Take 2 minutes to build/design a system that does two things:

1.) Senses when is low or CO2 is high. Hint: how might you use oxygen to trigger excitation of a cell?

2.) Triggers increased rate of breathing.

Hint: model it after the baroreceptor reflex and everything you need for a homeostatic feedback loop

31 Step 1: we need a sensor.

32 Peripheral chemoreceptors monitor PO2, PCO2, pH

Video from: http://bk.psu.edu/clt/bisc4/ipweb/systems/buildframes.html?respiratory/conresp/01

3 Glomus cells are peripheral chemoreceptors which sense O2, CO2, pH

Blood vessel

Low PO 2

Low P O 2 K+ channels close This system responds Cell when PaO2 gets very depolarizes Glomus cell in carotid low (~60 mmHg) body

Ca2+ Relevant at high enters Voltage-gated Ca2+ altitudes or in chronic channel opens pulmonary disease Exocytosis of

Glomus cells also Receptor on respond to PaCO2 Action potential Increase in ventilation=faster

Signal to medullary breathing=more O2 centers to increase 4 ventilation in, more CO2 out Central chemoreceptors in brain monitor PCO2

Video from: http://bk.psu.edu/clt/bisc4/ipweb/systems/buildframes.html?respiratory/conresp/015 Sidenote: wait wait wait wait...... wait. CO2 is most important factor??

Remember changes in CO2 affect pH. Dangerous and deadly.

Remember also that hemoglobin has oxygen reserves

6 Step 2: send signal to integrating center

7 Peripheral chemoreceptors monitor PO2, PCO2, pH

Video from: http://bk.psu.edu/clt/bisc4/ipweb/systems/buildframes.html?respiratory/conresp/01

8 Step 3: have integrating center cause change in effectors

9 10 Figure 18.17 REVIEW: CHEMORECEPTOR RESPONSE Central Chemoreceptors Peripheral Chemoreceptors

+ Central chemoreceptors monitor CO2 in cerebrospinal fluid. Carotid and aortic chemoreceptors monitor CO2, O2, and H .

Plasma KEY PCO2 CA = carbonic anhydrase

Cerebral capillary

− Blood-brain CO2 H+ + HCO3 H+ barrier PCO2 (in plasma)

+ − CO2 + H2O H2CO3 H + HCO3 Cerebrospinal CA fluid Stimulates peripheral Plasma PO2 chemoreceptors <60 mm Hg in carotid and aortic bodies Central Medulla chemoreceptor oblongata at brain Respiratory Sensory control neurons centers

Ventilation

Plasma PO2 Negative feedback Plasma PCO2 11 Control of Respiration

Why/how can we breath when we sleep?

Why/how do we change rate/depth of breathing due to various internal or external stimuli?

Basic rhythm set by brainstem, and modified by input from sensory receptors and other regions of the brain

12 How do we regulate breathing? Gas Exchange and Transport Peripheral and central Part 1: Partial pressure gradients drive gas chemoreceptorsexchange. How/why does oxygen get into the monitor CO2 and O2 blood/tissues? levels and adjust breathing accordinglyPart 2: How are O2 and CO2 transported in the blood?

13 Some key points from past few days....

• Oxygen and transported in blood in multiple ways

• Many factors (pH, temperature, PCO2, PO2, BPG levels) affect saturation of hemoglobin

• Inspiratory center in medulla sets automatic breathing rhythm.

• Breathing rhythm modulated by changes in gas levels, pH, and some external stimuli

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