Inverse Stretch Reflex - Nervous System

 INVERSE STRETCH REFLEX

The more a muscle is stretched, the stronger is its contraction up to a certain point when it suddenly relaxes. This is a result of stimulation of the Golgi ten-don organs , which are networks of nerve endings, located in series, in the tendon of a muscle. Stimulation of the sensory nerve from them inhibits the motor neuron of that muscle and stimu-lates that of the antagonistic muscle. This is the in-verse stretch reflex ortendon reflex(see Figure 5.33), a protective reflex preventing injury to the mus-cle and tearing of tendons from the bone.

Direct stimulation of the alpha motor neuron (in-nervation to the skeletal muscle) and gamma motor neuron and interplay of various reflexes help contract muscle smoothly and control the force and speed of various groups of muscle in a precise manner.


Comments

Post a Comment

Popular posts from this blog

Microorganisms on the Skin

  Microorganisms on the Skin On the integumentary system would not be complete without considering the invisible layer of microorganisms that inhabit the surface of the skin. This huge colony of organisms is the  “normal mi-crobial flora.”  Similar to residents and tourists in acity, there are resident microorganisms (resident flora) that are regularly found in a specific area at a specific age and transient flora that inhabit the skin for hours, days, or weeks. The resident flora play an important part in maintaining health and normal function. Resident flora prevent harmful bacteria from thriving on the skin by directly inhibiting them or competing with them for nutrients. However, resi-dent bacteria can be infective and harmful if they are introduced in large amounts into the bloodstream, which can occur when the skin is injured or when surgery is performed without adequately cleansing the skin surface before incision. They may also be harmful in individuals whose immu...
Read more

Neuroglia

Image
  NEUROGLIA Neuroglias are the supporting cells. They are five times more abundant than neurons. There are four types of glial cells in the CNS: the  ependymal cells, astro-cytes, microglia,  and  oligodendrocytes  and twotypes in the PNS:  Schwann cells,  or  neurolemmo-cytes, and  satellite cells,  or  ganglionic gliocytes. The ependymal cells line the cavities in the brain and spinal cord and are responsible for producing, circulating, and monitoring the cerebrospinal fluid—the fluid inside and around the CNS that cushions and protects the brain. The astrocytes, as the name suggests, are star-shaped. They are present between the blood capillaries and the brain and spinal cord, monitoring the sub-stances that enter and leave the brain and preventing sudden changes in the environment around the CNS. This is the  blood-brain barrier,  and the astrocytes are responsible for its creation. The astrocytes also help at the time...
Read more

Movement in the Colon and Defecation

Image
  Movement in the Colon and Defecation The movement in the colon is similar to the small in-testine in that peristalsis and a segmentation type of contraction are present. In addition, there is a third type of contraction,  mass action  contraction, in which there is simultaneous contraction of the smooth muscle over a large area. This movement pushes material from one portion of the colon to an-other and into the rectum. When the rectum is dis-tended, it initiates the  defecation reflex.  When the pressure increases a little, there is a desire to defe-cate. Beyond a pressure of 55 mm Hg, both the inter-nal and external sphincters relax and the contents of the rectum are expelled. This is the reason for the in-voluntary expulsion seen in infants and individuals with spinal cord injury. In humans, sympathetic stimulation causes contrac-tion of the internal anal sphincter and parasympathetic stimulation relaxation. The external anal sphincter, which is comprised o...
Read more