LP 4- Tissue Level Organization (Muscle & Nervous Tissue)

Muscle

• is contractile, conductive, elastic, extensible, and excitable

• produces movement when stimulated to contract

• is well vascularized

• three types: skeletal, cardiac and smooth

Skeletal muscle tissue

• also known as striated or voluntary muscle tissue

• primarily used for movement of the skeleton (also moves some nonskeletal structures such as the skin of the face and composed the external urethral and external anal sphincters)

• functions in thermoregulation

• is composed of long, cylindrical celled skeletal muscle fibers

• only contracts when stimulated by somatic (voluntary) nervous system

• has reduced ability to repair itself through cell division

Skeletal muscle fibers

• long cylindrical cells that compose the muscle tissue

• are parallel bundles that extend the length of the entire muscle

• is multinucleated to carry out all cellular functions, nuclei is located at the periphery of the fiber

• have striations

Cardiac muscle tissue

• is confined to thick middle layer of the heart wall called the myocardium

• responsible for the pumping action of the heart to move blood through the cardiovascular system (heart and blood vessels)

• is composed of short cells that are bifurcated (branched)

• contains one or two centrally located nuclei

• cells are connected by intercalated discs

• is involuntary, pacemaker cells in the heart initiates the contraction

• has minimal capacity for regeneration

• have striations

Intercalated discs

• intercellular junctions between the cells composed of desmosomes and gap junctions

• appear as dark, thick lines when viewed with light microscopy

• strengthen the connection between cells and promote rapid conduction fo electrical activity through many cells at once, allowing cells of a heart chamber to contract as a unit

Smooth muscle tissue

• also called visceral or involuntary muscle tissue

• lacks striations

• cells are fusiform (spindle-shaped), thick in the middle and tapered at the ends. they are short and contain on centrally located nucleus

• found in the wall of most viscera (internal organs), such as intestines, stomach airways, urinary bladder, uterus and blood vessels

• also found in specialized structures where involuntary muscle contraction is required such as the iris of the eye

• can engage in cell division to provide growth and healing of the tissue

Nervous tissue

• located in the brain, spinal cord and nerves that transverse through the body

• consists of cells such as neurons and glial cells

• is well vascularized

Neurons

• a cell of the nervous system that receive, process and relay nerve impulses

• are the longest cells in the body

• has a prominent cell body that house both the nucleus and other organelles

  • have branches that extend from the cell body called nerve cell processes

  • have shorter and more numerous processes called dendrites

  • has a single long process extending from the cell body called the axon

Glial cells

• are supporting cells

• do not relay nerve impulses, it is responsible for the protection, nourishment and support of the neurons

Dendrites

• process on a neuron

• receive incoming signals and transmit the information to the cell body

axon

• relay nerve impulses to other cells

• process of a neuron that propagates nerve signals away from the cell body