Chapter 7 PE

Efficient cardiac circulatory system

A lower heart rate with an increased stroke volume, indicates an efficient circulatory system. An increase in stroke volume is due to a stronger ventricular contraction causing greater amounts of blood to be ejected. Heart rate is the most important factor in increase output during exercise. during sub maximal exercise, heart rate will increase until the oxygen demands of the activity have been met.

The energy substrates (PC, muscle glycogen, and intramuscular triglycerides.)

ATP is the immediate source of energy for all muscular contractions. When exercise begins, muscular contractions can be fuelled initially by the ATP stores in the muscles. The result of exercise is that there is a decrease in all fuel levels within the muscle. ATP, PC and muscle glycogen levels all decreases as does fats. Glycogen levels decrease more rapidly with endurance events compared to high intensity sprints.

Capillary lung diffusion

CO2 leaves the blood stream and enters the alveoli in the lungs to be breathed out. Oxygen leaves the alveoli and enters the blood stream via the capillaries.

Capillary Muscle diffusion

CO2 leaves the muscles and enters the bloodstream, oxygen leaves the bloodstream and enters the muscles. this also occurs at the heart.

Blood volume

During aerobic exercise, blood volumes decrease. The size of the decrease is depended on the intensity of the exercise, environment factors (such a temperature) and the level of hydration of the individual. Plasma volume decreases rapidly within the first five minutes of exercise but then stabilises

Blood pressure during exercise

During exercise such as running and swimming (bigger muscle groups) the blood vessels get bigger (vasodialate) to allow more blood to pass through at once, to meet the oxygen depends on the muscles. On the contrary strengthening exercises such as bicep curls would allow blood vessels to constrict (vasoconstriction).

Cardiovascular responses

During exercise the cardiovascular system needs to deliver greater amounts of oxygen to and energy substrates to the working muscles .

Venous return during exercise

During exercise venous return is increased by three mechanisms called, the muscular pump, respiratory pump and venoconstriction

Redistribution of blood flow

During exercise, blood is diverted from the body's organs to the working muscles so that those muscles receive the greatest percentage of cardiac output. Vasoconstriction occurs in the arterioles supplying the inactive areas of the body and vasodilatation occurs in the arterioles supplying the working muscles. Veins carry de-oxygenated blood back to the heart Arteries carry oxygen rich blood away from the heart

Respiratory pump

During inspiration, the diaphram increases abdominal pressure and veins in the thorax and abdomen are emptied towards the heart. Then during expiration, this process is reversed- the veins fill with blood ready to be emptied again. Venous return is promoted simply through breathing.

Ventilation

How much air is breathed out in one minute.

Tidal volume?`

How much air is inspired or expired in one breath.

Acute muscular responses to exercise

In order for exercise to begin, the muscular contractions responsible for movement need to increase. The type of contraction, the force and the speed of contraction are controlled by the central nervous system (CNS).

Acute responses in respiratory responses

Increased tidal volume increased Respiratory rate Increase ventilation Increased diffusion

Ventilation during exercise..

Increases immediately before exercise due to the anticipation of exercise that is about to be done (O2 to working muscles). An increase in ventilation is a result of an increase in tidal volume and/ or respiration rate. At submaximal exercise this increases rapidly in the first 4-5 minutes then slowly plateaus. Due to a reached steady state. At maximal, this increases until the activity is over, no plateau.

Lactate

Lactate Lactate is a component of Lactic Acid - a by-product of anaerobic Glycolysis. This is produced until oxygen supply meets oxygen demand. During sub-maximal levels, lactate levels increase rapidly, and then tapers off. During maximal activity, Lactate levels will rise and rise, until the body can no longer remove it as fast its being produced, at which point the Lactate Inflection Point is reached (LIP). Key Terms: Oxygen deficit: the lack of oxygen in the body at the beginning of exercise Oxygen debt: the "paying back" of oxygen at the conclusion of exercise - usually matches or is more than oxygen deficit

Increased blood flow

More blood is delivered to the skeletal muscles during exercise to meet the increased oxygen demands; this is a direct result of the redistribution of blood flow away from the organs to the working muscles. Skeletal capillaries open up and serve three main purposes. These are to: Allow for increases in total muscle blood flow Deliver large blood volume with minimal increase in blood flow velocity Increase the surface area to increase diffusion rates

Diffusion

Movement of molecules from an area of higher concentration to one of a lower concentration. Gas exchange occurs in the lungs at the alveolar capillary interface and in the muscle at the tissue- capillary interface through diffusion.

Oxygen consumption (VO2) and arteriovenous oxygen difference (a-VO2 diff)

Oxygen consumption is the volume of oxygen that can be taken up and used by the body. As intensity of exercise increases, so does oxygen consumption. This increases the difference in oxygen concentration in the arteries compared with the veins (a-vO2 diff)

Systolic blood pressure

Pressure in the arteries following contraction of ventricles as blood is pumped out of the heart.

Diastolic blood pressure

Pressure in the arteries when heart relaxes and ventricles are full with blood.

Cardiac output equation

Q= = stroke volume x heart rate

Cardiac output

The amount of blood pumped out of the heart in one minute.

Venous return

The amount of blood that is returned to the heart with every heartbeat. it is important to note that for an increase in cardiac output to occur it has to be accompanied with an increase in venous return.

Heart Rate

The number of beats in one minute

Respiration rate

The number of breaths take in one minute.

Motor unit recuitment

The number of motor units being used increases with exercise particularly exercise intensity. The brain increases the number and strength of the messages sent to the motor units, to account for the required strength and speed of the muscular contraction.

Blood pressure `

The pressure exerted on the blood vessel walls by the blood, which increases during exercise. exercises using larger muscle groups affect the sysolic blood pressure more than the diastolic blood pressure.

Muscle pump:

The result of the mechanical pumping action caused by repetitive muscular contractions. When he muscles contract, the veins are squashed together and the blood in them is pushed forwards towards the heart. The vasodilation and contrition of the vessels creates a pump actions.

Diffusion during exercise

This increases so greater amounts of oxygen and CO2 can be exchanged at the avoli and the muscles. allowing for greater amounts of oxygen at the muscles and more CO2 being removed.

Respiration responses

This is responsible for the delivery of oxygen to, and the removal of CO2 from the cells of the body.

Formula for ventilation

V (litres per minutes)= TV x RR

Venoconstriction

Venoconstriction is a reflex controlled by the central nervous system, and assists in venous return Venoconstriction reduces the capacity of the venous system, forcing blood to be pushed out towards the heart.

Definitions

Ventilation (V): How much air is breathed in or out in one minute Tidal Volume (TV): How much air is inspired or expired in one breath Respiratory Rate (RR): The number of breaths taken in one minute Plateau: To reach a period or level where no change is observed Ventilatory threshold: Point where ventilation is no longer increasing linearly with the increase in exercise intensity Diffusion: The movement of molecules from an area of higher concentration to one of lower concentration Cardiac output (Q): The amount of blood pumped out of the heart in one minute Stroke volume (SV): The amount of blood ejected by the left ventricle per beat Heart rate (HR): The number of times the heartbeats in one minute Systolic blood pressure: Pressure in the arteries following the contraction of the heart as blood is pumped out of the heart Diastolic blood pressure: Pressure in the arteries when the heart relaxes and ventricles fill with blood Vasoconstriction: The decrease in the diameter of a blood vessel Vasodilatation: An increase in the diameter of the blood vessel Arteriovenous oxygen difference (a-vO2 diff) Different in oxygen concentration in the arterioles compared with the venuoles Motor Unit: A motor neuron and the muscle fibres it stimulates Lactate inflection point (LIP): The exercise intensity beyond which lactate production exceeds removal, sometimes referred to as the lactate threshold

Body temperature

When exercise commences, there is an increase in the rate of metabolism required to produce ATP in the muscle. Heat is the by-product of the process of converting chemical energy (fuel) to mechanical energy (movement). An increase in the rate of reactions is accompanied by an increase in heat production, which causes body temperature to also increase. The body regulated this increase in body temperature through sweat and redistributing blood to the surface of the skin to let off heat.

Stroke volume

the amount of blood pumped out of the left ventricle of the heart per beat.