A&P Chapter 12

In which of the four divisions of the brain might an injury cause changes in personality? Explain.

Damage to the cerebrum, specifically the frontal lobe, could lead to changes in personality. This is because of association areas such as the prefrontal cortex, which house neurons involved in higher functions like personality and conscience.

Fill in the blanks: The tracts of the posterior columns decussate in the _______________ , whereas the tracts of the anterolateral system decussate in the _____________.

medulla, posterior horn of the spinal cord

Fill in the blanks: The two components of the CNS that are responsible for maintenance of homeostasis are the ________ and the ________ .

hypothalamus; the brainstem reticular formation

Predict the effects of a tumor that secretes excess orexins.

2. Orexins stimulate appetite and wakefulness. Therefore, an individual with such a tumor is likely to experience an increase in appetite and difficulty falling asleep at night.

The condition lissencephaly (lissr-en-SEF-uh-lee; "smooth brain") is characterized by a lack of gyri and sulci in the cerebral cortex, which gives the brain hemispheres a smooth appearance. Predict the effects of such a condition.

3. The gyri and sulci increase the surface area of the cerebral cortex, which in essence allows more neurons to "fit" in a small area. A lack of gyri and sulci severely reduces the surface area of the cerebral cortex and thus the number of neurons located within it.

Ms. Greer sustained major head trauma in an automobile accident. She is unresponsive to sensory stimuli, and scans of her cerebral cortex demonstrate no cortical activity. During a surgical procedure to relieve pressure on her brain, it is discovered that she has sustained major damage to her thalamus. How does this damage explain her symptoms?

4. Effects of damage to the thalamus depend on which portions are injured. Because the thalamus controls the inflow of information to the cerebral cortex, thalamic injury can lead to deficits in perception and awareness of sensory stimuli. Such injury can also affect an individual's ability to initiate voluntary movement. Severe damage to the thalamus will essentially cut off the cerebral cortex from the rest of the nervous system, leading to permanent coma or a persistent vegetative state.

In terms of survival, to which of the four divisions of the brain would an injury be most damaging? Explain.

An injury to the brainstem would be most damaging in terms of survival because the brainstem is responsible for maintaining basic aspects of homeostasis, such as breathing and blood pressure.

Would you expect the fingertips or the back to be represented by a greater area of the primary somatosensory cortex? Explain.

Areas of the body that have a higher density of sensory receptors have a larger proportional area of the primary somatosensory cortex dedicated to them. The fingertips have a higher density of sensory receptors than the back does, so their area of the primary somatosensory cortex is larger than that for the back.

A tear in the meninges may result in the leakage of CSF. Considering the functions of CSF, predict the symptoms you would see with a CSF leak.

CSF makes the brain buoyant, preventing it from crushing itself under its own weight. A decreased amount of CSF will put pressure on the brain, leading to headaches and possible impairment of various sensory and motor functions, depending on the degree of CSF loss.

A potential effect of chronic alcohol abuse is the development of cerebellar damage. Predict the symptoms you would likely see in a person with such a condition.

Cerebellar damage will cause an individual to appear clumsy and uncoordinated, as the cerebellum will be unable to detect motor error and/or unable to send feedback to the primary motor cortex to correct for motor error.

Fill in the blanks: The cell bodies of upper motor neurons reside in the _________ and function to ________, whereas the cell bodies of lower motor neurons reside in the __________ and function to _________.

Cerebral cortex, plan and initiate voluntary movement; anterior horn of the spinal cord, directly innervate skeletal muscles

9. What structure forms cerebrospinal fluid? How does this occur?

Cerebrospinal fluid is formed by the choroid plexuses. The capillaries of the choroid plexuses are fenestrated, and so fluid and electrolytes leak out of them and into the space under ependymal cells, which then secrete the CSF into the brain's ventricles.

Predict the effects of damage to the basal nuclei or the cerebellum.

Damage to the basal nuclei will cause a patient to have difficulty initiating movement. Damage to the cerebellum will cause a patient to have difficulty controlling ongoing movement.

Ms. Marcos undergoes treatment for a seizure disorder that involves removal of the right and left hippocampus. Will this affect her declarative memory, nondeclarative memory, or both? Will this remove her old memories, impair the formation of new memories, or both?

Ms. Marcos will have deficits in the formation of new declarative memories, as immediate and short-term declarative memories are processed by the hippocampus before becoming long-term memories. Existing long-term memories and new and old nondeclarative memories will be largely unaffected by the surgery.

When patients are given a drug that must enter the ECF of the brain, they are sometimes infused with the chemical mannitol. Mannitol temporarily disrupts tight junctions. How would this help deliver the drug?

Normally, the capillaries of the brain are highly impermeable to most large molecules due to the blood brain barrier. Disrupting the tight junctions of the blood-brain barrier with mannitol will increase the permeability of the capillaries and allow more molecules of a drug to exit the blood and enter the ECF.

The patient in question 2, Ms. Marcos, also has her right and left amygdala removed. What effect is this likely to have?

The amygdala is a key player (although not the only one) in the highly subjective feelings that we experience. Thus, Ms. Marcos can expect to have some emotional abnormalities, although the degree to which this will be a problem for her is difficult to predict.

How could you tell the difference between an injury that damaged the cerebellum and one that damaged the basal nuclei?

The basal nuclei are responsible for the initiation of movement, and the cerebellum is responsible for monitoring ongoing movement. An individual with damage to the basal nuclei will have difficulty in initiating a movement. An individual with damage to the cerebellum, however, will have difficulty in continuing a movement in a smooth, fluid, balanced fashion after it has been initiated.

Huntington's disease is characterized by a loss of normal inhibition mediated by the basal nuclei. Predict the symptoms you are likely to see with this disease.

The basal nuclei inhibit abnormal or involuntary movements. In a person with Huntington's disease, you will therefore see involuntary movements and vocalizations due to loss of inhibition.

A person who is in a vegetative state has no activity in his or her cerebrum. Why can a person in this condition continue living for a certain period? Can such a person feel pain or initiate voluntary movements? Explain.

The basic functions that enable life are controlled primarily by the hypothalamus and brainstem. For this reason, such functions can continue even in the absence of cortical activity. However, an individual in a vegetative state does not have any true sensory awareness of pain or other stimuli and lacks the ability to initiate voluntary movement, since that requires upper motor neurons of the motor cortices.

How would degeneration of the globus pallidus differ from degeneration of the caudate nucleus, putamen, and substantia nigra? Explain.

The caudate nucleus, putamen, and substantia nigra are instrumental in initiating movement by inhibiting the globus pallidus. With their degeneration, an individual would have difficulty in initiating movement, as the globus pallidus would inhibit movement continuously.

Why are no dural sinuses present in the spinal cord?

The dural sinuses are located between the periosteal and meningeal layers of the cranial dura. The spinal cord has no periosteal dura; instead, the dura there is composed of a single layer. For this reason, there is no place for a dural sinus in the spinal cord.

Which parts of the body have the greatest amount of space dedicated to them in the primary somatosensory cortex? Why?

The fingertips, lips, and hands have the greatest representation within the primary somatosensory cortex because of the importance of manual dexterity and facial expression to human activities.

Predict the effects of degeneration of the globus pallidus.

The globus pallidus sends inhibitory impulses to the thalamus, blocking the initiation of inappropriate movement. Degeneration of the globus pallidus would remove this inhibition, and the individual would experience inappropriate, involuntary movements.

Why do injuries to the hippocampus interfere with the formation of new declarative memories but do not impact memories already encoded in long-term memory? Why do such injuries not affect the formation of nondeclarative memories?

The hippocampus is involved in the formation of declarative memories, but not their storage (they are stored in the cerebral cortex). Nondeclarative memories are not formed by the hippocampus, but rather by the motor cortices, the cerebellum, and the basal nuclei, so damage to the hippocampus will not affect these memories.

Mr. Jacobs suffers widespread damage to his right cerebral hemisphere. His wife believes he will be fine because his left cerebral hemisphere is undamaged. Is his wife correct? Explain. What deficits, if any, can Mr. Jacobs expect to face?

The lateralization of certain functions means that some functions are performed primarily by the right or left side of the cerebrum. Mr. Jacobs can expect difficulties with attention, facial recognition, "negative" emotions such as anger, and interpretation of the emotional aspects of language. Furthermore, damage to sensory and motor regions of the right hemisphere will impair his ability to sense stimuli from the left or command muscles on the left side of his body.

A person with a spinal cord injury is experiencing loss of pain sensation in his left leg and loss of tactile sensation in his right leg. On which side of the spinal cord is the injury located? Explain.

The pathways of the anterolateral system, which carry pain stimuli from the left side of the body, decussate in the posterior horn and travel up the right side of the spinal cord. The pathways of the right posterior columns, which carry tactile stimuli, travel in the right side of the spinal cord and do not decussate until the brainstem. Therefore, the injury is on the right side of the spinal cord.

Mandy is a 13-year-old patient with suspected bacterial meningitis. A resident performs a lumbar puncture to collect a sample of CSF and sends it to the lab. However, when the lab technician examines the sample, she finds only blood and adipocytes (fat cells), and no CSF. What has likely happened?

The resident has likely not advanced the needle far enough and so has withdrawn material from the epidural space rather than the subarachnoid space. The epidural space contains adipose tissue and some blood vessels but no CSF. The CSF is located in the subarachnoid space.

Ms. Nazari presents to the emergency department with loss of muscle function on the right side of her body. The physician suspects she has suffered a stroke (a blood clot in the brain). On which side of her brain did the stroke likely occur? Explain.

The stroke likely occurred on the left side of Ms. Nazari's brain. Motor pathways initiate in one cerebral hemisphere, and then most of the fibers decussate in the medulla to serve the opposite side of the body. Therefore, damage to the left hemisphere will mostly affect the right side of the body

1. You are about to take your anatomy and physiology exam and you notice that your heart is beating rapidly and your rate of breathing has increased. What parts of the brain are responsible for these changes, and how do they accomplish them?

The structures mainly responsible for these changes are the hypothalamus and the reticular formation. The cerebral cortex also plays a role, as it is the cortical mediation of "nervous" feelings that trigger the hypothalamus to stimulate the reticular formation nuclei.

The term painkiller is used for drugs that bind to receptors for endorphins in the CNS. How do these drugs relieve pain? Do they actually treat the cause of the pain? (Hint: Where do they bind?)

These drugs bind to receptors in the brainstem and spinal cord, and block the transmission and perception of pain stimuli. They do not treat the cause of the pain, so when their effects wear off, the perception of pain will return.

Explain why sleepwalking and sleeptalking can occur only during non-REM sleep.

Under most conditions, muscle groups are paralyzed during REM sleep, which prevents sleeping individuals from acting out their dreams. These muscle groups are not fully paralyzed during non-REM sleep, and thus a sleeper can potentially engage in sleeptalking or sleepwalking.

16. Label the following components of the corticospinal tracts with numbers 1 through 6, with 1 being the origin of the tracts and 6 their destination. _____Medullary pyramids where most fibers decussate _____Anterior horn of the spinal gray matter _____Midbrain and pons _____Upper motor neurons in the primary motor and premotor cortices _____Corona radiata and internal capsule _____Lateral funiculus of the spinal cord

___4__Medullary pyramids where most fibers decussate ___6__Anterior horn of the spinal gray matter ___3__Midbrain and pons ___1__Upper motor neurons in the primary motor and premotor cortices ___2__Corona radiata and internal capsule ___5__Lateral funiculus of the spinal cord

Match the term on the left with its correct description from the column on the right. _____REM sleep _____Stage I sleep _____Delta waves _____Beta waves _____Theta waves _____Stage IV sleep a. The EEG pattern seen in the deepest stage of sleep b. The deepest stage of sleep c. The EEG pattern seen in an alert, awake adult d. Drowsiness or the lightest stage of sleep e. The EEG pattern seen in lighter stages of sleep f. The stage of sleep during which most dreaming takes place

___f__REM sleep ___d__Stage I sleep ___a__Delta waves ___c__Beta waves ___e__Theta waves ___b__Stage IV sleep

Match the following terms with the correct definition/ description: ____Insula ____Occipital lobe ____Cerebral cortex ____Cerebral white matter ____Parietal lobe ____Basal nuclei a. Outer few millimeters of gray matter of the cerebral hemispheres b. Cerebral lobe deep to the frontal, parietal, and temporal lobes c. Clusters of gray matter within the cerebrum that control movement d. Posterior cerebral lobe e. Groups of myelinated axons that connect regions of the cerebrum and other parts of the brain f. Middle and superior cerebral lobe

__b__Insula __d__Occipital lobe __a__Cerebral cortex __e__Cerebral white matter __f__Parietal lobe __c__Basal nuclei

Match the term on the left with its correct description in the column on the right. _____Amygdala _____Thalamus _____Hippocampus _____Midbrain _____Medulla oblongata _____Hypothalamus _____Cerebellum _____Pons a. Serves as the main "entryway" into the cerebral cortex b. Contains the pyramids where the corticospinal tracts decussate c. Portion of the limbic system involved in emotion d. Regulates homeostasis, the autonomic nervous system, the endocrine system, and the sleep/wake cycle e. Consists of three lobes and coordinates movement f. Portion of the limbic system; involved in memory g. Middle portion of brainstem; plays a role in movement, sleep, and arousal h. First component of the brainstem; participates in reflexes, sensation, and movement

__c__Amygdala __a___Thalamus __f___Hippocampus __h___Midbrain __b___Medulla oblongata __d___Hypothalamus __e___Cerebellum __g___Pons

Mark the following statements about the brain as true or false. If a statement is false, correct it to make a true statement. a. Humans use only 10% of their brains. b. The four main components of the brain are the cerebrum, the diencephalon, the cerebellum, and the brainstem. c. The right and left lateral ventricles are the largest of the ventricles in the brain and are located in the diencephalon. d. The cerebrum is responsible for our basic, involuntary functions and reflexes.

a. False - Humans use only 100% of their brains. b. True - The four main components of the brain are the cerebrum, the diencephalon, the cerebellum, and the brainstem. c. False - The right and left lateral ventricles are the largest of the ventricles in the brain and are located in the cerebrum. d. False - The brainstem is responsible for our basic, involuntary functions and reflexes.

11. Mark the following statements about the spinal cord as true or false. If a statement is false, correct it to make a true statement. a. The spinal cord functions as a relay and processing station. b. The spinal cord extends from the foramen magnum to the level between the first and second lumbar vertebrae. c. The epidural space around the spinal cord is only a potential space. d. The posterior horn of spinal gray matter contains the cell bodies of motor neurons. e. The corticospinal tracts are the main sensory tracts in the spinal cord.

a. The spinal cord functions as a relay and processing station. b. The spinal cord extends from the foramen magnum to the level between the first and second lumbar vertebrae. c. The epidural space around the spinal cord is only a potential space. d. The posterior horn of spinal gray matter contains the cell bodies of motor neurons. e. The corticospinal tracts are the main sensory tracts in the spinal cord.

Which statement about the cranial meninges is true? a. The subdural space is between the dura and the arachnoid mater. b. The arachnoid mater closely follows the contours of the cerebral gyri and sulci. c. The pia mater is the tough outer meninx. d. The subarachnoid space is between the dura and the arachnoid mater.

a. The subdural space is between the dura and the arachnoid mater.

20. Which of the following statements is false? a. The suprachiasmatic nucleus is often called the body's "master clock." b. Melatonin and the ventrolateral preoptic nucleus increase the activity of the reticular formation. c. A decrease in the activity of the reticular formation disconnects the thalamus from the cerebral cortex and decreases the level of consciousness. d. Orexins are neurotransmitters that stimulate the reticular formation.

b. Melatonin and the ventrolateral preoptic nucleus increase the activity of the reticular formation.

17. Mark the following statements on the role of the brain in movement as true or false. If a statement is false, correct it to make a true statement. a. The dopaminergic neurons of the substantia nigra enhance the actions of the caudate nucleus and putamen. b. The cerebellum monitors the initiation of movement but does not monitor ongoing movements. c. The basal nuclei inhibit inappropriate movements and are required for the initiation of movement. d. The correction of motor error by the cerebellum can occur over the long term by motor learning.

a. True - The dopaminergic neurons of the substantia nigra enhance the actions of the caudate nucleus and putamen. b. False - The cerebellum does not monitor the initiation of movement but does monitor ongoing movements. c. True - The basal nuclei inhibit inappropriate movements and are required for the initiation of movement. d. True - The correction of motor error by the cerebellum can occur over the long term by motor learning.

Mark the following statements about the cerebral cortex as true or false. If a statement is false, correct it to make a true statement. a. The neocortex is the "newest" component of the cerebral cortex from an evolutionary perspective. b. The cerebral cortex is composed of white matter. c. The primary visual cortex is located in the occipital lobe. d. The prefrontal cortex is located in the frontal lobe and is concerned with movement.

a. True - The neocortex is the "newest" component of the cerebral cortex from an evolutionary perspective. b. False - The cerebral cortex is composed of gray matter. c. True - The primary visual cortex is located in the occipital lobe. d. False - The prefrontal cortex is located in the frontal lobe and is concerned with behavior, personality, learning, and memory.

The central nervous system is responsible for: a. integrative functions. b. sensory functions. c. motor functions. d. Both b and c are correct.

a. integrative functions.

Which statement about cerebral white matter is false? a. Commissural fibers connect the right and left cerebral hemispheres. b. Projection fibers connect the cerebral cortex of one hemisphere with structures in the other hemisphere. c. The corpus callosum is the largest bundle of white matter in the brain. d. Association fibers connect the gyri of the cerebral cortex with one another.

b. Projection fibers connect the cerebral cortex of one hemisphere with structures in the other hemisphere.

Which of the following somatic sensations is not carried by the posterior columns? a. Tactile senses b. Temperature c. Proprioception d. Stretch

b. Temperature

Which of the following is not one of the basal nuclei? a. Caudate nucleus b. Globus pallidus c. Cerebellum d. Putamen

c. Cerebellum

Which of the following is not a component of emotion? a. Visceral motor responses mediated by the hypothalamus b. Somatic motor responses mediated by the limbic system and the hypothalamus c. Somatic motor responses mediated by the upper motor neurons of the corticospinal tracts d. Subjective feelings mediated by the amygdala and the cerebral cortex

c. Somatic motor responses mediated by the upper motor neurons of the corticospinal tracts

The part of the brain responsible for the production of language is known as: a. Wernicke's area. b. the prefrontal cortex. c. the auditory association area. d. Broca's area.

d. Broca's area.

Which of the following statements is false? a. The spinothalamic tracts are part of the anterolateral system. b. Pain, temperature, and crude touch stimuli are carried by the anterolateral system. c. Descending pathways from the brain and spinal cord can make the spinal cord less receptive to pain stimuli. d. The thalamus serves as the "gateway" for entry of all special sensory stimuli into the cerebral cortex, with the exception of audition (hearing).

d. The thalamus serves as the "gateway" for entry of all special sensory stimuli into the cerebral cortex, with the exception of audition (hearing).

6. The central sulcus separates the: a. parietal and temporal lobes. b. parietal and occipital lobes. c. frontal and temporal lobes. d. frontal and parietal lobes.

d. frontal and parietal lobes.

Fill in the blanks: Declarative memories are formed by the process of __________ that takes place in the ___________, and are stored in the ___________.

long-term potentiation, hippocampus, cerebral cortex