Clinical Uses of Reflexes

Since normal reflexes depend on normal neuron functions, reflexes are commonly used to obtain information concerning the condition of the nervous system.

An anesthesiologist, for instance, may try to initiate a reflex in a patient who is being anesthetized in order to determine how the anesthetic drug is affecting nerve functions. Also, in the case of injury to some part of the nervous system, various reflexes may be tested to discover the location and extent of the damage.

If any portion of a reflex arc is injured, the normal characteristics of that arc are likely to be altered. For example, a plantar reflex is normally initiated by stroking the sole of the foot, and the usual response includes a flexion of the foot and toes.

However, in persons who have suffered damage to certain nerve pathways (corticospinal tract) there may be an abnormal response called the Babinski reflex.

In this case the reflex response is plantar extension, in which the great toe extends upward and the smaller toes fan apart. If the injury is minor, the response may consist of plantar flexion with failure of the great toe to flex, or plantar flexion followed by plantar extension.

The Babinski reflex is, however, present normally in infants up to the age of 12 months and is thought to reflect a degree of immaturity in their corticospinal tracts.

Other reflexes that may be tested during a neurological examination include the following:

Biceps-jerk reflex

This reflex can be elicited by bending a person's arm at the elbow. The examiner's finger is placed on the inside of the bent elbow over the tendon of" the biceps muscle, and the finger is tapped. The biceps contracts in response, and the forearm is flexed at the elbow.

Triceps-jerk reflex

This reflex can be caused by flexing a person's arm at the elbow and tapping the short tendon of the triceps muscle close to its insertion near the tip of the elbow. The muscle contracts in response, and the forearm is extended slightly.

Abdominal reflexes

These reflexes occur when the examiner strokes the skin of the abdomen. For example, a dull pin may be drawn from the sides of the abdomen upward toward the midline and above the umbilicus. Normally, the abdominal muscles underlying the skin contract in response, and the umbilicus is moved toward the region that was stimulated.

Ankle-jerk reflex

This reflex is elicited by tapping the Achilles tendon just above its insertion on the calcaneus. The response is plantar flexion, produced by contraction of the gastrocnemius and soleus muscles.

Cremasteric reflex

This reflex is obtained in males by stroking the upper inside of the thigh. As a result, the testis on the same side is elevated by contracting muscles.

Anal reflex

This reflex is elicited by stroking the skin surrounding the anus. The anal sphincter muscles contract in response.

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Different types of Body Membrane Summary Notes

Two or more kinds of tissues grouped together and performing specialized functions constitute an organ. Thus, the sheetlike structures called membranes that cover body surfaces and line body cavities are organs.

Types of Membranes

Different types of membranes

There are four major types of membranes:

1. Serous membrane
2. Mucous membrane
3. Cutaneous membrane
4. Synovial membrane

Usually these structures are relatively thin. Serous, mucous, and cutaneous membranes are composed of epithelial tissue and some underlying connective tissue; synovial membranes are composed entirely of connective tissue.

Serous membranes

Serous membranes line the body cavities that lack openings to the outside. They form the inner linings of the thorax and abdomen, and they cover the organs within these cavities. Such a membrane consists of a layer of simple squamous epithelium (mesothelium) covering a thin layer of loose connective tissue. It secretes a watery serous fluid, which helps to lubricate the surfaces of the membrane.

Mucous membranes

Mucous membranes line the cavities and tubes that open to the outside of the body. These include the oral and nasal cavities and the tubes of the digestive, respiratory, urinary, and reproductive systems. Mucous membrane consists of epithelium overlying a layer of loose connective tissue; however, the type of epithelium varies with the location of the membrane. For example, stratified squamous epithelium lines the oral cavity, pseudostratified columnar epithelium lines part of the nasal cavity, and simple columnar epithelium lines the small intestine. Mucous membrane secretes the thick fluid called mucus.

Cutaneous membrane

The cutaneous membrane is an organ of the integumentary system and is more commonly called skin.

"Subcutaneous injections are administered into the layer beneath the skin. Intradermal injections, on the other hand, are injected between layers of tissues within the skin. Subcutaneous injections and intramuscular injections, which are administered into muscles, are sometimes called hypodermic injections".

Synovial membranes

Synovial membranes form the inner linings of joint cavities between the ends of bones at freely movable joints. These membranes usually include fibrous connective tissue overlying loose connective tissue and adipose tissue. They secrete a thick, colorless synovial fluid into the joint cavity. This fluid lubricates the ends of the bones within the joint.

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Interleukin

Name	Source	Target Receptor	Target Cells	Functions	Recent Research
Interleukin 1	Macrophages,  B cells, Monocytes, Dendritic Cells	CD121a/IL1R1, CD121b/ILR2	T helper cells	Co-stimulation
			B cells	Maturation & Proliferation
			NK cells	Activation
			Macrophages, endothelium or other	Inflammation, small amount induce acute phase reaction, large amounts induce fever	IL-1 can itself produce hyperalgesia as assessed by tailflick to radiant heat
Interleukin 2	Th - 1 Cells	CD25/IL2RA, CD122/IL2RB, CD132/IL2RG	Activated T cells, B cells, NK cells, macrophages, oligodendrocyte	- Stimulate growth and differentiation of T cell response.  - Can be used in immunotherapy to treat cancer or suppressed or transplant patients	High dose IL-2 produce durable responses in some patients with metastatic melanoma and should be considered a therapeutic option for appropriately selected patients with his disease. IL-2 released by lung T Cells in inactive pulmonary sarcoidosis
Interleukin 3	Activated T helper cells, mast cells, NK cells, endothelium, eosinophils	CD123/IL3RA, CD131/IL3RB	Hematopoietic stem cells	Differentiation and proliferation of myeloid progenitor cells Eg - erythrocytes & granulocytes	IL-3 supports growth of mouse pre B Cell clones in-vitro.
			Mast cell	Growth & histamine release
Interleukin 4	Th - 1 cells, activated naive CD4+ cell, memory CD4+ cells, mast cells, macrophages	CD124/IL4R, CD132/IL2RG	Activated B cells	Proliferation & differentiation, Ig G1 and Ig E synthesis. Important role in allergic response (Ig E)	Systemic sclerosis
			T cells	Proliferation
Interleukin 5	Th -2 cells, mast cell, eosinophils	CD125/IL5RA, CD131/IL3RB	Eosinophils	Production
			B Cells	Differentiation, Ig A production
Interleukin 6	Macrophages, Th - 2 cells, B cells, astrocytes, endothelium	CD126/IL6RA, CD130/IL6RB	Activated B cells	Differentiation into plasma cells
			Plasma cells	Antibody secretion
			Hematopoietic stem cells	Differentiation
			T Cells or Other	Induce acute phase reaction, hematopoiesis, differentiation, inflammation
Interleukin 7	Bone marrow, stromal cells & thymus stromal cells	CD127/IL7RA, CD132/IL2RG	Pre/pro- B cell, Pre/pro- T cell, NK cells	Differentiation and proliferation of lymphoid progenitor cells, involved B, T and NK cells survival, development and homeostasis, increase pro-inflammatory, cytokine	Show effect on T cells homeostasis

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