Muscular Movement (Edexcel International A Level (IAL) Biology): Flashcards

The sarcolemma is the cell surface membrane of a muscle fibre, surrounding it and helping transmit electrical impulses.

The cell surface membrane of a muscle fibre is called the sarcolemma.

The cell surface membrane of a muscle fibre is called the sarcolemma.

False.

Muscle fibres are multi-nucleated, meaning they contain many nuclei.

A fast twitch muscle fibre is a muscle fibre that contracts rapidly and is adapted for short bursts of high-intensity activity, but fatigues quickly.

A slow twitch muscle fibre is a muscle fibre that contracts more slowly and is adapted for endurance and sustained activities, fatiguing less quickly.

Slow twitch muscle fibres have higher amounts of myoglobin and mitochondria, along with a dense capillary network, to support aerobic respiration and endurance.

Fast twitch muscle fibres rely on anaerobic respiration for ATP supply and fatigue quickly due to lactate production.

Slow twitch muscle fibres appear dark red in colour due to high amounts of myoglobin.

False.

Fast twitch muscle fibres fatigue quickly and are suited to short bursts of high-intensity activity, not endurance.

Fast twitch muscle fibres contract rapidly, while slow twitch muscle fibres contract more slowly.

The sarcoplasmic reticulum (SR) stores calcium ions needed for muscle contraction.

Myosin is a fibrous protein molecule with a globular head that forms the main component of thick filaments in a myofibril.

Thin filaments are made up of actin molecules, which are globular protein molecules that form twisted chains.

During muscle contraction, sarcomeres within myofibrils shorten as the Z discs are pulled closer together.

False.

The myosin and actin filaments do not change length; instead, they slide over one another during muscle contraction.

A cross-bridge is formed when the globular heads of myosin bind to exposed binding sites on actin filaments.

Calcium ions bind to troponin, causing a shape change that moves tropomyosin and exposes the myosin binding sites on actin filaments.

Calcium ions bind to troponin molecules, causing a change in shape that moves tropomyosin and exposes myosin binding sites on actin filaments.

Once muscle stimulation stops, calcium ions are actively transported back to the sarcoplasmic reticulum, causing muscle relaxation.

ATPase on the myosin head hydrolyses ATP into ADP and inorganic phosphate, releasing the energy needed for the myosin head to perform the power stroke that pulls the actin filament along.

An electrocardiogram (ECG) is a trace produced by electrodes on the skin that records the electrical activity of the heart.

A myogenic muscle can contract without any external stimulus; the heart beats due to its own electrical activity.

The P wave is caused by the depolarisation of the atria, which results in atrial contraction (systole).

The QRS complex represents the depolarisation of the ventricles, leading to ventricular contraction (systole).

The T wave of the ECG is caused by the repolarisation of the ventricles, resulting in their relaxation (diastole).

True.

The bigger the wave on an ECG, the greater the electrical activity passing through the heart, resulting in a stronger contraction.

The sinoatrial (SA) node (SAN) initiates a wave of depolarisation that causes the atria to contract.

The bundle of His is a collection of conducting tissue in the septum that transmits electrical impulses from the AVN to the Purkyne fibres in the ventricles.

Tachycardia is when the heart beats too fast, usually defined as a resting heart rate over 100 beats per minute.

Bradycardia is when the heart beats too slowly, with a resting heart rate below 60 bpm. It is not always dangerous, as fit individuals may naturally have lower heart rates.

An ectopic heartbeat is caused by an early heartbeat followed by a pause.

Fibrillation is an irregular heartbeat in which the atria or ventricles stop contracting properly, disrupting heart rhythm, which can be life-threatening.

Purkyne fibres carry the wave of depolarisation to the apex of the ventricles, causing them to contract from the bottom upward.

The atrioventricular node (AVN) delays the wave of depolarisation before passing it on to the bundle of His, ensuring the atria finish contracting before the ventricles contract.

Stroke volume is the volume of blood pumped out of one ventricle of the heart in a single heartbeat.

During exercise, the body increases both the rate and depth of breathing and the heart rate, so more oxygen can be delivered to muscles and more carbon dioxide can be removed.

The ventilation centre in the medulla oblongata controls the rate and depth of breathing.

Chemoreceptors are specialised cells that detect changes in the chemical composition of the blood, such as oxygen, carbon dioxide, and pH levels.

Cardiac output = heart rate × stroke volume

During exhalation, the intercostal and diaphragm muscles relax causing the volume of the chest to decrease and air to flow out.

True.

Stretch receptors in the lungs send nerve impulses to the medulla oblongata to inhibit the inspiratory centre when the lungs inflate.

Cardiac output is the volume of blood pumped by the heart per minute.

Cardiac output = heart rate × stroke volume.

Stroke volume is measured in cm³.

The heart rate is the number of times the heart beats per minute.

Exercise increases cardiac output so that the blood supply matches the increased metabolic demands of the cells.

Baroreceptors detect high and low blood pressure and send impulses to the cardiovascular control centre to help regulate heart rate.

Parasympathetic neurones secrete acetylcholine which decreases the rate at which the SAN fires.

True.

Sympathetic neurones release noradrenaline which increases the rate at which the SAN fires, speeding up the heart rate during exercise.

The fight or flight response is a physiological reaction to stress, fear or excitement, where the sympathetic nervous system stimulates the adrenal medulla to release adrenaline, preparing the body for immediate action.

Adrenaline is a hormone that prepares the body for reacting to stressful situations by triggering the fight or flight response, which includes increasing heart rate and directing energy to the muscles.

During the fight or flight response, the sympathetic nervous system stimulates the adrenal medulla to release adrenaline.

False.

Adrenaline is a hormone and is transported around the body in the bloodstream.

Adrenaline binds to receptors on its target organs, including the SAN, to increase heart rate.

Blood flow to the brain remains constant because it is one of the most important organs and requires a constant supply of blood to function properly, regardless of stress or relaxation.

Blood vessels supplying less important organs (such as the digestive system and skin) constrict, diverting more blood to the muscles so they receive more oxygen and glucose for respiration.

Adrenaline acts as a first messenger, binding to a receptor and triggering the production of cyclic AMP (cAMP) as a second messenger inside the cell.

Tidal volume is the volume of air that is breathed in or out during normal breathing at rest.

Breathing rate is the number of breaths taken in one minute.

Oxygen consumption is the volume of oxygen used up by an organism in a given time.

Respiratory minute ventilation is the actual volume of air breathed in or out per minute.

Respiratory minute ventilation is calculated as tidal volume × breathing rate.

A spirometer is used to measure tidal volume, breathing rate and oxygen consumption.

A spirometer works by the subject breathing through the spirometer, allowing measurement of various lung volumes.

True.

Soda lime absorbs carbon dioxide from exhaled air to prevent its build-up in the spirometer.

To calculate the breathing rate from a spirometer trace, count the number of peaks in one minute.

Residual volume is the small amount of air that always remains in the lungs after maximum exhalation.

During exercise, both the breathing rate and the tidal volume increase.

Tidal volume can be determined by calculating the average difference in the volume of gas between each peak and trough on the trace.

False.

The total volume of air in the spirometer decreases as oxygen is consumed by the subject.

Respiratory minute ventilation can be calculated by multiplying tidal volume by breathing rate.