10 Signalling Between Cells I Flashcards
Q: Why do cells need to communicate? (4) Describe them.
A: - Process Information: Sensory stimuli - e.g. light (visual auditory signals we get are sent to brain to be processed= vital process)
- Self Preservation (natural instinct for survival): identify and take appropriate actions; Spinal reflexes, Sympathetic nervous system
- Voluntary Movement: getting from A to B, completing daily tasks (brain commuting with skeletal muscle)
- Homeostasis: Thermoregulation, Glucose homeostasis (process going on all the time- maintaining body’s homeostatic regulation)
Q: Give an example of spinal reflexes.
A: hold hand over flame and automatically retract hand -> senses on hand contacting skeletal muscle = arm movement
Q: Describe self preservation in terms of the sympathetic nervous system.
A: fight or flight response in moments of danger
sensory information communicating with brain
Q: What’s the body’s physiological response to hypoglycaemia? What’s the process for this? What’s this form of signalling an example of?
A: (eg. haven’t had breakfast yet)
- glycogen breakdown in liver (glycogenolysis)
- gluconeogenesis (using non carbohydrate sources)
- Glucagon is secreted by the alpha cells in the islets of Langerhans in pancreas
- glucagon travels out of pancreas in blood vessels
- glucagon stimulates gluconeogenesis and glycogenolysis in the liver
-> increases blood glucose levels
ENDOCRINE SIGNALLING
Q: What is endocrine signalling? Aside from glucagon acting on liver cells, name 2 other examples.
A: hormone travels via the blood and acts on a distant target cell
Other examples of endocrine signalling:
- Insulin, produced in pancreas acts on liver, muscle, adipose
- Adrenalin, produced in adrenal glands acting on the trachea
Q: Why is adrenalin produced? (in response to)
A: as a result of sympathetic nerve activation (fight/flight)
Q: What’s the body’s physiological response to hyperglycaemia? Process? What’s this form of signalling an example of?
A: Hyperglycaemia
A: - glucose uptake
- reduced glycogenolysis
- reduced gluconeogenesis
need to also prevent glucagon production
- increased blood glucose, insulin secretion from beta cells in the islets of Langerhans
- Insulin has PARACRINE effects: inhibits glucagon secretion by nearby alpha cells
- Insulin also has ENDOCRINE effects on liver cells
Q: What is paracrine signalling? Aside from insulin acting on alpha cells, name 2 other examples.
A: hormone acting on an adjacent cell
Nitric oxide (gas) produced by endothelial cells in blood vessels (acts on vascular smooth muscle cells close by)
Osteoblast activating factors produced by adjacent osteoblasts (occurs during bone remodelling)
Q: Describe signalling between membrane attached proteins using an example from the immune systems.
A: 1. Blood borne virus (eg hepatitis C) is detected in the blood stream by an antigen presenting cell (APC)
- APC digests the pathogen -> expresses major histo-compatibility (MHC) class II molecules on surface
- Circulating T-lymphocyte engages with the MHC molecule through T cell receptor (TCR) interaction (gets signal via receptor interaction)
Q: Summarise communication via membrane-attached proteins.
Aside from T lymphocytes interacting with MHC molecultes via TCR interaction, give 2 other examples of membrane attached protein signalling.
A: plasma membrane proteins on adjacent cells interacting
- HIV GP120 glycoprotein binds to CD4 receptors on T lymphocytes
- Bacterial cell wall components bind to toll-like receptors on haematopoietic cells
Q: Describe the autocrine signalling involved in T cell activation.
A: Activated TCR will initiate a cascade of reactions within the T cell
Activated T lymphocyte has a interleukin 2 (IL-2) receptor on surface
Activated T lymphocyte secretes IL-2
IL-2 can bind to the IL-2 receptor on its own surface thus having an effect on the cell
Q: What is autocrine signalling?
Aside from T lymphocyte activation, give 2 examples of autocrine signalling. Both are?
A: signalling protein acts on same cell (signalling protein is produced by same cell that it acts on)
- Acetylcholine binds to pre-synaptic muscarinic receptors
- Growth factors from tumour cells can lead to mitogenesis in the tumour cell
(both feedback inhibition)
Q: Describe neuromuscular junction signalling. (5)
A: 1. Voltage-gates sodium channel (VGSC) opens - membrane depolarisation
- VGKC opens - membrane repolarisation
- Calcium influx through VGCC - leads to vesicle exocytosis
- Acetylcholine (ACh) binds to sarcolemmal nicotinic receptors (nAChR)
- ACh is metabolised by cholinesterase (ChE) and recycled
Calcium acts as a second messenger
