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 BioSciencesg.shaw@unimelb.edu.au

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