Muscular tissues

• Myofibrils are the contractile units within muscle fibers and consist of actin filaments (thin filaments) and myosin filaments (thick filaments).
• Tissues are groups of closely associated cells with similar structure and function.
• If barriers are penetrated, the body initiates inflammatory & immune responses, mainly within connective tissues.
• There are four primary animal tissues types: Epithelial, Connective, Nervous, and Muscular.
• Most organs contain several tissue types.
• The arrangement of tissues determines the structure and function of the organ.
• Muscle tissue is specialized for contraction and produces all body movement.
• There are three types of muscle tissues: Skeletal muscle tissue, Cardiac muscle tissue, and Smooth muscle tissue.
• Skeletal muscle tissue consists of large body muscles responsible for movement.
• Cardiac muscle tissue is found only in the heart.
• Smooth muscle tissue is found in walls of hollow, contracting organs such as blood vessels, urinary bladder, respiratory, digestive, and reproductive tracts.
• Muscle tissue can be classified as striated (muscle cells with a banded appearance) or nonstriated (not banded; smooth).
• Muscle cells can have a single nucleus or can be multinucleate.
• Muscle cells can be controlled voluntarily or involuntarily.
• Skeletal muscle cells are long and thin, usually called muscle fibers, and do not divide.
• New fibers are produced by stem cells (myosatellite cells) in skeletal muscle tissue.
• Cardiac muscle cells, called cardiocytes, form branching networks connected at intercalated discs and are regulated by pacemaker cells.
• Smooth muscle cells are small and tapered, can divide and regenerate, and are found in walls of hollow internal organs.
• Epithelium tissue is found in different areas of the body such as body coverings & linings, glandular tissue, and is responsible for functions like protection, absorption, filtration, and secretion.
• Epithelium tissue can be classified as striated (muscle cells with a banded appearance) or nonstriated (not banded; smooth).
• Epithelial cells are composed almost entirely of cells, fit closely together, form a continuous sheet bound to adjacent cells by lateral contacts, and are avascular.
• Connective tissue consists of living cells in a secreted matrix, examples include bone, cartilage, blood, and is found everywhere in the body.
• Transmission of a signal involves knocking down line of dominoes by tipping first one, propagating signal, resetting system, and re-setting axon.
• At the end of the axon, an impulse has to jump the synapse, a junction between neurons, which has to hop quickly from one cell to the next.
• Connective tissue provides protection, binds body tissues together, and supports the body.
• Three types of neurons based on the direction in which information is sent: Sensory (afferent) neuron, Motor (efferent) neuron, Interneuron.
• Connective tissue consists of two types: Connective Tissue Proper (CTP) which includes skin, adipose tissues, and dense CT which includes collagenous fibers in tendons and ligaments.
• Cartilage is a type of connective tissue that includes collagenous fibers embedded in chondroitin sulfate, examples include Hyaline cartilage, Elastic cartilage, and Fibrocartilage.
• Neural tissue is specialized for conducting electrical impulses, rapidly senses internal or external environment, processes information and controls responses.
• Neural tissue is found in the brain, spinal cord, nerves.
• Bone or Osseous Tissue is strong and resists shattering, it is made up of calcified calcium salt deposits and flexible collagen fibers.
• Neurons are nerve cells that perform electrical communication.
• Body has many ways to protect itself: Mechanical barriers such as skin and mucosae, and ciliary action, and Chemical barriers such as strong acid produced by stomach glands.
• Neuroglia are supporting cells that repair and supply nutrients to neurons, do not transmit impulses, support activities of the neuron.
• Bone Cells or Osteocytes are arranged around central canals within matrix, have small channels through matrix (canaliculi) that access blood supply.
• Chemical synapse involves events at synapse: action potential depolarizes membrane, opens Ca++ channels, neurotransmitter vesicles fuse with membrane, release neurotransmitter to synapse, neurotransmitter binds with protein receptor, ion-gated channels open, neurotransmitter degraded or reabsorbed.
• Axon is coated with Schwann cells which protects and insulates axon, speeds signal, and facilitates saltatory conduction.
• Periosteum covers bone surfaces, is a fibrous layer, and a cellular layer.
• Simple squamous epithelia are found in the mesothelium, which lines body cavities, and in the endothelium, which lines heart and blood vessels.
• Adhesion junctions (Desmosomes) are anchoring junctions that prevent cells subjected to mechanical stress from being pulled apart.