Midterm 2 Essay questions Nov 2023

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Jan 9, 2024

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Midterm 2 questions 1.- A researcher creates a mouse that lacks the SIM-1 gene. What hypothalamic nucleus do you expect to be underdeveloped in this mouse? What peptidergic cell groups would be underdeveloped in these mice? (you need to read the paper on hypothalamic development from the readings). SIM-1 is essential for the expression of various hormones such as Vp and Ot in the paraventricular nuecleus and the supraoptic nucleus. The negative expression of the SIM-1 gene will result in the underdevelopment of the PVN and SON leading to an impaired stress reponse and disrupted osmoregulation. It will also lead to the overdevelopment of the preoptic area which will result in altered sexual behviour. The lack of the SIM-1 gene also leads to dysfunctional peptidergic cell groups in the hypothalmus such as those that produce neuropeptide Y (NPY), POMC, corticotropic releasing hormone, vasopressin, thyrotropin release hormone, somatostatin, and oxytocin. NPY and POMC dysregulation results in increased appetite and loss of appetie regulation resulting in obesity. Dysregulation of CRH and TRH leads to chronic stress issues and thyroid disorders affecting metabolism and energy balance. Dysfunction of vasopressin can lead to dysregulation of the water balance in the body leading to dehydration, dysfunction of SST can affect growth and metabolism and dysfunction of oxytocin can impact social behvaiours and reproductive functions. 2.- If a pregnant mouse is given the drug flutamide, an androgen receptor antagonist, during the second week of pregnancy, what do you expect to see in her male and female offspring? If a pregnant mouse is given the drug flutamide in its second week of pregnancy, the androgen receptor antagonist will interfere with the signalling of androgens such as testosterone, that play a key role in the male reproductive system in male offsprings. The male offsprings will show incomplete development of male reproductive organs, and this can lead to behaviour (for i.e, mating beahiours) that is more feminized . The lack of androgens in male offpsrings can also lead to reduced sperm production and therefore, reduced fertility. The testes will develop in the male offsprings without any of the other male reproductive organs developing, therefore the male offsprings will have a female reproductive system except for the testes remaining. The female offpsrings will have a normal female development as flutamide primarily influence male development. 3.- What would you expect to see in different hypothalamic nuclei of male and female offspring born to a pregnant mouse that was given the drug Latrozole (an aromatase inhibitor)? We would expect to see the following in differet hypothalamic nuclei of male and female offsprigs born to a pregnant mouse that was given the drug Latrozole. In male offsprings, there will be reduced estrogen exposure, and a smaller preoptic area, which will result in incomplete masculization of the brain and less masculinized male-typical mating. Furthermore, the feedback loops and regulation of sex hormones will also be disrupted interfering with the secretion of gonadotropin-releasing hormone (GnRH) and the hypothalamic-pituitary-gonadal (HPG) axis. The lack of GnRH will affect how the quantity of testosterone, androgens and sperm production in male offpsrings and disruption to the HPG axis cab lead to diminished sexual desire and
infertility. Female offsprings will exhibit masculinization due to the interference in signalling of androgens into estrogen, which results in more male-typical behaviours, and brain structures. Letrozale will also affect the production of estrogen leading to fertility problems in female offsprings. 4.- While watching the Ottawa senators, Dr. Alexander Edwards downs a jumbo bag of Doritos and a 2 litter bottle of coke. How would the salt in the doritos affect his osmotic balance? How would the sugar in the coke affect his osmotic balance? What do you expect his levels of angiotensin II, ADH and mineralocorticoids are like in response to the salt loading and then the glucose loading? The salt would affect Dr. Edwards osmotic balance, as the presence of salt will lower the water content in his blood, the brain will pick up on this and signal a lot of ADH release, angiotensin ii, and minerlcorticoids but it reduces aldosterone. The coke will lead to a reduction in ADH, angiotensin ii, and aldosterone but mineralocorticoids may be increased. 5.- A cute puppy (his name is “Draco”) has been going to the park since he was 2 months old, but lately, the puppy has become aggressive to other male dogs and rather “friendly” to female dogs. As he is “befriending” Lola, the neighbours sexy poodle who is in heat, what types of sensory information is Randy receiving to excite him and what brain pathways are conveying this information? (hint: there are two main pathways)? What brain region is critical for integratuing this sensory information with hormonal information? Draco can be aggressive towards other male dogs as they can detect each other’s pheromones that convey Draco about the other male dogs reproductive state, such as if they are looking to mate. The pathway involving sensory information - vomeronasal organ – olfactory bulb – medial amygdala – medial preoptic area – periaqueductal grey and the other pathway is the reward pathway that is activated in response to rewarding stimuli. 6.- Describe the endocrine role of the liver and the kidney in modulating drinking behaviors. The hepatorenal reflex of the liver, helps regulate the blood volume and pressure. The liver detects deviations in the blood osmolality, and the liver signals the kidneys to conserve water. The angiotensinogen protein produced by the liver also regulates blood pressure, therefore if there’s a decrease of blood pressure, the liver turns up the production of angiotensinogen, resulting in increased thirst and water rention by the kidneys. The angiotensinogen interacts with renin from the kidneys to make angioyensis I, which then interacts with ACE2, to become angiotensis II. The renin-angiotensin-aldosterone system (RAAS) is also essential for regulating fluid balance and blood pressure and volume. The kidneys release an enzyme called renin that trigger the production of angiotensis, and signals the release of aldosterone from the adrenal glands. The kidneys also help modulate drinking behaiours with osmoregulation, where the blood becomes too concentrated due to dehydration leading to an increase in thirst. 7.- Describe the neural circuitry that is required for the elicitation of the lordosis reflex. How does estrogen affect this neural circuit?
The brain regions that mediate the estrogen influnces leading to the neural circuit that medidates the lordosis response is as follows: - The spinal module deals with the stretch and flexion reflex to “local business”, the midbrain module bridges the hindbrain module to the hypothalamic module, which provides with endocrine regulation. - Estrogenic hormones work through two, alpha and beta receptors, to elevate mRNA levels and their gene products foster sexual behaviours in female offsprings. - Elevated estrogen levels causes the formation of ovarian follicles, that results in increase of ovarian hormones such as estradiol. The MPN receives this estrogenic input, and sends it to the PAG and spinal cord to coordinatae the posture for lordosis. - Sensory inputs from the vomeronasal organ an sensorymotor information from the skin (lower back area) move up the spinal column and are integrated, in the medial preoptic aream, the MPO and its neighbouring areas are receptive to estorgen and if estrogen is present it will signal to the periaqueductal grey which will signal the motor cortex to send a signal back down the spinal column to contract the lower back muscles and enable the lordosis reflex. 8.- Upon seein the golden arches a teo year old begins hounding his mom saying “I’m hungry! I want to go go to McDonalds!!”. Explain how the arches elicit hunger in this chils using what you know about the effect of a certain hormone on the reward system…. - Upon seeing the golden arches, the boy associates the familiar McDonald logo with delicious food, that causes a spike in dopamine, creating excitement and anticipation . Ghrelin, the hormone that stimulates appetite and food intake is released upon all the cues associated with food( the sight of the golden arches) stimulating hunger. This makes the child reallu hungry and asks his mon for McDonalds.
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