Exam One - 1.7 Communication and Cell SIgnaling

Question 1

Physiological signals

Answer 1

Electrical signals
Chemical signals
Extracellular vesicles

Question 2

Local cell to cell communication

Answer 2

gap junctions - create cytoplasmic bridges
contact-dependent signals - chemicals diffuse through ECF to act on nearby cells (*paracrine or *autocrine)
Extracellular vesicles

Question 3

Long distance cell to cell communication

Answer 3

chemical (cytokines, myokines, exerkines, and hormones)
electrical signals

Question 4

gap junction

Answer 4

form direct cytoplasmic junctions between adjacent cells

Question 5

contact-dependent signals

Answer 5

require interaction between membrane molecules on two cells

Question 6

autocrine signaling

Answer 6

act on same cell that secreted them

Question 7

paracrine signaling

Answer 7

are secreted by one cell and diffuse to adjacent cells

Question 8

Ctyokines

Answer 8

• both local and long distance signals
• peptides, synthesized and secreted by all nucleated cells in response to a stimuli
• *growth factors (important family)
• in development and differentiation, they usually function as autocrine or paracrine signals
• in stress and inflammation, some may act on relatively distant targets
• differ from hormones because they cannot be stored for later

Question 9

Extracellular vesicle types

Answer 9

Exosomes
microvesicles
- may contain proteins, peptides, RNA
- can merge with other cells (targets)

Question 10

When does a cell respond to a chemical signal???

Answer 10

A cell responds to a particular chemical signal only if the target has a receptor

Question 11

Describe the basic signal pathway

Answer 11

• Signal molecule (ligand)
  binds to…
• Membrane receptor protein
  which activates…
• Intra-cellular signal molecules
  which alters…
• Target proteins
  which creates…
• The Response

Question 12

Receptor locations can be…

Answer 12

Inside the cell or outside the cell

Question 13

Where are lipophilic signal molecule receptors?

Answer 13

Inside the cell!

• signal molecules diffuse through the cell membrane and usually bind to cytosolic receptors or nuclear receptors

Question 14

Where are lipophobic signal molecules?

Answer 14

On the cell membrane!

• signal molecules bind to receptors on the cell membrane!

Question 15

Membrane receptor categories

Answer 15

• Channel: ligand opens or closes channel
• G protein-coupled: opens an ion channel or alters enzyme activity
• Catalytic: receptor enzyme (activates intracellular enzyme) or integrin receptor (alters enzymes or cytoskeleton).

Question 16

Signal transduction

Answer 16

transducer converts a signal from one form to another
- extracellular signal is first messenger (activates protein kinases and amplifier enzymes)
- intracellular signal is the second messenger (alter gating of ion channels, increase intracellular CA, change enxyme activity)

know difference between cascades of activation steps and signal amplification

Question 17

What type of membrane receptor does signal transduction often use?

Answer 17

G protein coupled receptors (GPCR)
Many lipophobic hormones use GPCR-cAMP pathways
GCPR also use lipid-derived second messengers

Question 18

Integrin receptors

Answer 18

membrane-spanning proteins

outside the cell, integrins bind to extracellular matrix proteins or to ligands

inside the cell, integrins attach to the cytoskeleton via anchor proteins

Question 19

Ca+ as an intracellular messenger

Answer 19

often used for signal amplification
is not left to hang around in cytoplasm after an AP

Question 20

Soluble Gases

Answer 20

short acting paracrines or autocrines

Question 21

Nitric oxide (NO)

Answer 21

diffuse into smooth muscle and causes vasodilation
synthesized by nitric oxide synthase (NOS)

Question 22

Other gas signal molecules:

Answer 22

carbon monoxide (CO)
hydrogen disulfide (H2S)

Question 23

Are carbs, lipids, or proteins important for paracrine signaling?

Answer 23

-lipids

ex. Leukotrienes have an important roles in asthma and anaphylaxis

Question 24

modulation of signal pathways

Answer 24

specificity
saturation
competition
agonist/antagonist
up-regulation versus down-regulation
cells must be able to terminate signal pathways
many diseases and drugs target the proteins in signal transduction

Question 25

target response depends on target receptor. Explain epinephrine and blood vessel example

Answer 25

Epi binds to alpha adrenergic receptor and the blood vessel constricts (intestinal blood vessel)
Epi binds to beta adrenergic receptor and the blood vessel dilates (skeletal muscle)

Question 26

How does cholera toxin affect signal pathways?

Answer 26

antagonist to enzyme activity of G proteins, cell keeps making cAMP
ions secrete into lumen of intestine, causing massive diarrhea

Question 27

Homeostatic reflex pathways (4)

Answer 27

1 - nervous regulation of internal environment
2 - tonic control
3 - antagonistic control
4 - one chemical signal can have different effects in different tissues

Question 28

Tonic control

Answer 28

like a radio volume dial. not just on or off, but somewhere in the middle

Question 29

Antagonistic control

Answer 29

ex. sympathetic nerves increase HR but parasympathetic nerves decrease HR

Question 30

What does target response depend on?

Answer 30

Target response depends on target receptor!

Question 31

What do long distance pathways maintain?

Answer 31

Homeostasis

Question 32

What are the steps in a reflex pathway?

Answer 32

1 - stimulus
2 - sensor
3 - input signal
4 - integrating signal
5 - output signal
6 - target
7 - response

Question 33

control systems vary in?

Answer 33

speed and specificity

specificity - neural is more specific than endocrine

Question 34

What are the 3 different kinds of signals in a control system?

Answer 34

neural - electrical and chemical
endocrine - only chemical (hormones)
neuroendocrine - electrical and chemical (neurohormone)

speed - neural is faster than endocrine
duration of action - neural is shorter than endocrine

Question 35

How fast is nerve conduction velocity?

Answer 35

if mylenated motor neurons can be 268 mph

Question 36

how fast is nerve conduction velocity for pain?

Answer 36

3mph

Question 37

how fast is blood flow velocity?

Answer 37

• depends on HR
• about 3-4 mph