36-37;AP/ECG

Question 1

living cell as an electric force

Answer 1

membrane of living cell maintains PD between inside and outside of cell

Diffusion of ion provides V necessary to prevent further diffusion and keep rest membrane potential, around 70-90mV

movement of Na+/K+/Cl- determined by conc/electric potential gradient and membrane permeability for that ion

Question 2

action potential

Answer 2

membrane of nerve cell sufficiently stimulated to release some of its stored energy

1. depolarisation = -90mV to +30 mV = membrane permeable to Na+
2. repolarisation = immediate, brings inside potential back to -90mV/resting Potential

speed from 1 - 100m/s

AP can be transmitted to neighbouring membrane areas = successive stimulation propagating through cell

Question 3

ECG/Electrocardiogram

Answer 3

direct measurement of V produced by body

no transducer used

Question 4

pumping cycle of heart due to electrical conduction

Answer 4

initiated by electrical impulse generated in sinoatrial node = self-stimulated AP

SA nodes responds to in/decrease demand for blood = generates and conducts electrical impulses over specified paths = natural pacemaker = controls heart rate

Question 5

electrical conduction process controlling heart’s pumping cycle

Answer 5

1. SA node stimulates atrial contraction, impulses travel to AV node
2. AV node depolarises = electrical impulses travel to myocardium and Bundle of His via conducting system
3. CS branches into Purkinje fibres = allows ventricle to contract sharply = effective pumping impulses

Question 6

triangle of Einthoven

Answer 6

electrodes via Einthoven triangle - larger signals w/ less electrical noise

RA-LA-LL

Question 7

Features of ECG

Answer 7

P wave= depolarisation of SA node
QRS complex=depolarisation of AV node + conduction to ventricles
T wave = repolarisation of AV node + ventricular conduction system

Question 8

electroencephalogram EEG

Answer 8

electrodes placed on scalp to record electrical signals produced by brain

X signals need to amplified by factors of 1000s = electrical noise
X EEG signals not correlated w/ specific brain activity as precisely as ECG pulses related to heart cycle

alpha waves decrease during sleep, delta waves = deep sleep

diagnosing epilepsy, tumours, drug addition

Question 9

cardiac pacemaker

Answer 9

artificial implanted device implanted subcutaneously in abdominal region and leads connect it to the heart

battery powered device generating electrical stimuli at predetermined state

electrodes make contact w/ myocardium = arrival of sufficient electric impulses = allows heart to contract

X provision of a power supply = lasts long periods of time