BLOOD and LYMPH

Types of muscles and their differences.

http://www.majordifferences.com/2014/06/difference-betwee
http://www.majordifferences.com/2013/09/difference-between-cardiac-muscle-and.html#.Vdn37SWqqkon-striated-and-non.html

ELEMENTS OF XYLEM ( T.S) ( L.S.)

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Hormones

These are chemical messengers or information molecules which are produced by ductless glands and transported by circulatory system to other parts of body for inducing and coordinating their activities,

Characteristics:

1. These are produced by endocrine glands and poured into circulatory system
2. These act on specific cells , tissues and organs called target sites away from the place of origin.
3. Since these are transported by blood , their action is slow( except adrenaline)
4. These are small sized molecules of diverse origin-proteins, peptides, amino acid, steroids etc.
5. They are effective in very low concentration.
6. They are generally produced in response to a stimulus and are consumed during their activity in target cells.
7. Both their deficiency and excess is harmful.

Glands:

A cell, tissue or an organ that produces a secretion for performing a particular function is called gland. These can be 

1. Exocrine glands:These drain out their secretion through ducts into target sites which are adjacent to the gland. The secretion can be enzymes, mucus, excretory substances etc. Example:gastric glands, milk glands, sweat glands.
2. Endocrine glands: These are isolated glands which do not have ducts for draining out their secretion but put it into blood as their target sites are away from the point of origin.Their secretion comprises of hormones. Eg: Thyroid, pituitary gland.
3. Heterocrine glands: They have both exocrine and endocrine regions.Eg:Pancreas.

REFLEX ACTION

Spontaneous , involuntary and automatic response without the will of the organism.
The word reflex comes from refluxus which means reflected or directed back, which means that the reflex is reflected back from  the spinal cord.
Examples: coughing, sneezing, blinking of eye, salivation when food is eaten, sweating during exercise.
Reflex arc: The pathway taken by a stimulus to travel from receptor organ  to an effector organ.

Reflex arcs have evolved in higher animals for quick action in emergency situation when immediate action is needed for survival.
Reflexes can be put into two categories:

1. Unconditioned or simple or natural reflexes:These are inborn and inherited. Eg: blinking of eye, swallowing.
2. Conditioned or acquired reflexes.: one learns by experienceand gradually responds to it unconsciously.Eg. playing a musical instrument, working on keyboard of a computer,

Watering of mouth at the sight of food or closing of eyes when bright light id focussed on them is a cerebral reflex.
Importance:It checks overloading of the brain, provides immediate response to harmful stimuli and gives the organism a survival value.