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Human Physiology > Ch 6: Communication > Flashcards

Ch 6: Communication Flashcards

1
Q

Methods of cell-to-cell communication

A
  1. Gap junctions
  2. Contact-dependent signals
  3. Cells release messengers to the ECF
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2
Q

Gap junctions

A

Direct cytoplasmic transfer b/t adjacent cells
*aka communicating junction
- short distance
- transfer both chemical and electrical signals

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3
Q

Contact-dependent signals

A

Surface to surface contact b/t membranes
- proteins embedded in membrane
- short distance

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4
Q

Cells release messengers to the ECF

A
  1. Long-distance communication
    —hormones, neurohormones, & neurotransmitters
  2. Local communication
    —paracrine & autocrine
    *can go long distances
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5
Q

Cellular messengers

A
  • Hormones
  • Neurotransmitters
  • Neurohormones
  • Paracrine agent
  • Autocrine agent
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6
Q

Hormones

A

Released from tissue and travels to target cell thru blood

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7
Q

Neurotransmitters

A

Released from neurons to adjacent effector
- only from synapse to adjacent cell

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8
Q

Neurohormones

A

Released from neuron & travels to target cell thru blood

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9
Q

Paracrine agent

A

Released into interstitial fluid & affects neighboring target cell

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10
Q

Autocrine agent

A

Released into interstitial fluid & affects the cell that released it

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11
Q

Communication b/t cells also accomplished by?

A

SIGNAL MOLECULES (intracellular chemical messenger) & RECEPTOR

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12
Q

Receptors

A

Protein associated w/ the membrane or cellular interior which will bind a chemical messenger & exert an effect
*protein binding to a ligand
- highly specific
- high affinity for specific messenger
- can be saturated or blocked

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13
Q

Receptors can undergo…

A
  • Down-regulation
  • Up-regulation
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14
Q

Down-regulation

A

Decrease in receptor # in response to chronic elevated levels of messenger
- ex: Type II diabetes

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15
Q

Up-regulation

A

Increase in receptor # in response to chronic low levels of messengers

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16
Q

Routes of messenger action

A
  1. Lipophilic messengers
  2. Lipophobic messengers
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17
Q

Lipophilic messengers

A

Diffuse directly thru the membrane to an internal receptor
- lipophilic generally hydrophobic
- contains binding protein (amphipathic)
- relatively slow response, but persist in body
—ex: steroid (modifies transcription)

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18
Q

Lipophobic messengers

A

Must enter cell thru transport or bind to a surface receptor
- signal transduction
- fast responses (internal), but degrades quickly
- generally hydrophilic
- must bind noncovalently, causing protein to flex

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19
Q

Signal transduction

A

Message is conveyed from outside of cell to a new signal inside of the cell which then creates a cellular response
- converts one form of signal into a different form

19
Q

Signal transduction benefits the cell thru?

A
  1. Signal amplification (start small get big)
  2. Mutli-tasking (more than one effect)
19
Q

Transducers

A

Convert extracellular signals into intracellular messages which create a response

20
Q

Lipophobic messengers act on 4 types of membrane receptors

A
  1. Ligand-gated receptor channels
  2. Receptor enzymes
  3. GTP-binding proteins
  4. Integrin receptors
21
Q

Ligand-gated receptor channels

A

Receptor proteins that can act as an ion channel

22
Q

Receptor enzymes

A

Receptor acts as an enzyme & messenger binding initiates enzymatic activity resulting in cellular response

23
Q

GTP-binding proteins

A

Messenger activates a G-protein which opens an ion channel or activates an enzyme

24
Q

Integrin receptors

A

Messenger binding causes a change in the cytoskeleton

25
Q

Mechanisms of signal transduction (non-covalent binding)

A
  1. Messenger binds to ligand-gated channel
  2. Receptor enzymes
    —Kinase receptors
  3. GTP-binding proteins
26
Q

Messenger binds to ligand-gated channel

A

Now permeable to ion flux
- nicotinic, GABA, glycine
- depolarize, hyperpolarize, repolarize

27
Q

Receptor enzymes

A

When activated, receptor enzymes act as enzymes to alter cytoplasmic proteins
- allosteric activation

28
Q

Receptor enzymes: kinase receptors

A

Kinase receptors include many families of growth factors including: epidermal GF, platelet-derived GF, fibroblasts & insulin
- covalent modulation = phosphorylation of protein

29
Q

GTP-binding proteins (2nd messenger systems/ G protein coupled receptors [GPCR])

A

In a second messenger system, the intracellular messenger (or 1st messenger) binds non-covalently to a surface protein & activates a G-protein that initiates an internal chemical (or 2nd messenger) that initiates the cell’s response
- may open a channel or activate an enzyme
- “extra steps”

30
Q

2nd messengers

A
  • Cyclic AMP (cAMP)
  • Phospholipase C (GPCR)
31
Q

CAMs

A

Transfer signals in both directions

32
Q

Beta 2-Adrenergic Receptor

A

Transmembrane protein that noncovalently binds to epinephrine (adrenaline)
*signal transduction

33
Q

Steroid hormone influences?

A

Transcription
- slower responses related to changes in gene activity

34
Q

cAMP system (detail)

A
  1. Signal molecule binds to G protein-linked receptor, which activates the G protein
  2. G protein turns on adenylyl cyclase, an amplifier enzyme
  3. Adenylyl cyclase converts ATP to cyclic AMP
  4. cAMP (2nd messenger) activates protein kinase A
  5. Protein kinase A phosphorylates other proteins, leading ultimately to a cellular response
35
Q

ATP to cAMP to AMP

A

Phosphate group originally on C5, now on C3
- cAMP is an intermediate

36
Q

Cells prefer ATP

A

Energy is from phosphate to phosphate bond
- not influenced by bases

37
Q

GPCR: The Phospholipase C system

A

*Doesn’t attack phospholipids at random, only attacks one type
1 Signal molecule activates receptor and associated G protein
2. G protein activates phospholipase C (PL-C), an amplifier enzyme
3. PL-C converts membrane phospholipids into diacylglycerol (DAG), which remains in the membrane, and IP3, which diffuses into the cytoplasm
4. DAG activates protein kinase C (PK-C), which phosphorylates proteins (allosteric mod)
5. IP3 causes release of Ca+2 from organelles, creating a Ca+2 signal

38
Q

Agonist

A

Chemical messenger that binds to a receptor and triggers a cell’s response

39
Q

Antagonist

A

Molecule that competes w/ another for a receptor and binds to the receptor but does not trigger a cellular response
aka: anti-histamine?

40
Q

Epinephrine can bind to different isoforms of the adrenergic receptor…

A

Target response depends on the target receptor
- diff receptor = diff results

41
Q

Signal termination

A
  • After the cell’s response has been initiated, the 1st messenger must be stopped.
  • After the cell’s response has been initiated the 2nd messenger must also be removed.
42
Q

Many diseases & drugs have their effects at the?

A

Receptor or signal transduction step

43
Q

Signal termination: 1st messengers can be…

A
  • Degraded by extracellular enzymes (outside cell)
    —–ex: ACHE, MAO
  • Endocytosis of receptor-ligand complex (inside cell)
44
Q

Signal termination: 2nd messengers can be…

A
  • Degradation of the 2nd messenger
  • Pumping of ions out of the cytoplasm (put it back into its rightful organelle)

Human Physiology (8 decks)

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