18.9:
Reflex Activity
A reflex is a quick and automatic response to a stimulus, like pulling your hand away from heat or lifting your foot off a sharp object.
A reflex arc is the pathway that nerve impulses follow to produce a reflex action.
It is made up of five main components.
The first component is a sensory receptor that generates a nerve impulse when stimulated.
The second component is a sensory neuron that carries the impulses from the receptor to the central nervous system or the CNS.
The third component is an integration center located in the CNS, which processes the information provided by the sensory neurons.
Integration centers can be a single synapse between a sensory and motor neuron or multiple synapses with chains of interneurons in between.
The fourth component is a motor neuron, which carries motor instructions from the integration center to an effector muscle or a gland.
The fifth and final component is an effector muscle or a gland, which contracts or secretes a hormone to produce the reflex action.
18.9:
Reflex Activity
A reflex activity is an automatic, involuntary response to specific stimuli. It is a part of our survival mechanism, designed to protect us from potential harm. For example, when a bright light suddenly shines into our eyes, we instinctively close them or look away. This is a simple reflex activity orchestrated by the nervous system without conscious thought or effort.
A reflex exam is a diagnostic procedure performed by a healthcare professional to evaluate the functionality of a patient's reflexes. The exam can also assess the patient's sensory and motor function, as well as their coordination and balance.
It involves the stimulation of specific sensory receptors, typically through tapping or striking certain areas of the body and observing the resulting involuntary muscle contractions or reflex responses. The exam focuses on assessing the deep tendon reflexes, such as the knee-jerk reflex, ankle reflex, or biceps reflex.
The plantar reflex test is an essential tool used in neurological exams to assess the integrity of the central nervous system. It involves stroking the sole and observing the resulting movement of the toes. In a normal response, the toes curl downward.
However, in some cases, an abnormal response may occur. This is referred to as the Babinski reflex. Instead of the normal downward flexion of the toes, the big toe extends upward while the other toes spread out. This kind of reflex is typical in infants but pathological in adults.
It indicates a neurological dysfunction, such as damage to the descending tracts of the somatic nervous system or damage to the primary motor cortex.