Hormones and Homeostasis Quiz Flashcards
Compare and contrast steroid and peptide hormones (with regard to structure, mode of action, and effect).
From the Notes:
Both…
- Act on target cells/ organs
- Travel through the bloodstream
- Effective at very low concentrations
- Effects last longer than neurotransmitters
Steroid Hormones…
- Ex. Estrogen, Testosterone, Progesterone
- Made from cholesterol (lipid soluble/ nonpolar)
- Pass through plasma membrane (phospholipid bilayer) of target cells (steroids are small, hydrophobic molecules)
- Bind to receptor protein(s) in cytoplasm of target cell, forming a receptor-hormone complex - note that these receptor proteins are often gene regulatory proteins
- Receptor-hormone complex moves into nucleus (through nuclear membrane) and regulates gene expression/ act directly on DNA/ binds to DNA (directly promotes or inhibits transcription of specific genes - which controls protein production in a cell – drastically altering the biochemistry of the cell/ tissue etc.)
- Does not require use of ATP
Peptide Hormones…
- Ex. Insulin, ADH, Glucagon, FSH, LH, Prolactin, Oxytocin, Growth hormones, Leptin
- Made from amino acids (proteins/ water soluble/ polar)
- Do NOT enter target cells (cannot pass through plasma membrane), so bind to receptors on plasma membrane surface (of target cells)
- Binding of hormones to receptors activates a cascade of reactions, carried out by secondary messengers in the cytoplasm of the cell (such as cAMP), which activates or inhibits enzymes/ changes cell’s physiology (such as protein kinase, in the cell).
- Requires use of ATP
From the Worksheet:
14b (mode of action)
a. Steroid hormones enter the cell/pass through the plasma membrane; Peptide hormones do not enter the cell/pass through the plasma membrane
b. Steroid hormones bind to receptor in cytoplasm; Peptide hormones bind to receptor on plasma membrane surface
c. Steroid hormones act directly on DNA; Peptide hormones act through second messenger/cAMP
d. Steroid hormones directly affect gene transcription; Peptide hormones influence enzyme activity/protein kinase
18 (action)
a. both «peptide and steroid hormones» act on target organs/cells
b. both «peptide and steroid hormones» travel through blood
c. the effect of both «peptide and steroid hormones» lasts for a longer time «than neurotransmitters»
both are effective at very low concentrations
d. example of each type of hormone
e. steroid hormones enter cell/cross plasma membrane while peptide hormones do not
f. steroid hormones join receptor in cytoplasm while peptide hormones join receptor on membrane
g. steroid hormone-receptor complex travels to nucleus whereas peptide hormone-receptor triggers a cascade reaction/second messenger
h. steroid hormones activate genes while peptide hormones activate enzymes
i. peptide hormone requires ATP, steroid hormone does not
Know that the hypothalamus controls hormonal secretions by the anterior and posterior pituitary.
KNOW IT! (I don’t think we need to have anything else for this one?) (Laugh at me all you want, Rylee)
Contrast how neurosecretory cells are linked to the anterior and posterior pituitary and cause the anterior and posterior pituitary to release hormones into the blood.
THE POSTERIOR LOBE
- Controlled by neurosecretory cells of the hypothalamus
- Cell bodies and dendrites of neurosecretory cells are located in the hypothalamus. Their axons extend down into the posterior pituitary.
- Cell bodies (of posterior pituitary neurosecretory cells) produce hormones (ADH, oxytocin) which travel down the axons of these cells into the posterior pituitary to be released directly into the bloodstream when needed.
The ANTERIOR LOBE
- Controlled by neurosecretory cells in the hypothalamus that are linked to it through portal systems of blood vessels
- Capillaries in the hypothalamus carry “releasing” and “release-inhibiting” hormones from the hypothalamus through a portal vein that branches into another network of capillaries in the anterior pituitary.
- The anterior pituitary releases its hormones into the bloodstream when “releasing” hormones are received from the hypothalamus and stops releasing its hormones when “release-inhibiting” hormones are received.
Know that TSH, FSH, LH, Prolactin, and Growth hormone are anterior pituitary hormones (and know the target cell(s) and function of each).
For growth hormone, know direct and indirect targets and effects/ actions.
TSH, FSH, LH, Prolactin, and Growth hormones are ANTERIOR pituitary hormones!
TSH (thyroid-stimulating hormone): Targets cells of the thyroid to make and secrete thyroxine
FSH (follicle-stimulating hormone): Targets cells of the gonads in males and females. In males, it causes meiotic divisions to produce spermatocytes. In females, it causes maturation of an oocyte.
LH (luteinizing hormone): Targets cells of the gonads in males and females. In males, it causes Leydig cells to make and secrete testosterone (for sperm production). In females, it causes ovulation of an oocyte.
Prolactin: Targets cells of the mammary glands causing them to grow and produce milk
Growth hormones: Targets cells throughout the body; stimulates mitosis
- acts directly on adipose tissue (reduces adipose cells)
- acts indirectly on muscles/ bones (increases mass/ growth) - does this by activating IGF (insulin growth factor) in liver; IGF increases bone growth and muscle mass
Know that ADH and oxytocin are posterior pituitary hormones (and know the target cell(s) and function of each).
ADH and oxytocin are POSTERIOR pituitary hormones!
ADH (Antidiuretic hormone): Targets cells of the kidney, increasing the amount of water that is reabsorbed into the blood
Oxytocin: Produced in neurosecretory cells in hypothalamus but stored in/ secreted from posterior pituitary; Targets cells of the uterine muscles and mammary glands, causing contractions (for birth) and milk secretion (note that nursing then causes oxytocin to be released to allow milk to be secreted too)
Explain the roles of the hypothalamus and thyroid gland in thermoregulation.
HYPOTHALAMUS
Body temperature is monitored and controlled by a “biological thermostat” in your brain called the hypothalamus (36 -38°C)
Hypothermia:
- Body temp is too LOW (metabolic reactions cannot occur – death below 32°C)
- Thermoreceptors in skin send signals to hypothalamus
- Hypothalamus releases chemical signals that trigger:
* Vasoconstriction (arterioles get smaller, blood is diverted to deep tissues/ organs, less heat loss)
* Shivering of skeletal muscle (generates heat)
* “Goosebumps” – raises hair follicles on skin (traps heat/ insulates against heat loss)
Hyperthermia:
- Body temp is too HIGH (tissues/ enzymes damaged, above 40°C is deadly)
- Thermoreceptors in skin send signals to hypothalamus
- Hypothalamus releases chemical signals that trigger:
* Vasodilation (arterioles get bigger, fill with blood, transfer heat to skin and out of body)
* Increased sweat gland activity (evaporative cooling)
THYROID GLAND
Thyroxin is a hormone secreted by the thyroid gland of the endocrine system in response to signals initially derived from the hypothalamus
Role = regulation of the body’s basal metabolic rate (the amount of energy a body uses AT REST)
- Thyroxin acts on almost all cells in the body, and causes an increase in the body’s metabolic rate/ increases body’s rate of energy release and use
- Causes an increase in carbohydrate and lipid metabolism (more oxidation of glucose and fatty acids)
- Causes increased oxygen consumption and the hydrolysis of ATP; thereby causing an increase in the body’s temperature
- In a regular person, if the body’s temperature drops, a release in thyroxin will stimulate heat production causing the body’s temperature to rise
Explain the role of thyroxin and the causes and consequences of thyroxin deficiency.
ROLE OF THYROXIN
Thyroxin is a hormone secreted by the thyroid gland of the endocrine system in response to signals initially derived from the hypothalamus
Role = regulation of the body’s basal metabolic rate (the amount of energy a body uses AT REST)
- Thyroxin acts on almost all cells in the body, and causes an increase in the body’s metabolic rate/ increases body’s rate of energy release and use
- Causes an increase in carbohydrate and lipid metabolism (more oxidation of glucose and fatty acids)
- Causes increased oxygen consumption and the hydrolysis of ATP; thereby causing an increase in the body’s temperature
- In a regular person, if the body’s temperature drops, a release in thyroxin will stimulate heat production causing the body’s temperature to rise
THYROXIN DEFICIENCY
Causes: Thyroxin contains iodine
Prolonged deficiency to iodine in the diet prevents the production of thyroxin (iodine is an essential nutrient)
Consequences: Iodine deficiency causes the thyroid gland to become enlarged (trying to compensate for iodine deficiency), resulting in a disease known as goitre
- If there is an insufficient (low) amount of thyroxin in the body (due to diet or deficiency in soils that food is grown in), hypothyroidism can occur
* Some of the symptoms are weight gain, loss of energy, feeling cold all the time, forgetfulness and depression, stunted growth, stunted mental development - If there is an excess amount of thyroxin in the body, hyperthyroidism can occur
* Some of the symptoms include excessive sweating/ hunger, hyperactivity, mood swings, rapid heart rate, difficulty sleeping, weight loss, muscle weakness/ tremors
Explain the role of melatonin in circadian rhythms.
- Produced in pineal gland of brain in response to changes in light.
- Function: Controls/regulates 24-hr circadian rhythm/ biological clock (the body’s physiological responses to the 24-hour day-night cycle of activity).
- Production/ amount of melatonin secreted is controlled by amount of light detected by the retina.
- Higher production/secretion in the dark vs little to no production in daytime (production is suppressed by bright light - mostly blue wavelengths).
- Amount of melatonin produced is proportional to night time duration as well (longer nights = more melatonin)
- Amount of melatonin secreted and timing of melatonin secretion becomes entrained in the body over prolonged periods of time
- Melatonin affects sleep-wake cycles and
seasonal reproduction - Promotes sleep in diurnal animals (like us)
- Promotes activity in nocturnal animals
- As we age, melatonin levels naturally decrease
Explain the causes and treatments of jet-lag.
Jet-lag is a physiological condition resulting from a change to the body’s normal circadian rhythm
CAUSES: The body’s inability to rapidly adjust to a new time zone (following extended air travel through multiple time zones)
- The pineal gland continues to secrete melatonin according to the “old” time zone schedule
CONSEQUENCES: Sleep disturbance and fatigue - symptoms include headaches, lethargy, irritability, and reduced cognitive function
TREATMENTS: Taking melatonin supplements (artificially increasing melatonin levels in the body) around the sleep time of the new time zone can help to alleviate symptoms of jet lag and help the body adjust to the new time zone faster
Compare and contrast hormonal and nervous communication (in the body).
SIMILARITIES
- Both use chemicals that bind to receptors (hormones/ neurotransmitters are both chemicals)
- Both used for COMMUNICATION between cells/ tissues/ organs in the body
- Both cause a response or change in target cells
- Both can stimulate or inhibit processes in target cells
- Both can work/ cause changes over long distances (between widely separated parts of body)
- Both use feedback mechanisms to maintain homeostasis
- Both under (overall) control of brain/ CNS
DIFFERENCES (Hormones / Nerves)
- Chemical (messenger) / Electrical (nerve impulse)
- Messenger (hormones) transported in blood / Signal transported by neurons
- Slower / Faster
- Carried throughout body / Carried to single/ specific cell/ muscle fibre
- Wide range of organs/ tissues affected / Only muscles/ glands receive signals
- Long-term/ persistent response (usually) / Short-term/ short-lived response
