Exercise Physiology and Pharmacology

Arterial Blood

5 litres contains 1L oxygen, 15ml physically dissolved and remainder bound to Hb.

Haemoglobin

A protein in red blood cells that binds to oxygen and carries it throughout the body.

diaphragm and external intercostal muscles

involved in regular breathing

forced exhalation

involves sternum, internal intercostal muscles and abdominal muscles. The diaphragm contracts more.

Carotid chemoreceptors

detect changes in oxygen and carbon dioxide levels in the blood and send excitatory signals to inspiratory neurones.

Death by opioid abuse

opioids decrease activity of pacemaker neurones in the medulla which drive breathing

Pacemaker Neurons

Neurons in the medulla oblongata that regulate the rhythm of breathing.

Carbon Monoxide Poisoning

Carbon monoxide irreversibly binds to haemoglobin, preventing oxygen from binding

Somatic Motor Nerves

control voluntary movements of skeletal muscles

Myofibrils

Contractile structures within multinucleate skeletal muscle cells that contain thick myosin and thin actin and troponin fibres.

Transverse Tubules (T tubules)

Extensions of plasmalemma that allow propagation of action potentials deep into the muscle cell.

action potentials (AP) in muscle cells (requires ATP)

AP propagated into T tubules → calcium ion release from sarcoplasmic reticulum. Calcium ions bind troponin → tropomyosin moves → myosin binds troponin.

ATP hydrolysis in skeletal muscle contraction

drives cross-bridge cycling (myosin ATPase), restoration of plasma membrane ion gradients (Na+/K+ pump) and return of calcium from cytosol to sarcoplasmic reticulum.

Phosphocreatine

rapidly regenerates ATP in skeletal muscle cells

Slow-Twitch Fibers

Contract slowly. Resistant to fatigue and contain many mitochondria and myoglobin.

Fast-Twitch Fibers

Muscle fibers that contract quickly and fatigue more easily, containing fewer mitochondria but more glycolytic enzymes and glycogen stores.

Motor Units

A motor neuron and the muscle fibers it innervates.

Neuromuscular junction Blockers

Mimic ACh but are hydrolysed more slowly, causing sustained contraction and paralysis.

non-depolarising NMJ blockers eg tubocurarine

inhibit nAChR, preventing ACh binding and EPP formation

Botulinum Toxin A

inhibits release of acetylcholine, leading to muscle paralysis.

Dantrolene

inhibits release of calcium ions from the sarcoplasmic reticulum. Used to treat muscle spasticity or malignant hyperthermia.

Malignant Hyperthermia

A potentially fatal condition caused by a genetic mutation that leads to uncontrolled release of calcium ions in response to certain anaesthetics.

low intensity aerobic exercise

increases number of mitochondria and capillaries in skeletal muscle

endurance training

causes fast-glycolytic fibres to become fast-oxidative-glycolytic fibres

high intensity strength training

increases diameter of fast-twitch fibres (hypertrophy), increases expression of glycolytic enzymes and causes greater synchronisation of motor unit recruitment

VO2 Max

The maximum rate of oxygen consumption during exercise

activity from brain ‘exercise centres’ during exercise

reduce parasympathetic output to heart and increase sympathetic output to heart, veins, abdominal arterioles and kidneys

Cardiac Output

The volume of blood pumped by the heart per minute.

Skeletal Muscle Pump

The contraction of skeletal muscles that helps propel blood back to the heart.

Respiratory Pump

The changes in pressure within the chest during breathing that assist in venous return.

Venous Return

The flow of blood back to the heart from the veins.

Stroke Volume

The volume of blood pumped by the heart with each contraction.