Endocrine & Renal Flashcards
What are the three general classes of hormones (i.e. chemical structure)?
Steroid made from cholesterol
Non-steroid proteins or polypeptides
Non-steroid derivatives of the amino-acid tyrosine
Where are steroid hormones made?
Adrenal glands and gonads (testes or ovaries)
How do steroid hormones travel to and enact changes on their target cells?
They travel through the bloodstream bound to transport proteins to reach target cells. Since steroid hormones are relatively small, and non-polar, they diffuse right across the phospholipid membrane of target cells. Inside the cell, they bind to a receptor that activate certain genes in the nucleus
How do peptide hormones travel to and enact changes on their target cells?
Peptide hormones, like insulin and glucagon, travel through the bloodstream to reach target cells, they bind to cell surface receptor proteins on the cell membrane that activates various proteins and enzymes that create changes in gene expression within the cell.
How do amino-acid hormones travel to and enact changes on their target cells?
Different hormones behave differently, either like steroid or peptide hormones
Thyroid hormones behave like steroid hormones travel the bloodstream bound to a transport protein and cross the cell membrane to bind to an intracellular receptor, and signal changes in gene expression in the nucleus.
Adrenaline and noradrenaline, on the other hand, behave more like peptide hormones - they travel through blood unbound, and bind to cell surface receptors on cells, which then set off intracellular changes
What is the primary role of the hypothalamus in the endocrine system?
It is the link between the nervous and the endocrine system. It receives information from the entire body, and responds by producing hormones stored in the posterior pituitary, to be released later, or producing hormones that act on the anterior pituitary, making it secrete some hormones of its own.
What are the differences in the tissue types of the anterior and posterior lobes of the pituitary gland
The anterior lobe, is made up of glandular tissue
The posterior lobe, is made up of nervous tissue
What is the hypothalamo-hypophyseal-portal system?
This is a system of tiny capillaries that moves hormones quickly from the hypothalamus to the anterior pituitary
Are hypothalamic hormones stimulatory, inhibitory, or either?
Hypothalamic hormones can be stimulatory or inhibitory.
What are examples of hypothalamic stimulatory (releasing) hormones?
Thyrotropin releasing hormone, or TRH
Corticotropin releasing hormone, or CRH
Gonadotropin releasing hormone, or GnRH
Growth hormone releasing hormone, or GHRH
What hormone does the hypothalamic stimulatory (releasing) hormone thyrotropin releasing hormone (TRH) stimulate the production of? What does the released hormone do?
TRH leads to the production of thyroid stimulating hormone, or TSH, which reaches the thyroid and tells it to make some more thyroid hormones
What happens when plasma thyroid hormone levels increase?
A negative feedback signal is sent to the pituitary to make less TSH, keeping thyroid hormone levels in an optimal range
What hormone does the hypothalamic stimulatory (releasing) hormone corticotropin releasing hormone (CRH) stimulate the production of? What does the released hormone do?
CRH makes the pituitary produce adrenocorticotropic hormone - or ACTH - which goes to the adrenal glands and makes them secrete more of a hormone called cortisol
What happens when plasma cortisol levels increase?
High levels of cortisol inhibit the production of ACTH through a negative feedback mechanism
What hormone does the hypothalamic stimulatory (releasing) hormone growth hormone releasing hormone (GHRH) stimulate the production of? What does the released hormone do?
GHRH makes the anterior pituitary secrete more growth hormone - or GH - which has a direct effect on the long bones and other tissues in our body to stimulate growth.
What are the two hypothalamic inhibitory hormones?
Growth hormone inhibiting hormone (GHIH) also known as somatostatin, and prolactin inhibiting factor, which is also called dopamine
What hormones do the hypothalamic nuclei secrete to act on the posterior pituitary gland?
Antidiuretic hormone (ADH) also known as vasopressin and oxytocin.They travel down the axons in the pituitary stalk and reach the posterior lobe of the pituitary gland. The axons release ADH or oxytocin into the posterior pituitary capillaries, and from there, into the system circulation
What triggers the hypothalamus to release Antidiuretic hormone (ADH)?
High blood osmolarity or a low blood volume, ADH helps retain water from the urine and causes vasoconstriction of blood vessels, which helps decrease osmolarity and increase blood pressure
What hormone does the pineal gland release, what is its function?
Melatonin, it regulates our body’s circadian rhythm - or the “innerclock” that tells us when we should be sleeping and when we should be awake
What hormones are made by the thyroid gland?
T3 (triiodothyronine) & T4 (thyroxine)
What is the function of the T3 hormone?
Increases basal metabolic rate in the body
What is the function of the calcitonin and parathyroid hormone?
They are involved in calcium, phosphate, and bone metabolism
How are calcitonin and parathyroid hormone regulated?
By calcium levels in the blood
Where are the adrenal glands located?
Above each kidney
What is the outer layer of the adrenal gland called?
The cortex
What is the inner core of the adrenal gland called?
The medulla
What hormones are made by the cortex of the adrenal glands?
Steroid hormones- aldosterone, cortisol, and sex hormone precursors
What hormones are made by the medulla of the adrenal glands?
Epinephrine (AKA adrenaline) and norepinephrine (AKA noradrenaline)
What stimulates the secretion of aldosterone?
Low blood pressure or increased blood potassium
What is the function of aldosterone?
Prevent the loss of water and sodium in the urine and increases the elimination of potassium.
What stimulates the secretion of cortisol?
Stress, it is part of the sympathetic nervous system’s fight or flightresponse
What stimulates the secretion of epinephrine (AKA adrenaline) and norepinephrine (AKA noradrenaline)?
The sympathetic nervous system’s fight or flight response
What is the exocrine role of the pancreas?
To help with digestion
What is the endocrine role of the pancreas?
To secrete insulin and glucagon
What type of pancreatic cells secrete insulin?
Beta cells
What type of pancreatic cells secrete glucagon?
Alpha cells
What hormone is released in response to high blood sugar?
Insulin
What hormone is release in response to low blood sugar?
Glucagon
What is glycemia?
Blood sugar
What is the general function of insulin?
Insulin is a hormone that’s involved in lowering blood sugar levels or glycemia after a meal.
Where is insulin produced?
Islets of Langerhans in the pancreas
What is the primary exocrine role of the pancreas?
Secreting digestive enzymes into the small intestine to help digestion
What is the most abundant cell type found in the islets of Langerhans and what hormone do they secrete?
Beta cells are the most abundant, they produce insulin.
What hormone do the alpha cells of the islets of Langerhans secrete?
Glucagon
What is the most important trigger for insulin secretion?
Blood glucose. Beta cells are sensitive to glucose concentrations in blood, and when blood glucose levels rise, beta cells secrete insulin into the blood to help lower those levels and store glucose.
What are other stimulatory factors for insulin secretion?
Hormones like glucagon and cortisol, which stimulate insulin indirectly by increasing blood glucose levels
Increased fatty acid or amino acid concentrations in blood,since insulin is also involved in their storage.
Acetylcholine from the parasympathetic nervous system, which helps with digestion, and stimulates insulin secretion to decrease the recently absorbed glucose in blood.
What are inhibitory factors for insulin secretion?
Norepinephrine from the sympathetic nervous system, which is activated during stressful situations that demand high energy consumption and need glucose to be readily available in blood
Somatostatin, which avoids the excessive release of pancreatic hormones and growth hormone
Where are insulin receptors located?
Mainly in the liver but also in adipose tissue and skeletal muscles
Is insulin an anabolic or catabolic hormone?
Anabolic
What does insulin convert glucose to in the liver?
Glycogen
What does insulin convert glucose to in adipose tissue?
Fatty acids
What does insulin convert glucose to in skeletal muscle?
Amino acids
Does insulin stimulate or inhibit gluconeogenesis?
Insulin inhibits glucose production from lactic acid and noncarbohydrate molecules through gluconeogenesis.
What happens if glycogen storage capacity is reached and there is still excess glucose in the blood?
Insulin prompts the liver to convert glucose into fatty acids through glycolysis
What is glycolysis?
The metabolic pathway that converts glucose into pyruvate, and then pyruvate is converted to fatty acids through a reaction with acetyl-CoA
What do amino acid and glucose uptake in muscle cells help with?
Protein production and muscle growth. Insulin stimulates amino acid and glucose uptake into the muscle cells
What is the role of glucagon?
Increase glucose levels in the blood.
What is the general function of glucagon?
Increase blood glucose (glycemia)
Where is glucagon produced?
Islets of Langerhans in the pancreas
What hormone do the alpha cells of the islets of Langerhans secrete?
Glucagon
What hormone do the beta cells of the islets of Langerhans secrete?
Insulin
What is the most important trigger for glucagon secretion?
Alpha cells are sensitive to glucose concentrations in blood, and when blood glucose levels are low alpha cells secrete glucagon into the blood to help increase those levels
What are other stimulatory factors for glucagon secretion?
Glucagon secretion is also stimulated by adrenaline from the sympathetic nervous system, which is activated during stressful situations with high energy consumption
Glucagon secretion is also stimulated by cholecystokinin which is secreted by intestinal cells to stimulate digestion and absorption
What are inhibitory factors for glucagon secretion?
When blood glucose is high, alpha cells stop secreting glucagon, and beta cells start secreting insulin, which both lowers glucose levels and inhibits glucagon secretion in the process
Other molecules that inhibit glucagon production include somatostatin,which is classified as an inhibitory hormone that avoids the excessive release of pancreatic hormones
Where are glucagon receptors located?
Located in the membrane of its target cells- mainly in the liver, but also in fat or adipose tissue
Is glucagon an anabolic or catabolic hormone?
Catabolic
What is glycogenolysis?
The breakdown of glycogen stores into glucose in the liver
What is gluconeogenesis?
Glucose production from lactic acid and from noncarbohydrate molecules in the liver
From where does glucose get released to increase blood glucose levels?
Liver cells release glucose causing blood glucose levels to rise
What is lipolysis?
Breakdown of fat stimulated by glucagon through lipolysis in the liver and adipose tissue, causing a release of fatty acids into the bloodstream as an additional source of energy
What two hormones regulate glucose?
Glucagon and insulin
What is the function of adrenocorticotropic hormone (ACTH)?
It is a peptide hormone that helps regulate the release of hormones by the adrenal gland
Secretion of adrenocorticotropic hormone (ACTH) is dependent on what?
Hypothalamic-pituitary axis
What is the hypophyseal portal system?
A network of capillaries linking the hypothalamus to the anterior part of the pituitary gland
Where is corticotrophin releasing hormone (CRH) secreted and what is its function?
The hypothalamus secretes corticotropin releasing hormone (CRH) into the hypophyseal portal system to stimulate the release of adrenocorticotropic hormone (ACTH) from the anterior pituitary gland
How is ACTH normally released?
Normally, ACTH is released in a pulsatile manner throughout the day and peaks in the morning around 6am but it is also secreted in response to various forms of stressful stimuli
What are some examples of stressful stimuli that may stimulate the secretion of ACTH?
Hypoglycemia or during an infection in response to pro-inflammatory cytokines
What are the two parts of the adrenal glands and what hormone groups are each responsible for secreting?
Adrenal outer cortex- cortico steroids (aldosterone, cortisol, androgens)
Adrenal inner medulla- catecholamines (epinephrine andnorepinephrine)
What are the three zones of the adrenal cortex and what hormone is each responsible for secreting?
Outermost zone is the zona glomerulosa, secretes mineralocorticoids(aldosterone)
Middle zona fasciculata, secretes glucocorticoids (cortisol)
Innermost zona reticularis, secretes androgens (sex hormones)
What happens when ACTH binds to its receptor in the adrenal glands?
Adrenocortical cells release corticosteroid hormones, mainly glucocorticoids but also mineralocorticoids
What class of hormone are glucocorticoids and what is the most important glucocorticoid in humans?
Glucocorticoids are a class of steroid hormones, the most important glucocorticoid in humans is cortisol.
What is the function of cortisol?
Cortisol helps to regulate both the immune response as well as cellular metabolism
How does cortisol help to regulate the immune response?
It promotes an overall anti-inflammatory state, by inhibiting the two main products of inflammation
How does cortisol help to regulate cellular metabolism in adipose tissue?
In adipose tissue, cortisol triggers lipolysis, which is the breakdown of fats for energy, which can be used by other cells throughout the body
How does cortisol help to regulate cellular metabolism in the liver?
In the liver, it promotes gluconeogenesis, which is the production of new glucose molecules, and increased glycogen storage
How is cortisol involved in the regulation of blood glucose?
It increases insulin resistance in tissues, leading to an increase in blood glucose levels.
How does cortisol help to regulate cellular metabolism in the muscles?
In the muscles, cortisol stimulates proteolysis, which is the breakdown of proteins into amino acids, which then serve as substrates for gluconeogenesis
What type of feedback system do glucocorticoids use to control the release ACTH, what are the two primary methods?
Negative feedback system
First, glucocorticoids signal the hypothalamus to stop secreting corticotropin releasing hormone (CRH), which decreases anterior pituitary secretion of ACTH adrenocorticotropic hormone
Second, glucocorticoids signal directly into the anterior pituitary to stop the release of adrenocorticotropic hormone
What is another name for growth hormone?
Somatotropin
What is the general function of growth hormone?
It helps regulate the rate of growth in the body
What controls the secretion of growth hormone?
The hypothalamic-pituitary axis, the hypothalamus secretes growth hormone-releasing hormone (GHRH) into the hypophyseal portal system to stimulate the release of growth hormone by the anterior pituitary gland.
What is the hypophyseal portal system?
A network of capillaries linking the hypothalamus to the anterior pituitary gland
How is growth hormone normally released?
Normally, growth hormone releasing hormone (GHRH) is released in a pulsatile manner, throughout the day and peaks one hour after you fall asleep, but it is also secreted in response to various forms of internal and external stimuli.
What are some examples of stimuli that may stimulate the secretion of growth hormone?
Hypoglycemia causes the hypothalamus to secrete growth hormone releasing hormone (GHRH)
Exercise causes the adrenal glands to secrete epinephrine and that stimulates the hypothalamus to secrete growth hormone releasing hormone (GHRH)
In puberty, increased levels of estrogen and testosterone stimulate the hypothalamus to release growth hormone releasing hormone (GHRH), which is responsible for the growth spurt
What type of feedback system control the release of growth hormone? What are the three primary methods?
Negative feedback system
First, increased levels of growth-hormone-releasing hormone (GHRH) in the blood signals the hypothalamus to stop making more
Second, when growth hormone reaches tissues like the liver, muscles, and bones, they make somatomedins, which are hormones that signal the anterior pituitary to stop producing growth hormone.
Third, growth hormone and somatomedins together signal to the hypothalamus to produce somatostatin, which is also called the growth hormone inhibiting hormone (GHIH)
What is the function of somatostatin in the pituitary gland?
In the pituitary, it blocks growth hormone releasing hormone (GHRH) from acting on the somatotroph cells, so that secretion of growth hormone is inhibited.
What are direct effects of growth hormone?
Stimulation of cellular metabolism which leads to tissue growth through lipolysis in adipose tissue and in the liver through gluconeogenesis and glycogenolysis. It also increases insulin resistance in tissues.
What are indirect effects of growth hormone?
Growth hormone stimulates the steady release of insulin-like growth factor 1 (IGF-1) which promotes cellular metabolism, prevents cell death, and increase the rate of cell division and differentiation throughout the body
In the muscles, it stimulates amino acid uptake into the muscle cells, which helps with protein production and muscle growth. It’s also the key hormone that stimulates the growth in length of long bones
What are the thyroid hormones called?
T3- Triiodothyronine
T4- Thyroxine (AKA tetraiodothyronine)
What is the general function of the thyroid hormones?
To help regulate the body’s metabolism.
Where are T3 and T4 produced?
The thyroid gland
What controls secretion and production of T3 and T4?
Production and secretion of thyroid hormones is under control ofthe hypothalamus-pituitary axis.
How does the hypothalamus-pituitary axis control secretion and production of T3 and T4?
The hypothalamus secretes thyrotropin releasing hormone (TRH) into the hypophyseal portal system
In the anterior pituitary, TRH binds to a surface protein on a group of pituitary cells and stimulates them to release thyroid stimulating hormone (TSH) into the bloodstream
TSH then travels to the thyroid gland and binds to the TSH receptors located in the membrane of the cells of the thyroid gland which promotes every aspect of T3 and T4 production.
What happens to T4 once it enters systemic cells?
It is mostly converted to T3.
How do T3 and T4 help with environmental adaptation?
Thyroid hormones help to speed up the basal metabolic rate. Exposure to cold weather stimulates the release of T3 and T4, and they increase body metabolism and heat production by burning up more energy in the form of sugars and fats
How are T3 and T4 involved with the autonomic nervous system?
Thyroid hormones help activate the sympathetic nervous system, which is responsible for the fight or flight response. This increases cardiac output, respiratory rate, and mental alertness
How are T3 and T4 involved with the development?
Thyroid hormones work synergistically with growth hormone to promote long bone growth and are necessary for normal brain development.
What type of feedback system do thyroid hormones use to control the release of T3 and T4? What is this process?
Negative feedback system
High levels of thyroid hormones tell the hypothalamus and anterior pituitary gland to stop their secretion of TRH and TSH, respectively, lowering thyroid hormone production and secretion from the thyroid gland.
Low levels of thyroid hormones tell the hypothalamus and anterior pituitary gland to increase their secretion of TRH and TSH, respectively. More TRH increases TSH production in the pituitary and the thyroid gland gets more stimulation to produce and secrete thyroid hormones.
Which 3 hormones are responsible for keeping blood calcium levels stable?
Parathyroid hormone (PTH), vitamin D, and calcitonin
Of the 3 hormones involved in blood calcium levels, which is primarily responsible for keeping blood calcium levels stable?
Parathyroid hormone (PTH)
Does parathyroid hormone (PTH) increase or decrease blood calcium levels?
Increase
Does vitamin D increase or decrease blood calcium levels?
Increase
Does calcitonin increase or decrease blood calcium levels?
Decrease
What cellular processes is free-ionized diffusible calcium involved with?
Neuronal action potentials, contraction of skeletal, smooth, and cardiac muscle, hormone secretion, and blood coagulation
Where are the parathyroid glands located?
Parathyroid glands are 4 pea sized glands buried within the posterior part of the thyroid gland
What are the three ways the parathyroid hormone increases extracellular calcium?
By stimulating bone resorption, causing phosphaturia and renalcalcium reabsorption, and calcium absorption in the digestive tract.
How does parathyroid hormone increase extracellular calcium through bone resorption?
In the bones, PTH binds to receptors on osteoblasts, which are the bone building cells, and gets them to release cytokines that form osteoclasts that breakdown bone, and the two minerals that make up bone - calcium and phosphate, -are released into the blood
How does parathyroid hormone increase extracellular calcium through phosphaturia and renal calcium reabsorption?
Parathyroid hormone binds to principal cells of the distal convoluted tubules and causes tubular cells to increase reabsorption of calcium from urine
How does parathyroid hormone increase extracellular calcium through calcium absorption in the digestive tract?
Parathyroid hormone helps the body convert the precursor of vitaminD, into its active form, vitamin D. Active vitamin D then goes on to the gastrointestinal tract where increases the activities of the calcium channels on the cell membrane, allowing them to absorb more calcium from food
What is thermoregulation?
How an organism keeps its body temperature within certain limits. It is needed in response to internal and external temperature variations.
What is the normal body temperature for humans?
Between 36.1- 37°C or 97-98.6°F
What is hyperthermia?
When body temperature increases above 38.5° C, or 101.3°F
What is hypothermia?
When body temperature decreases below 35 °C, or 95 °F
What structures sense and respond to internal temperature variations?
Thermoreceptors located in the anterior hypothalamus
What structures sense environmental temperature variations?
Changes in the external temperature are sensed by the skin thermoreceptors, which are specialized nerve cells located in the skin
What structure responds to increased environmental temperatures?
The anterior hypothalamus responds to increased environmental temperatures and it also controls the core temperature of the body
What structure responds to decreased environmental temperatures?
The posterior hypothalamus responds to decreased environmental temperatures
What are the three physiologic mechanisms through which heat production is increased?
Stimulation of thyroid hormones, activation of the sympathetic nervous system, and shivering
How does the stimulation of thyroid hormones increase heat production?
Thyroid hormone (T3 or T4) action is stimulated, one of their roles is toincrease heat production by stimulating conversion of T4 to T3. T3 thenincreases the production of the energy molecule adenosinetriphosphate or ATP which can be used to generate heat
How does the activation of the sympathetic nervous system increase heat production?
The sympathetic nervous system is normally activated by fight-or-flight situations, and it leads to increased catecholamine production (epinephrine or norepinephrine) which can burn calories, generate heat, and cause vasoconstriction decreasing blood flow to the surface of the skin, reducing heat loss.
How does shivering increase heat production?
When we shiver and these muscles contract, ATP breaks into adenosine diphosphate or ADP causing an exothermic reaction. With more energy released, more heat is generated.
What are physiologic mechanisms to increase heat loss when environmental temperatures are too high?
When the skin thermoreceptors sense that the body heat has become too high, they send signals to the anterior hypothalamus to activate the heat-dissipating mechanisms which include sweating and decreasing sympathetic nervous system activity
How does sweating increase heat loss?
The anterior hypothalamus increases the activity of thermoregulatory sweat glands leading to increased sweating.The sweat glands spew out perspiration which then evaporates from the skin. Evaporation is a heat-losing mechanism through which a liquid changes to a gaseous state due to an increase in temperature
How does decreasing the sympathetic nervous system activity increase heat loss?
The anterior hypothalamus decreases the activity of the sympathetic nervous system in skin blood vessels which means the arterioles dilate and the blood flow increases. More blood flow leads to more warm blood from the body core taken to the body surface, from where heat is lost by radiation, conduction, or convection
What typically causes fever?
Fever most frequently occurs in response to infections.
How do pyrogens contribute to fever?
During an infection, the microbes produce pyrogens, which are molecules that increase the production of interleukin-1 which signals the anterior hypothalamus to increase local prostaglandin production, which are lipid molecules that increase the set point temperature above 37 degrees Celsius
The new set point will make the normal core temperature appear too low and so the anterior hypothalamus activates heat-generating mechanisms, such as shivering, to increase body temperature up to the value of the new set point
What is the function of the kidneys?
Blood filtration, regulation of blood pH, volume, osmolarity and hormone production
What are the two main parts of the kidney?
Renal medulla and renal cortex
Where in the kidney does the urine collect before exiting the kidney through the ureter?
Renal pelvis
Approximately how many times does the body’s entire blood volume get filtered every day?
About 30 times a day, which is more than once every hour.
Approximately what percent of the total cardiac output is sent to the kidneys?
25%
Where does blood filtration start in the kidneys?
The glomerulus, a tiny bundle of capillaries
Where does the blood go after being filtered in the glomerulus?
It is sent through efferent arterioles to peritubular capillaries then sent to the venous system through the kidneys then out the renal veins into the vena cava
What type of arterioles allow blood to enter glomerular capillaries?
Afferent arterioles
What type of arterioles allow blood to leave glomerular capillaries?
Efferent arterioles
What is the functional unit of the kidney?
The nephron
Approximately how many nephrons are found in the kidneys?
Within each kidney, there are about 1 million nephrons
What do nephrons produce?
Urine
What are the two major structures of the nephron?
The renal corpuscle and the renal tubule
What are the two major structures of the renal corpuscle?
The glomerulus and the Bowman’s capsule (AKA glomerular capsule)
What is the function of the renal corpuscle?
It is where blood filtration starts, in the capillaries of the glomerulus which is encased by Bowman’s capsule
After the fluid is filtered from the blood in the glomerular capillaries where does it go and what is it called?
It is called filtrate and it flows into Bowman’s capsule and then into the proximal tubule
What do filtration slits in the epithelial lining of the nephron allow to pass through and what does it block?
They allow small particles such as water, glucose, and ionic salts to pass through and block large proteins and red blood cells
What structure surrounds the renal tubule?
The peritubular capillaries
What are the major parts of the renal tubule?
The proximal convoluted tubule, the loop of Henle (AKA nephron loop),the distal convoluted tubule, and the collecting duct
Where does fine-tuning of the filtrate happen based on the body’s needs?
In the lumen of the renal tubule in the nephron
What is the function of the juxtaglomerular complex and where is it located?
It is involved in the regulation of blood pressure and the glomerular filtration rate located in between the distal convoluted tubule and the afferent arteriole in the nephron.
What is the glomerular filtration rate?
The amount of blood that passes through the glomeruli each minute
What are the three types of cells in the juxtaglomerular complex?
Macula densa cells, juxtaglomerular cells, and extraglomerular mesangial cells
Where are macula densa cells of the juxtaglomerular complex located and what is their function?
Macula densa cells are in the distal convoluted tubule and they can sense when levels of sodium and chloride are low.
Where are juxtaglomerular cells of the juxtaglomerular complex located and what is their function?
Juxtaglomerular cells are in the wall of the afferent arteriole, they receive signals from the macula densa cells regarding the sodium and chloride levels. They can also independently sense the low pressure in the blood vessels and secrete an enzyme called renin which increases sodium reabsorption which helps raise the blood volume
What is the function of the extraglomerular mesangial cells of the juxtaglomerular complex?
The extraglomerular mesangial cells help with the signaling between macula densa cells and juxtaglomerular cells
What are the major functions of renin?
Increase sodium reabsorption which helps increase blood volume and constriction of blood vessels which helps raise blood pressure
What is the path of urine flow after it is produced by the nephrons?
Minor calyces–> major calyces–> renal pelvis–> ureter–> bladder–>urethra
What controls the internal urethral sphincter?
The autonomic nervous system (involuntary control)
What type of muscle is the detrusor muscle of the bladder?
Smooth
What controls the external urethral sphincter?
Skeletal muscle (voluntary control)
How is urination controlled?
The micturition reflex
How does the micturition reflex control urination?
It causes contraction of the detrusor muscle of the bladder and relaxation of the internal and external sphincter when the bladder is about half full.
The pontine storage center in the pons stops the micturition reflex until an appropriate time to urinate, then the pontine micturition center allows the micturition reflex to happen.
What is the function of antidiuretic hormone (ADH)?
ADH prevents excessive urine production
What is the chemical structure of ADH?
It is a peptide hormone
What is another name for ADH?
Vasopressin
What is the effect of ADH (AKA vasopressin) on blood vessels?
ADH causes vasoconstriction
What is the effect of ADH on blood pressure and how does it cause this effect?
ADH prevents making excessive urine, leading to water retention, and it causes vasoconstriction. Together these two actions help increase blood pressure
Where is ADH produced and how does it enter the bloodstream?
ADH is produced in the hypothalamus and travels down the pituitary stalk to the posterior pituitary gland where it is released into the bloodstream through capillaries in the posterior pituitary
What happens to plasma osmolarity when the body is dehydrated?
Osmolarity increases because the fluid levels in your blood drop, but the total number of solute particles remains roughly the same
Where are osmoreceptors that sense changes in osmolarity located and how do they sense changes in osmolarity?
Anterior hypothalamus through neurons sampling the blood through aquaporins, When the blood osmolarity is high, water moves out of these cells into the blood by osmosis, causing the neurons to shrink
What happens when blood osmolarity is high?
Neurons in the anterior hypothalamus fire action potentials that signals the hypothalamus to trigger the thirst response and trigger the hypothalamus to produce more ADH which is then released into the blood
What happens to ADH once it enters the bloodstream?
It travels to the kidneys and act on receptors in cells of the distal convoluted tubule and collecting ducts of the nephrons which act on aquaporins in the tubule to allow water to travel out of the lumen of the tubule and into the cells lining the nephron, and ultimately back into the blood. This dilutes the blood and returns plasma osmolarity to a normal level.
How is the production of ADH stopped once plasma osmolarity is at a normal level?
Once the plasma osmolarity returns to normal, water from the blood enters the osmoreceptors in the anterior hypothalamus via osmosis, causing them to swell which stops them from signaling the hypothalamus to produce ADH
Where is excessively low blood pressure detected and what happens when this is detected?
Baroreceptors near the carotid artery and the arch of the aorta detect low BP and signal the hypothalamus to increase ADH secretion.
Baroreceptors in the juxtaglomerular cells in the afferent artery of the kidneys also detect low BP and signal the kidneys to secrete the enzyme renin which through a cascade involving angiotensinogen, angiotensin I and angiotensin II stimulates the hypothalamus to make more ADH.
How does ADH cause blood pressure to increase?
First, ADH increases the number of aquaporins in the distal tubule and collecting duct which reabsorbs water from the urine and replenishes the plasma volume.
Second, ADH acts on smooth muscle cells in the arteries causing vasoconstriction which increases peripheral vascular resistance and blood pressure
How is the production of ADH stopped once blood pressure is increased?
Baroreceptors pick up on the increased blood pressure and send an inhibitory signal to the hypothalamus and that makes ADH secretion stop
What is the function of juxtaglomerular cells?
To identify if blood pressure or blood volume needs to rise.
What are three ways juxtaglomerular cells are signaled that blood pressure or blood volume needs to rise?
Through mechanoreceptors (baroreceptors) in the juxtaglomerular cells, through sympathetic nervous system activation from mechanoreceptors in the aortic arch and carotid sinus, and from macula densa cells in the distal convoluted tubule
What do the juxtaglomerular cells do if they feel low blood pressure through their mechanoreceptors?
When they are stretched by an increased blood pressure, they will inhibit renin release.
When they are collapsed from low blood pressure, they will stimulate renin release.
How does the sympathetic nervous system respond to signals from mechanoreceptors in the aortic arch and carotid sinus regarding blood pressure?
If they are stretched due to high blood pressure then the sympathetic nervous system will be down regulated, if they collapse secondary to low blood pressure then the sympathetic nervous system is activated and stimulate juxtaglomerular cells to stimulate renin
How do the macula densa cells sense the need to increase blood pressure?
Macula densa cells are chemoreceptors in the wall of the distal convoluted tubule that can sense when glomerular filtration rate increases or decreases based on the quantity of sodium and chloride ions flowing through the tubule.
When blood pressure rises, renal blood flow and glomerular filtration rate increases so more fluid and more dissolved sodium and chloride ions reach the macula densa.
When there’s decreased fluid and sodium and chloride ions getting to the macula densa cells, then that sends a signal to the juxtaglomerular cells in the afferent arteriole to secrete renin.
What is the RAAS?
Renin-Angiotensin- Aldosterone System, this is a system that works to increase blood pressure
How does the RAAS work?
Kidneys secrete renin that converts angiotensinogen to angiotensin I, and then angiotensin converting enzyme converts angiotensin I to angiotensin II.
Angiotensin II causes the efferent arteriole to constrict more than the afferent arteriole, which increases the glomerular filtration rate, it also causes the proximal tubule to reabsorb more sodium ions from the filtrate, increases thirst, and helps increase blood pressure, while it, also, stimulates the adrenal cortex to release aldosterone, which gets the kidneys to retain sodium and water.
What is the effect of angiotensin II on the hypothalamus?
It stimulates thirst and increases the production of antidiuretic hormone (ADH)
What is the impact of increased lactic acid in the bloodstream?
It can lower pH levels in the bloodstream
What structures detect increased lactic acid in the bloodstream?
Peripheral chemoreceptors, which are specialized neurons located in the walls of the carotid arteries and the aortic arch
What do peripheral chemoreceptors do when they detect decreased blood pH?
These neurons fire more impulses, notifying the respiratory centers in the brainstem that they have to increase the respiratory rate and depth of breathing, called hyperventilation
What is the effect of exercise-induced hyperventilation?
More oxygen reaches the alveoli, which are the tiny air sacs where gas exchange occurs
What is the effect of more oxygen in the alveoli due to exercise-induced hyperventilation?
It leads to pulmonary vasodilation, reducing the pulmonary vascular resistance, so more blood flows through. We get a more even distribution of pulmonary perfusion, and increased efficiency in gas exchange between the alveoli and the pulmonary capillaries, so more oxygen gets in the blood, and more carbon dioxide leaves the blood
What happens in the cardiac centers in the brainstem when peripheral chemoreceptors firing increases?
The cardiac centers in the brainstem decrease the parasympathetic stimulation to the heart and increase sympathetic stimulation - aka the fight or flight response.
What happens to heart rate and cardiac contractility with increased sympathetic stimulation?
When epinephrine gets to the heart, it binds to the adrenergic receptors of the heart muscle, making heart rate and contractility increase. The heart muscle fibers contract faster and stronger and the amount of blood the heart pumps out in a minute increases.
What happens to the blood vessels to the kidneys, liver, and gastrointestinal system with increased sympathetic stimulation?
Epinephrine causes systemic vasoconstriction, which means visceral blood vessels contract, so there’s reduced blood flow to the kidneys, liver, and the gastrointestinal system.
What happens to PaO2 and PaCO2 in arterial and venous blood during exercise?
Mean arterial oxygen, and mean carbon dioxide partial pressures, or PaO2 and PaCO2 for short, stay constant. In venous blood, however, oxygen partial pressure is low, but carbon dioxide partial pressure is high during exercise compared to rest
What happens to blood sugar levels with extended exercise?
Blood sugar levels decrease
What hormone does the pancreas release in response to low blood sugar?
In response to low blood sugar, the pancreas releases glucagon.
What is glycogenolysis?
Breakdown of stored glycogen in the liver into glucose, stimulated by glucagon and breakdown of stored glycogen in the muscle cells into glucose, stimulated by epinephrine.
What is lipolysis?
The breakdown of lipids into free fatty acids in adipose tissue stimulated by glucagon and epinephrine
