Transcript ANATOMIA FUNCTIONALA/ FIZIOPATOLOGIA HIPOTALAMUSULUI

FUNCTIONAL ANATOMY AND
PHYSIOPATHOLOGY OF
HYPOTHALAMUS AND
ADENOHYPOPHISIS
PHYSIOTHERAPY IN
ENDOCRINE PATHOLOGY
Outline and objectives of the
course
Outline
Objectives
HYPOTHALAMUS
-Describe the location, structure and function of the
hypothalamus
-Describe the hormons of the hypothalamus
HYPOPHISIS
Hormones of the
adenohypophisis
Regualation of the
AdenoHy hormones
Hormones of the
neuroHy
Pituitary disorders
-Explain the functions of anterior pituitary hormones
and how they are regulated
-Explain the functions of posterior pituitary hormones
and how they are regulated
- Summarise the characteristics of pituitary disorders
HYPOTHALAMUS STRUCTURE
OVERVIEW
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Located inferior to the talamus
Represents the ventral region of the
midbrain
Center of homeostasis
GENERAL PRESENTATION
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The hypothalamus (from Greek ὑποθαλαμος = under the
thalamus) is a region of the mammalian brain located below the
thalamus, forming the major portion of the ventral region of the
diencephalon and functioning to regulate certain metabolic
processes and other autonomic activities.
The hypothalamus links the nervous system to the endocrine
system via the pituitary gland, also known as the "master
gland," by synthesizing and secreting neurohormones, often
called releasing hormones, as needed that control the secretion
of hormones from the anterior pituitary gland — among them,
gonadotropin-releasing hormone (GnRH). The neurons that
secrete GnRH are linked to the limbic system, which is primarily
involved in the control of emotions and sexual activity. The
hypothalamus also controls body temperature, hunger, thirst,
and circadian cycles.
GENERAL PRESENTATION
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The hypothalamus co-ordinates many seasonal and
circadian
rhythms,
complex
patterns
of
neuroendocrine outputs, complex homeostatic
mechanisms, and many important stereotyped
behaviours. The hypothalamus must therefore
respond to many different signals, some of which are
generated externally and some internally. The
hypothalamus is thus richly connected with many
parts of the CNS, including the brainstem reticular
formation and autonomic zones, the limbic forebrain
(particularly the amygdala, septum, diagonal band of
Broca, and the olfactory bulbs, and the cerebral
cortex).
FUNCTION
The hypothalamus is responsive to:
 Light: daylength and photoperiod for generating circadian and
seasonal rhythms
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Olfactory stimuli, including pheromones
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Steroids, including gonadal steroids and corticosteroids
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Neurally transmitted information arising in particular from the
heart, the stomach, and the reproductive tract
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Autonomic inputs
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Blood-borne stimuli, including leptin, ghrelin, angiotensin,
insulin, pituitary hormones, cytokines, plasma concentrations of
glucose and osmolarity etc
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Stress
 Invading microorganisms by increasing body temperature,
resetting the bodys thermostat upward.
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The hypothalamus is a very
complex region, and even small
nuclei within the hypothalamus
are involved in many different
functions. The paraventricular
nucleus contains oxytocin and
vasopressin neurons which
project to the posterior pituitary,
but also contains neurons that
regulate ACTH and TSH secretion
(which project to the anterior
pituitary), gastric reflexes,
maternal behavior, blood
pressure, feeding, immune
responses, and temperature.
Hypothalamic nuclei
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Medial Area
Anterior
Medial preoptic nucleus
Supraoptic nucleus
Paraventricular nucleus
Anterior nucleus
Suprachiasmatic nucleus
Tuberal
Dorsomedial nucleus
Ventromedial nucleus
Arcuate nucleus
Posterior
Mammillary nuclei (part
of mammillary bodies)
Posterior nucleus
Lateral Area
Anterior
Lateral preoptic nucleus
Lateral nucleus
Part of supraoptic
nucleus
Tuberal
Lateral nucleus
Lateral tuberal nuclei
Posterior
Lateral nucleus
Hormones of the
hypothalamus
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Corticotropin-releasing hormone (CRH)
Dopamine
Gonadotropin-releasing hormone (GnRH)
Growth hormone releasing hormone (GHRH)
Somatostatin
Thyrotropin-releasing hormone (TRH)
Hypocreatin
Antidiuretic Hormone (ADH)
HT role in obesity
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An important aspect of hypothalamic
autonomic control with regard to the
endocrine system is the control of food
intake. The effects of obesity on
endocrine function can be widespread
and endocrine abnormalities can cause
obesity. A number of hormones play
central roles in the control of food
intake
Measures of obesity
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Three main experimental measures of fat mass in man have been used
for many years. They require the determination of body density, water
or potassium content and the assumption that the body composition
can be divided into fat and fat-free or lean body mass with certain
characteristics. These techniques are relatively costly, time-consuming
and do not give information on the distribution of the fat.
Techniques such as bioelectrical impedance rely on the fact that fat is
not as good an electrical conductor as lean body mass. It is cheap but
also does not allow an assessment of the distribution of the fat mass.
Imaging techniques such as CT or MR allow the determination of fat
from a number of tomographic 'slices' of the body. The distribution of
the fat mass can be calculated.
Simple anthropomorphic measurements such as height and weight
allow the calculation of body mass index (BMI), whilst calipers can be
used to measure subcutaneous fat.
BMI = body weight (in kg)/height2 (in m)
Waist/hip circumference * = ratio of waist circumference to that of the
hips
HIPOPHYSIS (pituitary gland)
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O,5-0,8 G
anterior pituitary (adenohypophysis)
posterior pituitary (neurohypophysis)
Regulated by hypothalamus – providing
anatomical and physiological
connections between nervous and
endocrine system
ADENOHYPOPHYSIS
Connected with the hypothalamus via the
hypophyseal portal system
NEUROHYPOPHYSIS
Connected with the hypothalamus via the
hypophyseal tract
HORMONES OF THE
ADENOHYPOPHISIS
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Somatotropin (growth hormone)
Prolactin
Gonadotropines: follicle-stimulating
hormone (FSH); luteinizing hormone
(LH)
Thyroid stimulating hormone (TSH)
Adrenocorticotropic hormone (ACTH)
Thyrotropin
Stimulates the thyroid gland to
synthetize and secrete its hormones
(triiodothyronine – T3; thyroxine – T4)
Regulation by negative feedback ( high
concentration of T3 and T4 in blood)
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Gonadotropines (FSH, LH)
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FSH stimulates the maturation of an ovum
each month during a female reproductive
years
Stimulates maturation of sperm in males
Stimulates production of estrogen hormones
Regulation by negative feedback ( high
concentration of estrogensin blood)
LH
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Stimulates ovulation and causes
follicular cells to produce progesterone
which stimulates nidation and
mammary gland development
In males stimulates development of
interstitial cells (Leydig) of testis;
stimulates production of testosterone
Somatotropin
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Acts directly on some cells to stimulate
growth
Acts indirectly on others to release proteins
(insulin like growth factor I)
Promotes calcium absorbtion from intestine
Works with insulin and thyroid hormones to
promote collagen synthesis
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Increase the rate at wich cells take up
aminoacids and use them to synthetise
proteins
Stimulate free fatty acid release from
fat cells and glycogen breakdown in the
liver
Stimulate growth to adult size
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Bone and muscle loss associated with
reduced strength in aging may be due
to declining GH after age 50.
At age 30 – body mass: 10% bone,
30% muscle, 20% fatty tissue
At age 75 - body mass: 8% bone, 15%
muscle, 40% fatty tissue
Corticotropin(ACTH)
Acts on the cortex of the adrenal gland to
regulate synthesis and secretion of several of
its hormones, especially glucocorticoids
 Glucocorticoids stimulate the release of fatty
acids and glucose into the blood and help the
body to resist stress and inflamation
Regulation by negative feedback ( high
concentration of cortisol in blood)
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Prolactin
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Stimulates milk secretion in mammary
glands previously prepared for milk
production by other hormones –
estradiol, progesterone, corticosteroids,
insulin
Beta-lipoprotein
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Has been isolated from the anterior
pituitary gland
Endorphins and enkefalins can be made
from it in the anterior pituitary or in
the brain directly
Melanocyte stimulating hormone
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Secreted in small quantities by the
intermediate lobe of pituitary gland
Role in skin pigmentation
Regulation of the
adenohypophyseal hormones
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By neurohormones secreted by hypothalamus
(releasind and inhibiting)
Tropic hormones from the anterior pituitary regulate
other glands such as the thyroid, adrenal cortex,
gonads
Hormones from these glands act by negative
feedback to inhibit the release of both tropic and
hypothalamic hormones
Neural signals elicited by sexual arousal, stress,
anxiety, trauma, variations in the light-dark cycle and
the sucking of a breast-fed infant also regualte
hypothalamus hormones
Hypothalamic hormones that
regulate secretion of adenoHY
Hormone
Abreviation
Function
Thyrotropin releasing
hormone
TRH
Stimulates release of
TSH
Corticotropin releasing
hormone
CRH
Stimulates release of
ACTH
Gonadotropin releasing
hormone
GnRH
Stimulates release of
FSH and LH
Growth hormone
releasing hormone
GHRHH
Stimulates release of
GH
Growth hormone
inhibiting hormone
(somatostatin)
GHIH
Inhibits release of GH
Prolactin releasing
hormone
PRH
Stimulates release of
prolactin
Prolactin inhibiting
hormone
PIH
Inhibits release of
prolactin
Hormones of the
neurohypophysis
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2 chemically similar peptide hormones,
ocytocin and antidiuretic hormone are
called neurosecretions because are
synthetised in hypotalamic neurons and
stored in the neuroHY
When action potentials causes their
release from axons they enter the blood
and act as hormones.
Oxytocin
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Stimulates contraction of smooth
muscle in the uterus and the contractile
cells around mammary gland ducts
Is relased during sexual intercourse,
labor, lactation
Antidiuretic hormone (ADH)
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Also called vasopresine
Prevents excess water loss in urine
In high concentrations constricts blood
vessels
Decreases osmotic pressure and the
urine volume
Increases the blood volume
Pituitary disoders
Disorder
Possible cause
Hormone
Excess or
defficiency
Effects
Pituitary
dwarfism
Destruction or
congenital defficiency of
GH production cells
GH
defficiency
Small, well proportioned body,
sexual imaturity
Gigantism
Pituitary tumor before
adult size is reached
GH
excess
Large, well proportioned body
Acromegaly
Pituitary tumor after
adult size is reached
GH
excess
Disproportionate increase in
thickness of bones of face,
hands and feet
Panhypopituit
arism
Tumor or thrombus
all
defficiency
Depressed thyroid,
adrenocortical and gonad
function
Diabetes
insipidus
Damage to the
hypothalamus
ADH
defficiency
Excessive excretion of dilute
urine
High ADH
blood level
Excessive stimulation of
ADH-secreting neurons
or pituitary tumor
ADH
excess
Excessively dilute blood and low
sodiun concentration in plasma
Reminder
Glands
Hormones
Target cells
Major effects
Negative
feedback
disorders
Adeno
hypophisis
Growth hormone
(somatotropin)
Most cells
growth, maintanence
of adult size, protein
synthesis, release of
fats and glucose into
blood
Blood nutrient
level
Dwarfism,
gigantism,
acromegaly
Prolactin
Mammary
glands
Secretion of milk
Follicle stimulating
hormone(FSH)
Ovaries
Maturation of ova;
production of
estrogen
Maturation of sperm
Estrogen
Release of ova;
production of
progesterone
Development of
interstitial cells and
production of
testosterone
Progesterone
Testes
Luteinizing hormone
(LH)
Ovaries
Testes
Inhibin
Testosterone
Adrenocorticotropic
hormone (ACTH)
Adrenal cortex
Release of hormones
from adrenal cortex
Cortisol
Thyroid stimulating
hormone (TSH)thyrotropin
Thyroid gland
Synthesis and release
of T3, T4
T3, T4
Reminder
Glands
Hormones
Target cells
Major effects
Neurohypophisis
Oxytocin
Smooth muscle of
uterus and
mammary ducts
Cause uterine
contraction and
release of milk
Antidiuretic
hormone (ADH)vasopresin
Kidney tubules
Smooth muscle of
blood vessels
Water reabsorbtion
Constrict blood
vessels and raise
blood pressure
Negative feedback
REFERENCES
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Avramescu ET, Rusu L., Ciupeanu – Calugaru D., 2005, Human
Anatomy, Universitaria Publishing House, Craiova
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,
Bello M., Testing the effects of growth hormone releasing hormone,
Research Resources 9, no 10:1, 1985
Creager J., 1992, Wm. C. Brown Publisher
Lechan, R., Neuroendocrinology of pituitary hormone regulation,
Endocrinology and Metabolism Clinics 16, no 3:475, 1987