Psychology - Problem Drill 05: Endocrine System & Influence on Behavior

Transcription

1 Psychology - Problem Drill 05: Endocrine System & Influence on Behavior No. 1 of Which of the following statements is FALSE regarding the interaction between the nervous an endocrine systems? (A) It takes longer for the hormones of the endocrine system to find and affect their targets. (B) The effects of the hormones tend to last longer than those of the nervous system. (C) Researchers have discovered that certain neurotransmitters can act on distant targets. (D) Both the nervous system and the endocrine system have a large effect on behavior. (E) The distinction between neurotransmitters and hormones is very clear. It is true that it does take longer for the hormones of the endocrine system to find and affect their targets compared to the nervous system. It is true that the effects of hormones tend to last longer than those of the nervous system. It is true that researchers have discovered a certain neurotransmitters can act on distant targets. It is true that both the nervous and endocrine system have a large effect on behavior. E. Correct! The distinction between certain neurotransmitters and hormones is no longer clear when hormones are released by glands. The cells in your body communicate through chemical messengers. The nervous system uses chemical messengers, called neurotransmitters, at each synapse (the gap between neurons or between a neuron and a target tissue, such as a muscle cell), and thus represents a point-to-point system of connection. However, there is a second communication system in your body. The endocrine system consists of a number of glands that secrete chemical messengers, called hormones. These hormones travel through the blood stream to distant targets. Both the nervous system and the endocrine system have a large effect on behavior and there is a great deal of interaction between them. However, the speed and duration of their effects are different. The nervous system sends messages very quickly while it takes longer for the hormones of the endocrine system to find and affect their targets. However, the effects of the hormones tend to last longer. Researchers have discovered that neurotransmitters can drift in the brain s fluid to nerve receptors at distant sites, which is a characteristic of a hormone, thereby affecting overall alertness or mood. In such cases, the distinction between certain neurotransmitters and their chemical twins; which are called hormones when released by glands; is no longer so clear. Conducting and coordinating this whole electrochemical orchestra is that maestro we call the brain. Again we are reminded of our overriding principal in psychology: that everything psychological is simultaneously biological.

2 No. 2 of Which of the following is NOT a criterion for categorizing a chemical as a hormone? (A) A hormone must be a chemical that is secreted by a cell or group of cells. (B) A hormone must be able to exert its effect only at very high concentrations. (C) A hormone must be secreted into the blood. (D) A hormone is transported to a distant target. (E) There must be a mechanism in place that can terminate the hormone s action. It is true that a hormone must be a chemical that is secreted by a cell or group of cells. B. Correct! One criterion is that a hormone must be able to exert its affect at very LOW concentrations, not high concentrations. It is true that a hormone must be secreted into the blood. It is true that a hormone is transported to a distant target. It is true that in order for a chemical to be categorized as a hormone, there must be a mechanism in place that can terminate the hormone s action. Hormones originate in one tissue, travel through the bloodstream, and affect other tissues, including the brain. When they act on the brain, they influence our interest in sex, food, and aggression. But how are hormones defined? In order for a chemical to be categorized as a hormone, it must meet specific criteria. A hormone must be a chemical that is secreted by a cell or group of cells. It must be secreted into the blood and transported to a distant target. It must exert its effect at very low concentrations and act by binding to receptors. At finally, there must be a mechanism in place that can terminate the hormone s action.

3 No. 3 of Which of the following pairing of endocrine gland to main function is FALSE? (A) The pancreas which regulates the level of sugar in the blood. (B) The thyroid gland which affects metabolism. (C) The adrenal glands which are called the master gland because they affect so many other glands. (D) The hypothalamus; which is the brain region controlling the pituitary gland. (E) The pituitary gland which secretes many different hormones, some of which affect other glands. It is true that the pancreas which regulates the level of sugar in the blood. It is true that the thyroid gland which affects metabolism. C. Correct! The adrenal glands which help trigger the fight or flight response. Instead, it is the pituitary gland that is called the master gland. It is true that the hypothalamus which is the brain region controlling the pituitary gland. It is true that the pituitary gland which secretes many different hormones, some of which affect other glands. The main glands of the endocrine system include: The hypothalamus which is the brain region controlling the pituitary gland. The pituitary gland which secretes many different hormones, some of which affect other glands. The thyroid gland which affects metabolism, among other things. The adrenal glands which help trigger the fight or flight response. The pancreas which regulates the level of sugar in the blood. The ovaries which secrete female sex hormones. The testes which secrete male sex hormones.

4 No. 4 of 10 on paper as needed, (3) Pick the answer, and (4) Review the core concept tutorial as needed. 4. Which of the following statements is TRUE regarding the hypothalamus and homeostasis? (A) The hypothalamus regulates these levels in response to a changing internal environment through a regulatory process known as homeostasis. (B) The hypothalamus contains temperature-sensitive cells which detect variations in body temperature and orchestrate the appropriate response. (C) If you are cold, dehydrated, and depleted of energy, the appropriate humoral and visceromotor responses must be consciously initiated. (D) When you are cold, hypothalamic influences cause blood to move to the peripheral tissue. (E) The lateral hypothalamus is involved in initiating some motivated behaviors. The hypothalamus regulates these levels in response to a changing external environment through a regulatory process known as homeostasis, not internal. The purpose of this is to maintain the internal environment in response to a changing external environment. The hypothalamus contains temperature-sensitive cells which detect variations in BRAIN temperature and orchestrate the appropriate response, not in body. There are other mechanisms to control body temperature. If you are cold, dehydrated, and depleted of energy, the appropriate humoral and visceromotor responses kick in automatically. When you are cold, hypothalamic influences cause the blood to be shunted towards the core of the body, away from the peripheral tissues. E. Correct! It is true that the lateral hypothalamus is involved in initiating some motivated behaviors such as seeking warmth when you are cold or removing clothing when you are hot. Homeostasis can be defined as the maintenance of the body s internal environment in response to a changing external environment. In mammals, the requirements for life include a narrow range of body temperatures and blood compositions, no matter what the conditions are outside of the body. The hypothalamus regulates these levels in response to a changing external environment through a regulatory process known as homeostasis, or the maintenance of the body s internal environment. The hypothalamus contains temperature-sensitive cells which detect variations in brain temperature and orchestrate the appropriate response: either causing the body to shiver, develop goose bumps, or turn blue; all an attempt to heat up the core temperature; or if the body is too hot, the hypothalamus sends signals to make you turn red and sweat; in an attempt to cool down the body. The hypothalamus must also maintain a very narrow range in blood compositions to include blood volume, blood pressure; the amount of salts (electrolytes) in the blood, the ph or acidity, and blood oxygen and blood glucose levels; and it does so by a variety of means that all involve chemical release. If you are cold, dehydrated, and depleted of energy, the appropriate humoral and visceromotor responses kick in automatically. You will begin to shiver and blood will be shunted away from the body surface in an attempt to keep your core body temperature constant. Your urine production will be inhibited and your body fat reserves will be mobilized, and so on. But the fastest and most effective way to correct these disturbances of brain homeostatis is to seek or generate warmth by moving, to drink water, and to eat. You will be motivated to do so. These are examples of motivated behaviors generated by the somatic motor system, and they are incited to occur by the activity of the lateral hypothalamus.

5 No. 5 of Which of the following statements is TRUE regarding the pituitary gland? (A) The anterior pituitary is considered a true gland. (B) The hypothalamus controls the two lobes of the pituitary gland in the same way. (C) The anterior pituitary is neural tissue derived as part of the brain. (D) The cell bodies of the magnocelluar neurosecretory cells are found in the posterior pituitary. (E) TRH and CRH are two of the hormones secreted by the anterior pituitary. A. Correct! It is true that the anterior pituitary is considered a true gland since it synthesizes and secretes its own hormones. The hypothalamus controls the two lobes of the pituitary gland in different ways. Instead, the posterior pituitary is the neural tissue derived as part of the brain. Anterior pituitary is an actual gland. It is the axons of the magnocellular neuroscretory cells that are found in the posterior pituitary, not cell bodies. Instead, TRH and CRH are secreted by the hypothalamus; not anterior pituitary. It is TSH and ACTH that are secreted by the anterior pituitary. The hypothalamus controls the two lobes of the pituitary gland in different ways. The posterior pituitary is the neural tissue derived as part of the brain and is therefore not actually a gland. It contains a circuit of tiny blood vessels, capillaries, which travel through it in hopes of picking up useful substances. The Magnocellular neurosecretory cells are the largest hypothalamic cells. These cells have their cell bodies located in the hypothalamus and extend their axons down into the posterior pituitary. These cells release two neurohormones into the capillaries located in the posterior pituitary: oxytocin and vasopressin. Both of these chemicals are peptides. The anterior pituitary is an actual gland; meaning it does synthesize and secrete its own hormones. It is under the control of the hypothalamus. They hypothalamic neurons do not extend axons all the way into the anterior pituitary as they do in the posterior pituitary but instead the hypothalamus releases hormones of its own that will then stimulate or inhibit the release of hormones from the anterior pituitary. The hormones released by the hypothalamus enter the blood through a special hypothalamo-pituitary portal circulation. These hormones then travel downstream in the portal circulation until they bind to specific receptors on the surface of anterior pituitary cells which will then either stimulate secretion of hormones from these pituitary cells or stop secretion of hormones (inhibit). There are a large number of hormones synthesized in the hypothalamus that affect the anterior pituitary, which in turn affect various organs in the body, which in turn release their own hormones which affect many different tissues. The hormones released by the hypothalamus towards the anterior pituitary include: TRH, CRH, CHRH, and GnRH which in turn affect the release of TSH, ACTH, GH, FSH and LH from the Anterior Pituitary. These in turn, affect the thyroid gland, the adrenal cortex, the liver and the endocrine cells of the gonads. Each of these organs is then stimulated to release thyroid hormones, cortisol, IGFs androgens and estrogens & progesterones. Various target tissues are affected by these hormones.

6 No. 6 of Which of the following statements is FALSE regarding the adrenal gland? (A) The adrenal glands sit atop the kidneys. (B) Each adrenal gland is actually two glands of different embryological origins that fused during development. (C) The adrenal cortex secretes Aldosterone, glucocorticoids and a small amount of sex hormones. (D) The adrenal cortex is often described as a modified sympathetic ganglion. (E) When cortisol is released by the adrenal cortex, it affects many tissues. It is true that the adrenal glands sit atop the kidneys. It is true that each adrenal gland is actually two glands of different embryological origins that fused during development. It is true that the adrenal cortex secretes aldosterone, glucocorticoids and a small amount of sex hormones. D. Correct! It is the adrenal medulla that is often described as a modified sympathetic ganglion, not adrenal cortex. It is true that when cortisol is released by the adrenal cortex, it affects many tissues. The adrenal glands sit atop the kidneys. Like the pituitary gland, each adrenal gland is actually two glands of different embryological origins that fused during development. The adrenal medulla, which forms the small core of the gland, develops from the same tissue as sympathetic neurons and is a neurosecretory structure that secretes primarily epinephrine into the blood. The cells in the adrenal medulla are stimulated by sympathetic neurons that project from the spinal cord. Thus, the adrenal medulla is often described as a modified sympathetic ganglion. The outer portion, the adrenal cortex, is a true endocrine gland that secretes steroid hormones. Specifically, it secretes aldosterone (affects sodium and potassium), glucocorticoids (increases plasma glucose levels), and a small amount of sex hormones. Of these hormones, cortisol is the main glucocorticoid secreted by the adrenal cortex Let s briefly run through the hormone cascade in the HPA axis. The hormone cortisol affects many tissues and is released from the adrenal cortex in response to an elevation in the blood level of ACTH (adrenocorticotropic hormone). ACTH is released by the anterior pituitary gland in response to CRH (corticotropin-releasing hormone). CRH is released into the blood of the portal circulation by neurons in the hypothalamus. Thus, this arm of the stress response can be traced back to activation of the CRH-containing neurons of the hypothalamus. Much can be learned about anxiety disorders by understanding how the activity of these neurons is regulate. For example, when CRH is over-expressed in genetically engineered mice, the animals display increased anxiety-like behavior. When the receptors for CRH are genetically eliminated from mice, they have less anxiety-like behavior than normal mice. When cortisol is released, it affects many different tissues. It suppresses the immune system. In the liver, cortisol stimulates the conversion of stored glycogen into glucose. In muscle cells, cortisol stimulates the breakdown of muscle as fuel and in adipose tissue; it stimulates the breakdown of lipids into another available fuel source. All this is done to assist the body in preparing for the flight or fight response.

7 No. 7 of Which of the following statements is FALSE regarding the Thyroid gland? (A) C-cells of the thyroid gland secrete calcitonin. (B) The hormones T3 and T4 are released from the thyroid gland in response to an elevation in the blood level of TSH. (C) A decrease in T3 and T4 suppresses secretion of TSH and TRH. (D) The actions of thyroid hormones are most observable in people who suffer from either hyper-secretion or hypo-secretion. (E) Thyroid hormones have long-term effects on metabolism. It is true that C-cells of the thyroid gland secrete calcitonin. It is true that T3 and T4 are released from the thyroid gland in response to an elevation in the blood level of TSH. C. Correct! It is an INCREASE in T3 and T4 that suppresses secretion of TSH and TRH (negative feedback), not a decrease. It is true that the actions of thyroid hormones are most observable in people who suffer from either hyper-secretion or hypo-secretion. It is true that thyroid hormones have long-term effects on metabolism. The thyroid gland is a butterfly-shaped gland that lies across the trachea and is located just below the larynx in the throat region. It is one of the larger endocrine glands and is composed of two distinct endocrine cell types. C (clear) cells secrete calcium regulating hormone called calcitonin. Follicular cells secrete thyroid hormones. These thyroid hormones contain iodine. Let s briefly run through the thyroid hormone cascade. The hormones T3 and T4 are released from the thyroid gland in response to an elevation in the blood level of TSH (thyroid-stimulating hormone or thyrotropin). TSH is released by the anterior pituitary gland in response to TRH (thyrotropin-releasing hormone). TRH is released into the blood of the portal circulation by neurons in the hypothalamus. Thus, this cascade can be traced back to activation of the TRH-containing neurons of the hypothalamus. As is typical with a negative feedback loop, the secretion of other hormones in the pathway also changes with the increase or decrease in the downstream hormone. In this pathway, it is an increase in T3 and T4 that suppresses secretion of TSH and TRH. The actions of thyroid hormones are most observable in people who suffer from either hyper-secretion or hypo-secretion. Physiological effects that are subtle in normal people often become exaggerated in patients with endocrine disorders. Hyperthyroidism involves the over secretion of thyroid hormones. This causes changes in metabolism, the nervous system, and the heart. Hypothyroidism involves the same systems but has the opposite effect. Thyroid hormones have long-term effects on metabolism. They provide substrates for oxidative metabolism. Thyroid hormones also interact with other hormones to modulate the metabolism of proteins, carbohydrates and fats. They also increase oxygen consumption in most tissues. However, thyroid hormones are not essential for life but do substantially affect the quality of life. Thyroid hormones are essential for normal growth and development in children; especially in the formation of myelin and synapses. Infants born with thyroid deficiency will be developmentally delayed unless treated promptly. All newborns in North America are tested for thyroid deficiency.

8 No. 8 of Which of the following is FALSE regarding the sex hormones? (A) The enzyme aromatase is found only in females. (B) Both sexes produce both androgens and estrogens. (C) Testosterone is converted into its more potent derivative DHT in the peripheral tissues. (D) The pathways that regulate reproduction begin with secretion of peptide hormones by the hypothalamus in the brain. (E) The sex hormones are produced in the gonads under the influence of FSH and LH. A. Correct! Aromatase is an enzyme that is responsible for a key step in the biosynthesis of estrogens. Both sexes produce both androgens and estrogens. The male s testis and female s ovaries contain the enzyme aromatase which converts testosterone to the female sex hormone estradiol. It is true that both sexes produce both androgens and estrogens, but androgens predominate in males, and estrogens are dominant in females. It is true that testosterone is converted into its more potent derivative DHT in the peripheral tissues. It is true that the pathways that regulate reproduction begin with secretion of peptide hormones by the hypothalamus in the brain. It is true that the sex hormones are produced in the gonads under the influence of FSH and LH. The steroid hormones are closely related to one another and arise from the same steroid precursors. Both sexes produce both androgens and estrogens, but androgens predominate in males, and estrogens are dominant in females. 95% of the testosterone is produced in the testis with 5% being produced in the adrenal cortex. Testosterone is converted into its more potent derivative DHT in the peripheral tissues. Some of the physiological effects attributed to testosterone are actually the result of DHT activity. Males synthesize some estrogens. Both testis and ovaries contain the enzyme aromatase which converts testosterone to the female sex hormone estradiol. Estradiol is the main estrogen in humans. In women, the ovary produces estrogens (primarily estradiol and estrone) as well as progestins, particularly progesterone. The ovary and the adrenal cortex produce small amounts of androgens. The pathways that regulate reproduction begin with secretion of peptide hormones by the hypothalamus in the brain which acts on the anterior pituitary. These trophic hormones control gonadal secretion of the steroid sex hormones, including androgens, estrogens, and protesterone. The sex hormones are produced in the gonads under the influence of FSH and LH. FSH and LH are secreted from the anterior pituitary under the influence of GnRH. Gonadotropin-releasing hormone is secreted by the hypothalamus. LH acts primarily on endocrine cells in the gonads, stimulating production of the steroid sex hormones. FSH, along with the steroid sex hormones, is required to initiate and maintain gametogenesis.

9 No. 9 of Which of the following is FALSE regarding feedback regulation within the endocrine system? (A) Excessively high levels of cortisol will suppress secretion of ACTH and of CRH. (B) In a typical negative feedback loop, the secretion of other hormones in the pathway do not change with the increase or decrease in the downstream hormone. (C) Inhibins inhibit FSH secretion while activins, stimulate FSH secretion. (D) Activins also promote spermatogenesis, oocyte maturation, and embryonic nervous system development. (E) Negative feedback loops are present in the HPA axis. It is true that excessively high levels of cortisol will suppress secretion of ACTH and of CRH. B. Correct! In a typical negative feedback loop, hormones in the pathway do change with the increase or decrease in the downstream hormone. It is true that inhibins inhibit FSH secretion while related peptides, called activins, stimulate FSH secretion. It is true that activins also promote spermatogenesis, oocyte maturation, and embryonic nervous system development. It is true that negative feedback regulation occurs in the Hypothalamus-Pituitary- Adrenal axis. regulation for the HPA involves negative feedback loops from cortisol back to the anterior pituitary and the hypothalamus. Excessively high levels of cortisol will suppress secretion of ACTH and of CRH. As is typical with a negative feedback loop, the secretion of other hormones in the pathway also changes with the increase or decrease in the downstream hormone. As is typical with a negative feedback loop, the secretion of other hormones in the pathway also changes with the increase or decrease in the downstream hormone. In this pathway, it is an increase in T3 and T4 that suppresses secretion of TSH and TRH. Although primary control of gonadal function arises in the brain, the gonads also influence their own function. Both ovary and testis secrete peptide hormones that act directly on the pituitary. Inhibins inhibit FSH secretion. Related peptides, called activins, stimulate FSH secretion. Activins also promote spermatogenesis, oocyte maturation, and embryonic nervous system development. These gonadal peptides are produced in nongonadal tissues as well, and their other functions are still being investigated.

10 No. 10 of Which of the following statements is FALSE regarding regulation of the hypothalamus? (A) Regulation of the stress response involves regulation of the Hypothalamic- Pituitary-Adrenal (HPA) axis. (B) Activation of the amygdala causes an activation of the hypothalamus and the HPA axis. (C) Hippocampal activation stimulates CRH release. (D) Continuous exposure to cortisol, such as during periods of chronic stress, can cause hippocampal neurons to wither and die in experimental animals. (E) Inappropriate activation of the amygdala, as measured using fmri, has been associated with some anxiety disorders. It is true that regulation of the stress response involves regulation of the Hypothalamic-Pituitary-Adrenal (HPA) axis. It is true that activation of the amygdala causes an activation of the hypothalamus and the HPA axis. C. Correct! Hippocampal activation suppresses rather than stimulates CRH release. It is true that continuous exposure to cortisol, such as during periods of chronic stress, can cause hippocampal neurons to wither and die in experimental animals. It is true that inappropriate activation of the amygdala, as measured using fmri, has been associated with some anxiety disorders. Regulation of the stress response involves regulation of the Hypothalamic-Pituitary- Adrenal (HPA) axis. This regulation occurs at the amygdala and hippocampus. The amygdala is critical to fear responses. Sensory information enters the basolateral amygdala, where it is processed and relayed to neurons in the central nucleus. When the central nucleus of the amygdala becomes active, the stress response ensues. Downstream from the amygdala is a collection of neurons called the bed nucleus of the strait terminalis. The bed nucleus neurons activate the HPA axis and the stress response. Inappropriate activation of the amygdala, as measured using fmri, has been associated with some anxiety disorders. The HPA axis is also regulated by the hippocampus. However, hippocampal activation suppresses rather than stimulates CRH release. Thus, the hippocampus normally participates in the feedback regulation of the HPA axis by inhibiting CRH release when circulating cortisol levels get too high. Continuous exposure to cortisol, such as during periods of chronic stress, can cause hippocampal neurons to wither and die in experimental animals. This degeneration of the hippocampus may set off a vicious cycle in which the stress response becomes more pronounced, leading to even greater cortisol release and more hippocampal damage. Human brain imaging studies have shown a decrease in the volume of the hippocampus in some people suffering from post-traumatic stress disorder, an anxiety disorder that is triggered by exposure to inescapable stress.