The Landau reflex is a primitive reflex observed in infants that facilitates crawling movements [1]. When the infant is held in a vertical position with their feet touching a flat surface, a reflexive stepping motion occurs as the infant places one foot in front of the other [2]. This reflex emerges around 8-10 months of…
Author: lewj2012
Oculocardiac reflex
The oculocardiac reflex is a brainstem reflex that causes a decrease in heart rate during traction on the extraocular muscles (1). This reflex protects the retina from potential damage during eye movement by coordinating the actions of the oculomotor and vagus nerves (2). When the eye is moved by applying pressure on the globe, this…
Optical blink reflex
The optical blink reflex (sometimes called the “dazzle reflex”) is a rapid protective closure of the eyelids triggered by sudden visual stimuli (e.g. bright light or an approaching object) and is mediated by a subcortical brainstem circuit. In humans, this reflex begins with retinal photoreceptors (rods and cones) and retinal ganglion cells (RGCs) detecting the stimulus. These…
Blink reflex
The blink reflex protects the eye from potential damage when foreign objects make contact with the cornea or conjunctiva (1). This reflexive blinking is accomplished through a reflex arc between the trigeminal nerve (CN V) and facial nerve (CN VII) (2). When the cornea or conjunctiva are stimulated, sensory information is transmitted via the ophthalmic…
Pupillary dark response
Pupillary dilation in response to the absence of light occurs due to the reduction or absence of constriction signals which otherwise oppose tonic sympathetic pupillary dilation (1). Since the iris sphincter is stronger than the dilator muscle, pupil dilation does not readily occur until the sphincter muscle relaxes (2). Relaxation of the iris sphincter is…
Reflex tear secretion
Reflex tear secretion is a fundamental protective mechanism of the ocular surface, triggered by a variety of stimuli that engage a complex neurocircuitry to elicit a rapid and graded lacrimal gland response. This process is distinct from basal and emotional tearing, relying on a well-defined reflex arc involving sensory afferents, central processing units within the…
Neural Regulation of Insulin Secretion
Insulin secretion from pancreatic beta cells is regulated by both nutrient and neural signals [1][2]. Vagal cholinergic signaling stimulates insulin release, mediated by muscarinic receptors on beta cells [2][6]. Gastrin and secretin also stimulate insulin secretion [1]. In contrast, sympathetic norepinephrine signaling inhibits insulin release via α2-adrenergic receptors [1][3]. Low blood glucose is sensed by…
Neural regulation of glucose homeostasis
Glucose homeostasis is tightly regulated by neural and hormonal signals. The pancreas secretes insulin and glucagon to control blood glucose levels [1][4]. Insulin secretion is stimulated by rising blood glucose levels as well as neural signals from the vagus nerve [2][3]. Insulin signals the liver, muscle and adipose tissue to take up glucose from the…
Neural regulation of growth hormone secretion
Growth hormone (GH) secretion from the anterior pituitary is primarily regulated by two hypothalamic hormones – growth hormone releasing hormone (GHRH) and somatostatin [1][2]. GHRH is secreted from the arcuate nucleus and stimulates GH release. Somatostatin is secreted from the periventricular nucleus and inhibits GH release [1][3]. The balance between GHRH and somatostatin signaling generates…
Neural regulation of metabolism
The hypothalamus and brainstem play key roles in regulating metabolism through both neural and hormonal signals [1][2]. The arcuate nucleus in the hypothalamus contains neurons that sense nutrients and hormones related to energy status, including leptin, insulin, and ghrelin [3][5]. These neurons project to other hypothalamic areas like the paraventricular nucleus to modulate appetite and…