neuroendocrinology. hormones endocrine hormones secreted directly into the blood controlled by...
Post on 15-Jan-2016
229 Views
Preview:
TRANSCRIPT
Neuroendocrinology
Hormones
Endocrine hormonesSecreted directly into the bloodControlled by pituitary (master gland)and hypothalamus
Exocrine HormonesSecreted into ducts
Not controlled by pituitary glandor hypothalamus (e.g., gut hormones)
Hormones
Neurotransmitters
long latency, long duration of effect (mins/days)
short latency, short duration of effect (msec)
delivered via blood
released directly onto target cells
diffuse actions
specific actions
released from endocrine cells
released from neurons
This distinction has become blurred; e.g.peptide neurotransmitters/neuromodulators,monoamines, etc.
Pituitary Gland(Hypophysis)
Anterior Pituitary(Adenohypophysis)
Posterior Pituitary(Neurohypophysis)
Endocrine Hormones`
Neurohypophysial hormonesOxytocinVasopressin
Adenohypophysial hormonesDirect Actions
ProlactinMelanocyte-stimulating hormone (MSH)
Somatotrophin (growth hormone; GH)
Indirect actions
Thyrotrophin (TSH)Corticotrophin (ACTH)
GonadotrophinsLuteinizing Hormone (LH)
Follicle-stimulating hormone (FSH)
Hypothalamus
Adenohypophysis
Endocrine Gland
Target tissues
Control of Adenohypophysial Hormones with Indirect
Actions
IndirectLoop
ShortLoop
DirectLoop
Releasing Factor
Trophic hormone
Endocrinehormone
All loops are negative feedback loops. Increases in the amount of the substances monitored reduces further secretion of those substances.
neural inputs
Indirect ActingACTH, TSH, LH, FSH
Hypothalamus
Adenohypophysis
Target tissues
Control of AdenohypophysialHormones withDirect Actions
IndirectLoop
Inhibitingfactor
DirectLoop
Releasing Factor
All loops are negative feedback loops. Increases in the amount of the substances monitored reduces further secretion of those substances.
neural inputs
Direct ActingGH, MSH, Prolactin
Direct ActingHormone
Endocrine HormonesAdenohypophysial hormones
Direct ActionsSomatotrophin (growth hormone; GH)Growth hormone releasing hormone (GHRH) somatotrophin (GH) somatic tissues
promotes growth by stimulating proteins synthesis of virtually all tissues
GH release inhibited by somatostatin
Endocrine HormonesAdenohypophysial hormones
Direct Actions
ProlactinSomatotrophin (growth hormone; GH)
prolactin release inhibited by prolactin inhibiting factor (PIF)
PIF secretion inhibited by stimulation of nipples
stimulates milk production
Prolactin releasing factorprolactinmammaries
Endocrine HormonesAdenohypophysial hormones
Direct Actions
ProlactinMelanocyte-stimulating hormone (MSH)
Somatotrophin (growth hormone; GH)
MSH releasing factor melanocyte-stimulating hormonemelanocytes
stimulates melanin synthesisin melanocytes
Hypothalamus
Adenohypophysis
Endocrine Gland
Target tissues
Control ofAdrenocortical Hormones
IndirectLoop
ShortLoop
DirectLoop
Corticotrophin(ACTH)
Cortisol andAldosterone
neural inputs
CRF
Endocrine HormonesAdenohypophysial hormones
Direct Actions
ProlactinMelanocyte-stimulating hormone (MSH)
Somatotrophin (growth hormone; GH)
Indirect actionsCorticotrophin (ACTH) regulates stress hormones and nutrient utilization (glucocorticoids) and water/mineral balance (mineralocorticoids)
Endocrine HormonesAdenohypophysial hormones
Direct Actions
ProlactinMelanocyte-stimulating hormone (MSH)
Somatotrophin (growth hormone; GH)
Indirect actionsCorticotrophin (ACTH)
Corticotrophin releasing factor (CRF) ===> corticotrophin ===> cortisol, aldosterone ===> tissues
cortisol inhibits protein synthesisstimulates gluconeogenesis(synthesis of glucose from proteins)inhibits conversion of carbohydrates to fats
aldosterone regulates electrolytes,especially sodium
principal stress hormonephysiological stress—challenges to homeostasispsychological stress—perceived challenges limbic system participation
Corticotrophin
Controls secretions from adrenal cortexad = on, renal = kidney, so adrenal = on the kidney
the adrenal gland is really two glands in one cortex = bark, medulla = core medulla is a modified sympathetic ganglion cortex is an endocrine gland
Activity of both medulla and cortex arestress-related
What is stress?
What is stress?It is “a real or interpreted threatto the physiological orpsychological integrity of anindividual that results inphysiological and/or behavioralresponses. In biomedicine,stress often refers to situationsin which adrenal glucocorticoidsand catecholamines are elevated because of an experience.”
McEwen, B. (2000) In G. Fink(Ed.) Encyclopedia of Stress,Vol. 3. San Diego: Academic Press.
What is stress?Is it a demanding stimulus or situation?
“I’m under a lot of stress.”
Is it a subjective experience?“I’m feeling stressed out.”depression
Is it a physiological challenge?hunger, thirst, fatigue
Is it an endocrine response?circulating stress hormones
Two types of stress1. Systemic stress
physiological threat
2. Processive stress potential or eventual threat
In adults, responses to processive, but not systemic,stress is blocked by lesions ofthe hippocampus
Systemic stress is also referred to asphysiological stress, and processivestress is oten referred to as psychological stress
Endocrine HormonesAdenohypophysial hormones
Direct Actions
ProlactinMelanocyte-stimulating hormone (MSH)
Somatotrophin (growth hormone; GH)
Indirect actions
Thyrotrophin (TSH)Corticotrophin (ACTH)
Thyrotrophin releasing factor (TRF or TRH) thyrotrophin (TSH) thyroid gland thyroxine tissues
regulates development
regulates metabolic rate in adulthood
Hypothalamus
Adenohypophysis
Thyroid Gland
Target tissues
Control ofThyroid Hormones
IndirectLoop
ShortLoop
DirectLoop
TRF (TRH)
TSH
Thyroxine (T4)
neural inputs
Thyroid Hormones asRegulators of Development
Stimulation of Metamorphosisin Amphibians
iin brain, thyroid hormones stimulatesecondary neurogenesis of cerebellarPurkinje cells, development of optic tectum
e.g. loss of gills, septation of lungs remodeling of gastrointestinal tract loss of tail, growth of limbs
Thus, thyroxine stimulates both cell loss (apoptosis) and cell proliferation (mitosis) in different populations
Thyroid Hormones asRegulators of Development
Thus, thyroxine stimulates both cell loss (apoptosis) and cell proliferation (mitosis) in different populations.
This role contrasts with that of growthhormone.
In the absence of growth hormone, tadpoles still undergo metamorphosisbut have reduced size.
In the absence of thyroxine, tadpolescontinue to grow but fail to transform.
Analogous Effectsare seen in mammals
In mammals, growth hormone deficiencyresults in dwarfism; thyroid hormonedeficiency results in cretinism.
Dwarves reach developmental milestonesat the normal time; they are simply of shorter stature.
Hypothyroid individuals are also small,but more profoundly, developmentalmilestones are greatly delayed.
15-20 years old,Congo-Kinshasa
Endocrine HormonesAdenohypophysial hormones
Direct Actions
ProlactinMelanocyte-stimulating hormone (MSH)
Somatotrophin (growth hormone; GH)
Indirect actions
Thyrotrophin (TSH)Corticotrophin (ACTH)
GonadotrophinsGonadotrophin releasing hormone (GnRH) orLeuteinizing hormone releasing hormone (LHRH) luteinizing hormone (LH) and
follicle stimulating hormone (FSH) gonads (ovaries or testes) estrogen and progesterone
or androgens tissues
organizational effectsactivational effects
Definitions of Sex
Genetic (XX vs XY
Gonadal (ovaries vs testes)
Hormonal (cyclic vs constant releaseMorphological (clitoris, labia vs penis, scrotum)
Behavioral (gender role behavior)
Identity (what you consider yourself to be)
Hypothalamus
Adenohypophysis
Testes (♂)Ovaries (♀)
Target tissues
(GnRH)
Luteinizing Hormone (LH)Follicle Stimulating Hormone (FSH)
Testosterone (♂)Estrogen/Progesterone (♀)
Control ofSex Hormones
neural inputs
Sexual DimorphismsPhenotypic differencesbetween males and females
They can be:anatomicalphysiologicalbehavioralcognitive
They can be:qualitativequantitative
Effects of Sex Hormones
• Organizational Effects• structural• sensitive period• irreversible• masculinization/defeminization
• Activational Effects• act on existing structure• no sensitive period• reversible
Bipotential tissues—those that can differentiateinto tissues typical of either sex
Bipotential tissues: Undifferentiated tissuethat can differentiate into either a male orfemale form.
Sexual Dimophisms: Structures, functionsor behaviors that differ qualitatively or quantitatively between the sexes.
Castrate male hamster at birth
Prototypical Experiment(Males)
(before period of brain differentiation)
Test in adulthood
place with receptive female
inject with testosterone
male typical behavior low
mounting, intromission (ejaculation not possible)
female-typical behavior high
darting, ear-wiggling, lordosis
place with male
inject with estrogen and progesterone
Neuter female hamster at birth andinject with testosterone
Prototypical Experiment(Females)
(before period of brain differentiation)
Test in adulthood
place with receptive femaleinject with testosterone
male typical behavior high (mounting)
female-typical behavior low (ear-wiggling, darting, lordosis)
place with male
inject with estrogen and progesterone
Differentiation of the Brain
MasculinizationInduction of male characteristics paradoxically, dependent on estradiol
DefeminizationSuppression of female characteristics
Two processes both are dependent of fetal androgens
estrodiol
aromatase 5-alphareductase
cholesterol
DHT
Why aren’t all femalesmasculinized?
α-fetoproteinbinds to estradiol extracellularyand prevents entry into cell
♁♂
medial preoptic area (MPOA) = “the” sexually dimorphic nucleus (SDN)
Sexual Differentiation
Female is the “default sex;” no sex hormones are required for normal organization of the brain or peripheral tissues.
Male development requires thattestosterone be secreted from the fetal testes during a sensitive period of development. Masculinization and defeminization of the brain requires theconversion of testosterone to estradiol byneurons of the brain. Masculinization ofperipheral tissues requires conversion oftestosterone to dihydrotestosterone (DHT).
Sexual DimorphismsPhenotypic differencesbetween males and females
They can be:anatomicalphysiologicalbehavioralcognitive
They can be:qualitativequantitiave
estrodiol
aromatase 5-alphareductase
cholesterol
DHT
XX Congenital Adrenal Hyperplasia (CAH)
XX Congenital Adrenal Hyperplasia (CAH)
estrodiol
aromatase 5-alphareductase
cholesterol
DHT
Female Spotted Hyena
estrodiol
aromatase 5-alphareductase
cholesterol
DHT
estrodiol
aromatase 5-alphareductase
cholesterol
DHT
Endocrine HormonesAdenohypophysial hormones
Direct Actions
ProlactinMelanocyte-stimulating hormone (MSH)
Somatotrophin (growth hormone; GH)
Indirect actions
Thyrotrophin (TSH)Corticotrophin (ACTH)
Gonadotrophins
LH and FSH stimulate ovulation in females and spermatogenesis in males
Gonadotrophin releasing hormone (GnRH) orLeuteinizing hormone releasing hormone (LHRH) luteinizing hormone (LH) and
follicle stimulating hormone (FSH) gonads (ovaries or testes) estrogen and progesterone
or androgens tissues
Testosterone masculinizes and defeminizes fetus
Produce secondary sex characteristics andactivate gender-typical behavior
1. LH and FSH stimulate follicular development
2. Developing follicles secrete estrodiol
3. Increasing estrodiol stimulates GnRH release
4. LH surge stimulates ovulatoin
5. Luteinized cells secrete estradiol, progesterone
6. Luteinized cells degenerate.
Gladue, Green & Hellman,(1983), Science, 225, 1496-1499.
♁♂
medial preoptic area (MPOA) = “the” sexually dimorphic nucleus (SDN)
Correspondto MPOA of rodents
Endocrine Hormones
Neurohypophysial hormonesOxytocin
Adenohypophysial hormonesDirect Actions
ProlactinMelanocyte-stimulating hormone (MSH)
Somatotrophin (growth hormone; GH)
Indirect actions
Thyrotrophin (TSH)Corticotrophin (ACTH)
GonadotrophinsLuteinizing Hormone (LH)
Follicle-stimulating hormone (FSH)
stimulation of cervix, nipples ===> oxytocin
primes maternal behavior
stimulates milk ejection
Endocrine Hormones
Neurohypophysial hormonesOxytocin
Vasopressin
Adenohypophysial hormonesDirect Actions
ProlactinMelanocyte-stimulating hormone (MSH)
Somatotrophin (growth hormone; GH)
Indirect actions
Thyrotrophin (TSH)Corticotrophin (ACTH)
GonadotrophinsLuteinizing Hormone (LH)
Follicle-stimulating hormone (FSH)
low blood pressure vasopressin (ADH)
kidneys retain more water
Endocrine Hormones
Neurohypophysial hormonesOxytocinVasopressin
Adenohypophysial hormonesDirect Actions
ProlactinMelanocyte-stimulating hormone (MSH)
Somatotrophin (growth hormone; GH)
Indirect actions
Thyrotrophin (TSH)Corticotrophin (ACTH)
GonadotrophinsLuteinizing Hormone (LH)
Follicle-stimulating hormone (FSH)
top related