Paraventricular nucleus
Encyclopedia
The paraventricular nucleus (PVN, PVA, or PVH) is a neuronal nucleus in the hypothalamus
. It contains multiple subpopulations of neurons that are activated by a variety of stressful and/or physiological changes. Many PVN neurons project directly to the posterior pituitary where they release oxytocin
or vasopressin
into the general circulation. Other PVN neurons control various anterior pituitary functions, while still others directly regulate appetite and autonomic functions in the brainstem and spinal cord.
, from which it derives its name, "paraventricular" meaning "alongside a ventricle."
It does lie within the periventricular zone and must not be confused with the periventricular nucleus
, which occupies a more medial position, beneath the third ventricle
.
The PVN is highly vascularised and is protected by the blood-brain barrier
, although its neuroendocrine
neurons extend to sites (in the median eminence
and in the posterior pituitary
) beyond the blood-brain barrier.
s whose axons extend into the posterior pituitary
, parvocellular neurosecretory cells that project to the median eminence
, and several populations of peptide
-containing cells that project to many different brain regions.
cells in the PVN elaborate and secrete two peptide hormones: oxytocin
and vasopressin
.
These hormones are packaged into large vesicles, which are then transported down the unmyelinated axon
s of the cells and released from neurosecretory nerve terminals residing in the posterior pituitary gland.
Similar magnocellular neurons are found in the supraoptic nucleus
.
neurosecretory neurons of the PVN project to the median eminence, at the base of the brain, where their neurosecretory nerve terminals release peptides vasopressin, corticotropin-releasing hormone (CRH), thyrotropin-releasing hormone (TRH), gonadotropin-releasing hormone (GnRH), growth hormone-releasing hormone (GHRH), and somatostatin (growth hormone release inhibiting hormone, GIH) into blood vessels in the hypothalamo-pituitary portal system. The blood vessels carry the peptides to the anterior pituitary
gland, where they regulate the secretion of hormones into the systemic circulation. The parvocellular neurosecretory cells include those that make:
s and populations of neurons that project centrally (i.e., to other brain regions). The centrally-projecting neurons include
Among these, inputs from neurons in structures adjacent to the anterior wall of the third ventricle (the "AV3V region") carry information about the electrolyte composition of the blood, and about circulating concentrations of such hormones as angiotensin
and relaxin
, to regulate the magnocellular neurons.
Inputs from the brainstem (the nucleus of the solitary tract) and the ventrolateral medulla carry information from the heart and stomach
. Inputs from the hippocampus
to the CRH neurones are important regulators of stress responses.
Inputs from neuropeptide Y
-containing neurons in the arcuate nucleus
co-ordinate metabolic regulation (via TRH secretion) with regulation of energy intake.
Inputs from suprachiasmatic nucleus
about levels of lighting (circadian rhythms).
Inputs from glucose sensors within the brain stimulate release of vasopressin
and Corticotropin-releasing hormone
from Parvocellular neurosecretory cell
s .
Hypothalamus
The Hypothalamus is a portion of the brain that contains a number of small nuclei with a variety of functions...
. It contains multiple subpopulations of neurons that are activated by a variety of stressful and/or physiological changes. Many PVN neurons project directly to the posterior pituitary where they release oxytocin
Oxytocin
Oxytocin is a mammalian hormone that acts primarily as a neuromodulator in the brain.Oxytocin is best known for its roles in sexual reproduction, in particular during and after childbirth...
or vasopressin
Vasopressin
Arginine vasopressin , also known as vasopressin, argipressin or antidiuretic hormone , is a neurohypophysial hormone found in most mammals, including humans. Vasopressin is a peptide hormone that controls the reabsorption of molecules in the tubules of the kidneys by affecting the tissue's...
into the general circulation. Other PVN neurons control various anterior pituitary functions, while still others directly regulate appetite and autonomic functions in the brainstem and spinal cord.
Location
The paraventricular nucleus lies adjacent to the third ventricleThird ventricle
The third ventricle is one of four connected fluid-filled cavities comprising the ventricular system within the human brain. It is a median cleft between the two thalami, and is filled with cerebrospinal fluid ....
, from which it derives its name, "paraventricular" meaning "alongside a ventricle."
It does lie within the periventricular zone and must not be confused with the periventricular nucleus
Periventricular nucleus
The Periventricular nucleus is a thin sheet of small neurons located in the wall of the third ventricle, a composite structure of the hypothalamus. Functions in analgesia....
, which occupies a more medial position, beneath the third ventricle
Third ventricle
The third ventricle is one of four connected fluid-filled cavities comprising the ventricular system within the human brain. It is a median cleft between the two thalami, and is filled with cerebrospinal fluid ....
.
The PVN is highly vascularised and is protected by the blood-brain barrier
Blood-brain barrier
The blood–brain barrier is a separation of circulating blood and the brain extracellular fluid in the central nervous system . It occurs along all capillaries and consists of tight junctions around the capillaries that do not exist in normal circulation. Endothelial cells restrict the diffusion...
, although its neuroendocrine
Neuroendocrinology
Neuroendocrinology is the study of the extensive interactions between the nervous system and the endocrine system, including the biological features of the cells that participate, and how they functionally communicate...
neurons extend to sites (in the median eminence
Median eminence
The median eminence is part of the inferior boundary for the hypothalamus part of the human brain. A small swelling on the tuber cinereum posterior to the infundibulum - atop the pituitary stalk - the median eminence lies in the area roughly bounded on its posterolateral region by the cerebral...
and in the posterior pituitary
Posterior pituitary
The posterior pituitary comprises the posterior lobe of the pituitary gland and is part of the endocrine system. Despite its name, the posterior pituitary gland is not a gland, per se; rather, it is largely a collection of axonal projections from the hypothalamus that terminate behind the anterior...
) beyond the blood-brain barrier.
Neurons
The PVN contains magnocellular neurosecretory cellMagnocellular neurosecretory cell
Magnocellular neurosecretory cells are large cells within the supraoptic nucleus and paraventricular nucleus of the hypothalamus. They are also found in smaller numbers in accessory cell groups between these two nuclei, the largest one being the nucleus circularis...
s whose axons extend into the posterior pituitary
Posterior pituitary
The posterior pituitary comprises the posterior lobe of the pituitary gland and is part of the endocrine system. Despite its name, the posterior pituitary gland is not a gland, per se; rather, it is largely a collection of axonal projections from the hypothalamus that terminate behind the anterior...
, parvocellular neurosecretory cells that project to the median eminence
Median eminence
The median eminence is part of the inferior boundary for the hypothalamus part of the human brain. A small swelling on the tuber cinereum posterior to the infundibulum - atop the pituitary stalk - the median eminence lies in the area roughly bounded on its posterolateral region by the cerebral...
, and several populations of peptide
Peptide
Peptides are short polymers of amino acid monomers linked by peptide bonds. They are distinguished from proteins on the basis of size, typically containing less than 50 monomer units. The shortest peptides are dipeptides, consisting of two amino acids joined by a single peptide bond...
-containing cells that project to many different brain regions.
Magnocellular neurosecretory neurons
The magnocellularMagnocellular neurosecretory cell
Magnocellular neurosecretory cells are large cells within the supraoptic nucleus and paraventricular nucleus of the hypothalamus. They are also found in smaller numbers in accessory cell groups between these two nuclei, the largest one being the nucleus circularis...
cells in the PVN elaborate and secrete two peptide hormones: oxytocin
Oxytocin
Oxytocin is a mammalian hormone that acts primarily as a neuromodulator in the brain.Oxytocin is best known for its roles in sexual reproduction, in particular during and after childbirth...
and vasopressin
Vasopressin
Arginine vasopressin , also known as vasopressin, argipressin or antidiuretic hormone , is a neurohypophysial hormone found in most mammals, including humans. Vasopressin is a peptide hormone that controls the reabsorption of molecules in the tubules of the kidneys by affecting the tissue's...
.
These hormones are packaged into large vesicles, which are then transported down the unmyelinated axon
Axon
An axon is a long, slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neuron's cell body or soma....
s of the cells and released from neurosecretory nerve terminals residing in the posterior pituitary gland.
Similar magnocellular neurons are found in the supraoptic nucleus
Supraoptic nucleus
The supraoptic nucleus is a nucleus of magnocellular neurosecretory cells in the hypothalamus of the mammalian brain. The nucleus is situated at the base of the brain, adjacent to the optic chiasm...
.
Parvocellular neurosecretory neurons
The axons of the parvocellularParvocellular neurosecretory cell
Parvocellular neurosecretory cells are small neurons within paraventricular nucleus of the hypothalamus. The axons of the parvocellular neurosecretory cells of the PVN project to the median eminence, at the base of the brain, where their neurosecretory nerve terminals release peptides into blood...
neurosecretory neurons of the PVN project to the median eminence, at the base of the brain, where their neurosecretory nerve terminals release peptides vasopressin, corticotropin-releasing hormone (CRH), thyrotropin-releasing hormone (TRH), gonadotropin-releasing hormone (GnRH), growth hormone-releasing hormone (GHRH), and somatostatin (growth hormone release inhibiting hormone, GIH) into blood vessels in the hypothalamo-pituitary portal system. The blood vessels carry the peptides to the anterior pituitary
Anterior pituitary
A major organ of the endocrine system, the anterior pituitary, also called the adenohypophysis, is the glandular, anterior lobe of the pituitary gland...
gland, where they regulate the secretion of hormones into the systemic circulation. The parvocellular neurosecretory cells include those that make:
- Corticotropin-releasing hormoneCorticotropin-releasing hormoneCorticotropin-releasing hormone , originally named corticotropin-releasing factor , and also called corticoliberin, is a polypeptide hormone and neurotransmitter involved in the stress response...
(CRH), which regulates ACTH secretion from the anterior pituitary gland - VasopressinVasopressinArginine vasopressin , also known as vasopressin, argipressin or antidiuretic hormone , is a neurohypophysial hormone found in most mammals, including humans. Vasopressin is a peptide hormone that controls the reabsorption of molecules in the tubules of the kidneys by affecting the tissue's...
, which also regulates ACTH secretion (vasopressin and CRH act synergistically to stimulate ACTH secretion) - Thyrotropin-releasing hormoneThyrotropin-releasing hormoneThyrotropin-releasing hormone , also called thyrotropin-releasing factor , thyroliberin or protirelin, is a tropic tripeptide hormone that stimulates the release of thyroid-stimulating hormone and prolactin by the anterior pituitary...
(TRH), which regulates TSHThyroid-stimulating hormoneThyrotrophin-stimulating hormone is a peptide hormone synthesized and secreted by thyrotrope cells in the anterior pituitary gland, which regulates the endocrine function of the thyroid gland.- Physiology :...
and prolactinProlactinProlactin also known as luteotropic hormone is a protein that in humans is encoded by the PRL gene.Prolactin is a peptide hormone discovered by Henry Friesen...
secretion
Centrally-projecting neurons
As well as neuroendocrine neurons, the PVN contains interneuronInterneuron
An interneuron is a multipolar neuron which connects afferent neurons and efferent neurons in neural pathways...
s and populations of neurons that project centrally (i.e., to other brain regions). The centrally-projecting neurons include
- Parvocellular oxytocin cells, which project mainly to the brainstem and spinal cordSpinal cordThe spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...
and are involved, respectively, in gastric reflexes and penile erection, - Parvocellular vasopressin cells, which project to many points in the hypothalamus and limbic systemLimbic systemThe limbic system is a set of brain structures including the hippocampus, amygdala, anterior thalamic nuclei, septum, limbic cortex and fornix, which seemingly support a variety of functions including emotion, behavior, long term memory, and olfaction. The term "limbic" comes from the Latin...
, as well as to the brainstem and spinal cord (these are involved in blood pressure and temperature regulation), and - Parvocellular CRH neurons, which are thought to be involved in stress-related behaviors.
Afferent inputs to the PVN
The PVN receives afferent inputs from many brain regions.Among these, inputs from neurons in structures adjacent to the anterior wall of the third ventricle (the "AV3V region") carry information about the electrolyte composition of the blood, and about circulating concentrations of such hormones as angiotensin
Angiotensin
Angiotensin, a peptide hormone, causes blood vessels to constrict, and drives blood pressure up. It is part of the renin-angiotensin system, which is a major target for drugs that lower blood pressure. Angiotensin also stimulates the release of aldosterone, another hormone, from the adrenal cortex...
and relaxin
Relaxin
Relaxin is a protein hormone first described in 1926 by Frederick Hisaw.The relaxin-like peptide family belongs in the insulin superfamily and consists of 7 peptides of high structural but low sequence similarity; relaxin-1 , 2 and 3 , and the insulin-like peptides, INSL3, INSL4, INSL5 and INSL6...
, to regulate the magnocellular neurons.
Inputs from the brainstem (the nucleus of the solitary tract) and the ventrolateral medulla carry information from the heart and stomach
Stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...
. Inputs from the hippocampus
Hippocampus
The hippocampus is a major component of the brains of humans and other vertebrates. It belongs to the limbic system and plays important roles in the consolidation of information from short-term memory to long-term memory and spatial navigation. Humans and other mammals have two hippocampi, one in...
to the CRH neurones are important regulators of stress responses.
Inputs from neuropeptide Y
Neuropeptide Y
Neuropeptide Y is a 36-amino acid peptide neurotransmitter found in the brain and autonomic nervous system."NPY has been associated with a number of physiologic processes in the brain, including the regulation of energy balance, memory and learning, and epilepsy." The main effect is increased food...
-containing neurons in the arcuate nucleus
Arcuate nucleus
The arcuate nucleus is an aggregation of neurons in the mediobasal hypothalamus, adjacent to the third ventricle and the median eminence...
co-ordinate metabolic regulation (via TRH secretion) with regulation of energy intake.
Inputs from suprachiasmatic nucleus
Suprachiasmatic nucleus
The suprachiasmatic nucleus or nuclei, abbreviated SCN, is a tiny region on the brain's midline, situated directly above the optic chiasm. It is responsible for controlling circadian rhythms...
about levels of lighting (circadian rhythms).
Inputs from glucose sensors within the brain stimulate release of vasopressin
Vasopressin
Arginine vasopressin , also known as vasopressin, argipressin or antidiuretic hormone , is a neurohypophysial hormone found in most mammals, including humans. Vasopressin is a peptide hormone that controls the reabsorption of molecules in the tubules of the kidneys by affecting the tissue's...
and Corticotropin-releasing hormone
Corticotropin-releasing hormone
Corticotropin-releasing hormone , originally named corticotropin-releasing factor , and also called corticoliberin, is a polypeptide hormone and neurotransmitter involved in the stress response...
from Parvocellular neurosecretory cell
Parvocellular neurosecretory cell
Parvocellular neurosecretory cells are small neurons within paraventricular nucleus of the hypothalamus. The axons of the parvocellular neurosecretory cells of the PVN project to the median eminence, at the base of the brain, where their neurosecretory nerve terminals release peptides into blood...
s .