signal

Question 1

Why do we need cell signalling?

Answer 1

to process info
self preservation e.g. reflex arc to save from damage
voluntary movement
homeostasis

Question 2

The two main systems within the body that provide these lines of communication are:

Answer 2

Nerve fibres of the central and peripheral nervous system.

The blood vessels of the cardiovascular system.

Question 3

difference between the the 2 forms

Answer 3

nervous system rapid and short lasted

blood/hormonal response slower but longer lasted

Question 4

main hormone communication organs

Answer 4

Endocrine communication (see video 2)
Paracrine communication (see video 3)
Communication between membrane receptors (see video 4)
Autocrine communication (see video 5)

Question 5

endocrine response

Answer 5

hypoglycaemia- glucagon released form pancreases a cells of islets of langerham
travel via blood to the liver
cause glycogenlysis
gluconeogenisis
hormone travel within blood vessel to distant target

Question 6

paracrine response

Answer 6

hyperglycaemia has both para and endo 
increase in glucose uptake 
reduction in both g's 
released from b 
paracrine has inhibits ADJACENT a cells secreating glucagon  
hormone acts on adjacent cell

Question 7

membrane receptors communication

Answer 7

happens when antigen presenting cells presents pathogen antigen on their surface to a t lymph and they interact
plasma membrane protien in adjacent cell interact

Question 8

autocrine

Answer 8

when a signal molecule acts on the same cell it was secreted from
t cells release il 2 and it binds to the il 2 receptor on the same cell

Question 9

what are chemical messengers referred to

Answer 9

ligands

Question 10

gen overview

Answer 10

ligand bind to protein
activates
causes second messenger

Question 11

4 receptors

Answer 11

Ligand-gated ion channel receptors
G protein coupled receptors
Enzyme-linked receptors
Intracellular receptors

Question 12

Ligand-gated ion channel receptors (ionotropic receptors)

Answer 12

The ligand binds to the receptor protein
A change in conformation of the channel protein results in the opening of a pore, which spans the cell membrane.
The pore allows ions to move in or out of the cell according to their respective concentration gradients

Question 13

G protein-coupled receptors/ 7-transmembrane receptors

Answer 13

in the resting state the G protein complex consists of a Gα subunit, a Gβγ subunit and an associated GDP molecule, which are in close proximity to the receptor
Ligand binding causes the G protein complex to associate with the receptor resulting in the GDP molecule being phosphorylated to a GTP molecule
The Gα subunit dissociates from the Gβγ subunit
Both Gα and Gβγ can act as second messengers
When the ligand dissociates from the receptor, internal GTPase on the Gα subunit hydrolyses GTP to GDP
The Gα and Gβγ subunits re-associate and are once again available to the receptor

Question 14

Enzyme-linked receptors

Answer 14

Ligand binding results in receptors clustering.
Receptor clustering activates enzyme activity within the cytoplasmic domain.
The enzymes phosphorylate the receptor.
This phosphorylation leads to the binding of signalling proteins to the cytoplasmic domain.
These signalling proteins recruit other signalling proteins and a signal is generated within the cell.
The signal is terminated when a phosphatase dephosphorylates the receptor.

Question 15

Intracellular receptors function

Answer 15

Steroid hormones are membrane permeable
Intracellular receptors are essentially transcription factors
regulate mRNA and protein synthesis

Question 16

intracellular receptor working

Answer 16

Type I receptors are located within the cytosolic compartment and are associated with chaperone molecules (normally heat shock proteins, hsp). Once the hormone binds to the receptor, the hsp molecule dissociates allowing the hormone-receptor complex to form a homodimer with another identical hormone-receptor complex. The homodimer subsequently translocates to the nucleus where it binds to DNA and acts as a transcription factor (also see video 9).

Type II receptors are located within the nucleus of a cell and are often already bound to DNA. Binding of the hormone ligand to the receptor usually results in direct transcriptional regulation by the activated hormone-receptor complex.