Human Physiology Week 4 - Cardiovascular (Transcripts Pt. 1)

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Questions and Answers

What is the primary purpose of ATP in the body?

To increase muscle size

To store fat for energy

To facilitate nerve conduction and transport (correct)

To regulate body temperature

How does basal metabolic rate (BMR) relate to energy expenditure?

It represents the total energy consumed from food intake.

It indicates energy used only during physical activity.

It is the energy required to maintain basic physiological functions at rest. (correct)

It fluctuates significantly based on daily exercise.

What percentage of daily energy expenditure is typically due to purposeful physical activity?

10%

75%

25% (correct)

50%

Which of the following factors is NOT mentioned as affecting metabolic rate?

Age Signup and view all the answers

What role does the thermic effect of food have in energy expenditure?

It contributes to about 8% of daily energy expenditure. Signup and view all the answers

What is the definition of one calorie?

The amount of energy required to raise 1 gram of water by 1 degree Celsius. Signup and view all the answers

What unit is typically used to measure the energy content of food?

Kilo calorie Signup and view all the answers

What happens during the breakdown of ATP?

Heat is released along with ADP and inorganic phosphate. Signup and view all the answers

How does the body maintain a temperature warmer than the environment?

By breaking down ATP and releasing heat. Signup and view all the answers

What is indicated by the measurement of calories in terms of metabolism?

The heat produced as a byproduct of metabolic processes. Signup and view all the answers

What primarily affects an individual's metabolic rate?

Body size and surface area Signup and view all the answers

Which method is considered the gold standard for accurately measuring core body temperature?

Esophageal probe Signup and view all the answers

How does body temperature vary throughout the day?

It fluctuates due to various factors and activities. Signup and view all the answers

What could influence the accuracy of an oral thermometer reading?

Food or drink consumed prior to measurement Signup and view all the answers

What is a significant limitation of using an infrared thermometer?

It measures skin temperature, not core temperature. Signup and view all the answers

What primarily causes the increase in body temperature during exercise?

Enhanced metabolism and breakdown of ATP Signup and view all the answers

What role do pyrogens play in the phenomenon of fever?

They stimulate the hypothalamus to increase the body's temperature set point Signup and view all the answers

Which of the following factors contributes least to heat generation in the body at rest?

Thermal radiation from skin surface Signup and view all the answers

How does the hypothalamus function during a fever?

It adjusts the set point for body temperature regulation Signup and view all the answers

Which mechanism primarily accounts for thermogenesis during physical exercise?

Increased friction from contracting muscles and ATP breakdown Signup and view all the answers

What role do pyrogens serve in the body during an infection?

They tell the hypothalamus to raise the body's temperature. Signup and view all the answers

How does the body primarily increase heat production during a fever?

Through enhanced muscle contraction during shivering. Signup and view all the answers

What physiological response helps reduce heat loss during a fever?

Vasoconstriction of blood vessels to the skin. Signup and view all the answers

What occurs when the hypothalamus resets the body temperature set point during a fever?

The body feels cold even though the temperature is elevated. Signup and view all the answers

What happens when the pyrogens in the body are eliminated during an infection?

The hypothalamus lowers the temperature set point back to normal. Signup and view all the answers

What is the first chamber of the heart that blood enters after coming from the vena cava?

Right atrium Signup and view all the answers

Which valve is located between the left atrium and the left ventricle?

Mitral valve Signup and view all the answers

What characterizes the syncytium in the atria of the heart?

It allows electrical signals to pass easily between interconnected cells. Signup and view all the answers

What is the role of the fibrous insulator located between the atria and ventricles?

To keep the electrical activity of the atria separate from the ventricles. Signup and view all the answers

During which phase do the atrioventricular valves, such as the tricuspid and mitral valves, open to allow blood flow from the atria to the ventricles?

Diastole Signup and view all the answers

What physiological mechanism does the body employ to cool down during a fever?

Sweating and increased breathing rate Signup and view all the answers

What is the critical temperature at which proteins in the body begin to denature?

106.5 degrees Fahrenheit Signup and view all the answers

What happens to proteins in the body when they denature?

They undergo irreversible structural changes Signup and view all the answers

Why is fever considered a normal physiological response?

It aims to eliminate foreign invaders like bacteria and viruses Signup and view all the answers

What is the main focus of understanding cardiovascular physiology in physical therapy?

To manage risks and prescribe exercise for various patient populations Signup and view all the answers

What happens to the cardiac valves during systole?

They close tightly to prevent blood from flowing back into the atria. Signup and view all the answers

What role do the chordae tendineae play in the function of heart valves?

They anchor the valves in place to prevent backflow of blood. Signup and view all the answers

Which feature distinguishes cardiac muscle from skeletal muscle?

Cardiac muscle is striated and contains branching structures. Signup and view all the answers

What is the significance of intercalated discs in cardiac muscle?

They facilitate the quick transmission of electrical signals between cells. Signup and view all the answers

What percentage of blood flow at rest is directed to the brain?

15% Signup and view all the answers

Study Notes

Metabolism and Energy

Calorie: Amount of energy required to raise temperature of 1 gram (or 1 mL) of water by 1°C; serves as a measurement of heat.
Kilocalorie (kcal): Common unit for measuring food energy content and human energy expenditure, often referenced in exercise contexts.
ATP Breakdown: Hydrolysis of ATP to ADP and inorganic phosphate releases heat, contributing to body temperature.

Basal Metabolic Rate (BMR)

BMR: The number of calories needed to maintain normal physiological functions at rest, crucial for homeostasis.
A significant portion of BMR occurs during sleep, highlighting metabolic activity during rest.
Average energy expenditure for a typical individual is around 2000 calories daily, with 25% from basal metabolism when awake.

Energy Expenditure Components

Purposeful Physical Activity: Accounts for approximately 25% of total energy expenditure.
Non-Exercise Activity: Daily activities such as walking, cooking, and errands contribute about 10%.
Thermic Effect of Food: Digesting food requires energy, accounting for roughly 8% of daily energy expenditure.

Factors Influencing Metabolic Rate

Exercise and physical activity significantly boost metabolic rate.
Protein consumption raises metabolic rate due to higher energy demands for digestion.
Body composition: More muscle mass correlates with a higher metabolic rate due to increased energy maintenance demands.

Body Temperature and Thermoregulation

Normal body temperature averages between 97°F to 99°F (36.1°C to 37.2°C), varying among individuals and throughout the day.
Core temperature is best measured with internal probes or rectal thermometers, significantly more accurate than oral or skin measures.
Thermogenesis: Heat production occurs mainly from ATP breakdown and friction during muscle contractions and blood circulation.

Fever Dynamics

Fever: A physiological response that elevates body temperature by resetting the hypothalamic thermostat.
Pyrogens: Molecules, either endogenous or exogenous, trigger the hypothalamus to increase the body’s temperature set point, leading to increased metabolic activity and heat production during infections.### Pyrogens and Fever Mechanism
Pyrogens are molecules that signal the hypothalamus to raise the body's temperature set point, initiating a fever.
Endogenous pyrogens originate from the immune system, often cytokines, that indicate the need for increased body temperature.
Exogenous pyrogens are molecules from external infectious agents, such as bacterial lipopolysaccharides or endotoxins, prompting an increase in temperature.
By raising body temperature above the normal range (97-99°F), the immune system aims to hinder pathogen survival and enhance its ability to combat infections.

Hypothalamic Response to Infection

Upon detection of pyrogens, the hypothalamus adjusts the body's temperature set point, often to around 102°F.
The shivering response occurs as the body interprets the increased set point while still at a lower temperature, causing sensations of cold and chills.
Shivering generates heat through muscle contractions, increasing ATP consumption and subsequently heat production.
The hypothalamus also promotes the release of hormones like thyroid hormone, increasing metabolic activity in cells, further contributing to heat generation.

Mechanisms for Temperature Increase

Vasoconstriction of blood vessels in the skin occurs to minimize heat loss, restricting blood flow and reducing temperature exchange with the environment.
The body actively works to maintain the newly established temperature by reducing sweat production and increasing muscle contractions to retain heat.

Fever Resolution

Once the infection resolves, pyrogen levels decrease, prompting the hypothalamus to lower the temperature set point back to normal (98°F).
As the body remains at a higher temperature while the set point drops, individuals may experience feelings of heat and initiate cooling mechanisms like sweating and increased breathing rates.
Normal regulation of body temperature resumes through vasodilation and sweating to expel excess heat.

Physiological Effects of High Fever

Fever is a natural physiological response to infection designed to eliminate pathogens.
Excessively high fever (>106.5°F) poses a risk, leading to protein denaturation and cellular damage that are irreversible.
Interventions are often advised when fever is around 103.5°F, to prevent reaching dangerous temperature levels.
Analogous to cooking an egg, proteins undergo irreversible changes when exposed to high temperatures, indicating potential harm to body functions.

Cardiovascular Physiology Overview

The cardiovascular system comprises two main components: the cardiac (heart) part and the vascular (blood vessels) part.
Understanding cardiovascular physiology is crucial for managing patient care and exercise prescriptions in various health conditions.
All patients have cardiovascular systems, highlighting the importance of physiology in evaluating health regimen applicability.

Heart Anatomy and Blood Flow

Blood from the body enters the heart through the vena cava into the right atrium, passing through the tricuspid valve to the right ventricle.
Blood is then pumped through the pulmonary valve into the pulmonary arteries to the lungs for oxygenation.
Oxygenated blood returns to the heart via the pulmonary veins into the left atrium, passing through the mitral valve into the left ventricle.
The aortic valve regulates blood flow from the left ventricle into the aorta, distributing oxygen-rich blood throughout the body.

Electrical Activity in the Heart

The right and left atria work as a syncytium, allowing for coordinated electrical activity crucial for heart function.
A fibrous insulator separates atrial and ventricular electrical activity, ensuring that atria contract before ventricles, aiding in effective blood pumping.
Valves in the heart prevent backflow, maintained by chordae tendineae that anchor the valves to cardiac muscles, vital in maintaining proper circulation during contractions.

Cardiac Muscle Structure

Cardiac muscle exhibits striations similar to skeletal muscle, resulting from the arrangement of actin and myosin filaments.
Muscular organization allows for efficient contraction and blood flow regulation, essential for sustaining cardiac function.

These notes summarize key concepts regarding pyrogens, fever mechanisms, cardiovascular physiology, and heart anatomy, providing a foundational understanding important in health sciences and therapy practices.### Cardiac Muscle Characteristics

Cardiac muscle is characterized by its branching structure, unlike skeletal muscle.
Intercalated discs are specialized structures within cardiac muscle that facilitate ion movement and electrical coupling between cells.
These low-resistance areas enable the rapid transmission of action potentials throughout the cardiac muscle, promoting synchronized contractions.

Blood Flow Through the Heart

Blood flows from the left atrium through the mitral valve into the left ventricle during diastole, especially when atrial pressure is high.
The left atrium contracts at the end of diastole to push remaining blood into the ventricle.
During ventricular systole, pressure in the ventricle rises until it exceeds diastolic pressure in the aorta, causing the aortic valve to open, allowing blood to enter the aorta.

Blood Distribution in the Body

At rest, approximately 15% of blood flow is directed to the brain, critical for neurological function.
Around 5% of blood flow at rest goes to the coronary arteries, necessary for supplying cardiac muscle with oxygen and nutrients.
The kidneys receive about 25% of resting blood flow, playing a crucial role in regulating blood pressure and filtering blood.
The gastrointestinal tract also receives approximately 25% of blood flow at rest, influenced by digestion and physical activity.
Skeletal muscle receives about 25% of blood flow while at rest, with this amount increasing during exercise.
Only around 5% of blood flow is allocated to the skin, varying according to environmental temperature.

Cardiac Cycle Overview

The cardiac cycle includes systole (contraction) and diastole (relaxation) phases, crucial for understanding heart function.
The electrocardiogram (ECG) records heart electrical activity, showing distinct waves representing atrial and ventricular depolarization and repolarization.
Ventricular volumes range from 50 mL (end systolic volume) to 130 mL (end diastolic volume), indicating heart filling and emptying phases.

Ventricular Pressure Changes

Ventricular pressure drops to zero during diastole and rises during systole, reaching about 120 mmHg during contraction.
The isovolumic contraction phase occurs when ventricular pressure builds up before the aortic valve opens, keeping blood volume unchanged.
As blood is ejected from the ventricle, pressure decreases until it drops below the aortic pressure, leading to aortic valve closure and the end of systole.

Atrial Contribution to Ventricular Filling

Atrial systole occurs at the end of diastole, where the atria contract to push additional blood into the ventricles, maximizing filling volume.
The beginning of ventricular pressure rise corresponds with ventricular depolarization, depicted by the QRS complex on the ECG.

Summary of Heart Function

The efficient coordination of electrical signals and pressure changes during the cardiac cycle ensures optimal blood circulation throughout the body.
Understanding the flow of blood, the function of heart valves, and the relationship between pressure and volume is key to comprehending cardiac physiology and cardiovascular health.

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This quiz explores key concepts related to metabolic rate and energy production through metabolism. It includes definitions of terms such as calorie and discusses the significance of these concepts in understanding energy balance. Test your knowledge on this fundamental aspect of biology!