hormone basics Flashcards
describe the role of the nervous system
to translate or transduce external stimuli into neural signals that bring change to the connected system
list some key aspects of the nervous system
Afferent neurons, Spinal cord, Effrent neurons, Target tissues, Hypothalamus,
what is an efferent neuron
Neurons which are nerves that travel away from the spinal cord towards target tissue
What is an afferent neuron
Sensory neurons taking signals towards the spinal cord
what are the two reflexes that control the neuroendocrine system
Simple neural reflex
neuroendocrine reflex
describe the simple neural reflex arch and name two examples
senory pick up by neurons -> signal sent to spinal cord via afferent neurons -> efferent neurons send back signal to target tissue with adjustment to response to stimuli.
ejaculation (touch stimuli and muscle contractions response)
scrotum tempreture (tempretur stimuli, contraction elevation of testes in response)
what is a neurotransmitter
substance/ small molecule released from the terminals of nerves that cause other nerves to fire or cause contraction of smooth muscle.
describe the neuroendocrine reflex and give an example
sensory neruon (affrenet) send signal to spine -> signal travels to hypothalamus (efferent) -> hypothalamus releases moleculs into blood (neurohormones)
what is an inhibitory neuron
Inhibitory neurons stop / prevent actions caused by other excitatory neurons.
what is an excitatory neuron
Neurons which increase the probability of postsynaptic action potential (firing nerves)
what does the probabilty of postsynaptic neruon firing relay on?
ratio of presynaptic inhibition to presynaptic excitation.
what is the hypothalamus
The hypothalamus is a complex portion of the brain. It is made from clusters of nerve cell bodies called hypothalamic nuclei, each one having a specific name and function.
where is the surge center and what does it produce
in the hypothalamus, it produces Gonadotropin Releasing Hormone (GnRH)
what allows for neuron communication in the hypothalamus and what is it made of?
via the anterior lobe of the pituitary using a specialized system called the hypothalamo - hypophyseal portal system. This system is a capillary network connected to terminal nerve endings.
how does the hypothalamo - hypophyseal portal system function?
Terminal boutons release neuropeptides which enter the blood from the superior hypophyseal artery.
The hypothalamic-hypophyseal portal is important as it allows small quantities of releasing hormones to act directly on the anterior lobe of the pituitary before the GnRH becomes diluted by the systemic circulation
does the prosterior pituitary lobe have a portal system?
No, instead the neurohormones are deposited straight into the capillaries.
what is a hormone
substance produced by a gland that acts on a REMOTE tissue, these can include changes to metabolism, synthetic activity, and secretory activity.
what is a luteolytic hormone
Hormones which cause destruction to the corpus luteum (PGF2a) prostaglandin F2a
list endocrine glands important to the reproductinve system (obviously)
Anterior pituitary gland
Posterior pituitary gland
Uterine
Placenta
Ovaries
Testes
Thyroid gland
Adrenal cortex
Endocrine gland
what hormone does the hypothalamus mainly produce
Gonadotropin releasing hormone (GnRH)
what does the Anterior pituitary gland release?
Follicle Stimulating hormone (FSH), Luteinizing hormone (LH), prolactin, somatropin (growth hormone)
what does the posterior pituitary gland release
oxytocin
what hormone does the uterine release
prostaglandin F2a (PGF2a)
what hormone does th placenta release
progesterone, estrogen (estradiol) , equine chorionic gonadotropin (eCG), human chorionic gonadotropin (hCG), placental lactogen, Acitvin
what hormones do the ovaries produce
estrogen (estradiol) , progesterone, inhibin, oxytocin, relaxin and some testosterone
What hormone do the testes produce
testosterone, other androgens and estrogen
do hormone does the thyroid gland produce
thyroxine
what hormone dose the adrenal cortex produce
arsenal corticoids
what do the endocrin glands produce
pheromones and hormones
list the types of classification methods
source, mode of action, biochemically
list the diffrent types of sources for hormones and their role
Hypothalamic - causes release of hormones in the anterior/ posterior pituitary, from hypothalamus
Pituitary - releases into the circulatory system from either pituitary gland
Gonadal - released from the gonads they effect hypothalamic function and development of secondary sex characteristics
example of a hypothamalic hormone
Gonadotropin Releasing Hormone (GnRH)
example of a gonadal hormone
Female - estrogen, progesterone, inhibin, oxytocin, relaxin and some testosterone
Male - testosterone, androgen, inhibin and estrogen
example of a pituitary hormone
Follicle Stimulating hormone (FSH),
Luteinizing hormone (LH) and prolactin - all from the anterior lobe
Oxytocin - from the posterior lobe
what is hCG and eCG and describe their role and source
equine chorionic gonadotropin (eCG), human chorionic gonadotropin (hCG).
hCG and eCG are produced by the early embryo in the chorion (one of the membranes surronding embryo which is apart of the placenta) to stimulate the maternal ovary.
list the diffrent types of mode of actions for hormones and their role.
neurohormones - synthesized by neurons and released into blood, they travel to target tissue and can effect any number
Releasing hormones - synthesized by neurons in the hypothalamus they cause the release of other hormones
Gonadotrophins - Released by the gonadotroph cells in the anterior pituitary, they stimulate the gonads
example of neurohormone
Oxytocin from the posterior pituitary glandex
example of releasing hormone
Gonadotropin Releasing Hormone - GnRH which releases Follicle stimulation hormone (FSH) and Lutenizing hormone (LH).
example of gonadotropins
Follicle stimulating hormone (FSH)
Luteinizing hormone (LH) - causes ovulation and stimulates corpus luteum into producing progesterone OR stimulates testosterone production in males
list the diffrent types of biochemical hormones and their description.
Peptides - small, with few amino acids joined via peptide bonds
Glycoproteins - Polypeptide hormones that contain carbohydrate moieties. some have alph and beta subunits when they are connected beside on another.
steroids all have a molecular nucleus and are synthesized from cholesterol via enzymatic conversions
Prostaglandins - lipids of 20 carbon unsaturated hydroxy fatty acids, they are destoryed in the blood stream withing one cycle (30 sec)
example of peptide hormone
Gonadotropin Releasing Hormone - GnRH
example of glycoproteins
Anterior lobe producing FSH, TSH and LH, all have the same but subunit A but subunit B is unique for each hormone.
Inhibin has one type of Alpha and two possible Beta
Activin has two Beta subunits
Prolactin no subunits,
what is the molecular nucleus in steroids
made from four rings it is
cyclypentanoperhydrophenanthrenen
Example of steroids
progesterone , estrogen and testosterone (androgens)
example of prostaglandins
Prostaglandin E2 (PGE2) - lowers BP and prostaglandin F2 (PGF2a) increases blood pressure. They both partially control ovulation.
PGF2a was found to cause luteolysis
describe pheromones
Substances secreted outside the body, generally they are volatiles and directed at the olfactory system by members of the same species.
Pheromones cause specific behavioral or physiological reactions in species. These can be indemnification females in estrus or similar.
how is hormone secretion controlled
positive and negative fee back loops
define positive and neagtive feedback loops
Positive feedback: stimulates the GnRH neurons
Negative feedback: suppress the GnRH neurons
example of positive feedback loop
When estradiol (estrogen) reaches the threshold level the surge center in the hypothalamus stimulates GnRH neurons and increases the development of LH that stimulates ovulation.
example of negative feesback loop
Progesterone causes highly negative feedback in the hypothalamus, causing only basal levels of secretions of GnRH. This prevents significant follicular development as less FSH and LH is secreted; inhibiting the period cycle while progesterone is high. (consider the pill)
how is hormone strength determined
pattern and duration of secretion, half life, receptor density and receptor hormone affinity.
what are the three types of secretion patterns
Episodic - generally hormones with nervous control, they have large peaks.
Basal - hormone remain low but with fluctuations in low pulses
Sustained - remains elevated in a steady manner for a long period of time (steroids)
what is a hormone potency dependent on
the receptor density and receptor hormone affinity.
what is a hormone agonist which is analog
sythetic hormone which increases potentcy, likey due to a higher affinity
what is a hormone antagonist which is analog
synthetic hormone with a greater affinity but a weaker effect than the natural hormone.
describe the receptor for protein hormones
Protein hormone receptors are located on the plasma membrane of the target cell, it has three regions called the receptor domains (extracellular domain, transmembrane domain and intracellular domain.
list the step in the protien receptors
1 - hormone receptor binding
2 - adenylate cyclase activation
3 - protein kinase activation
4 - synthesis of new product
list the step in steroid receptors
1- steroid transport
2- movement through the cell membrane
3 - binding of steroid to nuclear receptor
4 - mRNA synthesis and protein synthesis
