Week 7 Flashcards
What is homeostasis?
Maintaining a constant internal environment (With set limits)
Examples where homeostasis occurs?
Temperature – blood and skin
Salt (electrolytes) concentration- kidneys
Water - kidneys
Proteins, fats (lipids), carbohydrates – the liver
What are the basic components of a homeostatic system?
Receptor - detects changes
Control centre - recognises information, processes it, and formulates a response
Effector – responds
Negative feedback prevents small/acute changes from becoming big ones.
Proportion of body weight represented by water in male, female and neonate
Neonate = 80%
Male = 60%
Female = 50%
What is the distribution of body fluids?
3L plasma
12L Interstitial fluid
25L Intracellular fluid
(40L total)
What is fluid movement influenced by?
Diffusion, osmosis, filtration, reabsorption, secretion
What is osmosis
Movement of water through a selectively permeable membrane (plasma membrane) from an area of lower solute concentration to an area of higher solute concentration.
What is osmolality?
Number of particles that have an osmotic effect
What should the overall water intake and loss per day equal?
0
(2.2L intake + 0.3L metabolic production - (0.9 + 1.5 + 0.1)L output = 0)
What are the basic components of the urinary system?
Kidneys
Ureters
Bladder
Urethra
Why is the renal artery located above the renal vein in the kidney?
To create a pressure gradient
What does the renal corpuscle refer to?
Glomerulus and Bowman’s capsule
Where does blood enter and exit the glomerulus?
Enters via the afferent arteriole and exits the efferent arteriole of glomerulus.
What occurs in the glomerulus?
Filtration.
Water and all solutes (eg glucose, amino acids, ions, waste products, etc) enter Bowman’s capsule (but not proteins >65KD)
How does filtration occur in the glomerulus?
The afferent arteriole has a larger diameter than the efferent, therefore creating high pressure in the glomerulus.
Where unfiltered blood leaves via the efferent vessel, and filtered fluid moves to the proximal convoluted tubule
Components of the filtration membrane in the nephron?
Glomerular endothelial cell
Pore: All plasma passes
Basal lamina of glomerulus: Large proteins held back
Slit membrane between pedicels: Medium-sized proteins held back
What is the role of the proximal convoluted tubule?
Reabsorption back into the blood:
Water 65%, osmosis
Na+ 65% (symporters and others)
Glucose 100% (symporters)
Cl- 50%
HCO3 80-90% (bicarbonate)
Secretion into tubular fluid:
H+ (variable)
NH4+ (variable)
Urea (variable)
What do we start to see glucose within the urine (glycosuria)?
[Glucose] plasma > 10mmol/L
(Usually indicating diabetes)
What transport process does the proximal convoluted tubule use?
Active transport
Therefore lots of mitochondria are present.
And surface area for reabsorption is increased by microvilli
Why does water move out of the descending limb of loop of Henle?
The medulla solute concentration increases. (osmosis occurs in this tubule)
Therefore, tubular fluid is very concentrated at hairpin
What occurs at the ascending limb of the LoH?
NaCl diffuses into medulla interstitial fluid at base of LoH.
Active transport of NaCl in thick section of LoH. Creates salt concentration gradient in the medulla (ascending limb is impermeable to water)
What occurs at the distal convoluted tubule?
Reabsorption back into blood:
- Na+ ions 5% (increased by action
of aldosterone enabling
more water reabsorption by
osmosis)
- Water 10-15% (osmosis)
- Cl- 5%
Secretion into the tubular fluid:
H+ (variable)
K+ (variable)
NH4+ (variable)
Urea (variable)
What occurs in the collecting duct in the nephron? (reabsorption)
Reabsorption back into blood:
- Water variable (ADH causes insertion of aquaporin 2, water channels into into Principal cells of collecting duct so concentrated urine is made)
- Na+ (therefore, if no ADH, dilute urine is made)
- Urea (recycling into base of LoH to increase solute conc in medulla)
What occurs in the collecting duct of nephron? (secretion)
Secretion into tubular fluid:
K+ (variable)
H+ (variable) - adjust blood pH
What are the two types of Diabetes Insipidous?
Craniogenic,
Nephrogenic
What happens in the collecting duct of a dehydrated individual?
ADH release promotes water reabsorption.
- ADH release, water channels in collecting duct
- H2O reabsorbed back into body from tubular fluid
- Concentrated (hyperosmotic) urine
What are the different types of nephron?
Cortical nephron (short LoH, mainly located in cortex)
Juxtamedullary nephron (LoH extends deep into medulla)
Longer LoH, greater ability of individual to produce concentrated urine. Enables conservation of water, for example in desert rats
What can occur if an individual is dehydrated?
(diarrhoea, vomiting)
Weight loss,
Increasing thirst,
Light headedness,
Kidney failure
What can occur if an individual is overhydrated?
(Water intoxication)
Digestive problems,
Behavioural changes,
Seizures,
Coma
How does ADH prevent water loss in a dehydrated patient?
Anti diuretic hormone (ADH) = vasopressin
Made in hypothalamus and released from posterior pituitary gland
More water reabsorbed from the collecting ducts back into the body
Concentrated urine produced
Water conserved
What happens in the Juxta Glomerular Apparatus in response to low BP or low Na+ in the distal tubule?
Granular cells secrete renin which results in the release of aldosterone
What is natriuresis?
Loss of Na+ and Cl- in urine
What happens in overhydration in the nephron?
Atrial natriuretic peptide (ANP):
- Blood vol inc
- Atria of heart stretch, ANP produced
- Natriuresis
- Water follows electrolytes = lots of dilute urine
- Blood vol dec
ADH:
- Secretion of AHD shuts down therefore less H2O reabsorbed in collecting duct
What is the Renin-Angiotensin-Aldosterone System?
Drop in blood pressure and fluid volume triggers renin release from the kidney.
Renin acts on angiotensinogen from the liver forming angiotensin I.
Angiotensin-converting enzyme is released from the lungs, acts on angiotensin I forming angiotensin II.
This acts on the adrenal gland stimulating release of aldosterone.
Aldosterone acts on the kidneys to stimulate reabsorption of salt and water
What happens when angiotensin II acts directly on blood vessels?
Vasoconstriction (narrowing) is triggered.
What are the major functions of the liver?
Phagocytosis
Synthesis of Bile Sales and Excretion of Haem
Synthesis of Serum Proteins
Metabolism (carbohydrate, lipid, protein)
Processing of drugs and hormones
Activation of vitamin D
Storage (eg glycogen)
Why isn’t the Hepatic Portal vein not a true vein?
it conducts blood from the capillary bed of the GI tract into the capillary be of the liver and does not go directly to the heart
What is the first pass effect?
A way in which our body protects us from exogenous substances whatever we put in our mouth goes to the liver first to remove toxins before going around the body.
How does oxygen/blood leave the liver?
Via the inferior vena cava
How does oxygen/blood enter the liver?
Via the Hepatic artery
What is a Kupffer Cell? (liver)
Within sinusoids
Fixed phagocytic cells
Bacteria and old blood cells
Where is bile stored?
Gail bladder
What are the components of bile?
800ml - 1L p/day
Yellow/green
pH 7.6-8.6
What does bile contain?
Water
Bile salts
Cholesterol
Phospholipids
Bile pigments
Ions
Bile salts digestion function?
Based on structure of cholesterol
Emulsify fats
Allow pancreatic lipase to break down fats more easily
Aid absorption of lipids
What make up bile pigments?
RBC broke down in the splean (recycle the iron present in haemoglobin, break down haem)
Bilirubin (yellow) breakdown product of haem
Bilirubin metabolised by bacteria to give stercobilin (brown) - faeces
What does unconjugated bilirubin bind to before it foes to the liver to become conjugated?
Protein Albumin
What is the function of glycogenesis
Maintain circulation of glucose levels, whether just eaten or not
(To provide the body with an alternative glucose between meals, to maintain its levels)
What is the function of glycolysis (glycogenolysis)?
Describes the breakdown of glycogen into glucose using adrenaline and glucagon
What is epinephrine?
Adrenaline
What is glycogenesis stimulated by?
Insulin
What is glycogenolysis stimulated by?
Glucagon and epinephrine
What is gluconeogenesis stimulated by?
Cortisol and glucagon
What is gluconeogenesis?
Generating new glucose, (prolonged post-absorptive state) - from used up glycogen stores
What is lipogenesis?
Make triglycerides
Glucose + amino acid –> Glycerol and fatty acids
(stimulated by insulin)
What happens in beta oxidisation pf lipids?
Fatty acids split into two carbon molecules
What is lipolysis?
Triglycerides broken down to fatty acids and glycerol
Glycerol –> pyruvate –> acetyl CoA
Beta oxidisation –> acetyl CoA
Acetyl CoA –> Acetoaceditic acid (–> B hydroxybutyric acid and acetone)
Icetone bodies –> ATP
What are the functions of lipid metabolism in Hepatocytes?
Make Triglycerides (lipogenesis)
Triglycerides broken down to fatty acids and glycerol (lipolysis)
make cholesterol (a lipid) + bile salts
What is anabolism in liver?
Hepatocytes make plasma proteins (eg albumin and fibrinogen)
Where are intercalated disks found?
Cardiac muscle
Mesodermal tissue can give rise to what during development?
Connective tissue
Epithelial tissue
muscle tissue?
What systems is the pancreas a part of?
endocrine system + digestive system
Waste elimination is carried out by what system?
Urinary + digestive system + integumentary system
True or false?
The nervous system initiates muscle contraction or glandular secretion
True
True or false?
Parts of the skeletal system produce blood cells
True
True of false?
Dense connective tissue is only regular
False - Can be regular or irregular
Collagen is where in connective tissue?
Part of the extracellular matrix
Does epithelium have a blood supply (well vascularised)?
No - the connective tissue underneath the epithelium has a good blood supply however
Do endocrine glands have ducts to release their hormones?
No
True or false
Cells of merocrine glands secrete contents by cell rupturing
False
The cell junctions respectively that exclude the passage of water between cells, maintain tissue form and strength, and allow the exchange of small molecules between cells are:
Tight junctions, desmosomes, gap junctions
True or false
Dense connective tissue combines elasticity with strength
true
true or false
The kidneys regulate blood volume composition
true
true or false
a role of the cardiovascular system is the repair of tissues
true
What is the equation to calculate filtration pressure (FP)?
FP = net hydrostatic pressure + net osmotic pressure
True or false The descending loop of Henle is permeable to water, so the concentration of the tubular fluid INCREASES the further into the medulla the Loop of Henle extends.
true
true or false
The ascending loop of Henle is freely permeable to sodium ions at the base of the Loop of Henle. Further up the ascending Loop of Henle, sodium ions are actively pumped out of the tubular fluid into the interstitial fluid of the medulla. This creates a salt concentration gradient.
true
true or false
The production of the osmolarity gradient in the medulla of the kidney is created by the Loop of Henle and also by urea recycling between the collecting duct and the base of the Loop of Henle.
true
true or false
The Loop of Henle of the Juxtamedullary nephron creates an osmotic gradient in the medulla which enables water to be reabsorbed from the collecting duct of the nephrons, when ADH (vasopressin) is present.
true
Podocytes, the basal lamina of the glomerulus and the glomerular endothelial cell pores form what?
Filtration membrane
What arteriole has a wider diameter, afferent or efferent?
The afferent arteriole, leading to the renal corpuscle has a wider diameter than the efferent arteriole
true or false
Once tubular fluid has passed through the Juxtamedullary nephron’s Loop of Henle (descending limb AND ascending limb), it is hyperosmotic compared with the tubular fluid at the start of the proximal convoluted tubule.
false
does ANP relax mesangial cells in the visceral layer of bowmans capsule?
yes
Does ANP release lead to a decrease in blood flow through glomerulus and more fluid is filtered out of the blood?
No - it leads to an increase in blood flow through the glomerulus and more fluid filtered out of the blood
true or false
ANP promotes natriuresis (loss of salt in the urine) which aids water loss in the urine too.
True
ADH (vasopressin) enables hypersomotic urine to be produced where?
the nephron
What % of water is reabsorbed from tubular fluid by the proximal convoluted tubule back into the circulation?
Approximately 65%
True or false
Hyperosmotic urine is produced within the Loop of Henle of the Juxtamedullary nephron.
false
tubular fluid at the end of the Loop of Henle has a lower concentration to that entering the Loop of Henle.
The LoH enables the osmotic gradient to be created in the medulla essential for the production of hyperosmotic urine because through the action of ADH, the collecting duct becomes permeable to water so tubular fluid becomes more concentrated as the collecting tube traverses the medulla. ADH could not cause hyperosmotic urine production if it were not the for the increasing salt concentration gradient within the medulla.
does the osmolarity of the interstitial fluid in the kidney medulla increase as it nears the renal pelvis?
Yes, there is a higher concentration of NaCl and urea deep within the medulla, which enables water to be reabsorbed from the collecting duct, when ADH is present
True or false?
A decrease in angiotensin II increases blood flow in the glomerulus?
False, an increase in angiotensin II decreases blood flow in the glomerulus
True or false
Aldosterone causes the proximal convoluted tubule to reabsorb K+ and water?
True - Aldosterone causes the proximal convoluted tubule to reabsorb more Na+ and water
Features of thick filaments in skeletal muscle fibres?
- Bind to ATP during concentration
- Composed of several myosin molecules wound above one another
- Bind to actin via cross bridges, during concentration
Features of thin filaments in skeletal muscle?
- Contain regulatory proteins known as tropomyosin and troponin
- Contain myosin-binding sites which, in the relaxed state, are covered by tropomyosin
The nuclei in a skeletal muscle fibre lie directly beneath what?
Sarcolemma
True or false an action potential is quickly transferred to all myofibrils in a muscle fibre, via R tubules?
false - it is T-tubules which transfer action potentials
true or false
When an action potential arrives at the neuromuscular junction, calcium is released into the overlap zone of the sarcomere, enabling the thick and thin filaments to interact and hence contract the sarcomere.
true
