Spontaneous blinking is an intrinsic motor pattern that maintains the tear film and protects the eye. It involves a stereotyped sequence: rapid contraction of the orbicularis oculi (eyelid‐closing muscle) followed by relaxation and reactivation of the levator palpebrae superioris (eyelid‐opening muscle). Unlike reflex blinks triggered by external stimuli, spontaneous blinks originate in central circuits spanning…
Author: lewj2012
Milk letdown reflex
The human milk letdown reflex, a critical neuroendocrine mechanism for neonatal survival, is initiated by the suckling stimulus at the nipple and areola, which are densely innervated cutaneous regions (1, 2, 3). This tactile stimulation activates a complex neural pathway culminating in the pulsatile release of oxytocin from the posterior pituitary gland, leading to the…
Oxytocin release
Oxytocin is a neuropeptide hormone synthesized in magnocellular neurosecretory cells of the paraventricular and supraoptic nuclei in the hypothalamus [1][2]. It is packaged into neurosecretory vesicles and transported down axons to the posterior pituitary gland, where it is released into the bloodstream [1]. Oxytocin is also released within the brain from dendrites and soma of…
Neural regulation of LHRH
Luteinizing hormone-releasing hormone (LHRH) is a neurohormone produced in the hypothalamus which regulates reproduction [1]. LHRH neurons project to the median eminence and release LHRH in a pulsatile manner into the hypophyseal portal system [2]. This stimulates the anterior pituitary to secrete luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which act on the gonads to…
Neural regulation of prolactin secretion
Neural regulation of prolactin secretion involves complex interactions between hypothalamic dopamine neurons and various stimulatory and inhibitory neurotransmitters. The key hypothalamic dopamine (TIDA) neurons project to the pituitary gland and inhibit prolactin release through dopamine D2 receptors on lactotrophs. TIDA activity is regulated by prolactin feedback, estrogen, neurotensin, bombesin, glutamate, opioids, GABA, and other factors…
Neural regulation of cerebral blood flow
Neural regulation of cerebral blood flow is a complex process that involves coordination between neural activity, blood vessels, and metabolic factors. Here is a detailed summary based on the provided sources: Neural activity leads to increased cerebral blood flow to active regions through neurovascular coupling. When neurons are active, they utilize more oxygen and glucose,…
Gamma loop
The gamma loop is a feedback mechanism which allows the nervous system to maintain muscle contraction and proprioception [1]. Gamma motor neurons in the spinal cord excite intrafusal muscle fibers in muscle spindles, causing them to contract [2]. This stretches the central portions of the intrafusal fibers, stimulating the Ia sensory afferents that wrap around…
Atrial reflex
The atrial reflex, also known as the Bainbridge reflex, is an important neural mechanism which helps maintain cardiovascular homeostasis, providing several key benefits to the body [1]. This reflex is mediated by stretch receptors in the atria which detect changes in blood volume. These receptors send signals via vagal afferent nerves to the nucleus tractus…
Sensory receptors
Sensory receptors exhibit specialized sensitivities and transduction mechanisms to detect particular physical stimuli relevant for perception and behavior [1][2][3]. For example, photoreceptors in the retina contain light-sensitive opsins that transduce light energy into electrical signals [3][4][6]. Rod photoreceptors detect dim light while cone photoreceptors enable color vision [4]. In the auditory system, hair cells in…
Optic flow
Optic flow refers to the visual motion pattern that occurs due to relative motion between an observer and their surrounding environment. This flow pattern contains information about the observer’s direction and speed of self-motion, as well as the three-dimensional structure of the environment. The processing of optic flow begins in the primary visual cortex (V1),…