Mechanism Of Intercellular Communication

Question 0

Connexions and intercalated disks

Answer 0

Connexions are subunits that form channels (gap junction ). Pore size is very small to permit sugars, amino acids, and ion between cells.
Found in almost every cell except mature skeletal muscle

Intercalated disk type of gap junction found in cardiac muscle which allows for rapid and coordinated propagation of action potential for rhythmic contractions. Can be regulated by phosphorylation and dephosphorylation

Question 1

Direct and indirect communication

Answer 1

Direct is when their is a junction gap or a tunnelling nanotube or a mechanosignaling

Indirect is chemical messengers

Question 2

Nanotubes

Answer 2

Tubes ad e formed from plasma membrane larger then gap junctions and have larger pore diameters
For transferring nuclei acids small organelles between cells
The transfer of pathogens, virus and prions

Question 3

Mechanosignal transduction

Answer 3

Convention of mechanical stimuli into a cellular response
Direct physical stress on cells, eliciting a chemical or metabolic response

Shearing stress from blood flow on arterial endothelial cells
Can induce formation of new blood vessels
Is excessive, mediates vascular inflammation and progression of atherosclerosis

Remodelling of bone and cartilage through physical stress

Chemical stress of muscle fibres

Pressure on skin into neutral impulse

Soundwave into electrical signal

Question 4

Chemical messengers

Answer 4

Paracrines
Neurotransmitter
Hormones
Neuroendocrine

Question 5

Paracrine

Answer 5

Near by cells
Growth factors like estrogen, clotting factor

REMEMBER lots of secreted hormones can act in a paracrine fashion but also a endocrine fashion

Question 6

Neurotransmitter

Answer 6

Synapse is short
Signals must be tightly controlled ( not too many molecules released at ones and an auto shut off)

Ephedrine - stimulates norepinephrine release from presynaptic terminal
Caffeine- blocks adenosine feedback
Aspirin- block prostaglandin production

Ephedrine/ aspirin increase thermic effect of food in obese ppl
Eating meals increase metabolic rate
Notice the response to a meal is impaired in obese ppl but completely restored by ephedrine and aspirin combo to the same level as lean individuals

Weight loss
Caffeine nothing
Ephedrine a little
But together very affective

Question 7

Hormones

Answer 7

Water or lipid- soluble
Must cross membrane
Have target receptors

Hydrophilic messenger -water loving 
-insulin , epinephrine, serotonin 
-stored in secretory cell 
Dissolves in plasma 
Travels through vessel to cross lipid membrane 

Hydrophobic -water hating 
-steroid, estrogen,testosterone, cortisol 
-storage is limited (created on demand) 
-needs carrier 
Crosses lipid membrane no vessel needed

Question 8

Neuroendocrine

Answer 8

Norepinephrine and antidiuretic hormone

Neuron ->receptors in bloodstream -> to target cell to create response
Long duration

Question 9

Secretory tissues of body?

Answer 9

Kidneys 
Hypothalamus 
Anterior pituitary 
Adrenal gland 
Pancreas
Thyroid 
Sex organs 

Also skeletal muscle and adipose tissue

Most tissue have endocrine function

Question 10

Adipose tissue

Answer 10

Secretes 100s of peptides
Ex-leptin -decrease appetite , improves insulin sensitivity regulates fertility in females
-Interleukin 6, resistin, tumour necrosis factor -inflammatory , insulin de-sensitizing peptides
Adiponectin- stimulated fat oxidation, improves insulin sensitivity

Question 11

Skeletal muscle

Answer 11

Interleukin 6 released by muscle contraction, first discovered myokine, thought promote lipolysis

Irisin -discovery in mice, expression is increased by muscle contraction , thought to increase energy expenditure in adipose tissue ( convert white adipose tissue to brown a disposes tissue

Brown a adipose tissue small lipid vacuole more mitochondria higher metabolic rate (wasting energy as heat that is way higher metabolic rate)