Cranial Nerves
Name two cranial nerves that target the tongue.
Glossopharyngeal (CN IV)
Hypoglossal (CN XII)
Name the three ear ossicles, in the order by which they are stimulated.
malleus -> incus -> stapes
Explain why chemicals must be dissolved in order for the brain to interpret them in the sense of taste.
Tastants must dissolve into the saliva to access the chemoreceptors that are deep within the gustatory pores of the taste buds, which are located on the edges of the papillae of the tongue.
Name the tunics of the eye, from most superficial to the deepest. Include the subcomponents of each tunic.
fibrous tunic (sclera & cornea) -> vascular tunic (choroid, ciliary body, & iris) -> neural tunic (retina)
Explain what is meant by dual innervation and how this applies to the ANS.
Most visceral organs have nerves coming from both sides of the ANS, mediating homeostasis. For example, the heart can receive messages from the Parasympathetic division via the Vagus (CN X) or the Sympathetic division via a different nerve. The heart rate can be either increased or decreased depending on the current needs of the body. Two exceptions are the skin (sweat glands) and the adrenal gland. These two are only innervated by the Sympathetic division.
Name the cranial nerve responsible for equilibrium and hearing.
Vestibulocochlear (CN VIII)
Explain what is meant by mechanically gated ion channels & how they apply to both hearing and equilibrium.
Mechanically gated ion channels require a physical force to open them, such as the shearing forces applied to the gelatinous tectorial membrane by the vibration passing through the endolymph. This bends the stereocilia on the hair cells (neurons) and triggers an action potential. This is similar to the force applied by gravity to the otolith membrane for static balance and momentum on the cupula for dynamic balance.
What is the function of basal cells in the chemical senses?
Basal cells are germ cells that can replace damaged neurons of smell & taste. Most neurons are amitotic, but since both of these senses have neurons that are exposed to the outside world, they are susceptible to damage. Taste in particular is susceptible due to the potentially harsh environment (e.g., hot or acidic foods, etc.).
Aqueous humor is a plasma-like fluid that circulates anterior to the lens. It serves to provide nutrients and remove wastes and is the primary determinant of intraocular pressure. Vitreous humor is a gel-like substance that resides posterior to the lens. It serves primarily to hold the retina flat against the back of the eye and supports the back of the lens.
Name two specific physiological effects that would occur at the skeletal muscles when either the Sympathetic or Parasympathetic division is in control.
When the Sympathetic division is in control, the skeletal muscles will need to receive more blood flow, so the smooth muscles of the blood vessels serving them would be inhibited in order to vasodilate and bring in more blood. When Parasympathetic takes over, the opposite would happen. The vascular smooth muscles would be stimulated and vasoconstriction would limit blood flow here. Such as just after a meal, the Parasympathetic division would need to shift blood to the stomach to more efficiently digest the food.
List two functions of the vagus nerve, including at least one sensory and one motor function.
Sensory: taste from pharynx. Motor: innervates visceral organs, such as sending Parasympathetic impulses to the heart.
Briefly explain why humans cannot hear sounds that are too low in pitch.
The wavelength of a very low pitch sound will travel past the oval window into the scala vestibuli of the cochlea and will pass around the cochlear duct via the helicotrema into the scala tympani and out through the round window. By missing the cochlear duct where the neurons are, no action potentials will be sent to the brain.
How does the word adaptation apply to the sense of smell?
Compare & contrast the functions & locations of rods & cones.
Rods are the most common photoreceptor type and are found throughout the peripheral areas of the retina. They can respond in fairly low light but are capable of detecting only black & white because they have only one pigment. Cones have three pigments, thus can detect color. They also provide fine focus and are concentrated in the fovea centralis. As you move out from the the fovea centralis into the macula, there is a transition from pure cones to a mix of rods & cones.
Differentiate between cholinergic and adrenergic fibers. Where would you find each & what do they each do?
Cholinergic fibers are the neurons that release ACh. They would be found in the Somatic NS, all pre-ganglionic neurons of both sides of the ANS, and the post-ganglionic neurons of the Parasympathetic division. Adrenergic fibers are the neurons that release NE and are exclusively found in the post-ganglionic neurons of the Sympathetic division.
Name the three cranial nerves responsible for movement of the eye.
Oculomotor (CN III), Trochlear (CN IV), Abducent (CN VI)
Describe the 'sound attenuation reflex' and how it serves to protect ones hearing.
Name the targets for smell & taste impulses.
Odorants trigger action potentials to travel to the thalamus and then to the frontal lobe where the olfactory cortex is located. Tastants trigger action potentials to travel to the thalamus and then to either the insula or parietal lobe where the gustatory cortex is located.
Briefly differentiate between the optic disc and the blind spot.
The optic disc is a structure at the back of the eye where the axons exit. It contains no photoreceptors so the brain does not get any information from this part of the visual field, thus creating a 'blind spot'. Fortunately, the opposite eye can provide the missing information via cortical fusion and thus does not appear in the perceived image.
Differentiate between adrenergic and cholinergic receptors based on function & location.
Adrenergic receptors receive NE and are found on all Sympathetic effector organs. Cholinergic receptors receive ACh and are found on all Somatic effectors (skeletal muscles), all ganglionic neurons of both sides of the ANS, and all Parasympathetic effector organs.
Oculomotor (CN III), Trochlear (CN IV), Trigeminal (CN V1), Abducent (CN VI)
Explain how the semicircular canals function to inform the brain of the body's position.
Three semicircular canals filled with endolymph are positioned in the three planes of the body (frontal, sagittal, and transverse). When the body moves, momentum causes the endolymph to move & can trigger the crista ampullaris. The brain can use the combination of information from the three planes to determine body position.
Differentiate between papillae and taste buds.
There are four distinct types of papillae on the tongue. These are the visible bumps on the tongue and they may or may not contain taste buds. Taste buds are the microscopic structures deep within the crevices surrounding certain papillae and they contain a gustatory hair cell (neuron) and a taste pore through which saliva brings chemicals to be sensed.
Name one disorder associated with each of the following: cornea, lens, retina
Explain specifically how beta-blocker drugs function at the receptor level. Also, discuss which types of patients they might be prescribed to.
The Sympathetic division increases heart rate by sending NE to beta-1 adrenergic receptors. Beta-blocker drugs are Sympathetic antagonists because they bind to & inhibit beta-1 adrenergic receptors on the heart. Typically these medications are given to patients with heart abnormalities or arrythmias, hypertension, or anxiety disorders and are designed to keep the heart from ever going too fast.