Bodys Internal Clock Pineal Gland

Published Date: 02 Nov 2017

Released: Melatonin

Function: Regulates the body’s internal clock responding

to light and dark as well as sleep/wake rhythms. Melatonin can also have an inhibitory effect on the sexual glands by decreasing simulation of these organs (K Saladin, 2004).

D) Thyroid

Released: Thyroxine (T4) and triiodothyronine (T3)

Function: Regulates growth and development.

They also help maintain our body’s core temperature and metabolic levels

(http://www.medadvocate.net/complimentary/ThyroidFunctionOverview.pdf, 2009)

Released: Calcitonin

Function: Decreases rate of bone breakdown,

It also prevents large increase in blood

calcium levels (C. Brown, 2001)

E) Parathyroids

Releases: Parathyroid (PTH)

Function: Increases rate of bone breakdown by

Osteoclasts. Increases vitamin D

synthesis, essential for

maintenance of normal blood

calcium levels (K Saladin, 2004).

F)Thymus

Release: Thymosim

Function: helps in the development of certain white blood cells,

called T cells. T cells help protect the body against infection

by foreign organisms. The thymus gland is most important

in childhood, becoming smaller in the adult (P. Raven; G. Johnson, 2002)

G) Adrenal cortex:

Released: Glucocorticoids (cortisol)

Function: Raise blood glucose level, stimulate breakdown of protein and increases blood concentration of amino acids. It also promotes the release of fatty acids from adipose tissue (P. Raven; G. Johnson, 2002).

Released: Mineralocorticoids (aldosterone)

Function: stimulates the exchange of sodium and potassium by reabsorbing sodium and excreting potassium. (http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/index.html, 2010).

Released: Sex hormones

Function: Stimulate reproductive organs and bring about sex characteristics (K Saladin, 2004).

Adrenal medulla:

Released: Epinephrine (adrenaline) and norepinephrine (noradrenaline)

Function: in situations of fear or stress Epinephrine and norepinephrine can be released this causes an Increase in heart rate, widening of blood vessels (increasing blood flow), widening of bronchi and a breakdown of glycogen to glucose, this in turn raises the blood sugar level increasing power and stamina. Metabolic rate also increases

.( http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/index.html, 2010).

H) Pancreas:

Released: Insulin

Function: secreted by the beta cells of the pancreas in situations of high blood sugar. It allows muscles, red blood cells and fat to take in excess glucose from the blood, Lowering blood glucose levels. It also promotes formation of glycogen (C. Brown, 2001).

Released: Glucagon

Function: if the blood sugar level in the body is low glucagon is released from the alpha cells in the pancreas, causing the liver to release stored glucose, Raising the blood glucose level (C. Brown, 2001).

I) Testes:

Released: Androgens (testosterone)

Function: responsible for the growth and development

of the male reproductive organ, muscle enlargement,

growth of body hair, voice changes, and sex

drive (P. Raven; G. Johnson, 2002).

J) Ovaries:

Released: Estrogens and progesterone

Function: development and function of female reproductive organs

and other female sexual characteristics. These characteristics

include enlargement of the breasts and distribution of fat,

which influences the shape of the hips, breasts, and legs. The

female menstrual cycle is controlled by the cyclical release of

estrogen and progesterone from the ovaries.(http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/index.html, 2010)

Task 2

1)

The adrenal medulla secretes two major hormones: epinephrine

(adrenaline), 80%, and norepinephrine (noradrenaline) 20%. as well as a trace of dopamine (K Saladin, 2004). The adrenal cortex secretes three hormone types: mineralocorticoids which include aldosterone.

Glucocorticoids which include cortisol and cortisone

As well as androgens (sex hormones like testosterone or androsterone) (K Saladin, 2004).

2)

Catecholamines such as epinephrine/adrenaline and nophrephenine/noradrenaline, bind to receptors on the heart, arteries, pancreas, liver, muscles and fatty tissue.

The main overall effect is an increase alertness and stamina during situations of fear stress or danger. Epinephrine/adrenaline and nophrephenine/ noradrenaline, have certain different physiological functions as shown in the table below (C. Brown, 2001)

Function Affected

Epinephrine

Norepinephrine

heart

Rate increases

Force of contraction increases

Rate increases

Force of contraction increases

Blood vessels

Vessels in skeletal muscle widen

decreasing resistance to blood flow vessels

Blood flow to skeletal muscles increases

resulting from constriction of blood,

in skin and viscera

Systemic blood pressure

Some increase

Great increase due to vasoconstriction, output counteracted in muscle blood vessels during

airways

Dilated

Some dilation

Reticular formation of brain

Activated

Little effect

liver

Promotes breakdown of glycogen to glucose, increasing blood sugar level

Little effect on blood sugar

Metabolic rate

increases

increases

(P. Raven; G. Johnson, 2002)

2b)

Physiologic Effects of Mineralocorticoids

Mineralocorticoids help regulate sodium and potassium in the body. A lack of these hormones can be life threatening, due to abnormalities in electrolyte and fluid balance(S. Mader, 2003).

Aldosterone is the most important mineralocorticoid, The major target of Mineralocorticoids and in particular aldosterone is the kidney, where it stimulates the exchange of sodium and potassium, it does this in three ways

1) Increases absorption of sodium and therefore less sodium is lost in urine

2) Increases absorption of water, which in turn aids sodium absorption as there is more fluid inside the body causing an osmotic effect.

3) Increases excretion of potassium via the kidney

Aldosterone also has effects on sweat glands, salivary glands and the colon which all aid with the retention of sodium (S. Mader, 2003).

Physiological Effects of Glucocorticoids

Cortisol (hydrocortisone) is a glucocorticoid, which means it affects glucose metabolism.

In addition to affecting glucose, cortisol influences protein and fat metabolism.

cortisol inhibits the synthesis of protein in various tissues, and increases blood concentration of amino acids.

It promotes the release of fatty acids from adipose tissue, increasing the use of fatty acids as an energy source and decreasing the use of glucose as an energy source.

It stimulates liver cells to synthesize glucose from noncarbohydrates (gluconeogenesis), such ascirculating amino acids and glycerol, thus

increasing blood glucose concentration. Cortisol’s actions help keep the blood glucose concentration within the normal range between meals. These

actions are important because just a few hours without food can exhaust liver glycogen, another major source of glucose (P. Raven; G. Johnson, 2002).

Cortisol also relieves pain by

• decreasing permeability of capillaries, preventing

leakage of fluids that swell surrounding tissues

• stabilizing lysosomal membranes, preventing

release of their enzymes, which destroy tissue

• inhibiting prostaglandin synthesis (P. Raven; G. Johnson, 2002).

3)

When the brain perceives an environment as threatening, stressful or exciting, the hypothalamus signals to the adrenal glands to produce adrenaline. Adrenaline is produced in the adrenal medulla. The adrenal gland is located on top of the kidney (S. Mader, 2003). The adrenal medulla converts tyrosine into dopamine. When dopamine receives oxygen it turns into noradrenaline this is then converted to adrenaline. Adrenaline binds to receptors on the heart, arteries, pancreas, liver, muscles and fatty tissue. This in turn Increases the heart rate, widens the blood vessels (increasing blood flow), widens the of bronchi and a breaks down glycogen to glucose, this in turn raises the blood sugar level providing energy/fuel in a flight or fight situation. Metabolic rate also increases (P. Raven; G. Johnson, 2002)

Task 3

1) 99% of calcium ions (Ca2_) in the body is contained in the bones and teeth. The remaining 1% (around 1.5 gramms) is contained in the blood. The blood calcium levels are regulated by hormones and kept within the range of 9mg/100ml to 11mg/100ml. if the blood calcium levels rise above 11mg/100ml in the blood its termed hypercalcemia. (P. Raven; G. Johnson, 2002)

Hypocalcemia increases the permeability of plasma membranes to Na. As a result,

nerve and muscle tissues can undergo spontaneous action. Hypercalcemia prevents normal depolarization

of nerve and muscle cells. High levels of Ca2 levels cause the

deposits of calcium carbonate salts in soft tissues to build up, causing irritation and inflammation.

When the calcium levels rise, the thyroid gland releases Calcitonin,

this reduces Ca2 levels. (S. Mader, 2003)

Bones can also play a role in reducing blood calcium levels, by inhibiting calcium from bone into the blood (http://www.abpischools.org.uk/page/modules/hormones/horm7.cfm?coSiteNavigation_allTopic=1, 2012)

2)

When the blood calcium levels drop below 9mg/100ml it is termed Hypocalcemia . Hypocalcemia means an increase in the permeability of plasma membranes to Na. As a result, nerve and muscle tissues can undergo spontaneous action. As a result the para- thyroid gland secretes parathyroid hormone (PTH) resulting in increased numbers of osteoclasts, which causes increased bone breakdown allowing more calcium to enter the blood, raising calcium levels (S. Fox, 2004).

PTH also regulates blood calcium levels by increasing calcium

uptake in the small intestine Increased PTH

promotes the formation of vitamin D in the kidneys, and vitamin

D increases the absorption of calcium from the small intestine.

PTH also increases the reabsorption of calcium from urine in the

kidneys, which reduces calcium lost in the urine (S. Fox, 2004).

3)

Stretching of the uterine and vaginal tissues towards the end of a pregnancy during labour

initiates nerve impulses to the hypothalamus. The hypothalamus signals the posterior pituitary gland to release the hormone oxytocin. Oxytocin promotes uterine contractions. As the fetus is pushed more against the cervix, more oxytocin is released in a continuous positive feedback cycle Combined with the greater excitability of the myometrium due to the decline in

progesterone secretion, oxytocin aids labor in its later

stages. (P. Raven; G. Johnson, 2002)

Oxytocin promotes uterine contractions in two ways.

Oxytocin stimulates the release of prostaglandin E2 and prostaglandin F2a in fetal membranes by activation of phospholipase C. The prostaglandins stimulate uterine contractility.

Oxytocin can also directly induce myometrial contractions through phospholipase C, which in turn activates calcium channels and the release of calcium from intracellular stores. (S. Fox, 2004).

Task 4

1)

The Anterior Pituitary (Adenohypophysis)

Produces the following hormones, Prolactin, Follicle-stimulating hormone (FSH), Luteinizing hormone (LH), Melanocyte hormone (MSH), Beta Endorphins, Lipotropins , Adrenocorticotropic hormone (ACTH), Thyroid-stimulating hormone (TSH) and Growth hormone (GH) (S. Mader, 2003).

The Posterior Pituitary (Neurohypophysis), produces, Antidiuretic hormone(ADH) and oxytocin (S. Mader, 2003).

2a)

Posterior Pituitary (Neurohypophysis)

ADH ADH promotes the retention of water

by the kidneys so that less water is excreted in the urine

and more water is retained in the blood.

oxytocin stimulates contractions of

the uterus during labor.

Oxytocin also stimulates the mammary gland to contract, which

results in the milk-ejection in lactating woman. In

men, a rise in oxytocin secretion at the time of ejaculation

has been measured, but the physiological significance of

this hormone in males remains to be demonstrated.

2b)

Anterior Pituitary (Adenohypophysis)

GH acts on the liver, stimulating it to produce another hormone called growth factors. It is this second hormone, which directly affects the growth of bone and muscle.

GH also increases glycogen synthesis, blood glucose levels and somatomedin production

TSH simulates thyroid hormone secretion

ACTH ACTH binds to membrane-bound receptors on cells of the adrenal cortex

and stimulates the secretion of glucocorticoids

Lipotropins increase fat breakdown

Beta Endorphins help with pain relief in the brain and also inhibition of gonadotropin

releasing hormone secretion

MSH function is to increase melanin production in melanocytes to make

the skin darker in color

LH simulates Ovulation and progesterone production in ovaries; testosterone synthesis and support for sperm cell production in testes

FSH simulates Follicle maturation and estrogen secretion in ovaries as well as sperm cell production in testes

Prolactin simulates Milk production in lactating women however it has an unclear physiological effect in males

3a)

Antidiuretic hormone (ADH), is secreted by the posterior pituitary gland.

The release of ADH from the posterior pituitary is regulated

by the hypothalamus. Certain cells of the hypothalamus

are sensitive to changes in the solute concentration of the

fluid within the hypothalamus. An increased solute

concentration of the blood and fluid results in messenger hormones being sent along the axons of the ADH secreting

neurons of the hypothalamus to the posterior pituitary,

causing ADH to be released from the ends of the axons

A reduced solute concentration in the blood

and interstitial fluid within the hypothalamus causes inhibition

of ADH release.

Baroreceptors that monitor blood pressure also influence

ADH secretion. Increased blood pressure causes a decrease

in ADH secretion, and decreased blood pressure increases

ADH secretion

3b)

When the brain receives signals of stress, the hypothalamus releases . Corticotrophin which travels down the hypothalamohypophysial portal system, to the anterior pituitary gland.

In the anterior pituitary CRH binds to and stimulates cells that secrete

adrenocorticotropic hormone (ACTH). During this process several other hormones are also created such as lipoproteins, Beta-endorphins, Met-enkephalins and Melanocyte-stimulating hormone (MSH)

ACTH is then released into the blood stream and attaches to the adrenal gland, simulating the adrenal cortex to secrete glucocorticoids such as cortisol. It doesn’t control aldosterone (the other hormone secreted by the adrenal cortex)

Cortisol inhibits CRH and ACTH secretion. And is thus called a negative feedback loop (http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/hypopit/acth.html, 2012)

4)

Hypothalamic Control of the Posterior Pituitary

Both of the posterior pituitary hormones—ADH

and oxytocin, are actually produced in neuron cell bodies of the

supraoptic nuclei and paraventricular nuclei of the hypothalamus.

These nuclei within the hypothalamus are thus endocrine

glands. The hormones they produce are transported along axons

of the hypothalamo-hypophyseal tract to the posterior

pituitary, where they are stored and later released. The posterior

pituitary is thus more a storage organ than a producing gland.

The release of ADH and oxytocin from the posterior pituitary

is controlled by neuroendocrine reflexes. In nursing

mothers, for example, the mechanical stimulus of suckling acts,

via sensory nerve impulses to the hypothalamus, to stimulate the

reflex secretion of oxytocin. The secretion of ADH

is stimulated by osmoreceptor neurons in the hypothalamus in

response to a rise in blood osmotic pressure; its secretion

is inhibited by sensory impulses from stretch receptors

in the left atrium of the heart in response to a rise in blood volume

Hypothalamic Control of the Anterior Pituitary

The anterior pituitary is not really the master gland, since secretion

of its hormones is in turn controlled by hormones secreted

by the hypothalamus.

Releasing and Inhibiting Hormones

Since axons do not enter the anterior pituitary, the hypothalamus

Controls the anterior pituitary with hormones

As appose to neural regulation. Hormones,

produced by the hypothalamus, are transported

to the axon endings in the basal portion of the hypothalamus.

This area has extremerly small blood vessels

The blood vessels that drain the hypothalamus deliver blood

to a second set of blod vessels in the anterior pituitary. Since these blood vessles below the blood vessels in the hypothalamus, the recieve and receives deoxygenated blood from it, the vascular

link between the outer part of the hypothalamus and the anterior pituitary

forms a portal system. The vascular link between the hypothalamus

and the anterior pituitary is thus called the hypothalamohypophyseal

portal system.

Regulatory hormones are secreted into the hypothalamohypophyseal

portal system by neurons of the hypothalamus. These

hormones regulate the anterior pituitary. Thyrotropin releasing hormone (TRH)

stimulates the secretion of TSH.

corticotropin-releasing hormone

(CRH) stimulates the secretion of ACTH from the anterior

pituitary. A single releasing hormone, gonadotropin-releasing

hormone, or GnRH, stimulates the secretion of both gonadotropic

hormones (FSH and LH) from the anterior pituitary.

Prolactin and the growth hormone from the (anterior

Pituitary) is regulated by hormones,

known as prolactin-inhibiting hormone (PIH) and somatostatin.

A specific growth hormone-releasing hormone (GHRH)

( R. Seeley, D. Stephens, P. Tate, 2001)