LO 10: ANS, Special Senses

Describe the following autonomic reflexes: cardiac, gastrointestinal, and micturition.

- Cardiac: Blood pressure is maintained by a baroreflex which can activate both the sympathetic and parasympathetic nervous systems. When blood pressure is too low, the sympathetic nervous system increases heart contractions, heart rate and vasoconstriction, all of which increases blood pressure. When blood pressure is too high, the parasympathetic nervous system decreases heart rate, reducing overall blood pressure. - Gastrointestinal: This is a stretch reflex that senses stretching in the walls of the stomach. Stretch receptors are activated and send signals to the ANS to stimulate digestion (GI gland secretion and motility, relax sphincters and stimulate glycogenesis in the liver). - Micturition: When the bladder fills, the walls of the bladder stretch, sending a signal to the brain. When a person urinates, the brain decreases action potentials to the nerves that relax the urinary sphincter, allowing urine to pass out of the bladder and out of the body.

Define the following terms: glaucoma, astigmatism

- Glaucoma is a group of conditions that cause damage to the optic nerve, which is necessary to see. It's usually caused by abnormally high pressure in the eye, which is caused by excess aqueous humor in the eye, either by overproduction or insufficient drainage. Glaucoma tends to run in families. - Astigmatism is a defect in the eye that is caused by a deviation in the spherical curvature of the eye, which results in distorted images.

Describe the effects of innervation by the parasympathetic and sympathetic systems on the following structures: pupils of the eye, salivary glands, sweat glands, heart, lungs, GI tract, and blood vessels of the skeletal muscle, coronary, and the integumentary systems.

- Pupils of the eye: S: Dilation P:Constriction - Salivary glands S:Produces viscous secretion P:Produces watery secretion - Sweat glands : S:Secretion P:None - Heart S:Increases heart rate, force of contraction P:Decreases heart rate - Lungs S:Bronchodilation P:Bronchoconstriction - GI tract S:Inhibits gland secretion and causes vasoconstriction P:Increases gland secretion and vasodilation - Blood vessels of skeletal muscle S:Vasodilation P:None - Coronary S:Vasodilation of beta receptors, P: vasoconstriction of alpha receptors Vasodilation - Integumentary S:Contracts arrector pili to cause hair erection P:None

What are the structural and functional differences between the sympathetic and parasympathetic divisions of the ANS?

- Structural: In sympathetic NS, the preganglionic fiber is shorter and the postganglionic fiber is longer, making the ganglion closer to the spinal cord. In the parasympathetic NS, the preganglionic fiber is longer and the postganglionic fiber is shorter, making the ganglion closer to the organ. - Functional: The sympathetic NS is excitatory: it results in excitement, exercise and embarrassment. The parasympathetic NS is relaxing, the "rest and digest" NS. The preganglionic fibers for both the SNS and the PSNS is cholergenic, releasing Ach. The postganglionic fibers differ: in the SNS, the postganglionic fiber is adrenergic and releases norepinephrine (NE). In the PSNS, the postganglionic fiber is also cholergenic, and releases Ach.

What neurotransmitters are released by the different divisions of the ANS

Ach and norepinephrine.

What are the adrenergic receptors, and where are they found?

Adrenergic receptors can be nicotinic or muscatinic, and they are found on the organ.

The parasympathetic nervous system is also called craniosacral- why?

Because the nerves originate from the cranial and sacral areas of the CNS.

What are the cholinergic receptors, and where are they found?

Cholinergic receptors can be alpha or beta receptors, and they are found on the organ.

What is diabetic retinopathy?

Diabetic retinopathy is a complication of diabetes. Many tissues can be damaged by the inability to regulate blood sugar, including blood vessels that are present in the retina. Diabetic retinopathy occurs because these vessels leak blood and other fluids. The symptoms of diabetic retinopathy include "floaters," blurriness, dark areas of vision and difficulty perceiving colors. At its most extreme, blindness can occur.

Summarize the process of hearing and indicate the important structures involved in the process

First, sound waves enter the ear. They pass through the external auditory canal and hit the tympanic membrane, which vibrates. The vibrations move through the tympanic membrane to the three ossicles: the malleus, incus and stapes. The vibrations enter the cochlea from the stapes through the oval window. The vibrations cause wave-like movement in the perilymph fluid, which moves the basilar membrane and creates waves in the endolymph fluid. The waves move the basilar and tectorial membranes inside the cochlea. The tectorial membrane then moves the cilia attached to hair cells, which creates a mechanical change that allows a positive charge to enter the hair cell, which creates an action potential. The AP allows the hair cell to send information via its axon (and thus the cochlear nerve) to the thalamus, from which it is transmitted to the auditory cortex, and then the auditory processing cortex.

Which cranial nerves carry parasympathetic information?

III, VII, IX and X.

Why is the adrenal medulla considered to be a modified sympathetic ganglion? The

The adrenal medulla is located at the center of the adrenal gland, and it consists of cells that secrete epinephrine, norepinephrine and a small amount of dopamine. It consists of irregularly shaped cells grouped around blood vessels. It's considered a modified sympathetic ganglion because it functions as a postganglionic cell in the ANS, fed by preganglionic sympathetic cells in the CNS. The adrenal medulla also releases neurotransmitters that are normally released by postganglionic cells in the ANS.

What are the auditory ossicles, and where are they located?

The auditory ossicles are three structures connected to the tympanic membrane and the cochlea in the inner ear. They are the malleus, incus and stapes.

What are the optic discs?

The optic disc is located at the posterior of the eye, slightly toward the medial side. It's the location where all of the axons of the ganglia converge. There are no rods or cones, and thus no photoreceptors, in the optic disc. This results in the blind spot in human vision.

What structures are responsible for equilibrium?

The semicircular canals are responsible for equilibrium. When your head moves around, fluid in the semicircular canals moves and stimulates tiny hairs in each canal, which send information through nerve cells to the brain to allow it to sense the body's position in space.

What are the structures of the inner ear?

The structures of the inner ear include the cochlea and the semicircular canals. The cochlea is separated into three separate compartments that contain perilymphatic fluid (external) and endolymphatic fluid (internal). Inside the cochlea is the organ of corti, where hair cells (neurons) connect to the basilar and tectorial membranes.

Which division of the ANS is also called the thoracolumbar? Why?

The sympathetic NS is called the thoracolumbar, because the nerves originate in the thoracic and lumbar areas of the spine.

What are the two subdivisions of the autonomic nervous system

The sympathetic and the parasympathetic NS

What are the three layers or the neural tunic of the eye wall?

The three tunics of the eye are the fibrous tunic, the vascular tunic and the nervous tunic. The fibrous tunic is made up of the cornea and the sclera. The vascular tunic contains the iris, the ciliary body and the choroid. The neural tunic contains the retina.

. In some severe cases, a person suffering from stomach ulcers may have surgery to cut the branches of the vagus nerve that innervates the stomach. Explain the neurophysiological effects pertaining to gastric secretion and digestive function that would result from severing the vagus nerve.

The vagus nerve provides parasympathetic, or "rest and digest" function to the stomach. It signals the stomach to produce the acid necessary to digest food. Cutting the vagus nerve would reduce the amount of acid produced, which could reduce the pain caused by stomach ulcers. However, the vagus nerve also sends signals to the digestive system to move food from the stomach into the small intestine. The reduced acid and the reduction in movement of bolus would slow down the digestive process. This is problematic for patients, and as a result, vagotomy is not commonly practiced anymore.

Briefly summarize the steps involved in photoreception in your own words. When

When light enters the eye, it hits photoreceptors in the rods and cones in the retina. The light changes the shape of the retinol in rhodopsin, which causes opsin to be released into the cell. Opsin activates phosphodiesterase, which changes cGMP to GMP, and removes GMP from gates in the cell membrane that usually let in calcium and sodium. When the GMP is removed, the gates close, stopping the movement of calcium and sodium into the cell. This lowers the cell's RMP to -70 mV, which then stops the cell from releasing an IPSP. When the IPSP isn't transmitted to the bipolar nerve cell in the retina, the bipolar cell then is able to release a neurotransmitter to the ganglion cell, which will trigger an action potential in the ganglion cell. The ganglion cell then transmits the stimulus through the optic nerve and to the thalamus, which then transmits the stimulus to the visual cortex and then the visual association cortex, which processes the information.