Anatomy and Physiology Flashcards
Main functions of the renal system?
Fluid and electrolyte balance
Removal of waste and reabsorption of others
Regulate blood pH
Endocrine functions
Blood pressure control
Gluco-neogenesis
Regulates blood volume
Regulates RBC production
What is most of the renal medulla made up of?
Pyramids
Main structure of the nephron?
Bowman’s capsule
Glomerulus
Loop of Henle
Vasa recta
Proximal convoluted tubule
Distal convoluted tubule
Collecting duct
What are the two types of nephrons?
Cortical
Juxtamedullary
Differences between cortical and juxtamedullary nephrons?
Cortical: loop of Henle only penetrates outer renal medulla, short loop of Henle, reduced/no vasa recta, small glomeruli, low glomerular filtration rate, 85% of nephrons, excretory/regulatory functions
Juxtamedulla: loop of Henle penetrates deep into medulla, long loop of Henle, large vasa recta, large glomeruli, high glomerular filtration rate, 15% of nephrons, concentrating/diluting urea
How does blood enter the glomerulus?
Afferent arteriole
How does blood leave the glomerulus?
Efferent arteriole
How to calculate urinary excretion rate?
Filtration rate - re-absorption rate + secretion rate
What three processes are involved in renal excretion (urine production)?
Glomerular filtration
Active tubular secretion
Passive tubular re-absorption from tubule
What is glomerular filtration?
Movement of fluid and solutes from the glomerular capillaries into Bowman’s space
What is tubular re-absorption?
Movement of materials from the filtrate in the tubules into the peri-tubular capillaries
What is tubular secretion?
Secretion of solutes from the peri-tubular capillaries into the tubules
Where and how in the nephron is glucose re-absorbed?
Proximal convoluted tubule, ~100%
By two active sodium-dependent glucose transporters (SGLT 1 and 2)
Where and how in the nephron are proteins/amino acids re-absorbed?
Proximal convoluted tubule, ~100%
Active transport
Where in the nephron are vitamins re-absorbed?
Proximal convoluted tubule
Where in the nephron is lactate re-absorbed?
Proximal convoluted tubule
Where in the nephron is creatinine secreted?
Proximal convoluted tubule
Where and how in the nephron is urea re-absorbed/secreted?
Mainly secreted in distal convoluted tubule
Where and how in the nephron is sodium re-absorbed?
65% actively in proximal convoluted tubule
25% actively in thick ascending limb of loop of Henle
5% actively in distal convoluted tubule
5% actively in collecting ducts, stimulated by aldosterone
Where and how in the nephron is chloride re-absorbed?
Symport with sodium in proximal convoluted tubule
By diffusion in ascending loop of Henle and distal convoluted tubule
Symport in collecting ducts
Where and how in the nephron is water re-absorbed?
67% osmotically with solutes in proximal convoluted tubule
15% osmotically in descending limb of loop of Henle
Distal convoluted tubule and collecting ducts by osmosis controlled by ADH
Where and how in the nephron are hydrogen ions secreted?
By diffusion into proximal convoluted tubule
Actively into distal convoluted tubule and collecting ducts
Where and how in the nephron is ammonium secreted?
By diffusion in proximal convoluted tubule, distal convoluted tubule and collecting ducts
Where and how in the nephron is bicarbonate re-absorbed?
80-90% in proximal convoluted tubule symport with sodium
In ascending limb of loop of Henle symport with sodium and antiport with chloride
In collecting ducts antiport with chloride
Where and how in the nephron is potassium re-absorbed and secreted?
65% re absorbed in proximal convoluted tubule by diffusion
20% re absorbed in thick ascending limb of loop of Henle, symport
Actively secreted into distal convoluted tubule
Active secretion controlled by aldosterone in collecting ducts
Where and how in the nephron is calcium re-absorbed?
Proximal convoluted tubule and thick ascending limb of loop of Henle by diffusion
Actively collection ducts if parathyroid hormone present
Where and how in the nephron is magnesium re-absorbed?
By diffusion in proximal convoluted tubule, thick ascending limb of loop of Henle, distal convoluted tubule
Where and how in the nephron is phosphate re-absorbed?
85% by diffusion in proximal convoluted tubule (inhibited by parathyroid hormone)
By diffusion in distal convoluted tubule
Difference between filtrate and plasma?
Filtrate is protein free
Where does the glomerular filtrate need to pass through?
Pores between endothelial cells of the glomerular capillary
Basement membrane
Podocytes
What can be filtered through the glomerular endothelium?
Large pores 70-100 nanometres
Solutes, plasma proteins and fluids
Blood cells cannot pass
Role of the glomerular basement membrane?
Prevents plasma proteins from being filtered out of bloodstream
Role of the glomerular podocytes?
Wrap around capillaries but leave slits, filtration slits, a thin diaphragm between the slits acts as the final filtration barrier
Size of neutral solutes and glomerular filtration?
<180 nanometres freely filtered
>180 <360 nanometres filtered to various degrees
>360 nanometres not freely filtered
How to calculate net filtration pressure?
Hydrostatic pressure of capillary - (colloid osmotic pressure of blood + hydrostatic pressure of bowman’s capsule)
E.g. 55-(15+30) = 10
How to calculate GFR?
Net filtration rate x filtration coefficient (Kf)
What is the filtration coefficient?
Kf
Based on surface area of glomerular capillaries and hydraulic conductivity
What are the three pressures involved in glomerular filtration?
Pgc is glomerular capillary hydrostatic pressure
Pbc is the back pressure built up in the bowman’s capsule
πgc is the colloidal osmotic pressure of the glomerular capillary plasma
What is the tubuloglomerular feedback mechanism?
Involved in autoregulation
Sensed by changes in GFR, renal blood flow and NaCl
Stimulates either relaxation or constriction of afferent arteriole
What is extrinsic regulation of GFR?
Sympathetic nervous system releases norepinephrine-> adrenal medulla releases epinephrine -> leads to constriction of afferent arteriole and inhibition of glomerular filtration
What is renal clearance?
Volume of plasma that is cleared of a specific substance in time unit
Renal clearance calculation?
Renal clearance (RC) = concentration of substance in urine (CU) x flow rate of urine formation (V) / concentration of same substance in plasma (CP)
RC=CUxV/CP
What is creatinine clearance?
To assay the excretory function of the kidneys (ml/min of filtered creatinine). It is a bio marker to estimate GFR
Creatinine clearance formula?
(140-age) x mass in kg x constant
————————————————
Serum creatinine
Male =1.23
Female= 1.04
What is body fluids usually measured in?
Milliosmoles (mom)
What is a milliosmole?
An osmole is an amount of a substance that contributes to the osmotic pressure of a solution. A milliosmole is one-thousandth of an osmole
The solute concentration of body fluids is kept at around….. by the kidneys
300 mom
How do the kidneys keep body fluids at a constant solute concentration?
Counter current mechanism
What is micturition?
Urination
Steps of micturition?
Urine is made in the kidneys.
Urine is stored in the bladder.
The sphincter muscles relax.
The bladder muscle (detrusor) contracts.
The bladder is emptied through the urethra and urine is removed from the body.
What is countercurrent multiplication?
the process of using energy to
generate an osmotic gradient that enables
you to reabsorb water from the tubular
fluid and produce concentrated urine.
Where does the countercurrent multiplication take place?
Loop of Henle, mainly juxtamedullary nephrons
Countercurrent multiplication process?
Step 1: Assume that the Henle loop is filled with a concentration of 300mOsm/L, which is the same as the concentration leaving the proximal tubules.
Step 2: The thick ascending limb of the Henle loop’s active ion pump lowers the concentration inside the tubule and raises the interstitial concentration.
Step 3: Due to osmosis of water out of the descending limb, the tubular fluid in the descending limb and the interstitial fluid quickly approach osmotic equilibrium.
Step 4: Additional fluid flow from the proximal tubule into the Henle loop, causing hyperosmotic fluid previously generated in the descending limb to flow into the ascending limb.
Step 5: More ions are pushed into the interstitium while water remains in the tubular fluid, resulting in a 200-mOsm/L osmotic gradient.
Step 6: As the hyperosmotic tubular fluid from the descending limb flows into the ascending limb, additional solute is constantly pushed out of the tubules and deposited into the medullary interstitium.
Step 7: These stages are repeated over and over, with the net result of bringing more and more solute to the medulla in excess of water. Over time, this process traps solutes in the medulla and magnifies the concentration gradient generated by active pumping of ions out of the thick ascending limb. Eventually raising the interstitial fluid osmolarity to 1200- 1400 mOsm/L .
What happens when blood osmolarity changes?
Neural signal is sent to the hypothalamus to increase or decrease ADH
What is ADH?
Antidiuretic hormone
What detects changes in blood osmolarity?
Osmoreceptors
How does renin angiotensin system work?
Blood volume/sodium levels detected as low -> juxta-glomerular cells stimulated by b1-adrenergic receptors-> releases enzyme called renin -> renin acts on angiotensinogen -> angiotensin I released -> converted to angiotensin II -> map increases -> adrenal cortex releases aldosterone-> increase in both systemic and glomerular hydrostatic pressure
What is normal blood pH?
7.4
How are the kidneys involved in acid/base balance?
Reabsorption of bicarbonate
Excretion of hydrogen ions
What causes altitude sickness?
Decreased oxygen pressure causes increased rate and depth of respiration-> leading to pCO2 levels to drop and respiratory alkalosis to occur -> over time increased bicarbonate excretion causes pH to go back to normal and allowing respiratory rate to increase to compensate for the alkalosis
What hormone helps renal calcium regulation?
Parathyroid hormone
What are the two main types of cells in the nervous system?
Neurons
Glial cells
What are neurons?
Specialised cells in the nervous system for the transmission of signals and communication with each other through chemical synapses
What are glial cells?
Cells in the nervous system that surround and support neurons
What are the three types of glial cells in the central nervous system?
Astrocytes
Oligodendrocytes
Microglia
What are the three types of glial cells in the peripheral nervous system?
Schwann cells
Enteric glial cells
Satellite cells
What is the nervous system split up into?
Central
Peripheral
What is the peripheral nervous system split up into?
Autonomic
Somatic
What is the autonomic nervous system split up into?
Sympathetic
Parasympathetic
Purpose of the somatic nervous system?
consists of nerves that go to the skin and muscles and is involved in conscious activities
Purpose of the autonomic nervous system?
consists of nerves that connect the CNS to the visceral organs such as the heart, stomach, and intestines. It mediates unconscious activities.
What does the sympathetic nervous system do?
role in responding to dangerous or stressful situations.
What does the parasympathetic nervous system do?
controls bodily functions when a person is at rest.
Effects of sympathetic nervous system?
Increase heart rate.
Dilation of the pupils
Secretion of sweat glands
Dilated muscles
Increased alertness
Slowing down or stopping digestion
Relaxation of the bladder
Effects of parasympathetic nervous system?
Salivation: As part of its rest-and-digest function, the PSNS stimulates production of saliva, which contains enzymes to help your food digest.
Lacrimation: ie making tears. Tears keep your eyes lubricated, preserving their delicate tissues.
Urination: The PSNS contracts the bladder, which squeezes it so urine can come out.
Digestion: The PSNS stimulates the release of saliva to promote digestion. It also enacts peristalsis, or the movement of the stomach and intestines, to digest food as well as release bile for the body to digest fats.
Defecation: The PSNS constricts the sphincters in the intestine and moves digested food material down the digestive tract so a person can have a bowel movement.
What neurotransmitter does the parasympathetic nervous system use?
Acetylcholine
What neurotransmitter does the sympathetic nervous system use?
Mainly Noradrenaline
What is the main excitory neurotransmitter of the brain?
Glutamate
What is the main inhibitory neurotransmitter of the brain?
GABA (Gamma-aminobutyric acid)
Astrocyte structure and function?
In central nervous system
Most abundant, versatile and highly branched glial cells
Cling to neurons, synaptic endings, and capillaries
Help maintain the ionic and chemical environment
Microglial structure and function?
In central nervous system
Small, ovoid cells with thorny processes that touch and monitor neurons
Migrate towards injured neurons
Can transform to phagocytose microorganisms and neuronal debris
Oligodendrocyte structure and function?
Branched cells
The processes wrap central nervous system nerves fibres, forming insulating myelin sheaths (thicker nerve fibres)
Ependymal cell structure and function?
Range in shape from squamous to columnar
May be ciliated- cilia beat to circulate cerebrospinal fluid
Line the central cavities of the brain and spinal column
Form permeable barrier between cerebrospinal fluid in cavities and tissue fluid bathing central nervous system cells
What do satellite and Schwann cells do?
Surround neurons in peripheral nervous system, forming myelin
Purpose of the myelin sheath?
myelin sheath allows electrical impulses to transmit quickly and efficiently along the nerve cells
Features of neurons?
Extreme longevity
Usually amitotic
High metabolic rate
All have cell body and one or more processes
What is the axon?
where electrical impulses from the neuron travel away to be received by other neurons
What are dendrites?
tree-like extensions at the beginning of a neuron that help increase the surface area of the cell body. These tiny protrusions receive information from other neurons and transmit electrical stimulation to the soma
Another name for the neuron cell body?
Soma
How is an action potential conducted?
1) neurotransmitter opens ligand-gated channel
2) positive ions (na+) enter cell to make it less negative
3) if net influx is positive and hits threshold potential then voltage-gated sodium channels open
4) influx of sodium ions causes a chain reaction down axon
5) membrane potential reaches +40mv and sodium stops entering
6) k+ voltage-gated channels open and K+ flows out causing membrane potential to become more negative -10mv
7) neuron becomes hyperpolarised due to k+ flowing out and K+/na+ pumps, -75mv
8) all channels close and returns to resting membrane potential -65mv
How does the neuron sheath speed up electrical impulse condition?
Action potential only conducts in gaps in myelin sheath called nodes of Ranvier
Meaning it can ‘skip’ sections
Called saltatory conduction
Picture of action potential graph
What is the resting membrane potential?
~70mv
What are the three connective tissues layers of muscle?
Epimysium
Perimysium
Endomysium
What is the epimysium?
Outermost layer. Irregular dense connective tissue that allows muscle to contract, move independently and maintain its structure. It also separates muscle from nearby organs and tissues
How are muscles attached?
Either directly to other organs or tissues or indirectly by tendons
What is the perimysium?
Middle layer of connective tissue. Organise muscle fibres into bundles
What is the endomysium?
Innermost layer of connective tissue. A thin layer of collagen and reticular fibres, surrounds the extra cellular matrix of the cells and plays a role in transferring force produced by the muscle fibres to the tendons.
What is the sarcomere?
The smallest contractile unit of the muscle fibre.
Contains myofibrils.
Middle of sarcomere called the M-line.
Borders called Z disks
What is the M-line made up of?
Myomesin proteins
What attaches to the M-line?
Myosin
What are the Z disks made up of?
Alpha actin proteins
What attaches to the Z disks?
Actin
What is a muscle fibre?
An individual muscle cell. Each runs the entire length of the muscle