Homeostasis, Endocrine System, and Human Reproductive Cycles Flashcards
The extracellular component of G-protein coupled receptors is a ____.
ligand-binding site
The intracellular component of G-protein coupled receptors is a ____.
portion that binds to G protein
What happens when a G protein-coupled receptor is activated?
it associates with a G protein
G protein-coupled receptors are able to transmit signals from ____ the cell –> ____ the cell.
outside –> inside
G protein-coupled receptors initiate a long-term/short-term response.
short-term
What are the four steps in the G protein-coupled receptor pathway?
- receptor activation
- signal amplification
- cellular response
- signal termination
When the G protein is inactive, it is bound to ____
GDP
When the G protein is active, it is bound to ____
GTP
releases GDP to bind GTP
What subunit of the G protein binds to GTP?
alpha subunit
What steps occur during signal amplification of the adrenaline pathway (after receptor activation)?
- GTP-bound subunit binds to enzyme adenylyl cyclase
- adenylyl cyclase converts ATP into cAMP
- cAMP binds to and activates protein kinase A
What is a second messenger?
a signaling molecule that relays info to the next target in the signal transduction pathway
True or False:
A G protein-coupled pathway can only be terminated at the receptor.
False
can be terminated at either the receptor or G protein
How is the G protein signal terminated at the receptor?
binding affinity of signaling molecule decreases, which leads to it dissociating from the receptor
How is the G protein signal terminated at the G protein?
active GTP bound subunit turns itself off by converting GTP –> GDP
What is homeostasis?
the active regulation and maintenance of a stable internal physiological state in the face of a changing external environment
What are the four components of a negative feedback loop?
- stimulus
- sensor
- effector
- response
What does a negative feedback loop do?
a process in which the output or produce of a pathway opposes the initial stimulus so that homeostasis is maintained
What is the set point in a feedback loop?
a steady-state value in homeostatic regulation
i.e. temperature, levels of a chemical
What is a hormone?
a chemical messenger that regulates the organism’s physiological response to the enviornment and helps maintain stable physiological conditions
What are neurosecretory cells?
neurons in the hypothalamus and posterior pituitary gland that secrete hormones into the bloodstream
What are neurohormones?
hormones released by neurosecretory cells
What hormone is secreted in a negative feedback loop in which high blood glucose is the stimulus?
insulin
What is the function of insulin?
body cells take up glucose and store it as glycogen
What hormone is secreted in a negative feedback loop in which low blood glucose is the stimulus?
glucagon
What is the function of glucagon?
stimulates the breakdown of glycogen into glucose
What is the sensor in blood glucose loops?
pancreas
What are the effectors in blood glucose loops?
- insulin/glucagon
- body cells
- muscle and liver
What is a stimulus in a negative feedback loop?
a change in level from homeostatic set point
What is the sensor in a negative feedback loop?
endocrine organ that detects a stimuli and initiates release of a signaling molecule
What is the effector in a negative feedback loop?
a hormone/other bodily component that acts to exhibit a response
What is the response in a negative feedback loop?
a response that opposes the initial stimulus and returns the body back to set point
What happens in a positive feedback loop?
a stimulus causes a response in the same direction as the initial stimulus
How does a positive feedback loop work?
more hormone is released, which escalates the response
Where are the receptors of hydrophilic hormones located?
cell surface
Where are the receptors of hydrophobic hormones located?
inside the cell
What is the structure of peptide hormones?
short chain of amino acids
What is the structure of amine hormones?
single aromatic amino acid
What is the pituitary gland?
the central regulating gland of the endocrine system that releases hormones to coordinate the action of the other endocrine organs
How does the anterior pituitary gland communicate with the hypothalamus?
neurosecretory cells in hypothalamus secrete hormones into blood vessels that travel to the anterior pituitary
How does the posterior pituitary gland communicate with the hypothalamus?
communicates without the release of hormones
neurosecretory cells extend axons into the posterior pituitary
What are tropic hormones?
hormones that control the release of other hormones
What is the difference between hormones and paracrine signals?
hormones enter circulation and target distant cells
paracrine signals bind to receptors and target local cells
What are pheromones?
water or airborne chemical compounds released by animals into the environment that signals and influences the behavior of other members of their spaces
What are the gonads of the male reproductive system?
testes
What gamete is produced in the male reproductive system?
sperm
What sex hormones are involved in the male reproductive system?
testosterone and estrogen
What are the target cells of the sex hormones in the male reproductive system?
Leydig cells and Sertoli cells
What do Leydig cells do?
secrete testosterone and estrogen
What do Sertoli cells do?
stimulate sperm production
How are gametes released in the male reproductive system?
ejaculation
What are the gonads in the female reproductive system?
ovaries
What gametes are produced in the female reproductive system?
oocytes
What sex hormones are involved in the female reproductive system?
estrogen, progesterone, and testosterone
What are the target cells of sex hormones in the female reproductive system?
granulosa cells, hypothalamus, and anterior pituitary
How are gametes released in the female reproductive system?
menstrual cycle (ovulation)
What does GnRH do?
stimulates anterior pituitary to secrete LH and FSH
How do GnRH levels change during the menstrual cycle?
follicular ↑
ovulation ↓
luteal ↓
How do FSH levels change during the menstrual cycle?
follicular ↓
ovulation ↑
luteal ↓
What does FSH do?
stimulates estrogen and progesterone secretion
What does LH do?
stimulates the secretion of estrogen and progesterone
How do LH levels change during the menstrual cycle?
follicular ↓
ovulation ↑↑↑
luteal ↓
What does estradiol do?
acts on oocytes to begin to mature each month; causes the uterine lining to thicken
How do estradiol levels change during the menstrual cycle?
follicular ↓
ovulation ↑
luteal ↓
What does progesterone do?
helps maintain the thickened uterine lining in preparation for the possible implantation of a fertilized egg
How do progesterone levels change during the menstrual cycle?
follicular ↓
ovulation ↓
luteal ↑
What happens during the follicular phase?
stimulates the production of follicles on the ovary to mature into an egg
What happens during the ovulation phase?
a mature egg is released from the ovary
What happens during the luteal phase?
the uterus prepares for pregnancy by causing the uterine lining to thicken
What happens during the menstruation phase?
the uterine lining sheds
True or False:
In certain situations, the body is able to change its set point.
True
How is the set point changed when you have a fever?
pyrogens sense that your body is colder than it really is, so it sends a message to your brain to increase the set point, leading to you feeling hotter than normal
When you are developing a fever and your body temperature set point increases, you may feel…
feel cold and shiver
When your body is recovering from a fever, blood vessels in the skin dilate/constrict to release/retain heat.
As a result, your skin appears ____.
dilate; release
flushed
When calcium levels are too high, the thyroid gland increases/decreases production of calcitonin.
increases
What is the function of calcitonin?
deposits more calcium in the bone
When blood calcium levels decline:
Thyroid gland produces ____ to increase/decrease bone calcium levels.
calcitonin; increase
When blood calcium levels rise:
Parathyroid gland produces ____ to increase/decrease bone calcium levels.
PTH; decrease
How are T3 and T4 produced?
thyroid takes in dietary iodide, which reacts with thyroglobulin to produce T3 and T4
How do enlarged thyroids occur?
accumulation of thyroglobulin due to no dietary iodide intake, which prevents thyroglobulin from synthesizing to T3 and T4
Feedback inhibition of GnRH ____ follicular development.
inhibits
