Chapter 6.2 - Regulation of gas concentrations

Question 1

What is the cellular respiration equation?

word and chemical

Answer 1

Oxygen + Glucose –> Carbon Dioxide + Water + Energy

6O2 + C6H12O6 –> 6CO2 + H2O + ENERGY

Question 2

Why is cellular respiration in the body important?

Answer 2

• occurs in cells to provides energy for cell functions

Question 3

WHY AND HOW gas concentrations regulated in the body?

Answer 3

WHY - CELLULAR RESPIRATION
cells need a continuous supply of O2 and removal of CO2
- therefore it is crucial that the levels of these gases in the body are regulated

RESPIRATORY SYSTEM

• responsible for taking in O2 and excreting co2 from the body
• via lungs which exchange the materials
• changes in breathing change the amount of oxygen taken in and the amount of carbon dioxide excreted

CIRCULATORY SYSTEM

• Carries oxygen from the lungs to the cells, where it is used.
• Takes away the carbon dioxide produced and delivers it to the lungs for excretion from the body.

Question 4

What muscles control breathing?

Answer 4

1. DIAPHRAGM - a muscle that separates the thorax from the abdomen
   - STIMULATED by impulses from the PHRENIC NERVE
2. INTERCOSTAL MUSCLES - muscles between the ribs
   - STIMULATED by the impulses from the INTERCOSTAL NERVES

*these are SKELETAL MUSCLES and REQUIRE STIMULATION from NERVE IMPULSES to INITIATE CONTRACTION

** these SPINAL NERVES have their ORIGIN in the SPINAL CORD at the LEVEL of the NECK AND THORAX (THORACIC REGION)

Question 5

What controls the muscle contractions for breathing?

Answer 5

nerve impulses that travel to the diaphragm and intercostal muscles are CONTROLLED BY THE RESPIRATORY CENTRE LOCATED IN THE MEDULLA OBLONGATA OF THE BRAIN.

2 REGIONS within the respiratory centre

• 1. one that controls expiration (breathing out)
• 2. one that controls inspiration (breathing in)

TO COORDINATE BREATHING, MESSAGES NEED TO PASS BACK AND FORTH BETWEEN THE NEURONS IN THESE 2 REGIONS.

Question 6

What are the two types of chemoreceptors? AND WHAT DO THEY DO?

Answer 6

1. PERIPHERAL CHEMORECEPTOR
2. CENTRAL CHEMORECEPTOR

WHEN THEY ARE STIMULATED, THEY END NERVE IMPULSES TO THE AREA OF THE RESPIRATORY CENTRE THAT REGULATES BREATHING.

Question 7

EXPLAIN peripheral chemoreceptors

Answer 7

they are GROUPS OF CELLS WITHIN THE WALLS OF THE AORTA AND CAROTID ARTERIES

SENSITIVE TO CHANGES IN THE CONCENTRATION OF O2, CO2, H IONS IN THE BLOOD PLASMA.

known as AORTIC AND CAROTID BODIES

Question 8

EXPLAIN central chemoreceptors

Answer 8

LOCATED IN THE MEDULLA OBLONGATA

- SENSITIVE TO CHANGES IN CONCENTRATION OF CO2, in the BLOOD and H ions in the CSF.

Question 9

Explain the concentration of oxygen levels affects breathing rate?

Answer 9

1. AS O2 CONSUMED BY CELLS
2. O2 concentration in Blood begins to FALL
3. O2 concentration falls below normal, while other factors are held constant, BREATHING RATE INCREASES

Question 10

WHY under normal conditions/circumstances, oxygen plays little part in the regulation of breathing?

Answer 10

within the NORMAL RANGE of blood O2 CONT.
- the EFFECT IS ON BREATHING RATE IS ONLY SLIGHT.

CONCENTRATION HAS TO FALL to VERY LOW LEVELS BEFORE MAJOR STIMULATORY EFFECT.

Thus under normal conditions/circumstances, oxygen plays little part in the regulation of breathing.

Question 11

What happens when there is a large decrease in oxygen levels in the blood?

Answer 11

1. LARGE DECREASE in OXYGEN concentration STIMULATES PERIPHERAL CHEORECEPTORS,
2. and the nerve impulses stimulate the transmission of messages to the diaphragm and intercostal muscles
3. and so the breathing RATE AND DEPTH INCREASES.

Question 12

What chemicals have some effect on the regulation of breathing activity?

Answer 12

O2, CO2, H ions

1. O2 and CO2 are carried in the blood and their concentrations affect the breathing rate and depth
2. CONCENTRATION of the CO2 in the BLOOD PLASMA affects the CONCENTRATION OF HYDROGEN IONS
3. CO2 DISSOLVES in WATER
4. FORMS CARBONIC ACID, which breaks down regularly to form HYDROGEN IONS and BICARBONATE IONS

CO2 + H2O H2CO3
H2CO3 H+ + HCO3 -

Question 13

Explain the concentration of CO2 levels affects breathing rate?

Answer 13

A relatively small increase in the concentration of CO2 is enough to cause a marked increase in the rate and depth of breathing.

1. Any increase in CO2 results in an associated increase in H ion concentrations.
2. increase in both concentrations in blood stimulates the CENTRAL AND PERIPHERAL CHEMORECEPTORS.
3. these, in turn, TRANSMIT NERVE IMPULSES to the RESPIRATORY CENTRE
4. Resulting in the INCREASE IN BREATHING RATE AND DEPTH
5. Immediate increase in breathing rate that occurs following an increase in the CO2 CONT. of the plasma is produced by the stimulation of the AORTIC and CAROTID BODIES.

Question 14

EXPLAIN Chemoreceptors MOST SENSITIVE TO CO2 IN PLASMA (LOCATION AND RESPONSIBILITY)

Answer 14

LOCATED IN MEDULLA OBLONGATA.

ARE RESPONSIBLE FOR 70-80% OF THE INCREASE in BREATHING RATE THAT RESULTS FROM AN INCREASE IN CO2 CONT. IN BLOOD

HOWEVER, THIS RESPONSE TAKES SEVERAL MINUTES.

Question 15

Explain the concentration of H IONS levels affects breathing rate?

Answer 15

1. H ion concentration of blood increases, pH INCREASES
2. A decrease in the pH directly stimulates chemoreceptors in the AORTIC AND CAROTID BODIES
3. Which then TRANSMIT IMPULSES TO THE RESPIRATORY CENTRE
4. resulting in an INCREASE IN BREATHING RATE AND DEPTH

Question 16

HOW THE 3 FACTORS CONCENTRATIONS AFFECT BREATHING TOGETHER

Answer 16

NONE OF THE 3 FACTORS (CO2, O2, AND H ION) CONCENTRATION IS INDEPENDENT IN THE REGULATION OF BREATHING RATE.

• Each factor interacts with each other

other factors affecting breathing rate is true

sensitivity of some factors, eg O2, is generally not as great as the sensitivity of others, eg CO2

Question 17

DRAW THE NEGATIVE FEEDBACK IN PG 141.

Answer 17

NEGATIVE FEEDBACK CONTROL OF BREATHING RATE THROUGH CHANGES IN THE CONT. OF CO2 AND pH OF BLOOD PLASMA.
*** FIG. 6.12

Question 18

EXPLAIN Voluntary control of breathing

Answer 18

• control comes via connections from the CEREBRAL CORTEX TO DESCENDING TRACTS IN THE SPINAL CORD.

VOLUNTARY CONTROL THUS BYPASSES THE RESPIRATORY CENTRE IN THE MEDULLA OBLONGATA.

• THIS IS A PROTECTIVE DEVICE AS IT ENABLES US TO PREVENT IRRITATING GASES AND WATER FROM ENTERING THE LUNGS

Question 19

EXPLAIN THE PROCESS OF VOLUNTARY BREATHING

Answer 19

DIAGRAM

Question 20

EXPLAIN HOLDING BREATH

Answer 20

possible to hold breath, however, cannot die from it

the build-up of carbon dioxide in the plasma stimulates the inspiratory centre to send impulses to the inspiratory muscles.

eventually forced to take a breath whether we want to or not.

Question 21

What happens to the concentration and exchange of gases during exercise?

Answer 21

during exercise, the contracting muscle cells require large amounts of oxygen and produce large amounts of CO2

In responding to this INCREASED DEMAND FOR GAS EXCHANGE, THE RESPIRATORY SYSTEM INCREASES BOTH THE RATE AND DEPTH OF BREATHING.

During heavy exercise, VOLUME OF AIR GOING INTO AND OUT OF LUNGS, EACH MINUTE MAY INCREASE 10-20 FOLD.

SAME FACTORS THAT INFLUENCE BREATHING AT REST APPEAR TO BE INVOLVED IN THIS INCREASE - LESSER EXTENT O2.

Question 22

DEFINE HYPERVENTILATION:

Answer 22

EXTREMELY RAPID OR DEEP BREATHING; DUE TO LOSS OF CO2 FROM THE BLOOD
- rapid, deep breathing can provide more oxygen than required and remove more carbon dioxide than necessary

MUCH FASTER AND DEEPER

‘OVERBREATHING’

MANIFESTS ITSELF IN ATTACKS

Question 23

EXPLAIN HYPERVENTILATION

Answer 23

CAUSES

• can occur voluntarily or may be stimulated by physical stress such as
• TENSION, EXTREME ANXIETY, EMOTIONAL STRESS
• HIGH ALTITUDES
• STRENUOUS WORK,
• PHYSICAL INJURIES - SEVERE PAIN
• POISONING
• PANIC
• LACK OF SLEEP

CONTROLLING/TREATMENT

• usually corrects itself because of the reduction in CO2 cont. means that the chemoreceptors are not stimulated, reducing the rate of and depth of breathing until CO2 LEVELS RETURN TO NORMAL
• CONTROLLING BREATHING, IN AND OUR OF PAPER BAG
• BREATHING THERAPY IF CHRONIC OR BOTHERING DAILY LIFE

SYMPTOMS

• tingling in mouth or hand
• frightening feeling
• not getting any air feeling
• dizziness
• nausea
• chest/abdominal pain
• rapid inhalation - O2 amount increases
• LOW Levels of CO2 - rapid breathing

Question 24

WHEN IS HYPERVENTILATION DANGEROUS?

Answer 24

DANGEROUS PRACTICE TO HYPERVENTILATE BEFORE SWIMMING.

• DOES ALLOW PEOPLE TO STAY UNDERWATER LONGER, NOT BECAUSE OF EXTRA OXYGEN IN THE BLOOD: IT IS DUE TO THE LOSS OF CO2.
• THE BREATHE HOLD-ABILITYCOULD BE INCREASED TO SUCH AN EXTENT THAT THE INDIVIDUAL LOSES CONSCIOUSNESS FROM LACK OF O2 TO THE BRAIN BEFORE FEELING THE URGE TO BREATHE.

MAY DROWNING DEATHS IN AUS HAVE BEEN DIRECT RESULT OF HYPERVENTILATION.