Block 2 ALS Revision Questions

What are the three main stimulations for breathing?

• Central neural rhythm

• Chemical control (pH, O₂, hormones)

• Sensory input

What is the main nerve controlling respiration?

Vagus (X)

What solutions increase breathing?

Acidic

What solutions decrease breathing?

Alkaline

In patients with COPD, what drives their breathing?

Hypoxic drive (low oxygen)

What type of respiratory failure is marked by a raise in CO₂?

Type 2

What is the main hormone responsible for altering breathing rate?

Adrenaline

Why does hyperventilating lead to tingling sensation in extremeties?

Blows off CO₂ so more alkaline blood

This results in a drop in ionised calcium and causes excessive neuronal activity

Where are the main chemoreceptors found?

• Aortic arch

• Carotid artery

Which muscles of the thoracic wall are involved in inspiration?

External intercostal (elevate ribs)

Which nerves carries impulses for the cough reflex?

Internal laryngeal (branch of vagus)

What are the two functional divisions of the respiratory system?

• Conducting portion - all respiratory passages, cleanse, warm and humidify air

• Respiratory portion - site of gas exchange

What type of epithelial cells line the nasal cavity?

Pseudostratified ciliated columnar epithelium with goblet cells

• Inferior turbinate

• Middle turbinate

• Superior turbinate

• Choana

• Pharyngeal tonsil

• Uvula

• Soft palate

• Hard palate

What are olfactory mucosa?

Sensory receptors for smell

What is located superior to the superior turbinate?

Sphenoethmoidal recess

What are the subdivisions of the pharynx?

• Nasopharynx

• Oropharynx

• Laryngopharynx

Where does the nasopharynx begin and end?

• Base of skull

• Uvula and soft palate

Where does the oropharynx begin and end?

• Soft palate

• Epiglottis

Where does the laryngopharynx begin and end?

• Epiglottis

• Cricoid cartilage

What are the three circular muscles of the pharynx?

• Superior constrictor

• Middle constrictor

• Inferior constrictor

What are the three unpaired cartilages of the larynx?

• Epiglottis

• Thyroid

• Cricoid

What are the three paired cartilages of the larynx?

• Arytenoid

• Cuneiform

• Corniculate

• Epiglottis

• Thyrohyoid membrane

• Corniculate cartilage

• Arytenoid cartilage

• First tracheal cartilage

What does the base of an arytenoid cartilage attach to?

Vocal process

What is the function of the laryngeal muscles?

Abduct and adduct the vocal folds

• Epiglottis

• Hyoid bone, greater cornu

• Vestibular fold

• Thyroid cartilage

• Vocal fold

• Cricoid cartilage

At what vertebral level is the thyroid cartilage located?

C3/4

What structures support the trachea?

C-shaped cartilage rings

At what level does the trachea bifurcate?

T4-5

Angle of Louis

In which main bronchus are objects most likely to become lodged and why?

Right main bronchus

Wider, shorter, more vertical

What are the two coverings of the lungs?

• Visceral pleura

• Parietal pleura

What is the hilum of a lung?

Point where structures enter and leave the lung

What are the three main components of the hilum?

• Main bronchus

• Pulmonary artery

• Pulmonary veins

How many lobes does each lung have?

• Right - 3

• Left - 2

What is the mechanism of normal inspiration?

• Diaphragm contracts and descends

• External intercostal muscles contract to raise ribs

• Volume of thoracic cavity increases

• Intrathoracic pressure drops to below atmospheric

• Air moves in down pressure gradient

What effect does the vagus have on the bronchioles?

Constriction

What sympathetic portion dilates the bronchioles?

Sympathetic T2-5

What is the embryological origin of the heart?

Cardiogenic mesoderm

What structure gives rise to the diaphragm?

Septum transversum

What is the mediastinum?

The part of the thoracic cavity between the two pleural cavities

What are the five divisions of the mediastinum?

• Superior

• Inferior

• Middle

• Anterior

• Posterior

Which portion of the mediastinum do the vagus and phrenic nerves pass through?

Superior

What is the main content of the middle mediastinum?

The heart

What supplies all parasympathetic innervation to the airways?

Vagus nerve

Which spinal segments provide sympathetic innervation to the airways?

T1-6

What are the three cell types in respiratory mucosa?

• Ciliated epithelial

• Goblet cells

• Basal cells

What shape are the mucosa in the bronchioles?

Cuboidal

What is the function of basal cells?

Stem cells that also contribute to structure

What is the ventilation perfusion ratio?

Matching perfusion (blood supply) to areas of greater ventilation

How is the majority of oxygen transported in the blood?

Bound to haemoglobin

What is an alveolar sac?

Two or more alveoli that share a common opening

What epithelial cells line the alveoli?

Simple squamous epithelium

What is the function of type 1 alveolar cells?

Gas exchange

What is the function of type 2 alveolar cells?

Secrete alveolar fluid - reduces likelihood of alveolar collapse by reducing surface tension within alveoli

What are the four layers of the respiratory membrane?

• Alveolar wall (type 1 and 2 cells)

• Epithelial basement membrane

• Capillary basement membrane

• Capillary endothelium

What is the rate of removal of carbon dioxide by the lungs?

200ml/min

What is the histology of the terminal bronchioles?

Non-ciliated simple cuboidal epithelium

How is ventilation calculated?

Respiratory rate (/min) x tidal volume (l)

What is FVC?

Forced vital capacity

What is FEV₁?

Forced expiratory volume in 1 second

What is the ideal gas law?

P V = n R T

P = pressure (Pa)

V = volume (m³)

n = number of moles

R = gas constant (8.314 J K^-1 mol^-1)

T = temperature (K)

What is Dalton’s law of partial pressures?

The total pressure of a mixture of gases is equal to the sum of the partial pressures of each gas

What shifts the oxygen dissociation curve to the right?

• Reduced pH

• Increased PO₂

• Increased temperature

• Increased DPG

What does a shift of the oxygen dissociation curve to the left represent?

Increased affinity of haemoglobin for oxygen

How can carbon dioxide be transported?

• Dissolved in plasma (7%)

• As carbamino compounds (23%)

• As bicarbonate (70%)

What are the metabolic consequences of a drop in blood pH?

• Diabetic ketoacidosis (DKA)

• Renal failure

What is the smallest contractile unit of muscle?

Sarcomere

Which two proteins are the units of muscle fibres?

• Actin - thin filament

• Myosin - thick filament

What protein inhibits actin and myosin coupling?

Troponin I

What initiates the contraction of heart muscle?

Sinoatrial (SA) node

What is inotropy?

Increase in the force of contraction

What is the normal duration of the cardiac cycle?

0.8 s

What are the five stages of the cardiac cycle?

• Atrial systole

• Isometric ventricular contraction

• Ejection phase

• Isometric ventricular relaxation

• Slow filling

What happens during atrial systole?

• P wave

• Mitral valve open

• Aortic valve closed

What happens during isometric ventricular contraction?

• QRS

• All valves closed

• First heart sound - closure of valves

What is the ejection phase?

• ST segment

• Aortic valve opens

• Blood ejected from heart

• Valves open when pressure in heart is higher than in the aorta

What happens in isometric ventricular relaxation?

• T wave

• All chambers in diastole

• All valves closed

What happens during slow filling?

• V wave on atrial trace

• Passive filling of atria and ventricle

• AV valves open

• Mitral valve closes

• Isovolumetric contraction

• Aortic valve opens

• Aortic valve closes

• Isovolumic relaxation

• Mitral valve opens

How is cardiac output calculated?

Stroke volume x heart rate

During exercise, what is the main way to increase cardiac output?

By raising heart rate

What is the Frank-Starling effect?

• Increasing fibre length → increased velocity of contraction

• Increased end diastolic volume → increased stroke volume

What is unique about cardiac muscle?

It is myogenic

Which ion initiates an action potential in pacemaker cells?

Ca²⁺

Which two membranes cover the heart?

• Fibrous pericardium

• Serous pericardium

What does blood flow through from the right atria into the right ventricle?

Right atrioventricular orifice

How many papillary muscles are there in the right ventricle?

3

What attaches each papillary muscle to a cusp of a valve?

Chordae tendinae

What type of valve are the pulmonary and aortic vaves??

Semilunar

What causes the closure of the pulmonary and aortic valves?

Recoil of blood into the sinuses

What embryologically allows the flow of blood between the two atria?

Fossa ovale

What is the embryological origin of the cardiovascular system?

Cardiogenic mesoderm

What supplies blood to the right atrium and ventricle?

Right coronary artery

• Right coronary artery

• Posterior descending artery

• Right marginal artery

• Left coronary artery

• Left circumflex artery

• Left marginal artery

• Left anterior descending (interventricular) artery

• Diagonal branch

What are the three cardiac veins?

• Great

• Middle

• Small

Where do all the cardiac veins drain into?

Coronary sinus

Then into the right atrium

What nerve provides parasympathetic innervation to the heart?

Vagus nerve

What are the three types of cell found in the heart?

• Pacemaker - SA & AV nodes

• Purkinje fibres

• Muscle cells

What is automaticity?

Even at resting potential some cells have a flux of ions that increase transmembrane potential

Can be enough to trigger further depolarisation

Generates normal heart rhythm