Chapter 12 Central Nervous

The cerebral cortex is the "executive suite" of the nervous system, where our conscious mind is found. It enables us to be aware of ourselves and our sensations, to communicate, remember, understand, and initiate voluntary movements.

cerebral and diencephalic structures The limbic system, which mediates emotional response and plays a role in memory, is a group of structures located on the medial aspect of each cerebral hemisphere and diencephalon. The cerebral structures include the amygdaloid body, cingulate gyrus, septal nuclei, hippocampus, dentate gyrus, and parahippocampal gyrus. The diencephalic structures include the mammillary body, hypothalamus, and anterior thalamic nuclei. The fiber tracts that link these limbic system regions together include the fornix and anterior commissure.

White matter consists largely of myelinated fibers bundled into large tracts. These fibers and tracts are classified according to the direction in which they run as association, commissural, or projection. Commissural fibers connect corresponding gray areas of the two cerebral hemispheres, allowing them to function as a coordinated whole. The largest commissure is the corpus callosum. Less prominent examples include the anterior and posterior commissures.

Afferent impulses from all senses and all parts of the body converge on the thalamus and synapse with at least one of its nuclei. The thalamus - which sorts out and "edits" these afferent signals before relaying them to the appropriate cortical areas - is considered the gateway to the cerebral cortex. In summary, the thalamus plays a key role in mediating sensation, motor activities, cortical arousal, learning, and memory.

The hypothalamus is the main visceral control center of the body and is vitally important to overall body homeostasis. Its chief homeostatic roles include: controlling the autonomic nervous system; controlling endocrine system function; regulating the sleep-wake cycle, body temperature, hunger and thirst; and initiating physical responses to emotions.

The medulla contains many important functional groups of visceral motor nuclei, including the cardiovascular (CV) and respiratory centers. The CV center includes the cardiac center, which adjusts the force and rate of heart contraction to meet the body's needs, and the vasomotor center, which changes blood vessel diameter to regulate blood pressure. The respiratory centers generate the respiratory rhythm and (in concert with pontine centers) control the rate and depth of breathing. The olivary nuclei and cough, sneezing, swallowing, and vomiting centers are also in the medulla.

By processing and interpreting impulses from the motor cortex and brain stem nuclei, as well as sensory pathways, the cerebellum provides the precise timing and appropriate patterns of skeletal muscle contraction for the smooth, coordinated movements and agility needed for daily living (e.g., driving, typing, and tying our shoes). It also plays a poorly understood role in cognition. Cerebellar activity occurs subconsciously (we are not aware of it).

The subarachnoid space is filled with CSF. Knoblike projections of the arachnoid mater, called arachnoid villi, protrude superiorly through the dura mater and into the superior sagittal sinus. These villi provide a passageway for CSF to leave the subarachnoid space and enter the venous blood of the sinus.

Memory is a function of the brain (not the spinal cord).

The collection of nerve roots at the inferior end of the vertebral canal is named the cauda (tail) equina (horse) because it resembles a horse's tail. This strange arrangement reflects the fact that during fetal development, the vertebral column grows faster than the spinal cord, forcing the lower spinal nerve roots to "chase" their exit points inferiorly through the vertebral canal.

The term mesencephalon means "midbrain." As it develops from a primary brain vesicle to a secondary brain vesicle, and finally an adult brain structure, it retains its name - the midbrain. Each of the other two primary brain vesicles divide to give rise to new secondary brain vesicles and adult brain structures (with new names). Note that encephalo- means "brain."

The cerebral hemispheres, which form the superior part of the brain, account for about 83% of total brain mass.

The cerebral cortex contains three types of functional areas: motor areas, sensory areas, and association areas. The visuals areas are examples of sensory and association areas. The visual association area surrounds the primary visual cortex and covers much of the occipital lobe. Communicating with the primary visual cortex, the visual association area uses past visual experiences to interpret visual stimuli (color, form, and movement), enabling us to recognize a flower or a person's face and to appreciate what we are seeing.

The following motor areas of the cortex, which control voluntary movement, lie in the posterior part of the frontal lobes: primary motor cortex, premotor cortex, Broca's area, and the frontal eye field. The frontal eye field (which controls voluntary movement of the eyes) is located partially in and anterior to the premotor cortex (which helps plan movements) and superior to Broca's area (a motor speech area that also becomes active as we prepare to speak and even as we think about (plan) many voluntary motor activities other than speech).

primary somatosensory cortex. Neurons in the primary somatosensory cortex receive information from the general (somatic) sensory receptors in the skin and from proprioceptors (position sense receptors) in skeletal muscles, joints, and tendons. The neurons then identify the body region being stimulated, an ability called spatial discrimination. The vestibular (equilibrium) cortex is responsible for conscious awareness of balance (the position of the head in space), not spatial discrimination. It is located in the posterior part of the insula and the adjacent parietal cortex.

The frontal eye field controls voluntary movement of the eyes; it is located partially in and anterior to the premotor cortex.

Secretion of the hormone melatonin is a function of the pineal gland (not the hypothalamus). The hypothalamus is the main visceral control center of the body and is vitally important to overall body homeostasis. Its chief homeostatic roles include: control the autonomic nervous system; control endocrine system function; regulate the sleep-wake cycle, body temperature, hunger, and thirst; and initiate physical responses to emotions.

By processing and interpreting impulses from the motor cortex and brain stem nuclei, as well as the sensory pathways, the cerebellum provides the precise timing and appropriate patterns of skeletal muscle contraction for the smooth, coordinated movements and agility needed for daily activities (e.g., driving, typing, and tying our shoes). It also plays a poorly understood role in cognition. Cerebellar activity occurs subconsciously (we are not aware of it).

True; In general, information flows from sensory receptors to the appropriate primary sensory cortex, then to a sensory association cortex and then on to the multimodal association cortex. The multimodal association cortex allows us to give meaning to the information that we receive, store it in memory, tie it to previous experience and knowledge, and then decide what action to take.

One cerebral hemisphere or the other "dominates" each of the brain's tasks, and the term cerebral dominance designates the hemisphere that is dominant for language. In most people (about 90%), the left hemisphere has greater control over language abilities, math, and logic.

Afferent impulses from all senses and all parts of the body converge on the thalamus (not the hypothalamus) and synapse with at least one of its nuclei. The thalamus - which sorts out and "edits" these afferent signals before relaying them to the appropriate cortical areas - is considered to be the gateway to the cerebral cortex.

D. based on the doctor's observations, none of the listed answers are correct conclusions; Review central nervous system control of voluntary skeletal muscle contractions and compare it to reflex arc activation.

None of the listed responses is correct. Review the different sensory cortices of the parietal and temporal lobes of the brain.

The frontal lobe has areas that control voluntary motor functions, mood, smell, and social judgment.

suprachiasmatic nucleus: This area of the hypothalamus is important in determining the circadian rhythm that sets our sleep-wake cycles.

People with narcolepsy lapse abruptly into REM sleep from the awake state. These sleep episodes last about 15 minutes, can occur without warning, and are often triggered by a pleasurable event such as a good joke or a game of poker.

Patients with lesions involving Broca's area can understand language but have difficulty speaking (and sometimes cannot write or type or use sign language) - this disorder is called expressive, or Broca's, aphasia. On the other hand, patients with lesions involving Wernicke's area are able to speak but produce a type of nonsense often referred to as "word salad" - this disorder is called receptive, or Wernicke's, aphasia. These patients also have great difficulty understanding language.

True. Many factors can influence the transfer of information from STM to LTM, including: emotional state (we learn best when we are alert, motivated, surprised, and aroused), rehearsal (repeating the material enhances memory), association (tying "new" information to "old" information already stored in LTM appears to be important in remembering facts), and automatic memory (some impressions that become part of LTM are subconsciously formed).

thalamus. This area of the diencephalon groups and organizes afferent sensory impulses. Once grouped, the sensory input is relayed to the correct cerebral area for interpretation.

C. continuously reduced mitochondrial activity in brain neurons; Mitochondria are cytoplasmic organelles that produce ATP that provide energy for other cellular activities. Oxygen consumption during sleep resembles that of the waking state. In coma patients, in contrast, oxygen use is always below resting levels.

Gastrointestinal activity is activated by the sight or smell of food. Additionally, presence of a food bolus in the gastrointestinal tract will stimulate peristalsis and digestive enzyme release.

B. LTM (long term memory) is not disrupted. People with this type of amnesia often cannot remember what they ate for their last meal or events from the immediate past.

The pia mater, meaning "gentle mother," is composed of delicate connective tissue and is richly invested with tiny blood vessels. It is the only meninx that clings tightly to the brain, like cellophane wrap, following its every convolution.

Cerebrospinal fluid (CSF), found in and around the brain and spinal cord, forms a liquid cushion that gives buoyancy to CNS structures. By floating the jellylike brain, the CSF effectively reduces brain weight by 97% and prevents the delicate brain from crushing under its own weight. CSF also protects the brain and spinal cord from blows and other trauma. Additionally, although the brain has a rich blood supply, CSF helps to nourish the brain, and there is some evidence that it carries chemical signals (such as hormones and sleep- and appetite-inducing molecules) from one part of the brain to another.

The pia mater is meningeal layer closest to the brain.

Parkinson's disease results from a degeneration of the dopamine-releasing neurons of the substantia nigra (of the midbrain). As those neurons deteriorate, the dopamine-deprived basal nuclei they target become overactive. Afflicted individuals have a persistent tremor at rest, a forward-bent walking posture and shuffling gait, and a stiff facial expression. They are slow initiating and executing movement.

Alzheimer's disease is a degenerative brain disease in which beta-amyloid peptide deposits and neurofibrillary tangles appear. Marked by a deficit of ACh, it results in slow, progressive loss of memory and motor control and increasing dementia. Alzheimer's patients represent nearly half of the people living in nursing homes. Between 5 and 15% of people over 65 develop this condition, and for up to half of those over 85 it is a major contributing cause in their deaths.

First-order neurons, whose cell bodies reside in a ganglion (dorsal root or cranial), conduct impulses from the cutaneous receptors of the skin and from proprioceptors to the spinal cord or brain stem, where they synapse with second-order neurons.

In anencephaly ("without brain"), the cerebrum and part of the brain stem never develop because the neural folds fail to fuse rostrally. The infant is totally vegetative, unable to see, hear, or process sensory inputs. Muscles are flaccid, and no voluntary movement is possible. Mental life as we know it does not exist. Mercifully, death occurs soon after birth. Spina bifida ("forked spine") results from incomplete formation of the vertebral arches and typically involves the lumbosacral region. The technical definition is that laminae and spinous processes are missing on at least one vertebra. If the condition is severe, neural deficits occur as well.

True

prefrontal cortex

loss of proprioception

True

gyri

False

initiating protective reflex actions

True

the dorsal root ganglia of the spinal cord

longitudinal fissure

pyramidal and corticospinal

metabolic waste such as urea

is considered a motor speech area

premotor cortex

True

initiation of some nerve impulses

midbrain, medulla, and pons

red blood cells

temporary skeletal muscle inhibition except for ocular muscles and diaphragm

temporal lobe

visual association area

medulla

Association

fiber tracts

True

sulcus

True

C. The hemispheres are exactly equal in function.

True

indicated by the arrows

True

arachnoid and pia

True

Parkinson's disease

cerebellar white matter

ependymal cells