Lecture 11 Study Guide

Why would people using chemotherapy agents take antiemetic medications? How do antiemetic agents work?

these medications numb the vomiting center so that the toxic substances that cause the GI tract to send signals to the vomiting center can keep food down, and also so that the body doesn't form a memory associating the perfectly fine food you ate with vomiting and toxicity.

What is an advantage of a keen sense of smell? What is an advantage of smell or taste sensations being relayed to the vomiting center in the medulla?

keen sense of smell can help you detect toxins present in the air, saving you from ingesting them. By passing smell and taste to the vomiting center in the medulla, we can help save ourselves if we ingest something dangerous.

What is the vomiting center of the brain? Where is it? What type of sensory information is relayed there? What is the role of dopamine in the system?

area postrema, region in the medulla oblongata that detects CSF and blood composition and also recieves input from gustatory and olfactory receptors and the GI tract. Dopamine in the system is used as a NT to initiate this, so by blocking it you can supress nausea

What would happen to your ability to visually focus if the nerve to the ciliary body were cut?

you would not be able to bend light and would have blurred vision as a result.

What do you think is the importance of smell or taste memories?

smell and taste can have valuable survival mechanisms with memories so that you known not to eat toxic tastes or smells.

What similarities and differences exist for olfaction and gustation?

smell and taste converge in the cerebrum to give you an overall understanding of what you are eating. They are both chemoreceptors and end in a similar region of the cerebrum. Olfactory pathway bypasses the thalamus, however, and instead synapses directly with the limbic system which is why it is strong associated with memory. It also only has one cranial nerve involved, CNI, and it is the actual receptors. The Gustatory pathway uses three cranial nerves, CNVII, CNIX and CNX but has gustatory hairs as the receptors. Both pathways are adaptable, regenerative, and detect toxic particles at lower thresholds.

Why is it important that the lens and cornea and eye fluids be crystal celar?

because the light needs to get through accurately so that we can see.

Why do you need to keep batteries fresh in your smoke detector?

because the olfactory pathway does not synapse with the thalamus and is not involved in stimulating the RAS, so if you smelled smoke it would not wake you up

7. What controls the position of the eye in its orbit (what allows you to move your eye medially, laterally, etc.)? What innervates these structures? (You do not need to know the names of each muscle & which direction they move the eye, or which cranial nerve innervates which muscle - you do need to know which 3 cranial nerves collectively innervate these muscles).

extrinsic eye muscles control the movement of each eyeball. These muscles originate from the walls of the orbit and insert into the outer surface of the eyeball. They allow the eyes to follow a moving object, help maintain the shape of the eyeball, and hold it in orbit. Cranial nerves III, IV and VI innervate these muscles, the trochlear, abducens, and oculomotor.

Why might medications for the treatment of Parkinson's disease lead to vomiting or nausea?

GI tract sends info to the vomiting center in the medulla, the area postrema

Using the figures from chapter 15, make sure you know the location and are able to identify on a figure, as well as the function of each of the following: a. Accessory structures: Palpebrae (eyelids), conjunctiva, lacrimal apparatus b. Anterior & posterior cavities, aqueous humor, vitreous humor c. Fibrous tunic: sclera & cornea d. Vascular tunic (Uvea): iris, ciliary body (ciliary process & muscles), choroid, pupil, suspensory ligaments e. Sensory/Neural tunic (retina): pigmented layer & neural layer, macula lutea, fovea centralis, optic disc, optic nerve, ganglion cells, bipolar cells, photoreceptors f. Lens

A.) Accessory structures: 1. Palpebrae (eyelids) = provide protection 2. Conjunctiva = transparent mucus membrane, it lines the eyelids and folds back over the surface of the eyeball. It covers only the white of the eye. It produces lubricating mucus so the eyes don't dry out. 3. lacrimal apparatus = the lacrimal gland and ducts that drain secretions from this. This produces tears, which cleans and protect the eye surface. if too much is produced, they spill over the eyelids and fill the nasal cavities, the ducts run to the nasal cavities. B.) 1. Anterior and Posterior Cavities = Anterior segment contains the aqueous humor and the posterior segment contains the vitreous humor. These are both used to help maintain the shape of the eye. The two segments are divided by the lens which is supported vertically. 2. Aqueous Humor = anterior segments, continually remade, similar to blood plasma 3. Vitreous Humor = posterior segment. forms as embryo and lasts a lifetime C.) Fibrous Tunic = avascular 1. Sclera = the posterior portion and the bulk of the fibrous layer which is the outside. it is the white of the eye, it protects the shape of the eyeball and serves as a point for the extrinsic muscles to anchor. it is continuous with the dura mater of the brain 2. Cornea = very anterior portion, it is transparent and bulges from the sclera. this is a window for light to enter the eye and works as part of the light bending apparatus. D.) Vascular Tunic = vascular 1. Iris = The iris is the colored part of the eye. it lies between the cornea and the lens and is continuous with the ciliary body posteriorly. It does not touch. these are smooth muscles that control the size of the pupil. 2 Ciliary body = The very anterior portion of the choroid layer. It is a ring of smooth muscle that controls the shape of the lens 3. Ciliary process and muscles = muscles control the lens shape, processes are folds near the lens that secrete fluid that fills the anterior cavity of the eye. 4. Choroid = blood vessel rich membrane that forms the back portion of this layer. Its vessels nourish all eye layers. It is brown in color due to melanocytes (melanin) which helps to absorb light so it isn't reflected within the eye. 5. Pupil = the opening between the two portions of the iris, that allows light to enter the eye. Sphincter pupillae are circular muscles that control the closing of the eye in bright light, the dilator puillae are radial muscles that dialate the eye in dim light. Sympathetic muscles dialate and parasympathetic constrict 6. Suspensory ligaments= extend from the ciliary processes to the lens to hold it in an upright position. E.) Sensory/ Neural Tunic (Retina) = extension of brain 1. Pigmented layer = outer. next to choroid, also prevents light from scattering and stores vitamin A 2. Neural layer= inner, transparent, only this layer plays a direct role in vision.. 3. macula lutea = oval region that enhances visual acuity, so important in detail sight. 4. fovea centralis = center of the macula lutea, it contains only cones to provide detailed color vision 5. optic disc = where the optic nerve exits the eye, this is a blind spot because it lacks photoreceptors, but the opposite eye compensates. 6. optic nerve = continuous with the ganglion cells, carries sensory info in to the brain. 7. ganglion cells = generate action potentials and make a right angle turn to send info up the optic nerve. 8. bipolar cells = in between ganglion and photo 9. photoreceptors = attached to the pigmented layer. ora serrata is the region between the ciliary body and the choroid. F.) lens = biconvex structure that can change its shape to focus light onto the retina. it enlarges throughout life with is gradually why our vision gets worse with age.

2. What is gustation? What are the gustatory receptors - are they special cells or are they the end of a CN? Do you have the same taste buds all your life or are they replaced? What are tongue papillae? What is the function of the one type that does not contain taste buds? Are all taste sensations equally sensitive (I asked something similar for smell)? a. Complete the blanks to describe the gustatory pathway. The ______________, _______________ & _______________ cranial nerves receive signals from gustatory cells. If an action potential is generated, these cranial nerves will relay information to the next neuron in the solitary nucleus of the ___________ _______________. From there, the axons project to the __________ and then to the gustatory cortex in the _____________ (or _____________) lobe. b. How does olfactory information affect taste perception?

Gustation is the sense of taste. The receptors are special cells of the gustatory epithelium called gustatory hairs. These are regenerative, so no we don't have the same cells all our lives. Togue papillae are little hills that have taste buds in them or provide friction. This is used to grip your food, or in cats to groom. there are different thresholds for different toxicities of tastants A.) The facial (2/3), glossopharyngeal, and vagus nerves recieve signals from the gustatory cells.If an action potential is generated, these cranial nerves will relay information to the next neuron in the solitary nucleus of the medulla oblongata . From there, the axons project to the thalamus and then to the gustatory cortex in the parietal lobe or the insula. Olfactory information affects taste perception by: converging together with the gustatory information in the cerebrum to give us a full profile of what we are eating.

Do you think smell or taste is more important to our survival? Use evidence of neuroanatomy to support or defend your claim

I think smell is more important to survival because of its direct synapse with the limbic system that forms strong memories of toxic things. it also can trigger the vomiting center in the medulla which can effectively prevent us from eating something before we have ingested the toxic substance.

1. What is olfaction? What is the olfactory epithelium (generally)? When an odorant particle enters the nose, it dissolves in the olfactory mucous and then interacts with the receptors. Are the receptor cells a cranial nerve (if yes, which one)? What kind of receptor cells are the olfactory receptors (chemoreceptors, thermoreceptors etc)? Do you have the same olfactory receptor cells your entire life? Are the receptor cells sensitive to small amounts of all odors (meaning, if you have 3 molecules of one "dangerous" odor and 3 molecules of another benign odor, will they both trigger the same intensity of response in your olfactory receptors)? a. Complete the blanks to describe the olfactory pathway. If the stimulation is sufficient, an action potential is generated in the olfactory receptor cells (CN ____) which then first synapse in the ___________ ___________. From there, signals are sent to the olfactory cortex in the ___________ & _________ lobes. Along the way, information is sent to _________ system which is why smell is so strongly associated with memory. b. How does this pathway differ from all other sensory pathways?

Olfaction is the sense of smell. Olfactory epithelium is the little patch responsible for this sense and is cranial nerve I in the nose and these cranial nerves are the actual receptors themselves. They are found in the roof of the nasal cavity. When an odorant particle enters the nose and dissolves into the mucus, it interacts with the receptor cells which are cranial nerve I, the olfactory nerve. These are chemoreceptors, which are very regenerative cells, so not the same receptor cells from birth. receptor cells are very sensitive and also combine with nocciceptors from cranial nerve 5 in the nose which amonia and hot peppers can trigger. There are different thresholds for different toxicities of odorants A)Receptors= CNI, which first synapses in the olfactory bulb. From there, signals are sent to the olfactory cortex in the frontal lobe and the temporal lobe. It is the only path of sensory information that can bypass the thalamus. Along the way, information is sent to the limbic system, which is why smell is so strongly associated with memory. B) this is different than most sensory paths because it skips the synapse at the thalamus and goes straight to the cerebral cortex. This is why smell is not involved in stimulating the RAS, it doesn't use the same pathway as other senses.

8. Describe the path of light as it moves through the eye to the fovea. What structures does it pass through on the way? a. What structure can change the amount of light entering the eye? How does it do this? b. How can the lens change the path of light? Why is this important? How do the ciliary muscles control the shape of the lens?

light passes through the cornea, through the pupil, past the lens where it is bent and focused on the fovea centralis in the center of the macula lutea. The light hits the retina and stimulates photoreceptor which communicate with bipolar cells which send their signals to the ganglion cells that send the info out the optic nerve through the optic disc at the back of the eye. A.) the pupil is where light passes through, so the iris uses round sphincter pupillae muscles to constrict via parasympathetic, or radial dilator pupillae to dilate the eye via sympathetic. B.) The lens bends light to focus it on the retina using the ciliary body.

What is adaptation in the olfactory and gustatory senses? Think of the smell of cows early in the morning at OSU...

persistant smells and taste your brain becomes accustomed to so that you no longer notice the smell or you need higher glucose intake for the same response or taste when you eat sugar all the time.