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Flashcards in Slide Set 3 Deck (125)
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1

2 basic types of physiological signals

Electrical : involve changes in membrane potential
Chemical : molecules secreted by cells into extracellular fluid

2

4 methods of cell-cell communication

Gap Junctions
Contact-dependent signals
Chemicals that diffuse
Long-Distance communication

3

Gap junctions

- simplest form of cell-to-cell communication
- direct transfer of E and C signals
- creates cytoplasmic bridges between adjacent cells

4

Which molecules can pass or can't go through a gap junction

can : ions, amino acids, ATP, cAMP
can't : large molecules

5

Connexins

= proteins on the membrane that connects the cell in a gap junction

6

What is the only means by which electrical signals can pass directly form cell to cell

gap junctions

7

Contact-dependent signals

- interaction between membrane surface molecules on 2 cells
- immune system, growth, development
- Cell-adhesion molecules (CAMs)

8

What are CAMs

= Cell-adhesion Molecules
Are present in contact-dependent signals
They transfer signals, like integrins

9

Chemical signalling

- paracrine : signals secreted by ONE cell and diffuse to the NEXT
- autocrate : signals act on the SAME cell that secreted them

10

Long-distance communication

- HORMONES

- NEUROTRANSMITTERS

- Cytokines
(also local signalling)

11

HORMONES

Long-distance
- secreted by endocrine glands/cells into the blood
- cells with RECEPTORS for the hormone ("lock & key") will respond to the signal

12

NEUROTRANSMITTERS

Long-distance
= chemicals secreted by neutrons that diffuse across a small gap to the target cell
- use chemical and electrical signals
- have a rapid effect

13

Neurohormones
examples :

chemicals released by neutrons into the blood for action at a distant target
examples : norepinephrine and epinephrine

14

CYTOKINES

Local and long-distance signals
- all nucleated cells synthesise and secrete them
- control cell development, differentiation, immune responses
- have a broader action than hormones
- made on demand, not stored

15

Difference between cytokines & hormones

Cytokines act on a broader spectrum of target cells than hormones. Are like hormone but not produced by a gland, they are made on demand.

16

Signal pathways

1. Ligand/first molecules brings info/signal to target cell
2. Ligand-receptor binding activates the receptor
3. receptor activates one or more intracellular signal molecules
4. Last signal molecule initiates synthesis of target proteins or modifies existing target proteins to create a response

17

Signal molecule -> binds to __ -> activates intracellular signal molecule -> alters __ -> response

receptor protein
target proteins

18

Where are receptor proteins located

Inside cell or on the cell membrane

19

Location of ligand/receptor binding is dependant on whether a signal molecule is __ or __

hydrophobic or hydrophilic

20

__ signal molecules can diffuse through the phospholipid bilayer binding to __ or __ receptors

Hydrophobic
Cytoplasmic
Nuclear

21

Receptor activation often turns on or off a _
This is a relatively __ process

gene
slow

22

Lipophobic signal molecules __ diffuse through the plasma membrane

CAN'T
- they bind to extracellular receptors (on plasma membrane)
- causes a cascade of events

23

Lipophobic molecules
(hydrophilic)

- bind to extracellular receptors on plasma membrane
- very rapid response

24

Lipophilic molecules
(hydrophobic)

- diffuse through phospholipid bilayer
- bind to cytoplasmic or nuclear receptors
- slow process
(some can bind to membrane receptors in addition to intracellular receptors)

25

Why is the response slower for lipophilic signal molecules?

Because this is related to changes in genes activity,
the receptors bind in the nucleus

26

Where are receptors for lipophilic signal molecules?

- in cytosol
- in nucleus

27

Signal pathway of lipophobic signal molecules

- bind to cell membrane receptor
- forms ligand-receptor complex
- rapid cellular response :
- Initiates transduction by proteins
- second messenger

28

What is the role of the second messenger

- alters gating of ion channels
- increases intracellular calcium
- changes enzyme activity (protein kinases, protein phosphatases)

29

Steps of signal transduction pathway form a __

CASCADE:
inactive A becomes active A thanks to a stimulus, leased to inactive B becoming active B etc until product

30

Example of receptor-enzyme

tyrosine kinase
- is on the cytoplasmic side
- it transfers a phosphate group from ATP to a tyrosine of a protein