Modes of hormone delivery

Endocrine: most common, classical mode, hormones delivered to target cells by blood.
Paracrine: hormone released diffuses to its target cells through immediate extracellular space. Blood is not directly involved in the delivery.

Neuroendocrine: hormone is produced and released by a neuron., delivered to target cells by blood.

Autocrine: hormone released feeds-back on the cell of origin, again without entering blood circulation.


HORMONE TARGET CELL SPECIFICITY

Only target cells, or cells that have specific receptors, will respond to the hormone’s presence. The strength of this response will depend on:
-blood levels of the hormone. – the relative numbers of receptors for that hormone on or in the target cells.
The affinity (or strength of interactions) of the hormone and the receptor.


Half-life onset and duration of hormone activity..

The affinity of hormones to their specific receptors is typically very high. The actual concentration of a circulating hormone in blood at any time reflects. – its rate of release – the speed of its inactiviation and removal from the body.

The half –life is the time required for the hormone to loose half of its original effectiveness(or drop to half of its orginal concentration)

The time required for hormone effects to take place varies greatly, from almost immediate responses to hours or even days.

In addition, some hormones are produced in an inactive form and must be activated in the target cells before exerting cellular responses.

In terms of duration of hormone action, it ranges from about 20 minutes to several hours, depending on the hormone.

CONTROL OF HORMONE RELEASE:

The synthesis and secretion of most hormones are usually regulated by negative feedback systems. As hormone levels rise, they stimulate target organ responses. These in turn, inhibit further hormone release. The stimuli that induce endocrine glands to synthesize and release hormones belong to one of the following major types.
Humoral
Neural
Hormonal

The endocrine system works closely with the nervous system to maintain and steady state of the body.the functions of hormones. Endocrin gland is ductless gland. Target issue. Chemical structure of hormones: protein, peptide, aminoacid derived and steroid hormones. Pheromones

Histology of Integument Video

Video of basic histology , Histology of Integument

integumentary slides

Integumentary system info

intergumentary system videos and parts

Another Video of the Integumentary System, again these are some study notes & pictures to share with classmates who may benefit from them. Video is very nice and good details.

Integumentary System video

intergumentary system video and very simple integumentary system clip. very usefull for students and learners. Basic integumentary system parts explaining in this video.

The Integumentary System song

very good song about intergumentary system :) integumentary system video song ..

the skin

The skin is an important sense organ, and as such includes a number of nerves that are mainly in the dermis, with a few reaching the epidermis. Nerves carry impulses to and from hair muscles, sweat glands, and blood vessels, and receive messages from touch, temperature, and pain receptors. Some nerve endings are specialized such as sensory receptors that detect external stimuli. The nerve endings in the dermal papillae are known as Meissner's corpuscles, which detect light touch, such as a pat, or the feel of clothing on the skin. Pacinian corpuscles, located in the deeper dermis, are stimulated by stronger pressure on the skin. Receptors near hair roots detect displacement of the skin hairs by stimuli such as touch or wind. Bare nerve endings throughout the skin report information to the brain about temperature change (both heat and cold), texture, pressure, and trauma.