The Role of Hormones

8/2/2019 The Role of Hormones

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THE ROLE OFHORMONESIN HUMAN


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HORMONE???

Hormone are chemical messenger produced byendocrine glands

It takes only a small amount to cause big changes incells or even the whole body

Hormones work slowly, over time, and affect manydifferent processes, including:

Growth and development

Metabolism Sexual function

Reproduction

Mood


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consist of many glands

each gland secrete different types

of hormone

Endocrine gland are ductless

gland

Hence, hormones are secretes

directly into interstitial fluid and into

the bloodstream The circulating blood then delivers

hormone to the target cells


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Why do we need endocrine system?

1. The endocrine system and nervous system playimportant roles in maintaining homeostasis.

2. Both this system often works together.

3. The endocrine system usually complement the nervous

system.

Ex: When dehydrated, the blood osmotic pressureincreased. This stimulates the neurones in thehypothalamus which in activates the pituitary glands torelease the antidiuretic hormones (ADH). ADH causes thekidneys to retain more water. Thus, the osmotic pressuredecrease and return to normal again.


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The endocrine system Controls involuntary actions

Conveys chemical signal(hormones)

Messages are conveyed via thebloodstream

Message are conveyed slowly

Messages are carried from thesource to the various destination

The response or effects are long-lasting

The nervous system Control voluntary and

involuntary actions

Conveys electrical signals

Messages are conducted vianeurones.

Messages are conveyedrapidly

Messages are carried

between specific locations

The responses or effect aretemporary


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FUNCTION OF HORMONES

3 MAIN CATEGORIES:

Reproduction

(FSH, LH, oestrogens, progesterone, androgen)

Growth

(growth hormone, thyroid-stimulating hormone,

thyroxine)

Homeostasis

( insulin, glucagon, ADH, adrenaline)


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REGULATION OF HORMONES

SECRETION

How???

- Regulates by the other hormones

- Regulate by the signals from the nervoussystem

- Regulates by the level of certain substances in

the body


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The hypothalamus serve as a link between the

nervous system and the endocrine system The hypothalamus act on the endocrine

system by controlling the pituitary gland

In hypothalamus = neurosecretory cells These cells produce hypothalamic releasing

hormone and hypothalamic inhibiting

hormone


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Ex:

Thyroid-releasing hormone (TRH) inhypothalamus stimulates the anterior

pituitary to secretes thyroid-stimulating

hormones (TSH)

TSH stimulate the thyroid gland to secretes

thyroxine


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HYPOTHALAMUSThyroid-releasingHormone, TRH

ANTERIOR PITUITARYThyroid-stimulating

Hormone, TSH

TARGET GLANDThyroxine

Stimulates the anterior

pituitary to secrete TSH

Stimulates the target gland

to secrete Thyroxine

When the thyroxine concentration exceeds a certain level in

the blood, its inhibits TRH production in the hypothalamusand TSH production from the anterior pituitary

Negative

feedback

inhibits

the releaseof TSH

Negative

feedbackinhibits the

release of

TRH

Negative feedback mechanism in hormone regulation


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Regulation by the other substances:

blood glucose level rise

the pancreas produce insulin

insulin causes increase in glucose uptake by

cells the cells metabolise the glucose or convert it

into glycogen

as a result, blood glucose level return tonormal


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ThyroxineInsulin

Growth hormon (GH)

TestosteroneOestrogen

Progesterone


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ThyroxineUNDER SECRETION OVER SECRETION

~Cretinismstunted physical and

mental in children

~ Myxedema in adult: slow heart

rate, low body temperature, a

tendency to gain weight easily

~Increase metabolic rate, increase

heartbeat, excessive sweating,

nervousness, restlessness and weight loss


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Insulin

UNDER SECRETION OVER SECRETION

~Diabetes mellitus - high blood sugar level

and sugar in urine.

~Hypoglycaemia abnormal lowering of

blood sugar level (lead to shock and coma)


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Growth hormone (GH)UNDER SECRETION OVER SECRETION

~Dwarfism ~Gigantism (childhood)

~Acromegaly (adult)


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Facial aspect of a patient with acromegaly

The nose is widened and thickened.

The cheekbones are obvious, the foreheadbulges, the lips are thick and the facial linesare marked.


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Testosterone


~ Inhibit the development of male

secondary characteristics

~Excessive male characteristics and early

puberty.


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Oestrogen


~Inhibits the development of

secondary sex characteristics in

female.

~Excessive female characteristics and

early puberty.


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Progesterone


~Abortion of embryo ~Failure in delivery at the correct time.

The Role of Hormones

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