Cell Signalling

Question 1

Why do cells need signalling?

Answer 1

1. To process info
2. For self - preservation
3. For voluntary movement
4. For homeostasis - inc involuntary processes such as CA2+ levels for blog glucose

Question 2

What is an example of self-preservation?

Answer 2

Spinal reflex arc

Question 3

What are the two main systems that provide communication between cells?

Answer 3

1. Nerve fibres of the central & peripheral nervous system

2. Blood vessels of the cardiovascular system.

Question 4

What is the difference between the 2 main systems of cell communication?

Answer 4

Nerve fibres .. = rapid, instantaneous
vs.
BV = slower but more versatile regulation

Question 5

What is Endocrine signalling?

Answer 5

hormone travels within blood vessels to act on a distant target cell

Question 6

What are examples of endocrine signalling?

Answer 6

1. Glucagon - produced in the pancreas but it acts on the liver
2. Insulin is produced in the pancreas but it acts on the liver, muscle cells and adipose tissue
3. Adrenaline - produced in adrenal glands but acts on trachea (fight or flight)

Question 7

Describe a physiological response relating to endocrine signalling.

Answer 7

• 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.

Question 8

What is Paracrine signalling?

Answer 8

hormone acts on the adjacent cell.

Question 9

What are examples of paracrine signalling?

Answer 9

1. Insulin produced in Beta cells acting on alpha cells
2. Osteoclast activating factors produced by adjacent osteoblasts - BONE FORMATION
3. Nitric oxide produced by endothelial cells in blood vessels

Question 10

What does NItric oxide in bv do?

Answer 10

Causes vasodilation.

e.g. when someone is in septic shock.

Question 11

Describe a physiological response relating to paracrine signalling.

Answer 11

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

Question 12

What is signalling via membrane attached proteins?

Answer 12

when membrane proteins from two different cells interact

Question 13

What is an example of communicating via membrane attached proteins using T cells?

Answer 13

T cell receptor interacting with MHC class II molecule on surface of APC.

Question 14

What does HIV GP120 glycoprotein interact with and what type of cell signalling is this?

Answer 14

• with CD4 receptor

- signalling via membrane attached proteins

Question 15

What is another example of membrane attached protein signalling?

Answer 15

Bacterial ell wall components binding to toll-like receptors on haemopoietic cells

Question 16

What is Autocrine signalling?

Answer 16

hormone acts on the same cell that produces it

Question 17

How does Interleukin-2 carry out autocrine signalling?

Answer 17

• 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.

Question 18

IL-2 binding to a receptor on the adjacent cell is what kind on communication?

Answer 18

paracrine

Question 19

What kind of feedback can autocrine signalling have?

Answer 19

negative feedback

Question 20

What are other examples of autocrine siganlling?

Answer 20

• 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)

Question 21

During Neurotransmission, when is cell signalling used?

Answer 21

Propagation of action potential by depolarisation and repolarisation

NT released from vesicles

Activation of post synaptic receptors

Question 22

what are receptors?

Answer 22

usually proteins that bind ligands and have an effect within a cell that arises due to a second messenger

Question 23

How do ionotropic/Ligand-gated ion channel receptors transmit messages?

Answer 23

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.

Question 24

Example of a Ionotropic receptor, its ligand and effect in the skeletal muscle?

Answer 24

Receptor = Nicotinic Acetylcholine
Ligand = Acetylcholine(ACh)
Effect = muscle contraction

Question 25

What ionortopic receptor and ligand causes the inhibition of neuronal activity?

Answer 25

GABA(A) receptor and GABA ligand

Question 26

what ligand is NMDA the receptor for and what does it do?

Answer 26

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

Question 27

What is a membrane-spanning receptor?

Answer 27

Has external and internal components e.g. ligand-binding domain on outside and enzyme on the inside

Question 28

What is an Enzyme linked receptor?

Answer 28

Membrane -spanning receptor

has an enzyme, usually tyrosine kinase, on the inside and ligand-binding domain on the outside

Question 29

What is required to activate the enzyme in an enzyme-linked receptor?

Answer 29

Receptor clustering

Question 30

How does receptor clustering occur?

Answer 30

The binding of a ligand results in receptor clustering

Question 31

What is the process of communication using an enzyme-linked receptor?

Answer 31

1. Ligand binds-> receptor clustering

2. Recep clustering