Practical 4. Human Physiology Flashcards
What is voluntary muscle contraction the result of ?
Communication between the brain and individual muscle fibres of the musculoskeletal system
What results in muscle contraction ?
A thought being transformed into electrical impulses that travel down interneurons and motor neurons to the neuromuscular junctions that form a motor unit
What is a hand dynamometer used for ?
Measuring maximum grip strength
What are the initials for an electrocardiogram ?
ECG or EKG
What is an electrocardiogram ?
A graphical recording of the electrical events occurring within the heart
What initiates an electrical sequence in a healthy heart ?
The pacemaker in the right atrium specifically the sinoatrial node
What does the impulse pass down ?
Conduction pathways between the atria to the atrioventricular node and from there to both ventricles
What do conduction pathways facilitate ?
Orderly spread of the impulses and coordinated contraction of first the atria and then the ventricles
What does electrical conductance create ?
Unique deflections in the ECG that give information about heart function and health
What is the p-wave ?
Represents atrial depolarisation
What does atrial depolarisation result in ?
Atrial contraction
What is the P-R interval ?
Time from the beginning of the P wave to the start of the QRS complex
What is the QRS complex ?
Time from Q deflection to S deflection
What is the Q-T interval ?
Time from Q deflection to the end of the T
What is R ?
The largest part of the wave
What is Q ?
The beginning of the R
What does Q represent ?
Depolarisation in the septum
What does R represent ?
The electrical stimulus as it passes through the main portion of the ventricular walls
What is the S ?
The smallest part of the large waves
What does S represent ?
The final depolarisation of the ventricles
What is the T-wave ?
Repolarisation of the ventricular myocardium
What is blood pressure a measure of ?
Changing fluid pressure within the circulatory system
What does blood pressure vary between ?
A peak pressure produced by contraction of the left ventricle, to a low pressure
What is low blood pressure maintained by ?
Closure of the aortic valve and elastic recoil of the arterial system
What is the pressure peak called ?
Systole
What is meant by diastole ?
Pressure that is maintained even while the left ventricle is relaxing
Why is mean arterial pressure not a simple average of two pressures ?
The duration of diastole is twice that of systole
How is MAP used by emergency room and icu ?
A measure of adequacy of blood supplies to vital tissues when blood pressure is dangerously low
What does the cold stimulus activate ?
The sympathetic nervous system resulting in haemodynamic changes that prepare the body for fight or flight response
What makes the sensitivity of blood pressure to harmful external or internal injuries useful ?
Its a vital sign, an indicator or health, disease, excitement and stress
What does measurement of lung volume provide a tool for ?
Understanding normal function of the lungs as well as diseased states
What is the breathing cycle initiated by ?
Expansion of the chest
What happens during quite breathing ?
Contraction of the diaphragm muscle causing it to flatten downwards
What does the contraction of the diaphragm muscle do ?
Increases the vertical dimension of the thoracic cavity
What lifts the ribs ?
External intercostals
What do external intercostals do ?
Lift the ribs, expanding the outwards and increase the cavity volume
What does the increase in chest volume do ?
Creates a negative pressure and draws air through the nose and mouth
What is normal exhalation ?
Passive
What does normal exhalation result from ?
Recoil of the chest wall, diaphragm and lung tissue
What does active breathing use ?
Accessory respiratory muscles
What are some examples of accessory respiratory muscles ?
- Sternocleidomastoid
- Scalenes
- Internal intercostals
- Abdominal muscle groups
What is the function of accessory respiratory muscles ?
To further expand and contract the thorax
What is the total lung capacity used at rest in normal breathing ?
1/10 the total lung capacity
What is tidal volume ?
The volume of air breathed in and out without conscious effort
What is inspiratory reserve volume ?
The additional volume of air that can be inhaled with maximum effort after a normal inspiration
What is expiratory reserve volume ?
The additional volume of air that can be forcible exhaled after normal exhalation
What is vital capacity ?
The total volume of air that can be inhaled after a maximum exhalation
What is the equation for vital capacity ?
Tidal volume + Inspiratory reserve volume + expiratory reserve volume = vital capacity
What is residual volume ?
The volume of air remaining in the lungs after maximum exhalation
What cannot happen to the lungs ?
They can never be completely emptied
What is the equation for total lung capacity ?
Vital capacity + residual volume = total lung capacity
What is minute ventilation ?
The volume of air breathed in one minute
What is the equation for minute ventilation ?
Tidal volume x breaths per minute
