Endocrine To IGCSE Biology

5/25/2018 Endocrine To IGCSE Biology

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TheEndocrine System

Controls many body

functions

exerts control by

releasing specialchemical substances into

the blood called

hormones

Hormones affect other

endocrine glands or body

systems

Derives its name from

the fact that various

glands release

hormones directly intothe blood, which in turn

transports the

hormones to target

tissues via ducts.


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The Endocrine System

Exocrine glands -

transport their

hormones to target

tissues via ducts.

Endocrine

Emergencies:

from common:

Diabetes

to the unusual:

Thyrotoxicosis


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Consists of several

glands located in

various parts of thebody.

Pituitary gland: a smallgland located on a stalk

hanging from the base of the

brain -AKA

The Master Gland

Primary function is to

control other glands.

Produces many

hormones.

Secretion is controlled by

the hypothalamus in the

base of the brain.


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The Pituitary Gland is

divided into 2 areas,

which differ

structurallyandfunctionally

each area has

separate types of

hormone production.

The two segments are:

Posterior Pituitary:

produces oxytocin

and antidiuretic

hormone (ADH)

Anterior Pituitary:

produces thyroid-

stimulating hormone

(TSH)

growth hormone (GH) adrenocorticotropin

(ACTH)

follicle-stimulating

hormone (FSH)


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And even more

luteinizing hormone

(LH)

prolactin

Lets go over these

one at a time...

Posterior Pituitary

Oxytocin(the

natural form of

pitocin) stimulates gravid

uterus

causes let down

of milk from thebreast.

ADH(vasopressin)

causes the kidney to

retain water.


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Anterior Pituitary Primarily regulates

other endocrine

glands

rarely a factor inendocrinological

emergencies

TSHstimulates the

thyroid gland torelease its

hormones, thus metabolic rate

Anterior Pituitary Growth hormone

(GH)

glucose usageconsumption of

fats as an energy

source

ACTHstimulates the

adrenal cortex torelease its hormones

FSH & LHstimulates

maturation & release

of eggs from ovary.


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The Thyroid Gland lies in the anterior

neck just below the

larynyx.

Two lobes, locatedon either side of the

trachea, connected

by a narrow band of

tissue called thei s thmus.

Sacs inside the

gland contain col lo id

Within the colloid arethe thyroid hormones:

thyroxine (T4)

triiodothyronine (T3)

When stimulated(by TSH or by

cold), these are

released into the

circulatory systemand themetabolic rate.

C cells within the

thyroid produce the

hormone calc i tonin.


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Calcitonin, when

released, lowers the

amount of calcium in

the blood.

Inadequate levels of

thyroid hormones =

hypothyroidism, orMyxedema.

Myxedema symptoms:

Facial bloating

weakness

cold intolerance

lethargy

altered mental

status

oily skin and hair

TX: replacement of

thyroid hormone.


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Increased thyroidhormone release

causes

hyper thyro id ism,

commonly calledGraves disease.

Signs and

symptoms:

insomnia, fatigue tachycardia

hypertension

heat intolerance

weight loss

Long termhyperthyroidism:

Exopthalmos

bulging of the

eyeballs (pictureBarbara Bush)

In severe cases - a

medical emergency

called thyrotoxicosiscan result.


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Parathyroid Glands

small, pea-shaped

glands, located in the

neck near the thyroid usually 4 - number can

vary

regulate the level of

calcium in the body

produce parathyroid

hormone - level ofcalcium in blood

Hypocalcemia can

result if parathyroids

are removed or

destroyed.


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Pancreas

a key gland located in

the folds of the

duodenum has both endocrine and

exocrine functions

secretes several key

digestive enzymes

Islets of Langerhans

specialized tissues in

which the endocrine

functions of thepancreas occurs

include 3 types of

cells:

alpha ( ) beta () delta ()

each secretes an

important hormone.


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Alpha () cellsreleaseglucagon,

essential for

controlling bloodglucose levels.

When blood glucose

levels fall, cells

the amount of

glucagon in the blood .

The surge of glucagon

stimulates the liver to

release glucose stores

(from glycogen andadditional storage

sites).

Also, glucagonstimulates the liver to

manufacture glucose -

gluconeogenesis.


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Beta Cells () releaseinsulin (antagonistic to

glucagon).

Insulin the rate atwhich various body

cells take up glucose.

Thus, insulin lowersthe blood glucose

level.

Insulin is rapidly

broken down by the

liver and must be

secreted constantly.

Delta Cells ()producesomatostatin,

which inhibits bothglucagon and insulin.


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Adrenal Glands

2 small glands that sit

atop both kidneys.

Each has 2 divisions,

each with different

functions.

the Adrenal Medulla

secretes the

catecholamine

hormonesnorepinephrineand

epinephrine (closely

related to the

sympathetic

component of the

autonomic nervous

system).


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The Adrenal Cortex

secretes 3 classes of

hormones, all steroid

hormones:

gluticocorticoids

mineralocorticoids

androgenic hormones

One at a time gluticocorticoids:

accounts for 95% of

adrenal cortex

hormone production

the level of glucosein the blood

Released in response to

stress, injury, orserious infection - like

the hormones from the

adrenal medulla.


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Mineralocorticoids:

work to regulate the

concentration of

potassium and sodiumin the body.

Prolonged in

adrenal cortex

hormone results inCushings Disease.

Signs & Symptoms of

Cushings Disease:

in blood sugar levels unusual body fat

distribution

rapid mood swings


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And - if there is an in mineralocorticoids

as well

A serious electolyte

imbalance will occur

due to the potassiumexcretion by the

kidney, which resultsin hypokalemia.

Sodium can also be

retained by the kidney,

resulting in

hyponatremia. Causes:

dysrhythmias

coma

death usually results from a

tumor - TX? Removal

of tumor.


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Gonads and Ovaries:

the endocrine glands

associated with human

reproduction. Female ovaries

produce eggs

Male gonads produce

sperm

both have endocrine

functions.

Ovaries:

located in the

abdominal cavity

adjacent to the uterus. Under the control of

LH and FSH from the

anterior pituitary they

manufacture estrogen

protesterone


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Estrogenand

Progesteronehave

several functions,

including sexualdevelopment and

preparation of the

uterus for implantation

of the egg.

Testes:

located in the scrotum

produce sperm for

reproduction

manufacture

testosterone -

promotes male growth

and masculinization

Controlled by anterior

pituitary hormones

FSH and LH.


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Endocrine

Emergencies:

Diabetes Mellitus

one of the most

common diseases in

North America.

insulin secretion bythe Beta () cells ofthe islets of

Langerhans in the

pancreas.

Complications of

Diabetes:

contributes to heart

disease

stroke

kidney disease

blindness


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Pathophysiology of

Diabetes:

Glucose Metabolism

Glucose (dextrose) is a

simple sugar required

by the body to produce

energy.

Sugars, or

carbohydrates, are 1 of

3 major food sources

used by the body.

The other 2 major

food sources are

proteins

fats

Most sugars in the

human diet are

complex and must bebroken down into

simple sugars:

glucose, galactose and

fructose - before use.


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Breakdown of sugars

is carried out by

enzymes in the gastro

intestinal system. As simple sugars, these

are absorbed from the

GE system into the

body.

More than 95% enter

the body as glucose.

To be converted into

energy, glucose must

first be transmitted

through the cellmembrane. BUT - the

glucose molecule is

large and doesnt

readily diffuse through

the cell membrane.


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Glucose must pass

into the cell by

binding to a special

carrier protein on thecells surface.

Facil i tated dif fusion -

doesnt use energy.

The carrier proteinbinds with the glucose

and carries it into the

cell.

The rate at which

glucose can enter the

cell is dependent upon

insulin levels. Insulin serves as the

messenger - travels via

blood to target tissues.

Combines with specific

insulin receptors on the

surface of the cell

membrane.

Documents

Endocrine To IGCSE Biology