SIMARA CLOUDHURY DEHYDRATION Adam Reynolds M1900276@sgul.ac.uk - - PowerPoint PPT Presentation

SIMARA CLOUDHURY – DEHYDRATION

Adam Reynolds M1900276@sgul.ac.uk Will Nash m1902620@sgul.ac.uk

OVERVIEW

• Our top tips for the year
• Useful resources
• Practice SBA Questions
• Questions

TOP TIPS FOR THIS YEAR (1)

• DR DEAC PIMP – Nice way to summarize a disease
• Definition
• Risk Factors
• Differential Diagnosis
• Epidemiology
• Aetiology
• Clinical Features
• Pathophysiology
• Investigations
• Management
• Prognosis

TOP TIPS FOR THIS YEAR (2)

• MICRA – Nice way to summarize drugs
• Mechanism of Action – How it works
• Indications – What it is used for
• Contraindications – Who should NOT have this drug
• Route of Administration – How the drug is given
• Adverse Effects/Side Effects – What the side effects of this are (they love exam questions on this!!)
• Go over the PBL Cases and try to understand the actions the doctors take

USEFUL RESOURCES

• Armando
• Osmosis – Need to pay but get a group together – worth it!
• PassMedicine - Question Banks – more for later years
• Anki
• T

each Me Anatomy

• AMBOSS
• BMJ Best Practice
• Zero to Finals – Great podcast
• Geeky Medics – OSCE
• Leeds University - Histology
• T

extbooks

• T
• p 100 Drugs
• USMLE First Aid
• Kumar and Clark

MEET YOUR GEP PARENTS!

• Wednesday 9th September at Tooting Common
• Come and meet your GEP Parents
• Due to social distancing there will be time slots for you to come

and meet your parents.

• All details are on your GEP Facebook page!

• Fluid Compartments, Fluid Balance and Fluid Movement
• Intro to Structure and Function of the Kidney
• Pharmacology
• Autonomic Nervous System
• Anatomical T

erminology

KEY AREAS OF THE WEEK

• Everything this week (and in the foundation

module) will be repeated.

• Don’t worry if you don’t understand everything

perfectly this week, you will come back to it and it will be much clearer!

• Use the Foundation Module to develop your own

system to learn medicine!

FLUID LOSSES

• Fluid Losses
• Insensible - ~700 – 800 ml/day
• Evaporation from the respiratory tract – respiratory droplets
• Diffusion through the skin
• Sensible – Much more variable
• Sweat – Can depend on climate or physical exertion. Usually ~100 ml/day but

can be 1-2 L/day following strenuous activity.

• Faeces – Usually only a small amount but can be up to 5-7 L/day in severe

diarrhoea.

• Urine (Kidneys) – Highly variable depending on level of hydration or diseases.

FLUID REQUIREMENTS

• Fluid Requirements
• Generally, 2 – 2.5 L of water a day, but this is highly variable
• Majority of water gained is from ingestion.
• We make a small amount from the oxidation of carbohydrates,

~200ml/day

FLUID COMPARTMENTS

• 2 main stores of fluid in the body
• Intracellular (2/3 of total fluid)
• Water inside cells
• Extracellular (1/3 of total fluid)
• Plasma – fluid component of blood
• Interstitial Fluid – fluid surrounding cells
• Only separated by thin capillary membrane
• 60, 40, 20 Rule
• 60% of the body is water, 40% (2/3) of this water is

intracellular, 20% (1/3) of this water is intracellular!

IONIC COMPOSITION OF EXTRACELLULAR AND INTRACELLULAR FLUID

• Extracellular – What we measure in blood tests
• Na+ (Low sodium = hyponatraemic, High sodium = hypernatraemic)
• Cl-
• HCO3- - Buffer
• Intracellular
• K+ (Potassium) – Cardiac Arrest if high extracellular levels! (Hyperkalaemia)
• PO43- (Phosphate) – Used for many intracellular reactions
• Lots of Proteins

DIFFUSION AND OSMOSIS

• Diffusion
• The movement of MOLECULES in a solution from a high to low gradient
• Facilitated Diffusion – When diffusion occurs across a membrane, utilizing a carrier

protein (Ion Channels)

• Osmosis
• The movement of WATER across a cell membrane
• Nature likes things to be equal – equal concentrations on both sides of a

membrane

• Charged molecules cannot move across the cell membrane to equalize

concentrations

• Therefore, water moves across the membrane to equalize concentrations
• Water leaves the dilute solution to enter the more concentrated solution
• Makes the dilute solution more concentrated and the more concentrated

solution more dilute àà Concentrations equalize across the membrane

MOLARITY AND OSMOLARITY

• Molarity is a measure of the MOLES of a solution in a given volume
• Basically, how many moles there are in one litre
• Expressed in moles per litre (mol/L or M)
• In reality, when ionic compounds are dissolved in water they dissociate.
• Sodium Chloride (salt) is NaCl, when it is dissolved in water it splits into Na+ ions and Cl-

ions.

• Each ion exerts a force, we need to consider individually.
• This is Osmolarity, it considers the number of PARTICLES in a given volume
• Basically, how many particles there are in one litre
• 1 mol of NaCl dissolved in 1 litre will have a molarity of 1 mol/L but an osmolarity of 2

Osmol/L (splits into Na+ and Cl-, 2 particles)

• 1 mol of Glucose dissolved in 1 litre will have a molarity of 1 mol/L and also an
• smolarity of 1Osmol/L (it doesn’t split and remains 1 particle)

OSMOLALITY

• Molarity and Osmolarity
• Moles and osmoles per

VOLUME (Litres)

• Molality and Osmolality
• Moles and osmoles per WEIGHT (Kg)
• Osmolality technically more accurate, but physiologically speaking no

difference

• For purposes of Medicine: Osmolarity = Osmolality

TONICITY

• Tonicity is the ability of a solution to make water move in or out of it by osmosis
• This has implications for how water moves in and out of a cell
• Similar to Osmolarity, tonicity refers to the direction in which water would travel
• Think of tonicity as the affects of osmolarity!
• A hypertonic solution is a solution that is very concentrated, a hypotonic solution

is a solution that is dilute.

• If a cell is in a hypertonic solution, water will move out of the cell (Osmosis)
• If a cell is in a hypotonic solution, water will move into the cell (Osmosis)
• An isotonic solution is one in which the osmolarity of intracellular and

extracellular fluids are the same - no net movement of water.

MOVEMENT BETWEEN FLUID COMPARTMENTS ACCORDING TO OSMOSIS/TONICITY

• Extracellular and Intracellular Fluid are linked by Osmosis/Tonicity
• Alterations to Extracellular Fluid can result in changes to Intracellular Fluid –

we take advantage of this clinically.

• Water is lost from the Extracellular Fluid, with the Intracellular Fluid changing

according to what has been lost.

• If more salt than water lost – Hypotonic Dehydration
• Water ENTERS cells via osmotic pressure to equalize osmolarities across the cell

membrane

• If more water than salt lost – Hypertonic Dehydration
• Water LEAVES cells via osmotic pressure to equalize osmolarities across the cell

membrane

• This video summarises nicely –

tricky concept

TYPES OF DEHYDRATION

• Salt and Water Depletion (Isotonic Dehydration)
• Water and Salt are lost in equal measure à No change in concentration of Extracellular Fluid à No change in osmotic

pressure à No change in volume of Intercellular Fluid

• Water Depletion (Hypertonic Dehydration)
• More water than salt lost à Extracellular Fluid becomes more concentrated à Increased Osmolarity à Hypertonic Solution

à Water moves into Extracellular Fluid to compensate, from Intracellular Fluid à Decrease in Intracellular Volume à Cells Shrink

• Salt Depletion (Hypotonic Dehydration)
• More salt than water lost à Extracellular fluid becomes more dilute à Decreased Osmolarity à Hypotonic Solution à

Water moves out of Extracellular Fluid, into Intracellular Fluid à Increase in Intracellular Volume à Cells expand, risk of lysis

• Blood T

ests reveal which type:

• Normal Electrolyte Levels – Isotonic
• High Electrolyte Levels – Hypertonic
• Low Electrolyte Levels – Hypotonic

CLINICAL RELEVANCE – FLUIDS

• Isotonic Saline (0.9% Saline)
• Isotonic Dehydration
• Hypertonic Saline (>0.9% Saline)
• Hypotonic Dehydration
• Hypotonic Saline (<0.9% Saline)
• Hypertonic Dehydration

SBA PRACTICE QUESTION

• An 89

Year-Old woman is brought to an emergency department after falling at home and was found to have Hypertonic Dehydration. Which of the following will describe the changes to intracellular fluid following this type of dehydration?

• A) No Change in Intracellular Fluid

Volume

• B) Decrease in Intracellular Fluid

Volume

• C) Increase in Intracellular Fluid

Volume

• D) Intracellular Fluid will increase pH
• E) Intracellular Fluid will decrease pH

SBA PRACTICE QUESTION

• An 89

Year-Old woman is brought to an emergency department after falling at home and was found to have Hypertonic Dehydration. Which of the following will describe the changes to intracellular fluid following this type of dehydration?

• A) No Change in Intracellular Fluid

Volume

• B) Decrease in Intracellular Fluid

Volume

• C) Increase in Intracellular Fluid

Volume

• D) Intracellular Fluid will increase pH
• E) Intracellular Fluid will decrease pH

EXPLANATION

SBA PRACTICE QUESTION

• Following a severe bout of Diarrhoea and

Vomiting following food poisoning a patient is admitted to St. George’s A&E, blood tests reveal Isotonic Dehydration. What will the effects of this type of dehydration be to the intracellular fluid?

• A) No Change in Intracellular Fluid

Volume

• B) Decrease in Intracellular Fluid

Volume

• C) Increase in Intracellular Fluid

Volume

• D) Intracellular Fluid will increase pH
• E) Intracellular Fluid will decrease pH

SBA PRACTICE QUESTION

• Following a severe bout Diarrhoea and

Vomiting following food poisoning a patient is admitted to St. George’s A&E, blood tests reveal Isotonic Dehydration. What will the effects of this type of dehydration be to the intracellular fluid?

• A) No Change in Intracellular Fluid

Volume

• B) Decrease in Intracellular Fluid

Volume

• C) Increase in Intracellular Fluid

Volume

• D) Intracellular Fluid will increase pH
• E) Intracellular Fluid will decrease pH

EXPLANATION

ANY QUESTIONS????

ANATOMY OF THE KIDNEY

THE KIDNEY AND FLUID BALANCE (1)

The kidney is constantly weighing up what we do and don’t need. ¼ of your blood passes through your kidneys every minute. Water and other substances are filtrated, reabsorbed, secreted and excreted.

• Proximal tubule = ~65% water/NaCl

reabsorbed.

• Loop of Henle = ~25% water/NaCl

reabsorbed

• Distal tubule = ~5% water/NaCl
• reabsorbed. VARIABLE
• Collecting duct = ~5% water/NaCl
• reabsorbed. VARIABLE

THE KIDNEY AND FLUID BALANCE (2)

Countercurrent multiplication = takes place in the loop of Henle. It is the process of using energy to generate an osmotic gradient. This allows for reabsorption of water → concentrates urine. Stops you from producing tonnes of dilute urine! Tricky concept to get your head around, great video – https://www.youtube.com/watch?v=cYyJF_aSC6o

• Descending limb permeable to water. PASSIVE (does not

require energy)

• Ascending limb actively pumps Na+, K+ & Cl- ions out, it’s

impermeable to water. ACTIVE (requires energy)

• New tubular fluid enters the descending limb, which pushes

fluid at higher osmolarity down the tube

• The further you move down the medulla the interstitium

becomes more salty (hypertonic)

• Creation of an osmotic gradient, draws water out of the

descending limb and collecting duct

THE RAAS SYSTEM

This will make more and more sense over the year! The kidneys are a key part of the Renin-angiotensin- aldosterone system (RAAS) which is essential for maintaining blood pressure & volume.

• 1. ↓ Blood volume & pressure detected by

juxtaglomerular apparatus

• 2. Renin released which causes ↑ angiotensin I
• 3. This is converted to angiotensin II by the enzyme ACE
• 4. Angiotensin II has a wide variety of effects to ↑ blood

volume & pressure

LATER IN THE YEAR!

INTRODUCTION TO PHARMACOLOGY

Drug = a chemical that produces a biological effect Pharmacodynamics = the mechanism action, what a drug does to the body Pharmacokinetics = absorption, distribution, metabolism, excretion of a drug, what the body does to the drug. Receptor = a specific target molecule which a drug interacts with to produce a cellular response. Agonist = a drug which binds to a receptor to produce a biological cellular response. Has efficacy because it has a response!

• Full agonist – full efficacy
• Partial agonist – less efficacy

Antagonist = a drug which binds to a receptor but does not produce a biological effect. Does not have efficacy because it has no response!

THE AUTONOMIC NERVOUS SYSTEM

Somatic: the connections between your CNS and skeletal muscle. VOLUNTARY Autonomic: the connections between your CNS and peripheral organs. INVOLUNTARY Sympathetic ”fight and flight”

• Increased heart rate and contractility
• Increased BP
• Bronchodilation – more O2 required
• Dilation of pupils
• Increased sweating
• Increased blood to muscles / increased fuel

(breakdown glycogen/lipids) Parasympathetic ”rest and digest”

• Decreases HR
• Bladder/micturition response
• Increased GI tract motility/secretions
• Metabolic changes: insulin release, glucose uptake

and storage

• Bronchoconstriction – less O2 required

IMPORTANT TERMINOLOGY

Afferent neuron – travelling towards the CNS

• Somatic afferents = receive signals from skin/muscles/tendons/joints (e.g. touch and pain).
• Visceral (autonomic) afferents = receive signals from organs (e.g. blood pressure)

Efferent neuron – travelling away from the CNS

• Somatic efferents = send signals to skeletal muscles for movement. Voluntary
• Visceral (autonomic) efferents = send signals to organs. Involuntary
• “Fight or flight”
• “Rest and digest”

Ganglion - a group of neuronal cell bodies lying outside the CNS Pre-ganglionic nerve – neuron from CNS to the ganglion Post-ganglionic nerve – neuron from the ganglion to the peripheral organ

SYMPATHETIC VS PARASYMPATHETIC

Sympathetic NS Parasympathetic NS Length of preganglionic nerve Short Long Length of postganglionic nerve Long Short Location of ganglia Near spinal cord (paravertebral) Near target organ Pre-ganglionic neurotransmitter (receptor) Acetylcholine (Nic) Acetylcholine (Nic) Post-ganglionic neurotransmitter (receptor) Noradrenaline* Acetylcholine (Mus)

*In sweat glands it’s acetylcholine (mus) In adrenal medulla it’s acetylcholine (nic) Nic = nicotinic receptor Mus = muscarinic receptor

ANATOMICAL TERMINOLOGY

The anatomical position

• Body upright
• Palms facing forward
• Thumbs pointing away from body
• Head and eyes facing forward

Body axes

• Superior (cranial) /inferior (caudal)
• Rostral (towards the nose)

Caudal = tail

• Anterior (ventral)/ Posterior (dorsal).

Think Dorsal fin!

• Medial / lateral

ANATOMICAL TERMINOLOGY(2)

Body planes

• Coronal or frontal plane. Divides body into front

and back. A tiara style crown (corona), heavily decorated on front and bare at back

• Horizontal, axial or transverse plane. Divides body

into top and bottom.

• Sagittal plane. Saggitarius, an archer holds his bow in

the sagittal plane

• Midsaggital or median plane
• Parasaggital plane

ANATOMICAL TERMINOLOGY(3)

You’ll become familiar with a lot more terms throughout the year! Don’t feel like you need to learn them all this week

• Palmar / dorsal
• Plantar / dorsal
• Proximal (nearer the trunk)) / distal (further from trunk)
• Movements!

SBA PRACTICE QUESTION

A patient who has had profound diarrhea and vomiting following a dodgy Sam’s Chicken stands up from the floor after being sick all night and faints, banging their head on the door handle as they fall. They go to A&E and have a head CT scan as a precaution, seen below. What is the body plane that the below CT was taken in?

• A) Coronal
• B) Transverse
• C) Sagittal
• D) Oblique
• E) Side On

SBA PRACTICE QUESTION

A patient who has had profound diarrhea and vomiting following a dodgy Sam’s Chicken stands up from the floor after being sick all night and faints, banging their head on the door handle as they fall. They go to A&E and have a head CT scan as a precaution, seen below. What is the body plane that the below CT was taken in?

• A) Coronal
• B) Transverse
• C) Sagittal
• D) Oblique
• E) Side On

SBA PRACTICE QUESTION

A GEP Yr 1 Student is waiting to sit their February BCS exams and notices that they are surprisingly relaxed because they have attended all of the Studyhub GEP Yr 1 lectures and are prepared for their exams. Their friend however did not and is very nervous, with their sympathetic nervous system being activated. Which of the following would you NOT expect to see in the friend due to Sympathetic Nervous System activation?

• A) Increased Heart Rate (Tachycardia)
• B) Increased Blood Flow to Skeletal Muscles
• C) Dilation of the Pupils
• D) Narrowing of the airways (Bronchoconstriction)
• E) Opening of the airways (Bronchodilation)

SBA PRACTICE QUESTION

A GEP Yr 1 Student is waiting to sit their February BCS exams and notices that they are surprisingly relaxed because they have attended all of the Studyhub GEP Yr 1 lectures and are prepared for their exams. Their friend however did not and is very nervous, with their sympathetic nervous system being activated. Which of the following would you NOT expect to see in the friend due to Sympathetic Nervous System activation?

• A) Increased Heart Rate (Tachycardia)
• B) Increased Blood Flow to Skeletal Muscles
• C) Dilation of the Pupils
• D) Narrowing of the airways (Bronchoconstriction)
• E) Opening of the airways (Bronchodilation)

SBA PRACTICE QUESTION Which part of the nephron is responsible for the majority of water reabsorption?

• A) Distal Convoluted Tubule
• B) Proximal Convoluted Tubule
• C) Glomerulus
• D) Collecting Duct
• E) Ascending Limb of the Loop of Henle

SBA PRACTICE QUESTION Which part of the nephron is responsible for the majority of water reabsorption?

• A) Distal Convoluted Tubule
• B) Proximal Convoluted

Tubule

• C) Glomerulus
• D) Collecting Duct
• E) Ascending Limb of the Loop of Henle

EXTRA-SLIDES IF TIME IF NOT THEN USE THESE TO ANSWER THE RELEVANT LOBS IF YOU WANT J EXTRA-SLIDES IF TIME IF NOT THEN USE THESE TO ANSWER THE RELEVANT LOBS IF YOU WANT J

PASSIVE MOVEMENT VS ACTIVE TRANSPORT

• Learn Anthony Alberts lectures well, they will come up in the exams, even the introductory ones!
• Everything you need for them on the slides and he’s really good!
• Passive Movement/Transport
• The movement of molecules down a gradient (high to low)
• Pressure/Concentration/Osmotic Gradient Gradient
• This requires NO ENERGY
• Active Transport
• The movement of molecules against a gradient (low to high)
• This REQUIRES ENERGY (ATP) and the use of specialized pumps

MOVEMENT THROUGH THE MEMBRANE

• Cell Membranes are made of Phospholipids
• Hydrophobic Core
• Not everything can easily pass into the cell through the membrane
• Small/Hydrophobic molecules can easily pass through a cell membrane
• Small – Oxygen, Carbon Dioxide, Urea, Ethanol
• Hydrophobic – Glycerol, Steroid Hormones (estrogen, testosterone, cortisol)
• Large/Hydrophilic (polar) molecules cannot pass easily through a cell

membrane

• Large – Plasma Proteins, Peptide Hormones
• Hydrophilic (charged) – Electrolytes, Glucose, Amino Acids,

PRIMARY ACTIVE TRANSPORT

• Active Transport
• Requires energy to transport molecules against their concentration gradient.
• Often achieved via ATP Dependent pumps
• Carrier proteins which require ATP in order to transport ions against concentration

gradient

• VERY IMPORTANT in controlling intracellular and extracellular electrolyte balance
• When there’s no oxygen less ATP produced (anerobic respiration)
• Leads to less activity of ATP-dependent pumps
• Cannot maintain intracellular/extracellular electrolyte balances
• Leads to a breakdown in membrane potentials, heart and brain require membrane

potentials to function

• Why not breathing leads to death – cardiac arrest due to inability of ATP-

dependent pumps to generate cardiac membrane potential

SECONDARY ACTIVE TRANSPORT

• Secondary Active Transport
• Still requires energy but not ATP
• Utilizes other forms of energy to move a

molecule against it’s concentration gradient

• Utilize the existing electrochemical gradients to ‘hitch a

ride’

• Weird Concept – This video explains it well

SBA PRACTICE QUESTION

• Which of the following molecules is able to pass freely through the

phospholipid bilayer of a cell membrane?

• A) Haemoglobin
• B) K+
• C) Oxygen
• D) Cl-
• E) Glucose

SBA PRACTICE QUESTION

• Which of the following molecules is able to pass freely through the

phospholipid bilayer of a cell membrane?

• A) Haemoglobin
• B) K+
• C) Oxygen
• D) Cl-
• E) Glucose

THANK YOU! ANY QUESTIONS??

(FEEL FREE TO EMAIL US WITH ANY QUESTIONS)