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PSHL231 Neurophysiology > Cellular Communication > Flashcards

Cellular Communication Flashcards

1
Q

What are hormones and their key features?

A

Hormones are chemical substances that act like messenger molecules in the body.

Co-ordinate different functions
Work slowly, over time
May affect different processes

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2
Q

What are the five ways of cell to cell communication using hormones?

A

Contact dependent
Paracrine
Autocrine
Synaptic
Endocrine

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3
Q

What is contact dependant cell to cell communication?

A

Communication that requires close contact between the signalling cell and the target cell.

In this type of signalling, a ligand on one surface binds to a receptor on another adjacent surface.

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4
Q

What is paracrine cell to cell communication?

A

Cells that are near one another communicate through the release of chemical messengers (ligands that can diffuse through the space between the cells).

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5
Q

What is autocrine cell to cell communication?

A

A cell signals to itself, releasing a ligand that binds to receptors on its own surface.

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6
Q

What is synaptic cell to cell communication?

A

Communication between two nerve cells.

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7
Q

What is endocrine cell to cell communication?

A

Involves cell targeting a distance cell by releasing hormone into the bloodstream.

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8
Q

What can happen to hormones circulating in the blood?

A

They can be excreted in urine or faces, activated or inactivated by metabolism or bind to receptors and produce a cellular response.

Important to note that hormones will not have the same effect on all cells and will have no effect on cells that don’t have the required receptor.

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9
Q

What is synergy?

A

Synergy is about two hormones combining together to create a bigger response that either are capable of on their own.

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10
Q

What happens if we release thyroid hormone (synergy)?

A

Little to no fatty acids released

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11
Q

What happens if we release epinephrine (in relation to synergy)?

A

Small amount of fatty acid released

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12
Q

What happens if we release thyroid hormone and epinephrine together?

A

Synergist effect - large amount of fatty acids released.

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13
Q

What is the effect of cell communication if we increase hormone levels circulating?

A

Increase chance of receptor interactions therefore increased response.

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14
Q

What is up-regulation?

A

An increase in cells number of receptors expressed to increase sensitivity.

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15
Q

What is down-regulation?

A

A decrease in cells number of receptors expressed to decrease sensitivity.

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16
Q

What does sensitivity of a target cell depend on?

A

The number of receptors expressed.

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17
Q

What are the three chemical classifications of hormones?

A

Peptides which are created from three amino acids to large proteins.

Amines which are derived from tyrosine amino acid.

Steroid which are synthesised from cholesterol.

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18
Q

What are sex hormones created from?

A

Cholesterol (a steroid ring structure)

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19
Q

Which hormones do not have receptors on their membrane?

A

Steroids and thyroid hormones because they are lipid soluble they require carrier proteins. They then bind to intracellular receptors in cytoplasm or nucleus.

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20
Q

What are amines formed from?

A

Tyrosine

Tyrosine can be turned into a heap of different things depending on the enzymes inside that cell.

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21
Q

Why can steroid hormones not be stored?

A

Because they are lipid soluble. Therefore once they are synthesised they diffuse out of the cell and circulate around the blood.

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22
Q

Can amines be stored?

A

Yes - they can be stored and released when needed.

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23
Q

Are thyroid hormones amines?

A

Yes - thyroid hormones are also amines (but amines are not thyroid hormones). This is because amines are not made from cholesterol but they are lipid soluble.

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24
Q

Where does synthesis occur?

A

Rough endoplasmic reticulum

25
Q

Where does packaging occur?

A

Golgi apparatus

26
Q

Where are vesicles stored?

A

Inside the cell

27
Q

What hormones have cell surface receptors and why?

A

Amines and peptides. Because they are not lipid soluble - if you are water soluble you have to activate a receptor because you cannot get across the membrane without it.

28
Q

What is the secondary messenger system and why do we have it?

A

Secondary messaging is where one signalling molecule activates numerous things within a cell. We have it because it is the more efficient way to activate the cascade of reactions.

29
Q

What is transcription?

A

Process of copying a section of DNA to RNA.

30
Q

What happens if there is no receptor for the steroid or thyroid hormone once it is inside the cell?

A

It will be broken down/metabolised inside the cell.

It has no effect on the cell.

31
Q

Where can steroids and thyroid hormones bind to receptors?

A

Cytoplasmic receptors (in the cell cytoplasm) or nuclear receptors (in the nucleus).

32
Q

How do steroids or thyroid hormones diffuse freely into cell when they are attached to carrier proteins?

A

Some of the hormone is not bound to the carrier protein and when this gets close to the cell they will diffuse into the cytoplasm and nucleus.

33
Q

What are the two main hormones released by the thyroid?

A

T3 and T4

There is a lot more T4 than T3 but it is the T3 hormone that is active.

34
Q

How does the cell self determine how much T3 action it gets?

A

Both T3 and T4 can freely diffuse into the cell, but cells can also up regulate by having channels to get addition T3 and T4 into the cell.

Inside the cell there are enzymes that covert T4 to T3.

35
Q

What are the effects of Thyroid hormones?

A

Na-K pump
Gluconegenc enzymes
Respiratory enzymes
Myosin heavy chain
Beta adrenergic receptors
Many others

(not growing really makes big moves)

36
Q

What do water soluble molecules require in order to enter the cell?

A

Plasma membrane receptors

37
Q

How do Ligand-gated ion channels open?

A

By a ligand binding to the receptor the channel is activated and opens.

38
Q

What is a GPCR comprised of?

A

A G-Protein Coupled Receptor includes a G protein with three subunits (alpha, beta and gamma) plus a receptor.

39
Q

What do the GPCR Gs, Gi and Gq stand for?

A

Gs = stimulatory = turns things on.

Gi = inhibitory = turns things off.

(Gs and Gi have the same pathway but different results).

Gq = queer - different pathway to the rest.

40
Q

Explain the G-protein Alpha Pathway:

A

Has inactive GDP bound to it - signaling molecule binds and causing change in receptor shape - GDP is released from alpha unit and this causes the alpha unit to be activated and it will disassociate from the other units - it has its effect on the cell.

Disassociated alpha subunit runs into, bind to and activates Adenylyl cyclase (protein in the membrane). Adenylyl cyclase converts ATP (3 proteins) into 3 cyclic AMP’s. AC when activated by alpha can do million reactions a second. AMP activates PCA - their job is to phosphorylate proteins which means to introduce a phosphate group to the molecule.

Channel in cell membrane activated when PCA phosphorylates it. The downstream effects of PCA is huge.

41
Q

What does Gq convert?

A

Converts inositol triphosphate into secondary messengers IP3 and DAG.

42
Q

What does IP3 do?

A

increases intracellular calcium levels as it has its own internal receptor / channel allows flow of calcium from endoplasmic reticulum to the cytoplasm.

43
Q

What are Eicosanoid Receptors?

A

A type of GPCR.

They primarily act on allergy/inflammatory response and uterine contractions for birth.

44
Q

What do Eicosanoid receptors activate?

A

Phospholipase A - which has a long pathway that turns lipids into other things.

45
Q

Define ‘hormone’ and classify signaling molecules (hormones and neurotransmitters) according to their chemical structures

A

A hormone is a signaling molecule. Signaling molecules can be classified based on their chemical structures. Peptides are formed from three amino acids to large proteins, amines are derivatives of tyrosine, and steroids are synthesized from cholesterol.

46
Q

Define and explain ‘hormone targeting’ and ‘synergy’

A

Hormone targeting refers to the specificity with which hormones exert their effects on target cells or tissues. Each hormone typically acts on specific target cells that express receptors for that hormone. Once a hormone binds to its receptor it triggers the cellular responses.

“Synergy” refers to the interaction between two or more factors or agents that results in a combined effect greater than the sum of their individual effects. In the context of hormone action, synergy may occur when two or more hormones act together to produce a physiological response that is more significant than the response produced by each hormone acting alone.

47
Q

Describe how different types of hormones exert their effects on target cells

A

Because some hormones are lipid soluble and other are lipid insoluble, they require either Intracellular or cell surface receptors.

Lipid soluble means that the hormone is able to dissolve through the lipid (fat) portion of the membrane.

Amines and peptides are lipid insoluble therefore the require a cell surface receptor in order to cross the membrane. Steroids are lipid soluble therefore they do not require a cell surface receptor but there do require a intracellular receptor either in the cytoplasm or the nucleus.

48
Q

Explain how activation of a small number of receptors can cause large responses in target cells

A

Through secondary massagers we can have a large response from just one signaling molecule turning on a lot of enzymes - which is the most efficient way to communication at a cellular level. Then through transcription activation we can have an effect on the nucleus also.

49
Q

Explain how some hormones act on cell surface receptors and others act on intracellular receptors

A

Some hormones act on cell surface receptors, while others act on intracellular receptors, primarily based on their chemical properties and solubility in the cell membrane.

Water soluble (lipid insoluble) hormones such as peptides and amines typically act on cell surface receptors because they cannot cross lipid bilayer due to their hydrophilic nature. Instead they bind to specific receptors located on the outer surface of the cell membrane which then triggers a series of intracellular signalling events involving a secondary messenger system.

Lipid soluble hormones such as steroids and thyroid hormones can diffuse across the cell membrane due to their hydrophobic nature. Once inside the cell these hormones bind to specific intracellular receptors which typically located in cytoplasm or nucleus.

50
Q

Is diacylglycerol (DAG) associated with Gq, Gs or Gi?

A

Gq

51
Q

What activates Phospholipase C?

A

Alpha subunits of Gq G protein-coupled receptors.

52
Q

Where in the cell is calcium released from when activated by IP3?

A

Endoplasmic reticulum.

53
Q

What activated adenylyl cyclase?

A

The disassociated alpha subunit of Gs GPCR.

54
Q

What does adenylyl cyclase convert?

A

ATP into cyclic AMP’s

55
Q

What is the activated effector of the alpha subunit after it has released GDP?

A

GTP

56
Q

What is cAMP?

A

Important secondary messenger which phosphorylates enzymes - secondary messenger system.

57
Q

Where does packaging of peptides occur?

A

Gogli apparatus

58
Q

Why are thyroid hormones amines (aswell as steroids) but amines are not thyroid hormones?

A

Thyroid hormones are derivates of tyrosine which makes them a amine.

But they are lipid soluble making then a steroid.

However, they are not made from cholesterol.

59
Q

Do males produce aromatase?

A

No - aromatase is what produces estradiol which is secreted by ovaries.

PSHL231 Neurophysiology (10 decks)

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