sugar Flashcards
describe negative feedback
As a hormone increases in concentration, it inhibits the release of another hormone.
describe positive feedback
As a hormone increases in concentration, it promotes the release of a hormone
what hormones does the anterior pituitary secrete
(FLAGTOP) FSH – Follicle Stimulating Hormone LH – Luteinizing Hormone ACTH – Adrenocorticotropic hormone GH – Growth Hormone TSH – Thyroid Stimulating Hormone O – MelanOcyte stimulating hormone Prolactin
what hormones does the posterior pituitary secrete
ADH/Vasopressin
Oxytocin
describe the male HPG axis
LH -> Leydig cells -> Testosterone
FSH -> Sertoli Cells -> Stimulates production of ABP -> Spermatogenesis
describe the female HPG axis
LH -> Stimulates ovulation + ovarian follicle maturation + corpus luteum formation.
FSH -> regulates development + growth of ovarian follicle + affects 1st half of menstrual cycle
describe the oestrogen feedback mechanisms on the HPG axis
Moderate levels of oestrogen present will exert negative feedback on FSH and LH.
High oestrogen (with low progesterone) exerts positive feedback on LH and FSH.
Oestrogen in the presence of progesterone exerts negative feedback.
describe the HPA axis
CRH -> ACTH (corticotrohps) -> Cortisol (ZF of adrenal cortex)
cortisol functions
Gluconeogenesis and carbohydrate metabolism
Reduction of inflammation
Proteolysis and lipolysis
Reduction of bone formation, which can lead to osteoporosis over time
describe the HPS axis
GHRH -> GH (somatotrophs)
Somatostatin (SST) -/-> GH
what is GH involved in
Skeletal growth and bone density Muscle strength Protein synthesis Glycogenolysis Lipolysis
describe the HPT axis
TRH -> TSH -> T3/T4
what does TSH (thyroid stimulating hormone) do
increase metabolism
describe the release of prolactin
- Suckling causes the release of prolactin as well as TRH.
- Dopamine inhibits release of prolactin
what are the functions of prolactin
Initiate milk production in the breasts
Maintain milk production once is has been established
what is the peptide hormone of GnRH
FSH + LH
what is the peptide hormone of CRH
ACTH
what is the peptide hormone of GHRH
GH
what is the peptide hormone of TRH
TSH
where is oxytocin synthesised and stores?
synthesised in hypothalamus (paraventricular nucleus)
stored in posterior pituitary
what is the function of oxytocin
Oxytocin acts on the breasts to allow milk to move through the lactiferous ducts to be expressed through the nipple -> milk ejection during lactation
It also acts on the uterus to cause uterine contractions during labour-> promoting onset of labour
Oxytocin exerts positive feedback on itself
where is ADH synthesised
hypothalamus - supraoptic nucleus
how does ADH control osmolality
Osmoreceptors in the hypothalamus detect change
ADH binds to V2 receptors on the collecting ducts -> mobilisation of aquaporin 2 (AQP2) + insertion into cell membrane
These allow the passage of water from the collecting duct into the blood to reduce the plasma osmolality -> ↑water reabsorption
how does ADH maintain Blood pressure
Maintains BP by acting on smooth muscle cells -> vasoconstriction -> ↑BP
which hormone inhibits GHRH
somatostatin
what do the alpha cells of the islets of langerhans secrete
glucagon
what do the beta cells of the islets of langerhans secrete
insulin
what do the delta cells of the islets of langerhans secrete
somatostatin
describe the mechanism of insulin secretion
- Glucose moves into beta cells via GLUT2 channel
- ATP is made
Closure of ATP-sensitive potassium channels - Depolarisation of the beta cell membrane
- Opening of voltage-gated calcium channels
- Vesicles containing insulin fuse with the cell membrane
describe the action of insulin in lowering blood glucose
Insulin binds to insulin receptors on muscle + fat cells
Triggers intracellular signalling cascade -> mobilisation of intracellular GLUT4 vesicles to cell membrane
GLUT4 vesicle integrates into cell membrane -> ↑number of membrane glucose transporters -> ↑rate of glucose facilitated diffusion into cell -> ↓blood glucose level
describe what happens when glucose levels rise
Insulin is released and glucagon release is inhibited
There is increased glycogenesis in the liver and muscles
Gluconeogenesis is inhibited
This reduces the blood glucose level
what level is the thyroid gland situated
C5-T1
what divides the thyroid into 2 lobes
isthmus
what 2 muscles does the thyroid gland lie between
sternohyoid and sternothyroid
how many parathyroid glands are there and where are they located
4
posterior surface of the thyroid
what is the blood supply to the thyroid?
Superior thyroid arteries
Branch of external carotid artery.
Supply superior + anterior portion of gland
Inferior thyroid arteries
Branching of subclavian artery
Supplies posterior inferior aspect of gland
what protein is produced by the follicular cells
thyroglobulin
describe the production of T3 + T4 (ATE ICE)
A - (secondary) active transport of iodide via Na/I symporter
T - thyroglobulin is produced in the follicular cells
E - exocytosis of thyroglobulin into the follicular lumen
I - iodination of tyrosine residues on thyroglobulin (thyroid peroxidase) to form monoiodothyronine (MIT) and diiodothyronine (DIT)
C - coupling of MIT and DIT (T3) and DIT and DIT (T4)
E - endocytosis of T3 and T4 into follicular cells. Proteolysis occurs to free T3 and T4 from thyroglobulin
what is the function of T3 and T4
increases BMR & important in brain maturation
how does T3 increase BMR
- T3 -> stimulates carbohydrate absorption in SI , ↑FA release from adipocytes
- ↑BMR by providing more energy for metabolism
- ↑body temp (homeostasis)
what are the 3 main layers to the skin
epidermis
dermis
subcutaneous
what are the 5 layers of the epidermis (top to bottom) (Come, Let’s Get Sun Burnt)
Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum basale
what is adhesion in the skin provided by
Primary adherens junctions
Desmosomes (stratum spinosum)
Corneo-desmosomes keep corneocytes together
Tight junctions – epithelial layer (stratus granulosum)
Help with providing waterproofing
what is the function of NMF
Filaggrin -> natural moisturising factor (NMF)
NMF allows the skin to remain hydrated and maintains the slightly acidic pH the skin has
what is the purpose of the skin being acidic
Acidity prevents protease activity to stop the breakdown of corneodesmosomes.
It also aids with the formation of the lipid lamellae.
what is the affect of increased pH on the skin
The proteases are no longer inhibited by the low pH so they break down the corneodesmosomes
The increased pH also impairs the formation of the lipid lamellae
This allows the skin cells to move apart which reduces water retention in the skin
Allergens can then penetrate
how do allergens create an inflammatory response
Allergen penetrates skin + attracts lymphocyte -> releases inflammatory cytokines -> inflammatory response
what is the cause of red skin
dilation of vessels to bring more lymphocytes to area
what is the cause of itchy skin
stimulation of proprioceptors by the release of histamine (from mast cells) or thermal/mechanical mediators
what is the cause of dry skin
skin cells leaking water
what do sebaceous glands do
produce a lipid-rich sebum which protects the hair
how does acne occur
Acne occurs when the hair follicle becomes blocked with sebum, skin cells, and bacteria.
Sebum -> free fatty acids (by bacteria) -> inflammation & attraction of neutrophils -> pus formation
what is the automatic nervous supply to the bladder
SympathetiC – HypogastriC nerves T12-L2 -> relaxation of detrusor muscle -> urine retention
ParaSympathetic – Pelvic Splanchnic nerves S2-4 -> contraction of detrusor muscle -> micturition stimulation
what is the somatic nervous supply to the bladder
Somatic system (voluntary) -> Pudendal nerves S2-4 -> Innervate EUS -> constricts (storage) or relaxes (micturition)
describe the process of bladder filling/ storage
Parasympathetic input to detrusor muscles is minimal -> detrusor muscle relaxes.
Strong sympathetic input to Internal urethral sphincter + Strong somatic motor neuron input to External urethral sphincter -> Both Sphincters closed
This allows the bladder to expand to prevent an increase in pressure as the volume increases (stress-relaxation phenomenon)
describe the bladder stretch reflex arc
Bladder fills and stretches -> activating stretch receptors
Afferent sensory nerves transmit signal to brain
Interneurons relay signal to parasympathetic efferent nerves (pelvic nerve)
Contracts detrusor muscle -> stimulate micturition
describe the mechanism of voiding
Detrusor muscle contracts to increase the pressure in the bladder
Internal urethral sphincter relaxes
Once it’s appropriate to void, the external urethral sphincter will be consciously relaxed to allow voiding
what part of the adrenal gland secretes cortisol
zona fasciculata
what part of the adrenal gland secretes androgens
zona reticularis
what part of the adrenal gland secretes mineralocorticoids (aldosterone)
zona glomerulosa
what does the adrenal medulla secrete
adrenaline
what nerve innervates the external urethral sphincter and what nerve roots does it comprise of
pudendal nerve S2-S4
what are the functions of the skin
barrier to infection thermoregulation protect against trauma protection against UV vitamin D synthesis regulate H2O loss
what are corneocytes filled with
NMF
what is desquamation
when mature corneocytes are shed from the surface of the stratum corneum
what is the pH of normal skin
5.5
what does the lipid lamellae do
keep water inside the skin cells
describe the brick wall model
bricks = corneocytes
iron rods = corneodesmosomes
cement - lipid lamellae
what is the role of vitamin D for the skin
essential in producing the anti-microbial peptides necessary to defend the skin from bacteria and viruses
at what level are the kidneys found
T12 & L3
which kidney is lower
right - pushed down by liver
where is the hilum of the right kidney
L2
where is the hilum of the left kidney
L1
what is the cortex of the kidney composed of
renal corpuscles (glomerulus & bowman’s capsule) and the proximal and distal convoluted tubule
what is a medullary ray
collection of loop of henle tubules in the cortex - concentrate urine. and collecting ducts
what is the medulla of the kidney comprised of
no real corpuscles or glomeruli
loops of henle, collecting ducts and blood vessels
describe the composition of the kidney pelvis
lined by transitional epithelium
tips of medullary pyramids project into pelvis - at this point the pyramids are composed purely of collecting ducts
describe the blood supply to the kidneys
renal artery (L1 of aorta) -> segmental -> interlobar -> arcuate-> interlobular -> afferent arterioles
what many nephrons in the kidney
1 million in each
what is the role of the renal corpuscle
filtering
what is the role of the PCT
reabsorbing solutes
what is the role of the loop of henle
concentrating urine
what is the role of the DCT
reabsorbing more water and solutes
what is the role of the collecting duct
reabsorbing water and controlling acid-base & ion balance
what is the glomerular tuft supported by
smooth muscle mesangial cells
what are the 3 main functions of the mesangial cells
- structural support
2, contraction of muscles in the glomerulus to reduce GFR
what are the 2 components of the juxtaglomerular apparatus
afferent arteriole & distal convoluted tubule
what is the role of granular cells
detect blood pressure and secrete renin in response to a reduction in BP