cell signalling and homeostasis Flashcards
How do cells signal through direct contact.
Via a gap junction in animal cells and via a plasmodosmata in plant cells
What is paracrine signalling
When molecules travel a short distance to signal other cells.
What is endocrine signalling
When molecules have to travel a long distance and potentially have to enter the blood stream.
What is an autocrine system
When molecules are reacting within themselves in the cell.
What is the general term for a molecule that binds onto a receptor
Ligand
Define homeostasis and how it is achieved.
Homeostasis is the condition of equilibrium in the body’s internal environment.
It is achieved by constant interactions of the body’s main regulatory processes.
What are the components of a feedback system.
Set point, control centre, effector, regulated vairable, sensor.
Give an example of the control centre, effector, regulated response, and the sensor
1.Control centre-the brain
2.Effector-Diaphragm and respiratory muscles.
3.Regulated variable- Arterial po2 normal range.
4.sensor-chemosensors.
Back to the control centre.
What is the gain of a regulated variable.
It is the precision by which a control system can prevent deviation from homeostasis.
How does the magnitude of gain affect the control of a regulated variable
A control system that has a large gain shows it has a more sensitive regulation that better maintains normal conditions.
What is negative and positive feedback
Negative feedback acts to reduce an effect whilst positive feedback acts to increase an effect, e.g. bloodclotting.
What are feedforward loops
A physiological response in anticipation of a change in variable, e.g. heart increase prior to a running race.
What is a reflex response
A reflex response requires knowledge from an integrating centre that connects the receptor and effector.
What is a local response
Local controls allow individual parts of the body to self regulate their responses to certain conditions.
