Week 8 Flashcards
1
Q
The Neuroendocrine System comprises cells which secrete what products?
A
(neurotransmitters and neuropeptides)
2
Q
where does the Neuroendocrine System secrete their products into?
A
directly into the blood stream
3
Q
is the Neuroendocrine System endogenous or exogenous ?
A
endogenous
4
Q
where are the neurons in the Neuroendocrine system?
A
hypothalamus
5
Q
why is hypothalamus important for the Neuroendocrine system?
A
hypothalamus is key to neuroendocrine regulation.
6
Q
what is the function of the The hypothalamus
list 7
A
The hypothalamus regulates physiological functions: Growth Metabolism Stress responses Osmoregulation Thermoregulation Reproduction Circadian rhythm
7
Q
what is the The Hypothalamus main role?
A
Its main role is homeostatic control
8
Q
how does the hypothalamus control homeostatis
A
By comparing inputs (sensory and contextual information) with biological set points…
9
Q
what part of the brain does contextual information come from?
A
1) cerebral cortex
2) amygdala
3) hippocampal formation
10
Q
when comparing the inputs and biological output what is the hypothalamus doing
A
… it acts to coordinate the occurrence and timing of physiological functions
11
Q
what is the biological outputs of the hypothalamus ?
A
(visceral and somatic motor activity, neuroendocrine and behavioural responses)
12
Q
what is the sensory inputs to the hypothalamus ?
A
1) visceral and somatic sensory pathway
2) chemosensory and hormonal signals
13
Q
list the 4 sensory inputs to the hypothalamus ?
A
1) visceral sensory information from vagus (BP, gut distention)
2) information from the spinal cord (body temp)
3) visual information (light and dark cycle)
4) complex sensory information (smell, emotion)
14
Q
what is the relay pathway for visceral sensory information from vagus ?
A
nucleus of tractus solitarius
15
Q
what is the relay pathway for information from the spinal cord?
A
brain stem and reticular formation
16
Q
what is the relay pathway for visual information?
A
retina
17
Q
what is the relay pathway for complex sensory information?
A
limbic and olfactory system
18
Q
where do all the relay pathways converge onto?
A
hypothalamus
19
Q
what is the controlled parameters from hypothalamus respectively?
A
1) digestion
2) body temperature control
3) circadian rhythm
4) feeding and reproduction
20
Q
what are the Inputs to the hypothalamus?
A
Telencephalic inputs, retinal to SCN
Fornix– hippocampus
Medial forebrain bundle (MFB) and dorsal longitudinal fasciculus (DLF)- brainstem & spinal cord
Stria terminalis- amygdala
21
Q
how many Circumventricular organs (CVOs) surround the ventricles?
A
7
22
Q
where else is the Circumventricular organs (CVOs) found?
A
areas where there is no blood brain barrier
23
Q
what can neurons in the Circumventricular organs (CVOs) do?
A
Neurons here are able to interact with the blood, and the hormones and metabolites within it.
24
Q
why is the Circumventricular organs (CVOs) an important sensory organ?
A
because they provide input to the hypothalamus and allow secretion of hypothalamic hormones and their regulation by target tissue hormones (median eminence and pituitary gland)
25
why are these neurons also important in terms of the hypothalamus ?
neurons that directly sense stimuli in the hypothalamus, e.g., thermosensing
26
Outputs of the hypothalamus
| list 6
1) pituitary --> hormones --> homeostasis
2) autonomic NS --> internal organ control
3) reticular formation --> wakefulness/sleep
4) thalamus --> orbitofrontal cortex
5) orbitofrontal cortex --> nucleus accumbens --> motor behaviour
6) limbic system --> nucleus accumbens --> motor behaviour
27
what is the hypothalamus the core of?
central autonomic network
28
what is the function of the central autonomic network ?
integrates sensory inputs and produces autonomic motor responses.
29
how are visceral motor responses invoked?
Visceral and other sensory inputs together with processed cognitive/ emotional information invoke visceral motor responses
30
examples of visceral motor responses
visceral responses to embarrassing, fear-inducing and sexual situations.
31
do Reticular formation centres can function independently or dependently ?
independently
32
is the Reticular formation modulated by the hypothalamus ?
yes
33
Reticular formation function
coordinate the body’s response in maintaining homeostasis (autonomic motor control and other effects including behaviour).
34
what are the 3 subdivisions of the hypothalamus?
Anterior/preoptic,
tuberal
posterior
35
what are the 3 longitudinal zones of hypothalamus?
periventricular
medial
lateral
36
role of pituitary gland
The pituitary gland mediates neuroendocrine regulation
37
what are the two main parts of The pituitary gland
1) .The anterior lobe (adenohypophysis; pars distalis)
| 2) The posterior lobe (neurohypophysis; pars nervosa)
38
where is the The anterior lobe (adenohypophysis; pars distalis) is embryologically derived from?
ectoderm of the oral cavity and is glandular tissue.
39
The posterior lobe (neurohypophysis; pars nervosa) comprises what type of axons
comprises neurosecretory axons with their terminals arising from cell bodies in the hypothalamus.
40
what does the Parvocellular, periventricular
| neurons secrete ?
releasing and release inhibiting hormones
41
where are the releasing and release inhibiting hormones secreted into?
the capillary plexus of the median eminence (a circumventricular organ; CVO).
42
where do these hormones travel to?
These hormones travel down the portal vessels into the capillary plexus of the anterior pituitary gland (a CVO).
43
what is the function of these hormones?
These hormones regulate secretion of anterior pituitary gland hormones.
44
where are the Parvocellular neurons regulating hormonal release from the anterior pituitary found?
periventricular nucleus
paraventricular
arcuate nucleus
medial preoptic nucleus.
45
where do Parvocellular neurons project onto?
They project short axons onto the hypothalamo-pituitary portal system to regulate anterior pituitary hormone secretion.
46
Neuroendocrine hormones show what type of release?
Neuroendocrine hormones show pulsatile release
47
what is pulsatile release
These are ultradian patterns (repeated period within a 24 hr circadian day)... Hormones have circadian patterns as well
48
in the Hypothalamic pituitary adrenal (HPA) stress axis what nucleus is the neurons in parvocellular found?
paraventricular nucleus of the hypothalamus
49
in the Hypothalamic pituitary adrenal (HPA) stress axis what does the Neurons in the parvocellular portion of the paraventricular nucleus of the hypothalamus (PVN) secrete
corticotropin-releasing hormone (CRH).
50
where do corticotropin-releasing hormone (CRH) act on in the HPA system
corticotropes of the anterior pituitary gland
51
when CRH acts on the corticotropes of the anterior pituitary gland what hormone is released
adrenocorticotropic hormone (ACTH)
52
where does adrenocorticotropic hormone (ACTH) act on
adrenal cortex
53
when adrenocorticotropic hormone (ACTH) acts on adrenal cortex what hormone is released
glucocorticoids
54
what are glucocorticoids
Glucocorticoids are steroids that bind nuclear transcription factor receptors.
55
how is Negative feedback is a classical mode of regulation of neuroendocrine hormones:
cortisol binds to its receptor on the neurosecretory cells in the PVN and on corticotrophs to decrease the stimulation of its release.
56
essay like format - what happens in the Hypothalamic pituitary adrenal (HPA) stress axis
Neurons in the parvocellular portion of the paraventricular nucleus of the hypothalamus (PVN) secrete corticotropin-releasing hormone (CRH).
CRH stimulates the release of adrenocorticotropic hormone (ACTH) from corticotropes of the anterior pituitary gland.
ACTH causes release of glucocorticoids from the adrenal cortex. Glucocorticoids are steroids that bind nuclear transcription factor receptors.
Negative feedback is a classical mode of regulation of neuroendocrine hormones: cortisol binds to its receptor on the neurosecretory cells in the PVN and on corticotrophs to decrease the stimulation of its release.
57
what does stress do on HPA axis
Stress is an internal or external cue that disrupts homeostasis
58
is the HPA response a flight or flight response or rest and digest adaptive response?
The HPA response the flight or fight adaptive response with the ANS
59
what are the two functions of Glucocorticoids
1) mobilise energy stores and increase cardiovascular tone
2) interact with other endocrine systems and immune system– basal metabolism controlled by thyroid hormones, the reproductive axis e.g., as well as having negative feedback on CRH, cortisol decreases gonadotropin-releasing hormone GnRH secretion, growth; Glucocorticoids inhibit the immune system
60
in addition to pulsatile secretion (ultradian) what other rhythm is there that is dependent on suprachiasmatic nucleus
there is a circadian rhythm dependent on the suprachiasmatic nucleus – highest cortisol levels are in the morning, lowest in the afternoon
61
what is the neural function of Glucocorticoids
hippocampal granule cell survival and neurogenesis; learning and memory; chronic high levels can lead to neurodegeneration and cell death
62
in the Hypothalamic pituitary thyroid (HPT) axis where in what nucleus are the neurons of parvocellular found
Paraventricular nucleus of the hypothalamus (PVN
63
what do Neurons in the parvocellular portion of the Paraventricular nucleus of the hypothalamus (PVN) secrete
thyrotropin-releasing hormone (TRH).
64
where does thyrotropin-releasing hormone (TRH) act on
thyrotropes of the anterior pituitary gland
65
when TRH acts on thyrotropes of the anterior pituitary gland what hormone is produced?
thyroid stimulating hormone (TSH; thyrotropin)
66
where does TSH act on
thyroid gland.
67
when TSH acts on the thyroid gland what hormone is produced?
thyroid hormones
68
when does Classical negative feedback occur?
Classical negative feedback occurs whereby thyroid hormones decrease stimulation of the release of TRH and TSH by acting at receptors in the PVN and adrenal gland.
69
what do thyroid hormones do?
Thyroid hormones regulate basal metabolism e.g., cellular ATP, protein synthesis, via nuclear receptors.
70
essay like format what is the Hypothalamic pituitary thyroid (HPT) axis
Neurons in the parvocellular portion of the Paraventricular nucleus of the hypothalamus (PVN) secrete thyrotropin-releasing hormone (TRH).
CRH stimulates the release of thyroid stimulating hormone (TSH; thyrotropin) from thyrotropes of the anterior pituitary gland.
TSH causes release of thyroid hormones from the thyroid gland.
Classical negative feedback occurs whereby thyroid hormones decrease stimulation of the release of TRH and TSH by acting at receptors in the PVN and adrenal gland.
Thyroid hormones regulate basal metabolism e.g., cellular ATP, protein synthesis, via nuclear receptors.
71
in the Hypothalamic control of growth (Hypothalamic- Somatotropic Axis)/ (Hypothalamic- Somatotropic Axis) where in what nucleus are the neurons of parvocellular found
arcuate nucleus (ARC)
72
what hormone does the Parvocellular neurons in the arcuate nucleus (ARC) secrete
growth hormone releasing hormone (GHRH)
73
in the Hypothalamic control of growth (Hypothalamic- Somatotropic Axis)/ (Hypothalamic- Somatotropic Axis) what other nucelus is found in the parvocellular
the periventricular nucleus of the hypothalamus
74
what do neurons in the periventricular nucleus of the hypothalamus secrete ?
somatostatin.
75
where does GHRH act on?
somatotropes of the anterior pituitary gland.
76
when GHRH acts on somatotropes of the anterior pituitary gland what hormone is produced
growth hormone (GH)
77
what does Somatostatin do?
inhibits growth hormone (GH) release
78
where and to what response are GH and insulin-like growth factor-1 (IGF-1) made
GH and insulin-like growth factor-1 (IGF-1) made by the liver in response to GH stimulates somatic (body) growth, regeneration and metabolic homeostasis in tissues like bone and muscle. GH release is strongly diurnal mostly released in sleep.
79
how does Classical negative feedback occur
Classical negative feedback occurs by actions of IGF-1 and GH to inhibit somatotropes and arcuate GHRH neurons. Feedback also stimulates periventricular cells to secrete somatostatin and thereby inhibit pituitary GH release.
80
essay like format of Hypothalamic control of growth (Hypothalamic- Somatotropic Axis)
Parvocellular neurons in the arcuate nucleus (ARC) secrete growth hormone releasing hormone (GHRH) and neurons in the periventricular nucleus of the hypothalamus secrete somatostatin.
GHRH stimulates the release of growth hormone (GH) from somatotropes of the anterior pituitary gland. Somatostatin inhibits its release.
GH and insulin-like growth factor-1 (IGF-1) made by the liver in response to GH stimulates somatic (body) growth, regeneration and metabolic homeostasis in tissues like bone and muscle. GH release is strongly diurnal mostly released in sleep.
Classical negative feedback occurs by actions of IGF-1 and GH to inhibit somatotropes and arcuate GHRH neurons. Feedback also stimulates periventricular cells to secrete somatostatin and thereby inhibit pituitary GH release.
81
what is the Hypothalamic control of lactation (Hypothalamic- Lactotropic Axis)
Neurons in the arcuate nucleus secrete dopamine which inhibits secretion of prolactin from the anterior pituitary gland through the dopamine D2 receptor. This inhibition is relieved at lactation in response to suckling. (Various factors stimulate prolactin release.)
Prolactin acts on the mammary gland to stimulate the development of the gland and production of milk. Metabolic and other reproductive system roles in males and females are suggested, as are effects on behaviour (post-coital and maternal/ paternal)
As with other anterior pituitary systems prolactin release is pulsatile and has a circadian rhythm. There is no negative feedback system.
82
what is the Hypothalamic pituitary gonadal (HPG) axis
Parvocellular neurons in the anterior and medial basal hypothalamus (MBH) secrete gonadotropin releasing hormone (GnRH).
GnRH stimulates the release of both luteinising hormone (LH) and follicle stimulating hormone (FSH) from gonadotropes of the anterior pituitary gland.
LH and FSH have roles in the gonads and cause secretion of sex hormones from the ovaries and testes. Sex hormones are important in development, expression of secondary sex characteristics and adult reproductive function.
Negative feedback occurs in both males and females. Additionally, high levels of estrogens at the late follicular stage of the ovarian cycle lead to positive feedback and a surge of GnRH that precipitates ovulation.
83
in the Neuroendocrine control of the posterior pituitary what do Magnocellular neurons of the PVN and SON produce?
the neuroendocrine peptides arginine vasopressin (AVP; anti-diuretic hormone, ADH) and oxytocin.
84
where are these hormones transported to?
The hormones are transported down axons in the pituitary stalk and stored in their terminals in the posterior pituitary gland.
85
what happens upon neural stimulation?
Upon neural simulation of the neuroendocrine cells the hypothalamic hormones are secreted into the capillaries of posterior lobe and enter the peripheral venous circulation.
86
what does vasopressin do?
osmoregulation
water/ salt balance
social behaviours
87
what does oxytocin do?
!) parturition --> uterine contraction at labour
2) milk ejection
3) social behaviours
88
what peptides are Arginine vasopressin (AVP) and oxytocin (OXT) from
9 a.a. peptides transcribed from the same gene;
89
is the 9.a.a peptides related to 2.a.a peptide
yes but has differences, some functional overlap too
90
what is Secretion dependent on
Secretion is not pulsatile, but depends on neural stimulation in response to changes in osmolality/ blood volume (AVP; to a lesser extent OXT) or nipple/ genital stimulation (OXY).
91
is this a fast response
yes --> Is a fast response system for substantial release of each endocrine hormone. Provides a quick response to haemorrhage or suckling stimuli!
92
how is the The neuroendocrine system integrated by the hypothalamus with other responses
autonomic via parvocellular AVP/OXT descending projections
behavioural effects including bonding and parental behaviours
other neuroendocrine systems especially the HPA stress axis. AVP synergises with CRH to release ACTH; OXT acts centrally in antagonism of stress-stimulated pathways
93
An example of control of vasopressin secretion:
| what does Low blood pressure stimulate?
secretion of renin from the kidney
94
what does renin do?
cleaves angiotensin I from its precursor, which is then converted to active angiotensin II.
95
function of angiotensin II.
Angiotensin II stimulates neurons in the subfornical organ (SFO, a circumventricular organ).
96
what does neural input from from the SFO to the PVN/ SON cause?
Neuronal input from the SFO to the PVN/ SON causes release of vasopressin (ADH) causing salt and water retention and increase in blood pressure and a feeling of thirst (via cortical output possibly).
97
Control of oxytocin secretion and its effects
1) Dendritic release of OT coordinates neuroendocrine secretion; may have behavioural effects
2) Changes in osmolality are detected by cells in the OVLT and PVN/SON directly to modulate AVP/OXT secretion & regulate kidney function, thirst and salt appetite
3) Effects on feeding behaviours and inhibition of parturition may be mediated by the arcuate nucleus input
4) Vagal stimulation during labour leads to increased OT secretion; uterine contraction
5) Projections to the preoptic area and amygdala mediate social & maternal behavioural effects
