Muscle

Name: Stephanie Castillo
Muscles
* What is the muscle?
Is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Is an organ that can relax andcontract to allow movement, usually in response to a stimulus from the nervous system.

* What is the basic unit of the muscle?
The basic unit of the muscle is the myofibril.

* How is itcomposed?
A threadlike structure composed of complex proteins. Each muscle cell, or fiber, contains several myofibrils, which are composed of regularly arranged myofilaments of two types, thick and thin.* What does the thick and thin myofilaments contain?
* Thick myofilaments: contains several hundred molecules of the protein myosin.
* Thin filaments: contains two strands of the proteinactin.

* What would be the functions for both myofilaments?
The myofibrils are made up of alternating rows of thick and thin myofilaments with their ends interleaved; in muscular contractions,they slide along each other by means of cross bridges that act as ratchets.

* How many types of muscles are there?
There are 3 types of muscles:
* Skeletal Muscles
* Smooth Muscles* Cardiac Muscles
* Describe the smooth Muscle and their functions.
Visceral, or involuntary, muscle is composed of spindle-shaped cells, each having a central nucleus. The cells have no crossstriations, although they do exhibit faint longitudinal striations. Stimuli for the contractions of smooth muscles are mediated by the autonomic nervous system. Smooth muscle is found in the skin,internal organs, reproductive system, major blood vessels, and excretory system.

* Describe the cardiac muscle and their functions.
This muscle tissue composes most of the vertebrate heart. Thecells, which show both longitudinal and imperfect cross striations, differ from skeletal muscle primarily in having centrally placed nuclei and in the branching and interconnecting of fibers. Cardiac...