Cell Signalling Flashcards
Why do cells need signalling?
- To process info
- For self - preservation
- For voluntary movement
- For homeostasis - inc involuntary processes such as CA2+ levels for blog glucose
What is an example of self-preservation?
Spinal reflex arc
What are the two main systems that provide communication between cells?
- Nerve fibres of the central & peripheral nervous system
2. Blood vessels of the cardiovascular system.
What is the difference between the 2 main systems of cell communication?
Nerve fibres .. = rapid, instantaneous
vs.
BV = slower but more versatile regulation
What is Endocrine signalling?
hormone travels within blood vessels to act on a distant target cell
What are examples of endocrine signalling?
- Glucagon - produced in the pancreas but it acts on the liver
- Insulin is produced in the pancreas but it acts on the liver, muscle cells and adipose tissue
- Adrenaline - produced in adrenal glands but acts on trachea (fight or flight)
Describe a physiological response relating to endocrine signalling.
- Physiological response to hypoglycaemia :
1. alpha cells of islets of Langerhans secret GLUCAGON
2. GLUCAGON travels out of pancreas in BLOOD VESSELS
3.GLUCAGON stimulates glycoGENOlysis and glucoNEOgenesis in the liver.
THIS LEADS TO AN INCREASE IN BLOOD GLUCOSE.
What is Paracrine signalling?
hormone acts on the adjacent cell.
What are examples of paracrine signalling?
- Insulin produced in Beta cells acting on alpha cells
- Osteoclast activating factors produced by adjacent osteoblasts - BONE FORMATION
- Nitric oxide produced by endothelial cells in blood vessels
What does NItric oxide in bv do?
Causes vasodilation.
e.g. when someone is in septic shock.
Describe a physiological response relating to paracrine signalling.
Hyperglycaemia:
- glucose uptake
- reduced glycogenolysis and gluconeogenesis:
increased bg levels lead to insulin secretion via beta cells in islets of Langerhans
ins inhibits glucagon secretion from alpha cells
What is signalling via membrane attached proteins?
when membrane proteins from two different cells interact
What is an example of communicating via membrane attached proteins using T cells?
T cell receptor interacting with MHC class II molecule on surface of APC.
What does HIV GP120 glycoprotein interact with and what type of cell signalling is this?
- with CD4 receptor
- signalling via membrane attached proteins
What is another example of membrane attached protein signalling?
Bacterial ell wall components binding to toll-like receptors on haemopoietic cells
What is Autocrine signalling?
hormone acts on the same cell that produces it
How does Interleukin-2 carry out autocrine signalling?
- acts on T lymphocytes:
activated T cell expresses IL-2 receptor on surface
activated T lymphocyte also secretes IL-2
-binds to IL-2 receptor on the SAME cell and adjacent activated T cell.
IL-2 binding to a receptor on the adjacent cell is what kind on communication?
paracrine
What kind of feedback can autocrine signalling have?
negative feedback
What are other examples of autocrine siganlling?
- Acetylcholine acting on pre-synaptic M2 receptors =NEGATIVE FEEDBACK
- growth factors such as TGFbeta from tumour cells act on tumour cells to cause mitogenesis (triggering mitosis)
During Neurotransmission, when is cell signalling used?
Propagation of action potential by depolarisation and repolarisation
NT released from vesicles
Activation of post synaptic receptors
what are receptors?
usually proteins that bind ligands and have an effect within a cell that arises due to a second messenger
How do ionotropic/Ligand-gated ion channel receptors transmit messages?
Ligand binds to the receptor protein
Channel protein arrangement/conformation changes to open a pore
Pore allows ion to move in and out of cell epending on their concentration gradients.
Example of a Ionotropic receptor, its ligand and effect in the skeletal muscle?
Receptor = Nicotinic Acetylcholine Ligand = Acetylcholine(ACh) Effect = muscle contraction
What ionortopic receptor and ligand causes the inhibition of neuronal activity?
GABA(A) receptor and GABA ligand
what ligand is NMDA the receptor for and what does it do?
ligand = glutamate
- synaptic plasticity (Synaptic plasticity is the biological process by which specific patterns of synaptic activity result in changes in synaptic strength and is thought to contribute to learning and memory.) and memory formation
What is a membrane-spanning receptor?
Has external and internal components e.g. ligand-binding domain on outside and enzyme on the inside
What is an Enzyme linked receptor?
Membrane -spanning receptor
has an enzyme, usually tyrosine kinase, on the inside and ligand-binding domain on the outside
What is required to activate the enzyme in an enzyme-linked receptor?
Receptor clustering
How does receptor clustering occur?
The binding of a ligand results in receptor clustering
What is the process of communication using an enzyme-linked receptor?
- Ligand binds-> receptor clustering
2. Recep clustering
