Upload
teodora-datonya-panova
View
221
Download
0
Embed Size (px)
Citation preview
7/31/2019 HBA Homeostasis and the Endocrine System 2
1/17
Homeostasis and theEndocrine System 2
Dr Terri Meehan-Andrews
School of Human BioscienceAS2 Room 3.07
Email: [email protected]
7/31/2019 HBA Homeostasis and the Endocrine System 2
2/17
Aims and Objectives
Text reference: Chapter 16. The Endocrine System. The Pituitary Gland
and Hypothalamus
Describe the structural and functional relationships
between the hypothalamus and a) the anterior and b) the
posterior pituitary gland
For thyroid hormone describe: actions, synthesis(briefly), hormonal stimulation of synthesis and secretion
and negative feedback control involving hypothalamic
and pituitary hormones
7/31/2019 HBA Homeostasis and the Endocrine System 2
3/17
Hypothalamus
Regulates a wide variety ofphysiological processes:
maintenance of bodytemperature,
water balance, sleeping
feeding
Via the autonomic nervous
system and the neuroendocrinesystem.
Its endocrine functions aremediated by the pituitary gland.
Figure 16.6
7/31/2019 HBA Homeostasis and the Endocrine System 2
4/17
Pituitary Gland Pituitary gland
two-lobed organ that secretes eight major hormones Connected to hypothalamus via infundibulum
Posterior pituitary (neural tissue) Receives, stores, and releases hormones from the hypothalamus
Anterior pituitary, made up of glandular tissue Synthesizes and secretes a number of hormones
7/31/2019 HBA Homeostasis and the Endocrine System 2
5/17
Posterior Pituitary
Neural tissue
Connection: hypothalamic hypophyseal tract
Two hormones are synthesized in the hypothalamus in cell bodies of
neurons
Oxytocin and antidiuretic hormone (ADH)
Hormones
travel down axons of tract into the posterior pituitary
stored in axon terminals
released into circulation when stimulated
7/31/2019 HBA Homeostasis and the Endocrine System 2
6/17
Hypothalamicneuronssynthesize oxytocinand ADH.
Oxytocin and ADH aretransported along thehypothalamic-hypophysealtract to the posteriorpituitary.
Oxytocin and ADH arestored in axon terminalsin the posterior pituitary.
Oxytocin and ADH arereleased into the blood
when hypothalamicneurons fire.
Paraventricularnucleus
Supraopticnucleus
Optic chiasma
Hypothalamus
Inferiorhypophyseal artery
Oxytocin
ADH
Infundibulum(connecting stalk)
Hypothalamic-hypophyseal
tract
Axonterminals
Posteriorlobe of
pituitary
1
2
3
4
Figure 16.5
Relationships of the Posterior pituitary glandand hypothalamus.
7/31/2019 HBA Homeostasis and the Endocrine System 2
7/17
Pituitary Pituitary
Oxytocin
Breast - hormonal trigger for milk ejection or
let down
Uterus - Strong stimulant of uterine
contraction
Anti diuretic hormone Stimulates the Kidney tubules to reabsorb
water (less urine formed)
7/31/2019 HBA Homeostasis and the Endocrine System 2
8/17
Anterior Pituitary
Glandular tissue Connection (vascular)hypophyseal portal
system
Manufactures, stores and secretes 6different hormones (all proteins)
Tropic hormones hormones that regulate
the secretion and growth of otherendocrine glands
7/31/2019 HBA Homeostasis and the Endocrine System 2
9/17
Anterior Pituitary
Stimulus
Hypothalamus (releasing hormone)
Hypophyseal portal system
Anterior pituitary tropic H (2)
Blood stream (circulation)
Endocrine organ
growth, hormone production and secretion
7/31/2019 HBA Homeostasis and the Endocrine System 2
10/17
When appropriately
stimulated,hypothalamic neuronssecrete releasing andinhibiting hormonesinto the primarycapillary plexus.
Hypothalamic hormonestravel through the portalveins to the anterior pituitarywhere they stimulate orinhibit release of hormonesfrom the anterior pituitary.
Anterior pituitaryhormones are secretedinto the secondarycapillary plexus.
Hypothalamus
Hypothalamic neuroncell bodies
Hypophysealportal system Primary capillary
plexus Hypophyseal
portal veins Secondary
capillaryplexus
Superiorhypophyseal artery
Anterior lobeof pituitary
TSH, FSH,LH, ACTH,
GH, PRL
1
2
3
Figure 16.5b
Relationships of the Anterior pituitary glandand hypothalamus.
7/31/2019 HBA Homeostasis and the Endocrine System 2
11/17
Anterior Pituitary
Six hormones
Growth hormone Stimulates growth and metabolism
Prolactin stimulates milk production by the breasts
The tropic hormones (stimulate the secretion of other hormones):
Thyroid-stimulating hormone (TSH)
thyroid hormone synthesis and secretion
Adrenocorticotropic hormone (ACTH)
release of glucocorticoids (cortisol) from the adrenal cortex
Gonadotrophins
Follicle-stimulating hormone (FSH) stimulates follicular
development
Luteinizing hormone (LH) stimulates testosterone
synthesis and production
7/31/2019 HBA Homeostasis and the Endocrine System 2
12/17
Hypothalamus is a key integration centre of the brainUnderstand all of the connections
Signals viathe nervous
system
Anterior Pituitary Posterior Pituitary
7/31/2019 HBA Homeostasis and the Endocrine System 2
13/17
Thyroid Gland The largest endocrine gland, located in the anterior neck, consists of two
lateral lobes connected by a median tissue mass called the isthmus
Composed of follicles that produce the glycoprotein thyroglobulin Colloid (thyroglobulin + iodine) fills the lumen of the follicles and is the
precursor of thyroid hormone
Other endocrine cells, the parafollicular cells, produce the hormonecalcitonin
7/31/2019 HBA Homeostasis and the Endocrine System 2
14/17
Thyroid Hormone
Thyroid hormonethe bodys major metabolic hormone Consists of two closely related iodine-containing compounds
T4 thyroxine; has two tyrosine molecules plus four boundiodine atoms
Converted to T3 at target tissue
T3 triiodothyronine; has two tyrosines with three boundiodine atoms
Biologically active form
7/31/2019 HBA Homeostasis and the Endocrine System 2
15/17
Thyroid Hormone
T4 and T3 are carried in plasma bound bind to
thyroxine-binding globulins (TBGs) produced by
the liver Protects from metabolism and excretion
Mechanisms of activity are similar to steroids
Revise signaling
7/31/2019 HBA Homeostasis and the Endocrine System 2
16/17
Thyroid Hormone
Glucose
oxidation
Metabolic rate
Heat production
Regulating tissuegrowth
CNS
Development
Mentalalertness
Reflexes
Stress
Thyroid produce and secretethyroid hormones
Hypothalamus
Negativefeedback loop
ThyroidReleasing hormone
Thyroid stimulatinghormone
T3 and T4
TemperatureMetabolic Rate
7/31/2019 HBA Homeostasis and the Endocrine System 2
17/17
Pathology
If levels of T3/T4 were low, what wouldhappen to the levels of TRH and TSH?Why?
What do you think would be symptoms forhypothryoidism (low T3/T4 levels)