SUGER Flashcards
What 3 things does growth hormone stimulate
Protein synthesis
Lipolysis
Glucose metabolism
Name the 3 controlling steps of RAAS initiation
macula densa in the distal convoluted tubule detect LESS NaCl in the tubule
• Sympathetic stimulation
• Little or no arteriolar stretch (i.e. low blood volume due to the lack of Na+ and thus H2O)
What releases renin
Renin is secreted by juxtaglomerular cells located in the afferent arterioles
What cleaves angiotensinogen to angiotensin I
Renin
Where is angiotensinogen produced
Liver
Describe the conversion of angiotensin I to angiotensin II
Angiotensin I is biologically inactive
Cleaved to angiotensin II (active agent) by angiotensin-converting enzyme (ACE)
Where is ACE produced
Lungs
How does angiotensin II cause the secretion of aldosterone
Stimulates the cells of the zona glomerulosa in the adrenal cortex of the supradrenal/adrenal glands to secrete the steroid hormone called ALDOSTERONE
What is the effect of angiotensin II on bp
Is a vasoconstrictor, which results in vasoconstriction especially at the efferent arteriole, this in turn results in the increase in pressure resulting in an increased GFR
How does aldosterone cause increase blood volume
Aldosterone acts on principal cells of the collecting duct which results in increased Na+ and H2O reabsorption
What effect does angiotensin II have on the hypothalamus
Stimulates thirst and ADH release resulting in water retention
Why is creatinine used as a marker substance
Freely filtered
Not metabolised
Not secreted or reabsorbed
Where is atrial natriuretic peptide synthesised and secreted from
Cardiac atrial cells
Effects of ANP
Acts as a renal vasodilator > afferent arteriole dilator > increased GFR
Inhibits Na+ reabsorption
Inhibits aldosterone
What is parathyroid hormone released in response to
Low plasma [Ca2+]
Effect of PTH on the distal tubule when [Ca] is low
PTH binds with receptors and causes an increase in Ca2+ uptake from the tubule
Stimulates the formation of Vit D
What are the 2 cell types found in the CT
Give their functions
Principal cells - respond to aldosterone and ADH, reabsorption of Na and water
Intercalated cells - secrete acid or HCO3
Functions of skin
- Barrier to infection
- Thermoregulation
- Protection against trauma
- Protection against UV
- Vitamin D synthesis
- Regulation of H2O loss
What are the 3 basic layers of the skin
Epidermis
Dermis
Subcutaneous tissue
What are the layers of the epidermis
Stratum corneum S lucidum S granulosum S spinosum S basale
Come Let’s Get Sun Burnt
How does the skin prevent transepidermal water loss
Tight junctions between cells in stratum granulosum, epidermal lipids and keratin in stratum corneum
Which layer of the skin is vitamin D stored
Subcutaneous layer
What is the pH of healthy skin
5.5
Describe the healthy skin barrier
1) filaggrin produces natural moisturising factor (NMF) - this helps maintain skins hydration and an acidic environment on the outer surface of the stratum corneum
2) Balance the introduction of new cells in the basal layer.
3) lipid lamellas keep water inside the cell. Irritant and allergens tend to bounce off surface of skin
What is the affect of an increased pH on the skin
Degradatory proteases are no longer inhibited so they breakdown the corneodesmosomes
Increase pH also impairs the formation of lipid lamellae - allows skin cells to move apart which reduces water retention
What are sebaceous glands responsible for
Producing a lipid rich sebum which protects the hair
When does acne occur
When hair follicles become blocked with sebum, bacteria and skin cells
What type epithelium is found in skin
Keratinising stratified squamous epithelium
What is the arterial supply to the adrenals
- Superior adrenal artery from inferior phrenic
- Middle adrenal artery from abdominal aorta
- Inferior adrenal artery from renal artery
What is the difference in venous drainage between the right and left adrenals
Right adrenal vein drains directly into IVF
left adrenal vein drain first into the left renal vein then into the IVF
What innervates the adrenals
Splanchnic nerve
What are the 3 parts of the adrenal cortex (outer to inner)
State what each produce
Zona glomerulosa - produces mineralocorticoids (aldosterone)
Zona fasciculata - glucocorticoids (cortisol)
Zona reticularis -Sex steroids (androgens) and cortisol
GFR, Make Good Sex
Which hormones are secreted from the adrenal medulla
Adrenaline
Noradrenaline
What is the precursor to all corticosteroids
Cholesterol
What % of cortisol in circulation is free
5%
Functions of cortisol
Inhibit growth and reproduction Reduction of inflammation Reduction of bone formation Gluconeogenesis and carb metabolism Proteolysis and lipolysis
What is the effect of adrenaline and noradrenaline when released in response to stress
Increase HR and BP dilates pupil Inhibits insulin release Increases glucagon release Increase in sweating
What are the receptors for adrenaline and noradrenaline
Adrenaline - high affinity beta receptors
Nor - high affinity alpha
What affect does cortisol have on insulin
Antagonistic affect as it stops it from acting in cells as cortisol wants to maintain high blood glucose for stressful situations
What spinal levels does the thyroid gland sit between
Anterior neck between C5 - T1
What divides the thyroid into its left and right lobe
The isthmus
What 2 muscles does the thyroid lie between
Sternohyoid and sternothyroid muscle
What can be found on the posterior surface of the thyroid
4 parathyroid glands
What is the blood supply to the thyroid
Superior thyroid arteries
- 1st branch of external carotid artery
- Supplies anterior and superior portions
Inferior thyroid arteries
- branch of subclavian artery
- Supplies posterior and inferior aspect
What innervates the thyroid and parathyroid gland
Sympathetic trunk
Name the thyroid hormones T3 and T4
T3 - triiodothyronine
T4 - thyroxine
Describe the process of thyroid hormone secretion ( hypothalamic-pituitary-thyroid axis)
- Thyrotropin releasing hormone (TRH ) released by hypothalamus in response to neural inputs
- TSH then released by anterior pituitary gland
- This acts on thyroid gland to secrete T3 and 4
- T4 is converted to T3 and acts on its target cells
- TSH and TRH are inhibited through negative feedback
What are the metabolic actions of T3
- stimulates carb absorption in small intestine and increases fatty acid release from adipocytes
- maintain high BMR
- increases body temp
How is T3 important in brain maturation
- formation of axon terminals
- formation of synapses
- growth of dendrites and dendritic extensions
- formation of myelin
What is the physiological difference between T3 and 4
T4 is most abundant but T3 is the biologically active form of T4
Where do the parathyroid glands drain into
Thyroid plexus
Function of parathyroid glands
Regulate calcium and phosphate levels
Secretes parathyroid hormone in response to low Ca or high phosphate
Effects of PTH
• Increases calcium reabsorption in renal distal tubule
• Increases intestinal calcium absorption (via activation
of vitamin D) – duodenum and jejunum
• Increases calcium release from bone (stimulated
osteoclasts activity)
• Decreases phosphate reabsorption
• Binds to G protein coupled receptors
Describe the difference in shape between right and left adrenal glands
Right is pyramidal
Left is crescent shaped
The kidneys are encased in layers of fat and fascia
Give them deep to superficial
Renal capsule – tough fibrous capsule.
Perinephric fat – collection of extraperitoneal fat.
Renal fascia (also known as Gerota’s fascia or perirenal fascia) – encloses the kidneys and the suprarenal glands.
Paranephric fat – mainly located on the posterolateral aspect of the kidney.
What is the difference between positive and negative feedback
Negative - as a hormone increase in [ ], it INHIBITS the release of another
In positive feedback it PROMOTES the release of another
Name the 6 hormones produced by the anterior pituitary
hint: FLAGTOP
FSH – Follicle Stimulating Hormone LH – Luteinizing Hormone ACTH – Adrenocorticotropic hormone GH – Growth Hormone TSH – Thyroid Stimulating Hormone O - ignore Prolactin
Name the 2 hormones produced by the posterior pituitary gland
ADH/ Vasopressin
oxytocin
What are hypophysiotropic hormones
Hypothalamic hormones that control secretion of anterior pituitary
hormones
What is the name of the hypophysiotropic hormone that stimulates the release of LH and FSH
Gonadotropin-releasing hormone (GnRH)
What effect does (LH) and (FSH) have on males
LH - stimulates production of testosterone by leydig cells
FSH - Stimulates spermatogenesis by stimulating sertoli cells to produce androgen binding protein
What effect does luteinising hormone (LH) and follicle stimulating hormone (FSH) have on females
LH -> Stimulates ovulation + ovarian follicle maturation + corpus luteum formation.
FSH -> regulates development + growth of ovarian follicle + affects 1st half of menstrual cycle
Name the hypophysiotropic hormone that stimulates the release of ACTH
Corticotropin-releasing-hormone
Describe the HPA axis
Adrenal
Corticotropin releasing hormone stimulates Adrenocorticotropic hormone which causes an increase in cortisol production in the zona fasciculata of adrenal cortex
Name the hypophysiotropic hormone that stimulates the release of growth hormone
Growth hormone releasing hormone (GHRH)
What processes are GH involved in
Skeletal growth and bone density Muscle strength Protein synthesis Glycogenolysis Lipolysis
What hormone inhibits GH
somatostatin
Where is GH produced
Somatotrophs
What causes the release of prolactin
Suckling
Thyroid releasing hormone
What inhibits the release of prolactin
dopamine
Functions of prolactin
Initiate breast milk production
Maintain milk production once established
How are the anterior and posterior pituitary different
- Anterior has no neural connection to hypothalamus while posterior does
- posterior pituitary STORES and releases hormones, anterior SYNTHESISES and releases hormones
Where is oxytocin synthesised
paraventricular nucleus of hypothalamus
Function of oxytocin
- Contraction of smooth muscle in the breast to promote milk ejection during lactation
- acts on the uterus to cause uterine contractions during labour-> promoting onset of labour
- Exerts positive feedback on itself
Where is anti diuretic hormone produced
Supraoptic nucleus of hypothalamus
Give 5 things that ADH is released in response to
- Increased osmotic pressure in blood
- Decreased blood volume
- Trauma/stress
- Increased PCO2
- Decreased PO2
Describe the negative feedback of ADH
- Osmoreceptors in the hypothalamus detect change
- ADH binds to V2 receptors on the collecting ducts -> increased expression of aquaporin 2 in cortical collecting duct
- This allows the passage of water from the CD into the blood to reduce the plasma osmolality -> ↑water reabsorption and blood volume
- vasoconstriction of SM cells around blood vessels increases bp
How does the anterior pituitary receive its blood supply
through portal venous circulation called hypothalamo-hypophyseal portal vessels
What are the 3 main cell types in islets of langerhans
State what each release
- Delta cells - somatostatin (inhibitors)
- Alpha cells - glucagon
- Beta cells - insulin
How is the active form of insulin produced
A and B chains connected by C peptide - proinsulin
Insulin is produced when C peptide is cleaved
Function of insulin
- Reduces glucose output by liver
- Increase storage of glucose, FA + aa
- Stops breakdown of fat + muscle
Describe the feedback loop when blood glucose rises
Insulin is released and glucagon release is inhibited
There is increased glycogenesis in the liver and muscles
Gluconeogenesis is inhibited
Describe the feedback loop when glucose levels fall
Glucagon is released and insulin release is inhibited
Glycogenolysis occurs to release glucose from the liver and muscles into the blood
Gluconeogenesis occurs
Glucose moves into beta cells via which channel
GLUT2 channel
What causes depolarisation of the beta cells membrane
Metabolism of glucose occurs which makes ATP
ATP causes the closure of ATP-sensitive potassium channels
This causes the membrane to depolarise
How is insulin released from beta cells after membrane depolarisation
Depolarisation causes voltage-gated Ca channels to open inducing an influx of Ca2+
Ca2+ binds to vesicles containing insulin
These vesicles fuse with the cell membrane and release insulin
How does insulin cause a decrease in blood glucose level after leaving beta cells
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 (uptake) into cell -> ↓blood glucose level
What secretes melatonin
pineal gland
What do C cells secrete
calcitonin
What 3 cells does the parathyroid contain
chief cells
oxyphils
adipocytes
Histologically, what can be used to determine whether the specimen is thyroid or parathyroid
Thyroid may contain calcium oxalate crystals but parathyroid wont
Where are islets of langerhans most abundant in the pancreas
pancreatic tail
What is the most prominent layer of the adrenal cortex
Zona fasciculata
Where is spermicide produced
Seminiferous tubule
Anatomy of the testes : SREEVE UP
Seminiferous tubules Rete testes Efferent ducts Epididymis Vas deferens Ejaculatory duct Urethra Penile urethra
What is syngamy
Fusion of the male and female pronuclei
What does a pregnant womens ‘water breaking’ describe
Amniotic sac ruptures, amniotic fluid flows through the vagina
Parasympathetic innervation to detrusor
Pelvic splanchnic nerve
S2-4
Sympathetic innervation of detrusor
Hypogastric nerve
T12-L2
Describe branching of the renal artery
Renal artery -> segmental arteries -> interlobar arteries -> arcuate arteries -> interlobular arteries -> afferent arterioles -> glomerular capillaries -> efferent arteriole -> peritubular capillaries
What innervates the external urethral sphincter
Pudendal nerve
S2-4
Where are C cells located
Thyroid gland
Which layer of the epidermis is acellular
Stratum corneum
Primary event in the switch from storage to voiding
Relaxation of urethral sphincter
What effect does aldosterone have on transporter protein in DCT
Increase in Na - K exchange transporters
What are incretins
Secreted by endothelial cells in GI tract.
Functions to increase the effect of insulin in response to glucose
Give 2 examples of incretins
Glucagon like peptide
Glucagon dependent insulinotropic peptide
Epithelium lining the vas deferens
Pseudostratified columnar
What secretes relaxin
Placenta and ovaries
