Cell Signalling Flashcards
Define Homeostasis
Cells need to maintain a relatively stable internal environment, so that normal cellular functions can be performed am the cell can perform at optimum efficiency
This is called homeostasis
Define a stimulus
a detectable change in the internal or external environment
What two interacting systems control homeostasis in animal cells?
endocrine and nervous
define the endocrine system
the collection of glands that produce hormones that regulate metabolism, growth and development, tissue function, sexual function, reproduction, sleep, and mood, among other things
define the nervous system
the network of nerve cells and fibres which transmits nerve impulses between parts of the body
What controls homeostasis in plant cells?
plant regulators
define chemical messengers
a direct result of a change in the cell environment
cellular responses are due to the specific characteristic of the chemical messengers involved
Outline the steps in the Stimulus response model
Stimulus -> receptor->(messages sent)->Control centre->(messages sent)->effector->response
What is Negative feedback?
Common. forms a looped system that restores the condition to a steady state and has a stabilising effect
constant stabilising effect keeps extremes in balance
What is positive feedback?
Rare. results in the escalation of a response to a stimulus, causing system instability
they amplify a physiological response in order to achieve a particular result
A positive feedback loop will end when a natural resolution is reached
What are some examples of negative feedback?
sweating and shivering to stabilise body temperature,
What is an example of positive feedback
labour
which system is responsible for the production of chemical messengers?
the endocrine system
The chemical messengers produced in the endocrine system are called what?
hormones
Define hormones
organic molecules produced an secreted by one type of cell and travel via extracellular fluid (usually blood) and act on Specific Target Cells causing profound effects
Why do chemical messengers only act on target cells?
Only target cells possess receptors for specific chemical messengers
What are the three main groups of hormones?
Proteins/Peptide: (insulin, adrenalin)
Steroids (lipids): (testosterone, oestrogen)
Amino Acid derivatives: (thyroxin)
Outline Protein based hormones
protein-based hormones are water soluble, meaning thy cannot cross the lipid-layer of cells
protein-based hormones must activate receptors on the surface of the cell membrane to start the cellular response
Outline the signal transduction pathway
when a signalling molecule joins a receptor a set of chemical reactions (or cascade) occurs, known as a transduction pathway
the end result is a response that will have an effect on the stimuli (that generated the signal molecule that started the process)
Reception -> Transduction -> Response
Outline Steroid-signalling molecules
Lipid soluble, steroid molecules pass through the cell membrane and bind to a receptor protein found only in target cells. the hormone receptor complex then enters the nucleus and binds to particular sites on the cell DNA
This stimulates Protein Synthesis
What are the two main sections of the nervous sytem?
Central Nervous System (Brain + Spine)
Peripheral Nervous System
What are the three types of neurons?
sensory, intermediate and motor
What happens when neurons are stimulated?
when stimulated, neurons produce electrical impulses that are transmitted along the axon.
These impulses are transmitted across junctions called synapses
Outline a chemical synapse
one neuron releases neurotransmitter molecules into a small space (the synaptic cleft) that is adjacent to another neuron. The neurotransmitters are kept within small sacs called vesicles, and are released into the synaptic cleft by exocytosis
