THE CARDIOVASCULAR SYSTEM

1
THE CARDIOVASCULAR SYSTEM
2
LEARNING OBJECTIVES

• Understand the interaction between the
  cardiovascular and respiratory systems
• Identify and describe the external and internal
  structures of the heart.
• Describe and explain the events of the cardiac
  cycle and how it is linked to the conduction
  system
• Know definitions and resting values for stroke
  volume, heart rate cardiac output.
• Describe and explain changes in heart rate,
  stroke volume and cardiac output during
  submaximal and maximal work
• Explain how changes in heart rate are regulated
  by neural, hormonal and intrinsic factors.
• Be able to represent graphically heart rate
  response to varying intensities of workload and
  during recovery.
• Describe and explain the distribution of cardiac
  output at rest and on exercise via the vascular
  shunt and vasomotor control centre
• Describe how carbon dioxide and oxygen are
  carried in the blood
• Describe the mechanisms of venous return
• Describe the effects of a warm up and cool down
  on the vascular system.

3
Cardiovascular and respiratory systems

• Aerobic exercise uses oxygen to supply the energy
  needed
• Three distinct systems work together to ensure
  oxygen is supplied to the working muscles during
  exercise
• These are the heart, vascular (blood vessels) and
  respiratory systems.

4
The Heart

• The heart is a double pump two separate pumps
  that work side by side
• The right side pumps deoxygenated blood to the
  lungs
• The left side pumps oxygenated blood to the rest
  of the body
• The heart consists of four chambers two upper
  atria and two lower ventricles
• The atrio-ventricular valves separate the atria
  and ventricles
• The semi-lunar valves are found in the pulmonary
  artery and aorta.
• Exercise 1 Exercise 2 Exercise 3

5
The cardiac cycleHow blood flows through the
heart

• Two phases systole contraction phase (atrial
  and ventricular) 0.3 secsdiastole relaxation
  phase 0.5 secs
• DIASTOLE
• atria fill with blood
• pressure rises
• atrioventricular valves open
• blood passes by gravity into ventricles
• semi lunar valves closed

• SYSTOLE
• Atrial systole
• Atria contract
• Forces remaining blood into ventricles
• Ventricles remain relaxed
• Ventricular systole
• Ventricles contract at same time
• Blood pressure increases
• AV valves forced shut (so no backflow)
• Semi-lunar valves forced open
• Blood pushed into aorta and pulmonary artery

Exercise 4
6
The conduction system of the heartHow the
cardiac cycle is controlled

• Initial impulse begins in the right atrium
  sinoatrial node SAN (pace maker)
• Wave of contraction spreads through atria causing
  them to contract
• Impulse passed to atrioventricular node AVN (lies
  between atria)
• AVN sends impulse along muscle fibres between
  ventricles (Bundle of His)
• Impulse conducted down septum to base of
  ventricles to Purkinje fibres
• Causes ventricles to contract

Exercise 5
http//www.quia.com/rd/30225.html?AP_rand60421903
6
Exercise 6
Click here for a summary sheet (Exercise 7)
7
Heart definitions

• STROKE VOLUME- volume of blood ejected from the
  heart when the ventricles contract (at rest 70
  cm3)
• HEART RATE the number of (ventricle)
  contractions in one minute (at rest 72bpm)
• STROKE VOLUME (Q) volume of blood ejected from
  the heart in one minute (at rest 5Litres)
• Q HR X SV

Exercise 8
8
Responding to exercise

• As exercise begins the following sequence of
  events takes place in the heart
• 1. Resting heart rate about 72 for untrained
  but for trained can be as low as 60.
• 2. Anticipatory rise due to the release of the
  hormone adrenalin. This acts on the SA node to
  increase heart rate.
• 3. Rapid increase of HR at start of exercise
  due to receptors proprioreceptors detect
  increased movement chemoreceptors detect
  increased CO2 and lactic acid and decreased O2.
  These stimulate the CCC which stimulates SA node
  to increase HR
• 4. Continued but slower increase of HR due to
  continued effect of receptors, increase in blood
  temp and increase in venous return.

9

• 5A Slight fall/ steady plateau (aerobic sub
  maximal work) due to oxygen supply meeting
  demand, baroreceptors slow HR to optimal via
  stimulation of para sympathetic nerves.
• 5B Continued rise in heart rate ( maximal
  aerobic work) due to anaerobic work where
  supply is below demand and to increasing lactic
  acid levels.
• 6 Rapid fall in heart rate as exercise stops
  due to decreased stimulation by receptors.
• 7 Slower fall in heart rate towards resting
  levels- due to elevated HR to help repay oxygen
  debt and to remove by products of respiration
  such as lactic acid.
• You should be able to show this information
  graphically
• Make sure whether the question asks for maximal
  or sub maximal exercise use either 5A or 5B
• NB maximum heart rate is 220 minus age

Exercise 9
10
Control of heart rate

• Heart rate is regulated by the cardiac control
  centre found in the medulla oblongata of the
  brain.
• The cardiac control centre is controlled by the
  autonomic nervous system.
• This system consists of sensory and motor nerves
  from either the sympathetic or parasympathetic
  nervous system.
• Sympathetic nerves increase heart rate and
  parasympathetic nerves decrease heart rate.
• The cardiac control centre initiates either
  sympathetic or parasympathetic nerves to
  stimulate the sino-atrial node to increase or
  decrease heart rate.

11

• There are three main factors which affect the
  activity of the cardiac control centre. They are
  neural, hormonal and intrinsic.
• Neural controlDuring exercise sensory receptors
  stimulate the cardiac control centre. These
  receptors include- proprio-receptors which
  sense that movement has increased.chemoreceptors
  which sense changes in chemicals in the muscles
  and blood. These changes include increased levels
  of carbon dioxide and lactic acid and increased
  acidity in the blood. baroreceptors which are
  sensitive to stretch within within the blood
  vessel walls. These detect increased blood
  pressure. The cardiac control centre responds to
  this information by stimulating the sino-atrial
  node via the sympathetic cardiac accelerator
  nerve to increase heart rate.

12

• Hormonal control
• Before and during exercise adrenalin is released
  in the blood.
• This stimulates the sino-atrial node to increase
  heart rate.
• Intrinsic control
• During exercise temperature increases which
  increases the speed of nerve impulses which in
  turn increases heart rate.
• Venous return increases heart rate which directly
  increases EDV and therefore stroke volume
  (Starlings Law).

Exercise 10
13
Blood vessels

• There are three main groups of blood vessels.
• Arteries and arterioles- transport oxygenated
  blood away from the heart.
• Capillaries bring blood to the tissues where
  oxygen and carbon dioxide are exchanged.
• Veins and venules transport deoxygenated blood
  back towards the heart.

14
Blood vessel structure

• Blood vessels have three layers except
  capillaries which are single walled.
• Arteries and arterioles have middle layer of
  smooth muscle which allows them to vasodilate
  (widen) and vasoconstrict (narrow).
• Arterioles have precapillary sphincters at the
  entry to the capillary. These control blood flow.
• Capillaries are one cell thick to allow efficient
  gaseous exchange.
• Venules and veins have thinner muscular walls.
  The can vasodilate and vasoconstrict. They also
  have valves to prevent the backflow of blood.

15
Venous return

• Starlings Law of the Heart states that stroke
  volume is dependent on venous return.
• At rest the amount of blood returning to the
  heart (venous return) is enough to supply the
  demands of the body.
• On exercise this is not enough so venous return
  must be increased. This happens in the following
  ways.

16
(No Transcript)
17
Click on the links to complete the exercises

• Exercise 11 summary sheet
• Exercise 12 matching exercise
• Exercise 13 crossword
• Exercise 14 cloze exercise

18
VASCULAR SHUNT

• At rest only a small of the blood supply is
  supplied to the muscles (15).
• The rest supplies the bodies organs.
• Changes during exercise
• Increased cardiac output is supplied to the
  muscles (80-85).
• Less blood is supplied to the body organs.
• Blood supply to the brain is maintained.
• During light exercise increased supply to the
  skin reduces temperature.
• The process of redistributing blood supply is
  called the vascular shunt mechanism.
• Skeletal muscle arterioles and pre-capillary
  sphincters vasodilate increasing blood supply to
  muscles.
• Organ arterioles and pre-capillary sphincters
  vasoconstrict decreasing blood supply to organs.

19
(No Transcript)
20
CONTROL OF THE VASCULAR SHUNT MECHANISM

• This is controlled by the vasomotor control
  centre found in the medulla oblongata of the
  brain.
• Chemoreceptors and baroreceptors stimulate the
  VCC.
• VCC stimulates the sympathetic nervous system
  which control blood vessel lumen diameter of
  organs and muscles.

21
Click on the links to complete the exercises

• Exercise 15 Cloze exercise
• Exercise 16 work sheet
• Exercise 17 Summary sheet

22
Oxygen and carbon dioxide transport

• Oxygen is transported in two ways
• 97 is carried in the red blood cells bound to
  haemoglobin as oxyhaemoglobin.
• 3 is carried dissolved in the plasma.
• Carbon dioxide is transported in three ways
• 70 combined with water within the red blood
  cells as carbonic acid.
• 23 combined with haemoglobin as
  carbaminohaemoglobin.
• 7 dissolved in the plasma.

23
Warm up

• Warm up effects on vascular system
• Gradual increase in blood flow brings more oxygen
  to working muscles
• An increase in temperature produces
• An increase in the rate transport of enzymes
  needed for the energy systems.
• A decrease in the viscosity of the blood which
  improves blood flow
• An increase in oxygen dissociating from
  oxyhaemoglobin
• A warm up delays the onset of blood lactic acid

24
Cool down

• An active cool down keeps respiratory and muscle
  pumps working which prevents blood pooling in the
  veins and maintains venous return.
• Capillaries remain dilated which means more
  oxygenated blood reaches the muscles which
  results in more lactic acid and carbon dioxide
  being removed.

Exercise 18
25
Click on the links for some revision games

• http//www.quia.com/rr/89411.html
• http//www.quia.com/mc/470408.html
• Just a minute