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All the organs of the human body were having a meeting, trying to decide who should be the one in charge.
"I should be in charge," said the brain , "Because I run all the body's systems, so without me nothing would happen."
"I should be in charge," said the blood, "Because I circulate oxygen all over so without me you'd all waste away."
"I should be in charge," said the stomach," Because I process food and give all of your energy."
"I should be in charge," said the legs, "because I carry the body wherever it needs to go"
"I should be in charge," said the eyes, "Because I allow the body to see where it goes."
"I should be in charge," said the rectum, "Because I'm responsible for waste removal."
All the other body parts laughed at the rectum and insulted him, so in a huff, he shut down tight. Within a few days, the brain had a terrible headache, the stomach was bloated, the legs got wobbly, the eyes got watery, and the blood was toxic. They all decided that the rectum should be the boss.
So what's the moral of the story?
The asshole is usually in charge!
BioSciences
Copyright Notice
Figures and images indicated by KLES are taken from the subject textbook R B Knox, P Y Ladiges, B K Evans and R Saint, Biology, An Australian Focus 4th Ed, McGraw-Hill, 2009, with permission of the publisher. Diagrams and images without that designation are © Geoff Shaw, or are from public domain sources as indicated.
BioSciences
Strategies for Learning
• Revise early, Revise often.
Number of students downloading L19 notes from LMS (by 24/4, 06:30 AM)
Total students who have accessed at least one form of notes <700
Students who had NOT accessed any notes from LMS >1200
http://services.unimelb.edu.au/academicskills/undergrads/top_resources
BioSciences
… continued from lecture 19• Diverse gas exchange surfaces • Exchange rate area x pressure / distance (Fick’s
Law)• Structure and function of respiratory structures
– large surface area; rich blood supply; counter current flows; surfactant
• Roles of convection and diffusion for gas exchange• Mechanisms of breathing and significance of dead
space
BioSciences
1. O2 dissolves in water (or blood plasma)
2. O2 combines reversibly with haemoglobin (Hb)
3. In 100 mL of oxygenated human blood, there is about 0.3 mL dissolved O2 and 20 mL O2 bound to Hb (40 mL in whale).
Transport of oxygen
BioSciences
Iron-based respiratory pigments
The oxygen-binding unit is haeme - based
on Fe++.
Oxygen binding is not an oxidation.
Colour change
Haemoglobin• In vertebrate haemoglobin, 4 globins (2
alpha, 2 beta) form a tetramer, MW ca 68,000.– (Earthworm haemoglobin has MW ca 1,000,000.)
• Binds and transports O2
- reversible
• binds carbon monoxide
http://en.wikipedia.org/wiki/Hemoglobin
BioSciences
Oxygen transport in the blood• The amount of oxygen carried by blood is largely determined by the oxygen
dissociation curve for haemoglobin, and by the local partial pressure of oxygen (PO2).
100
50
75
25
0
% s
atu
rati
on
of
HH
b w
ith
O2
12040Blood PO2 (Torr)
98% 100%
Arterial blood
Venous blood- high [CO2] & more acidic,- low [O2],
(air)(alveoli)(tissue)
The right-ward shift of the curve at low pH is called the Bohr effect.
Note 1 Torr = 1 mm Hg
160
↑ acid
BioSciences
0 2000 4000 6000 8000 100000
40
80
120
160
PO
2 (
Torr
)
altitude (m)
Evere
st
CuzcoKos
ciusz
ko
Melb
ourn
e
BioSciences
Control of heart rate, blood pressure, and breathing
• baroreceptors (pressure)– great veins– aortic arch– carotid body
• chemoreceptors (chemicals)– carotid body : O2
– aortic body: CO2 and pH
• feed into vasomotor centre in brain stem- regulation of – respiration– heart rate; cardiac output– blood pressure– vascular tone (constriction of blood
vessel walls)
Brain
vagus nerve
phre
nic
and
thor
acic
ner
ves
to d
iaph
ragm
and
inte
rcos
tal m
uscl
es
Heart
vasomotor and respiratory centres in brainstem
Lungs
BioSciences
incr. local metabolites
baroreceptorsin carotid and aortic
bodies
EXERCISEof skeletal
muscle
decr O2, incr CO2
Chemoreceptors:- carotid bodies- aortic bodies
increased rateand strengthof heartbeat
vasoconstrictionof some ateries
Awareness inhigher centres
of brain
vasodilation of arteries to muscle
increased bloodto muscles
increased gasexchange
in lungs
local dilation blood vessels
Adapted fromKLES5 fig 24.18
Circulatory control and exercise
BioSciences
What drives ventilation?•Air-breathing tetrapods like us are very sensitive to CO2.
•Note - experiments with rebreathing air.
•Note - danger of hyperventilation before unassisted diving.
•Chemoreceptors (CO2/pH, O2) in carotid
and aortic bodies and (CO2/pH) in medulla of
brainstem
18 16 14 12 10 8 6 4 2 0
1 2 3 4 5 6 7 8 9 10% CO2 in inhaled air
% O2 in inhaled air
brea
thin
g ra
te (
L/m
in)
20
40
60
80
a small amount of O2
in inhaled air has little effect on
breathing rate
a small amount of CO2 in inhaled air stimulates a large
increase in breathing rate
BioSciences
Cells, Tissues and OrgansProfessor Geoff Shaw
School of [email protected]
Refs (list also includes some material covered in Lec 21): KLES5: Chap 7 esp. Tables 7.1-7.3 on pp 157-159, pp 163-174, Chap 28:
pp 680-685 KLES4: Chap 7: esp. Tables 7.1-3, pp 153-163, Chap 27:636-640Resources on LMSExamples of cells, tissues, organs, and their function and control
mechanisms in Lectures 18,19,21,22,23 (and others)
BioSciences
Our bodies are made up of ….• organ systems
– skeleton– muscles– nervous system– digestive system– circulatory system– respiratory system– ….. and lots lots
more
BioSciences
And organs are made up of cells and tissues
• Many different sorts– connective tissue– muscle– epithelium– glandular– neural– …. and so on…
BioSciences
Examples of tissues/cells
epithelium
connective tissue
muscle
blood
mouse uterus
BioSciences
Coordination
• at the inter-cellular level– example – NO and vascular control
• at the tissue/organ level – – eg signalling in the heart – coordinated
contraction…
• At the whole organism level – – eg cardiovascular coordination– endocrine reproduction
BioSciences
How do cells communicate?
• local – cell-cell contacts– chemical signals
• distance– neural – endocrine
fast
slower
BioSciences
Homeostasis
• from the Greek –homoios same–stasis standing still
• a tendency to maintain a constant internal environment
–also spelled Homoeostasis
BioSciences
Body Temperature
HEATgener-ation
Balance between heat generation and heat loss
“Cold Blooded” animalincrease heat loss ordecrease heat production
cooler
decrease heat loss orincrease heat production
hotter
“Warm Blooded” animal
Balance:heat loss = heat made const Temp
BioSciences
lizard sunning itselfon a rock…
BioSciences
Why do we maintain homeostasis?
waste energyrisk of predation
etc etc
BioSciences
Why do we maintain homeostasis?
waste energyrisk of predation
etc etc metabolic efficiency
less dependenton environment
etc etc
BioSciences
Control Mechanisms
SET POINT
SENSOR
INTEGRATORYSYSTEM
RESPONSE(EFFECTOR)
SYSTEM
BioSciences
NEGATIVE FEEDBACK
• Responses cause changes that tend to return to desired set-point
shiveringpanting
Goosebumps (pilo-erection)
remove clothes
seek shade/cool
sweating
resting seek warm place
movement
warm clothes
vasodilationvasoconstriction
BioSciences
POSITIVE FEEDBACK
• When responses increase the change from the set point– eg severely hypothermic person may
undress…– LH surge in female reproductive cycle
(discussed in a later lecture)– Birth (later in this lecture)
BioSciences
Homeostasis: body temperature
• costs: – metabolic energy needed to stay warm in
too cool environment– water loss for cooling (sweat, panting) in
too warm environment
BioSciences
Homeostasis: body temperature
• benefits:– cellular enzymes optimised for one
temperature, ↑ efficiency– can remain active in cold
• more time to forage• less risk of predation
– able to use wider range of environments
BioSciences
O2 + sugar CO2
Homeostasis: blood gas
Breathing and exercise:
O2tissues
blood
air
O2
breathingexercise
circulation
input output?
BioSciences
Homeostasis: blood gas
• hold your breath – what happens– ↓ blood O2 and ↑ CO2
– CO2 ↔ carbonic acid pH sensor …
Blood CO2
hold breath
urge to breathe too great. Deep breaths taken…
Time
excess CO2 lost quickly
“overshoot” and responses to correct (reduced breathing)
BioSciences
Hyperventilation
• rapid deep breathing–loss of CO2 increased pH
light headed, dizzy, tingling …
If ↑ CO2 = ↓ O2 dilation of arteries to brain
then ↓ CO2 = ↑ O2 contraction of arteries to brain
BioSciences
Homeostasis: blood glucose
Food
glucose+O2 CO2+H2O
absorptionstorage
transport
glucose + glucose +… glycogen
glycogen glucose +…
release
metabolism
metabolismstorage
absorptiongycogenolysis
transport
transport
BioSciences
Homeostasis: blood glucose
4.5 mmol/L
eat
ch
oco
late
rapid absorption
glucose metabolised…
eat
ch
oco
late
rapid absorption
If no “feedback” regulation…. (…diabetes…)
time
blo
od
glu
co
se
BioSciences
Insulin and glucagon• peptide hormones • made by islet cells in pancreas
glucoseglucose
glucose
glucose
glucoseglucose
glucoseglucose
glucoseglucose
glucose
GLYCOGENLiver cells
bloodINSULIN
GLUCAGON
BioSciences
Homeostasis: blood glucose
4.5 mmol/L
eat
ch
oco
late
ba
r
eat
ch
oco
late
ba
r
With “feedback” regulation…. (normal)
time
blo
od
glu
co
se high glucoseinsulininsulinglucose stored
in glycogen
low glucoseglucagonglucagonglucose released from glycogen
BioSciences
Multiple regulatory mechanism…• endocrine:
– insulin– glucagon– adrenaline– cortisol, …
• behavioural– hunger eating – satiety fasting– activities
• burn off sugar• lethargy, to conserve sugar
• etc etc etc…
BioSciences
Birth, an example of a non-homeostatic processes
contractionsstretch cervix
Pituitarygland
uterinecontractions
oxytocin release
neural reflex
Ferguson Reflex
What do I expect you to learn from this lecture?• Levels of organization within an organism
– cells, tissues and organs– communication between cells / tissues/ organs– endocrine and neural control
• What is homeostasis?• What are some costs and benefits of
homeostasis?• How do feedback systems work ?
(sensors integrators response systems)• Negative and positive feedback• Examples of some homeostatic systems
– body temperature– blood gases– blood glucose