- The teleoncephelon consist of the cerebral hemisphere, basal nuclei and olfactory bulb.
- In primitive vertebrates, the cerebral hemisphere are mainly involved with olfaction and related motor responses.
- ın higher vertebrates the gray matter of the cerebral hemisferes, except for the basal ganglia is moved to the surface, forming the cerebral cortex.
- In mammals, the cortect forms the majority of the cerebral hemispheres.
- The cortext has convulated surface and many neurons.
Skin: The skin is the most important organ of the body.
Epidermis: are keratinized and dead cells that make the skin waterproof
Dermis: The sweat glands are present in this layer that collect waters and waste products from the blood stream. The hair roots are also present in this layer that help in the growth of hair.
Subcutaneous Layer: body temperature is also maintained within this layer by insulating the body to the temperature fluctuations.
Thermoregulation: with evaporation of the sweat and regulation of the blood flow to the dermis.
Sensations: The cutaneous sensations like touch, pressure, vibration, pain, cold are felt by the skin.
Protection: The protective barrier of the skin helps prevent diseases, infections, dehydration, etc.
Production of Vitamin D: helps in the production of vitamin D
Hair: functions of the hair include protection and sensation to light touch. The hair is made of dead, keratinized cells that are bound together with the extracellular proteins.
Nails: functions : is to help in grasping and holding things. The nails act as counter force and help increase the sensitivity of the fingertip.
Sweat Glands: that have an opening through the skin pores, help in excretion of waste matters from the circulatory system.
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.
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
Video of basic histology , Histology of Integument
Etiketler: basic histology
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.
Etiketler: integumentary system