NEUROLOGY 2 MARKS : PART 13

MECHANORECEPTORS & CHEMORECEPTORS:

  • Mechanoreceptors are receptors in the skin and on other organs that detect sensations of touch.
  • They are called mechanoreceptors because they are designed to detect mechanical sensations or differences in pressure.
  • Nociceptors, mechanoreceptors, chemoreceptors, thermoreceptors, and photoreceptors are types of sensory receptors (sensory neurons) located in different areas of the body.
  •  Mechanoreceptors are a type of sensory receptor that are activated and respond to mechanical pressure.

5 TYPES OF SENSORY RECEPTORS:

  • Phemoreceptors- stimulated by changes in the chemical concentration of substances.
  • Pain receptors-stimulated by tissue damage.
  • Thermoreceptors- stimulated by changes in temperature.
  • Mechanoreceptors- stimulated by changes in pressure or movement.
  • Photoreceptors- stimulated by light energy.

MUSCLE SPINDLE:

  •  Muscle spindles are stretch receptors within the body of a muscle that primarily detect changes in the length of the muscle.
  • They convey length information to the central nervous system via afferent nerve fibers.
  • The responses of muscle spindles to changes in length also play an important role in regulating the contraction of muscles, by activating motor neurons via the stretch reflex to resist muscle stretch.
  • Proprioceptors are specialized sensory receptors that are located within joints, muscles, and tendons.

THE GOLGI TENDON ORGAN  :

  • The Golgi tendon organ (GTO) (also called Golgi organ, tendon organ, neurotendinous organ or neurotendinous spindle) is a proprioceptive sensory receptor organ that senses changes in muscle tension.
  • The golgi tendon organ is a proprioceptor, sense organ that receives information from the tendon, that senses TENSION.
  • If there is too much muscle tension thegolgi tendon organ will inhibit the muscle from creating any force  thus protecting  from injuring itself.

PHYSIOLOGICAL CLASSIFICATION OF REFLEXES:

  • Stretch (knee-jerk, patellar) reflex.
  • Withdrawal (flexor) reflex.
  • Crossed-extensor reflex.

CLASSIFICATION OF CLINICAL REFLEXES:

  • Superficial reflex
  • Deep reflexes
  • Visceral reflexes
  • Pathological reflexes.

ANATOMICAL CLASSIFICATIONS:

  • Segmental reflex
  • Intersegmental  reflex
  • Suparsegmental reflex

CLONUS:

  • Clonus is a neurological condition that occurs when nerve cells that control the muscles are damaged.
  • This damage causes involuntary muscle contractions or spasms.
  • Clonus is a neurological condition that occurs when nerve cells that control the muscles are damaged. 
  • Clonus may be found at the ankle, patella, triceps surae, wrist, jaw, biceps brachii.
  • Damaged nerves can cause muscles to misfire, leading to involuntary contractions, muscle tightness, and pain.
  • Clonus can cause a muscle to pulse for an extended period. This pulsing can lead to muscle fatigue, which may make it difficult for a person to use the muscle later.

MONOSYNAPTIC AND POLYSYNAPTIC:

  • Monosynaptic refers to the presence of a single chemical synapse.
  • Monosynaptic reflex is a simple reflex that involves transmission of information from asensory neuron to the appropriate motor neuron across a single synapse in thespinal cord. 
  • By contrast, in polysynaptic reflex arcs, one or more interneurons connect afferent (sensory) and efferent (motor) signals.
  • The knee-jerk reflex is considered a monosynaptic reflex because it involves direct connections between sensory neurons and motor neurons, without any neurons in between.

MYOTOMES AND DERMATOMES:

  • Myotomes and dermatomes are a part of the somatic (voluntary) nervous system, which is part of the peripheral nervous system.
  • A dermatome is an area of skin supplied by sensory neurons that arise from a spinal nerve ganglion.
  • Each dermatome represents the sensory innervation of a particular spinal nerve.
  • Myotomes is  a group of muscles innervated by a single spinal nerve.

CAUSALGIA:

  • Causalgia is technically known as complex regional pain syndrome type II (CRPS II).
  • It’s a neurological disorder that can produce long-lasting, intense pain.
  • Causalgia is usually caused by brachial plexus injuries, involving nerves that run from the neck to the arm.
  • The disruption of neural signals causes pain and increased release of the neurotransmitter norepinephrine.
  • Research supports that there is no causal relationship between depression, anxiety, anger and sleep disorders, and CRPS.

ANTERIOR HORN CELLS:

  • Anterior horn cells (α-motor neurons), located in the anterior gray matter of the spinal cord, are found at every segment and are concentrated in the cervical and lumbosacral enlargements.
  • The lower motor neuron includes the anterior horn cell (motor neuron), nerve, neuromuscular junction, and muscle. 
  • Cell bodies are located in anterior horn of the spinal cord.

CATHERINE SHALINI RAJA
M.P.T.,MIAP.,PGDYN
CARDIO RESPIRATORY PHYSICAL THERAPIST
FITNESS & SPORTS REHABILITATION SPECIALIST
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