Circulatory responses to exercise

In general, what is the function of the circulatory system?

Delivery of oxygenated blood and nutrients to tissues in accordance with their needs

In general, what is the function of the respiratory system?

Adding oxygen to the blood and removing carbon dioxide.

To meet the increased oxygen demand, what adjustments to blood flow must be made?

Increased cardiac output and blood flow redistribution

The right side of the heart pumps blood through the _______ circulation

Pulmonary

The left side of the heart pumps blood to the ________ circulation

Systemic

Define functional syncytium

The intercalated disks in cardiac fibres cause all heart fibres to exite and contract as a unit when one fibre is excited

What fibre type is cardiac fibre similar to? How is it similar? What is an important distinction?

Type I. Highly aerobic and contain large number of mitochondria. Cardiac muscle contains many more mitochondria than type I, slow skeletal muscle fibres.

What is the function of satellite cells?

Provide skeletal muscle with the ability to regenerate (recover) from injury. Heart muscle fibres do not have so heart muscle cells have limited regeneration capacity.

How is blood pressure regulated short term?

Baroreceptors in the carotid artery and aorta sense changes in arterial blood pressure. Signal is sent to cardiovascular control centre (medulla oblongata) and responds by decreasing sympathetic activity

A decrease in parasympathetic tone causes heart rate to

increase

An increase in parasympathetic activity causes heart rate to

decrease

“When stimulated, these nerve endings (vagus nerve) release acetylcholine, which causes a decrease in the activity of both the SA and AV nodes due to hyperpolarization.” What does this mean? What happens to heart rate?

The resting membrane potential is moved further from the threshold, resulting in a reduction of heart rate. Parasympathetic acts as a braking system to slow down heart rate

What is the cause of the the initial increase in heart rate during low intensity exercise?

Withdrawal of parasympathetic tone

At rest, a normal balance between parasympathetic tone and sympathetic activity to the heart is maintained by the _______.

cardiovascular control centre in the medulla oblongata

Define heart rate variability

variation in time between heartbeats

How can aging or disease influence heart rate variability?

Decrease in parasympathetic tone at rest or an increase in sympathetic nervous system outflow; creates disturbance in sympathovagal balance

What factors regulate venous return?

1) vasoconstriction 2) muscle pump 3) respiratory pump

How does venoconstriction drive venous return?

The decrease in diameter drives the blood back toward the heart; occurs as a reflex sympathetic constriction of smooth muscle in veins draining skeletal muscle

How does the respiratory pump drive venous return?

The pressure whin the thorax decreases and abdominal pressure increases during inspiration

Stroke volume is regulated by:

EDV, cardiac contractility, cardiac afterload

Flow rate of blood through the vascular system is ________ to the pressure difference across the system

proportional

The flow rate of blood through the vascular system is ________ to the resistance

inversely proportional

What is the most important factor contributing to the resistance of blood flow?

radius of the vessel

How much of our cardiac output is directed toward skeletal muscle at rest?

15% to 20%

How much of our cardiac output is directed to our skeletal muscle during maximal exercise?

80% to 85%

Arterioles in skeletal muscle have a ____ vascular resistance at rest

high

Define autoregulation

The increase in muscle blood flow during exercise begin regulated by several factors that promote vasodilation

What determines the need of blood flow to a muscle?

The intensity of exercise and the number of motor units recruited

What metabolites encourage sympatholysis?

Nitric oxide, prostaglandins, ATP, adenosine, endothelium-derived hyperpolarization factors

Heart rate and blood pressure are ____ during arm work when compared to leg work at a given oxygen intake

higher

How is the increase in cardiac output during incremental exercise achieved?

decrease in vascular resistance to flow and an increase in mean arterial blood pressure. elevation in MAP due to an increase in systolic pressure because diastolic pressure remains constant during incremental work

Exercise pressor feedback

Peripheral feedback to the cardiovascular control centre (medulla oblongata)