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FUNGSI HORMON
YETTY MACHRINA
DEPARTEMEN FISIOLOGIFAKULTAS KEDOKTERAN USU
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Fungsi Hormon
Metabolisme (KH, Lemak, Protein)
Keseimbangan cairan
Pertumbuhan, produksi sel darah merah
Stabilitas lingkungan internal (Kadar glukosadarah,tekanan darah, Kadar mineral, dll)
Kontrol sirkulasi dan pencernaan /
penyerapam makanan. Ketahanan thd Stress
Perkembangan Seksual dan Reproduksi
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HORMON : suatu zat kimia yang di sekresikan
oleh kelenjar endokrin, masuk ke dalam
peredaran darah ke seluruh tubuh, untuk
merangsang atau menghambataktifitas
sel/jaringan tertentu .
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Hormon bersirkulasi ke semua jaringan, tapihanya sel-sel target yang dapat diaktifkan.
Sel target harus memiliki reseptor spesifikyang dapat ditempati hormon.
Reseptor-reseptor ini terletak di intrasel ataudi membran plasma.
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Contoh-contoh aktivitas hormon :
Reseptor ACTH hanya ada di sel-sel
tertentu pada korteks adrenal. Reseptor Thyroxin dijumpai pada hampir
semua sel-sel tubuh.
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Classification
Hormones can be classified by several properties
1. Classification by site of action.
Autocrine secretion - substance released by cell that
affects the secreting cell itself
(e.g. norepinephrine is released by a neurosecretory cell in
the adrenal medulla, and norepinephrine itself inhibitsfurther release by that cell - this is also an example of
direct negative feedback)
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Paracrinesecretion - substance released by cell that affects
neighboring cells. Not released into bloodstream(e.g. histamine released at site of injury to constrict blood
vessel walls and stop bleeding)
Endocrine secretion - substance released by cell intobloodstream that affects distant cells.
(e.g. testosterone is secreted by Leydig cells in testis, makes
hair grow on your back)
Though hormones may also have autocrine or paracrine
actions, we're mainly concerned with endocrine actions
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Exocrinesecretion - substance released by cell into a duct
that leads to epithelial surface
(onto skin or into gut). Action doesnt depend on receptors intarget tissue. (e.g. sweat, saliva)
Endocrine and exocrine secretions are glandular
secretions; they come from specialized secretory cells thatare clumped together to form a gland. Endocrine glands are
sometimes called ductless glands.
Note that a secretion may have several sites of action
simultaneously.Example of norepinephrine above - autocrineaction causes
negative feedback on secretion. Simultaneously, endocrine
action causes respiration rate to , peripheral blood vessels
to contract, etc.
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Circulating hormones
act on distant targets
travel in blood
Local hormones
act on neighboringcells or same cell thatsecreted them
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2. Classification by origin.
Another set of terms, related to those just discussed, is
commonly used to classify secretions, based both on
originand site of action
Neurohormones- endocrine, source = nerve
Glandular hormones- endocrine, source = gland
Local Hormones- paracrine (source may not be gland)
Pheromones- exocrine
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Chemical signaling by hormones: (a) Endocrine hormones are produced by cells ofendocrine glands and transported by the blood to target cells. (b) Some hormones arereleased by neurosecretory cells, which function in both the nervous and endocrinesystems. (c) A few hormones are secreted over short distances through tissue fluid.
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Tipe hormon berdasarkan struktur
molekul:
1. Asam Amino ; sebagian besar hormon
contoh : insulin, growth hormone, prolactin
2.Steroid ; derivat kolesterol
Contoh :hormon yg dihasilkan gonad (testosterone,
estrogen) dan korteks adrenal (hormon
adrenokortikal)
3.Eikosanoid ; sekresi lokal-bekerja lokal-hormondisekresi oleh semua membran sel
contoh : leukotrien dan prostaglandin
4. Amin ; katekolamin dan hormon tiroid.
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Action of Lipid-Soluble Hormones
Hormone diffuses
through phospholipid
bilayer & into cell
Binds to receptor
turning on/off specificgenes
Gene copies are formed
& direct synthesis of
new proteins
New protein alters cells
activity
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Action of Lipid-
insoluble Hormones
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The mechanism of peptide hormones(1) Peptide hormones are produced by an endocrine gland and carried by the blood. (2)
Receptors on the plasma membrane of a target cell bind with the hormone. The hormone
itself does not enter the cell. (3) An enzyme in the plasma membrane changes ATP to cyclic
AMP (cAMP). The cAMP molecule is the secondmessenger, carrying the hormones signal
through the cell. (4) Enzymes are activated, triggering a series of reactions. (5) These
reactions bring about the changes controlled by the hormone.
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The mechanism of steroid hormones(1) Steroid hormones are released by endocrine cells and carried by the blood. (2)Because of their size and structure, steroid hormones enter the cell. (3) The hormonesenter the nucleus, where they bind to receptor molecules. The hormone-receptor complex
binds to DNA and regulates gene expression. (4) If the gene is switchedon it will betranscribed and translated to protein. (5) The protein made in this way is the effect of thehormones release.
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Konsentrasi hormon yang beredar dalam
darah menggambarkan :
Kecepatan penglepasan hormon
Kecepatan inaktivasi dan pengeluaran dari
tubuh
Hormon dikeluarkan dari darah :
Enzim peng-degradasi Ginjal
Sistem enzim hepar
Konsentrasi hormon dalam Darah
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Kadar hormon dalam darah,secara umum :
Diatur dengan sistem umpan balik negatifYaitu adanya kontrol penglepasan hormon oleh:
1. stimulus humoral
2. stimulus neural
3. stimulus hormonal
Kontrol terhadap penglepasan hormon
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Stimulasi Humoral
Sekresi hormon sebagai respon terhadap
perubahan kadar ion dan nutrien dalam
darah.
Contoh : konsentrasi ion Kalsium dalam
darah mempengaruhi
pelepasan PTH atau calcitonin
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Stimulasi Neural
Serabut saraf menstimuli
penglepasan hormon
Contoh : serat saraf simpatetikmenstimulasi medula adrenal
untuk mensekresi
katekolamin.
Figure 16.4b
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Penglepasan hormon sebagai respon
terhadap hormon lain yg dihasilkan
organ endokrin berbeda.
Contoh :
Hormon-hormon hipotalamus
menstimulasi hipofise anterior.
Sebaliknya, hormon hipofisemenstimulasi berbagai organ endokrin
lain untuk mensekresi lebih banyak
hormon lain.
Stimuli Hormonal
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Contohpengaturan
dengan umpanbalik negatif :
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Pulsatility in
GnRH & LH release
0
2
4
6
8
10
12
14 GnRH (pg/10 min)
LH (ng/ml)
12:00 16:0014:00
Time of day
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Gangguan endokrin disebabkan oleh :
Kelebihan hormon
Resistensi thd hormon.
defisiensi hormon
Cara diagnosa
Menentukan aktivitas kelenjar endokrin :
Aktivitas menurun
Aktivitas meningkat
Mengukur kadar, dalam :
darah
urine
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Location of Major Endrocrine Organs
Copyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 9.3
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