REFLEXES THE CODES OF NEUROLOGY

reflexesneurologytaskindumankapak21432

NEUROANATOMY AND NEUROPHYSIOLOGY OF REFLEXES

Muhammet Okay Örün

Van Education and Research Hospital, Department of Neurology, Van, Türkiye

Örün MO. Neuroanatomy and Neurophysiology of Reflexes. In: Duman T, editor. Reflexes The Codes of Neurology. 1st ed. Ankara: Türkiye Klinikleri; 2025. p.25-42.

ABSTRACT

A reflex can be performed as a continuous, involuntary, qualitative response of the nervous system to any internal or external stimulus. The organism requires a stable and balanced internal environment, known as homeostasis, along with physical integrity. Both somatic and autonomic reflexes are crucial for maintaining the organism’s homeostasis and physical integrity.

The formation of reflexes is possible with the normal functioning of the anatomical-physiological structure defined as the reflex arc. The reflex arc consists of 5 basic elements. The receptor is a specialized structure that detects the stimulus, the afferent pathway carries the input to the reflex center, the reflex center generates the response and prepares the necessary actions, the efferent pathway receives and transmits the response, the effector organ receives the response from the efferent pathway and executes it.

Although each reflex has its own unique reflex arc, they can be classified under the same category due to some shared features. Reflexes are classified in various ways, depending on the number of synapses, their development, the processing region of the nervous system, and the area to which the response is directed.

The chemical message transmission system, applicable to all neurons in the nervous system, plays a key role in reflex formation. Neurotransmitters, which are endogenous chemical messengers that transport and amplify signals between nerve cells, are essential for transmitting information in the nervous system. Since 1921, more than 200 of these chemical messengers have been identified, yet the exact number of neurotransmitters remains unknown. various neurotransmitters involved in the formation of reflex mechanisms can have excitatory, inhibitory, or modulatory effects.

Although the structures of the peripheral nervous system, such as receptors and afferent and efferent nerves, play a critical role in reflex formation, the central nervous system also influences reflex mechanisms. The spinal cord, reticular activating system (RAS), brainstem, cerebellum, thalamus, and motor cortex are central nervous system structures that directly or indirectly affect reflexes. To sustain life, the body must continuously receive sensory input from its environment and internal structures and generates suitable motor responses. The brainstem and spinal cord are responsible for receiving sensory inputs and transmitting responses to peripheral organs. While the spinal cord primarily generates simple reflexes, both simple reflexes and more complex muscle movements are coordinated in the brainstem. As the response ascends to higher structures of the central nervous system, such as the cerebellum, motor cortex, and thalamus, it becomes increasingly complex.

Keywords: Reflex arc; Reflex; Neurotransmitters; Neurophysiology; Neuroanatomy; Monosynaptic reflex

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