B – The Cardiovascular System The structure and function of arteries, capillaries and veins The structure and function of the heart Pathology of cardio vascular disease (CVD) Blood glucose levels and obesity

KA 6: The structure and function of the heart 2.6 Key Topics REVISION: Structure of the heart (D) Blood Pressure (A) Cardiac function and cardiac output (B) Cardiac cycle (C) The structure and function of cardiac conducting system

KA 6c: Learning Outcomes Give another name for the pacemaker Describe the action of the SAN on the cardiac muscle cells, including how this stimulates the AVN Identify SAN and AVN locations in a diagram State the role of an ECG Interpret ECG graphs in order to calculate heart rate State that the heart beat can be regulated by both nervous and hormonal control State the role of medulla and the ANS Name the 2 nerves that can release hormones State the names of these 2 hormones and describe the effect they have on the heart beat

Cardiac Conducting System The events of the cardiac cycle are brought about by the activity of the heart’s pacemaker, or sino-atrial node (SAN) It is located in the wall of the right atrium

Cardiac Conducting System The SAN is a small region of specialised tissues that contains auto-rhythmic cells. These cells initiate electrical impulses that make the cardiac muscle cells contract at a certain rate.

Cardiac Conducting System The timing of cardiac cells contracting is controlled by the impulse from the SAN: Spreading through the atria and then travelling to the atrio-ventricular node (AVN) and then through the ventricles. These impulses generate currents that can be detected by an electrocardiogram (ECG).

P wave QRS complex T wave

ECGs This electrocardiogram (ECG) shows one cardiac cycle

ECGs An ECG measures the electrical changes that take place in the heart. P wave – the wave of electrical impulses spreading over the atria from the SAN Q-R-S complex – the electrical impulses through the ventricles T wave – the electrical recovery of the ventricles at the end of ventricular systole.

The person’s heart beat is: ______ bpm Answer = B The person’s heart beat is: ______ bpm

KA 6c: Learning Outcomes Give another name for the pacemaker Describe the action of the SAN on the cardiac muscle cells, including how this stimulates the AVN Identify SAN and AVN locations in a diagram State the role of an ECG Interpret ECG graphs in order to calculate heart rate State that the heart beat can be regulated by both nervous and hormonal control State the role of medulla and the ANS Name the 2 nerves that can release hormones State the names of these 2 hormones and describe the effect they have on the heart beat

What do you remember? THINK/PAIR/SHARE – 2 minutes! What are 3 main parts of the brain? What do they do? The brain is part of which body system? What do nerves do? What do hormones do?

Nervous System Central NS Brain Spinal cord Peripheral NS Somatic NS Autonomic NS Sympathetic Parasympathetic

Para - sympathetic nerve Nervous System Central NS Brain Spinal cord Peripheral NS Somatic NS Autonomic NS Sympathetic nerve Para - sympathetic nerve Nor-epinephrine Acetylcholine Control centre Impulses can be sent along both of these nerves to the heart. The heart rate depends on which system exerts a greater influence over the heart.

Tasks! Read page 168, from the title ‘regulation’ onwards Stick in your diagram and label it using page 168 of the textbook Write the title: The conducting system of the heart & how it is controlled Complete the missing words exercise and stick it in!

Wordbank! Acetylcholine Medulla Antagonistic Atrium Parasympathetic Autonomic AVN Sympathetic Speeds up Contract Slows down Diastole Ventricles Ventricular systole Impulses

Impulses originate in the control centres in the _________ The conducting system of the heart is controlled by the _________ nervous system It is made up of the sympathetic and ___________systems. These two systems are _________in action The sympathetic nerve _________the heart rate and parasympathetic nerve _________the heart rate Impulses originate in the control centres in the _________ The hormone nor-adrenaline (nor-epinephrine) is released by _________accelerator nerves, whereas the hormone _________is released by the slowing parasympathetic nerves. The pacemaker or SAN is located in the right _________ Once stimulated, the SAN starts producing _________and contracts These impulses cause the atria to _________ (atrial systole) This then stimulates the _________, which is found at the junction between the atria and ventricles The impulse from the AVN is carried by conducting nerves, which spread out over the _________. This causes the contraction of ventricles (_________________), followed by relaxation (____________) autonomic parasympathetic antagonistic Speeds up Slows down medulla sympathetic acetylcholine atrium impulses contract AVN ventricles diastole Ventricular systole

Think! Why does your heart rate increase during exercise?

Hormonal Regulation of SAN If stressed or during periods of exercise, the sympathetic nervous system acts on the adrenal glands, causing the release of adrenalin into the blood stream. Upon reaching the SAN in the heart, the adrenaline causes the SAN to generate cardiac impulses at a higher rate, therefore bringing about an increase in heart rate!

Re-cap! http://www.austincc.edu/apreview/NursingAnimations/cardiac_cycle.swf Don’t worry about advanced language: Pulmonary valve / aortic valve = SL valves Depolarisation = contraction Repolarisation = relaxation Further details on P QRS T graph

KA 6c: Learning Outcomes Give another name for the pacemaker Describe the action of the SAN on the cardiac muscle cells, including how this stimulates the AVN Identify SAN and AVN locations in a diagram State the role of an ECG Interpret ECG graphs in order to calculate heart rate State that the heart beat can be regulated by both nervous and hormonal control State the role of medulla and the ANS Name the 2 nerves that can release hormones State the names of these 2 hormones and describe the effect they have on the heart beat