Exam 4 LO Flashcards
Major roles of saliva
Starch breakdown
Food solubilization
Protection
Absorption
Lubrication
Major digestive enzyme present in the saliva, responsible for starch breakdown
alpha amylase
Alpha amylase’s ability to function depends on…
how well food is chewed
Starch breakdown is important in the mouth because…
amylase is deactivated in the stomach due to acidic environment
Breaking down food releases chemicals that activate…
taste receptors in mouth, if something doesn’t get broken down then you cannot taste it as well
In food solubilization, dissolved chemicals diffuse into…
pores in tongue, sensed by taste hairs that depolarize the membrane—activating NS
Protects against chewing of sharp material
Mucins producing thick mucus
pH of saliva and it’s role
Alkaline pH buffers against acidic foods and stomach acid
Absorption of what molecules can occur directly in the mouth? What happens when molecules are absorbed directly in the mouth?
Low molecular weight. they bypass (bypass hepatic portal vein) the first round of liver metabolism and go straight into the bloodstream
What do mucins produce and how it is relevant for lubrication?
glycoproteins that coat the food so you can move it around and important for swallowing
Swallowing is what kind of reflex
Long reflex
Explain the voluntary phase of swallowing
Tongue pushes food bolus back and upward’s towards the back of the mouth, once food touches the soft palate and back of mouth which triggers swallowing reflex
Explain the pharyngeal phase of swallowing
Medulla initiates swallowing reflex, causing soft palate to elevate, closing the glottis and opening the esophageal sphincter (once food moves into esophagus and sphincter closes, glottis opens and breathing continues)
Explain reflex arc of swallowing
Controlled variable:
Stimulus:
Sensor:
Input:
Controlled center:
Output:
Effectors:
Response:
Negative feedback:
Controlled variable: open and clear back of mouth
Stimulus: food touching palate
Sensor: mechanoreceptor
Input: afferent neuron
Controlled center: medulla
Output: somatic motor neuron
Effectors: skeletal muscle
Response: contract,elevate soft palate; larynx closes and epiglottis moves down; opening of UES (relaxation)
Negative feedback: moves bolus to clear back of mouth
What occurs in the esophageal phase
food moves down esophogus by peristalsis
As food moves into the stomach, the LES…
relaxes and opens allowing food to enter into stomach
If food gets stuck what occurs?
Short reflexes will continue peristalsis
Distinguish between the walls of the esophagus and those represented by small intestine
GI tract has smooth muscle
Upper 3rd of esophogus has skeletal muscle
Lower 2/3rds of esophogus has smooth muscle
Stretch of smooth muscle responds by contraction in ENS
myogenic reflex
Explain what happens at the cellular level with stretching of smooth muscle
stretch activates mechanically gated channels, allowing calcium to enter the cell
Higher calcium concentration where?
Outside the cell
Explain what happens at the subcellular level with stretching of smooth muscle
- calcium in cell binds to calmodulin forming the ca-calmodulin complex
- Ca-calmodulin complex activates MLCK
- Active MLCK binds to and phosphorylates myosin
- Myosin binds to actin, initiating contraction
If MLCK is elevated what occurs:
If you inhibit phosphorylation of myosin:
more likely to be contracted
Predict it will lead to muscle relaxation
Explain the reflex arc in esophogus that responds to stretch
Controlled variable:
Stimulus:
Sensor:
Input:
Controlled center:
Output:
Effectors:
Response:
Negative feedback:
Controlled variable: Muscle length
Stimulus: Stretch
Sensor: Mechanoreceptor (sensitive to stretch)
Input: Sensory neuron
Controlled center: ENS (interneuron)
Output:Myenteric plexus (innervate smooth muscle)
Effectors: Smooth muscle (contracts in response to ENS input)
Response: Contraction
Negative feedback: Moves bolus and restores muscle length
Describe how the closing of the LES is aided by positive pressure abdominal pressure
LES located outside thoracic cavity because it experiences normal atm pressure which helps keep the LES closed, forming a barrier between acid and esophogus
What is Gatroesophogeal reflux disease (GERD)? Who is at risk?
High pressure in stomach
At risk: Obsese people, pregnant women, anyone who has overeaten
What is the role of longitudinal muscle? Circular? in the muscularis externia
Long= propels food in one direction
Circular= wraps around the intestine and closes off the lumen in contraction
What occurs in the mucosa?
90% absorption
What innervates the GI tract?
Submucosa
Role of the submucosa
Enzyme secretion of glands, filled with BV and glands
The inner most layer, facing the inside of the stomach
Gastric mucosa
The gastric mucosa is able to secrete…? What does it contain
Mucus and bicarb; G cells, delta cells, and parietal cells
Characteristics of mucus secretion
80% carb chains, alkaline, high in bicarb
Only substance secreted by the stomach that’s essential to life
Intrinsic factor
Large glycoprotein that complexes with vitamin B12
Intrinsic factor
When is vitamin B12 absorbed?
When complexed with intrinsic factor (in intenstine)
Explain how acidic environment helps with iron absorption?
Iron absorbed as ferrous iron (Fe2+); acidic environment helps prepare the iron absorption in intestine
People taking anti-acids or a proton pump inhibitor can suffer from…
- Iron mal-absorption (If ferrous iron is oxidized)
- Bacterial infections (less acidic enviornment to kill bacteria)
- Decreased activation of pepsinogen and protein digestion (pepsin cannot be formed)
Function of mucus
lubricates food, protects against acidic stomach
Play a critical role in maintaining mucosal integrity, HCO3- secretion, and mucus production
Prostagladins
What is the effect of drugs that inhibit prostaglandins?
Drugs: NSAIDS, ibuprofen; ulcers
Intrinsic factor secreted from partietal cells stimulated by…
ACh, gastrin, and histamine with vitamin b12 to permit absorption
Explain the long reflex (extrinsic)
Chemo/Mechanoreceptor–> sensory neuron–> medulla–> vagus nerve–>smooth muscle cell/gland–> muscle contraction or secretion
What is typically secreted for the long reflex mechanism of acid secretion
Acetylcholine release from submucosal plexus and PSNS that binds parietal cell
What is typically secreted for the Short reflex mechanism of acid secretion
Acetylcholine release from submucosal plexus and PSNS that binds parietal cell
Explain the short reflex (intrinsic)
Chemo/Mechanoreceptor–> sensory neuron–>interneuron–> myenteric/submucosal plexus (ENS)–>smooth muscle cell/gland–> muscle contraction or secretion
What is typically secreted for the paracrine mechanism of acid secretion
histamine is released from H cells that bind receptors present in neighboring parietal cells
What is typically secreted for the endocrine mechanism of acid secretion
G cells in mucosa secrete gastrin into blood that binds to receptors on the parietal cell and histamine cell (allowing for histamine release)
One cell releases a hormone that affects a neighboring cell (close target), acts on a nearby cell that expresses the hormone’s receptor
Paracrine
Hormone released into the blood and effects cells expressing the hormone’s receptor (too far for diffusion)
Endocrine
Outputs for Long and short reflex
Long- parasym NS
Short- ENS
what is the mechanism for acid secretion in the lumen of stomach
- Co2 from blood is converted into H+ and HCO3- (by CA)
- H+ is pumped against its gradient by proton pump into the lumen of stomach
- HCO3- moves into the blood through Cl- exchanger, making blood that moves through stomach more basic (alkaline tide)
What is the proton pump
Moves H out and K in through primary transport
Lowering the hydrogen ion concentration results in…
CO2 diffusion into the cell
What is the inhibitor of acid secretion and explain how it inhibits?
Somatostatin released by delta cells if high H+ in lumen; acts directly on pariteal cell
If someone is over-produicing gastrin what can you expect to happen?
increased HCl levels and increased histamine release
An inactive enzyme synthesized and stored intracellularly. Give an example.
Zymogen, pepsinogen
Zymogen is released by __ and to be activated….
chief cells, requires acid presence
Explain pepsin’s activation, regulation, and function.
Activation= pepsinogen activated by HCl in stomach lumen (HCl cleaves pepsinogen into pepsin)
Regulation= by acid secretion in stomach lumen
Function= enzyme responsible for cleaving proteins and peptides in stomach, responsible for 20% protein digestion
Describe how the gastric muscularis promotes mechanical breakup of chyme through peristalsis
3 muscle layers: oblique, circular, and longitidudinal
Peristalsis allows mixing and moving of chyme (1 way movement)
Explain the Basal electrical rhythm (BER)
Pacemaker cells in stomach generate a spontaneous, rhythmic depolarization—resulting in contraction of the long. muscle
Describe the intrinsic BER
Myogenic and submucosal plexus, short reflexes
Describe the extrinsic stimulators of motility in the stomach. Shift? What’s released?
- Parasym. NS= increased activation shifts the resting MP toward threshold (increases # of AP)
- Sym NS= increased activation shifts the resting MP away from threshold (decreasing # of AP)
Parasym NS releases ACH on pacemaker cells
Sym NS releases norepi (inhibitory) on pacemaker cells
Describe the interaction of excitatory and inhibitory stimuli in regulation of gastric emptying
Increased PSNS would increase gastric emptying, decreased PSNS would decrease emptying
Increased sym output would lead to less/decreased gastric emptying
When food enters the stomach, what happens to the pH?
When there’s gastric emptying, what happens to the pH?
increases, excitatory
decreases, inhibits acid
The myenteric plexus receives its messages from the
vagus nerve
Produces peristaltic waves
submucosa plexus
Describe the effects of sympathetic and parasympathetic stimulation on the intrinsic activity of the gut….
Sympathetic= release NE on smooth muscle and pacemaker cells, inhibits digestive activity (decrease AP)
Parasympathetic= release ACh on smooth muscle and pacemaker cells, stimulates digestive activity (Increase AP)
Biggest contributor to parasympathetics stimulation of GI tract/gut is….
Vagus nerve
The ENS serves as the control center for…
local short reflexes
The ENS respond to what kind of input from the SNS and PSNS
Extrinsic
Stretching activates sensory neurons that increase motility through the…
activation of the ENS (stretch increases Ca2+ permeability)
What are the effects of stretch on the smooth muscle GI tissue (from lab)
opens the mechanically gated Ca2+ channels, causing Ca2+ to flow into the cell allowing for contraction
What are the effects of Ach on the smooth muscle GI tissue (from lab)
As Ach binds to the receptor, it will increase the rate of pacemaker firing and calcium into the cell—increasing contraction/strength of contraction
What are the effects of atropine on the smooth muscle GI tissue (from lab)
blocks Ach from binding to and activating the GPCR, relaxing the smooth muscle (no contraction)
What are the effects of epi/norepi on the smooth muscle GI tissue (from lab)
As epi binds to the receptor, it inhibits Ca2+ release from the SR and decreases the rate of pacemaker firing–leading to muscle relaxation
Epi/norepi hyper-polarizes the membrane
What are the effects of elevated extracellular K+ on the smooth muscle GI tissue (from lab)
cell depolarizes to threshold which promotes pacemaker cells to generate AP’s quicker and increases intracellular Ca2+—-muscle contraction
If you elevate the extracellular K+ on the smooth muscle GI tissue, what happens to the gradient
increases the gradient (Increase ECF K+ depolarizes the cell by preventing K+ from exiting)
What are the effects of BaCl–K+ inhibitor on the smooth muscle GI tissue (from lab)
BaCl causes our muscles to produce less/weaker contractions because re-polarization inhibits pacemaker cells from reaching threshold as often (intracellular Ca2+ decreases)
Describe the contraction in the intestine (peristaltic waves)
A slow wave must reach threshold
1. The depolarization from the AP spreads through the
intestine (gap junctions) depolarizing smooth muscle
cells.
2. Depolarization is sensed by voltage gated Ca2+
channels causing them to open.
3. Ca2+ enters the smooth muscle cells and initiates
muscle contraction.
Distension of the stomach ___ force of contractions and rate of emptying
increases
Presence of fat, acid, and amino acids in the intestine ___ gastric motility
inhibits
Waves of contraction become stronger as it moves towards the __. What occurs here? What else is affected?
antrum; most of mixing, pyloric sphincter starts relaxing (and open)
Somatostatin inhibits acid secretion and ____
Somatostatin is released in response to what?
release of CCK and secretin from enteroendocrine cell
Increased H levels, CCK, and secretin
Effects of secretin, CCK, and enteroendocrine cells on gastric emptying/motility
inhibit gastric emptying/motility
Force and duration of muscle contractions are directly related to…
frequency of AP’s
As a peristaltic wave moves toward the antrum, what happens to the pyloric sphincter?
Opens and then shuts allowing small amount of chyme to be released from stomach into SI
Where are precursor cells located
Crypts of L
Replace the dying epithelium by dividing and pushing cells upward to repolarize the villi tip from hypoxic environment
Precursor cells
90% of villi cells are
absorptive cells
Abundant in the first part of the intestine when we have a high level of acid coming from chyme in the stomach
Goblet cells
Entereoendocrine cells are located
villi
Describe the countercurrrent mechanism of villi
Tip of the villi becomes hypoxic because the oxygen is high as it enters the villi, diffuses down gradient into the venous blood (arterial and venous blood mixed) :cells then die
Highest turnover rate of cells is in the
SI
Relationship between precursor cells and chemotherapy/radiation
Chemo targets= fast dividing cells such as precursor cells
Role of circular folds in the SI
maximize absorption by increasing SA and increase surface diffusion
Why is it important to neutralize chyme
Enzyme function
Mucosal protection
Micelle formation
Secretin is released by ___ in response to ___
enteroendocrine cells, increased H+
Explain the mechanism of secretin acting on the pancreas and SI
- As CO2 diffuses into a ductal cell in pancreas, HCO3 and H+ is formed by CA
- HCO3- is pumped down gradient though HCO3/Cl- exchanger (secondary transport) into lumen of SI from pancreas
- HCO3- helps neutralize gastric acid
Secretin goes to the __, activates ___ to release ___ from _____ to _____
pancreas, ductal cells, bicarb, pancreatic duct to SI
Secretin in the blood has what effect on gastric motility
CCK in the blood has what effect on gastric motility
Gastrin has what effect on gastric motility
Inhibits
Inhibits
Stimulates
If enteroendocrine cells cannot secrete secretin (if there’s a mutation for example) what effect does this have?
no bicarb production and cannot neutralize pH in intestine
If there’s a plug in the pancreatic duct or an obstruction in duct, what effect does this have?
Bicarb cannot move into the SI (low pH in SI) but secretin is still being secreted
Hormone released from mucosal cells in response to fasting
Motilin
Motilin stimulates the Migrating Motor Complex that….
increases intestinal peristalsis (long peristalic wave from stomach to LI)
CCK is released from ____ when in the presence of ___
enteroendocrine cells; fats, peptides, and carbs
Signals the release of digestive enzymes from the pancreas and bile from liver into SI
CCK
Describe CCK secretion
- When an increase in lipase, CCK secreted from enteroendocrine cells into the blood
- From the blood CCK….
- Targets pancreas to release digestive enzymes to digest lipids that go to the lumen of SI
- Targets gall bladder to secrete bile to emulsify fat in prep for absorption
What cell releases digestive enzymes and zymogens in the pancreas
Acinar cells
Breaks up fat allowing digestive enzymes to digest and breakup fats and amino acids
Bile
Potent stimulator for acid secretion
Gastrin
Gastrin is secreted from the ___
Antrum by G cells
How does gastrin work to stimulate gastric motility
Gastrin binds to receptors on the parietal cells (for acid release) and histamine cells
What controls the movement of peristalsis and segmentation
ENS: Intrinsic
Serve as a control for short reflexes
Interneurons in the ENS
Stretch activates mechanoreceptors on sensory nerves that ____ motility by activating the ____
increase, myenteric plexus
Acid in the SI activates ___ on the sensory nerves that increase ____ by activating the ___
chemoreceptors, bicarb secretion, submucosal plexus
What controls the forward movement and mechanical breakup of the chyme
Long reflex (ANS)
Explain how the ANS/neural (long reflex) effects gastric motility (digestive activity)
Parasym (vagus) NS= cholinergic fibers (Ach) stimulates digestive activity
Sympathetic= NE inhibits digestive activity
Pancreas has an exocrine function because
it releases secretin and CCK into pancreatic DUCT
Describe protein digestion
- Digestive enzymes from acinar cells enter into the small intestine (as zymogens) from pancreatic duct
- Trypsinogen is activated by brush border enzymes on microvilli (convert into trypsin)
- Trypsin activates other inactive enzymes to break down proteins
Protein is broken down into…
Smaller peptides then single AA
Describe carbohydrate digestion
Glucose polymers to disaccharides to monosaccharides (broken down by amylase)
Digestive enzymes breakdown glucose
Describe fat digestion…
Large lipid globules + bile salts= small lipid globules
Don’t break bonds but separating larger lipids into smaller lipids
Emulsification, bile salts
Describe the process of fat absorption
- Bile salts from liver coat fat droplets (emulsification)
- Lipases from pancreas break down fat into monoglycerides and fatty acids
- Monoglycerides and fatty acids enter cells of SI by diffusion
- Absorbed fats combine with cholesterol and proteins in the cell to form chylomicrons (lipid droplet)
- Chylomicrons are removed by the lymphatic system by exocytosis into the vena cava
What effects do the parasympathetic and sympathetics have on the pancreas
Parasympathetic= enhances rate of secretion of alkaline juices (bicarbonate) and digestive enzymes
Sympathetic= inhibits rate of secretion of alkaline juices (bicarbonate) and digestive enzymes
Identify the 3 main vessels that move blood and bile within the liver:
What do they carry?
Direction of flow?
- Hepatic artery= arrives rich oxygenated blood, toward the central vein
- Hepatic portal vein= nutrients, toward the central vein
- Bile duct= bile from hepatocytes, away from central vein
Why do the hepatic portal vein and hepatic artery have in common?
Same direction of flow, oxygen and nutrients sent to every hepatocytes before dumped into central vein (mixed)
Describe carb absorption
Sodium moves down gradient into cell and glucose moves up gradient into the cell by sodium glucose transporter (2°)
Carbohydrate absorption prevents…
Glucose from leaving in feces
What are the ways protein can be absorbed (most to least common)
- Amino acids enter the cell by 2° transport by Na+ down gradient (uses energy from Na/K ATPase) & AA in cell enter blood by facilitated diffusion
- Di and tri-peptides co transport with H+ into the cell
- Peptides carried across cell by transcytosis
Is Na+ high or low in the interstitial fluid
High
What enhances and inhibits the rate of secretion of alkaline juices (bicarbonate) and digestive enzymes from the pancreas
Ach parasympathetics=enhance
NE sympathetics= inhibits
Describe the properties of a hormone
Potent in small concentrations, regulate biological functions, work thru certain receptors, work with other hormones to elicit a cellular response
Chemical substance secreted by a group of cells into bodily fluids that has a physiological effect on other cells that express the hormones receptors
Hormone
Steroid hormone derivative
Cholesterol
What hormone can diffuse through the membrane vs. cannot, dissolves in plasma
Diffuse through= steroid (non-polar, lipid soluble)
Dissolves in plasma, no carrier= protein
In steroid hormones…
Chemistry:
Half life:
Transportation:
Receptor location:
Mechanism of action:
Chemistry: slow acting but long lasting
Half life: longer (longer to degrade)
Transportation: protein carrier in the blood
Receptor location: Intracellular receptor (in cell)
Mechanism of action: initiates cellular transcription
How is the steroid hormone slow acting but long lasting
Slow acting: activate transcription and protein synthesis
Long lasting: protein carriers shield the steroid hormone from degradation
Most common protein carrier
Albumin
Steps for the mechanism of action for steroid hormones
- Lipid soluble hormone diffuses through plasma membrane
- Hormone finds receptor in cell and binds to it
- Hormone finds a specific DNA region
- Produce mRNA —transcription of gene for effector protein
- mRNA read by ribosome
- Synthesis of effector protein—causes cellular response
Example of steroid hormones
Sex hormones
In body builders, testosterone is taken exogenously, which results in ___ formation because ___. As a result, they take a ___
Estrogen, balance
Often take an aromatase inhibitor
In protein hormones…
Chemistry:
Half life:
Transportation:
Receptor location:
Mechanism of action:
Chemistry: fast acting but short lasting
Half life: short (not shielded in blood)
Transportation: dissolved in the blood
Receptor location: plasma membrane receptor
Mechanism of action: binds plasma membrane receptors to second messenger system
How are protein hormones fast acting but short lasting?
Fast acting= amplification
Short acting= freely degraded, not shielded like steroid hormones
Mechanism of action in protein hormone?
- Protein hormone binds to receptor in plasma membrane
- Binding activates a protein kinase
- Protein kinase phosphorylates effector protein
- Activates a cellular response
In what hormone is there no new protein synthesis occurring
Protein
Why can a small amount of protein hormone have s large cellular effects
Amplification
Activation at each step activates a larger and larger number of proteins in…
Amplification of 2nd messenger systems
Ability of a target cell to respond to a hormone
Sensitivity
What’s a reflection of the number of receptors
more__ = more receptors
Sensitivity, sensitive
Decrease in number of receptors
Increase in number of receptors
Down regulation, up regulation
What happens to receptor expression and sensitivity in down regulation vs. up regulation
Decreases vs increases
Chronic stress__ regulates GH receptor
Exercise __ regulates insulin receptor number on muscle cells
Down
Up
Hormone A has a small response but exposure of hormone A to this type of hormone results in a greater response
Permissive effect
Epinephrine weakly stimulates lipolysis but in the presence of T3 and T4 it strongly stimulates lipolysis (increase sensitivity)
Permissive hormone effect
Hormone A and B have a small effect on their own but when released together their effects are greater than the sum of the individual hormones
Synergistic hormone effects
Glucagon and epinephrine work to increase blood glucose levels on their own, but together blood glucose rises even further then the sum of the 2 individual effects
Synergistic
The binding of receptors to second messenger systems amplify the response of a signal in what type of hormone effect
Synergistic
One hormone opposes the actions of another hormone
Antagonistic
Insulin and glucagon have opposing results; insulin decreases glucose levels but glucagon increases glucose levels
Antagonistic hormone effect
Once an endocrine cell secretes a hormone into a fluid (like the blood) the hormone then…
1.
2.
- Travels until it reaches a capillary bed where it diffuses out into the extracellular space (interstitial fluid)
- Hormone binds to cells w its receptor and activates response
Explain carbohydrate metabolism function of the liver
Helps store excess glucose as glycogen and helps replenish plasma when glucose levels low
Explain conjugation of toxic substances in the liver
Increases the hydrophilicity of a substance (more contained and less toxic)
Where are conjugated substances of the liver released?
Released into blood/ cleared or secreted by kidneys (smaller particles) OR released with bile and cleared by intestine (large molecules)
How can the gallbladder get stimulated or inhibited?
Stimulated= CCK (parasympathetics) act directly on smooth muscle of gall bladder
Sympathetic inhibit smooth muscle contraction
Why is emulsifying fats by bile important?
Increases SA for digestive enzymes to degrade lipids
Bile salts remain in the small intensive until….
Absorbed by the ileum
How are bile salts recycled?
Reabsorbed bile salts return back to gallbladder and wait to be secreted; small amount lost in feces
If bile salts/acids aren’t returned to the liver, what will the response be?
Liver increases bile production
Contractions of the haustra in the small intestine help….
Squeeze out water from feces
Function of mass movements of LI
Peristaltic contractions help propel feces forward
Internal anal sphincter:
Type of muscle?
Function?
Involuntary/smooth
When feces touches this it relaxes
External anal sphincter:
Type of muscle?
Function?
Voluntary/ skeletal
Have control over when we “hold it”
What reflex plays a larger role in inhibiting defecation
Long reflex
Explain the defecation reflex for long reflex
Stretch
Mechanoreceptor
Sensory nerve
Integrating center: sacral spinal nerve
Efferent nerve: parasympathetic activation
Increased peristaltic waves in colon and rectum
Relaxations of sphincters=defecation
Explain the short reflex defecation reflex
Stretch
Mechanoreceptor
Sensory nerve
Integrating center: interneuron
Efferent nerve: myenteric plexus
Increased peristaltic waves in colon and rectum
Relaxations of sphincters=defecation
stimulating
hormones that target other glands
resulting in the release of a second
hormone (peripheral hormone)
Tropic hormones
Tropic hormones activated the release of what tier of hormones
3 for cellular response
move through the blood until they reach their target organ in the body
Peripheral hormones
A hormone that is secreted from the
pituitary that does not elicit the
secretion of a new hormone is a…
Direct hormone
A patient has a tumor in the anterior pituitary that causes hyper release of stimulating hormones.
In regards to the cortisol pathway, which hormones would you expect to be elevated? What would be low?
ACTH and cortisol are elevated and CRH is low
A person with Graves disease produces proteins called antibodies that mimic the actions of TSH (The body thinks the antibodies are TSH).
If you were to take a blood sample from this patient, describe the levels of TRH, TSH and T3 and T4 that you would expect to see.
TRH and TSH are decreasing
T3 and T4= increasing
Explain the 3 tiers of the anterior pituitary
Tier 1= releasing hormones from hypothalamus
Tier 2= delivery of hypothalamus hormones and release of AP hormones (stimulating hormones)
Tier 3= delivery of AP hormones to target organs (peripheral hormones)
What is an extension of the hypothalamus and how
Posterior pituitary: neurosecretory cell bodies originate in the hypothalamus and axons extend into PP
What hormones do neurosecretory cells produce
Oxytocin and ADH
Doesn’t have specialized cells that secrete hormones
Posterior pituitary
Doesn’t synthesize hormones, hormones come from cells in hypothalamus
Posterior pituitary
Contains a set of hormone, special secreting cells that are sensitive to hormones secreted from hypothalamus
Anterior pituitary
Hormones secretes by the hypothalamus will activate a subset of cells in the ___ that respond by secreting a 2nd hormone into the blood
Anterior pituitary
The neurons in the hypothalamus are connected to the anterior pituitary by
Portal system
Functions of growth hormone?
- Metabolic switch (direct)= occurs during short periods of fasting to maintain blood sugar (body switches from using glucose for energy to using fatty acids)
- Promote growth (tropic)= GH activates the release of insulin such as (IGF-1)
Promotes the growth and development of bones, neurons, and other tissues
IGF-1
Effect of cartilage cells with IGF
Cartilage cells increase with IGF
What happens to the cartilaginous epiphyseal plate before puberty
when stimulated by IGF —> causes you to grow
What happens to the growth plate after puberty
Seals and calcifies (adult height)
What is growth hormones role after puberty
Maintains bone
Excessive bone growth=
Excessive growth causes bone thickening and soft tissue overgrowth=
Gigantism
Acromegaly
Increasing the peripheral hormones has what effect on releasing and stimulating hormones
Inhibits them (tier 3 inhibits tier 1 and 2)
Increasing the stimulating hormones has what effect on the releasing hormone
Inhibits (tier 2 inhibits 1)
Inhibiting the release of releasing and stimulating hormone allows for…
Regulation of the amount of peripheral hormone
Stimulates gluconeogenesis, raise BP, anti-inflammatory
Cortisol
What’s the stimulus for cortisol release
Stress (low blood sugar, trauma, cytokines)
Describe the cycle of cortisol release and negative feedback
Stress—> CRH released through the hypothalamic portal system —> ACTH released in bloodstream —> cortisol released from the adrenal gland
Increases in cortisol inhibits the release of CRH and ACTH
Regulates BMR, enhance actions of epi, regulate development of nervous tissue and growth
Thyroid (T3 and T4)
Stimulus of thyroid (T3 and T4)
Low blood levels of T3 and T4
Describe the cycle of thyroid (T3 and T4) release and negative feedback
Low levels in blood —> TRH released through the hypothalamic portal system -> TSH released in bloodstream —> release of T3 and T4
Increasing T3 and T4 inhibit the release of TRH and TSH
Stimulus of growth hormone release
Hypoglycemia, low fatty acids in blood, and deep sleep
Describe the cycle of growth hormone release and negative feedback
Stimulus—> GHRH released through the hypothalamic portal system —> GH released —> release of IGF 1 (tropic) and direct effects on metabolism
Increasing GH and IGF-1 inhibits the release of GHRH and GH
Protein digestion first occurs in the stomach before the small intestine by…
Pepsin, from pepsinogen and acidic environment
Absorption of water relies on the absorption of
Sodium
If sodium moves into the cell, then the water concentration on the outside of the cell ___
Increases
Increased testosterone in the plasma would feedback negatively to the hypothalamus __________ GnRH.
Inhibiting
Decreased GnRH leads to a decrease in
FSH and LH
Is homeostasis a steady state or equilibrium
Steady state
Dynamic process that uses the systems of the body to maintain a constant internal environment
Homeostasis
What fluid is regulated by homeostasis
Interstitial fluid
Interstitial fluid is directly related to
Plasma, if plasma o2 drops then interstitial o2 drops
What is not considered a part of the internal environment
Intracellular fluid
Semen composed of
Sperm cells and seminal plasma
Most semen comes from
Accessory organs
Support and protect the developing sperm
Sertoli cells
Describe the sperm anatomy
Head = acrosome, helps egg and sperm fuse in fertilization (contains enzymes)
Midpiefe= mitochondria to provide atp for tail
Tail= allow movement in ejaculation
Describe meiosis in males and females in reproductive system
Parent cell germ cell
1. Diploid (23 and 23)
2. Crossing over occurs: 46 and 46
3. Divides into 2 cells (each with two 23 - cells are genetically different from parent)
4. Those cells divide into 4 cells, haploid that are unique
In females: 1 parent cell= 1 egg cell (oocyte) and 3 polar bodies
Describe mitosis in reproduction
Parent cell is somatic cell
1. Begins with a diploid cell
2. Dna replication, cell contains 2 sets of 46
3. Splits into two cells each with two sets of 23 (genetically identical)
Explain the process of gametogenesis/spermatogenesis
The the phase of spermiogenesis
Spermatids are formed and differentiation of spermatids to sperm cells
Explain the process of gametogenesis/spermatogenesis
The the phase of spermiation
Sperm released from serotoli cells and enter seminiferous tubules
Explain the process of gametogenesis/spermatogenesis
The phases in order
Spermatocytogenesis
Spermiogenesis
Spermiation
Explain the process of gametogenesis/spermatogenesis
The the phase of spermatocytogenesis
- Spermatogonium undergoes Mitosis which produces and replenishes stem cells
- Meiosis 1: produces two secondary spermatids (haploid)
- Meiosis 2: produces 4 haploid spermatids
Produce testosterone
Leydig cells
Increase transport of cholesterol into these cells, increase transcription of enzyme involved in testosterone production
Leydig cells
Leydig cells are stimulated by
LH
Testosterone from the leydig cells diffuse over to…
Sertoli cells (and blood) and stimulate spermatogenesis
FSH stimulates the production of substances that promote the development of sperm in what cell
Sertoli cell
What produces ABP and inhibin
Sertoli cells
Function of ABP
Binds diffusing testosterone to keep levels high in Sertoli cells enhancing spermatogenesis
When sperm production levels are high enough, the Sertoli cell produces
Inhibin
What cell expresses inhibin produced?
What produces inhibin?
FSH producing cells
Sertoli cells
Inhibin inhibits what
FSH and LH release in AP
Feedback regulation or hypothalamus and AP (regulation of LH and fsh)
Testosterone
Describe the relationship of testosterone during pre-puberty
Very sensitive to testosterone and little testosterone can turn off hormones in hypothalamus and AP, hypothalamus has an increased number of testosterone receptors
Describe the relationship of testosterone during puberty
Brain becomes less sensitive to testosterone, results in increased hormone and ABP production
What two things do you need to produce and/or restore sperm production if decreased
FSH and testosterone
Describe the pathway of testosterone release
Low testosterone levels (stimulus)—> GnRH released from hypothalamus through portal system —> LH and FSH released from AP into bloodstream
Pathway of FSH in males
Stimulates ABP and inhibin production—> spermatogenesis
Describe the pathway of LH in males
LH stimulates Leydig cells —> testosterone produced —> diffuses into Sertoli cell
Negative feedback of testosterone release and inhibin: increase in inhibin…
Increases in testosterone…
Increases in inhibin, inhibits the release of FSH and LH (TIER 2)
Increases in testosterone inhibits GnRH and LH and FSH (tier 2 and 1)
Used by sperm to make Atp
Citric acid
Clots semen after ejaculation
Clotting enzymes
What in the seminal secretions is protective from the acidic environment
Bicarbonate and clotting enzymes
Break down clots in seminal secretions once acidic environment is neutralized
Proteolytic enzymes
Antibiotic in seminal secretions
Seminal plasmin
Development of male or female internal and external genitalia
Phenotypic sex
Do the genotypic and phenotypic sex match always?
Don’t always match if XY male doesn’t have SRY gene
SRY gene
Located where:
Y chromosome
Stimulates neutral gonadal tissue differentiation into testes (testes formation)
SRY gene
The lack of the SRY gene results in
Female genitalia
Two functions of the ovaries
Produce eggs and secrete sex hormones
Follicles contain a __ and once it’s matured it is a __
Oocyte, ovum
In oogenesis, for every 1 oogonium there’s..
1 ovum (gamete) formed
What happens in meiosis 1 of oogenesis
Produces a primary oocyte from oogonium
What happens in meiosis 2 in oogenesis
Secondary oocyte and 1st polar body is produced, ovulation of secondary oocyte, after fertilization meiosis 2 resumes and oocyte turns into ovum and 2nd polar body
What joins together in ferlization?
Secondary oocyte and sperm cell
Explain the pathways for female sex hormones and estrogen release (LH and FSH pathway)
GnRH released from hypothalamus —> LH and FSH released into blood
LH in blood —> stimulates theca cells to produce androgens —> androgens diffuse into granulosa cells —> converted to estrogen
FSH in blood —> stimulate estrogen production —> when estrogen levels rise, granulosa cells secrete inhibin
Explain the negative and positive feedback of female sex hormones…
Increases in inhibin….
Mid levels of estrogen…
Increases in inhibin, inhibits FSH and LH (tier 2)
Mid levels of estrogen inhibits GnRH, FSH, and LH release
Positive feedback: estrogen continues to be produced and granulosa cells continue to divide until LH spike (ovulation)
Works as a transcription factor what 2 female hormones?
Estrogen and progesterone
Endometrial proliferation, granulosa cell expansion (division) increases this hormone…
Estrogen
Prepares the uterine tract for pregnancy, growth and differentiation of endometrium (becomes thicker and turns into a gland during implantation)
Progesterone
Suppresses myometrium contractile activity (keeps smooth muscle quiet until labor)
Progesterone
Inhibits milk production, from the placenta
Progesterone
When FSH levels are too high, what is released
Inhibin
Explain why perimenopausal women have anovulatory periods
Harder to ovulate because no period, LH spike; GnRH, LH, and FSH increase and estrogen decreased
Explain why a young girl may have a period without ovulation?
Estrogen levels may increase and proliferation of the uterus may occur but not enough to activate LH spike, differentiation of uterus
In a period, over time, follicles will die and estrogen will decrease resulting in…
Shedding of endometrium
Explain how oral contraceptives inhibit ovulation?
Taking exogenous estrogen and progesterone inhibits GnRH, LH, FSH and turns off granulosa and theca cells —> no estrogen or LH spike
When you take oral contraceptives, what happens to endogenous estrogen and proliferation or endometrium
Decreases
The sugar birth control pills represent….
Corpus albicans (what’s shed in period)
What happens during menopause
Ovaries run out of follicles, estrogen decreased and GnRH, LH, and FSH increased
Relationship of estrogen and sensitivity in pre- puberty and during puberty…
Pre= hypothalamus super sensitive to estrogen
During= brain less sensitive, less receptors (increased GnRH, LH, FSH, estrogen, androgens, and inhibin)
If pregnancy occurs, what happens to the corpus luteum?
Will stay alive and continue to produce hormones until the placenta can take over
If corpus luteum dies during pregnancy what happens….
No glycogen produced, lining can’t thicken for egg (miscarriage)
If pregnancy doesn’t occur what happens to the corpus luteum?
It does and forms corpus albicans, doesn’t produce hormones and endometrium sheds (menstruation)
Order of cycle in female
Follicular phase, contains proliferation phase
Ovulation
Luteal phase, contains secretory phase of egg implants
Menstruation if not pregnant
What happens during the proliferation phase in female
Uterine lining thickens, From menstruation shedding lining (result of high estrogen)
Describe the follicular phase if there are low levels of estrogen
- Releases GnRH from hypothalamus
- LH and FSH released from AP (targets ovaries)
- LH goes to Theca cells to stimulate androgen production
- FSH accumulates in antrum/follicle and stimulates estrogen production in granulosa cells
- Granulosa cells take up androgens and make estrogen
- Estrogen expands granulosa population (which thickens lining) and they keep dividing in ovary until high enough estrogen levels
- Estrogen from follicle stimulates endometrial growth and proliferation
Has cholesterol backbone, aromatase modifying
Androgen
The dominant follicle will accumulate the most… and is the most sensitive
FSH
When there are midrange levels of estrogen, what occurs
Inhibits GnRH, LH, FSH
Estrogen produced until ovulation
When there are high levels of estrogen, what occurs
Activates the release of GnRH because LH spike
Result of LH spike that releases the egg, marks the end of follicular phase and star of luteal phase
Ovulation
How does ovulation occur?
- High levels of estrogen from granulosa cells stimulates GnRH release
- Increased GnRH results in a surge of mainly LH from AP
- Increase LH from high estrogen=LH spike which released the egg
What determines when ovulation occurs and how?
Follicle; once it makes enough estrogen
What happens at the secretory phase in females
Glycogen is produced, GnRH, LH, FSH inhibited; promotes differentiation of lining converting it into a gland
Progesterone inhibits what tiers and why?
1 and 2, you don’t want those hormones being released and want to see if egg gets fertilized
Explain the steps in the luteal phase
- Ruptured follicle turns into corpus luteum
- CL secretes high levels of progesterone and some estrogen
- Progesterone promotes differentiation of lining and turns it into a gland for egg
- Estrogen helps with growth and maintenance of endometrium
Primary hormone producing structure in luteal phase
Corpus luteum
The corpus luteum consists of
Granulosa cells
More receptors for __ = most responsive follicles
LH and FSH
Describe what happens when egg is fertilized by sperm?
- Sperm binds to ZP3 receptor on egg’s surface
2.Triggers the acrosomal reaction and release of enzymes onto egg’s surface - Acrosomal rxn dissolves a hole in the zona pellucida allowing the sperm entrance into egg
fusion of sperm to egg activates pathways that block
polyspermy
How is polyspermy prevented?
Immediately after egg is fertilized, it initiates cortical rxn
Explain the cortical reaction, what two things occur to prevent polyspermy?
- Deactivation of all remaining ZP3 receptors (prevents other sperm from binding egg)
- Depolarization of oocyte: hardens zona pellucida
Describe dizygotic twins and monozygotic twins
Dizygotic- 2 eggs, 2 sperm (fraternal)
Mono- 1 egg, 1 sperm (identical twins)
Describe the embryonic development of forming a blastocyst
- Zygote divides by mitosis
- Development of many cell types start by day 5 to form blastocyst
- Trophoblast and inner cell mass
Forms the placenta, forms outside shell of blastocyst
trophoblast
Located inside blastocyst, will become the embryo
inner cell mass
Embryo burrow deep into uterine wall
implantation
Inner cell mass aligns with the wall of uterus and releases enzymes to attach to wall in what
implantation
The endometrium is rich in ___ due to what hormone
glycogen and blood vessels, progesterone
The blastocyst secretes __ in what phase
HCG, implantation
IN the implantation phase, the release of ___ breaks down the uterine wall to gain access to the blood source
proteolytic enzymes
What phase do cells in blastocyst become specialized, 3 layer differentiate
Gastrulation
Becomes the lining of GI in fetus=
Becomes skin and nervous tissue=
BEcomes muscle, bonds, and connective tissue
endoderm
Ectoderm
Mesoderm
Where does gas and nutrient exchange occur in mother and fetus
chroionic villi and mother blood supply
What is released from mom to fetus and how:
What is released from fetus to mom and how:
Mom to fetus: by veins, O2, nutrients, hormones, antibodies, and drugs
Fetus to mom: by arteries, CO2, metabolic waste, hormones
Females who are pregnant do not get periods because
high progesterone, inhibits menses
Produced by placenta
Estrogen and progesterone
How does progesterone keep myometrium quiescent (non-contractile)
- Increased K+ channel expression (easier for K+ to leave, hyper-polarizes membrane)
- Suppresses gap junctions between smooth muscles
Progesterone inhibits what
Gnrh, FSH, LH, and prolactin
Main hormone producer in pregnancy
placenta
Estrogen increases what receptor during pregnancy
oxytocin
How does HCG communicate with the CL to increase production of estrogen and progesterone
bind LH receptor
Known as the pregnancy hormone, increases in first trimester until placenta takes over
HCG
HCG signals from __ to ___
embryo, CL
Stages of labor
Stage 1: dilation of cervix (to 10cm)
Stage 2: expulsion of baby
Stage 3: placental delivery
What helps to soften cervix in first stage of labor
prostaglandins
What increases in the second stage of labor? When does this stage end?
Increased oxytocin release stimulates strong uterine contractions, ends when baby is born
What occurs to prevent hemorrhage in placental delivery
Blood vessel constriction and nursing baby
Positive feedback regulation of labor:
Controlled variable:
Stimulus:
Sensor:
Input:
Controlled center:
Output:
Effectors:
Response:
positive feedback:
Controlled variable: muscle length of cervix
Stimulus: Stretch
Sensor: Mechanoreceptor
Input: sensory neuron
Controlled center: hypothalamus (PP)
Output: oxytocin release
Effectors: uterus
Response:smooth muscle contraction
Positive feedback: more stretch of cervix
What ends positive feedback loop in labor
delievery of baby
Describe milk letdown
Stimulus:
Receptor:
Input:
Controlled center:
Output:
Effectors:
Response:
Positive or negative feedback
Stimulus: nursing at breast
Receptor: mechano
Input: sensory nerve
Controlled center: hypo (PP)
Output: oxytocin release from PP
Effectors: myoepithelial cells on mammary glands
Response: contraction and milk ejection
Positive
In pregnant females the ability to increase…. goes away. The reflex target is mainly on the ___ rather than the ___
TPR; heart, blood vessels
Explain the baroreceptor reflex arcs of an decrease BP as stimulus
Controlled variable:
Receptors:
Input:
Control center:
Output:
Effectors:
Response:
Controlled variable: BP
Receptors: baroreceptors
Input: stretch less, decreases AP rate
Control center: medulla
Output: Increased symp and decreased parasym stimulation
Effectors: heart- increase heart rate and contractility
Response: increase BP
Explain the baroreceptor reflex arcs of an increase BP as stimulus
Controlled variable:
Receptors:
Input:
Control center:
Output:
Effectors:
Response:
Controlled variable: BP
Receptors: baroreceptors
Input: stretch more, increases rate of AP
Control center: medulla
Output: decreased symp and increased parasympathetic stimulation
Effectors: decrease heart rate/contractility and vasodilation/decreased TPR
Response: decreased bp
Stroke volume depends on
contractility
A drop in TPR (low BP) will activate baroreceptor reflex arc–whats the correct input and response
Input: less stretch, less AP firing, increase SNA
Response: increase contractility and heart rate
passing of solutes from the blood into nephron in glomerulus
filtration
If freely filtered, not secreted and not absorbed, clearance ______ GFR
If reabsorbed: clearance ___ GFR
If secreted: clearance ___ GFR
equals
less than Gfr
greater than gfr
what happens to the capillary pressure and GFR when the afferent arteriole dilates
both increase; increase in hydrostatic pressure= increase GFR, decrease in hydrostatic pressure= decrease GFR
If clearance increases, and something is not reabsorbed or secreted: what happens to GFR
increases as well
How would you expect drug dosage to change during pregnancy (Ex. lithium)
Clearance of drugs are higher during pregnancy (increased dosage)
Why is it important to increase blood volume during pregnancy?
Increases blood volume, also increases what during pregnancy?
To meet increased demand for nutrients, oxygen, and waste removal due to growing baby
HR, CO, and contractility
What organ in females also produces renin during pregnancy
Ovaries
Increase in renin release results in increased Na and H2o reabsorption (increases blood volume): How?
Angiotensin II increases aldosterone production: insertion of new Na channels and Na/K ATPases, increases Na reabsorption
Also increases ADH production (from posterior pituitary): insertion of aquaporin channels, increases H2o reabsorption
Highest Na+ concentration and highest H2o water concentration
lumen of distal nephron
Lowest Na+ concentration and lowest H2o water concentration
cytoplasm of cell
As Na+ leaves the lumen of the collecting duct, what happens to H2O Concentration
increases in the lumen
