1 30 12 A sagittal cut exposes the dorsal cavity Endocrine system and CNS bring the body back to homeostasis the regulate the body Physiology function of the body parts Function refers to the biochemical reactions occurring inside the cells of the body The function of a part of the body depends on the structure of the part Structure the makeup cell type and tissue type Structure defines function The cellular make up tissue make up of an organ dictates the function of that organ Will see this theme over and over In the human body there are 11 organ systems Human body exhibits structural complexity The lowest level of structural complexity is the chemical level where biochemical reactions result in the function of the body parts The next level of structural complexity is the cellular level Cells are the structural units of organisms Cells are the smallest structures in which biomechanical reactions occur The next level of structural complexity is the tissue level Most cells in the body aggregate to form tissues A tissue is composed of similar cells placed together to form sheet like structures with specific functions 4 primary types of tissues 1 epithelial 2 connective 3 muscle 4 nervous the next level of structural complexity is the organ system level organ system consists of at least 2 organs that function in a complementary way to bring about a desired effect in the human body 11 organ systems in a human the next level of structural complexity is the organism the organism human exists when 11 organ systems work in unison to sustain he organism Results in homeostasis relatively constant environment maintained by the 11 organ systems even though the external environment is changing A homeostatic imbalance is one at least 1 organ system is not functioning properly If not corrected by internal regulatory systems endocrine and nervous it leads to a diseased state A diseased state is referred to as a pathophysiology Endocrine system long time to kick in but long lasting Nervous system kicks in quickly but short lived The first and the lowest level of structural complexity is the chemical level The basis of biochemical reactions in the human body basis for all biochemical reactions is for atoms to achieve stability by having a complete outermost valence shell orbit The atomic nucleus is composed of 2 subatomic particles Neutrons and protons In the shells the subatomic particles called electrons orbit around the atomic nucleus Every atom has an atomic number refers specifically to the number of protons in the atomic nucleus in the atom Because atoms have no charge the atomic number also equals number of electrons The number of protons must equal the number of electrons for the charge to remain zero
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