The pupillary light reflex is a homeostatic mechanism that keeps the activation of photoreceptors within certain limits. If light levels are too high, which system is activated to constrict the pupil?
Explanation
The pupillary light reflex demonstrates the competing actions of the autonomic divisions. Bright light triggers a parasympathetic response (constriction), while dim light triggers a sympathetic response (dilation), to maintain optimal light levels on the retina.
Other questions
Which division of the autonomic nervous system is associated with the 'fight-or-flight' response, preparing the body for extreme physical exertion?
The sympathetic division of the autonomic nervous system is also referred to as the thoracolumbar system because its connections emerge from which regions of the spinal cord?
Typically, how many ganglia are found in the sympathetic chain on either side of the spinal column?
What is the term for the ganglia located near or within the target effector, which are targets of parasympathetic preganglionic fibers?
In the parasympathetic system, what is the relative length of the preganglionic and postganglionic fibers?
Which signaling molecule is released by all preganglionic fibers in both the sympathetic and parasympathetic divisions?
The adrenal medulla contains neurosecretory cells called chromaffin cells that develop from the neural crest. What is the functional significance of this?
A single preganglionic sympathetic neuron can have how many targets, illustrating the divergence of the sympathetic system?
What type of receptor is found on the cell membranes of all ganglionic neurons, for both sympathetic and parasympathetic divisions?
Which cranial nerve is NOT involved in the parasympathetic craniosacral outflow?
A visceral reflex arc that is completely peripheral and does not involve any CNS components is known as a what?
What is the phenomenon called when strong visceral sensations are perceived in an unexpected part of the body, such as feeling heart pain in the left shoulder?
What specific type of mechanoreceptor, found in the walls of the aorta and carotid sinuses, senses the stretch of those organs when blood volume or pressure increases?
In the autonomic control of pupillary size, which action is caused by the sympathetic system?
The resting state of an organ system, which may have a greater tendency toward sympathetic or parasympathetic influence, is known as its what?
Which structure serves as the primary control center for many homeostatic mechanisms, regulating both autonomic and endocrine functions?
The medial forebrain bundle and the dorsal longitudinal fasciculus are two main tracts that carry output from which brain structure to influence autonomic function?
What is the primary effect of nicotine on the autonomic nervous system, leading to its risk factor for cardiovascular disease?
A drug that enhances or mimics adrenergic function, such as phenylephrine, is known as a what?
Pilocarpine is a nonspecific muscarinic agonist. Based on this, what would be its effect on the autonomic system?
Which structure connects the hypothalamus with major parasympathetic nuclei in the brain stem and preganglionic neurons in the spinal cord?
What is the collective term for the celiac ganglion, superior mesenteric ganglion, and inferior mesenteric ganglion?
Postganglionic sympathetic fibers that project to sweat glands and blood vessels in skeletal muscle are an exception to the rule because they release which neurotransmitter?
What type of receptor is the muscarinic receptor?
The parasympathetic division of the autonomic nervous system is also known as the craniosacral system. The 'sacral' part refers to preganglionic neurons located in which part of the spinal cord?
The structure of some autonomic connections is not a typical synaptic end bulb but a string of swellings along the length of a fiber. What is this structure called?
What is the primary reason that orthostatic hypotension, a drop in blood pressure when standing, can occur?
In the efferent branch of a visceral reflex, how many neurons are in the pathway from the CNS to the target effector?
Which brain stem nucleus, named for its ambiguous histology, contributes to the parasympathetic output of the vagus nerve and targets muscles for swallowing and speech?
A sympatholytic drug such as a beta-blocker would have what effect on the cardiovascular system?
What are the two subtypes of cholinergic receptors in the autonomic nervous system?
What is the primary function of the Eustachian tube, which connects the middle ear to the pharynx?
The greater splanchnic nerve contains axons from central sympathetic neurons that synapse in which type of ganglion before innervating the stomach?
A patient taking a sympatholytic drug like propanolol, a non-specific beta-blocker, would likely experience what physiological effect?
What is the result of a long reflex?
The release of epinephrine and norepinephrine from the adrenal medulla into the bloodstream means they should be considered what type of signaling molecules?
The cardiovascular center, which contains the cardiac accelerator and vasomotor nerves, is located in which part of the brain stem?
Atropine and scopolamine are muscarinic antagonists derived from the Atropa genus of plants. What is their effect on the parasympathetic system?
Without any parasympathetic input, the intrinsic rate of the heart is approximately how many beats per minute (bpm)?
Which structure receives input from the olfactory cortex, septal nuclei, and amygdala to inform the hypothalamus about the state of the nervous system?
Kehr's sign, pain in the left shoulder after a spleen rupture, is an example of referred pain. The actual visceral sensation causing this sign comes from which structure?
The sympathetic fibers that cause constriction of blood vessels in response to signals from the cardiovascular center are known as what?
What is the primary characteristic of a somatic reflex that distinguishes it from a visceral reflex?
What is the name for the myelinated structures that provide a short connection from a spinal nerve to a sympathetic chain ganglion, containing preganglionic fibers?
Which part of the limbic lobe has strong connections to the hypothalamus and influences its activity based on emotional states like anxiety or fear?
What is the collective name for drugs that interrupt or reduce the function of the parasympathetic system?
Systemic blood pressure is primarily determined by the autonomic tone of which division?
What is the epithet used to describe the activity of the parasympathetic division?
How many ganglia in the sympathetic chain typically correspond to the cervical region on each side?