control of heartbeat/ electrical activity of the heart

what is the heart made up of?

cardiac muscle

myogenic

The heart can initiate its own contractions within its muscle, without nerve impulses.

name the feature of the heart that controls its heartbeat →location

→role

-sino-atrial node (SAN)

→wall of right atrium

→ a pacemaker

-atrioventricular node (AVN)

→in the right atrium, near the septum

→receives the impulse from the SAN.

-bundle of His

→ in septum

→conducts the impulse from the AVN to the Purkyne tissue.

-Purkyne tissue

→ventricular walls

→conducts the impulse to the ventricle walls

describe how heart beat occurs

-The SAN produces electrical impulses [waves of excitation/ depolarisation]

-the impulse spreads across the atria, causing the atria to contract

-The impulse reaches the atrioventricular node (AVN) and is delayed slightly→This allows the ventricles to fill up with blood before contracting

-The bundle of His receives the impulse and conducts it to the apex (base) of the heart.

-the impulse travels through the Purkyne fibres, which branch through the ventricle walls
-This causes the ventricles to contract from the bottom up

role of non-conducting tissue

prevents the electrical impulse from passing directly from the atria to the ventricles.

What changes in the body may change heart activity? (3)

-exercise

-stress

-sleep

name of machine used to check function of heart.

→What does it record?

→how do they work?

Electrocardiograph

→records the electrical activity of the heart

→electrodes are placed on the chest to record change in polarisation in the heart muscle

what happens when heart muscle contracts and relaxes

-it depolarises (loses electrical charge) when it contracts

-it repolarises (regains charge) when it relaxes

name of trace produced by electricardiograph

→parts of it

electrocardiogram (ECG)

→ -P wave→ contraction (depolarisation) of the atria

-QRS complex→ contraction (depolarisation) of the ventricles [Q→ electrical impulses going down the Bundle of His]

-T wave→ relaxation (repolarisation) of the ventricles

heart rate formula

heart rate=60/ time taken for one heartbeat

normal heart rate

60-100 bpm

types of abnormal activity

Tachycardia - fast heartbeat (over 100 bpm)

Bradycardia - slow heartbeat (under 60 bpm)

ectopic heartbeat - an extra heartbeat that occurs out of the normal rhythm.

fibrillation - irregular heartbeat

how might some abnormal activity be treated?

pacemaker for bradycardia

reduce stress for ectopic heartbeat