73. Communication among cells, Intracellular receptor signaling

Question 1

Communication among cells

Answer 1

• Three major regulatory systems:
  (1) hormonal
  (2) immune
  (3) neural systems

There are many similarities across the three regulatory systems. Endocrine, immune and neural systems are in close connection with each other.

-Functioning of all three regulatory systems is based on intercellular communication.

Question 2

Cell signaling

Answer 2

• Gap junctions - transportation of several substances across junctions. Neighboring cells may have an influence on each other by means of ion transport from the cytoplasm of one cell into the other, through the connexins of the contacting membrane surfaces.
• Information processing via molecules integrated in the membrane. It is a close physical proximity of the two cells. A molecule expressed on the surface of one of the cells makes a contact with an other molecule located on the surface of the neighboring cell. Typical between cells of the immune system.
• Cells located relatively far away, may also have an influence on each other by means of secreted molecules. This way of information processing is extremely manifold and very important for the functioning of both the immune and nervous systems.
• Cytoskeletal communication. Processing mechanical information that will influence the cell by the cytoskeletal system

Question 3

Type of communication?

Answer 3

Direct communication

Question 4

Type of communication?

Answer 4

Contact communication

Question 5

Type of communication?

Answer 5

Communication by secretion

Question 6

Type of communication?

Answer 6

Cytoskeletal communication

-Processing mechanical information that will influence the cell by the cytoskeletal system

Question 7

Four types of communication among cells:

Answer 7

• direct =gap junctions
• contact = molecules integrated in the cell membrane.
• by secretion = Secreting molecules between cells that are not so close
• cytoskeletal = Processing mechanical information that will influence the cell by the cytoskeletal system

Question 8

Receptor is in the cytoplasm

Answer 8

• Lipophilic hormones (steroid hormones, thyroid hormones, D hormone) can easily pass the cellular membrane and bind to cytoplasmic proteins (receptors).
• The receptor - ligand complex is able to enter the nucleus.
• There, the DNA-binding domain of the receptor protein “finds” specific DNA segments (usually a few amino acid long segment). These specific sites of the DNA are called HRE-s (hormone-responsive elements).
• The receptor complex activates the structure gene downstream to the HRE, this way specific biological response is initiated through the transcription of a protein, mostly an enzyme.

Question 9

Effects of the IC receptor

Answer 9

Question 10

Answer 10

classical endocrine

Question 11

Answer 11

Paracrine

Question 12

Answer 12

Autocrine

Question 13

Neuro-immuno-endocrine regulation

Answer 13

• Endocrine glands are controlled by the major autonomic regulatory center, the hypothalamus.
• Its function is dependend on the levels of hormones and information arriving from the nervous and immune systems.

These responses, or the changing amount of hormones provides a multiple-level feedback, which enables a fine tuning in the regulation