BIOL124 - L1

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  • Created by: Katherine
  • Created on: 02-06-16 14:07
Why are signalling symstems needed?
To coordinate the activities of cells/tisseus in a multicellular organism.
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Give examples of the activities when signalling systems would be needed:
Neurotransmission, coordination of developmental process. Homeostasis (maintenacne of a constant internal balance)
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What are the types of signalling between cells:
Free diffusion between cells. Signalling via cytoplasmic connections. Direct cell-to-cell contact.
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What are the three types of signalling by free diffusion?
Autocrine, paracrine and endocrine
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What is autocrine signalling?
Signalling and reception by the same cell
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What is paracrine signalling?
Signalling between nearby cells
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What is endocrine signalling?
Signalling between distant cells
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How does autocrine signalling work?
The cell secretes chemicals that modify its own behaviour. Oftern associated with growth regulation (negative or positive)
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How does paracrine signalling work?
Cell signalling to neighbouring cells. Effects are local and short lived. Important e.g in coordinating the actions of neighbouring cells in embryonic development.
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What is synaptic signalling?
Highly specific and localized type of paracrine signalling between two nerve cells or between a nerve cell and a muscle cell.
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When is endocrine signalling?
Ductless glands called endocrine glands secrete hormones into extraceulluar spaces, which then diffused into the circulatory system.
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What are the endocrine glands?
Pituitary gland, adrendal gland, thyroid gland
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How is signalling via cytoplasmic connections done?
Transfer of signal from one cell to its neighbour through pores in the membrane. The fastest mode of cell-cell communication. e.g muscle cells in the heart communicate with each other via gap junctions, allowing all heart cells to contract simultan
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What does signalling by cell to cell contact involve?
Specific interactions between surface molecules on one cell, and receptors on another clel. Responsible for cell-cell recognition in animals. Important in embyronic development and immune response.
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What type of diffusion is free diffusion?
Autocrine, paracrine, endocrine
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What are the two types of signalling molecules?
Local regulators - act on cells in the vicinity (autocrine & paracrine signalling) 2.) Hormones - act at a distance (endocrine signalling)
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What are local regulators?
Growth factors, gases, prostaglandins, neurotransmitters
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What is a growth factor?
A peptide/protein that stimualtes cell proliferaton. It may have >1 target cell and hence >1 function.
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Give an example of a growth factor:
Nerve growth factor (NGF) - a small protein that regulates growth of target neurons
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Give an example of a gas local regulator:
Nitric Oxide (N=O) acts as a paracrine signal molecule (transient - hald life is only 1-5 sec) It is synthesized from arginine by nitric oxide synthase.
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What does nitric oxide do?
Induced vasodilation in the cardiovascular system.
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What are plostaglandins?
Modified fatty acids
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What are the multiple functions of these?
Excitability of the uterine wall during childbirth - placental secretion helps to induce labour. Induction of dever and inflammation in the immune system e.g. Aspirin inhibits these
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Give examples of neurotransmitters:
Acetylcholine, Biogenic amines (serotonin) Amino acids (Glutamate), Neuropeptides (endorphins). Some neurotransmiters are inhibitory, some excitatory, some either.
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Where are neurotransmitters found?
Some in both the CNS and the peripheral nervous system.
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What are hormones?
Secreted by endocrine glands and transported in the bloodstream. Hormone production controlled by neuroendocrine system (hypothalamus is control centre)
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What are the major galdns of the endocrine system?
Parathyroid glands (behind thyroid), adrendal glands, pineal gland, pituitary gland. testes, ovaries, thymus.
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A simple endocrine pathway is an example of ...
Negative feedback loop
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What is the simple endocrine pathway?
Stimulus, endocrine cell, blood vessel, target cells, response which then effects the stimulus.
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What is homeostasis?
Maintenance of a releatively stable internal environment in the face of stress from the external and internal environments. I
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Is the internal environment constant?
No, it is not, it is in a dynamic equilibrium, where changes are kept within an acceptable range (by means of negative feedback loops)
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What is the process of homeostasis of blood glucose through negative feedback loops?
When blood sugar is high, beta cells of pancreas stimulate to release insulin = body cells take up more glucose, liver takes glucose and stores it as glycogen. Blood glucose level decline to a set point stimulus for insulin release diminished.
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What about when the blood sugar is low?
Alpha celsl of pancreas stimulate to releate glucagon into the blood, liver breaks this down and released glucose to the blood. Blood glucose level rises to set point. Stimulus for glucagon diminishes.
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What are the two main classes of hormone?
Peptides and proteins, and steroids.
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What is an example of a peptide and protein?
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What do peptides and proteins do?
Bind to receptors on the cell surface, trigger events within cell cytoplasm through second messengers
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What do steroids do? And give an example:
Testosterone - Manufactured from cholesterol, can pass across lipid bilayer of plasma membrane and bind to receptors within cell.
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What is signal transduction?
The conversion of a signal at the cell surface to a specific cellular response is a multi-step process termed signal transduction pathway.
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What are the 3 main stages in signal transduction?
Reception of the signal at the cell surface, transduction of the signal, the cellular response (output response)
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What does reception of the signal at the cell surface involve?
Involves binding of a signal molecule to a specific receptor at the cell surface, changing the conformation of the receptor.
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What does transduction of the signal invovle?
Converting the signal into a response usually involves multiple steps (e.g. protein phophorylation by protein kinases)
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What is transduction of a signla?
Multistep pathways can amplify a signal: A few molecules can produce a large cellular response. Multistep pathways provide more opportunities for co-ordination and regulation.
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What does the cellular response involve?
It invovles a signal transduction pathway leading to regulation of one or more cellular activities.
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Where does the cellular response occur?
A signal transduction pathway leads to regulation of one or more cellular activities.
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Some pathways regulate the activity of enzymes, other do what?
Switch on genes by activating transcription factors.
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How is signal specificity obtained in signal transduction?
Different kinds of cells have different collections of proteins. These differences in proteins five each kind of cell specificity in detecting and responding to signals. The response of a cell to a signal depends on the cell's paticular proteins.
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What further helps the cell to coordinate incoming signals?
Pathway branching and cross talk
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Give examples of the activities when signalling systems would be needed:


Neurotransmission, coordination of developmental process. Homeostasis (maintenacne of a constant internal balance)

Card 3


What are the types of signalling between cells:


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Card 4


What are the three types of signalling by free diffusion?


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Card 5


What is autocrine signalling?


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