Lecture7&8- Principles of Hormone signalling

Question 1

What are the 2 major control systems of the vertebrate body ?

Answer 1

endocrine system
nervous system
required for effectuve cell-to -cell communication in large multicellualr organisms

Question 2

What does the endocrine system do ?

Answer 2

moniter and co-ordinate the internal environment and produce changes if required -(homeostasis)
-helps organisms to respond & adapt to changes i external environment
-hormones -regualting growth development,metabolism and reproduction

Question 3

How is hoemeostasis maintained ?

Answer 3

1.)stimulas prod change in variable
2.)detected by sensor
3.)input info sent along afferent pathway
4.)output: info sent efferent pathway to effector
5.)response of effector feeds back to influence magnitude of stimulas and returns variable to homeostasis

Question 4

What is Homeostasis negative feedback loop ?

Answer 4

controlled variable = room temp,sensed by thermostat
effector = heater

Question 5

What are hormones ?

Answer 5

a chemical agent prod and secreted bya spoecialised endocrine gland/tissue tht is transported in the blood stream to a sometime distant target where it elicits a phsiological
May be stimualtory or inhibitory
may act on several or 1 specific target tissue
responsive tissues must have specific receptors for particular hormone

Question 6

what are endocrin glands ?

Answer 6

majopr function is to produce hormones in response to a physiological state
secrete hormones into the blood stream or locally exorine glands secrete substances
some gland can secrete more than 1 hormone

Question 7

What are the principles of cell signalling ?

Answer 7

Individual cells must communicate with each other to carry out their functions-send and recieve signals
diffusible chem signals
-paracrine & autocrine signalling :local signals
endocrine signalling:via blood stream
gap junctions: connexins -also enable electrical coupling (synctium)

Question 8

How does intercellualr communication work ?

Answer 8

release of diffusible chemicl signals with local effects
-Paracrine signalling
- Autocrine signalling

Question 9

what is paracrine signalling ?

Answer 9

release of signal molecules that diffuse
short distances to affect nearby (neighbouring) target cells.
dont enter the blood stream

Question 10

what is autocrine signalling ?

Answer 10

releases self stimulating molecules secreted signal also acts on cells that secreted it
dont enetr blood stream

Question 11

What is endocrine signalling ?

Answer 11

release of signal molecules that diffuse over long distances to affect target cells

Question 12

What is neuroendocrine signalling /neurosecretion ?

Answer 12

Secretion of hormones from neurons

Question 13

What are the gap juctions between intercellular communication ?

Answer 13

-formed by connexins
-permit passage of ions and small molecules between cells enables metabolic coupling ,electrical coupling (synctium) and signalling via 2nd messenger (cAMP).
2-4 nm gaos between cells

Question 14

What are contact-dependent (juxtacrine signalling ) ?

Answer 14

Communications between adjacent cells involving membrane bound signals & receptor molecules

Question 15

What are the 3 main chemical classes of hormones ?

Answer 15

-Steroid
-Peptide & Protein
-Amine

Question 16

Steroid hormones and examples ?

Answer 16

Cholosterol derivatives ;lipid-soluble (hydrophobic)
eg.)cortisol (adrenal cortex)
testosterone (testes)

Question 17

What are Petide & protein hormones ?

give examples and what they are

Answer 17

Majority of hormones:water-soluble (hydrophillic)
-Small peptide :thyroptrophin-releasing hormone
-Protein (polpeptide):insulin,growth hormone(GH)
-Glycoprotein :follicle stimulating hormone (FSH)

Question 18

What are amine hormones ?

Answer 18

modified amino acids
eg.)tyrosine derivatives;water*,lipid-solubles
hydrophillic/phobic respectively

*catecholamines :adrenaline,noradrenaline;thyroid hormones:triidothyroni

Question 19

What are the 3 main chemical classes of hormones ?

Answer 19

Peptide & Protein-polypeptide(not lipid soluble)
Amine-derivatives(tyrosine,epinephrine)most not lipid solu
Steroid -cholesterol,cortisol-lipid soluble often binding to receptors

Question 20

Hormone transport in circulation ?

Answer 20

Catelcholamines & peptide proteins -are water soluble transported dissolved in plasma
Steroid hormone are lipid soluble transported bound to specific carrier proteins in plasma (many diff types)

Question 21

What is free hormone concentration ?

Answer 21

is physiologically important as bound hormone is not available to target cells (not affect )
free hormone + binding protein ↔ hormone protei complex

Question 22

How do the receptors control the activigy of target cells ?

Answer 22

1.)opens ligand gated channels (ionotropic)[fast]
2.)activating enzyme/enzyme linked membrane receptors (catalytic receptors)
3.Activates metabotropic (g protein coupled) receptor:indirectly opens ion channels or activates 2 nd messenger [slow]
4.Diffuses across cell membrane to activate gene expression

Question 23

How are signals detected in target cells ?

Answer 23

• when signals arrives at target cells the signal reception to detect the signals → receptors
• ligans binding initiates confromational change of receptors:
  1.ligand gated channels
  2.enzyme/enzymelinked
  3.G protein coupled receptors (GPCR)
  4.intracellular receptors

GPCRs mediate cellular responses in response to many hormones and neurot

Question 24

How do steroid hormones work ?

Answer 24

• cholesterol derivatives;lipid soluble
• transported in blood bound to CP
• Readily cross plasma membrane .Diffuse out of ce.s that prod them → synthesised ‘on demand’
• bind receptors found inside the cell :intracellular receptors → regulate gene expression

CP-carrier proteins
vertebrates-gonads,adrenal glands,skin & placenta se

SH found in cyptoplasm,nucleus

Question 25

Where are steroid hormones derived from ?

Answer 25

Cholesterol
6 carbon side chain is cleaved to form pregnenalone in the mitochondrian
-Pregnenalone travels to smooth ER where diff enzymatic processes produce different specific steroid molecules
-

effects of steroid hormoes usually take several hours -days
slow respon

Question 26

What are peptide & protein hormones and its properties ?

Answer 26

Majority of hormones -water soluble
-packaged into vesicles;r=released via exocytosis when needed
-easily transported in blood without the need for carrier protein
-Bind receptors found on the cell surface–>indirectly open ion channels &/or activate 2nd messenger

Difference between peptide/protein
size or structure
peptides-smaller t

Question 27

What are amines and their properties ?

Answer 27

Tyrosine derivatives;water or lipid soluble inclusing catecholamines & thyroid hormones
packaged into vesicles released by exocytsis when needed or siffuse out of cells that prod then synthesied on demand
easily transported u blood without carrier proteins
bind receptors found on cell surface or intracellularly

target cells may express different types of receptors –>capable of resp

Question 28

What does the endocrine system excrete ?

Answer 28

specific classes of hormones
-steroid
-peptides & proteins
-amines

Question 29

What are ligand gated ion channels ?

Answer 29

channel pore allowing specific solutes to enter the cell
-mostly at nerve terminals (synaptic signalling/transmission)
-secreted by -chromaffin cells of adrenal medulla~(considered specialised postganglionic sympathetic neurons)

Question 30

How do enzyme/enzyme linked receptors work ?

Answer 30

Insulin receptors is 1
-Hormone binds to cell surface receptors
-Activated receptor functions as a tyrosine kinase
-interacts directly with other membranes proteins–>cellular responses

binding to α subunits induces conformational change resulting in autopho

Question 31

What are GPCR’s ?

Answer 31

G protein coupled receptor
ligand binding to a GPCR activates G protein
:G protein bound to guanosine diphosphate (GDP) is inactive. The G protein is activated when bound to guanosine triphosphate (GTP).
-G protein dissociates :Gα and Gβγ interact with AC/PLC

AL/PLC-membrane bound-enzymes) & ion channels respectively

Question 32

GCPRs

Do different G proteins exist ?

Answer 32

All act as ‘biochemical switches ‘–>modulate ion channel activity or alter rate of 2nd messenger production
e.g)cAMP,IP3 DAG
-can regulate various intracellular events

signalling cascade:series of events linking the change in 2nd messenger levels to final response