Lab 5 Notes: Isopods, Earthworms, Rats & Organ Systems

Learning Objectives

Describe the direction of blood flow through the heart and vessels.
Palpate for pulse and identify 9 clinical locations to measure arterial pulse.
Define anastomosis and demonstrate arterial anastomoses in the hand.
Describe the function of hardware and software components used to acquire physiological data, including transducers, PowerLab, and LT.
Analyze an LT trace of breathing and heart rate; describe the relationship between breathing and heart rate.
Demonstrate and describe the effects of breath-holding on heart rate.
Acquire breathing and heart rate data using LT and analyze the effect of exercise on both.

Questions for Lab 5 Activities

How do you compare isopods, earthworms, and rats across the 3 organ systems (GI, Excretory, and Circulatory)?

1. Direction of Blood Flow in Veins

Blood in the veins travels toward the heart.
Systemic veins: carry deoxygenated blood from the body back to the heart.
- Venules → veins → superior/inferior vena cava → right atrium.
Pulmonary veins: carry oxygenated blood from the lungs to the heart.
- Blood flows from the lungs to the pulmonary veins to the left atrium of the heart.

2. Arterial Pulse Locations

Where in the arm can you feel the arterial pulse?
Where in the leg can you feel the arterial pulse?
Pressure changes as blood flows through blood vessels.
Pulse: pressure wave that can be felt in areas where the arteries are close to the surface.
- Systole (left ventricle contracts) generates a pressure wave into the aorta → aorta and arteries expand and recoil (pressure wave propagates through the body).
Palpation of the pulse detects both frequency (rate + rhythm) and amplitude (strength and quality) of the heart's contraction (heartbeat).
9 common places to take a pulse:
- Temporal artery, carotid, apical pulse, brachial, radial, femoral, popliteal artery, posterior tibial artery, pedal.

3. Recording and Visualizing the Pulse

Can we record and visualize the pulse?
Why might we want to use a tool to do so instead of palpating ourselves?
In general, why do scientists use tools for taking measurements?

4. Sampling Matters!

Aliasing: sampling produces a signal that does not resemble the analog signal.

5. Fingertip Pulse using PowerLab

Pulse wave amplitude = force of contraction.
Dicrotic notch: aortic valve closure.

Calculate Amplitude

Place a marker at the base of the pulse peak and a single handle at the top of the pulse peak and use pulse value provided by software.
$(beats \ per \ minute) / (60 \ seconds \ per \ minute)$

6. Radial and Ulnar Arteries

Is it necessary to have both the radial and ulnar arteries intact to maintain the viability of the tissues in the hand?
Either the ulnar or radial artery can be occluded and still allow for detection of pulse in the fingers.
However, if the brachial artery is occluded, there will be no distal pulses.

7. Breath Holding

How does holding your breath after inhaling and exhaling affect your breath rate?

How We Breathe:

Inhalation: thorax pressure is high, pressure in low, air flows in.
- Diaphragm contracts (moves downward and flattens), chest wall moves out (chest wall muscles contract and the thorax expands), thorax volume increases (expansion increases space in the chest cavity), pressure decreases (increase volume lowers the air pressure inside the lungs (below atmospheric pressure), air flows into the lungs (higher atmosphere pressure to lung pressure, air flows in).
Exhalation: thorax pressure is low, atmospheric pressure is high, air flows out.
- Diaphragm relaxes (moves upward), chest wall moves inward (thorax reduces in size as chest wall muscles relax), thorax volume decreases (reduces in space inside thorax), pressure increases (decrease in volume raises air pressure inside the lungs to greater than atmospheric pressure), air flows out of the lungs (higher lung pressure than atmospheric).

8. Relationship Between Breathing and Heart Rate

What is the relationship between breathing and heart rate?
How Does breath holding affect heart rate?
Diving reflex/mammalian dive response:
- Holding your breath will initially increase heart rate as $CO_2$ builds up in the blood and the body's chemoreceptors increase heart rate to maintain oxygen delivery to vital organs.
- Continuing to hold your breath activates the diving reflex and leads to bradycardia, to conserve oxygen for critical organs like the heart and brain by reducing the workload on the heart.

9. Exercise and Heart Rate

How does exercise affect heart rate and breathing rate?

10. Direction of Blood Flow

Systemic circulation → superior vena cava/ inferior vena cava → right atrium → right ventricle → pulmonary artery → lungs → pulmonary vein → left atrium → left ventricle → aorta
- Systemic circulation: returns deoxygenated blood to the heart.
- Superior/inferior vena cava: carries blood from the upper and lower body respectively.
- Pulmonary artery (carries deoxygenated blood to the lungs).
- Lungs: where blood is oxygenated.
- Pulmonary vein: carries oxygenated blood back to the heart.
- Aorta: distributes oxygenated blood to the body via systemic circulation.

11. False Statement About Veins and Arteries

Which is FALSE about veins and arteries?
- A. Arteries contain elastic tissue that allows the vessels to recoil once expanded - True: arteries contain elastic tissue that help them withstand and regulate pressure generated from the hearts pumping action (arteries are a pressure vessel).
- B. The muscular tissue in arterioles allows their diameter to be controlled. - True: true arterioles regulate blood flow by constricting or dilating using the smooth muscle in their walls.
- C. Veins contain valves that prevent backflow of blood as it returns to the heart - True: valves in veins ensure unidirectional blood flow.
- D. Blood flows from capillaries to venules to veins and then back to the heart - True.
- E. Blood flows from capillaries to arterioles to small arteries to large arteries. - False: blood flows from capillaries to venules to veins then back to the heart (option D).

12. Lab Questions

Label with the correct definition:
- Order in which vessels carry blood away from and return to the heart:
  - Arteries: act as a high pressure reservoir.
  - Arterioles: high resistance vessels that regulate blood flow.
  - Capillaries: exchange gases, nutrients, and waste.
  - Venules: drain blood from the capillary bed.
  - Veins: contain valves to stop back flow of blood.
Imagine if you've just held your breath for as long as possible, what changes would you expect to see in your subsequent respiratory pattern immediately after you held your breath as compared to normal breathing?
- Would expect: faster breathing, deeper breathing.
- Would NOT expect: no change in breathing, shallower breathing, slower breathing.
During which phase of respiration can the breath be held longer, after inspiration, after expiration, or somewhere in the middle? Why?
- Breath can be held longer after inspiration compared to expiration because there are higher oxygen levels. The lungs are filled with oxygen that is available for the body to use during the holding period and allows the body to sustain cellular respiration for a longer period of time before the urge to breathe takes over.
- Subsequently, there are lower carbon dioxide levels during this time because they have been exhaled out prior to the inhale and hold. The urge to breathe is triggered by rising $CO<em>2$ levels so starting with lower levels of $CO</em>2$ allows for a longer hold.
- After expiration it is harder to hold your breath because there is less oxygen available for the lungs and bloodstream so the body uses its oxygen supply more quickly. Exhalation still leaves residual $CO<em>2$ in the bloodstream so it takes less time for $CO</em>2$ to build up and trigger the urge to breathe. Much smaller volume of gas left in the lungs after exhalation causes more rapid buildup of $CO_2$ .