Bioscience: Unit 3

What is Cardiovascular System?

Closed loop system (blood keeps circulating in a cycle) consisting of the:

heart (muscular pump)

Vessels (tubes that carry blood)

Functions of Cardiovascular system

Transport oxygen and nutrients to tissues

Removes wastes from tissues

Helps regulate body temperature

R Atrium and R Ventricle (2/4 Chambers)

R Atrium: receives deoxygenated (used oxygen) blood from body and sends to right ventricle

R ventricle: pumps blood to the lungs to pick up oxygen

L Atrium and Ventricle (2/4 Chambers)

Left Atrium: pumps oxygenated blood delivered from lungs and sends to left ventricle

L ventricle: Pumps oxygenated blood to entire body

Right vs Left Atrioventricular valve (2/4 Valves)

Valves act like one way doors that prevent backflow (keep blood flowing in one direction)

Right Atrioventricular (AV) Valve

Prevents backflow of blood into right atrium when right ventricle contracts

Left Atrioventricular AV valve

Prevents backflow

of blood into left atrium when left ventricle contracts

Right vs Left Semilunar Valve (2/4 Valves)

Valves act like one way doors that prevent backflow (keep blood flowing in one direction)

Right Semilunar Valve

Prevents backflow of blood into right ventricle after its pumped to lungs

Left Semilunar Valve

Prevents backflow of blood into the left ventricle after pumped out to the body

Vena Cava (1/4 major vessels)

Brings deoxygenated blood coming from body to right atrium

Pulmonary Arteries (1/4 major vessels)

Carry deoxygenated blood from right ventricle to lungs to receive oxygen

Pulmonary Veins (1/4 major vessels)

Bring oxygenated blood from lungs to left atrium

Aorta (1/4 major vessels)

Carries oxygenated blood from left ventricle to entire body

Pulmonary circuit (1/2 loops blood travels through)

Carries deoxygenated blood from the heart to the lungs to pick up oxygen and back to the heart.

Systematic circuits (1/2 loops blood travels through)

Oxygenated blood goes from the heart → body tissues → returns deoxygenated blood to the heart

Veins

Return blood to heart, very low pressure, valves prevent backflow

Arteries

Thick muscular walls, carry blood away from heart, under high pressure

Capillaries

Smallest vessel in body, site of exchange of oxygen and nutrients

3 Walls of Heart (Endocardium, Myocardium, and Epicardium)

Endocardium

Protective inner lining of the chambers

Myocardium

Middle thickest layer. Muscular contraction that eject blood from heart chambers

Epicardium

Outer protective layer that serves as lubricative outer covering

Cardiac Cycle

Repeating cycle of contraction & relaxation

One cardiac cycle = 1 concentration & 1 relaxation

Ex: One full beat of the heart

Systole

Contraction Phase

Ejection of blood from ventricle

At rest, 40% of cardiac cycle spent in systole

Shorter time spent

Diastole

Relaxation Phase

Filling ventricle with blood

At rest, 60% of cardiac cycle spent in diastole

Longer time spent

Diastole Changes During Cardiac Cycle

Pressure in ventricles is low during filling,

volume increases (no contraction occurring)

"Lubb" (first sound at the end of diastole) - AV valves close

Systole Changes During Cardiac Cycle

Pressure in ventricles high during contraction, volume decreases during ejection (pumping)

"Dupp" ( sound at end of systole) - Semilunar valve closes

Stroke Volume (SV)

Amount of blood pumped out of the left ventricle per beat

Ex: Think of squeezing a ketchup packet once — that's one "beat" pushing out some ketchup, like one heartbeat pushing out blood

Average healthy volume = 60 mL

What is cardiac output & equation / role in exercise

Amount of blood pumped by heart per minute

Contracts slow

Involuntary

Q = SV x HR

Average healthy volume = 4800 mL

During exercise, cardiac output increases because your muscles need more oxygen. Your heart pumps more blood per minute by increasing heart rate and stroke volume.

Direction of blood flow through the chambers of the heart

Body → RA → RV → Lungs → LA → LV → Body

How are myocardial cells similar to skeletal muscle fibers?

They both contain sarcomeres, actin and myosin for contraction

End Diastolic Volume (EDV)

Amount of blood in the ventricle before it contracts

Happens at the end of diastole (after filling).

EDV = what you START with

End Systolic Volume (ESV)

Amount of blood left in the ventricle after it contracts

Happens at the end of systole (after pumping).

ESV = what you KEEP

Calculating Stroke Volume

EDV - ESV = SV

SV = What you pump out

Ejection Fraction Concept

The percentage of blood that is ejected (pumped out) is called the ejection fraction (EF)

Normally 50-60% at rest

Higher stroke volume does not mean better quality or strength of heart

Fraction for Ejection Problem + Example

( SV/EDV x 100)

EF = (60 ÷ 100) × 100

60%

typical EF range (50-70%)

Mean arterial pressure (MAP) + Equation

Average pressure in the arteries (not a simple average since diastole lasts longer than systole)

MAP = DBP+ 0.33 (SBP-DBP)

Factors that Influence Arterial Blood Pressure

Blood volume increases

Heart rate increases

stroke volume increases

Blood velocity increases

Peripheral resistance increases

What is the SA Node and Role as a Pacemaker

Collection of specialized cells at the top of the right atrium connected to all cardiac muscle cells

Spontaneously depolarize (sodium channels open) allows for entry of sodium and release of calcium

Starts electrical signal

This calcium is shared with all cardiac cells and allows for heart muscle to contract all over again

Depolarization of SA nodes occurs 100 times/min

Atrioventricular node (AV node)

Passes depolarization to ventricles

Brief delay to allow for ventricular filling

Bundle Branches vs Purkinje fibers

Bundle Branches

Carry signals down left and right ventricle

Purkinje fibers

Spreads signal throughout ventricles which allows for release of blood

SA node depolarization is regulated by what

Autonomic nervous system (ANS)

Stress- circulating epinephrine

Caffeine, drugs

Age

Parasympathetic NS: Difference in activation during rest and exercise conditions

Vagus nerve ("Brake nerve")

At rest: the parasympathetic nerve is stimulated, which decreases the intrinsic rate (The SA node naturally wanting to fire at 100 bpm)

During first part of exercise, heart rate increases over 100 bpm due to decrease in parasympathetic nerve stimulation

Sympathetic NS

Cardiac accelerator nerve

Makes SA nodes fire faster and release more calcium

SNS does not get involved until heart rises above 100bpm

Because below 100bpm the heart rate is mostly controlled by PNS until the PNS "is removed off the break and the SNS is able to push the gas pedal"

The increase in heart rate during exercise is completely due to a sympathetic nerve

Parasympethic nerve system must be eliminated first "foot off break"

2 step process

How are myocardial cells similar to skeletal muscle fibers?

Both contain sarcomeres, actin, and myosin for contraction

Contractility (1/3 factors that regulate stroke volume)

"How hard the heart squeezes"

Definition: Strength of the ventricular contraction (How hard the heart squeezes)

Ways Contractility can be increased (Frequency Effect)

Increased rate of depolarization by norepinephrine and epinephrine enhances the amount of calcium in myocardial cell allowing for a stronger heartbeat

Preload (pregaming) (1/3 factors that regulate stroke volume)

How Much blood fills the heart before it contracts

Definition: Volume of blood in the ventricles at the end of diastole (before ventricles contract)

Frank Starling Mechanism vs Venous Return

Venous return = how much blood comes back to the heart (more blood allows for more ejection)

Frank-Starling mechanism: how the heart responds to blood coming back to heart.

More blood = stretching the sarcomeres = More contraction = More blood ejected (higher SV)

How to increase venous return

Amount of blood returning to heart from veins

1). Venoconstriction

- Squeeze the veins

& pushes more blood back toward the heart

2). Skeletal muscle pump

- When muscles contract, they squeeze veins in one direction (blood is pushed toward the heart)

3). Respiratory Pump

Breathing increases abdominal pressure

This pushes blood from abdominal veins towards heart

Afterload (1/3 ways to increase stroke volume)

"How much the heart has to push to eject blood"

Definition

The resistance the heart has to push against to eject blood

Causes of Afterload

Higher BP = more resistance = harder to eject blood

Low BP = easier to eject blood (Higher SV)

What Increases Afterload?

Vasoconstriction

Narrowing of vessels

Increases blood pressure and reduces blood flow through the vessel.

High blood pressure

Increases resistance

Resistance Formula and Causes

(What makes it harder for blood to flow through blood vessel)

(Length x viscosity)/radius^4

Arterioles are small blood vessels that control blood flow to tissues. At rest, the sympathetic nervous system (SNS) makes them tighten which mantains blood pressure

Why does this resistance occur

At rest muscles don't need much blood

Blood is conserved for essential organs

Stroke volume increases

Blood Flow formula: BF = pressure/resistence

If resistance is high, blood flow is low

If resistance is low, blood flow is high

What is Vasodilation and why is important

(widening of blood cells-decrease resistence and increase blood flow) to skeletal muscle

Muscles need more oxygen during exercise

Decrease in SNS activity to arterioles leads to...

decreased afterload

Radius increases

Resistance decreases

increased ejection from ventricle (SV)

What happens to Heart Rate and Stroke Volume During Exercise (Athletic Individuals)

Increase in HR and SV: Cardiac output is increased and raised

However in untrained subjects SV does not increase beyond a workload of 40% VO2 max.

Cardiovascular Drift

if exercise duration is really long

Gradual decrease in stroke volume due to dehydration and reduced plasma volume

Gradual increase in heart rate to compensate

Fick Principle

Explains how much oxygen is actually used by body

Determined by

How much blood the heart pumps (cardiac output)

How much oxygen muscles take from that blood (a-vO₂ difference)

Venous blood (blood returning to the heat) has some oxygen during max exercise

The better muscles are at extracting oxygen out of blood the more oxygen body can use

Fick Equation

VO2 = Q × (a-vO2 difference) Explains what determines oxygen use

VO₂ = how much oxygen your muscles use

Q (cardiac output) = how much blood your heart pumps per minute

a-vO2 difference = the difference in oxygen content between arterial blood (going to muscles) and venous blood (coming back from heart)

a-vO2 Difference

Shows how much oxygen your muscles take from the blood.

At rest: Muscles use a little oxygen (e.g., 5 mL per 100 mL blood).

During exercise: Muscles use more oxygen (e.g., 10 mL per 100 mL blood).

Goal in exercise: A high a-vO2 difference is desired during exercise

Effects off Training on V02 max

Training helps body

Deliver more oxygen

Use more of oxygen delivered

V02 max is maximal amount of oxygen that can be utilized during exercise

Sets limit for how much energy can be made using oxygen

Short duration vs long duration in exercise

• Short duration: SV increase > a-vO2 increase (more of heart pumping more blood per beat)

• Long duration: a-vO2 increase > SV increase (muscles getting better at using oxygen)

Effect of Training on a-vO2 max

• Increased mitochondrial size and enzyme activity

• Increased capillary opening/formation

• Slowing blood flow so oxygen can move into muscle

• Reduces distance oxygen travels to mitochondria

Early Training vs Late Training

Early training: ↑ stroke volume → ↑ Q

Later training: ↑ a-vO₂diff

Genetics influence VO₂max potential

Ranges of VO2max Values (Percentage)

• 50% due to training

• 50% due to genetics

• Individuals vary ("low responders" vs "high responders")

Detraining and VO2max

• Stopping exercise causes Vo2 max to drop

Decreased stroke volume (heart pumps less blood)

Decreased a-vO2 difference (loss of mitochondria and capillaries)

Most important variable that determines resistance to blood flow and impacts afterload?

Vessel radius

Impact of exercise on CV variables & relationship with intensity

Q: increases with intensity

HR: increases linearly with intensity

SV: increases at low-moderate intensity, plateaus at higher intensities (untrained)

BP: systolic increases, diastolic remains same or slightly decreases

MAP: increases slightly

a-vO₂ difference: increases with intensity

How does an acute bout of endurance exercise impact the cardiovascular system in a inactive individual?

Increases heart rate, cardiac output, and blood flow to skeletal muscle.

Stroke volume increases at low-moderate intensity, then plateaus.

What are the primary biological bases for improvement in SV with endurance training?

Fluid Retention (increased plasma volume leading to increased preload

Which of the following is not a mechanism for increased venous return during exercise? (Increased stroke volume, skeletal muscle pump, respiratory pump, and vasoconstriction)

Increased stroke volume

Cardiorespiratory System

Heart and Vessels (Cardiovascular)

Circulate blood containing oxygen (and nutrients) to working tissue

Lungs

Supplies oxygen to the blood

Primary Function of the Respiratory System

1). Provides a mean of gas exchange between the environment and the body

- Ventilation: The mechanical process of moving air into and out of lungs

- Diffusion: Process by which oxygen moves out of lungs into the blood and CO2 moves from blood into lungs

2). Regulation of acid base balance during exercise

Major Organs of the Respiratory System

Group of passages that filter air and transport air to lungs:

Nose & Nasal Cavity

Pharynx: Throat

Larynx: Voice box

Trachea

Bronchial Tree & Alveoli

Lungs

Completely enclosed by two thin membranes collectively called the pleura (visceral & parietal)

2 layers are separated by intrapleural fluid

Primary function of pleura:

Support: tethers lungs to diaphragm and thoracic cavity

Protection: pleural surfaces slide past one another (decrease friction)

Functional Zone of Respiratory System

The passage of air through the lungs is divided into two functional zones (Conducting and Respiratory zone)

Alvelous

Small air sac at end of air passageways in lung site of gas exchange

Conducting Zone

1). Conducts (moves) air through the trachea, bronchi, bronchioles, and terminal bronchioles to the respiratory zone

2). Humidifies, warms, and filters the air (via mucus and macrophages)

No exchange of gases, lungs, and blood here

Respiratory Zone

Exchange of gases between lungs & blood occurs in alveoli of respiratory bronchioles and in alveolar sacs

Alveoli are those grape like clusters at the end of the bronchi

Ventilation

the mechanical process of moving air into and out of the lungs (breathing)

• Air moves into lungs due to the pressure gradient produced by contraction of respiratory muscles

Phrenic nerves

In brain project to the diaphragm and stimulate contraction several times per minute

Inhalation vs Excelation

Inhalation

Rib cage expands as muscles contracts

Diagram contracts (moves down)

Excelation

Rib cage becomes smaller as muscles relax

Diaphragm relaxes (moves up)

Why does air move into your lungs? (Inspiration vs Expiration)

Inspiration (Active)

Lowering the diaphragm expands the volume of the chest cavity, intrapulmonary pressure is decreases

Creates a "vacuum" allows air to flow into the bronchial passage

Expiration (Passive)

Diaphragm relaxes, elastic recoil of the alveoli raises the intrapulmonary pressure

Air is forced out of lunges

Fibrosis

Collagen buildup makes the lungs stiff, so they can’t expand well during inhalation, making it harder to pull air into the lungs.

Smoking, coal dust, genetics, lung infections

Emphysema

Emphysema destroys elastic tissue in the lungs, so they don’t recoil properly, trapping air and making it hard to exhale.

Smoking, genetics

Airflow Equation

Airflow = p1-p2 / Resistance

Airflow depends on pressure and how open the airways are.

Asthma vs Chronic Bronchitis

Asthma

Inflammation and narrowing of airways

Genetics and environmental factors

Chronic Bronchitis

Long term inflammation of the bronchi, causes mucus production

Lung volumes & capacities

They describe how much air is in the lungs and how much air can move in and out during breathing and exercise.

Ex:

Residual volume: air that always stays in lungs

Vital capacity: max air you can move in and out

Exercise: tidal volume increases (deeper breaths)

Pulmonary Ventilation & Tidal Volume Calculation

V = The amount (liters) of air moved in or out of the lungs per minute

Hows it calculated

V=Vt​×f

Vt (tidal volume): air per breath

f (breathing frequency): breaths per minute

Alveolar Ventilation vs Dead space ventilation

Alveolar Ventilation

Volume of "fresh air" that reaches the respiratory zone each minute (usually 0.35 L out of 0.5L)

Dead space ventilation

Not all air that passes the lips reaches the respiratory zone (remains in conducting zone) unused ventilation (0.15 L out of 0.5 L)

Inflammation = increases dead space ventilation

How many alveoli are estimated to exist in the lungs?

300 million alveoli in adult human lungs

Total Pressure of Air

Amount of pressure each gas contributes when mixed with other gases (like air)

Total pressure of air = 760mmHg (sea level)

Total pressure comes from all the gases in the air combined

Dalton's Law

The total pressure of a gas mixture is = to the sum of the pressure that each gas would exert independently

Each gas in air adds its own share share of pressure

Ex: Total pressure = oxygen pressure + nitrogen pressure

The partial pressure of oxygen (PO2)

Air contains 20.93% oxygen

Expressed as a fraction: 0.2093

PO2 = 0.293 x 760 = 159mmHg

This means that oxygen alone contributes 159 mmHg of the total air pressure

Partial Pressure of Gases

Pair = PO2+PCO2 + PN

The total pressure of air is the sum of each gas's partial pressure

Diffusion

Random movement of molecules from high to low concentration

Gases diffuse from high to low partial pressure

This is how oxygen moves from the lungs to the blood and muscles

Direction Lungs Move Oxygen & C02

Lungs = Pick up oxygen

Oxygen goes from lungs to blood

Co2 goes from blood to lungs

Direction Arteries Move Oxygen & C02

Transport (no exchange)

Oxygen stays in blood

C02 stays low

Direction Muscle Move Oxygen & C02

drop off oxygen

Oxygen goes from blood to muscle

Co2 goes from muscle to blood

Fick's Law of Diffusion

This explains what controls how fast gases move across tissues

Rate of gas transfer across tissues depend on

surface area

tissue thickness

diffusion coefficient,

partial pressure difference

Oxyhemoglobin

Approximately 99% of O2 is transported in the blood bound to hemoglobin (Hb)

- A protein found in red blood cells

Loading: Oxygen attaches to hemoglobin, this happens in lung capillaries (near alveoli)

Unloading / Offloading: Oxygen is released from hemoglobin, this happens in body tissues (like muscle)

Oxyhemoglobin Dissociation Curve

Purpose of curve: Shows how tightly hemoglobin holds oxygen at different pressure points

Flat portion of graph: illustrates unloading under rest conditions (100-75% = affinity of oxygen for Hb is high in lungs & arteries and only a small amount of oxygen is released to tissues at rest

Steep portion: small decreases in P02 causes large oxygen release. C02 can increase during exercise and can result in large increases in unloading (sensitive response)

Oxygen binding to Hb is reversible reaction (can attach or detach) and dependent on

dependent on

The P02 in the blood (high in lungs = oxygen binds and low = oxygen releases)

Other Factors: How strong hemoglobin holds oxygen

Other Factors that Alter the Hb Dissociation Curve (cause rightward shift)

pH

- More acidic leads to weaker bond

Oxygen released easier

Temperature

High temp = weaker o2 bond

More oxygen unloaded

Myoglobin

An oxygen binding protein in skeletal and cardiac muscle

moves oxygen from the cell membrane to mitochondria

Found mainly in in slower twitch I muscle fibers

Holds oxygen more tightly than hemoglobin

Releases only at very low P02