NEET MDS Lessons
Physiology
|
Damage to Spinal Nerves and Spinal Cord |
||
|
Damage |
Possible cause of damage |
Symptoms associated with innervated area |
|
Peripheral nerve |
Mechanical injury |
Loss of muscle tone. Loss of reflexes. Flaccid paralysis. Denervation atrophy. Loss of sensation |
|
Posterior root |
Tabes dorsalis |
Paresthesia. Intermittent sharp pains. Decreased sensitivity to pain. Loss of reflexes. Loss of sensation. Positive Romberg sign. High stepping and slapping of feet. |
|
Anterior Horn |
Poliomyelitis |
Loss of muscle tone. Loss of reflexes. Flaccid paralysis. Denervation atrophy |
|
Lamina X (gray matter) |
Syringomyelia |
Bilateral loss of pain and temperature sense only at afflicted cord level. Sensory dissociation. No sensory impairment below afflicted level |
|
Anterior horn and lateral corticospinal tract |
Amyotrophic lateral sclerosis |
Muscle weakness. Muscle atrophy. Fasciculations of hand and arm muscles. Spastic paralysis |
|
Posterior and lateral funiculi |
Subacute combined degeneration |
Loss of position sense. Loss of vibratory sense. Positive Romberg sign. Muscle weakness. Spasticity. Hyperactive tendon reflexes. Positive Babinski sign. |
|
Hemisection of the spinal cord |
Mechanical injury |
Brown-Sequard syndrome |
|
Below cord level on injured side |
||
|
Flaccid paralysis. Hyperactive tendon reflexes. Loss of position sense. Loss of vibratory sense. Tactile impairment |
||
|
Below cord level on opposite side beginning one or two segments below injury |
||
|
Loss of pain and temperature |
||
Asthma = Reversible Bronchioconstruction 4%-5% of population
Extrinsic / Atopic = Allergic, inherited (familia), chromosome 11
IgE, Chemical Mediators of inflammation
a. Intrinsic = Negative for Allergy, Normal IgE, Negative Allergic Tests
Nucleotide Imbalance cAMP/cGMP: cAMP = Inhibits mediator release, cGMP = Facilitates mediator release
b. Intolerance to Asprin (Triad Asthma)
c. Nasal Polyps & Asthma
d. Treatment cause, Symptoms in Acute Asthma
1. Bronchial dilators
2. steroids edema from Inflamation
3. Bronchiohygene to prevent Secondary Infection, (Remove Excess Mucus)
4. Education
Chemical Controls of Respiration
A. Chemoreceptors (CO2, O2, H+)
1. central chemoreceptors - located in the medulla
2. peripheral chemoreceptors - large vessels of neck
B. Carbon Dioxide Effects
1. a powerful chemical regulator of breathing by increasing H+ (lowering pH)
a. hypercapnia Carbon Dioxide increases ->
Carbonic Acid increases ->
pH of CSF decreases (higher H+)- >
DEPTH & RATE increase (hyperventilation)
b. hypocapnia - abnormally low Carbon Dioxide levels which can be produced by excessive hyperventilation; breathing into paper bag increases blood Carbon Dioxide levels
C. Oxygen Effects
1. aortic and carotid bodies - oxygen chemoreceptors
2. slight Ox decrease - modulate Carb Diox receptors
3. large Ox decrease - stimulate increase ventilation
4. hypoxic drive - chronic elevation of Carb Diox (due to disease) causes Oxygen levels to have greater effect on regulation of breathing
D. pH Effects (H+ ion)
1. acidosis - acid buildup (H+) in blood, leads to increased RATE and DEPTH (lactic acid)
E. Overview of Chemical Effects
Chemical Breathing Effect
increased Carbon Dioxide (more H+) increase
decreased Carbon Dioxide (less H+) decrease
slight decrease in Oxygen effect CO2 system
large decrease in Oxygen increase ventilation
decreased pH (more H+) increase
increased pH (less H+) decrease
Levels of Organization:
CHEMICAL LEVEL - includes all chemical substances necessary for life (see, for example, a small portion - a heme group - of a hemoglobin molecule); together form the next higher level
CELLULAR LEVEL - cells are the basic structural and functional units of the human body & there are many different types of cells (e.g., muscle, nerve, blood)
TISSUE LEVEL - a tissue is a group of cells that perform a specific function and the basic types of tissues in the human body include epithelial, muscle, nervous, and connective tissues
ORGAN LEVEL - an organ consists of 2 or more tissues that perform a particular function (e.g., heart, liver, stomach)
SYSTEM LEVEL - an association of organs that have a common function; the major systems in the human body include digestive, nervous, endocrine, circulatory, respiratory, urinary, and reproductive.
There are two types of cells that make up all living things on earth: prokaryotic and eukaryotic. Prokaryotic cells, like bacteria, have no 'nucleus', while eukaryotic cells, like those of the human body, do.
Neurons :
Types of neurons based on structure:
a multipolar neuron because it has many poles or processes, the dendrites and the axon. Multipolar neurons are found as motor neurons and interneurons. There are also bipolar neurons with two processes, a dendrite and an axon, and unipolar neurons, which have only one process, classified as an axon.. Unipolar neurons are found as most of the body's sensory neurons. Their dendrites are the exposed branches connected to receptors, the axon carries the action potential in to the central nervous system.
Types of neurons based on function:
- motor neurons - these carry a message to a muscle, gland, or other effector. They are said to be efferent, i.e. they carry the message away from the central nervous system.
- sensory neurons - these carry a message in to the CNS. They are afferent, i.e. going toward the brain or spinal cord.
- interneuron (ie. association neuron, connecting neuron) - these neurons connect one neuron with another. For example in many reflexes interneurons connect the sensory neurons with the motor neurons.
GENERAL SOMATIC AFFERENT (GSA) PATHWAYS FROM THE BODY
Pain and Temperature
Pain and temperature information from general somatic receptors is conducted over small-diameter (type A delta and type C) GSA fibers of the spinal nerves into the posterior horn of the spinal cord gray matter .
Fast and Slow Pain
Fast pain, often called sharp or pricking pain, is usually conducted to the CNS over type A delta fibers.
Slow pain, often called burning pain, is conducted to the CNS over smaller-diameter type C fibers.
Touch and Pressure
Touch can be subjectively described as discriminating or crude.
Discriminating (epicritic) touch implies an awareness of an object's shape, texture, three-dimensional qualities, and other fine points. Ability to recognize familiar objects simply by tactile manipulation.
The conscious awareness of body position and movement is called the kinesthetic sens
Crude (protopathic) touch, lacks the fine discrimination described above and doesn't generally give enough information to the brain to enable it to recognize a familiar object by touch alone.
Subconscious Proprioception
Most of the subconscious proprioceptive input is shunted to the cerebellum.
Posterior Funiculus Injury
Certain clinical signs are associated with injury to the dorsal columns.
As might be expected, these are generally caused by impairment to the kinesthetic sense and discriminating touch and pressure pathways.
They include
(1) the inability to recognize limb position,
(2) astereognosis,
(3) loss of two-point discrimination,
(4) loss of vibratory sense, and
(5) a positive Romberg sign.
Astereognosis is the inability to recognize familiar objects by touch alone. When asked to stand erect with feet together and eyes closed, a person with dorsal column damage may sway and fall. This is a positive Romberg sign.
Functional Divisions of the Nervous System:
1) The Voluntary Nervous System - (ie. somatic division) control of willful control of effectors (skeletal muscles) and conscious perception. Mediates voluntary reflexes.
2) The Autonomic Nervous System - control of autonomic effectors - smooth muscles, cardiac muscle, glands. Responsible for "visceral" reflexes