Distinguishing Sounds by Frequency Mechanism

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Questions and Answers

What is the characteristic of fluid particles trajectories at this point in a fluid?

Constant velocity

Parallel to tube walls

Chaotic without any order (correct)

Perpendicular to tube walls

What is the shape of the streamlines in laminar flow?

Parallel to the axis of the tube (correct)

Spiral

Circular

Perpendicular to the axis of the tube

What determines the flow rate of IV fluids according to Poiseuille's formula?

Radius to the fourth power (correct)

Radius to the fifth power

Radius to the third power

Radius to the second power

What is the function of skeleton muscles in blood circulation?

To promote blood circulation to the heart Signup and view all the answers

What is the main component that determines the resistance of the circulatory system?

Vessel diameter Signup and view all the answers

What is blood?

A suspension of blood cells in plasma Signup and view all the answers

What determines the importance of blood viscosity?

Physical characteristics of the blood Signup and view all the answers

What is the characteristic of the Basilar Membrane at the region closer to the oval window?

Narrower and stiffer Signup and view all the answers

What happens when a Low Frequency Sound reaches the Basilar Membrane?

It stimulates the nerve fibers at the apex Signup and view all the answers

What prevents the blood from moving in the opposite direction?

Vein valves Signup and view all the answers

Why does the inner ear require amplification of sound waves?

Due to the impedance difference between the Middle and Inner Ear Signup and view all the answers

What can extremely loud sounds like explosions cause to rupture?

The eardrum, ossicles, or basilar membrane Signup and view all the answers

What is the range of frequency to which the human acoustic organ is most sensitive?

2500-3000Hz Signup and view all the answers

What is the unit of Intensity or Energy Stream Density?

Watt/m2 Signup and view all the answers

What is the lower limit of intensity, also known as the Acoustic threshold?

10-12 w/m2 Signup and view all the answers

What can old age cause in the acoustic organ?

Blockage of blood supply, leading to cell death Signup and view all the answers

What is plasma composed of?

Water, dissolved salts, and hydrated molecules Signup and view all the answers

What is the main factor that determines blood viscosity?

Protein concentration in blood Signup and view all the answers

How does temperature affect blood viscosity?

It increases blood viscosity at high temperatures Signup and view all the answers

What happens to blood viscosity when hematocrit is high?

It increases by 10 fold Signup and view all the answers

What is the condition characterized by an increased percentage content of forming cells per blood volume unit?

Polycythemia Signup and view all the answers

What happens to blood viscosity in severe anemia?

It decreases twice Signup and view all the answers

What is the term for the percentage of blood cells in whole blood volume?

Hematocrit Signup and view all the answers

What is Thalassemia characterized by?

A lack of globin chains Signup and view all the answers

What determines the resistance of respiratory ways?

Internal friction force, friction forces between molecules and walls, and character of air flow Signup and view all the answers

What is the result of increased pressure difference to maintain flow in a turbulent airway?

Increased resistance Signup and view all the answers

What is the function of respiratory ways besides distribution?

Filtration and cleaning Signup and view all the answers

Which airway has a greater resistance?

Small airway Signup and view all the answers

What determines the tensility of the respiratory system?

The elasticity of lungs, chest wall, and alveoli Signup and view all the answers

What happens to the tensility of lungs with age increase?

It decreases Signup and view all the answers

What is the effect of emphysema on the tensility of lungs?

It increases Signup and view all the answers

What is the term for the ability of the respiratory system to change volume by the influence of pressure?

Tensility Signup and view all the answers

What happens to the pressure inside the pleural cavity when there is a disruption of pleural cavity isolation from the environment?

It becomes atmospheric Signup and view all the answers

Why does the lung collapse in an open pneumothorax?

Due to increased pressure in the pleural cavity Signup and view all the answers

What is the treatment for an open pneumothorax?

Sealing the open wound with an occlusive dressing Signup and view all the answers

What is the characteristic of the pressure inside the pleural cavity?

It is always sub-atmospheric Signup and view all the answers

What happens to the transpulmonary pressure in an open pneumothorax?

It becomes zero Signup and view all the answers

What is the relationship between the lung and chest walls in a normal individual?

They are pulled in opposite directions Signup and view all the answers

Study Notes

Mechanism of Distinguishing Sounds according to Frequency

The basilar membrane is narrower and stiffer at the region closer to the oval window, whereas it is wider and more flexible at the apex on the other side.
High frequency sounds cause movement of the stiffer part of the membrane closer to the oval window, stimulating the nerve fibers at that region.
Low frequency sounds cause the flexible region at the apex to oscillate, stimulating the nerve fibers at that part.

Significance of Impedance Difference between Middle and Inner Ear

The fluid-filled inner ear has much higher acoustic impedance than the air-filled middle ear.
The high acoustic impedance of the inner ear damps sound waves, requiring amplification to perceive the sound.

Causes and Mechanisms of Hearing Loss

Loud sounds can rupture the eardrum, break the ossicles, or rupture the basilar membrane.
Usual loud sounds can cause significant damage to hair cells and even the hair filaments that open ion channels.
Infections can rupture the eardrum (rare) and inner ear infections can damage hair cells.
Toxic drugs can enter hair cells through openings and poison or kill hair cells.
Old age can cause wear and tear on parts of the acoustic organ, leading to blockage of blood supply and cell death.

Intensity of Sound and Limits of Hearing and Pain

Intensity/Energy Stream Density is the stream of energy that propagates in a plane surface perpendicular to the direction of wave propagation, measured in Watts/m².
The human acoustic organ can perceive sound waves within a range of 10⁻¹² to 10⁻⁵ W/m².
The lower limit of intensity, I₀, is 10⁻¹² W/m², called the acoustic threshold.
At this threshold, fluid particles' trajectories are not parallel to tube walls, and velocity changes chaotically without any order.

Blood Flow and Circulation

The equation of Poiseuille's states that flow rate is proportional to the radius to the fourth power, meaning a small increase in the internal diameter of the cannula yields a significant increase in flow rate of IV fluids.
Laminar flow occurs when all elements of the fluid move in streamlines that are parallel to the axis of the tube, with velocity of fluid layers adjacent to the tube walls being minimal and maximal at the center of the tube.
Blood circulation is promoted by the contractile activity of skeleton muscles, breathing, and the existence of one-port valves.
Resistance is a force that opposes the flow of a fluid, determined by physical characteristics of the blood, vessel length, form, and diameter, and properties of vessel walls.

Physical Characteristics of Blood

Blood viscosity is a suspension of blood cells in plasma, with a viscosity of approximately 3.5 Pa sec at 37°C, determined by protein concentration and existence of suspended blood cells.
Blood viscosity depends on plasma viscosity, which is dependent on proteins concentration and temperature.
Hematocrit is the percentage of blood cells in whole blood, affecting blood viscosity, with high hematocrit increasing resistance and contributing to hypertension, and low hematocrit decreasing blood viscosity.

Turbulence and Resistance in Blood Flow

The degree of resistance depends on the diameter of the airway and whether flow is laminar or turbulent.
Laminar flow has less resistance than turbulent flow.
Larger airways are more prone to turbulent flow than smaller airways.

Airway Elasticity and Gas Flow

Airway elasticity is the size of elasticity of the respiratory system, determined by the tensility of lungs, chest wall, and alveoli.
Tensility is reduced with age and fibrosis, and increased with emphysema.
Changes in airway elasticity affect gas flow, with reduced elasticity leading to decreased gas flow and increased resistance.

Diseases and Conditions Affecting Airway Elasticity

Emphysema is a chronic non-specific disease of lungs, characterized by pathological extension of distal bronchioles with destructive-alveolar changes in alveolar walls, leading to increased lung elasticity.
Fibrosis is a condition characterized by decreased lung elasticity due to decrease in elastin content and increase in volume of collagen fibers.
Pneumo-thorax is a condition where the lung collapses due to increased pressure in the pleural cavity, requiring treatment to restore lung expansion.

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Description

Learn how the basilar membrane in the ear distinguishes between high and low frequency sounds, and how it stimulates nerve fibers accordingly.