Class 1: Axis of rotation is between the force and the load. The biceps curl is an example. Seesaw.
Class 2: Load is between the axis of rotation and the force. The length of the force arm is always longer than the resistance. In most cases, gravity is the resistance, and muscle activity the force. An example is a push-up.
Class 3: The force is between the axis of rotation and the load. The length of the force arm is always shorter than the resistance arm. Shoulder abduction with weight at the wrist is a class 3 lever.
What are the three distinct types of joint classification?
1. Synarthroses (Fibrous)
2. Amphiarthroses (Cartilaginous)
3. Diarthroses (Synovial)
Describe three types of a Synarthrosis joint.
1. Suture (sagittal suture of skull), union of two bones by a ligament or membrane, immovable, and possibility of fusion (synostosis).
2. Syndesmosis (tibia/fibula with interroseous membrane) bone connected to bone by a dense bifrous membrane or cord, very little motion.
3. Gomphosis (tooth in socket) two bony surfaces connected as a peg in a hole, the teeth in the mandible and maxilla are the only gomphosis joints in the body.
Describe two types of a Amphiarthrosis joint.
1. Synchondrosis (sternum and true rib articulation) hyaline cartilage adjoins two ossifying centers of bone, provide stability during growth, may become a synostosis when growth is completed, slight motion.
Symphiysis (pubic symphysis) generally located in the midline of the body, two bones covered in hyaline cartilage, two bones connected by fibrocartilage, slight motion.
Describe three types of a Diarthrosis joint.
1. Uniaxial has one motion around a single axis in one plan of the body. Hinge (ginglymus) elbow joint. Pivot (trochoid) atlantoaxial joint.
2. Biaxial movement occurs in two planes and around two axes through convex/concave surfaces. Condyloid - MCP joint of a finger. Saddle - CMC joint of the thumb.
3. Multiaxial movement occurs in three planes and around three axes. Plane (gliding) - carpal joints. Ball and socket - hip joint.
List the 5 types of joint receptors.
1. Free Nerve Endings
2. Golgi Ligament Endings
3. Mazzoni Corpuscles
4. Pacinian Corpuscles
5. Ruffini Endings
Describe the location, sensitivity and primary distribution of a Free Nerve Ending.