exam 3

Olfaction: Is it relayed through the thalamus?

thalamus (remember that it does not relay olfactory information). Olfaction goes directly to the primary olfactory cortex.

another word for midbrain

mesencephalon

What is the white of the eye?

sclera

Facial Nerve (VII)

anterior 2/3 of tongue

"Nerves" are found in the ______ while "tracts" are found in the ________.

CNS, PNS

cis-retinal

In darkness, retinal has a bent shape called

Memorizing cranial nerves Tips

Olfactory Cranial Nerve 1: you have 1 nose Optic Cranial Nerve 2: you have 2 eyes Oculomotor Cranial Nerve 3: oculo=eye and motor=movement Trochlear Nerve 4: Trochlea means pully Abducens (6): ABDUCTS eye lateral rectus Vestibulocochlear: vestibulo=balance and cochlear=hearing Glosso (tongue) pharyngeal (throat) Hypoglossal: glosso=tongue

Broca's are and Wernicke's area

broca's area is more anterior

The third part of the lecture reviews how changes in ion movements leads to action potentials or inhibits them. This segment also discusses how low levels of ions in your blood can affect your ion channels (15 minutes).

https://spu.hosted.panopto.com/Panopto/Pages/Viewer.aspx?id=24cf18b0-cd1a-4aa4-ac52-ac69000a870a&start=undefined

The first part of the lecture provides you with background information about the divisions of the nervous system. This part also discusses why and how you can repair a damaged peripheral nerve, but discusses how and why it's more difficult to repair an axon in the CNS (13 minutes).

https://spu.hosted.panopto.com/Panopto/Pages/Viewer.aspx?id=2a570698-e7e7-4a44-ad95-ac690001e768&start=undefined

what extrinsic eye muscle raises eyebrows?

levator

visual field pathway

half of info from each eye crosses over. The info from the nasal part of field of vision stays on same side and the temporal part of field of vision crosses over.

video on the cerebellum diencephalon. This segment contains many review questions about material in previous segments (10 minutes). x

https://spu.hosted.panopto.com/Panopto/Pages/Viewer.aspx?id=0b08e640-0dbe-4f87-a696-ac60005358b4&start=undefined

Role of the ciliary processes of eye?

produce aqueous humor

what controls superior oblique extrinsiic eye muscle?

trochlear nerve

cranial nerves image

when labeling cranial nerves image, the mnemonic device applies going in the direction from the frontal lobe to the occipital lobe except for cranial nerve 12, which comes just before 10 and 11.

optic disc (blind spot)

where the optic nerve exits the eye, ganglion cells

what is the lateral canthus?

where eyelids meet

Rods in the light

-Light bleaches rhodopsin molecules -Sodium channels close -Sodium ions cannot enter rods, and, as a result, the rods become hyper polarized Opsin decreases CGMP

Rods in the dark

-Rhodopsin molecules are inactive -Sodium channels are kept open -Sodium ions flow into the rods, partially depolarizing them.They are inhibited with IPSP and have high cGMP

Composition of Rhodopsin

Retinal+opsin (changes shape when struck by light)

Cranial Nerve Mnemonics 02 (Sensory, Motor or Both)

Some Say Money Matters, But My Brother Says Big Brains Matter More

what converts sound waves to neural signals?

cochlea

glossopharyngeal nerve IX

posterior 1/3 of tongue

Understand which ion channels open and close during an action potential and when each opens and closes AND WHERE EACH IS LOCATED. Hint: There are seven times as many voltage-gated sodium channels at the trigger zone at the axon hillock than elsewhere on the neuron's cell body.

. For example, in a neuron, chemically gated ion channels are located on the cell body and dendrites. Voltage-gated Na+ and K+ channels are found along the axon. Additionally, voltage-gated Ca2+ channels occur at axon terminals. Later sections will show how these differences in distribution affect the way that neurons function.

Reticular Formation

A diffuse network of gray matter that extends the entire length of the brainstem (medulla oblongata to the midbrain). The reticular formation is a closely intermingled mass of gray and white matter that contains embedded nuclei. It extends throughout the central core of the medulla oblongata and into the diencephalon and plays a role in autonomic (breathing, blood pressure, and thermoregulation) functions, endocrine functions, as well as body posture, skeletomuscular reflex activity, alertness, and sleep.

What happened to Phineas Gage and why did it have this effect?

A tamping iron went through his brain during railroad construction but he regained conciousness within a few minutes. He survived, yet his personality was radically changed since the frontal lobe is responsible for planning/decision-making (animalistic).

The insular lobe

The 5th hidden responsible for speech, cravings, and taste

The Brainstem

The diencephalon is a structural and functional link between the cerebral hemispheres and the brainstem. The brainstem contains a variety of important processing centers and nuclei (clearly distinguishable masses of brain neurons) that relay information headed to or from the cerebrum or cerebellum. brainstem includes the midbrain, pons, and medulla oblongata.

You should be able to describe how motor information travels from the precentral gyrus to a muscle. Which brain areas are involved and what do they do? How does information travel from the brain to a muscle.

The surface of the precentral gyrus is the primary motor cortex (Figure 14-16a). Neurons of the primary motor cortex direct voluntary movements by controlling somatic motor neurons in the brainstem and spinal cord. These cortical neurons are called pyramidal cells, because their cell bodies resemble little pyramids. The primary motor cortex is like the keyboard of a piano. If you strike a specific piano key, you produce a specific sound. Similarly, if you stimulate a specific motor neuron in the primary motor cortex, you generate a contraction in a specific skeletal muscle.

split brain experiment

a condition resulting from surgery that isolates the brain's two hemispheres by cutting the fibers (mainly those of the corpus callosum) connecting them. This quells seizures.

What is melanopsin?

a pigment that is in a small subset of ganglion in the retina that is sensitive to blue light and repsonsible for poor sleep when looking at screens before bed

what controls lateral rectus extrinsic eye muscle?

abducens

structure of a neuron image

ach such neuron has four general regions: a large cell body; several short, branched dendrites; a single, long axon; and terminal branches of the axon called telodendria

why can humans see color?

because pigments in cones respond to different color wavelengths

Where is the anterior chamber?

between cornea and iris

Where is the posterior chamber located?

between iris and lens

The fourth part of the lecture reviews the material in previous segments, introduces serotonin signaling pathways, and explains the concepts of EPSPs and IPSPs (17 minutes)

https://spu.hosted.panopto.com/Panopto/Pages/Viewer.aspx?id=1d534df3-21c2-420a-84be-ac69001239ca&start=undefined

Four major brain regions

the cerebrum, cerebellum, diencephalon, and brainstem

trans-retinal

the form of retinal after it takes in light (straight)

Are rods or cones more sensitive to light?

Rods are more sensitive to light and are responsible for night vision.

Be familiar with the different types of fibers (association fibers, commissural fibers, and projection fibers). What is the corpus callosum? What happens in a split brain patient? Which functions are lateralized to each side of the brain? You might want to review by playing the split brain Nobel prize game (https://educationalgames.nobelprize.org/educational/medicine/split-brain/splitbrainexp.html).

The interior of the cerebrum consists mostly of white matter. We can classify the axons of white matter as association, commissural, or projection fibers (Figure 14-14). Association fibers interconnect areas of cerebral cortex within a single cerebral hemisphere. Shorter association fibers are called arcuate (AR-kyū-āt) fibers, because they curve in an arc to pass from one gyrus to another. Longer association fibers are organized into discrete bundles, or fasciculi (fah-SIK-yū-lī). The longitudinal fasciculi connect the frontal lobe to the other lobes of the same hemisphere (Figure 14-14a). Commissural (kom-ih-SŪR-ul; commissura, crossing over) fibers interconnect and permit communication between the cerebral hemispheres. Bands of commissural fibers linking the hemispheres include the corpus callosum and the anterior commissure (Figure 14-14b). The corpus callosum alone contains more than 200 million axons, carrying some 4 billion impulses per second! Projection fibers link the cerebral cortex to the diencephalon, brainstem, cerebellum, and spinal cord. All projection fibers pass through the diencephalon. There, axons heading to sensory areas of the cerebral cortex pass among the axons descending from motor areas of the cortex. In gross dissection, the ascending fibers and descending fibers look alike. The entire collection of projection fibers is known as the internal capsule (see Figure 14-14b). The corpus callosum is A large bundle of axons that links centers in the left and right cerebral hemispheres allowing them to communicate. As mentioned, each of the two cerebral hemispheres is responsible for specific functions that are not ordinarily performed by the opposite hemisphere, a type of specialization known as hemispheric lateralization. In most people, the left hemisphere (intelle the specialized language areas of the brain and is responsible for language-based skills. For example, reading, writing, and speaking depend on processing done in the left cerebral hemisphere. In addition, the premotor cortex involved with hand movements is larger on the left side for right-handed people than for left-handed people. The left hemisphere is also important in performing analytical tasks, such as mathematical calculations and logical decision making. The right cerebral hemisphere analyzes sensory information and relates the body to the sensory environment. Interpretive centers in this hemisphere permit you to identify familiar objects by touch, smell, sight, or taste. For example, the right hemisphere plays a dominant role in recognizing faces and in understanding three-dimensional relationships. It is also important in analyzing the emotional context of a conversation—for instance, distinguishing between the threat "Get lost!" and the question "Get lost?" Individuals with a damaged right hemisphere may be unable to add emotional inflections to their own words. Left hemisphere=intellect, right hemisphere=perception

Which cells are activated in the light? Which cells are inhibited in the light? Why is vitamin A important? What causes bleaching of photoreceptors?

These specialized cells are called photoreceptors. There are 2 types of photoreceptors in the retina: rods and cones. Vitamin A is needed to activate Rhodopsin. Rhodopsin is broken apart into retinal and opsin through a process called bleaching. A light shone on the center of ganglion cell will excite it and a light shone around it will inhibit it.

Midbrain: corpora quadrigemina (a.k.a. superior and inferior colliculus), red nucleus, substantia nigra, reticular formation (which is also in other parts of the brain stem)

. The tectum, or roof of the midbrain, is the region posterior (dorsal) to the cerebral aqueduct. It contains two pairs of sensory nuclei known collectively as the corpora quadrigemina ("4 bodies). These nuclei, the superior and inferior colliculi, process visual and auditory sensations. Each superior colliculus (ko-LIK-ū-lus; colliculus, hill) receives visual inputs from the lateral geniculate body of the thalamus on that side. Each inferior colliculus receives auditory input from nuclei in the medulla oblongata and pons. Some of this information may be forwarded to the medial geniculate body of the thalamus on the same side. The superior colliculi control the reflex movements of the eyes, head, and neck in response to visual stimuli, such as a bright light. The inferior colliculi control reflex movements of the head, neck, and trunk in response to auditory stimuli, such as a loud noise.The red nucleus contains numerous blood vessels (and iron), which give it a rich red color. This nucleus receives information from the cerebrum and cerebellum, and issues subconscious motor commands that affect upper limb position and background muscle tone. The substantia nigra (NĪ-gruh; nigra, black) is the largest midbrain nucleus. It lies lateral to the red nucleus. The neurons of the substantia nigra release the neurotransmitter dopamine. p. 420 The gray matter in this region contains darkly pigmented cells, giving it a black color. The pigment is melanin and here it is a by-product of dopamine synthesis. The substantia nigra inhibits activity of the basal nuclei in the cerebrum. The basal nuclei are involved in the subconscious control of muscle tone and learned movements. As discussed in Section 14-9, Parkinson's disease is characterized by the loss of neuronal activity in the substantia nigra.. Although the reticular formation extends the length of the brainstem, its headquarters resides in the midbrain. The midbrain also contains the reticular activating system (RAS), a specialized component of the reticular formation. Stimulation of the RAS makes you more alert and attentive; damage to the RAS produces unconsciousness. We will consider the role of the RAS in maintaining consciousness in Chapter 16. reticular formation is the group of nuclei scattered throughout brainstem that regulates cyclic/sleep-wake cycle and keeps you awake.

Review the structure & function of the synaptic cleft. Review what happens to neurotransmitters after they are released (e.g. ACh, serotonin, norepinephrine).

A chemical synapse is where one neuron sends chemical signals to another cell, often a second neuron. Every chemical synapse involves two cells: (1) the axon terminal of the presynaptic cell, which sends a message, and (2) the postsynaptic cell, which receives the message. A narrow space called the synaptic cleft separates the two cells. The presynaptic cell typically releases neurotransmitters. The neurotransmitters then flood the synaptic cleft and bind to receptors on the postsynaptic plasma membrane, changing its permeability and producing graded potentials. The mechanism is comparable to that of the neuromuscular junction

Dermatomes: know what these are and why they might be used in a clinical setting. Remember that dermatomes show sensory innervation, but not motor output.

A dermatome is the specific bilateral region of the skin surface monitored by a single pair of spinal nerves. Each pair of spinal nerves supplies its own dermatome. Dermatomes are clinically important because damage or infection of a spinal nerve or spinal ganglion produces a loss of sensation in the corresponding region of the skin. Additionally, characteristic signs may appear on the skin supplied by that specific nerve. Peripheral neuropathies are regional losses of sensory and motor function most often resulting from nerve trauma or compression. (If your arm or leg has ever "fallen asleep" after you leaned or sat in an uncomfortable position, you have experienced a mild, temporary version of this disorder.) The location of the affected dermatomes provides clues to the location of injuries along the spinal cord, but the information is not precise. More exact conclusions can be drawn if there is loss of motor control, based on the origin and distribution of the peripheral nerves originating at nerve plexuses.

Review the mechanism by which you can acquire Parkinson's disease from drug use. What is deep brain stimulation and how does it work?

Caused by contaminated heroin that contained MPTP. In deep brain simulation a hole is drilled in brain and a wire is attched to basal nuclei that sends electrical impulsesto basal nuclei and trigger blood flow that causes NTs to be released which correct the abnormal basal nuclei activity.

What is an epidural injection?

Clinical Note Anesthesia Anesthetics are often injected into the epidural space. Introduced in this way, a drug should affect only the spinal nerves in the immediate area of the injection. The result is a regional pain reliever (analgesic) called epidural anesthesia, which blocks pain sensations. This procedure can be done either peripherally, as when skin lacerations are sewn up, or at sites around the spinal cord for more widespread anesthetic effects, as during labor and delivery. An epidural anesthetic has at least two advantages: (1) It affects only the spinal nerves in the immediate area of the injection; and (2) it provides mainly sensory anesthesia. Local anesthetics can also be introduced as a single dose into the subarachnoid space of the spinal cord. This procedure is commonly called spinal anesthesia. The effects include both temporary muscle paralysis and sensory loss. These effects tend to spread as the movement of cerebrospinal fluid distributes the anesthetic along the spinal cord. Problems with overdosing are seldom serious, because controlling the patient's position during administration can limit the distribution of the drug. Breathing continues even if all thoracic and abdominal segments have been paralyzed because the upper cervical spinal nerves control the diaphragm.

Review the diseases of the eye: glaucoma, macular degeneration. What is lasik?

Clinical Note Glaucoma If aqueous humor cannot drain into the scleral venous sinus, intra-ocular pressure rises due to the continued production of aqueous humor, and glaucoma results. The sclera is a fibrous coat, so it cannot expand like an inflating balloon, but it does have one weak point—the optic disc, where the optic nerve penetrates the wall of the eye. Gradually the increasing pressure pushes the optic nerve outward, damaging its nerve fibers. When the intra-ocular pressure has risen to roughly twice the normal level, the distortion of the optic nerve fibers begins to interfere with the propagation of action potentials, and peripheral vision begins to deteriorate. If this condition is not corrected, tunnel vision and then complete blindness may result. Glaucoma is a problem with movement of aqeous humor through schlemm. Although the primary factors responsible are not known, glaucoma is relatively common. For this reason, most eye exams include a test of intra-ocular pressure. Glaucoma may be treated by topical drugs that constrict the pupil and tense the edge of the iris, making the surface more permeable to aqueous humor. Surgical correction involves perforating the wall of the anterior chamber to encourage drainage. age-related macular degeneration: A disease associated with aging that gradually destroys sharp, central vision by affecting the macula, the part of the eye that allows a person to see fine detail. It is painless and in some cases can slowly worsen over time, causing little concern to the person, or it can rapidly progress and may cause blindness in both eyes. It is the leading cause of blindness in persons over the age of 60. It has two forms, wet and dry. Lasik is corneal remodeling

What is the effect of marijuana use on your brain?

Decreased intellect, significant drop in IQ

How is visual information processed in the retina? How does visual information travel into the brain? What leads to depth perception? Make sure that you understand which information from each eye decussates and which stays on the same side of the brain.

Depth perception is resolved by comparing relative positions of objects between the left- and right-eye images. (Figure 17-20). Visual data from the left half of the combined field of vision arrive at the visual cortex of the right occipital lobe. Data from the right half of the combined field of vision arrive at the visual cortex of the left occipital lobe..

Lobes of the brain and main functions.

Frontal lobe: mood, motor, motivation, agression, planning (actions) occipital: vision (vision) temporal: memory, hearing, learning (intellect) parietal: touch, pain, body position (feeling)

What are the major structures in each plexus?

Only the anterior rami form plexuses. These four major plexuses are the (1) cervical plexus, (2) brachial plexus, (3) lumbar plexus, and (4) sacral plexus (Figure 13-9). The nerves arising at these plexuses contain sensory as well as motor fibers because these nerves form from the fusion of anterior rami . brachial plexus: A network formed by branches of spinal nerves C5−T1 en route to innervating the upper limb. The cervical plexus consists of the anterior rami of spinal nerves C1-C5 (Figures 13-9, 13-10). The branches of the cervical plexus innervate the muscles of the neck and extend into the thoracic cavity, where they control the diaphragm. The phrenic (FREN-ik) nerve is the major nerve of the cervical plexus. The left and right phrenic nerves supply the diaphragm, a key breathing muscle. Other branches of this nerve plexus are distributed to the skin of the neck and the superior part of the chest. The Lumbar and Sacral Plexuses The lumbar plexus and the sacral plexus arise from the lumbar and sacral segments of the spinal cord, respectively. The nerves arising at these plexuses innervate the pelvic girdle and lower limbs. The lumbar plexus contains axons from the anterior rami of spinal nerves T12-L4. The major nerves of this plexus are the genitofemoral nerve, the lateral femoral cutaneous nerve, and the femoral nerve. The sacral plexus contains axons from the anterior rami of spinal nerves L4-S4. Two major nerves arise at this plexus: the sciatic (sī-AT-ik) nerve and the pudendal nerve. The sciatic nerve passes posterior to the femur, deep to the long head of the biceps femoris. As it approaches the knee, the sciatic nerve divides into two branches: the fibular nerve (or peroneal nerve) and the tibial nerve. The sural nerve, formed by branches of the fibular nerve, is a sensory nerve innervating the lateral portion of the foot. A section of this nerve is often removed for use in nerve grafts.

Which cranial nerves are involved in vision, eye movements, and pupillary constriction?

Optic Nerves carry visual information from special sensory ganglia in the eyes. The Oculomotor nerve controls eye movement (left and right) and pupillary contriction. Individuals with damage to this nerve often complain of pain over the eye, droopy eyelids, and double vision, because the movements of the left and right eyes cannot be coordinated properly. The oculomotor nerve also delivers preganglionic autonomic fibers to neurons of the ciliary ganglion. These neurons control intrinsic eye muscles. These muscles change the diameter of the pupil, adjusting the amount of light entering the eye. They also change the shape of the lens to focus images on the retina. A trochlear nerve (IV), the smallest cranial nerve, innervates the superior oblique of each eye(up/down). The trochlea is a pulley-shaped, ligamentous sling. Each superior oblique passes through a trochlea on its way to its insertion on the surface of the eye. An individual with damage to cranial nerve IV or to its nucleus has difficulty looking down and to the side.The abducens (ab-DŪ-senz) nerves (VI) innervate the lateral rectus, the sixth pair of extrinsic eye muscles. Contraction of the lateral rectus makes the eye look to the side. In essence, the abducens causes abduction of the eye. oculomotor controls 4 of the 6 extrinsic eye muscles.

How do SSRIs work? What is serotonin syndrome?

Serotonin (ser-ō-TŌ-nin) is another important CNS neurotransmitter. Inadequate serotonin production can have widespread effects on a person's attention and emotional states and may be responsible for many cases of severe chronic depression. Fluoxetine (Prozac), paroxetine (Paxil), sertraline (Zoloft), and related antidepressant drugs inhibit the reabsorption of serotonin by axon terminals (hence their classification as selective serotonin reuptake inhibitors, or SSRIs). This inhibition leads to increased serotonin concentration at synapses, and over time, the increase may relieve the symptoms of depression.Serotonin syndrome is when your body has too much of a chemical called serotonin, usually because of a medication or combinations of medications. It can be fatal.

Feel confident about basic neurophysiology: be able to explain what happens before, during, and after an action potential. Be able to list steps in order. You might want to write out the steps of an action potential using your book, scramble them, and try to place them in order.

Sodium-potassium because sodium gates open first. DPH (depolarization, repolarization, hyperpolarization)

Basal nuclei/ganglia: be able to name the main structure and describe the functions of this group of cell bodies.

Structure of the Basal Nuclei The basal nuclei are masses of gray matter that lie within each hemisphere deep to the floor of the lateral ventricle (Figure 14-15a). They are embedded in the white matter of the cerebrum. The radiating projection fibers and commissural fibers travel around or between these nuclei. They are Nuclei of the cerebrum that are important in the subconscious control of skeletal muscle activity..

What is the difference between the absolute and relative refractory period? Why does each occur?

The Refractory Period The plasma membrane does not respond normally to additional depolarizing stimuli from the time an action potential begins until the resting membrane potential has been reestablished. This period is known as the refractory period of the membrane. From the moment the voltage-gated sodium ion channels open at threshold until sodium ion channel inactivation ends, the membrane cannot respond to further stimulation because all the voltage-gated sodium ion channels either are already open or are inactivated. This first part of the refractory period, called the absolute refractory period, lasts 0.4-1.0 msec. The relative refractory period begins when the sodium ion channels regain their normal resting condition, and continues until the membrane potential stabilizes at the resting level. Another action potential can occur during this period if the membrane is sufficiently depolarized. That depolarization, however, requires a larger-than-normal stimulus, because (1) the local current must deliver enough Na+ to counteract the exit of positively charged K+ through open voltage-gated K+ channels, and (2) the membrane is hyperpolarized to some degree through most of the relative refractory period.

Cerebellum: know its functions and be able to identify the peduncles (including the structures that they connect), arbor vitae, flocculonodular lobe, vermis, anterior lobe, posterior lobe. What happens if you never develop a cerebellum?

The cerebellum has a complex, highly convoluted surface composed of gray matter called the cerebellar cortex. The folia or folds of the cerebellum surface, are less prominent than the folds in the surfaces of the cerebral hemispheres. The primary fissure separates the anterior and posterior lobes. Along the midline, a narrow band of cortex known as the vermis separates the cerebellar hemispheres. The slender flocculonodular lobe lies between the roof of the fourth ventricle and the cerebellar hemispheres and vermis. The internal white matter of the cerebellum forms a branching array that in sectional view resembles a tree. Anatomists call it the arbor vitae or "tree of life". It connects the cerebellar cortex and nuclei with the tracts of white matter that form the cerebellar peduncles. hemispheres as the superior, middle, and inferior cerebellar peduncles: The superior cerebellar peduncles link the cerebellum with nuclei in the midbrain, diencephalon, and cerebrum. The middle cerebellar peduncles are connected to the transverse pontine fibers. The middle cerebellar peduncles also connect the cerebellar hemispheres with sensory and motor nuclei in the pons. The inferior cerebellar peduncles communicate between the cerebellum and nuclei in the medulla oblongata and carry ascending and descending cerebellar tracts from the spinal cord. Cerebellar agenesis is a rare condition in which a brain develops without the cerebellum. ... The condition is not fatal on its own, but people born without a cerebellum experience severe developmental delays, language deficits, and neurological abnormalities.Most can walk (though they may need a cane), but fine motor skills like writing, typing, and speaking are a challenge. Their speech is never quite perfect and their handwriting is always a bit off. Their reaction times are slow and they can't drive cars or ride bikes, there's just too much going on.

What is decussation and why does it happen?

The gracile nucleus and the cuneate nucleus pass somatic sensory information to the thalamus. Tracts leaving these brainstem nuclei cross to the opposite side of the brain before reaching their destinations. This crossing over is called a decussation (dē-kuh-SĀ-shun; decussatio, crossing over), and the site is the decussation of pyramids. Also bc embryo twisted.

The Cerebrum

The largest/heaviest portion of the adult brain is the cerebrum (but less neurons). Conscious thoughts, sensations, intellect, memory, and complex movements all originate in the cerebrum. It is made up of large, paired left and right cerebral hemispheres. The surfaces of the cerebral hemispheres are highly folded and covered by a collection of neurons that form a thin superficial layer of gray matter called the cerebral cortex. the cortex forms a series of rounded elevations called gyri that increase its surface area. The gyri are separated by shallow grooves called sulci or by deeper grooves called fissures. Fissures separate larger brain regions.

Limbic system: be able to name the main structure and describe the functions of this group of cell bodies.

The limbic system is a group of nuclei and tracts that functions in emotion, motivation, and memory. Figure 14-12 shows the major parts of the limbic system, which includes nuclei and tracts along the border (limbus, edge) between the cerebrum and diencephalon. Functions of the limbic system include (1) establishing emotional states; (2) linking the conscious, intellectual functions of the cerebral cortex with the unconscious and autonomic functions of the brainstem; and (3) facilitating memory storage and retrieval. The cerebral cortex enables you to perform complex tasks, but it is largely the limbic system that makes you want to do them. For this reason, the limbic system is also known as the motivational system.

Medulla: autonomic nuclei controlling visceral activities (e.g. solitary nucleus, cardiovascular centers, respiratory rhythmicity center), sensory and motor nuclei of cranial nerves VIII-IX, relay stations along sensory and motor pathways (olivary nucleus, nucleus gracilis, nucleus cuneatus)

The medulla oblongata relays signals between the rest of the brain and the spinal cord. As mentioned, the medulla oblongata is the most inferior of the brainstem regions. The medulla oblongata includes three groups of nuclei that we introduce here and discuss in later chapters (Figure 14-6). First are nuclei and processing centers that control visceral functions. The medulla oblongata is a center for the coordination of complex autonomic reflexes. Second are sensory and motor nuclei of the CNS. Third are relay stations that move all communication between the brain and spinal cord by tracts that ascend or descend through the medulla oblongata. Reflex Centers: Autonomic and Reflex Activity. The reticular formation is a closely intermingled mass of gray and white matter that contains embedded nuclei. It extends throughout the central core of the medulla oblongata and into the diencephalon and plays a role in autonomic (breathing, blood pressure, and thermoregulation) functions, endocrine functions, as well as body posture, skeletomuscular reflex activity, alertness, and sleep. There are two major groups of reflex centers in the medulla oblongata, cardiovascular and respiratory. The cardiovascular centers adjust the heart rate, the strength of cardiac contractions, and the flow of blood through peripheral tissues. (In terms of function, the cardiovascular centers are subdivided into cardiac and vasomotor centers, but their anatomical boundaries are difficult to determine.) The respiratory rhythmicity centers set the basic pace for respiratory movements. Their activity is regulated by inputs from the respiratory centers of the pons. Sensory and Motor Nuclei of Cranial Nerves. The medulla oblongata contains sensory and motor nuclei associated with five of the cranial nerves (VIII, IX, X, XI, and XII). These cranial nerves provide motor commands to muscles of the pharynx, neck, and back as well as to the visceral organs of the thoracic and peritoneal cavities. Cranial nerve VIII carries sensory information from receptors in the internal ear to the vestibular (involved with balance) and cochlear (involved with hearing) nuclei, which extend from the pons into the medulla oblongata. Relay Stations along Sensory and Motor Pathways. The gracile nucleus and the cuneate nucleus pass somatic sensory information to the thalamus. Tracts leaving these brainstem nuclei cross to the opposite side of the brain before reaching their destinations. This crossing over is called a decussation (dē-kuh-SĀ-shun; decussatio, crossing over), and the site is the decussation of pyramids. Decussation is when info crosses from one side of brain to other side due to embryo twisting during development. In addition, a few important paired nuclei are found in the medulla oblongata. The solitary nuclei (nuclei of solitary tract) are the visceral sensory nuclei, receiving information from the spinal and cranial nerves. This information is integrated and forwarded to other autonomic centers in the medulla oblongata and elsewhere. The inferior olivary complex consists of three nuclei that collectively form the inferior olivary nucleus. They relay information to the cerebellar cortex about somatic motor commands as they are issued by motor centers at higher levels. The bulk of the olivary nuclei creates the olives, prominent olive-shaped bulges along the ventrolateral surface of the medulla oblongata. You need medulla oblongata to function in order to live.

Components of Brainstem and details

The midbrain contains nuclei that process visual and auditory information and control reflexes triggered by these stimuli. For example, your immediate, reflexive responses to a loud, unexpected noise (eye movements and head turning) are directed by nuclei in the midbrain. This region also contains centers (groups of nerve cells governing a specific function) that help maintain consciousness (see Figure 14-1d). The pons of the brain connects the cerebellum to the brainstem (pons is Latin for "bridge"). In addition to tracts (collections of CNS axons) and relay centers, the pons contains nuclei involved with somatic and visceral motor control (see Figure 14-1e). The medulla oblongata connects the brain to the spinal cord. Near the pons, the posterior wall of the medulla oblongata is thin and membranous. The inferior portion of the medulla oblongata resembles the spinal cord in that it has a narrow central canal. The medulla oblongata relays sensory information to the thalamus and to centers in other portions of the brainstem. The medulla oblongata also contains major centers that regulate autonomic function, such as heart rate, blood pressure, and digestion (see Figure 14-1f).

The Diencephalon

The other major anatomical regions of the brain can best be examined after the cerebral and cerebellar hemispheres have been removed. The walls of the diencephalon (dī-en-SEF-a-lon; dia, through + encephalos, brain) are composed of the thalamus and hypothalamus. The thalamus contains relay and processing centers for sensory information. The hypothalamus (hypo-, below) is the floor of the diencephalon. It contains centers involved with emotions, autonomic function, and hormone production. The infundibulum, a narrow stalk, connects the hypothalamus to the pituitary gland, a part of the endocrine system. This connection integrates the nervous and endocrine systems.

Pons: nuclei for cranial nerves, apneustic/pneumotaxic centers, nuclei and tracts passing through to cerebellum, nuclei and tracts to other portions of CNS

The pons contains four groups of components: Sensory and Motor Nuclei of Cranial Nerves. These cranial nerves (V, VI, VII, and VIII) innervate the jaw muscles, the anterior surface of the face, one of the extrinsic eye muscles (the lateral rectus), and the sense organs of the internal ear (the vestibular and cochlear nuclei). Nuclei Involved with the Control of Respiration. Research on laboratory animals has identified regions in the medulla and pons, known as centers, that appear to modify breathing activities. Two pontine centers, the apneustic (ap-NŪS- tik) center located in the middle or lower pons, and the pneumotaxic (nū-mō-TAK-sik) center located in the rostral pons, process information originating in the respiratory rhythmicity centers of the medulla oblongata. These centers are further discussed in Chapter 23. Nuclei and Tracts That Process and Relay Information Sent to or from the Cerebellum. The pons links the cerebellum with the brainstem, cerebrum, and spinal cord. Ascending, Descending, and Transverse Pontine Fibers. Longitudinal tracts interconnect other portions of the CNS. Tracts of the cerebellum (middle cerebellar peduncles) are connected to the transverse pontine fibers, which cross the anterior surface of the pons. These fibers are axons that link nuclei of the pons (pontine nuclei) with the cerebellum of the opposite side.

You should also know the pathway of sensory information (posterior column pathway) that is relayed through the nucleus gracilis and cuneatus to the thalamus and primary somatosensory cortex (postcentral gyrus).

The posterior column pathway, shown in Spotlight Figure 15-8b, carries sensations of fine touch, vibration, pressure, and proprioception. The spinal tracts involved are the left and right gracile fasciculus (gracilis, slender) and the left and right cuneate fasciculus (cuneus, wedge shaped). On each side of the posterior median sulcus, the gracile fasciculus is medial to the cuneate fasciculus (see Figure 15-7). The axons of the first-order neurons reach the CNS within the posterior roots of spinal nerves and the sensory roots of cranial nerves. The axons ascending within the posterior column are organized according to the region innervated. Axons carrying sensations from the inferior half of the body ascend within the gracile fasciculus and synapse in the gracile nucleus of the medulla oblongata. Axons carrying sensations from the superior half of the trunk, upper limbs, and neck ascend in the cuneate fasciculus and synapse in the cuneate nucleus. p. 474 The posterior column pathway, shown in Spotlight Figure 15-8b, carries sensations of fine touch, vibration, pressure, and proprioception. The spinal tracts involved are the left and right gracile fasciculus (gracilis, slender) and the left and right cuneate fasciculus (cuneus, wedge shaped). On each side of the posterior median sulcus, the gracile fasciculus is medial to the cuneate fasciculus (see Figure 15-7). Axons of the second-order neurons of the gracile nucleus and cuneate nucleus decussate in the brainstem as they ascend toward the thalamus. Once on the opposite side of the brain, the axons enter a tract called the medial lemniscus (lemniskos, ribbon). The axons in this tract synapse on third-order neurons in one of the ventral nuclei of the thalamus. p. 481 These nuclei sort the arriving information according to (1) the nature of the stimulus and (2) the region of the body involved. Processing in the thalamus determines whether you perceive a given sensation as fine touch, pressure, or vibration. We then localize the sensation by where it arrives in the primary somatosensory cortex. Sensory information from the toes arrives at the medial end of the primary sensory cortex, and information from the head arrives at the lateral end. When neurons in one portion of your primary somatosensory cortex are stimulated, you become aware of sensations originating at a specific location.

Functions of the tissue of the pre-central gyrus and post-central gyrus. Know what a homunculus is. Be able to explain what happens if you stimulate a specific area of the somatic sensory or motor cortex.

The precentral gyrus of the frontal lobe forms the anterior border of the central sulcus, while the postcentral gyrus of the parietal lobe forms its posterior border. The precentral gyrus is The primary motor cortex of a cerebral hemisphere, located anterior to the central sulcus. The postcentral gyrus is The primary sensory cortex, where touch, vibration, pain, temperature, and taste sensations arrive and are consciously perceived. Researchers have electrically stimulated the primary somatosensory cortex in awake individuals during brain surgery and asked the subjects where they thought the stimulus originated. The results were used to create a functional map of the primary somatosensory cortex known as a sensory homunculus. In a sensory homunculus, the body features are distorted. For example, the face is huge, with enormous lips and tongue, but the back is relatively tiny. These distortions arise because the area of somatosensory cortex devoted to a particular body region is proportional to the density of sensory neurons in the region, not to the region's physical size. In other words, many more cortical neurons are required to process sensory information from the tongue, which has tens of thousands of taste and touch receptors, than to process sensations from the back, where touch receptors are few and far between.The precentral gyrus has this homonculus and areas will feel that sensation even if that part of the body isn't actually being touched.

Review the anatomy of rods and cones. What are the main differences between rods and cones (location in the eye, functions, ease of activation by dim light)? Why do humans have color vision?

The rods and cones of the retina are called photoreceptors because they detect photons, basic units of visible light. Rods provide the central nervous system with information about the presence or absence of photons, with little regard to their wavelength. Cones provide information about the wavelength of arriving photons, giving us the perception of color. Both are located in retina. Rods are more abundant and found in the periphery retina whilst cones are found in the center/fovea. Rod cells are for dim light/night vision while cones are for bright light/day vision.

The diencephalon's 4 main components: thalamus (remember that it does not relay olfactory information), subthalamus (we didn't discuss this), epithalamus (remember the pineal which secretes melatonin to regulate biological rhythms and is involved in jet lag), and hypothalamus—main functions of each as listed in your book & PowerPoint. For the hypothalamus, be able to identify the main functions of the hypothalamus. You do not need to identify the different regions of the hypothalamus on a diagram or be able to match specific areas with their functions.

The walls of the diencephalon are composed of the thalamus and hypothalamus . The thalamus contains relay and processing centers for sensory information. The hypothalamus (hypo-, below) is the floor of the diencephalon. It contains centers involved with emotions, autonomic function, and hormone production. The infundibulum, a narrow stalk, connects the hypothalamus to the pituitary gland, a part of the endocrine system. This connection integrates the nervous and endocrine systems. the thalamus is the final relay point for sensory information ascending to the cerebral cortex. Ascending sensory information from the spinal cord and cranial nerves (other than the olfactory tract) synapses in a nucleus in the left side or right side of the thalamus before reaching the cerebral cortex and our conscious awareness. It acts as a filter, passing on only a small portion of the arriving sensory information. The thalamus also coordinates the activities of the basal nuclei (which we discuss shortly) and the cerebral cortex by relaying information between them.The hypothalamus contains important nuclei that function as control and integrative centers in addition to those associated with the limbic system: secretes 2 hormones, regulates body temp, control autonomic function, Coordination between Voluntary and Autonomic Functions, coordination of Activities of the Nervous and Endocrine Systems, Regulation of Circadian Rhythms, Subconscious Control of Skeletal Muscle Contractions., Production of Emotions and Behavioral Drives..The hypothalamus is floor of the diencephalon; the region of the brain containing centers involved with the subconscious regulation of visceral functions, emotions, drives, and the coordination of neural and endocrine functions. The subthalamus general functions are responsible for include sexuality, food and water intake and maintenance of hydration, and cardiovascular activity.

Where is Broca's area and what is its function? Where is Wernicke's area and what is its function? What is aphasia?

Two important cortical areas with varying functions related to human language are Wernicke's area and Broca's area. Both are primarily associated with the left cerebral hemisphere. Wernicke's area is sensory speech area that understands and thinks of what to say. Wernicke's (VER-nih-kēz) area is near the auditory cortex and is associated with language comprehension. This analytical center receives information from the sensory association areas and plays an important role in your personality by integrating sensory information and coordinating access to visual and auditory memories. Broca's area (motor speech area) is near the motor cortex and is associated with speech production. Broca's area regulates the patterns of breathing and vocalization needed for normal speech. This regulation involves coordinating the activities of the respiratory muscles, the laryngeal and pharyngeal muscles, and the muscles of the tongue, cheeks, lips, and jaws. A person with damage to Broca's area can make sounds but not words. Aphasia (ah-FĀ-zē-ah; a-, without + phasia, speech) is a disorder affecting the ability to speak or read. Global aphasia results from extensive damage to the specialized language areas of the brain or to the associated sensory tracts. Affected individuals are unable to speak, read, or understand speech. Global aphasia often accompanies a stroke that is severe enough to affect a large area of cortex, including the speech and language areas. Recovery is possible, but the process often takes months or even years. Aphasia is when you're brain holds your words hostage.

What are cranial and spinal nerves? Be able to identify and describe the functions of the cranial nerves.

Two useful mnemonics for remembering the names of the cranial nerves in numerical order are "Oh Oh Oh, To Touch And Feel Very Green Vegetables, Ah Heaven!" and "Oh, Once One Takes The Anatomy Final, Very Good Vacations Are Heavenly!" Distal to each spinal ganglion, the sensory and motor roots are bound together into a single spinal nerve just lateral to the intervertebral foramen. The spinal nerve then forms branches containing nerve fibers that carry sensory and/or motor information. These branches include paired communicating structures called rami communicantes (singular, ramus communicans), a posterior ramus, and an anterior ramus (Figure 13-3b). A typical spinal nerve has a white ramus communicans (containing myelinated axons), a gray ramus communicans (containing unmyelinated fibers that innervate glands and smooth muscles in the body wall or limbs), a posterior ramus (providing sensory and motor innervation to the skin and muscles of the back), and an anterior ramus (supplying the ventrolateral body surface, structures in the body wall, and the limbs). Spinal nerves are classified as mixed nerves—that is, they contain both afferent (sensory) and efferent (motor) fibers. As mentioned, there are 31 pairs of spinal nerves, each identified by its association with adjacent vertebrae. For example, we speak of "cervical spinal nerves" or even "cervical nerves" when we make a general reference to spinal nerves of the neck.

What happens when there is damage to the PNS? To the CNS? What is Wallerian degeneration?

What happens when a neuron is injured? It responds to injury in a very limited way, although in general more repair is possible in PNS neurons than in those of the CNS.In the PNS, Schwann cells play a part in repairing damaged nerves. In the process known as Wallerian (vah-LEHR-ē-an) degeneration, the axon distal to the injury site degenerates, and macrophages migrate into the area to clean up the debris (Figure 12-7). The Schwann cells do not degenerate. Instead, they proliferate and form a solid cellular cord that follows the path of the original axon. As the neuron recovers, its axon grows into the site of injury, and the Schwann cells wrap around the axon. If the axon grows alongside the appropriate cord of Schwann cells, it may eventually reestablish its normal synaptic contacts. However, if it stops growing or wanders off in some new direction, normal function will not return. The growing axon is most likely to arrive at its appropriate destination if the cut edges of the original nerve bundle remain in contact. Limited regeneration can occur in the CNS, but the situation is more complicated because (1) many more axons are likely to be involved, (2) astrocytes produce scar tissue that can prevent axon growth across the damaged area, and (3) astrocytes release chemicals that block the regrowth of axons. Damage in the CNS is oftentimes permanent.

Review the locations of gray/white matter within the brain. Understand that the "nuclei" described below (e.g. basal nuclei) are gray matter. What is the difference between a sulcus, gyrus, and a fissure? Where is the central sulcus? The lateral fissure? The longitudinal fissure?

White matter (tracts) is found buried in the inner layer of the brain's cortex, while the grey matter is mainly located on the surface of the brain. The spinal cord is arranged in the opposite way, with grey matter found deep inside its core and the insulating white matter wrapped around the outside. his cerebral cortex forms a series of rounded elevations called gyri (JĪ-rī; singular, gyrus) that increase its surface area. The gyri are separated by shallow grooves called sulci (SUL-sī; singular, sulcus) or by deeper grooves called fissures. Fissures separate larger brain regions. On each hemisphere, the central sulcus, a deep groove, divides the anterior frontal lobe from the more posterior parietal lobe. The basal nuclei are masses of gray matter that lie within each hemisphere deep to the floor of the lateral ventricle They are embedded in the white matter of the cerebrum. The radiating projection fibers and commissural fibers travel around or between these nuclei. White matter is inside brain and grey matter is inside but it's the opposite for the spinal cord. The longitudinal fissure seperates the 2 hemispheres. The central sulcus seperates the frontal and parietal lobe. The lateral fissure seperates the temporal lobe from the frontal and parietal lobe.

Be able to identify the main structures on a picture of a neuron and their functions (especially axon, axon hillock, initial segment, mitochondrion, myelin sheath formed by Schwann cell or oligodendrocyte, cell body/soma, node of Ranvier , presynaptic terminals)

ach such neuron has four general regions: a large cell body; several short, branched dendrites; a single, long axon; and terminal branches of the axon called telodendria. Many oligodendrocytes cooperate in forming a myelin sheath along the length of an axon. Such an axon is said to be myelinated. Each oligodendrocyte myelinates segments of several axons. The fairly large areas of the axon that are wrapped in myelin are called internodes (inter, between). Internodes are typically 1-2 mm in length. The small gaps of a few micrometers that separate adjacent internodes are called nodes, or nodes of Ranvier (rahn-vē-Ā). An axon's collateral branches originate at nodes.

What are dorsal root ganglia?

cell bodies of sensory neurons

Chapters covered in exam

ch 13-ch 17

Understand the differences between depolarization, hyperpolarization, repolarization, action potentials, temporal summation, spatial summation, IPSP, EPSP, axoaxonic synapses.

depolarization: A change in the membrane potential from a negative value toward 0 m V. hyperpolarization: The movement of the membrane potential away from the normal resting potential and farther from 0 mV. action potential: A propagated change in the membrane potential of excitable cells, initiated by a change in the membrane permeability to sodium ions; see also nerve impulse. Temporal summation (tempus, time) is the addition of stimuli occurring in rapid succession at a single synapse that is active repeatedly. Spatial summation occurs when simultaneous stimuli applied at different locations have a cumulative effect on the membrane potential. In other words, spatial summation involves multiple synapses that are active simultaneously. An excitatory postsynaptic potential, or EPSP, is a graded depolarization caused by the arrival of a neurotransmitter at the postsynaptic membrane. An EPSP results from the opening of chemically gated ion channels in the plasma membrane that lead to membrane depolarization. For example, the graded depolarization produced by the binding of ACh is an EPSP. Because it is a graded potential, an EPSP affects only the area immediately surrounding the synapse, as shown earlier in Figure 12-12. We have already noted that not all neurotransmitters have an excitatory (depolarizing) effect. An inhibitory postsynaptic potential, or IPSP, is a graded hyperpolarization of the postsynaptic membrane. For example, an IPSP may result from the opening of chemically gated potassium ion channels. While the hyperpolarization continues, the neuron is said to be inhibited, because a larger-than-usual depolarizing stimulus is needed to bring the membrane potential to threshold. A stimulus that shifts the membrane potential by 10 mV (from −70 mV to −60 mV) would normally produce an action potential, but if the membrane potential were reset at −85 mV by an IPSP, the same stimulus would depolarize it to only −75 mV, which is below threshold. At an axoaxonic synapse, a synapse occurs between the axons of two neurons.

The second lecture segment tests your understanding of the structures of the eye, provides more information about them, and introduces the extrinsic muscles of the eye and reminds you of their cranial nerve innervation (8 minutes).

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The fourth part of the video explains how information enters and leaves your central nervous system (19 minutes). x

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watch this video (14 min) on main divisions of brain x

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The final part of the video explains some of the complex branching patterns of spinal nerves and explains how epidurals work (7 minutes).

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This video is on the case of Phineas Gage and what it tells us about sin and the frontal lobe. I also explain how marijuana affects the brain and explain how brain injuries can lead to aphasia. This segment also introduces the functions of the basal nuclei and explains the biology of Parkinson's disease and Huntington's disease. x

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The final lecture segment focuses on processing of visual information in the retina and the visual cortex. This segment will also talk about how your retina helps you to produce complicated color perception and why you can't see a reddish green color. In the part about the visual pathways, I think that I accidentally said that visual reflexes occur in the thalamus instead of the superior colliculus. Note that the thalamus is the relay station for the sensory information and that the superior colliculus of the midbrain is important for visual reflexes (18 minutes).

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video on locations and functions of the main structures of the brain stem (18 minutes). x

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The second video tutor segment describes the main structures of the ear and their functions. You'll learn how your inner ear helps you to hear and to detect gravity and movement (10 minutes).

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The second part of the lecture provides you with information about the myelin sheath and why it is so important. Multiple sclerosis is also discussed in this segment (11 minutes).

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The second part of the video discusses the effects of deep brain stimulation on Parkinson's disease, discusses the limbic system, and includes some practice questions for you (9 minutes).

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video on the lobes of the brain and reviews material in the previous segments of this presentation (10 minutes). x

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The first video tutor segment describes the main structures of the eye and their functions (10 minutes).

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The first lecture segment describes the main structures of the eye and their functions. Take careful notes because you'll need to identify some of these structures in the next part of the lecture (18 minutes)!

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The third part of the video focuses on the structure of a nerve and introduces the cranial nerves. It also includes a music video for you to watch. This segment will be helpful for you to watch before completing Homework 6 (21 minutes).

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The final part of the lecture explains how antidepressants work and what happens if you have too much serotonin in your system (16 minutes).

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The fourth lecture segment describes visual processing in the retina. How do your photoreceptors change their activity when light is shining on them? Why can't you see after a burst of light enters your eye? Watch this section to find out (15 minutes)!

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The third lecture segment describes the main structures of the retina and their functions and explains the biological basis of colorblindness (13 minutes).

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Review the normal pattern of ion distribution and what happens if you manipulate ion concentrations in the extracellular fluid. What happens with hypokalemia? What happens with hypocalcemia?

hypokalemia is a dangerous reduction in the plasma potassium (K+) ion concentration.HYpocalcemiaexists when the calcium is low. relative distribution of ions across the resting cell's plasma membrane, associate Negative with the iNside and pOsitive with the Outside. The sodium ion concentration is relatively high in the extracellular fluid, but extremely low inside the cell. As a result, there is a strong chemical gradient driving Na+ into the cell (the thinner purple arrow in Figure 12-9c). In addition, the extracellular sodium ions are attracted by the excess of negative charges on the inner surface of the plasma membrane. Hypokalemia symptoms are muscle weakness and sluggish reflexes. Hypocalcemia symptoms are nervousness and uncontrollable muscle contraction due to open sodium channels. Manipulating the permeability of the membrane by altering chloride ions could cause the cell to become hyperpolarized.

Review the factors that determine the membrane's resting potential (concentration and charge gradients). Review which type of ion channel is the most important in maintaining the resting membrane potential.

leak channels are most important in maintaining resting membrane potential.

Understand the biology of myasthenia gravis and multiple sclerosis

myasthenia gravis: A general muscular weakness resulting from a reduction in the number of ACh receptors on the motor end plate.a disease of the neuromuscular junction (NMJ). In people with this autoimmune disease, the immune system mistakenly makes antibodies that damage the acetylcholine (ACh) receptor sites on the surface of the motor end plates of skeletal muscle fibers. The ACh that is released by the axon terminal of the motor neuron cannot find enough intact ACh receptors on which to bind. For this reason, the muscle fiber membrane permeability to sodium ions does not change enough, and the cascade of events leading to muscular contraction is feeble. The result is weakness and fatigability. This weakness improves with rest as the ACh store is built up again. Often the muscles of the eyes, including the eyelids, and other facial muscles are affected first. All voluntary, skeletal muscles can be affected. Multiple sclerosis (skler-Ō-sis; sklerosis, hardness), or MS, is the most common demyelinating disease. It is characterized by recurrent demyelinating episodes that affect axons in the optic nerve, brain, and spinal cord. Although the precise cause of MS is yet to be discovered, myelin becomes the target of an autoimmune reaction. Inflammation occurs at multiple sites where white matter is located. Healing produces multiple scars, which accounts for the name of the disease. Common signs include partial loss of vision and problems with speech, balance, and general motor coordination, including bowel and urinary bladder control. Myelin is important bc it's the insulation around axons thta allpws action potentials to be quickly transmitetted. Nodes of ranvier are between myelin and signal travels between them via nodes.

The Cerebellum

the second-largest part of the brain. is partially hidden by the cerebral hemispheres. Like the cerebrum, the cerebellum has hemispheres covered by a sheet of gray matter called the cerebellar cortex. The cerebellum adjusts ongoing movements by comparing arriving sensations with previously experienced sensations, allowing you to perform the same movements over and over.