Module 10: Cell Signaling

Question 1

Why do cells communicate with each other?

Answer 1

1. To regulate their development and growth into tissues
2. Control their growth and division
3. Coordinate other activities

Question 2

How do cells communicate?

Answer 2

3 main ways:
1. Secreting chemical signals to targets at a distance
2. Displaying molecules on their plasma membranes
3. Forming gap junctions to allow for direct communication between cells

Question 3

Different methods cells use to send signals

Answer 3

Cells can send signals via:
1. Chemical mediators that act locally,
2. Hormones that travel through the bloodstream via the endocrine system,
3. Neurotransmitters at the synapses between 2 neurons

Question 4

Local chemical mediators→ methods of action

Answer 4

1. Paracrine = adjacent/nearby cells
2. Autocrine= the cell sends a signal to itself
3. Contact-dependent communication = through gapjunctions

Question 5

Different methods of the release of cell signals

Answer 5

Aka modes of secretion:
1. Merocrine
2. Holocrine
3. Apocrine

Question 6

Merocrine secretion

Answer 6

The cell secretes the signal by exocytosis, without any damage to the cell itself
Example: sweat glands, mammary glands

Question 7

Holocrine secretion

Answer 7

The whole cell is expelled during the process of secretion and the ruptured cell becomes part of the secretory product
Example: sebaceous glands

Question 8

Apocrine secretion

Answer 8

Only the apical part of the cell (the cell’s apex) is shed in the secretory product
Example: sweat glands in the armpit

Question 9

Cell signaling types

Answer 9

3 main types = autocrine, paracrine, and endocrine
All 3 types involve the secretion of some kind of chemical signal from a cell that binds to a receptor and causes a downstream effect.

Question 10

Autocrine signaling

Answer 10

A cell releases a signal that acts on itself, binding to receptors on the plasma membrane, and causing an effect within the same cell
Example: the release of the cytokine IL-2 from T cells

Question 11

The release of cytokine IL-2 from T cells

Answer 11

An example of autocrine signaling

This cytokine promotes the proliferation and differentiation of the same T cells → to protect our bodies via our immune system

Question 12

Paracrine signaling

Answer 12

The cell releases a signal that acts on nearby cells, causing a downstream effect in these target cells
Example: At the neuromuscular junction, where a neuron meets a muscle cell.

Question 13

The neuromuscular junction = junction where a neuron meets a muscle cell

Answer 13

An example of paracrine signaling
The neuron releases a signal onto the muscle cell → causes a downstream effect in the muscle cell once the signal has bound to the receptor in the muscle cell
Example: if the signal is acetylcholine, the downstream effect in the muscle cell leads to muscle contraction

Question 14

Endocrine signaling

Answer 14

A cell releases a signal that must travel through the bloodstream to reach its target cell, which is often very far away
General example: associated with the endocrine system →
Specific example: cascade of events that originates at the hypothalamus and ends in the testicles

Question 15

The endocrine system

Answer 15

One of the physiological systems in the body that controls hormones
Via the actions of these hormones, this system influences just about every other system of the body

Question 16

How the hypothalamus communicates to cells in the testicles

Answer 16

An example of endocrine signaling → a cascade of events:
1. The hypothalamus releases GnRH (gonadotropin releasing hormone)
2. GnRH acts on the anterior pituitary → releases LH (luteinizing hormone)
3. LH acts on the Leydig cells in the testicles → produces testosterone

Question 17

Neurotransmitter signaling

Answer 17

A very well-known form of cell signaling
Involves the chemical messages sent between 2 neurons at a synapse (the point where the processes of I neurons meet)