19 Flashcards
Two forms that oxygen is carried around the blood in
- dissolved O2
- bound to haemoglobin in RBCs
Describe oxygens ability to dissolve at physiological partial pressure
Oxygen dissolves poorly, due to its low solubility at physiological partial pressure
How much oxygen is dissolved per litre of blood.. how much oxygen do we need per minute ?
- only about 3ml of 02 per litre of blood, so about 15ml total.. we need about 250ml/min
O2 forms an ____ ______ combination with Hb to give _________
Easily reversible
Oxyhaemoglobin
What does O2 binding to Hb depend on?
PO2
Does haemoglboin contribute to the presssure gradient?
Yes - as it moves from alveoli into pulmonary capillary it binds to haemoglobin reducing the partial pressure in the pulmonary capillary - this creates a larger gradient and thus more can move from alveoli to capillary
- thus without haemoglobin you’d only have 3ml of oxygen in your blood
Oxygen- haemoglobin saturation curve
Percentage of heme units bound with oxygen - haemoglobin satuaration
Relationship between haemoglobin structure and oxygen binding results is a ______ curve
Singmoidal
Healthy indivaisual w it’ll have a haemoglobin concentration of…
98% (in arterial system)
As haemoglobin moves around body and gives oxygen to surrounding tissues what happens to PO2
It reduces
What is the p50
- indication of the affectingly of Haeme for oxygen
Why is the singmaiodal shape of the curve an advantage - upper flat part if the curve
- moderate changes in PO2 around the normal value (~100mmHg) have only small effects on the % satuatruaion and therefore the amount of O2 carried by the arterial blood… i.e some reserve capacity (buffer zone that can cope with a massive reduction in PO2)
Sigmoindal shape of the curve advantage - steep part of the curve at lower PO2
- helps with loading of Hb in lungs AND unloading of O2 in the tissues (makes it easier to unload to working tissue- only needs small drop in PO2 to release oxygen - more pronounced during exercise)
- small changes in PO2 results in large changes in amount of O2 bound to haemoglobin
What happens if u increase / decrease the affinity of Hb for O2 - BOHR EFFECT
Curve shirts left if u increase affinity ( oxyhemoglobin saturation increases)
Right if u decrease ( oxyhaemoglobin satuaration decreases)
- this is gaged by the p50
What is the Bohr effect
The haemoglobin binding curve can be shifted
How do u reduce O2 affinity and what happens to the graph
- lower plasma pH
- higher temperature
- shift to the right
What contributes to Bohr effect
- lower plasma pH
- higher temperature
- increase PCO2 - right shift - increase in CO2 —> H+ increases - reduces pH
- increased 2,3 biphosphoglycerate (BPG) - right shift
What is BPG
Metabolic byproduct
What happens when haemoglobin comes into a working tissue?
It experiences high temperature
- lots of CO2 (H+)
- bi product of metabolism BPG
Reduces affinity offloading the oxygen
Relationship with oxygen
Is always changing
Three ways CO2 is transported
- Dissolved in plasma - 20 times more soluble then O2 (~7%)
- As bicarbonate (70%)
- Combined with proteins as carbamino compounds (23%)
Carbon dioxide transport
Transport of O2 and CO2 in lungs and peripheral tissues - red blood cell
From the right bottom:
CO2 comes out of the tissues and into the plasma , some is dissolved, majority enters red blood cell, 23% will bind to haemoglobin, majority reacts with water to form carbonic acid which then dissociates into bicarbonate and hydrogen
Blood then travels back up to the lungs into Plomonary circulation - the dissolved CO2 diffuses back into alveolar (do to the partial pressure gradient) bicarbonate comes back into the red blood cell, combined with hydrogen ions forming carbonacid to then form a water and CO2, gradient then drives CO2 back into alveoli
Red blood cell now has no CO2 so is now increadbly attracted to the O2, oxygen moves into RBC
Where is the control of breathing centrally regulated ?
Medulla oblongata (brain stem)
Different neuron populations inevate different
Respiratory muscles
Respiratory rhythmicity centres
Generates cycles of contraction and relaxation in the diaphragm establishing pace of respiration; modify activity in response to chemical and pressure signals
What allows you to control ur breathing
Higher brain region - cortex
Control of breathing
Where are central chemoreceptors located?
In the medulla
What are the central chemoreceptors sensitive to?
- sensitive to the PCO2 but not to PO2 of blood
Two totes of chemoreceptors
Central chemoreceptors
Peripheral chemoreceptors
What happens when CO2 is too high - central? Receptors?
- CO2 diffuses out of the cerebral capillaries
- CO2 reacts with water to form ultimately bicarbonate and H+
- changes pH of the cerebrospinal fluid (CSF)
- central chemoreceptors respond to pH change
- relay information to respiratory centre saying there is an increase in CO2 - respiratory centre will increase breathing to get rid of the excess CO2
Where are the peripheral cemoreceptors located -
in the carotid and aortic bodies
What do peripheral chemoreceptors respond to?
Mainly respons to changes in arterial PO2, limited response to changes in PCO2
RAPIDLY RESPONDING
Peripheral chemoreceptors are ____ ______ing
Rapidly responding
Carbon dioxide receptors are the most important in determineing…
Respiratory activity
How do stretch receptors play a role in breahting
- as the lungs inflate of deflate, they send afferent input from the stretch receptor
- the brain then sends efferent output preventing them for stretching too far either way
Receptors also detect
Irritation
What triggers a sneeze or a cough
- receptors in mucosa are sensitive to irratence
- brain sending out efferent signals
