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Lecture notes

Biomedical Sciences 2 lecture notes

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Topics:Cell communication, Body fluids, Synaptic transmission in the CNS, Chemical synaptic transmission, Nervous system, Data Analysis, Reproductive system , Respiratory system, Endocrine system

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  • May 15, 2022
  • 78
  • 2021/2022
  • Lecture notes
  • N/a
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chiaza
BMSZ (semi)




2021/2022

,Principles
cell
of
communication

,CELL Lt +2
COMMUNICATION




L1


How do cells communicate ?

1) Gap junctions
soluble signals
for
↳ small


Allows communication without membrane
needing to
negotiate with plasma
↳ .




2) Free diffusion

for hydrophobic molecules




3) Pumps / transporters / ion channels / vesicle fusion/fission / indirect

far hydrophilic molecules




How are
signals released ?
1) Exocytosis (constitutive evoked release) or




proteins, peptides, aa
,
nucleotides




2) Channels r
transporters ¢ or
e)
↓ ↓
↳ ions passive gated


3) Free diffusion (c)
↳ steroids,
gases




Forms
of signalling
PARACRINE

AUTOCRINE

SYNAPTIC signals highly concentrated @ synapse receptors
low-aqim.ly

are : .
are



ENDOCRINE →
signals get diluted @ blood : -


receptors are
high-affinity
GASEOUS (can bypass plasma mem .
+ receptors to activate enzymes directly inside )
cell

, L2

4 major types of receptors
v.
fast IONOTROPIC -



flow of ions across membranes down
dveousiongr .
A membrane potential
nicotinic Alk R
e)
.




fast METABOTROPIC / G- PROTEIN -
LINKED -




generate new
signals inside cell
(2ⁿᵈ messengers) regulate activity of
muscarinic Ach R ↓ ↓ membrane-bound
eg
a




tht
.




7- transmembrane a P 8
opioid R 3 subunits :
, ,
" """
target protein
domain structure
/\/ -


(enzyme channels
""
to receptor
to membrane
config or ion
+

to
-
GDP
a④
Upon ar
:
GTP attached instead 1) activation a subunit
of
-




2) release /8 subunits to target protein
g p
termination hydrolysis of
signalling by a-subunit
ATP GDP
of
: →

=




fast KINASE
modify existing molecules to
generate signals (are enzymes usually) + can also control
-

new


gene transcription
autophosphorylation ↓
ligand binding FÑÑÑaÉ
mum
themselves enzyme activity
is inside the cell




creates additional interaction sites


for more recruitment o
phosphorylation


amplify their
signal via a series
of phosphorylation reactions




termination of phosphatases
signalling
:



=


ligand binding
required for can bind

NUCLEAR/
DNA
binding
without
ligand
↓ ↓
slow STEROID -




change expression of genes ( in
cytosol or in nucleus
)

steroid hormones,
thyroid hormones , retinoids ,
✓ it -
D
( aka meat, hyE signals) freely diffuse
membrane → bind to intracellular receptors this activation
regulates transcription of genes
across →
directly
activated within 30min
1° response =
specific genes
other activated
2° response genes
=

, Same have tors
divergent effects
signal can :





their location have different
is
affinities
hey to the
physiological for ligands
response




L3
Difference in
fingerprints between identical twins . : one
piece of anatomy cannot be

determined
by a
b¥nt

kidney intermediate
mesenchyme
L >


embryonic origin metanephwgenic mesenchyme urelewc bud
:
+



↓ ↓ [branching]
nephron collecting duct
how this
branching
is


controlled ?
test this L
by looking for Hypothesis :
cells around UB


pins AND
mathers that ⇐ (mesenchymal cells) secrete

are in the
right place for this a
signalling substance
UB


I

④ UB grind to
express net & MM to express INF } Ret / ADNF
signalling

antibody binding
to GDNF to
test to / GDNF
Ret
by interrupting

the prevent its binding
neay for branching regulation
see
if
is
signal to net

+
beads
agarose
soaked in
test to see
if Ret/ a DNF is
Ñt for branching regulation by introducing an ectopic signal

daooenentats
(replace ADNF)

and
placing
r




them in close

proximity to a v



early tube .

, by experimental
same


/ processes
Other discovered that communicate to UB where /when it should
signals elongate
:




"

BMP2
"
-


keep out

BMP 7
" "




go straight
-




BMP4
"


TGF,
"


elongate
-




,




~


How do branches not
tangle ?
(horrid )
i

hypothesised Self loathing
'




Égqg
-
: -
model :
UB secretes a substance whose cone .
directs


branching direction
(towards least [horrid])


Experimental model :
culture
kidneys aimed at one another before adding various test
drugs
I
BE found to be a
¥sne signal (made
from
U
B)

How do MM to waste cells ?
cells sense when MM condensates are
large enough to
fam a nephron or not be too large

↳ sÉsmgsystemw) Wnt
a
quorum -




Quorum →
4 autocrine
signal within
sensing
=

no MET



÷÷÷÷É;É÷
MM that
nurse : propagates
✗ -1 -



mass wntl,
mesenchymal aggregation




÷÷%%%
o o




7

; I
,




f
°



@nt 4] threshold reached
o
o
°

if
¥É¥¥ :
o o o o
o > > Control
8. % go
.
°
o
renal vesicle RV) starts to
(
differentiate into nephron .




°
J o
o

+
> Li
¥1


; .
too
gew Lit =
illusion
of Ñ[Wnt4]
cells




Emergence the presence
of properties
at
system level that not present at component level
-
-
are



(Eg branching tree not present in cells but
)
emerged during developing organ

,L4


Drug
a chemical that produces
biological effect when given to
living organism
~
a a




}
→ structure must be know


FDA definition
not a nutrient




Medicine contains its components
drugs as one
of



Drug action is selective +
specific
↳ absolute however
specificity is never



(drugs often interact with +9 protein targets side
effects)
-
k -
i receptors
LIGAND t RECEPTOR LIGAND / RECEPTOR COMPLEX
^
k +1


¥%
Equilibrium constant (k ) ,
=

quantifiable measure
of affinity measured
by ftp.?y?-
K
☒É
'




n
aˢˢʳiaHcnrate_
-




KD =


KI
=

dissociation rate
(lug )
scale




÷:;H
• that
receptors




k☐ =




KD 50% og receptors occupied
ligand
=
conc .
at which are




The
higher ligand (
the K →
the the the
smaller
, affinity of as
@my]
less is required
to
occupy
50% q receptors )
Beland.pe#eptor-cupan-oy-ofoeot-
Most
frequently it is the effect to a of
"
a
drug (Aao Nist)
that is
quantified and not
Cigand]
↳ "




guinea pig
-
ileum
,
receptors in
gut practical .

, drug Che
The effect to administration
of
a
functional response) is
usually
not
directly proportional
to receptor
occupancy
responses of the
aha same
occupancy
evokes
different drug .




eg .




Due to this :
the [agonist] at 50% response ≠ K,


The effective dose at which response =
50% of Max . (ED )
so
is nevertheless useful as it allows


comparison of the potency of duooerent drugs .




Efficacy ~
the
ability of agonist
to
an elicit an
effect once bound to receptor


Drug A efficacy Drug B
>




Antagonists
have
affinity and
zeweqgicacy (only agonists have
efficacy)
^ competitive reversible
antagonist




[
,



response


competitive , irreversible antagonist
in.nea.ng@tag.ni.y




Allosteric modulators receptor fue
alters action
of agonist by binding to an site neutral
ve

accessory
-
-
on -
or
,




(
allosteric
modulation
no
effect in absence of
agonist

, NiiÑeptc
1) ligand-gated ion channel
(agonist binding allows rotation
of pore
-




lining region →
opening gate


Has 2
binding sites

both with
rely charged Glu Asp aa residues → interact with +ve trim
ethyl ammonium components
-
- +




Ach
of .




-



have polar residues → coordinate rest
of molecule these interactions
form basis of
affinity
not identical however
affinity
-
→ As in




Muscarinic Ach receptor


2) a protein -

coupled
its
binding site
is v.
different from (1) but still has high aqginity
-




D-mytargets #targets)
# RECEPTORS

- 10N CHANNELS (blockers

or allosteric
modulators
local
ey anaesthetics



°Ñ ENZYMES (inhibitors , false sybstrates or
pro
-




drugs)
\
abnormal inactive -→ active
produce
reaction product

☒= TRANSPORTERS (inhibitors or
false substrates
(for non -

lipid hydrophilic )
, \
leads to accumulation

of
abnormal compound

, Body
Fluids

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