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.