called myelin to aid transmitting signals quicker (through insulation).
Myelin Sheath
The myelin sheath is a layer of fatty material that covers the axon that insulates nerve cell from another and so prevent impulse from one neuron from interfering with another. Also speeds up transmission as the axons are wrapped in cells known as glial cells (also known as oligodendrocytes and Schwann cells) which form the myelin.
Nodes of ranvier
Myelin sheath contains gaps known as Nodes of Ranvier allowing the electrical signal to jump from node to node.
Axon Terminals
The axon terminals are at end of neuron that are responsible for transmitting signals to other neurons via the synapse (using neurotransmitters from terminal button to dendrites of the post-synaptic neuron). The terminal button also reuptakes the neurotransmitters that weren’t passed to the next neuron.
