PPP Flashcards

Question

What are the three main fluid compartments?

Answer 1

- Blood plasma - Intracellular space - Interstitial space

Answer 2

- 40% = intracellular space (~28L). - 15% = interstitial space (~10.5L). - 5% = plasma space (~3.5L).

Answer 3

- CSF - Aqueous and vitreous humors of the eye - Synovial fluid - Amniotic fluid (during pregnancy) - GI tract secretions - Lymph These spaces are all part of the extracellular space.

Answer 4

Dilution method = add a known amount of substance to an unknown volume and measure the concentration. Use this information to calculate volume.

Answer 5

To measure plasma volume the substances need to be large enough to not cross capillaries: - Evans Blue - Labeled Inulin - Albumin To measure ECS the substance must not be able to enter cells easily: - 24Na - Sucrose To measure TBW you need something that distributes with all water in the body: - 3H20 (heavy water).

Answer 6

Na, Cl and K Determine osmolarity.

Answer 7

The total number of freely diffusible entities in a solution.

Answer 8

~290mosmol/L

Answer 9

The osmotic pressure set by small diffusible ions such as Na, K and Cl in body fluids.

Answer 10

Because proteins are unable to travel through the plasma membrane they exert an oncotic/colloidal pressure of about 25mmHg. Oncotic pressure is vital for fluid transport across capillaries.

Answer 11

At the arterial end, the hydrostatic pressure is higher than the oncotic pressure so fluid will move out of the bloodstream into the surrounding tissues. At the venous end, the oncotic pressure is higher than the hydrostatic pressure which forces fluid back into the bloodstream.

Answer 12

- Na = 140mmol/L - K = 4mmol/L - Ca = 2mmol/L - Bicarbonate = 24mmol/L

Answer 13

- Na = 10mmol/L - K = 120mmol/L - Ca = ~100nmol/L

Answer 14

- Albumin (48g/L). Used in transport and pH buffering. - α, β and γ globulins (0.7-13 g/L each). Used in haemostasis (stopping the flow of blood), transport and immune system. - Fibrinogen (3g/L). Used in haemostasis.

Answer 15

Male = 5.5 x10^12/L Female = 4.8x10^12/L

Answer 16

4-11x10^9/L

Answer 17

Lymphocytes (20-40%) produce immunoglobulins. Monocytes (2-8%) migrate to tissues and form macrophages. Granulocytes: - Neutrophils = chemotactic, phagocytosis - Eosinophils = phagocytosis, allergy - Basophils = release histamine and heparin

Answer 18

They are fragments of megakaryocytes that are produced in the bone marrow. 150-400x10^9/L

Answer 19

Major role in haemostasis = they will move towards the broken endothelium and accumulate and release the contents of their granules which attracts more platelets. They also help maintain the coagulation of the blood at the site.

Answer 20

Pulmonary = ~16mmHg Systemic = ~92mmHg

Answer 21

- Pulmonary is in series with the systemic circulation. | - The systemic circulation is in parallel with itself.

Answer 22

Stroke volume x Heart rate

Answer 23

TPR = total peripheral resistance. This determines pressure load on the left side of the heart i.e. afterload.

Answer 24

The filling pressure of the heart which is determined by the central venous pressure (CVP).

Answer 25

Transport within the blood or air as a result of pressure differences.

Answer 26

Fick's law is used to calculate the rate of diffusion in a solution. Rate of diffusion = ΔC x A/Δx x solubility/√MW Where: - ΔC = difference in concentration of diffusing substance - A = area over which diffusion occurs - Δx = distance over which is has to travel

Answer 27

- Temperature - Solubility of the substance - Square root of the molecular weight of the substance

Answer 28

A/Δx * solubility/√MW

Answer 29

ΔC and permeability

Answer 30

Flow is proportional to the pressure difference and inversely proportional to the resistance to flow.

Answer 31

P1-P2/R - Darcy's law Difference in pressure divided by the resistance.

Answer 32

Resistance is an independent variable. This means that if either flow or pressure change, the resistance stays the same.

Answer 33

Poiseuille's law: R = 8VL/πr^4 Where: - L = length of tube - r = radius of tube - V = viscosity of fluid

Answer 34

A large change in resistance and therefore flow.

Answer 35

Viscous drag at the sides of the tube slows the fluid, so the fastest movement (flow) is in the centre.

Answer 36

Where, as a result of laminar flow, red blood cells align themselves in the centre of the vessel where the flow is the fastest.

Answer 37

The Fåhræus–Lindqvist effect describes how the viscosity of blood changes with the diameter of the vessel. There is a decrease in viscosity as the tube's diameter decreases. This is because erythrocytes move to the centre of the vessel, leaving only plasma near the wall of the vessel.

Answer 38

Where high velocity, sharp edges and branch points (such as plaques caused by atherosclerosis) can disrupt laminar flow leading to turbulence. This causes increased resistance and creates vibrations.

Answer 39

Distensible vessels are able to expand and contract in response to changes in pressure. - Pulmonary vessels - Cerebral vessels

Answer 40

Adding together the individual resistances.

Answer 41

1/total R = 1/R1 + 1/R2...

Answer 42

By regulating resistance. If blood pressure is kept constant, then the flow in certain tissues can be controlled by changing resistance and keeping other tissues in parallel unaffected.

Answer 43

Cardiac Output (CO) x Total Peripheral Resistance (TPR)

Answer 44

When the plasma membrane of a cell becomes positively charged (normally negatively charged).

Answer 45

Where a glass electrode is used to clamp patch of cell membrane that contains a single ion channel which allows you to measure the voltage of that channel.

Answer 46

1. The pump moves ions against their concentration gradient. 2. There is restricted ion movement through channels. 3. The membrane stores ionic charges on its inner and outer surfaces - it is a capacitor.

Answer 47

Voltage is the expenditure of energy (from ATP) used to move charge across a membrane i.e. to separate paired charged ions on either side of the membrane.

Answer 48

The point where the force of the concentration gradient pushing an ion out of the cell is matched by the electrical force pulling an ion back into the cell. There is no net movement and the electrical forces which exactly balances the osmotic force is called the equilibrium potential.

Answer 49

-70mV Na and K

Answer 50

Where the net movement of an ion is 0. This is also the membrane voltage that a cell needs to be at to prevent movement of that ion down its concentration gradient. This potential is very negative for K and very positive for Na.

Answer 51

Because the membrane is about 50x more permeable to K than Na.

Answer 52

Because the passive lead of K out is matched by the passive leak of Na in.

Answer 53

The ion will move down its electrochemical gradient and will drive the Vm towards the equilibrium potential for that ion.

Answer 54

Vm-Eeq Membrane potential minus equilibrium potential. The driving force tells us the voltage being used to move the ions either in or out of the cell. +ve forcing ions out -ve forcing ions in

Answer 55

E = RT/zF x Log([ion]o/[ion]i)

Answer 56

Vm = RT/F x log((Pion x [ion]o) + (Pion x [ion]o)) / ((Pion x[ion]i) + (Pion x [ion]i))

Answer 57

1. Vm goes from negative to positive = Na channels open and Na rushes in causing more Na channels to open. 2. Vm goes from positive to negative = K channels open slowly causing an efflux of K. 3. Overshoot where Vm goes too negative then gets a little less negative to reach the resting Vm.

Answer 58

- Triggered by depolarisation. - Threshold of depolarisation is required for an AP. - All or none. - Propagates without diminishing. - At its peak Vm approaches ENa. - After the AP the membrane is inexcitable due to the refractory period.

Answer 59

This allows Na to come into the cell very quickly i.e. faster than K is leaving the cell because the flow of K out can counteract the flow of Na in.

Answer 60

Charge (Q) (coulombs) = capacitance (C) x voltage (V).

Answer 61

So that the change in ions needed for an AP does not affect the overall concentration gradient across the cell and does not cause osmotic changes.

Answer 62

Where the strength of the AP decreases the further away you get from the stimulation site.

Answer 63

- Resistive = ions flow through channels. | - Capacitative = ion approaches one surface of the membrane and another is expelled from the other side.

Answer 64

Along nerves that are myelinated. The AP jumps between nodes of Ranvier (when one node is activated, the next node is almost instantaneously depolarised, small delay is present as the channels respond).

Answer 65

Causes the current to be forced through the axoplasm to the next node.

Answer 66

- Thinner axons lead to higher longitudinal axoplasmic resistance. - Lower membrane resistance leads to the current dissipating faster and voltage falling more rapidly. - Higher membrane charge stored means that the voltage across the membrane changes more slowly.

Answer 67

Where signal can be directly transmitted between cells without the need for a synapse. This happens in cardiac cells through intercalated discs.

Answer 68

The last site in the soma where membrane potentials propagated from synaptic inputs are summated before being transmitted to the axon.

Answer 69

1. Pre-synaptic cleft depolarises causing voltage-gated Ca channels to open causing a massive influx of Ca into the cell. 2. High Ca concentrations trigger ACh filled vesicles to fuse with the membrane and release their contents into the EC space. 3. The ACh then binds and opens ACh-gated cation channels. This channel allows Ca in and K out of the post-synaptic cell simultaneously.

Answer 70

The influx of Ca into the cell is much slower than that of K or Na.

Answer 71

They are the depolarisations of skeletal muscle fibres which produce a sub-threshold signal and therefore do not produce an action potential.

Answer 72

Directly beneath the pre-synaptic cleft and nowhere else along the muscle fibre.

Answer 73

When ACh channels are activated, some Na flows in and K out. The result of this is a small potential called the end-plate potential.

Answer 74

The opening of Na and K channels along the muscle fibre.

Answer 75

Where the strength of an AP gets weaker the further away from the initiation site you go.

Answer 76

Excitatory and inhibitory post-synaptic potentials. They are sub-threshold events which determine whether a neuron will reach threshold to fire an AP. EPSPs and IPSPs cancel each other out. They are make up of miniature end-plate potentials (MEEPs).

Answer 77

- Fatter t-tubules in cardiac muscle. - Dyads in cardiac and triads in skeletal muscle. - Larger mitochondria in cardiac cells.

Answer 78

Atrial, neonatal and avian heart cells.

Answer 79

Google answer.

Answer 80

The time during an AP where the cell is incapable of firing a new AP.

Answer 81

Because of the long refractory period preventing a new AP to be fired. The long APs prevent tetany (where APs summate and cause muscles to spasm) and protects against re-entrant arrhythmias.

Answer 82

Cardiac muscle requires Ca influx to initiate a contraction whereas skeletal muscle does not.

Answer 83

- Clusters of L-type Ca channels (also known as DHP receptors) are found on the t-tubules and are voltage-gated so open when the AP sweeps past. - There are Ca release channels found on the sarcoplasmic reticulum (also called ryanodine receptors). These channels open when bound to Ca. This is called calcium-induced calcium release.

Answer 84

Ryanodine receptors or 'foot proteins' because they are so large.

Answer 85

- Ca is taken back up into the sarcoplasmic reticulum via an ATP-driven pump called SERCA. - Remaining Ca is removed by the Na-Ca exchanger (Na goes in and Ca goes out).

Answer 86

When the L-type Ca channels on the t-tubules are voltage-activated, they physically remove a 'plug' from the ryanodine receptor which allows Ca to flow into the cell. This is why skeletal muscle contraction is not Ca-dependant.

Answer 87

1. Ca needs to bind to troponin C which pulls tropomyosin out of the way. 2. ATP provides the energy to allow the myosin head to release from actin and swing forwards.

Answer 88

It is a sigmoidal relationship. Affected by temperature, pH, drugs, inorganic phosphate.

Answer 89

Where the sarcomere length determines the force generated by the muscle fibres. There is an optimal length - too small and too long produces very little force.

Answer 90

It increases the Ca sensitivity (affinity for Ca to troponin C) and the maximally activated force.

Answer 91

The law represents the relationship between stroke volume and end diastolic pressure. The law states that the stroke volume of the heart increases in response to an increase in the volume of blood in the ventricles, before contraction (the end diastolic volume), when all other factors remain constant.

Answer 92

The Frank-Starling law of the heart.

Answer 93

It is an autoregulation method by which myocardial tension increases with an increase in heart rate.

Answer 94

It becomes negative i.e. force decreases with increasing frequency. This is due to down-regulation of SERCA, up-regulation of Na/Ca exchange and an elevation of intracellular Na. This causes more Ca extrusion between beats and less Ca cycling through the SR.

Answer 95

The autonomic nervous system, hormones and locally released substances. The GI tract's rhythmic contractions are initiated by pacemaker cells.

Answer 96

- Elongated shape. - Lack of striations. - Presence of dense bodies which anchor actin filaments. - Presence of endoplasmic/sarcoplasmic reticulum to store Ca. - Gap junctions. - Higher ratio of actic to myosin compared to striated muscle.

Answer 97

A physiologically active factor released by cells which typically acts locally and briefly on other cells.

Answer 98

Any regulatory substance released by cells acting in an autocrine or paracrine fashion.

Answer 99

- ANS - Autocoids - Local hormones - Vascular endothelium - Blood-borne substances

Answer 100

Smooth muscle contraction can be actively suppressed by inhibitory stimuli.

Answer 101

- Lumen - Endothelial cells - Tunica intima (internal elastic lamina) - Smooth muscle cells (tunica media) - Tunica adventitia (blood vessels if large enough, collagen, sympathetic nerves and fibroblasts)

Answer 102

- Angiotensin II, adrenaline (blood-borne) - Noradrenaline released by sympathetic nerves - Local hormones - Pressure/stretch

Answer 103

- Tissue metabolites (adenosine, K) - Flow causing endothelial cells to release NO - Local hormones

Answer 104

1. NA binds to α1 receptors activating phospholipase C via g-proteins. 2. Phospholipase C catalyses PIP2 -> DAG & IP3. 3. IP3 causing Ca to be released from the sarcoplasmic reticulum. 4. DAG opens a RGC (receptor-gated channel) on the membrane which non-selectively allows cations into the cell including Na and Ca causing the cell to depolarise. 5. The membrane depolarisation causing the voltage-gated Ca channel to open allowing more Ca into the cell.

Answer 105

Their activation allows Na into the cell which causes depolarisation and starts the contraction cascade.

Answer 106

1. NO diffuses straight into the cell and activates guanylate cyclase. 2. Guanylate cyclase catalyses the reaction GTP -> cGMP. 3. cGMP activates protein kinase G which phosphorylates K channels. 4. Outflux of K from the cell causes hyperpolarisation which closes voltage-gated Ca channels. 5. Protein kinase G also phosphorylates SERCA and PMCA (plasma membrane Ca ATPase) causing Ca to be pumped out of the cell.

Answer 107

1. Substances (including adrenaline and adenosine) binds to β1 adrenergic receptors activating adenylate cyclase. 2. Adenylate cyclase catalyses the reaction ATP -> cAMP. 3. cAMP activates protein kinase A which phosphorylates K channels. 4. Outflux of K from the cell causes hyperpolarisation which closes voltage-gated Ca channels. 5. Protein kinase A also phosphorylates SERCA and PMCA (plasma membrane Ca ATPase) causing Ca to be pumped out of the cell.

Answer 108

Phosphodiesterases

Answer 109

1. Increase in Ca causes Ca to bind to calmodulin (similar to troponin) which binds four Ca's to become activated. 2. Active calmodulin interacts with myosin light-chain kinase which is then activated. 3. Myosin becomes phosphoylated and cross-bridges form causing contraction.

Answer 110

Myosin dephosphorylation catalysed by myosin phosphatase.

Answer 111

1. Reduced levels of Ca reverse the contraction process. 2. Rho A activates Rho kinase which inhibits myosin phosphatase promoting contraction. Ca sensitisation. 3. NO via cGMP stimulates myosin phosphatase promoting relaxation. Ca densensitisation.

Answer 112

It is much slower compared to striated muscle which leads to a lower requirement for ATP synthesis so smooth muscle can remain contracted indefinitely and doesn't fatigue.

Answer 113

Where myosin phosphatase is acting on myosin while it is still bound to actin. This 'locks' the myosin and actin together to maintain contraction which does not require ATP. Myosin and actin eventually fall apart but this takes a very long time.

Answer 114

These are spontaneous oscillations found in visceral smooth muscle that are generated by either the smooth muscle cells themselves or are driven by pacemaker cells.

Answer 115

This is where each smooth muscle cell has a synaptic input which allows for finer control of the muscle. This is found in the iris, ciliary body and piloerector muscles of the skin.

Answer 116

This is where not all cells have synaptic input and excitation is spread through tissue by via gap junctions. This allows for co-ordinated contraction of many cells. This is found in the GI tract, genitourinary tracts, airways and most vasculature.

Answer 117

The ANS is the neuronal groups and fibre connections that control the activity of the heart, visceral organs, blood vessels and glands.

Answer 118

It maintains homeostasis by directly or indirectly facilitating the response of virtually every organ system to changing external and internal demands.

Answer 119

Digestion, excretion and visual accommodation. It promotes effects that are associated with relaxation. Its innervation and effects are less widespread.

Answer 120

They are mainly important for the ongoing control of the cardiovascular system and reflex responses to stressful situations. It controls the 'fright, fight and flight' response. Its innervation and effects are more widespread.

Answer 121

- Nerve originates in the CNS and the preganglionic nerve travels all the way to the ganglion which is in the tissue itself. - ACh is released at the synapse and binds to nicotinic receptors on the post-ganglionic nerve. - Post-ganglionic nerves also release ACh which bind to muscarinic receptors in the tissue causing a response.

Answer 122

- Nerve originates in the CNS and the pre-ganglionic nerve is short ending at the sypathetic chain where it synapses. - ACh is released which binds to nicotinic receptors on the post-ganglionic nerve. - The post-ganglionic nerves are long and travel to the tissues where noradrenaline is released and binds to adrenergic receptors (α or β) which cause a response.

Answer 123

1) Works in exactly the same way as the parasympathetic efferent pathway just the ganglion is located near the spinal cord not in the tissue. 2) Pre-ganglionic fibres travel to the adrenal medulla where they release ACh which binds to nicotinic receptors on the medulla. The medulla then releases noradrenaline and adrenaline into the blood which bind to adrenergic receptors (α or β).

Answer 124

G-protein coupled receptors.

Answer 125

1) M2 = found in cardiac tissue that causes a decrease in cAMP causing heart rate to decrease. 2) M3 = found in smooth muscle and glandular tissue causes and increase in IP3 and DAG which is important in contraction of visceral muscle.

Answer 126

They are non-selective cation channels that mainly admit Na and K leading to rapid cell depolarisation.

Answer 127

1) N1 = found in muscle. | 2) N2 found in ganglia.

Answer 128

Activates Gq which stimulates IP3/Ca2+ and DAG second messenger pathways which raises cellular [Ca2+]. Found post-synaptically.

Answer 129

Activates Gi which inhibits adenylate cyclase and consequently decreases cAMP. It is often located presynaptically and acts to decrease the release of noradrenaline.

Answer 130

All three subtypes activate Gs which causes and increase in cAMP.

Answer 131

- β1 = main cardiac subtype. Found post-synaptically. - β2 = main vascular and airways subtype. Found in non-synaptic sites. - β3 = mainly found in adipose tissue but are also important in the bladder.

Answer 132

Non-adrenergic, non-cholinergic transmission where nerves in the ANS conduct neurotransmission that is neither adrenergic or cholinergic.

Answer 133

1) Some post-ganglionic sympathetic fibres release neuropeptide Y and ATP along with NA which promotes vasoconstriction. 2) Some postganglionic parasympathetic fibre branches release NO and vasoactive intestinal peptide along with ACh which causes vasodilation.

Answer 134

Sympathetic = ejaculation. Parasympathetic = erection.

Answer 135

- Inhibition of the cardiac pacemaker (sinoatrial node) causing a decrease in heart rate, blood pressure and cardiac output. - Decreases the conduction velocity in the atrioventricular node. - Has a small direct effect on ventricular contraction. All mediated by the vagus nerve.

Answer 136

Even though there are cholinergic muscarinic receptors in blood vessels, normally there is no ACh in the blood so none of the receptors can be activated. The one exception are the blood vessels in the penis which cause erection.

Answer 137

When there is an increase in blood pressure: - Afferent nerve endings found in the arterial walls are stimulated by stretch which signals to the nucleus tractus solitarius (NTS) in the brainstem. - The NTS compares the increase in BP to a set point. As it is above the set point, it acts to: - Increases parasympathetic input to the heart. - Decreases sympathetic input to the heart, arteries and veins. - All of these effects cause BP to fall towards the set point.

Answer 138

- Bronchioles constrict. - Causes spontaneous contractions of the gut wall and relaxes the intestinal sphincters. - Contracts the detrusor muscle of the bladder and relaxes the external sphincter.

Answer 139

- Bronchosecretions (mucus). - Gastrointestinal (gastric acid, pancreatic enzymes). - Salivary glands (watery saliva). - Lacrimal glands (tears).

Answer 140

1) Causes focusing by contracting ciliary muscles which relaxes tension on the lens allowing it to thicken and shorten the focal distance. 2) Causes pupil constriction (miosis) by contracting the sphincter pupillae muscle in the iris.

Answer 141

It is a product of the reaction Acetyl CoA + Choline which is catalysed by choline acetyltransferase.

Answer 142

Acetylchonlinesterase is found on the post-synaptic cleft and breaks ACh down into choline and acetate. The choline is then taken up by the pre-synaptic cleft to be used to make ACh once more.

Answer 143

A long-lasting cholinesterase inhibitor called ecothiopate.

Answer 144

It prevents the stimulation of muscarinic receptors on the detrusor muscle by binding to and degrading SNAP-25 which prevents exocytosis of ACh and other neurotransmitters.

Answer 145

A complex network of plexuses (myenteric and submucosal) of sensory, motor and interneurons which form two layers within the walls of the GI tract.

Answer 146

1) Sympathetic nerves in the CNS. All drugs need to penetrate the BBB and effects are widespread. 2) Sympathetic ganglia. Because transmission is similar to all autonomic ganglia ( ACh mediated) the effects are widespread and non-specific. 3) Neuroeffector junction. This allows for specific targeting of receptors with minimal off-target effects.

Answer 147

1) Noradrenaline synthesis from tyrosine - can manipulate the synthesis pathway. 2) Storage of NA in vesicles in the post-ganglionic nerve. VMAT (vesicular monoamine transporter) mediates the controlled uptake of NA into vesicles. Can block this channel using Reserpine. 3) Release of NA from the vesicles. When the concentration of NA reaches a certain level, the α2 adrenergic receptor is activated and prevents further release. Clonidine is a α2 adrenergic receptor agonist. Uptake 1 is also present which takes NA up from the EC space back into the nerve. Cocaine blocks Uptake 1.

Answer 148

Tyrosine -> DOPA -> Dopamine -> Noradrenaline -> Adrenaline

Answer 149

4) Interaction with receptors. Agonists and antagonists for the α and β adrenergic receptors. 5) Transmitter inactivation. Uptake 2 channel is found in the post-synaptic tissue and takes up NA where it is metabolised in the tissue by COMT (catecholomethyl transferase). MAO (monoamine oxidase) added to the EC space will degrate NA before it has a chance to activate the receptors.

Answer 150

1) MAOA found in the CNS, liver, pulmonary vascular endothelium, GI tract and placenta. 2) MAOB found in the CNS and systemically in blood platelets.

Answer 151

1) Phenylzine = irreversible non-selective inhibitor that inhibits both MAO isoforms. 2) Moclobemide = short-acting MAOA selective inhibitor. 3) Selegiline = irreversible MAOB selective inhibitor. It is selective for dopamine so used in Parkinson's disease.

Answer 152

Tyramine is found in cheese, wine and yogurt and is normally degraded by MAO. However, if patients are taking MAO inhibitors tyramine will not be metabolised leading to a hypertensive crisis.

Answer 153

- Salbutamol = β2 adrenergic agonist. Treats asthma, premature labour. - Propanolol = non-selective β adrenergic antagonist. Treats hypertension, angina. - Prazosin = α adrenoceptor antagonist. Treats benign prostatic hypertrophy.

Answer 154

Drugs which mimic the action of endogenous sympathetic nervous system agents.

Answer 155

- Widespread = adrenaline and noradrenaline. | - Directly acting = phenylephrine (α), salbutamol (β).

Answer 156

They block sympathetic vasoconstrictor tone which decreases blood pressure.

Answer 157

They block sympathetic nervous input to the heart causing a decrease in force of contraction, frequency of contraction and vascular tone. This leads to decreased cardiac output and decreased blood pressure.

Answer 158

- Salbutamol = β2 agonist. Treats asthma, premature labour. - Atenolol = β1 antagonist. Treats hypertension, angina. - Prazosin = α1 antagonist. Treats hypertension. - Labetalol = α1/β antagonist. Treats hypertension.

Answer 159

Hypothalamus

Answer 160

They are salivary glands.

Answer 161

- Parasympathetic causes and increase in saliva secretion by vasodilation. Mediated via the chorda lingual nerve. - Sympathetic causes a decrease in saliva secretion by vasoconstriction and a viscous secretion rich in proteins.

Answer 162

Glycoproteins

Answer 163

Parietal/oxyntic cells

Answer 164

- Basal (fasting) - Stimulated (post-prandial) - Cephalic - Gastric - Intestinal

Answer 165

They release pepsinogen into the stomach which is converted into pepsin in the highly acidic environment. Pepsisn then goes on to digest proteins.

Answer 166

- Superficial epithelial cells - Mucous neck cells - Stem/regenerative cells - Parietal (oxyntic) cells - Chief/peptic cells - Endocrine cells

Answer 167

In gastric parietal/oxyntic cells. Their function is to form a channel which increases the surface area for HCl secretion into the lumen of the stomach.

Answer 168

Acetylcholine, histamine and gastrin.

Answer 169

- ACh is released at or near the basolateral surface of cells from post-ganglionic neurons = neurocrine mechanism. - Gastrin is released by G cells from the antral mucosa and first part of the duodenum into the bloodstream which carries the hormone to the parietal/oxyntic cells = endocrine mechanism. - Histamine is released from mast-like cells from the lamina propria of oxyntic (acid secreting/parietal) mucosa into extracellular fluid and subsequently diffuses to the parietal/oxyntic cells = paracrine mechanism.

Answer 170

- Food intake stimulates G-cells to secrete gastrin into the blood. - Blood takes gastrin back to the epithelium of the stomach where it binds to a receptor on a ECL cell (Enterochromaffin-like) which causes it to release histamine. - Histamine binds to a receptor on a parietal/oxyntic cell causing acid secretion.

Answer 171

By a negative feedback loop. When D cells in the stomach detect HCl, they release somatostatin which binds to a receptor on G-cells which stops the release of gastrin.

Answer 172

- Proteolytic enzymes - Bicarbonate - Amylase - Lipase

Answer 173

Secretin helps regulate the pH of the duodenum by: - Inhibiting the secretion of gastric acid from the parietal/oxyntic cells of the stomach. - Stimulating the production of bicarbonate from the ductal cells of the pancreas. - Stimulates bile production by the liver.

Answer 174

- Causes the gall bladder to contract. | - Causes the sphincter of Oddi to relax.

Answer 175

- Secretion of bile is an active process. - Secretion is independent of liver sinusoidal blood pressure. - Secretion occurs against a pressure gradient from bile ductules to vasculature.

Answer 176

It is an active mechanism involving Na/H pump on the apical membrane, Na/K ATPase on the basal membrane and the movement of water out of the cell as a result of extrusion of Cl and Na into the interstitial space.

Answer 177

- Normal = 3-10 mg/ml | - Jaundice = 18mg/ml

Answer 178

It is a cellular antioxidant.

Answer 179

Where you have the effects of jaundice without pain. This can be caused by an obstruction to the bile duct, increased bilirubin production or decreased bilirubin clearance.

Answer 180

- Various fats enter the cell in the form of micelles where they are processed by the SER. - Glycerol, short-chain and medium-chain fatty acids pass through the cell wall and straight into the vasculature. - Apoproteins from the RER associate with the other lipid droplets at the SER. - The golgi synthesises chylomicrons which are stored in vesicles and bud off from the cell where they travel to the lymphatic system.

Answer 181

The circulation of biliary acids, bilirubin, drugs or other substances from the liver to bile to the small intestine, absorption by the enterocyte (mainly ileum) and transport back to the liver in order to prevent high loss of bile salts in the stool.

Answer 182

1) Too much absorption of water from bile. 2) Too much absorption of bile acids from bile. 3) Too much cholesterol in the bile. 4) Inflammation of the epithelium.

Answer 183

- Vagus nerve stimulation causes an increase in the secretion of bile. - The splanchnic nerve causes vasoconstriction and decreases bile flow. -

Answer 184

Vasoactive intestinal polypeptide (VIP). Inhibition of VIP causes an increase of absorption. Serotonin inhibits net fluid and electrolyte reabsorption.

Answer 185

Secretin Bile salts

Answer 186

They act to increase bile flow.

Answer 187

It is a metabolic product of haemoglobin porphyrin, degraded in the reticuloendothelial system, conjugated with glucuronic acid in the liver and then secreted into the bile at very high concentrations.

Answer 188

The release of CCK and gastric inhibitory peptide (GIP) is triggered from duodenal mucosal cells. CCK stimulates the contraction of the gall bladder, flow of bile and secretion of pancreatic enzymes. GIP weakly inhibits gastric acid secretion, but its main role is to stimulate insulin secretion.

Answer 189

- Emulsification of lipid aggregates: Bile acids have detergent action on particles of dietary fat which causes fat globules to break down or be emulsified into smaller micelles. - Solubilisation and transport of lipids in an aqueous environment.

Answer 190

Increased gastrin serum concentrations caused by gastrin-secreting tumours found in the pancreas, duodenum or abdominal lymph nodes.

Answer 191

It is a Competitive inhibitor for H+ channels – competes with histamine and gastrin (mainly histamine). The drug is absorbed rapidly and degrades quickly – short half-life (2-3 hours). It is used to treat Zollinger-Ellison syndrome.

Answer 192

A secondary reactive hyperaemia (increase in blood flow following a temporary ischaemia.

Answer 193

An isotonic primary fluid (plasma-like electrolyte composition) is formed by acinar cells is then modified in the straited duct system by reabsorption of Na and Cl and secretion of K and HCO3. This is stimulated by acinar epithelial cells increasing intracellular Ca.

Answer 194

Acinar cells arranged as endpieces surround a small central lumen (acinus). This opens into an intercalated duct which in turn converges into large ducts. These open into the main excretory ducts that drain into the mouth.

Answer 195

The glycoprotein instrinsic factor.

Answer 196

A nerve plexus found within the middle circular and longitudinal muscle layers of the muscularis of the stomach. It coordinates contractions for churning food.

Answer 197

- They secrete mucous towards the oesophageal end. - The glands are tubular, highly branched and coiled with few or no peptic or oxyntic cells. - They secrete some electrolytes.

Answer 198

- They constitute 15-20% of total gastric mucosal area. - They secrete alkaline mucous juice and some electrolytes such as Ca, phosphate, bicarbonate, NaCl and KCl. - They have characteristic deep gastric pits. - They are the predominant cell type in the antrum of the stomach.

Answer 199

- They occupy the fundus and body of the stomach and comprise 75-80% of the total gastric mucosa. - They are the key site of gastric HCl secretion.

Answer 200

1) Isthmus = parietal/oxyntic and surface mucous cells. 2) Neck = parietal/oxyntic and mucous neck cells. 3) Base = chief/peptic cells and some endocrine cells.

Answer 201

They are simple columnar epithelium that secrete neutral carbohydrate-rich glycoproteins.

Answer 202

It is activated by sight, smell, taste and chewing of food. It is mediated by efferent impulses through vagus fibres to the stomach.

Answer 203

They are pyramidal shaped cells whose apical cytoplasm is packed with zymogen granules.

Answer 204

2-4% dispersed throughout the exocrine tissue.

Answer 205

- Bicarbonate to neutralise stomach acid. - Proteolytic enzymes. - Starch and glycogen, - Lipase to hydrolyse fat into glycerol and fatty acids.

Answer 206

Acid in the mucosa of the upper duodenum acts as a stimulus for secretin release. Secretin then triggers a large secretion of bicarbonate from the exocrine pancreatic ductules in an effort to neutralise the acid.

Answer 207

- CO2 from blood combines with H2O to form carbonic acid. - Carbonic acid dissociates into HCO3 and H. - HCO3 then diffuses and/or goes through the HCO3:Cl exchanger into the lumen of the pancreatic ducts.

Answer 208

They are propelled by peristalsis towards the pylorus, but because they are too large they are then refluxed backwards. This loop continues until the solids are reduced sufficiently in size to flow through the pylorus.

Answer 209

When a small amount of gastric juice is emptied from the stomach, chemo- and mechanoreceptors in the proximal and distal small intestine sense low pH, high content of calories, lipids, some amino acids or changes in osmolality. All of these factors will trigger a decrease in gastric emptying via neural and humoral signals including vagus nerve, secretin and CCK released from the duodenum into the bloodstream.

Answer 210

- Relax the proximal stomach. - Enhance contractions in the distal stomach (e.g. antral contractions). - Increase constriction of the pyloric sphincter, The net effect of this is to diminish the rate of gastric emptying.

Answer 211

A pattern of smooth muscle contractions that originate in the stomach and propagate through the intestines. This occurs during periods of fasting and is capable of passing indigestible solids through the pylorus that were unable to fit through shortly after consumption. The complex serves as a 'housekeeping' function to remove residual undigested material through the GI tract.

Answer 212

1) Smooth muscle quiescence lasting 45-60 mins. 2) 30 mins of peristaltic contractions progressively increasing in frequency from the stomach through to the small intestines. 3) 5-15 mins of rapid, evenly spaced peristaltic contractions. Here the pylorus remains open. 4) Short period between phase 3 and phase 1.

Answer 213

Gastric, biliary and pancreatic secretions. They probably aid the cleansing activity of the migrating motor complex and assist in preventing a build-up of bacterial populations in the proximal segments of the digestive tract.

Answer 214

A ganglia in the enteric nervous system that is found in the submucosal layer.

Answer 215

- Ensures fats aren't emptied into the duodenum faster than they can be emulsified by bile acids. - Ensures acidic chyme does not enter faster than neutralisation via pancreatic HCO3 and other secretions can occur. - Ensures that the rate of entry of other components does not exceed the ability of the duodenum to process components.

Answer 216

Where increased secretory and motor functions of the stomach lead to increased motility of the terminal part of the ileum and accelerate movement of chyme through the ileocecal sphincter.

Answer 217

Pancreatic enzymes

Answer 218

Intestinal enzymes in the mucosal surface.

Answer 219

They are intestinal glands that extend to the muscularis mucosae. They have generative and secretory functions.

Answer 220

They are glands found in the upper duodenum submucosa that secrete neutral or alkaline mucous into crypts in response to parasympathetic stimulation and feeding.

Answer 221

- Arteriole - Capillary network - Vein - Central lymphatic or lacteal vessel

Answer 222

Via a Na-sugar coupled uptake mechanism at the mucosal/apical surface. (SGLT1) Gradient is provided by Na K ATPase on the basolateral membrane. The sugar exits across the serosal membrane via a facilitated carrier (GLUT2).

Answer 223

Specific mucosal and basolateral carriers for amino acids are used with co-transport dependent on the Na gradient from the lumen to the cell. The structural specificity of the carrier systems allows neutral, acidic and basic amino acids to be absorbed.

Answer 224

They are primarily Na-independent transport proteins which provide nutrient supply for epithelial renewal especially during prolonged periods of starvation where muscle protein breaks down).

Answer 225

They are taken up into the cell in an acitve process driven by a H gradient via the H+/oligopeptide cotransporter PepT1. They are then hydrolysed into single amino acids by intracellular peptidases in the enterocyte.

Answer 226

A Na/H exchanger on the brush border (apical membrane).

Answer 227

- A - D - E - K

Answer 228

The vitamin B-complex group: - Thiamin (B1) - Riboflavin (B2) - Niacin (B3) - Pyridoxine (B6) - Folate (folic acid) - B12 - Biotin - Pantothenic acid - Vitamin C

Answer 229

Each vitamin has its own membrane transporter process for absorption across the enterocyte.

Answer 230

They are carried by micelles to the brush-border membrane of intestinal villi where they then leave the micelle and diffuse across the lipid bilayer into the enterocyte. Within the enterocyte they become incorporated into chylomicrons which travel via the lacteals to the bloodstream.

Answer 231

- Renin - Vitamin D - Erythropoietin - Prostaglandins - αKlotho

Answer 232

1) Renal corpuscle | 2) Tubule

Answer 233

The interface between the blood flowing through the glomerulus capillaries and the fluid in Bowman's capsule.

Answer 234

1) Fenestrated (leaky) capillary endothelium. 2) Basements membrane. 3) Tubular epithelium (podocytes). Layers go from the capillary lumen to the Bowman's space.

Answer 235

Nephrin and podocin.

Answer 236

1) Proximal covoluted tubule 2) Proximal straight tubule 3) Descending thin limb of Henle's loop 4) Ascending thin limb of Henle's loop 5) Thick ascending limb of Henle's loop 6) Distal convoluted tubule 7) Cortical collecting duct 8) Medullary collecting duct

Answer 237

- Cortical nephrons are in the majority and have a short loop of Henle. - Juxtamedullary nephrons make up only 15% of the nephrons and have very long loops of Henle that extend deep into the renal medulla. They are used for producing concentrated urine.

Answer 238

In the cortex.

Answer 239

Three cell types sandwiched together in the nephron. - Juxtaglomerular cells of the afferent arteriole which are specialised smooth muscle cells of the arteriole wall containing renin granules. - Extra-glomerular mesangial cell (lacis cells). - Macula densa (at the beginning of the distal tubule) is an area of large, closely packed epithelial cells lining cells facing afferent arterioles.

Answer 240

They secrete renin into the afferent arterioles.

Answer 241

Vasa recta

Answer 242

It is a passive process so is driven by osmotic gradients and pressures.

Answer 243

7kDa or less

Answer 244

Because the basement membrane in the filtration interface has a negative charge so anions are repelled.

Answer 245

Ultrafiltrate

Answer 246

Large proteins and any substances or drugs that bind to these proteins in the bloodstream.

Answer 247

The glomerular filtration rate = the volume of fluid filtered from the glomeruli per minute (ml/min).

Answer 248

- Starling forces - Surface area of filtration interface - Hydraulic permeability of capillaries

Answer 249

The opposing hydrostatic (forcing filtration) and colloid osmotic/oncotic pressures (opposing filtration) that drive filtration in the glomerulus.

Answer 250

Constricting the afferent arterioles and dilating the efferent arterioles will cause a decrease in GFR. The converse of this will lead to increased GFR. This is controlled by sympathetic innervation of mesangial cells.

Answer 251

125ml/min (180L/day)

Answer 252

Proximal convoluted tubule and proximal straight tubule.

Answer 253

They have a brush border.

Answer 254

Na-coupled co-transporters which is a tubular maximum system. Found on the lumenal/apical membrane of the proximal tubule.

Answer 255

- Organic acids (anions) - Organic bases (cations) These include endogenous molecules (bile salts etc.), drugs and diagnostic agents.

Answer 256

1) The organic anion (OA-) enters the cell in exchange for dicarboxylate (DC-) through organic anion transporters (OAT1/3). 2) DC- accumulates in cells by metabolism and Na-coupled cotransport. 3) OA- enters the tubule lumen and the urine via an ATP-dependent transporter on the apical membrane.

Answer 257

1) They enter the cell via facilitated organic cation transporters (OCT2). 2) They enter the tubule lumen and the urine via multidrug and toxin extrusion proteins (MATEs) antiporter in exchange for H and/or OCTN.

Answer 258

The volume of plasma that is cleared of a substance in a given time.

Answer 259

U x V / P Where:: U = concentration in urine V = volume of urine/min P = concentration in plasma

Answer 260

Because it is: - Freely filtered - Not reabsorbed - Not secreted - Not metabolised - Easily measured

Answer 261

Creatinine

Answer 262

1) It is reabsorbed 2) There is no reabsorption or secretion 3) There is secretion

Answer 263

Where the clearance of a substance that is completely secreted and not reabsorbed is used to calculate renal plasma flow. This is an underestimation of the total renal flow.

Answer 264

The total renal blood flow in ml/min: Blood flow = (plasma flow)/(1-heamatocrit)

Answer 265

In mosm/kg it is a measure of water concentration. It is independent of temperature.

Answer 266

Substance plasma concentration (mmol/l) x GFR (l/min) = amount filtered (mmoles/min)

Answer 267

- None in the descending limb. | - Passive reabsorption in the thin ascending limb.

Answer 268

In an active process. - Na is taken in via transporters on the apical membrane of the tubule epithelium = NHE3 (Na/H exchanger 3) and Na/nutrient (X-) symporter. - Absorption of Na leaves a negative charge in the lumen which drives Cl- towards to basolateral membrane between the cells not through them. Water follows Cl. - Na leaves the tubule epithelium via the Na/K ATPase on the basolateral membrane.

Answer 269

- A Na/K/2Cl cotransporter brings Na into the cell. This influx is maintained by a K channel transporting K out of the cell into the lumen down its concentration gradient. - With K being transported out of the cell into the lumen, this makes the lumen a positive area. This repels Na and allows it to move to the basolateral side between the cells along with other positively charged ions including Ca and Mg. - Na is then transported out of the cell via the Na/K ATPase on the basolateral membrane.

Answer 270

- Na/Cl cotransporter brings Na into the cell from the lumen. - Na/K ATPase brings Na out of the cell on the basolateral membrane.

Answer 271

Principal cells are responsible for Na reabsorption: - ENAC is present on the apical membrane and brings Na into the cell. This leaves a negative environment in the lumen which drives Cl to the basolateral membrane between the cells. - Na/K ATPase on the basolateral membrane transports Na out of the cell.

Answer 272

Decrease in Na concentration in the lumen causes a decrease in local osmolarity. The increase in Na in the insterstitial fluid is conversely causing an increase in osmolarity which allows water to travel from the lumen to the basolateral membrane via: - AQP1 (aquaporin 1) channels on the apical membrane of the tubule epithelium. - Through tight junctions as they have high water permeability.

Answer 273

- Separate Na and water reabsorption. - Generate a renal medulla interstitial fluid with high osmolarity to drive water reabsorption. Occurs in the loop of Henle.

Answer 274

It reabsorbs more salt (25%) than water (10%). This is achieved by: - In the ascending limb, there is Na reabsorption but no water reabsorption because because the membrane is impermeable to water. - In the descending limb, there is a small amount of passive secretion of NaCl and it also reabsorbs water because AQP-1 channels are expressed.

Answer 275

1) Fill loop of Henle with a fluid of 300mOsmol/l. 2) Activate the Na transporters in the ascending limb which changes the osmolarity here to 200 and the interstitial fluid to 400mOsmol/l. 3) Water reabsorption occurs in the descending limb in order to equibrilate the interstitial fluid. 4) Because of the counter-current flow, the higher osmolarity high Na concentration fluid in the descending limb travels to the ascending limb leading to more Na being reabsorbed. Water reabsorption in the descending limb is also happening to maintain equilibrium. 5) The fluid leaving the loop of Henle has a very low Na concentration which makes it hypo-osmotic to plasma. This creates a gradient of increasing osmolarity of interstitial fluid that gets more and more concentrated the further down into the medulla.

Answer 276

They are shaped in the same way as the loops of Henle and are capable of supplying blood without washing away the medullary interstitial osmolarity gradient produced here.

Answer 277

- In the descending part of the vasa recta, solutes (mainly Na and Cl) are being reabsorbed and water is being secreted increasing the osmolarity of the plasma. - In the ascending part, the opposite is occuring leading to a decreased osmolarity of plasma. This action mimics that of the medullary interstitial gradient so it is not lost.

Answer 278

1) In the proximal tubule by passive reabsorption (50%). 2) In the loop of Henle by apical secretion via urea transporters UT-A2 (60% secreted). 3) In the inner medullary collecting duct by apical reabsorption via UT-A1 and UT-A3 on the basolateral membrane (70% reabsorbed). 40% of the filtered urea is excreted (dependent on hydration levels).

Answer 279

The concentration of non-penetrating solutes only (can't pass through the membrane).

Answer 280

Thick ascending limb and the distal tubule.

Answer 281

It is controlled by ADH/vasopressin. - Released by the pituitary and circulates the blood. - Interacts with V2 receptors on the basolateral membrane which is a g-protein coupled receptor so triggers a cAMP cascade. - This causes AQP2 to travel from the cytosol and insert itself into the apical membrane allowing for water reabsorption. Water moves out via AQP3&4 on the basolateral membrane. This increase water permeability in the collecting duct.

Answer 282

>300 mosmoles/L

Answer 283

Decreased urine production (less than the obligatory water loss of 0.428L of urine per day).

Answer 284

<300 mosmoles/L

Answer 285

Excessive production of urine.

Answer 286

The rate at which plasma is cleared of solute only by the kidneys OR the imaginary urine flow that would have resulted in a urine which was isomolar (same molarity) to plasma.

Answer 287

Cosm (ml/min) = Uosm x V / Posm Where: - V = urine flow rate (ml/min) - Uosm = Urine osmolarity (mosm/ml) - Posm = Plasma osmolarity (mosm/ml)

Answer 288

It reflects the ability of the kidneys to excrete dilute urine or concentrated urine and is used to assess renal function.

Answer 289

Ch20 (ml/min) = V - Uosm x V / Posm Where: - V = urine flow rate (ml/min) - Uosm = Urine osmolarity (mosm/ml) - Posm = Plasma osmolarity (mosm/ml)

Answer 290

- CH20 > 0 indicates a hypo-osmotic urine i.e. dilute urine. - CH20 = 0 indicates an isosmotic urine with respect to plasma. - CH20 < 0 indicates a hyper-osmotic urine i.e. concentrated urine.

Answer 291

2-3 ml/min

Answer 292

-1.3 - 14.5 ml/min

Answer 293

Osmoreceptors near the hypothalamus. They cause an increase or decrease in ADH secretion in the posterior pituitary.

Answer 294

- OVLT (organum vasculosum lamina terminalis). - MPN (median preoptic nucleus). - SFO (subfornical organ).

Answer 295

To magnocellular neurosecretory cells in the paraventricular (PVN) and supraoptic (SON) nuclei in the hypothalamus.

Answer 296

Because it causes rapid constriction of arterioles elevating total peripheral resistance.

Answer 297

- Alcohol inhibits ADH. | - Nicotine, pain, stress and nausea all stimulate ADH.

Answer 298

- Polyuria - Thirst (polydipsia) - Nocturia (getting up in the night to urinate)

Answer 299

1) Neurogenic where there is no ADH secreted which can be either a) congenital (present from birth) or b) as a result of trauma or brain tumour. 2) Nephrogenic can either be a) inhertied (mutated V2 receptor or AQP2 channel) or b) acquired (infection or side effect of a drug such as lithium).

Answer 300

Increased urination due too small molecules (e.g. glycerol, mannitol and excess glucose) present in the renal tubule lumen. This is typical of untreated diabetes mellitus.

Answer 301

- Increased blood glucose leads to an increase in the glomerular filtration of glucose which in turn increases the osmolarity of the filtrate. - Increased osmolarity filtrate causes a decrease in water reabsorption from the proximal tubule. The later portions of the nephron are unable to compensate for this so you have higher amounts of water in the urine.

Answer 302

~65% is reabsorbed passively at the proximal tubule. It travels from the lumen to the basolateral membrane passively following the concentration gradient. There is a low K concentration in the interstitial space because of the Na/K ATPase constantly pumping K into the cell in exchange for Na.

Answer 303

- 30% in the thick ascending limb via the NKCC2 transporter on the apical membrane. - 5% in the distal tubule via the K/H exchanger.

Answer 304

There is slight K reabsorption in the intercalated cells of the collecting duct, but this is outweighed by secretion of K through the principal cells. This occurs via ROMK (renal outer medullary K channel) and BK (Ca-activated big-conductance K channel) both on the apical membrane.

Answer 305

Because changes to ENaC affects the electrochemical potential driving K secretion through the K channels. The movement of Na out of the lumen makes the environement negative which supports the flow of positive K into the lumen.

Answer 306

Aldosterone works by increasing the activity of the Na/K ATPases leading to more K being brought inside the cell, increasing the activity of ENaC so more Na is brought into the cell and encourages the activity of the apical K channels.

Answer 307

High flow washes away the positive ions in the lumen which creates an environment that encourages movement of K out of the cell.

Answer 308

- Acidosis inhibits it because high H concentration leads to a positive environment which discourages secretion. - Alkalosis enhances it because there are less H ions in the lumen which leads to a more negative environment which encourages secretion.

Answer 309

Low plasma K concentrations (<3.5mM). It is caused by: - Increased external losses by hyperexretion of the kidneys, GI tract or skin (burns/intense sweating). - Redistribution into cells. - Inadequate K intake.

Answer 310

- Higher tubular flow rates increasing K secretion and excretion. - Hyperaldosteronism stimulating K secretion and excretion.

Answer 311

H ions that are bound to intracellular proteins acting as buffers will leave cells in order to return plasma pH to normal. K takes its place.

Answer 312

- Excess insulin in the body leads to insulin binding to its receptor which causes Na/K ATPase to be simulated which brings K into the cell causing hypokalaemia.

Answer 313

Because the resting membrane potential is set by K, in hypokalemia the RMP becomes more negative (hyperpolarised) which means that nerves have to be depolarised more to reach threshold for AP firing. Repolarisation is also slower so cells will stay closer to threshold for longer. This causes delayed APs which leads to muscle weakness etc.

Answer 314

K inactivates cAMP which is the second messenger for stimulating AQP2 to insert into the apical membrane and reabsorb water. Hypokalemia means higher intracellular K.

Answer 315

When the plasma K concentration is higher than 5.5mM. It is caused by: - Decreased external losses (renal failure, hypoaldosteronism, action of drugs). - Redistribution out of cells in alkalosis and tissue destruction.

Answer 316

Resting membrane potential is shifted closer to threshold for action potential firing (depolarises excitable cells).

Answer 317

- Short = Ca administered to antagonise the effects of K on the heart muscle. - Intermediate = insulin administered to bring K into cells and glucose to prevent hypoglycaemia. - Long = increase K secretion with diuretics or treat for renal failure.

Answer 318

285-295 mosmol/kg

Answer 319

In the principal cells of the collecting duct.

Answer 320

Causes us to feel thirsty making us drink more water to counter the dehydration.

Answer 321

The total amount of Na in ECF.

Answer 322

Plasma volume

Answer 323

By regulating two factors: 1) Na filtration (by affecting GFR). 2) Na reabsorption.

Answer 324

To maintain arterial blood pressure by controlling GFR.

Answer 325

To protect renal capillaries from hypertensive damage and maintaining a healthy GFR. Also called autoregulation.

Answer 326

The activation of baroreceptors which are part of the sympathetic nervous system. These high pressure stretch receptors are found in the carotid sinus and aortic sinus.

Answer 327

When blood pressure falls, the baroreceptors trigger activation of the sympathetic nervous system which causes vasoconstriction at the renal afferent arteriole and it reduces the surface area of the filtration barrier via mesangial cells. These actions decrease GFR so Na is conserved increasing BP.

Answer 328

1) A myogenic response by the renal smooth muscle cells that surround arterioles (e.g. vasoconstriction in response to stretch mediated through stretch-activated Ca channels). 2) Tubuloglomerular feedback by the juxtaglomerular apparatus. This controls vasoconstriction and renin release.

Answer 329

90-200 mmHg

Answer 330

a) Dilate | b) Constrict

Answer 331

1) Tubular fluid NaCl concentration receptors within the macula densa. 2) Pressure receptors in the central arterial tree. 3) Pressure receptors in renal afferent arterioles (intrarenal baroreceptors). 4) Volume receptors in cardiac atria and intrathoracic veins.

Answer 332

1) Renal sympathetic nerves stimulating renin release. 2) Direct pressure on the kidney which affects renin release. 3) Renin/angiotensin II/aldosterone all stimulate Na reabsorption. 4) Atrial natriuretic peptide causes natriuresis and inhibits Na reabsorption via ENAC. 5) Dopamine causes natriuresis and inhibits Na reabsorption.

Answer 333

By stimulating renin release.

Answer 334

Where increased NaCl to the macula densa will lead to an increased formation of adenosine which through A1 receptors causes an increase in calcium that causes the afferent arteriole to contract inhibiting renin release.

Answer 335

1) Decreased Na delivery to the macula densa. 2) Decrease in wall tension in the afferent arteriole (caused by intrarenal baroreceptors or granular cells of the juxtoglomerular apparatus). 3) Sympathetic activity. 4) Low blood volume (hypovolemia).

Answer 336

- Plasma angiotensinogen is broken down into angiotensin I. - Angiotenin I is converted into angiotensin II by a converting enzyme ACE. - Angiotensin II is what causes the widespread effects.

Answer 337

It stimulates proximal tubule Na reabsorption by binding to AT1 receptors on the apical and basolateral membranes. Activity of NHE3 on the apical membrane and Na K ATPase on the basement membrane are stimulated. This increases plasma volume and blood pressure.

Answer 338

By binding to receptors on OVLT, MPN and SFO. These receptors also cause thirst.

Answer 339

It is released from the zona glomerulosa in the adrenal cortex by angiotensin II.

Answer 340

- Sweat glands - Salivary glands - Gut

Answer 341

Increased plasma K concentration.

Answer 342

See flow chart slide 43 lecture 20 (Kidney function IV).

Answer 343

When the heart is stretched due to an increased in blood volume.

Answer 344

1) A type secreted from atrial myocardium. | 2) B type secreted form ventricular myocardium.

Answer 345

An increased secretion of Na in the urine.

Answer 346

1) Natriuretic: they act on the collecting duct cells to inhibit Na entry through ENaC, inhibit renin release and aldosterone production. This works with dopamine to inhibit Na, K ATPases activity in the proximal tubule. 2) Diuretic: inhibits ADH release. 3) Hypotensive: decreases blood pressure by systemic vasodilation and increases GFR by dilating afferent arterioles.

Answer 347

They cause an increase in their production by 40-80mmol/day.

Answer 348

The use of bicarbonate to take up the H ions and produce CO2. This increases breathing rate expelling CO2. This is very effective but you will eventually run out of bicarbonate.

Answer 349

They can reabsorb bicarbonate and rid the body of excess H+ (urine has a high pH range allowing for acidity).

Answer 350

- Proximal tubule (80%) - Ascending loop of Henle (15%) - Cortical collecting duct (intercalated cells type A) (5%).

Answer 351

H2O and CO2 combine to form H2CO3 (carbonic acid) catalysed by carbonic anhydrase II. This then breaks down to form bicarbonate which is reabsorbed on the basolateral membrane and H+ which is secreted.

Answer 352

- NA-H countertransporters - H-ATPase pumps - H, K ATPase pumps

Answer 353

It binds to bicarbonate and forms H2CO3 and therefore CO2 and H20 which both travel back into the tubular epithelial cells. The H+ is not excreted.

Answer 354

It will combine to form dihydrogen phosphate (H2PO4-) and is then excreted.

Answer 355

It is transported into the epithelium from the filtrate through Na/glutamine cotransporter and from the interstitial fluid through a glutamine amino acid exchanger (LAT2). Once inside the cell it splits to form bicarbonate (which is reabsorbed) and NH4+ (which is secreted through a Na/NH4+ exchanger).

Answer 356

It responds to changes in arterial pCO2, pO2 and H+ concentration which causes it to adjust ventilation to retain or expel CO2. This change works within minutes.

Answer 357

Acidosis = pH < 7.35 Alkalosis = pH > 7.45

Answer 358

Respiratory = increase and decrease of pCO2. Metabolic = increase and decrease in the amount of HCO3-.

Answer 359

- Drug-induced respiratory depression (narcotics and barbituates). - Airway obstruction (asthma).

Answer 360

- Airway obstruction (COPD) - Lung damage (fibrosis) - Chest wall disorders (pectus carinatum) - Neuromuscular disorders (ALS)

Answer 361

- More H+ is secreted in the urine forming a highly acidic urine. - More HCO3 is reabsorbed. - More glutamine is found in the blood in an attempt to form more bicarbonate.

Answer 362

Bicarbonate deficit and elevated H+.

Answer 363

Renal tubular acidosis (affecting the kidneys) and diarrhoea.

Answer 364

- Exogenous acid - Abnormal lipid metabolism - Abnormal carbohydrate metabolism - Normal protein metabolism

Answer 365

- Excessive central respiratory drive (aspirin overdose, fever, brainstem damage). - Hypoxic stimulation (response to altitude, hyperventilation, pulmonary embolism).

Answer 366

It reduces H+ secretion into the filtrate which causes more bicarbonate to be excreted in the urine. These are small changes.

Answer 367

- Repeated vomiting/loss of gastric acid. - Excess aldosterone (hyperaldosteronism stimulates tubule H+, ATPase). - Excess alkali ingestion (citrate/lactate are metabolised to bicarbonate).

Answer 368

In the intercalated cells type B of the collecting duct, bicarbonate is secreted into the filtrate by a Cl- exchanger called Pendrin on the apical membrane.

Answer 369

Presence of aldosterone.

Answer 370

Acidosis = increases glutamine production. Alkalosis = decreases glutamine production.

Answer 371

In the deep parts of the crypts found in the epithelium.

Answer 372

It contains a large amount of short-chain fatty acids which helps keep down pathogenic strains.

Answer 373

- Counter-transport in exchange for H+ (proximal bowel). - Co-transport with amino acids, monosaccharides (jujenum). - Co-transport with Cl (ileum).

Answer 374

Restricted movement through ion channels.

Answer 375

Transport is due to an electrical potential created by the Na transport. The high concentration of ions in the IC space causes the fluid there to be hypertonic.

Answer 376

1) Congenital (deficiency of normal ion transport system). 2) Due to bacterial infection of the gut (e.g. cholera). 3) Osmotic (where osmotic gradient across gut epithelium is reversed).

Answer 377

It permanently activates adenylyl cyclase which elevates cAMP in the crypt cells. This enhances the secretion of Cl (through CFTR) and blocks the H, Na exchanger. This together increases the amount of Cl and Na in your gut lumen which causes water to go into the lumen.

Answer 378

- Laxatives - Broad spectrum antibiotics - Hypermotility of the intestine - gut doesn't have a chance to absorb the nutrients it needs

Answer 379

1.5kg ~100 trillion bacteria

Answer 380

- Synthesise and excrete vitamins inc. vitamin K. - Protect against invading bacteria. - Stimulates the production of cross-reactive antibodies. - Stimulates the development of certain tissues, including cecum and lymphatic tissue. - Breaks down fibre. - Produces short-chain fatty acids.

Answer 381

- Regulates gut hormone release. - When absorbed can be used as an energy source. - Can influence food intake and insulin sensitivity. - Prevents osmotic diarrhoea.

Answer 382

Blood vessels and nerves supplying the muscle fibres (the neurovascular bundle).

Answer 383

Myofibrils

Answer 384

Within the sarcolemma.

Answer 385

Where repeating series of networks of sarcoplasmic reticulum meet.

Answer 386

They are plasma membrane (sarcolemma) invaginations.

Answer 387

Because they do not have such an extensive sarcoplasmic reticulum.

Answer 388

It is a molecule that extends from the Z-line of a sarcomere along the length of one thin actin filament. It acts like a template for the regulation of the actin filament.

Answer 389

It is a molecule that extends from the Z-line to the M-line of a sarcomere. It is closely associated with myosin and maintains the central position of the thick myosin filaments in the sarcomere.

Answer 390

It generates a passive tension through elastic extension when the sarcomere is stretched.

Answer 391

a) Contracted stage where filaments interdigitate and muscle shortens causing flexion. b) Stretched stage where thick and thin filaments do not interact. Also called isotonic. c) Where you increase tension but there is no change in sarcomere length.

Answer 392

1) ACh is released from the motor end plate which binds to voltage-gated Na channels opening them. 2) Na enters the cell causing depolarisation to spread over the plasma membrane including the t-tubules. 3) Ca is released into the sarcoplasm which then binds to troponin. 4) Tropomyosin changes its conformation allowing the myosin head to attach causing contraction of the muscle.

Answer 393

The presence of ATP, ADP and phosphate and then the loss of ADP.

Answer 394

They are slow-twitch oxidative (rely on aerobic respiration) fibres. They allow for sustained contraction (e.g. posture) and are fatigue resistant. They have the slowest speed of development of maximum tension.

Answer 395

They are fast-twitch oxidative and glycolytic (rely on anaerobic respiration but can be trained to use oxidative) and are used for phasic movements such as walking. They are fatigue resistant. They have a medium speed of development of maximum tension.

Answer 396

They are fast-twitch glycolytic muscles that are used for phasic movements including jumping and fast movements. They have the fastest speed of development of maximum tension but are easily fatigued.

Answer 397

The tension a muscle can generate is related to the number of crossbridges formed between the thick and thin filaments. Little tension is formed at the two extremes of length and there is optimum length which produces the most tension (2-2.3µm).

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