H_P (hypothalamic pituitary axis - cell bio) Flashcards
LEARNING OBJECTIVES
- List the endocrine glands regulated by the Hypothalamic-Pituitary Axis
- Explain the specific structures and characteristics of the anterior and the posterior pituitary (embryogenesis)
- List and understand the functions of the hormones produced by the hypothalamus and pituitary gland
1st slide: Hypothalamus -> (corticotropin releasing hormone CRH) -> Anterior pituitary -> (adrenocorticotropic hormone aka ACTH) -> Adrenal cortex -> cortisol aka CORT
The HYPOTHALAMUS is a place of ? and ? connection
Composed of more than ? nuclei (groups of neurons) and areas that regulate:
? SYSTEM (sympathetic and parasympathetic)
? SYSTEM
? SYSTEM
(Instintic and emotions: fear, aggression, memory, reflex memories related to smell, learning, feeding behavior, pleasure, sex, care for offspring, dominance)
go through labelings on the brain
The HYPOTHALAMUS is a place of neurological and endocrine connection
Composed of more than 12 nuclei (groups of neurons) and areas that regulate:
AUTONOMIC SYSTEM (sympathetic and parasympathetic)
ENDOCRINE SYSTEM
LIMBIC SYSTEM
(Instintic and emotions: fear, aggression, memory, reflex memories related to smell, learning, feeding behavior, pleasure, sex, care for offspring, dominance)
go through labelings for the brain!! - don’t confuse pituitary gland w pineal gland; pineal located in the center while pituitary more on the left lateral side
- don’t forget “diencephalon”
When regulating the endocrine system, the hypothalamus works in close connection with the
? gland (Hypophysis)
HYPOTHALAMIC-PITUITARY AXIS
When regulating the endocrine system, the hypothalamus works in close connection with the
PITUITARY gland (Hypophysis)
HYPOTHALAMIC-PITUITARY AXIS
The hypothalamus and pituitary gland function in a coordinated way to affect the ? system regulating:
- ?
- ? GLANDS
- ? GLANDS
- ?
- ? PRODUCTION/EJECTION
- ?
The hypothalamus and pituitary gland function in a coordinated way to affect the endocrine system regulating:
- THYROID
- ADRENAL GLANDS
- REPRODUCTIVE GLANDS
- GROWTH
- MILK PRODUCTION/EJECTION
- OSMOREGULATION
The HYPOTHALAMUS secretes ? and ? hormones that control ? ? secretion
- ?-releasing hormone (TRH)
- ?-releasing hormone (CRH)
- ?-releasing hormone (GnRH)
- ? hormone-releasing hormone (GHRH)
- Growth hormone ? hormone (Somatostatin/GHIH)
- ? inhibiting hormone (Dopamine/PIH)
The HYPOTHALAMUS secretes stimulatory and inhibitory hormones that control anterior pituitary secretion
- Thyrotropin-releasing hormone (TRH)
- corticotropin-releasing hormone (CRH)
- gonadotropin-releasing hormone (GnRH)
- growth hormone-releasing hormone (GHRH)
- Growth hormone inhibiting hormone (Somatostatin/GHIH)
- prolactin inhibiting hormone (Dopamine/PIH)
HYPOTHALAMUS
Special neurons synthesize and secrete the hypothalamic-releasing and inhibitory hormones
o Neurons originate in various parts of the ?
o The endings of these fibers are different from most nerve endings in the CNS
They secrete ? into the ECF (extracellular fluid)
Hormones are immediately absorbed into the:
** Hypothalamic-Hypophysial Portal System → carry hormones directly to the sinuses of the ? gland **
HYPOTHALAMUS
Special neurons synthesize and secrete the hypothalamic-releasing and inhibitory hormones
o Neurons originate in various parts of the hypothalamus
o The endings of these fibers are different from most nerve endings in the CNS
They secrete hormones into the ECF (extracellular fluid)
Hormones are immediately absorbed into the:
** Hypothalamic-Hypophysial Portal System → carry hormones directly to the sinuses of the anterior pituitary gland **
The hypothalamic-hypophyseal portal system
is a microcirculation system of blood vessels at the ? of the brain, connecting the hypothalamus with the anterior pituitary
Its main function is to quickly transport and exchange ? between the hypothalamus and anterior pituitary gland.
The ? in the portal system are ? (have many small channels with high or low? vascular permeability) which allows a ? exchange between the hypothalamus and the pituitary.
The hypothalamic-hypophyseal portal system
is a microcirculation system of blood vessels at the base of the brain, connecting the hypothalamus with the anterior pituitary
Its main function is to quickly transport and exchange hormones between the hypothalamus and anterior pituitary gland.
The capillaries in the portal system are fenestrated (have many small channels with high vascular permeability) which allows a rapid exchange between the hypothalamus and the pituitary.
anterior pituitary: ADENOHYPOPHYSIS
posterior pituitary: NEUROPOPHYSIS
pic:
neurons synthesizing trophic hormones release them into capillaries of the portal system
portal vessels (present in between) carry the trophic hormones directly to the anterior pituitary
endocrine cells release their hormones into the second set of capillaries for distribution to the rest of the body.
neurons synthesizing posterior pituitary hormones (Green ones)
HYPOPHYSIS
The HYPOPHYSIS is a small gland located in the ? ? (bony cavity at the ? of the brain)
Connected to the hypothalamus by the ? stalk (infundibulum)
Divided into 2 distinct parts:
1. Anterior Pituitary (?)
2. Posterior Pituitary (?)
HYPOPHYSIS
The HYPOPHYSIS is a small gland located in the “sella turcica” (bony cavity at the ? of the brain)
Connected to the hypothalamus by the pituitary stalk (infundibulum)
Divided into 2 distinct parts:
1. Anterior Pituitary (ADENOHYPOPHYSES)
2. Posterior Pituitary (NEUROPHYPOPHYSES)
ANTERIOR PITUITARY (ADENOHYPOPHYSIS)
The anterior hypophysis originates from the ? pouch (embryonic invagination of the pharyngeal epithelium)
o Contains #? major types of cells with epithelioid nature
Each cell type produces a different type of hormone
Adenohypophysis 5 major types of cells:
- ? – produce growth hormone (GH) – about 50%
- ? – produce adrenocorticotropin (ACTH) – 15 to 20%
- ? – produce prolactin - 15 to 20%
- ? – produce thyroid-stimulating hormone (TSH) - 5%
- ? – gonadotropic hormones (LH and FSH) – 10 to 15% * Luteinizing hormone and Follicle-stimulating hormone
Adenohypophysis 5 major types of cells:
(don’t memorize the %s below)
- SOMATOTROPES – produce growth hormone (GH) – about 50%
- CORTICOTROPES – produce adrenocorticotropin (ACTH) – 15 to 20%
- LACTOTROPES – produce prolactin - 15 to 20%
- THYROTOPES – produce thyroid-stimulating hormone (TSH) - 5%
- GONADOTROPES – gonadotropic hormones (LH and FSH) – 10 to 15% * Luteinizing hormone and Follicle-stimulating hormone
ANTERIOR PITUITARY (ADENOHYPOPHYSIS)
The ? of the anterior pituitary play a major role in the control of metabolic functions throughout the body
GROWTH HORMONES (GH) – promote growth of the entire body by affecting protein formation, cell multiplication and cell ?
? (adrenocorticotropic hormone ACTH) – controls secretion of some of the adrenocortical hormones, which affect metabolism of ** ?, ? and ? **
? (? stimulating hormone TSH) controls the secretion rate of * ? (T4) and ? (T3) * by the thyroid gland, and these hormones control the rates of most ? chemical reactions in the body
PROLACTIN (PRL)– promotes ? gland development and ? production
GONADOTROPINS (FSH and LH) – control growth of the ? and ?, as well as their hormonal and ? activities
ANTERIOR PITUITARY (ADENOHYPOPHYSIS) - GCTPC
The peptide hormones of anterior pituitary plays a major role in the control of metabolic functions throughout the body
GROWTH HORMONES (GH) – promote the growth of the entire body by affecting protein formation, cell multiplication and cell differentiation
CORTICOTRPOIN (adrenocorticotropic hormone ACTH) – controls secretion of some of the adrenocortical hormones, which affect metabolism of ** glucose, proteins, and fats **
THYROTROPIN (thyroid stimulating hormone TSH) controls the secretion rate of * thyroxine (T4) and triiodothyronine (T3) * by the thyroid gland, and these hormones control the rates of most intracellular chemical reactions in the body
PROLACTIN (PRL)– promotes mammary gland development and milk production (DONT CONFUSE WITH OXYTOCIN: expression of milk)
GONADOTROPINS (FSH and LH) – control growth of the ovaries and testes, as well as their hormonal and reproductive activities
POSTERIOR PITUITARY (NEUROHYPOPHYSIS)
The NEUROHYPOPHYSIS originates from a neural tissue outgrowth from the ?
Composed by glial-like cells and axons of large neurons called ** ? ? **
Their ? are located in the hypothalamus
? and ? nucleus (refer to pic in ans)
The hormones are produced in the hypothalamus and ? in the axoplasm to the pituitary
The ? contain many secretory granules and lie on the ? of capillaries where they secrete ** #? hormones **
POSTERIOR PITUITARY (NEUROHYPOPHYSIS)
The NEUROHYPOPHYSIS originates from a neural tissue outgrowth from the HYPOTHALAMUS
Composed by glial-like cells and axons of large neurons called ** MAGNOCELLULAR NEURON **
Their *cell bodies are located in the hypothalamus
paraventricular and supraoptic nucleus (refer to pic in ans) *
The hormones are produced in the hypothalamus and transported in the axoplasm to the pituitary (where the terminal axons are located)
The nerve endings contain many secretory granules and lie on the surface of capillaries where they secrete ** #2 hormones **
POSTERIOR PITUITARY (NEUROHYPOPHYSIS)
2 important peptide hormones are secreted by the neurohypophysis
- ? HORMONE (ADH) or ?
o Controls the rate of ? into the urine, helping to control the concentration of water in the body fluids - OXYTOCIN
o Released during ? – mating behavior, parenting behavior/?
o Released during pregnancy and nursing. Effects on smooth muscles:
Helps with the ? of the baby at the end of gestation
Helps ** ? ** milk from the mammary gland to the nipples during suckling
POSTERIOR PITUITARY (NEUROHYPOPHYSIS)
2 important peptide hormones are secreted by the neurohypophysis
- ANTIDIURETIC HORMONE (ADH) or VASOPRESSIN
o Controls the rate of water excretion into the urine, helping to control the concentration of water in the body fluids - OXYTOCIN
o Released during copulation – mating behavior, parenting behavior/monogamy
o Released during pregnancy and nursing. Effects on smooth muscles:
Helps with the delivery of the baby at the end of gestation
Helps ** express ** milk from the mammary gland to the nipples during suckling
NEUROPHYPOPHYSIS (refer to pic in ANS)
- Hypothalamic neurons synthesize ? and ?
- Oxytocin and ADH are transported along the ?-? tract to the posterior pituitary
- Oxytocin and ADH are stored in ? terminals in the ? pituitary
- Oxytocin and ADH are released into the ? when hypothalamic neurons fire
NEUROPHYPOPHYSIS (refer to pic in ANS)
- Hypothalamic neurons synthesize oxytocin and ADH
- Oxytocin and ADH are transported along the hypothalamus-hypophyseal tract to the posterior pituitary
- Oxytocin and ADH are stored in axon terminals in the posterior pituitary
- Oxytocin and ADH are released into the blood when hypothalamic neurons fire
top pic
ADH and oxytocin are produced in the neuron’s cell body and transported through the axon using a specific protein called ?
processing of the precursor to the mature peptide takes place as the secretory granules move down the axon
(neurophysin is attached to vasopressin)
- So we have calcium influx into the axon terminal binding to these vesicles and facilitating exocytosis of the hormone.
- And so these hormones will be taken into the capillaries and enter into the main bloodstream, and it goes to the target organ i.e. kidneys (as target of ADH = kidney)
- we don’t know role of neurophysin; only know it’s a protein also synthesized here and it binds to ADH into these vesicles and is secreted in the bloodstream)
Pic shows the same process but diff. visual
Vasopressinergic neurons in the hypothalamus receive input from several sources -> in response, the neuron synthesizes the precursor hormone which is packed for transportation to the nerve ending
-> The axon terminates on the capillary walls where hormone will be released in a calcium-dependent manner -> Hormone and its associated neurophysin diffuse through fenestrations in the capillary wall into the capillaries
So this the neuron body containing all, you know, the nucleus, the smooth ER, the plasma, Golgi apparatus and so on.
So the hormone is packed into these vesicles and it’s carried through the axon lengths to the axon terminal, and it is then released into the fenestrated capillaries.
hypothalamus senses quantitiy of hormones and depending on the understanding of the hypothalamus, it will start releasing the stimulatory or inhibitory hormones to the “hypophysis”
Hypophysis will in turn will be then produce the other hormones and then release them into the stream to the target gland and target gland-producing hormones
so there are the negative feedback loop and then you have the long loops that go from the blood circulation to the HYPOHYSIS or to the hypothalamus.
And then you have this short loop, which goes from the HYPOPHYSIS to the hypothalamus. and then the positive feedback loop, it’s basically the same mechanism but only diff. is that stimulation instead of inhibition occurs.
So the negative feedback loop will stop it, slow down, or block the production of that hormone And the positive feedback loop will then enhance the production of that hormone.
pic summarizes everything discussed in this lecture and “we should know everything on there”
