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What is the inspiratory reserve volume?
How much breath can be maximally taken in.
What is the tidal volume?
The resting breathing volume.
What is functional residual capacity?
Air remaining in the lungs after a normal breath to prevent collapse. Sum of expiratory reserve volume and residual volume.
Give the two definitions of dead space.
- Anatomical: space that conducts air to the alveoli
- Physiological: space in the airway that does not contribute to gas exchange.
What is the purpose of dead space?
To warm, filter and humidify air as well as deliver it to the alveoli.
What is alveolar ventilation and how is it measured?
- An indicator of the amount of CO2 expired.
- Tidal volume - dead space volume = alveolar ventilation.
Define and give the causes of hypoventilation.
- A decrease in ventilation without similar decrease in oxygen consumption / carbon dioxide production.
- 1. Increase in physiological dead space.
- 2. Respiratory muscle paralysis.
- 3. Tidal volume decrease by CNS depression.
Define and give the causes of hyperventilation.
- An increase in ventilation without similar increase in oxygen consumption / carbon dioxide production.
- 1. Asthma attack
- 1. Stress conditions.
Which neurones do the dorsal and ventral respiratory groups contain?
- Dorsal - inspiratory
- Ventral - expiratory
Outline the process of inspiration.
- 1. Diaphragm contracts and flattens. External intercostal muscles contract. Thoracic cavity volume increases. Alveolar pressure drops.
- 2. Intrapleural pressure drops.
- 3. Alveoli expand until the pressure gradient is satisfied.
Outline the process of expiration.
1. Intrapleural pressure increases, alveoli recoil and air is expelled.
What is compliance?
- Measure of system elasticity.
- ΔV / ΔP
How does gravity influence the ventilation:perfusion ratio?
At the top of the lung, both ventilation and perfusion will be lower. Gravity drags air and blood down to the bottom of the lung, creating both a higher pressure and compressed alveoli ready to inflate and blood pooling.
What does haemoglobin carry and in what section?
- Oxygen - haem, bound to iron molecule.
- Carbon dioxide - in globin. Converted to carbonic acid by carbonic anhydrase.
- Hydrogen ions - globin, as buffer.
- Carbon monoxide - haem, carbon monoxide poisoning.
What is the Haldane effect?
Releasing oxygen from haemoglobin increases availability for carbon dioxide binding. Carbonic anhydrase converts carbon dioxide, generating hydrogen ions, which enhances oxygen release. This cycle continues until no more carbon dioxide is available to propagate it.
What does a left Bohr shift indicate?
- More saturation at same pO2, so increased affinity. Possible causes:
- 1. Alkalosis
- 2. Hypocapnia
- 3. Hypothermia
What does a Bohr shift right indicate?
- Less saturation at same pO2, so decreased affinity. Possible causes:
- 1. Acidosis
- 2. Hypercapnia
- 3. Hyperthermia
- 4. 2,3 BPG
What are some types of hormone?
- 1. Peptide
- 2. Steroid
- 3. Amine
- 4. Catecholamine
- 5. Thyroid
Describe hypothalmic pituitary interaction for both the anterior and posterior pituitary.
- Anterior: hypothalamus secretes neurosecretory hormones into hypophyseal blood vessels. These hormones either inhibit / stimulate production of hormones in secretory cells in the anterior pituitary, which are, in turn, secreted into the hypophyseal blood vessels.
- Posterior: hypothalamus secretes neurosecretory hormones directly into the posterior pituitary, where they hit the bloodstream.
What major hormones does the anterior pituitary produce?
FSH, LH, somatotropin, ACTH.
What two hormones control GH secretion?
- GHRH (somatocrinin) (stimulates)
- Somatostatin (inhibits)
What effect may GH-excess have on the body?
- Pre-epiphyseal fusion: gigantism. normal body proportions, rapid growth, Type 2 diabetes.
- Post-epiphyseal fusion: acromegaly. abnormal body proportions, type 2 diabetes.
Why does excess GH cause type 2 diabetes?
GH at normal levels decreases glucose uptake to protect against hypoglycaemia. In excess, GH overrides insulin, creating insulin deficiency.
What are the effects of thyroxine?
Increase glucose mobilisation, lipolysis and heat production. Increase ventilation rate, heart rate and contractility. Permissive for growth.
What are the precursors for thyroxine?
Thymine and iodine.
What are the symptoms of hypothyroidism?
Low metabolic rate; fatigue, weight gain despite exercise.
What are the symptoms of hyperthyroidism?
High metabolic rate; weight loss despite increased appetite.
Which hormone from the pituitary stimulates cortisol production in the adrenal cortex?
ACTH aka corticotropin.
What is Cushing's syndrome?
Adrenal cortex hyperfunction; cortisol excess causes type 2 diabetes, poor wound healing, hypertension, fat redistribution.
What is Addison's disease?
autoimmune destruction of the adrenal cortex; lack of cortisol causes hypoglycaemia, very low blood pressure.
Give the reproductive hormones and their effects.
- GnRH - stimulates FSH and LH production in both sexes.
- FSH - In females, stimulates follicles to mature ready to release an egg.
- In males, stimulates Sertoli cells to produce sperm.
- LH - In females, stimulates ovulation and uterine wall building.
- In males, stimulates Leydig cells to produce testosterone.
- Oestrogen - at a certain level, stimulates LH peak that causes ovulation. Matures ovum and triggers secondary sexual characteristics. Females only.
- Progesterone - produced by corpus luteum, maintains uterine lining. Females only.
- Testosterone - stimulates spermatogenesis in Sertoli cells. Produced in Leydig cells stimulated by LH.
What two regulatory mechanisms are used in calcium balance?
- PTH - produced by parathyroid, causes calcium re absorption in kidneys.
- Vitamin D derivative calcitriol - Inhibits PTH, promotes bone mineralisation.
Give the effects of calcium imbalance.
- Hypercalcaemia: high depolarisation threshold causing CNS depression. Confusion, fatigue, kidney stones.
- Hypocalcaemia: low depolarisation threshold causing CNS hyper-excitability. Chvostek's sign to diagnose tetany. May be caused by alkalosis.
Give an overview of diabetes, both types.
- Type 1 - insulin deficiency. Susceptible to ketoacidosis, which can result in coma and death.
- Type 2 - insulin resistance. May be caused by Cushing's syndrome / GH excess. Susceptible to hypoglycaemia due to treatment imbalance.
What are the potential damaging effects of prolonged high blood glucose?
- Protein glycation
- Osmotic dieuresis
Describe the production of HCl in a parietal cell.
- 1. Carbon dioxide and water converted to bicarbonate ions and hydrogen ions by carbonic anhydrase.
- 2. Hydrogen ions pumped into stomach via H+/K+/ATPase.
- 3. Bicarbonate used as a co-transporter to bring chloride into the cell.
- 4. Cl- enters stomach via ion channel.
What is the role of gastrin?
Stimulate HCl output via g-protein receptor.
How are enzymes stored in the pancreas and where?
Acinar cells as zymogen granules.
Define transcellular and paracellular.
- Transcellular: solute movement through cells, requires carriers and energy dependent methods.
- Paracellular: solute movement around cells, depends on simple diffusion or solvent drag.
How do you find osmoles?
Number of moles x Number of dissociated components.
What is the main controller of ECF volume?
Give an overview of nephron structure.
Bowman's capsule and glomerulus form the corpuscle. Proximal tubule runs into the loop of Henle's descending tubule, followed by the ascending tubule running into the distal tubule, which leads to the ureter.
What is the counter current mechanism?
The pumping of solutes from the distal tubule into the interstitial space of the Loop of Henle to produce an osmotic gradient that draws water out of the proximal tubule.
Give an overview of the renin-angiotensin-aldosterone system.
When blood volume is low, juxtaglomerular cells produce renin, which converts angiotensin (AGT) into AGT 1, which is in turn converted to AGT 2 by ACE. AGT 2 stimulates production of aldosterone in the adrenal glands, which induces tubulur sodium reabsorption to increase blood volume.
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