PPP Flashcards

1
Q

What is nebulin?

A

Molecule that extends from Z band along the length of one thin actin filament

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is titin?

A

Associated with myosin filaments extending from Z disk to M line

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is concentric contraction?

A

Contraction stage with an increase in the interdigitation of the filaments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is eccentric contraction?

A

Stretched stage where I and H bands are wide. Thick and thin filaments do not interact

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How is contraction of skeletal muscle initiated?

A

ACh binds to nicotinic receptor at motor end plate; depolarisation spreads into T-tubules –> DHP is activated –> RyR are linked and activated –> release of Ca2+ from sarcoplasmic reticulum; Ca2+ binds to troponin –> change in tropomyosin allowing myosin heads to attach –> contraction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How is extracellular space defined?

A

Plasma + interstitial space

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How is total body water distributed?

A
Plasma space (5% bw; 3.5 L)
Interstitial space (15% bw; 10.5 L)
Intracellular space (40% bw; 28 L)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the amount of CSF in the body?

A

Around 150 ml

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What substances are used to measure fluid compartments?

A

Plasma volume: albumin, evans blue, labeled inulin
ECS: 24Na, sucrose
TBW: 3H20

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the difference between osmolarity and osmolality?

A

Osmolarity: 1 osmole per liter
Osmolality: 1 osmole per kg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the osmolarity of plasma?

A

290 mosmol/l

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is crystalloid osmotic pressure?

A

Due to small diffusible ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the ionic composition of plasma and intracellular compartment?

A
Na+: 140 mM and 10 mM
K+: 4 mM and 120/140 mM
Ca2+: 2 mM and around 100 nM
Cl-: 110 mM
bicarbonate: 24 mM
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Which are the plasma proteins?

A

Albumin: oncotic pressure of around 25 mmHg
Alpha, beta and gamma globulins
Fibrinogen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the count of RBCs and Hb?

A

RBCs: 5.5/4.8 x 10^12 per litre
Hb: 160/140 g per litre

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the total WBCC?

A

4-11 x 10^9 per litre
Lymphocytes (20-40%)
Monocytes (2-8%)
Granulocytes: neutrophils (50-70%), eosinophils, basophils

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the total number of platelets?

A

150-400 x 10^9 per litre

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the normal MCV?

A

85 fL

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are the average pressures in the pulmonary and systemic circulation?

A

Pulmonary: 16 mmHg
Systemic: 92 mmHg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is Fick’s law?

A
Rate of diffusion depends on:
1. Area
2. Difference in concentrations
3. Distance over which it has to travel
How easily it diffuses depends on:
1. Temperature
2. Solubility
3. Square root of molecular weight
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is Darcy’s law?

A

Flow = (P1-P2)/R

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is Poiseuille’s law?

A

R = 8VL/pir^4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is the Fahraeus-Lindqvist effect?

A

Axial streaming due to laminar flow reduces viscosity of blood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

How is Rtotal calculated in series and in parallel?

A

Series: Rtotal = R1 + R2 +…
Parallel: 1/Rtotal = 1/R1 + 1/R2 +…

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

How do you calculate MABP?

A

MABP = CO*TPR

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is the definition of voltage?

A

A measure of the electrical work done to separate charges across the membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What is the equilibrium potential?

A

When the force of the concentration gradient of K+ out of the cell is matched by the electrical force pulling K+ back into the cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is the Nerst equation for monovalent ions?

A

E = 58 (mV) x log [Cout]/[Cin]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What are the equilibrium potentials of sodium and postassium?

A

Sodium: +50 mV
Potassium: -90 mV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

How do you calculate the driving force on the ion out of the cell?

A

Vm - Eeq

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What is the Goldman Hodgkin Katz equation?

A

Calculates membrane potential taking into account permeabilities of ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Where are cardiac t-tubules absent?

A

Atria, neonatal and avian hearts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

How long is the cardiac AP?

A

200-400 ms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Why is the cardiac AP so long?

A

Prevents tetany, protects against re-entering arrhythmias

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What does cardiac muscle require to initiate contraction?

A

Calcium influx

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What is the difference in the mechanisms of calcium release in skeletal, cardiac and smooth muscle?

A

Skeletal: depolarization-induced calcium release (L-type calcium channels/DHP act as plug on RyR)
Cardiac: Ca-induced Ca-release
Smooth: IP3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

How is calcium removed from the sarcoplasm in cardiac muscle cells?

A

Through SERCA and sarcolemma Na/Ca exchanger

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

What is the explanation of the length-tension relationship in cardiac muscle?

A
  1. Overlap of thick and thin filaments (only accounts for 20%)
  2. Increased calcium affinity to troponin C upon increased sarcomere length
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

What is the Frank Starling law of the heart?

A

CO is directly related to filling pressure; peak systolic pressure is directly related to resting fibre length

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

How is the force-frequency relationship in a failing heart?

A

Negative: force decreases with increasing frequency; due to decreased action of SERCA and increased action of Na/Ca exchanger

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

Which are the smooth muscle containing organs?

A

Blood vessels, GI tract, bladder, ureters, urethra, uterus, respiratory system, vas deferens and corpus cavernosum, iris and ciliary body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

What are dense bodies?

A

Structures in SMCs that anchor actin filaments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

Which are the vasoconstrictors of vascular smooth muscle?

A

Noradrenaline (from symp nerves)
Histamine (locally released from veins), PGF, TXA2
Adrenaline, angiotensin II, vasopressin (hormones)
Pressure, moderate cold

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

Which are the vasodilators of vascular smooth muscle?

A

VIP, substance P, CGRP, ACh (ANS nerves)
PGE2, PGI2, NO, EDHF, histamine (arterioles)
Adrenaline (some organs), ANP
Flow, heat

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

How is vascular smooth muscle contraction mediated?

A

Adrenaline/angiotensin II or other vasoconstrictors –> activate alpha 1 receptors:

  1. Phospholipase C –> IP3 and DAG –> calcium release from SR + Ca and Na influx through receptor gated channel
  2. Rho kinase –> calcium sensitisation

Stretch –> stretch activated channel –> sodium influx –> membrane depolarisation –> opening of voltage gated calcium channels (VGCC)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

How does NO-mediated vasodilation occur?

A

Endothelial cells secrete NO –> activation of guanylate cyclase –> cGMP:

  1. Stimulation of SERCA and PMCA (plasma membrane Ca ATPase)
  2. Calcium desensitisation
  3. Opening of K+ channels –> membrane hyperpolarisation –> closing of VGCC
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

How does cAMP-mediated vasodilation occur?

A

Adrenaline, adenosine or prostacyclin –> beta1 activation –> increase in cAMP:

  1. stimulates SERCA and PMCA
  2. Opening of K+ channels –> membrane hyperpolarisation –> closing of VGCC
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

What are the mechanisms of the crossbridge cycle in SM and its regulation?

A

Myosin light chain kinase + calmodulin + calcium –> active complex:
1. myosin –> phosphorylated myosin –> crossbridge cycle

Regulation by myosin phosphatase:

  1. Inhibited by agonists via rho kinase –> Ca sensitisation
  2. Activated by NO via cGMP –> Ca desensitisation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

What are latch bridges?

A

Form when myosin is dephosphorylated while still bound to actin –> cycle very slowly and thus maintain force

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

What is the AP upstroke and repolarisation in smooth muscle due to?

A

Upstroke: voltage gated calcium channels influx
Repolarisation: K+ outflow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

What is the difference between unitary and multi-unit smooth muscle?

A

Unitary: not all cells have synaptic input, excitation is spread through gap junctions
Multi-unit: each muscle cell has synaptic input (iris, ciliary body, piloerector muscles)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

Which receptors are present in the sympathetic and parasympathetic pathways?

A

Preganglionic onto postganglionic: ACh onto nicotinic
Postganglionic onto effector:
1. Sympathetic: NA onto alpha or beta (except sweat glands –> ACh onto muscarinic)
2. Parasympathetic: ACh onto muscarinic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

What are NA and Adrenaline derived from?

A

Tyrosine + tyrosine hydroxulase –> DOPA
DOPA + DOPA decarboxylase –> dopamine
dopamine + dopamine beta-hydroxylase –> noradrenaline

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

How and why is NA stored?

A

Unprotected monoamines (NA, serotonin, dopamine) are metabolised by monoamine oxidase (MAO); thus, NA is taken into vesicles via vesicular monoamine transporter (VMAT)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

What is the action of reserpine?

A

Blocks VMAT

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

What is the function of alpha 2 receptors in NA signalling?

A

Located on the presynaptic membrane and provide negative feedback mechanism to prevent further release of NA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

What is the action of cocaine?

A

Blocks uptake 1 channels preventing NA reuptake –> more NA is available for signalling

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

What is the action of clonidine and its uses?

A

alpha2 receptor agonist –> inhibits NA release

Uses: hypertension and tachycardia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

How is NA inactivated?

A
  1. Taken up presynaptically by uptake 1 channels –> MAO

2. Diffuses away and is taken up by extrasynaptic uptake (uptake 2) –> COMT –> MAO in liver and gut –> VMA in urine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

What are the actions of salbutamol and salmeterol?

A

beta2 agonists –> bronchodilation (asthma) and uterine relaxation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

What are the actions and uses of propanolol?

A

non-selective beta antagonist; used for hypertension, angina

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

What are the actions and uses of prazosin and tamsulosin?

A

Alpha adrenoreceptor antagonist –> benign prostatic hypertrophy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
63
Q

What are the effects of alpha1 stimulation on the following:

  1. Vascular smooth muscle
  2. Longitudinal muscle of GI tract
  3. Anal sphincter
  4. Urinary sphincter
  5. Uterine muscle
  6. Radial muscle
  7. Salivary glands
  8. Glycogen metabolism
  9. Vas deferens
A
  1. Vascular smooth muscle: contraction
  2. Longitudinal muscle of GI tract: relaxation
  3. Anal sphincter: contraction
  4. Urinary sphincter: contraction
  5. Uterine muscle: contraction
  6. Radial muscle: contraction
  7. Salivary glands: increased secretion
  8. Glycogen metabolism: increase
  9. Vas deferens: contraction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
64
Q

What are the effects of beta1 stimulation?

A

Increased heart rate and force of contraction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
65
Q

What are the effects of beta2 stimulation?

A

Relaxation of bronchial smooth muscle and vascular smooth muscle
Skeletal muscle, coronary and hepatic arteriole vasodilation
Uterine smooth muscle relaxation
Glycogen mobilisation in the liver

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
66
Q

How do adrenaline and noradrenaline sympathomimetics differ in their action?

A

Noradrenaline: more potent on alpha receptors, least on beta2
Adrenaline: more potent on beta receptors, used also for anaphylactic shock (im or sc)
Both used for acute hypotension and cardiac arrest (iv)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
67
Q

Which are alpha-selective sympathomimetics?

A

phenylephrine (alpha1): acute hypotension

clonidine (alpha2): hypertension, migraine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
68
Q

Which are beta-selective sympathomimetics?

A

Isoprenaline (beta): heart block
Salbutamol: asthma, premature labor
Dobutamine: cardiogenic shock

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
69
Q

What are labetalol and carvedilol?

A

non-selective adrenergic receptor antagonists

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
70
Q

What are propanolol and timolol?

A

beta-selective antagonists

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
71
Q

What are metaprolol and atenolol?

A

beta1-subtype selective antagonists

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
72
Q

What are the structures of muscarinic and nicotinic receptors?

A

Muscarinic:
-GPCR
-5 subtypes: M2 (cardiac) –> Galphai/o leads to decrease in cAMP; M3 (smooth muscle, glandular) –> increase in IP3 and DAG
Nicotinic: nonselective cation channel, causes rapid cell depolarisation –> 5 subunits and 2 subtypes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
73
Q

How does the baroreceptor reflex work?

A

Arterial stretch sensed by afferent nerves of vagus nerve (aortic arch) and glossopharyngeal nerve (carotids) –> signal to the NTS in brain stem:
1. increase PNS drive to heart –> decrease heart rate and CO
2. decrease SNS –> decreased TPR
since BP = CO*TPR –> BP decreases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
74
Q

What are the parasympathetic effects on the eye?

A

Accommodation for near vision –> contraction of ciliary muscle allows lens to relax
Pupil constriction –> contraction of sphincter pupillae muscle in the iris (pupil constriction)
Mediated by CN III (oculomotor nerve)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
75
Q

What are the mechanisms of cholinergic neurotransmission?

A
Choline acetyltransferase:
Acetyl CoA + choline --> acetylcholine
Storage in vesicles
Acetylcholinesterase:
ACh --> choline + acetate --> reuptake mechanism
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
76
Q

Why is ecothiopate given for closed angle glaucoma?

A

long-lasting cholinesterase inhibitor:

pupillary constriction increases outflow of acqueous humour –> decreased intraocular pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
77
Q

What is the action of botulinum toxin?

A

Binds to and degrades SNAP-25 –> prevents exocytosis of ACh and other NTs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
78
Q

How is salivary secretion controlled?

A

Afferents from smell, higher brain centres to hypothalamus and from trigeminal nerve (tongue) to brain stem:

  1. Parasympathetic efferents: CN IX to parotid and VII to sublingual and submandibular
  2. Sympathetic: through thoracic nerves I and II
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
79
Q

Where is innervation to the GI tract located?

A

Submucosa: Messner’s plexus

Between inner circular and outer longitudinal: Auberbach’s plexus

80
Q

How do parietal cells work?

A

Activated H+/K+ ATPase by increase in cAMP –> canaliculi formation –> Cl- follows H+ through facilitated diffusion
Cl- enters cell at basolateral membrane through Cl-/HCO3- antiporter

81
Q

How does the gastric phase of gastric acid secretion work?

A

Distension of the stomach:
1. ENS –> ACh –> stimulation of antral G cells, ECL cells and parietal cells
2. Vagovagal reflex –> ACh release + GRP (gastrin releasing peptide) –> stimulation of antral G cells –> gastrin –> ECL cells –> histamine –> parietal cells)
Digestion of protein:
1. peptides and amino acids stimulate antral G cells

82
Q

What enzymes are present in the pancreatic juice?

A

Proteolytic: trypsinogen, chymotrypsinogen, procarboxypolypeptidase, ribonuclease, deoxyribonuclease
Amylase
Lipase

83
Q

How are trypsinogen and chymotrypsinogen activated in the intestinal lumen?

A

Enterokinase: trypsinogen –> trypsin
Trypsin: chymotrypsinogen –> chymotrypsin

84
Q

How are carbohydrates digested?

A

Pancreas and salivary glands secrete alpha-amylase: starch –> maltose + glucose
Small intestine secretes 1,6-glucosidase
Small intestine contains maltase, lactase and sucrase

85
Q

How are proteins digested?

A

Stomach: HCl activates pepsinogen –> pepsins
Pancreatic juices: carboxypeptidases, trypsin, chymotrypsin
Small intestine: breakdown tri and dipeptides with aminopeptidases and dipeptidases; absorption through Na+ and H+ (tri and dipeptide) co-transport

86
Q

How is bile secretion regulated?

A

PNS through vagus nerve –> production of bile in liver
Acidic chyme sensed by enteroendocrine cells of duodenum:
1. Secretion of secretin in the blood –> flow of bile rich in HCO3- and pancreatic juices
Fatty acids and amino acids in chyme:
2. Secretion of CCK –> contraction of gall bladder

87
Q

What is bile flow dependent on?

A

partial pressure of O2

88
Q

What is the structure of the biliary tree?

A

Apical membranes of hepatocytes form canaliculi –> terminal bile ductules (canals of Hering) –> perilobular ducts –> interlobular ducts –> septal ducts –> lobular ducts –> left and right hepatic ducts –> common hepatic duct + cystic duct –> common bile duct

89
Q

How does the gallbladder concentrate bile acids?

A

Apical membrane:
1. Na-H and Cl-HCO3- exchangers –> reabsorption of NaCl
Basolateral membrane:
1. Na/K+ pump –> Na+ exits
2. Cl- leaves through channels
Additional:
1. H2O and HCO3- move through leaky junctions from lumen into blood
Result: isotonic bile with higher concentration of bile acids

90
Q

How is bilirubin excreted?

A

85% from breakdown of red blood cells; fat soluble and toxic; bound to albumin in blood; free form taken up by the liver –> formation of bilirubin glucuronide –> secretion into bile canaliculi
15% reabsorbed in the intestine

91
Q

How are lipids absorbed?

A

Glycerol, short-chain and medium-chain FAs: pass through enterocyte and enter capillaries
Cholesterol, lysophospholipids, long-chain FAs and monoglycerides: present in lumen as mixed micelles with bile salts –> allows absorption of fatty acids at brush border (low pH) –> SER, combine with apoproteins from RER to form chylomicrons (apo B48, C-II, E) or VLDLs –> Golgi –> lacteals

92
Q

What is the function of cholesterol ester transfer protein?

A

Transfer cholesterol esters from HDL to VLDLs, IDLs or LDLs

Cholesterol esters in HDL are formed by LCAT

93
Q

How does the breakdown of fat work?

A

Lingual lipase
Breakdown in stomach (10-30%): gastric lipase + emulsification by gastric contractions
Breakdown and micelle formation in duodenum and jejunum (70-90%): pancreatic lipase
Absorption in small intestine
Excretion as Ca2+ soaps (5%)

94
Q

What is the enterohepatic circulation of bile acids?

A

Bile acids are primarily conjugated to taurine or glycine to form bile salts –> secreted into the duodenum and then:

  1. Reabsorbed passively as conjugated bile salts or through Na+-coupled transporters in terminal ileum
  2. Bacteria in terminal ileum and colon deconjugate –> passively absorbed by nonionic diffusion
  3. Bacteria in terminal ileum and colon dehydroxylate –> secondary bile salts –> passively reabsorbed or excreted in faeces
95
Q

What are the causes of gallstones?

A
  1. too much absorption of water from bile
  2. too much absorption of bile acids
  3. too much cholesterol in bile
  4. inflammation of epithelium
96
Q

What are the effects of vagal and splanchnic nerve stimulation on bile secretion?

A

Vagus: increase production and secretion

Splanchnic nerve: vasoconstriction and reduced flow of bile

97
Q

What is function of VIP on bile secretion?

A

Inhibits net fluid and electrolyte absorption in gallbladder

alpha adrenergic blockage of neural VIP increases fluid absorption

98
Q

What is the role of GIP?

A

inhibition of gastric acid secretion + stimulation of insulin secretion; produced by K cells of the duodenum and jejunum

99
Q

What is the function of the chorda lingual nerve?

A

Parasympathetic innervation evokes marked fluid secretion accompanied by increased blood flow and oxygen consumption

100
Q

What is the function of atropine on salivary excretions?

A

Atropine blocks secretion but not blood flow (VIP or substance P co-release)

101
Q

How is salivation controlled?

A

Production of watery saliva is elicited by cholinergic, adrenergic and peptidergic stimulation
Sympathetic innervation: initial vasoconstriction (then vasodilation) with a viscous, protein-rich secretion via beta-adrenergic stimulation

102
Q

What is the structure of the salivary tree?

A

Acinar cells –> ductule-striated or intercalated ducts –> larger ducts –> main excretory duct into the mouth

103
Q

Through which pathways do sympathetic and parasympathetic nerves operate on salivary glands?

A
Sympathetic:
1. Beta1 --> increased cAMP and NO
2. Alpha1 --> increased Ca2+
Parasympathetic:
1. VIP --> increased cAMP and NO
2. ACh --> muscarinic 1, 3 receptors --> increased cAMP
104
Q

How are primary and secondary saliva different?

A

Primary: isotonic to plasma
Secondary: hypotonic to plasma (reabsorption of NaCl + K+ and HCO3- secretion)

105
Q

How is primary saliva produced?

A

NTs and hormones –> increase in intracellular Ca2+ in acinar cells:
1. Activation of K+ channels on basolateral membrane and Cl- channels on luminal
2. Reuptake via Na+-K+-2Cl- cotransporter dependent on Na+/K+ ATPase
Result: Cl- leaves through channels in luminal membrane and draws water and Na+ through paracellular space

106
Q

What are the two phases of swallowing?

A

Voluntary phase: bolus and tongue movements

Involuntary phase: reflex response stimulated by mechanoreceptors (CN IX and X)

107
Q

How do gastric secretions vary between cardia, pyloric and oxyntic glands?

A

Cardiac glands: mucous primarily, few or no peptic or oxyntic cells
Pyloric glands: alkaline mucous juice and some electrolytes (Ca phosphate, NaCl, KCl and bicarbonates)
Oxyntic glands: key site of gastric HCl secretion

108
Q

What are the different types of cells in gastric pits and what is their function?

A

Superficial epithelial cells
Mucous neck cells: HCO3- rich mucous secretion
Stem/regenerative cells
Parietal/oxyntic cells: HCl secretion
Chief cells: pepsinogen production and secretion
Endocrine G cells: gastrin secretion

109
Q

What is the Dimaline model as opposed to the Soll’s three receptor model?

A

Gastrin activates CCK2 on ECL-cell –> histamine is released and acts on H2 receptors on parietal cells –> cAMP increase
Other pathways:
1. Direct activation of parietal cells by gastrin (CCK2 receptors)
2. ACh activation by M3 receptors –> increase in Ca2+

110
Q

What are the functions of famotidine and omeprazole?

A

Famotidine: H2 antagonist
Omeprazole: proton pump inhibitor

111
Q

How is gastrin secretion regulated?

A

D-cells sense acid in stomach and release somatostatin which inhibits G-cells

112
Q

What is the intestinal phase of gastric secretion?

A

Protein digestion products stimulate acid secretion:
1. Intestinal G cells –> gastrin
2. Intestinal endocrine cells –> entero-oxyntin –> G-cell stimulation
3. Absorbed amino acids –> G cell stimulation
Intestinal acid, fat and hyperosmolar solutions inhibit acid secretions:
1. receptors for H+, osmolarity and neutral amino acids –> sympathetic inhibition
2. fat –> secretion of SIH, GIP and secretin –> endocrine inhibition

113
Q

What are the characteristics of pancreatic juice and how is it secreted?

A

HCO3- and NaCl-rich isotonic fluid

  1. Basolateral uptake of Cl- through NKCC
  2. Basolateral exit of Na+ through Na+/K+ ATPase and exit of K+ through channels (stimulated by Ca2+)
  3. Cl- diffuses down electrochemical gradient at apical membrane
  4. Na+ follows paracellularly
  5. HCO3- produced by carbonic anhydrase –> diffusion and/or HCO3/Cl- exchanger
114
Q

Is the GI tract single or multi-unit smooth muscle?

A

Single (gap junctions are present)

115
Q

What are the interstitial cells of Cajal?

A

Act as pacemakers in the GI tract

116
Q

What is the effect of vagal stimulation, CCK, GIP and secretin on gastric motility?

A

Vagal stimulation: increases
CCK: decreases
GIP: decreases
secretin: decreases

117
Q

Which has the fastest spontaneous activity: stomach, duodenum, ileum or colon?

A

Duodenum

118
Q

What is the function of motilin?

A

Regulates migrating motor complex from stomach to intestines

119
Q

Which mechanisms regulate gastric emptying?

A

Neural enterogastric reflex:
1. Short reflexes operate via ENS
2. Long reflexes via CNS (increase symp and inhibit parasymp)
Hormonal mechanisms:
1. Secretin (stimulates HCO3- secretion and inhibits stomach activity)
2. CCK (gallbladder contraction and inhibits stomach activity)
3. GIP (inhibits gastric contractions)
4. Motilin (increases gastric and intestinal motility)

120
Q

What are the crypts of Lieberkuhn?

A

Opening of intestinal glands

121
Q

Which cells are present in the villous epithelium?

A

Goblet cells and absorptive cells

122
Q

What is the function of Paneth cells?

A

Key effectors of innate mucosal defense of intestinal crypts

123
Q

How is absorption of monosaccharides driven?

A

Basolateral Na+/K+ ATPase generates sodium gradient –> allows SGLUT to work

124
Q

How is the absorption of oligopeptides through H+ cotransporter driven?

A

Apical Na+/H+ exchanger pumps H+ outside –> creates gradient
Basolateral Na+/K+ ATPase pumps Na+ outside –> creates gradient

125
Q

What are hartnup disease and cystinuria?

A

Hartnup disease: autosomal-recessive –> reduced absorption of neutral amino acid phenylalanine
Cystinuria: autosomal recessive –> reduced absorption of L-cystine and cationic amino acids (L-arginine)

126
Q

What are the differences between alpha and gamma tocopherol?

A

Alpha: resecreted as component of hepatically derived HDL and VLDLs
Gamma: metabolised and excreted by the liver

127
Q

How are vitamins B and C absorbed?

A

B1, 2: sodium cotransporter in jejunum

C: sodium cotransporter in ileum

128
Q

How is calcium absorbed across intestinal epithelium?

A

Facilitated diffusion from lumen –> bound to calbindin intracellularly –> exits basolateral membrane via:

  1. Ca2+/3Na+ exchanger
  2. Ca2+/H+ ATPase
129
Q

What are Brunner glands?

A

Situated in the duodenum –> secrete alkaline or neutral mucous

130
Q

Which hormones act on the kidneys?

A

ADH, aldosterone, natriuretic peptides, parathyroid hormones, fibroblast growth factor 23 (FGF23)

131
Q

Which hormones are produced by the kidneys?

A

Renin, vitamin D, erythropoietin, alphaKlotho, prostaglandins

132
Q

What is the filtration interface of the renal corpuscle composed of?

A
Fenestrated capillary endothelium
Basement membrane (fixed polyanions)
Tubular epithelium (podocytes)
133
Q

What are the types of nephrons and their prevalence?

A

Cortical (85%), juxtamedullary (15%)

134
Q

What constitutes the juxtaglomerular apparatus?

A

Macula densa (end of ascending loop of Henle)
Mesangial cells in between the afferent and efferent arteriole
Juxtaglomerular cells on afferent arteriole (innervated by sympathetic fibers)

135
Q

How much of the plasma that enters the glomerulus is filtered?

A

20%

136
Q

What is a substance that is filtered and secreted but not reabsorbed?

A

PAH

137
Q

What are substances that are filtered and some of it are reabsorbed?

A

Water and electrolytes

138
Q

What is a substance that is filtered and completely reabsorbed?

A

Glucose

139
Q

What is the maximal size for glomerular filtration?

A

7 kDa

140
Q

What are the differences between ultrafiltrate and plasma?

A

Ultrafiltrate does not contain proteins and molecules that can bind to proteins (Ca2+ and some drugs)
Albumin binds acidic drugs, alpha1-acid glycoprotein binds basic drugs

141
Q

What is the definition of GFR?

A

Volume of fluid filtered from the glomeruli per minute

142
Q

What is the net glomerular filtration pressure?

A

(60-15)-(29-0)= 16 mmHg

143
Q

What are the typical GFR and urine output?

A

GFR: 180 l/day

urine output: 1.5 l/day

144
Q

How is filtered glucose reabsorbed and where?

A

PT;

  1. SGLT
  2. GLUT facilitated transporters
  3. Na+/K+ ATPase keeps gradient
145
Q

How are amino acids reabsorbed and where?

A

PT;
at least 8 aa transporters, 6 Na+-dependent
Proteins: reabsorbed through endocytosis

146
Q

How are phosphate and sulphate reabsorbed in PCT?

A

Na+ coupled transporters

147
Q

Which compounds are passively reabsorbed in PCT?

A

urea, chloride, potassium, calcium

bicarbonate (linked to H+ secretion)

148
Q

Which compounds are secreted in PCT?

A

Organic acids (anions): enter basolateral through dicarboxylate exchange (OAT1,3; Na+ coupled transport with DC-), exit via ATP-dependent transporters
1. Drugs (penicillin)
2. Endogenous molecules (bile salts, fatty acids, prostaglandins)
3. diagnostic agent (PAH)
Organic bases (cations): enter via facilitated organic cation transporter (OCT2), exit through MATEs antiporter in exchange for H+ or OCTN
1. Endogenous molecules (creatinine, dopamine, choline, guanidine, histamine, serotonin, adrenaline)
2. Drugs (morphine, atropine)

149
Q

What is the definition of clearance?

A

Volume of plasma that is cleared of a substance in a given time (uv/p)

150
Q

Which substances are used to measure GFR?

A

Experimentally: inulin (filtered, not secreted, not reabsorbed)
Clinically: creatinine

151
Q

How do you measure renal plasma flow?

A

renal plasma flow = PAH clearance (around 600 ml/min)

152
Q

How do you calculate blood flow from plasma flow?

A

Blood flow = plasma flow/ (1-hematocrit)

153
Q

What are the normal osmolalities for plasma and urine?

A

Plasma: 285-295 mosom/kg
Urine: 50-1400 mosm/kg

154
Q

Where is the majority of sodium reabsorbed?

A

Proximal (65%) and thick (25%) ascending

Hormonal control: distal (2-5%) and collecting (5%)

155
Q

How is sodium reabsorbed in proximal tubule?

A
Apical:
1. Na/H exchanger 
2. Na-nutrient symporter
Basolateral:
Na+/K+ ATPase
Others: Cl- follows paracellularly
156
Q

How is sodium reabsorbed in the thick ascending limb?

A
Apical:
1. NKCC
2. K+ channels --> pump K+ out to create gradient
Basolateral:
1. Na/K+ ATPase
2. KCl cotransporter
3. Cl- channels
157
Q

How is sodium reabsorbed in the distal tubule?

A
Apical:
1. NaCl cotransporter
Basolateral:
1. Na/K+ ATPase
2. Cl- channels
3. K+ channels
158
Q

How is sodium reabsorbed in the collecting duct?

A

Principal cells (Na+ transport), intercalated cells (H+ transport)
Apical: eNaC
Basolateral: Na+/K+ ATPase

159
Q

How does the loop of henle work?

A

Countercurrent multiplier
Descending limb: picks up salt and loses water (AQP1) –> progressively more concentrated
Ascending limb: solute pump, water-impermeable –> dilute urine (100 mosm/kg)
Vasa recta: countercurrent exchange mechanism

160
Q

How does urea recycling by the kidney occur?

A
  1. PT: passive reabsorption of urea (50%)
  2. Loop of henle: apical secretion via urea transporters (UT-A2) –> 60% secreted
  3. Inner medullary collecting duct (apical reabsorption via UT-A1 + UT-A3) –> 70% reabsorbed
    40% of that filtrated is excreted
161
Q

What is the action of ADH on collecting duct?

A

ADH stimulates GPCR –> increase cAMP –> activated PKA –> AQP2 expression on apical side
AQP3 and 4 on basolateral

162
Q

What is the definition of oliguria?

A

Output below 0.428 l/day

163
Q

What are the definitions of concentrated and dilute urine?

A

Dilute: <300 mosm/kg
Concentrated: >300 mosm/kg

164
Q

How is osmolar clearance calculated?

A

Cosm = (Uosm*V)/Posm

165
Q

What is the free water clearance?

A
Reflects the ability of the kidneys to excrete concentrated or dilute urine
Ch2o = V- Cosm
>0 --> hypo-osmotic
=0 --> isosmotic
<0 --> hyperosmotic
166
Q

What are the regions involved in ADH release?

A

Osmoreceptors in OVLT, MPN, SFO signal to supraoptic nuclei (SON) and paraventricular nuclei (PVN) in hypothalamus –> ADH release from posterior pituitary

167
Q

Which molecules increase/decrease ADH secretion?

A

Angiotensin II increases; natriuretic peptides decreases
Alcohol –> inhibits ADH
Nicotine –> stimulates ADH

168
Q

What is diabetes insipidus?

A
  1. urination (polyuria –> >2l/day)
  2. thirst (polydipsia)
  3. nocturia
    Neurogenic: no ADH secreted
    Nephrogenic: inherited mutation in channel or acquired
169
Q

What is osmotic diuresis?

A

Increased urination due to small molecules in renal tubule lumen

170
Q

What are the elements involved in the maintenance of potassium balance?

A

Renal excretion, GI losses, cellular shifts

171
Q

How much potassium is ingested daily?

A

40-120 mmoles

172
Q

How is potassium filtered, reabsorbed and secreted in urine?

A

800 mmoles/day is filtered

95% passively reabsorbed (65% passively in PT, 30% in thick ascending limb, 5% in distal tubule via K+/H+ exchanger)

173
Q

How do collecting ducts influence K+ reabsorption and secretion?

A

Intercalated cells: K+ reabsorbed through K+/H+ exchanger

Principal cells: K+ is secreted by ROMK, Ca2+ activated big-conductance K+ channels (BK) and KCl cotransporter

174
Q

Which factors affect K+ secretion by principal cells?

A
  1. Factors affecting Na+ entry through ENaC
  2. Aldosterone stimulates K+ channels
  3. Tubular flow rate: high flow favours secretion
  4. Acid-base balance: acidosis inhibits, alkalosis enhances
175
Q

What is hypokalemia and what are its causes?

A

K+ < 3.5 mM

  1. Increased external losses (diuretics, hyperaldosteronism, alkalosis, vomiting, diarrhoea, burns, intense sweating)
  2. redistribution into cells (metabolic alkalosis, insulin excess)
  3. Inadequate K+ intake
176
Q

What is hyperkalemia and what are its causes?

A

K+ > 5.5 mM
1. Decreased external losses (renal failure, hypoaldosteronism, action of drugs)
2. Redistribution out of cells (acidosis, lack of insulin, tissue destruction)
Treatment: Ca2+ iv, insulin administration, long-term diuretics

177
Q

What is the lateral preoptic area responsible during water deprivation?

A

Osmoreceptors –> signal thirst

178
Q

What are the intrinsic and extrinsic controls of GFR?

A

Extrinsic: maintains arterial BP by controlling GFR (sympathetic NS baroreceptor reflex)
Intrinsic: protects renal capillaries from hypertensive damage (tubuloglomerular feedback)

179
Q

How does the tubuloglomerular feedback work?

A

Increased flow of Na through macula densa –> increased production of adenosine –> increased Ca2+ in granular juxtaglomerular and VSM cells –> constriction and inhibition of renin release

180
Q

What stimuli lead to renin release?

A
  1. low sodium delivery to macula densa
  2. decreased wall tension in afferent arteriole (intrarenal baroreceptor)
  3. sympathetic activity
  4. low blood volume (hypovolemia)
181
Q

What are the effects of renin?

A
Plasma angiotensinogen --> Angiotensin I
Angiotensin I + ACE --> angiotensin II:
1. Stimulates PT Na+ reabsorption
2. ADH release
3. Aldosterone secretion
4. Thirst
5. Vasoconstriction of small arterioles
182
Q

What stimuli lead to aldosterone secretion?

A

Angiotensin II; increased K+ concentration

183
Q

What are natriuretic peptides?

A

Released when the heart is stretched; A type from atrial myocardium and B type from ventricular myocardium
Actions:
1. Inhibit Na+ entry through ENaC in principal cells and Na/K ATPase in proximal tubule
2. inhibit renin release and aldosterone production
3. Inhibit ADH release
4. Systemic vasodilation –> decreased BP
5. Afferent arteriole dilation –> increased GFR

184
Q

What are the buffers in blood, extracellular, intracellular fluid and urine?

A

Blood: hemoglobin, bicarbonate and plasma proteins
Extracellular fluid: bicarbonates, very little proteins
Intracellular fluid: intracellular proteins, phosphates, a little bicarbonate
Urine: ammonia, phosphates

185
Q

How does the kidney control pH?

A
  1. Absorb HCO3-

2. Excrete H+

186
Q

Where does bicarbonate reabsorption occur?

A

PT, ascending loop of Henle, intercalated cells type A
H2O + CO2 + carbonic anhydrase –> H+ + HCO3-:
bicarbonate goes to blood
H+ secreted into filtrate –> not excreted if HCO3- is available in the lumen

187
Q

How does H+ excretion happen?

A

In combination with nonbicarbonate buffer (monohydrogen phosphate)
Result: addition of new HCO3- to plasma

188
Q

Apart from H+ excretion, what is another mechanism that produces new HCO3-?

A

Glutamine absorbed through Na+ symport into tubular epithelium
Glutamine metabolised in tubule epithelium –> ammonium ions + bicarbonate
Ammonium ions secreted through Na+ exchanger

189
Q

What is the difference between respiratory and metabolic acidosis and alkalosis?

A

Respiratory acidosis: high pCO2
Respiratory alkalosis: low pCO2
Metabolic acidosis: low HCO3-
Metabolic alkalosis: high HCO3-

190
Q

How is acidosis compensated?

A
  1. Chemical: CO2 –> HCO3-
  2. Brainstem: adjust ventilation
  3. Renal mechanisms: increase plasma HCO3-
191
Q

How is metabolic alkalosis compensated in the kidneys?

A

Type B intercalated cells secrete HCO3- through HCO3-/Cl- exchanger

192
Q

How does glutamine production by the liver change in alkalosis and acidosis?

A

Acidosis: increases
Alkalosis: decreases

193
Q

How is the epithelium of the colon?

A

Flat with deep crypts

194
Q

What is the percentage of water in normal stool?

A

65-85%

195
Q

How does intestinal Na+ reabsorption vary throughout the GI tract?

A

Proximal bowel: Na/H exchanger
Jejunum: SGLUT, Na-aa cotransport
Ileum: NaCl cotransport
Colon: Na+ ion channels + HCO3-/Cl- antiporter

196
Q

What types of diarrhoea are there?

A

Congenital: deficiency of normal ion transport system (Cl-/HCO3- exchanger lacking)
Bacterial infection: cholera toxin –> permanently activates AC –> increased cAMP –> Cl- secretion
Osmotic (>350 mosm)

197
Q

Which bacteria are present in the colon?

A

Bacteroides: gram-negative, anaerobic, non spore forming
Bifidobacteria: “good bacteria”, gram-positive, non-sporeforming, lactic acid bacteria