Endokrein K28

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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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