Unit 9 - Endocrine System Flashcards
What are some characteristics of the endocrine system?
- works together with the nervous system
- maintains homeostasis of the body
- produces messengers (hormones) that coordinate the body’s response to different situations and stimulus
- reacts slowly to changes, but it sustains the response for long periods
What is the pathway for the endocrine system signalling?
endocrine gland cells -> hormones (messengers) -> (blood stream) to target tissues
What are the differences between the nervous system and the endocrine system?
Overall function - both maintenance of homeostasis
Reaction to stimuli:
endocrine - slow
nervous - short
Duration of effects:
endocrine - long
nervous - short
Target tissues:
endocrine - most of the body cells and tissues
nervous - muscle and glandular tissues
Chemical messenger:
endocrine - hormone
nervous - neurons
Communication with target tissues:
endocrine - via bloodstream (long distance)
nervous - via synapses (short distance)
What are the basic unit of the endocrine system?
endocrine glands (ductless glands)
Where are the endocrine glands located?
throughout the body
What do the endocrine glands secrete?
small amounts of hormones directly in the bloodstream
What do exocrine glands do?
secrete their products onto epithelial surfaces through the ducts
What are hormones?
chemical messengers produced by endocrine glands
Where do hormones travel?
in the bloodstream to all parts of the body
What do hormones bind to?
they bind to their particular receptors in or on the target cells
What are the three groups of hormones?
peptide hormones
steroid hormons
monoamine hormones
What are some characteristics of peptide hormones?
- contains 200 or more AA
- hydrophillic (soluble in water)
- easily travels in the blood plasma
What are some characteristics of steroid hormones?
- lipids synthesized from cholesterol
- hydrophobic (insoluble in water)
- must bind to a transporter protein to travel in the plasma
- can easily diffuse into cell membrane
What are some characteristics of monoamine hormones?
- derived from amino acids and retain an amino group
- contains both hydrophillic and hydrophobic type of hormones
What is hormone secretion controlled by?
feedback system
- levels of the hormone “feed back” the gland that produces it
- this feedback can increase or decrease the production levels of the hormone
What is negative feedback vs positive feedback?
negative feedback - rising levels of the hormone decrease the activity of the gland
positive feedback - falling levels of the hormone increase the activity of the gland
What is the hormone feedback cycle of the anterior pituitary gland and TSH?
Anterior pituitary gland produces thyroid stimulating hormone (TSH) which activates the thyroid gland which produces thyroid hormones, if the levels of thyroid hormone drop too low/raise too high, feedback goes to the anterior pituitary gland to produce more/less TSH
What is the hypothalamus a part of?
the diencephalon of the brain
What does the hypothalamus control?
hormone release from the pituitary gland by producing, releasing, or inhibiting hormones under the control of nervous impulses
Where is the pituitary gland located?
ventral to the hypothalamus and is attached to it by a slender stalk
What do blood vessels and nerve fibers do in the hypothalamus stalk?
blood vessels and nerve fibers in the stalk enable the hypothalamus to control the activity of the pituitary gland and therefore most of the rest of the body
What is the relationship of the hypothalamus and posterior pituitary?
- neurosecretory cells in the hypothalmus produces hormones that are transported down nerve fibers to the posterior pituitary
- the hormones are stored here and their release is controlled by nerve impulses from the hypothalamus
What is the relationship between the hypothalamus and the anterior pituitary?
- hormones from the hypothalamus are secreted into portal blood vessels
- carry them to the anterior pituitary which brings info in
What is another name for the pituitary gland?
hypophysis
What do the hormones in the pituitary gland do?
direct the activity of other endocrine glands in the body
What does the anterior pituitary develop from?
develops from glandular tissue in the embryo
What does the posterior pituitary develop from?
develops from nervous system in the embryo
What is the function of the posterior pituitary gland?
- it does not produce hormones
- it stores and releases two hormones produced in the hypothalamus
What is the function of the anterior pituitary gland?
- produces hormones when stimulated by the hypothalamus and/or when stimulated by direct feedback by target tissues
What do the posterior and anterior pituitary glands look like under a microscope?
posterior - lighter pink
anterior - darker pink
What are the hormones that the anterior pituitary gland produces?
- growth hormone (GH)
- prolactin
- thyroid-stimulating hormone (TSH)
- andrenocortictropic hormone
- follicle-stimualting hormone (FSH)
- luteinizing hormone (LH)
- melanocyte-stimulating hormone
What does the growth hormone do?
- it acts in all body cells to help to regulate the metabolism of proteins, carbohydrates and lipids
- the effects of GH on protein metabolism is to encourage anabolism (enhance tissue growth)
- it causes mobilization of fat tissue and breakdown of lipids for energy production
- it discourages cells to use carbohydrates as energy sources - causing increasing levels of blood glucose
Why do we castrate right after birth?
- less aggression
- when muscles develop, they can use more fat+protein stores
Why do fatty acids release more energy than glucose when they are oxidized?
because they have a lot more carbons in their backbone than glucose
What is the GH effects on muscle tissue? (graph)
free fatty acid graph:
- free fatty acids indicate lipid mobilization on y-axis
- one line is GH infusion the other is saline infusion
- GH infusion has more FFA’s because gh triggers lipid deposition in the body
Glucose graph:
- glucose infusion rate GIR on y-axis
- insulin is injected when the lines go up (insulin is important for glucose uptake)
- GH infusion has more glucose because gh discourages cells to use carbohydrates as energy sources causing increasing levels of blood glucose
What does prolactin do?
- helps trigger and maintain lactation - secretion of milk by mammary glands
- its production and release is stimulated by nursing or milking of the teat. nursing or milking is ceased, its production is ceased as well
What is the prolactin and gh levels due to external stimulus (graph)?
effects of suckling before milking on blood levels of prolactin graph:
- prolactin on y-axis
- two lines, one is with sucking before milking, other is no sucking before milking
- sucking before milking line is is higher in prolactin bevause suckling causes activation of prolactin
effects of sucking before milking on blood levels of GH
- GH on y-axis
- sucking before milking is higher in GH
- gh affects supply and utilization of nutrients in tissues, which affects supply to the mammary gland. the mammary glands function to secrete milk, since calve is nursing the gh is needed to stimulate the mammary gland
What does the thyroid stimulating hormone (TSH) do?
- stimulates the growth and development of thyroid gland, causing it to produce its hormone
- TSH production regulated by thyroid hormone levels - feedback mechanisms previously discussed
What is the relationship of the thyroid hormone production and TSH levels? graph
T4 graph:
- shows T4 decreasing
TSH graph:
- shows TSH increasing
relationship is that if you lower T4 then it stimulates TSH to increase in order to make more T4, a negative feedback loop
What is T4
one of the hormones produces by thyroid gland
What is TSH
hormone produced by pituitary gland that stimulates the thyroid gland
What does the follicle stimulating hormone (FSH) do?
- stimulates the growth and development of follicles in the ovaries, and thus the oogenesis (female gamete production)
- it stimulates the secretion of estrogens (female sex hormone) and stimulates spermatogenesis in the males
What is the function of the luteinizing hormone (LH)?
- it completes the process of follicle development in the ovary that was started by FSH
- once ovulated has occurred, the high LH level sitmulates the cells left behind in the empty follicle to multiple and develop into another endocrine structure - the corpus luteum
- increases the size of the follicle in order to burst antrum and release oocyte
Where does FSH and LH production take place?
hypothalamic-pituitary-gonadal axis
What are the major endocrine glands in males and females?
males
either FSH or LH
FSH -> sertoli cells -> spermatogenesis
LH -> interstitial cells -> testosterone
females
either FSH or LH
FSH -> ovary -> folliculogenesis -> production of estrogen
LH -> ovary -> corpus luteum cells -> progesterone
What does the posterior pituitary gland do?
- does not produce any hormone
- it stores two hormones produced by the hypothalamus and releases it periodically
- releases antidiuretic hormone (ADH) and oxytocin
What are the two hormones that the posterior pituitary gland stores and releases?
ADH and oxytocin
How do the hormones get from the hypothalamus to the posterior pituitary?
nerve impulses from the hypothalamus tell the nerve ending at posterior pituitary when to release them into the bloodstream
What does ADH do?
- helps the body conserve water in times of short supply by acting on the kidneys
- causes the kidneys to reabsorb more water from the urinary they are producing back into the bloodstream
What does oxytocin do?
uterus
- induces contraction by the myometrium
- breeding: help movement of spermatozoa up to oviducts
- parturition: aid the delivery and the expulsion of the placenta
mammary glands
- movement of the milk down to the lower parts of the gland
- the oxytocin circulates down to the mammary gland and causes the cells around the alveoli and small ducts to contract
How does oxytocin act on smooth muscles cells of the myometrium?
endogenous and exogenous oxytocin promotes myometrium contraction by activation of its receptors and its action on the voltage regulated Ca2+ channels that facilitate Ca influx
What does the thyroid gland consist of?
- consists of two lobes located on each side of the larynx
- contains two distinct populations of hormone secreting epithelial cells
- thyroid follicular epithelium
- medullary C cells
What are the two distinct populations of hormone secreting epithelial cells in the thyroid gland?
thyroid follicular epithelium
medullary C cells
Where are hormones produces in the thyroid?
thyroid follicle
What do medullary C cells vs epithelial cells look like under a microscope?
medullary cells look more diluted and do not produce hormones
epithelial cells produce hormones and surround the TF thyroid follicle
What are the steps to the thyroid gland being activated?
anterior pituitary gland -> thyroid-stimulating hormone (TSH) activates -> thyroid gland
-> T3 -> is the most biologically active form of thyroid hormone
-> T4 -> it is converted to T3 in peripheral tissue, mainly the liver, kidney and muscle, as needed
What are the two effects that T3 and T4 cause?
Calorigenic effect
- it regulates metabolic rate of the cells
- it helps to generate heat and maintain body temperature
Protein, carbohydrate, and lipid metabolism
- it may induce protein anabolism or catabolism
- it will depend on the energy availability in diet
What does calcitonin do?
- maintains homeostasis of blood calcium levels (the other is parathyroid hormone)
Where is calcitonin produced?
produced by c cells located between the thyroid follicles
What do the small pale nodules in on or near the thyroid glands produce?
parathyroid hormone (parathormone)
What does the parathyroid hormone do?
it helps to maintain blood calcium homeostasis - it has an opposite effect of calcitonin
What is the pathway of the parathyroid hormone?
PTH secreted by parathyroid gland -> increases renal Ca reabsorption and production of 1,25(OH)2D3 (active form of vitamin D) -> the active form of vit d stimulates Ca absorption by intestinal epithelial cells
What is the pathway of calcitonin?
calcitonin secreted by thyroid gland -> inhibits the resorption of bone Ca and increases urinary Ca loss -> aiming to lower blood concentrations of Ca
What is milk fever and how is it caused?
- parturient paresis (Milk fever) is a common disease following calving in dairy cattle
- it caused by the high demand for Ca when the lactating period begins
- it results from an an inability of homeostatic mechanisms to regulate calcemia
What is the graph for calcium homeostasis graph?
Low hypocalcemia is high levels of calcium AND low levels of PTH
High hypocalcemia is low levels of calcium AND high levels of PTH
Why is there high levels of PTH during milk fever?
trying to compensate for low Ca by being able to absorb more Ca
What is the structure of the adrenal glands?
outer adrenal cortex and the inner adrenal medulla, two glands
What is the adrenal cortex stimulated and controlled by?
adrenocorticopic hormone ACTH - a hormone produced by the anterior pituitary
What are the three groups of hormones produced by the adrenal cortex?
- glucocorticoid hormones
- cortisol
- cortisone
- corticosterone
- mineralocorticoid hormones
- sex hormones (small amounts)
What are three glucocorticoid hormones?
cortisol
cortisone
corticosterone
What do the glucocorticoid hormones do?
have a general hyperglycemic effect (increase blood glucose), activate mechanisms to increase blood glucose levels
What is the pathway of glucocorticoid hormones?
hypothalamus produces CRH which goes to anterior pituitary which then produces ACTH which binds to receptors on adrenocortical cells on the adrenal gland which produces glucocorticoids, high levels produce a negative feedback loop which inhibits hypothalamus and the anterior pituitary, low glucocorticoids create positive feedback loop
How do glucocorticoids signal a target cell?
glucocorticoid complex in cell travels to nucleus and goes to GRE (glucocorticoid response elements) which then controls response
What does the adrenal medulla secrete?
secreting cells are modified neurons, which secretes the hormones in the bloodstream
What are the hormones that the adrenal medulla produce?
epinephrine
norepinephrine
What are the secretion of the adrenal medulla hormones controlled by?
epinephrine and norepinephrine are controlled by sympathetic portion of the ANS
What do epinephrine and norepinephrine do?
the adrenal medullary hormones circulate around the body, helping to produce the whole body fight or flight effect
What causes PSE in meat?
short term stressors before slaughter, the brain sends stress signal to adrenal glands which cause adrenaline and cortisol in blood, the glycogen in the muscle and liver is used as an energy source, energy (increased body temp) and lactice acid produce low muscle pH and PSE
What causes DFD?
long term stressor before slaughter -> brain sends signal to adrenal glands which produce adrenaline and cortisol in blood, the glycogen in the muscle and liver are depleted which causes low glycogen at slaughter and creates less lactic acid and high muscle pH and DFD
What is the pH graph for PSE and DFD?
sudden drop in pH when corpse is still hot causes denaturation and PSE
What are the effects of stress on adrenal hormones and impact on meat quality?
pH in postmortem muscle declines due to the accumulation of lactic acid which causes a reduction in the availability of reactive groups on the muscle proteins for binding water -> the isoelectric point (pl) of a muscle protein is the pH at which the number of negative and positive charges on the protein are essentially equal and the overall net charge of the protein is zero
What is the graphs for the stress effect on meat?
muscle glycogen graph:
highest is control
second is short term
lowest is long term
epinephrine:
highest is long term
middle is short term
lowest is control
tenderness (higher WBSF, tougher the meat)
highest is long term
middle is short term
lowest is control
What is the function of the mineralocorticoid hormones?
has the kidney as its target
regulates the levels of important mineral salts in the body, by doing this we regulate blood pressure
What is the main mineralocorticoid hormone?
aldosterone
What is the cycle for aldosterone?
aldosterone is produced by the adrenal glands, it regulates ions and therefore blood pressure, regulates urine volume, therefore most water reabsorption, causes higher blood volume and therefore pressure
What are some features of the pancreas?
- has both exocrine and endocrine functions
- its endocrine component makes up only a small percentage 1-2% of the total volume of the organ
What are the cells that the pancreas contains?
inside the pancreatic islets
beta cells: produces insulin
alpha cells: produces glucagon
delta cells: produces somatostatin
What is the relationship between glucose and insulin?
when glucose goes up insulin goes down and when glucose goes down insulin goes up
What triggers insulin secretion?
glucose levels in the blood stream
- it may be increased directly by dietary factors
- it may be increased indirectly by action of other nutrients such as fatty acids and proteins
What triggers glucagon secretion?
glucose levels in the bloodstream
- increase at fasting or after intense activity
- also increased intense stress
caused to increase the glucose levels in the blood
