1. Brain size is proportional to body size only and can be divided into three major portions; the cerebrum, cerebellum, and brainstem.

2. The cerebrum consists of 2 cerebral hemispheres, each marked by gyri and sulci, with a few fissures. The longitudinal fissure separates left from right, although they remain connected through the corpus callosum. The cerebrum constitutes 83% of brain volume.

3. The cerebellum also has surface markings, but these are more delicate. The cerebrum lies inferior and posterior to the cerebrum.

4. The brainstem is at the base of the brain, and includes the thalamus, hypothlamus, midbrain, pons, and medulla oblongata.

5. Two major types of tissue in the CNS are the gray matter (consisting of nonmyelinated soma and dendrites) and white matter (myelinated nerve fibers). The gray matter forms an outer cortex in the brain, but an inner core in the spinal cord.

6. Much of the CNS is hollow, filled with cerebrospinal fluid.

1. The nervous system forms from ectoderm. By the third week, the neuroectoderm appears along the embryo, and forms a neural plate.

2. The neural plate sinks into a neural groove, while cells along its margin form a neural fold, which eventually fuses.

3. By 4 weeks, a neural tube is evident, the lumen of which forms the ventricles of the brain and the central canal of the spinal cord.

4. Some cells separate from the neural tube and form the neural crest, which gives rise to some sensory neurons and other cell types (neuroglia and neurons).

5. At week 4, the neural tube shows three primary vesicles, a forebrain, midbrain, and hindbrain; the forebrain then divides further into the telencephalon and diencephalon. The hindbrain divides into the metencephalon and myelencephalon.

1. The meninges are three protective fibrous coverings that separate the brain and spinal cord from the skull and vertebrae.

2. The outermost meninx, the dura mater, consists of an outer periosteal layer and an inner meningeal layer. In certain places, these two layers are separated by dural sinuses where blood pools. In other places, the dura mater folds to separate major areas of the brain. These folds are the flax cerebri and tentorium cerebelli. The dura also forms a covering over the sella turcica, called the diaphragma sellae.

3. Within the vertebral canal, the periosteal layer of the dura is absent. The meningeal layer forms a dural sheath. Between the sheath and surrounding bone lies the epidural space.

4. The second meninx, the arachnoid matter adheres to the dura and sends spiderlike extensions out to the pia mater.

5. The pia mater is highly vascular layer that closely follows the contours of the brain.

6. The dura and arachnoid are separated by a subdural space; the arachnoid and pia mater are separated by the subarachnoid space.

1. Cerebrospinal fluid (CSF) is a clear, colorless liquid that functions to lend buoyancy, for protection, in waste removal, and in providing a stable chemical environment.

2. Cerebrospinal fluid is produced by the choroid plexus within each ventricle, which consists of capillaries covered by simple cuboidal epithelium.

3. Tight junctions within the choroid plexus form a blood-CSF barrier that protects the brain.

1. The brain has four CSF-filled ventricles. Each cerebral hemisphere houses a large lateral ventricle that communicates with a third ventricle through an interventricular foramen. The cerebral aqueduct connects the third with the fourth ventricle.

2. Cerebrospinal fluid originates in the choroid plexuses of each ventricle, circulates throughout the ventricles, and makes its way into the central canal of the spinal cord. It exits the fourth ventricles through two apertures and enters the subarachnoid space.

3. Hydrocephalus results from blockage of the route of CSF and its absorption.

1. The brain is very metabolically active, and has a high demand for oxygen and glucose. Stopping the blood supply to the brain for as little as 4 minutes can cause irreversible brain damage.

2. The CNS is protected by a blood-brain barrier that regulates substances entering the brain. Tight junctions within capillaries and astrocytes comprise this barrier.

3. The blood-brain barrier is absent in areas of the brain (called circumventricular organs) that monitor blood glucose, pH, salinity, and so forth.

1. The spinal cord functions in conduction, locomotion, and control of reflex activity.

1. The spinal cord begins at the foramen magnum and ends at the first lumbar vertebra. It is divided into cervical, thoracic, lumbar, and sacral regions.

2. The spinal cord gives rise to 31 pairs of spinal nerves, each of which is connected to a segment of the spinal cord.

3. The spinal cord bears a cervical and lumbar enlargement, where nerves leading to appendages arise. The cord tapers to a point at the conus medullaris. A nerve bundle, the cauda equina, exits the bottom of the spinal cord.

1. The spinal cord has an anterior median fissure and a posterior median sulcus.

2. Gray Matter (p. 473)

3. White Matter (p. 474)

1. Ascending tracts carry sensory information up the spinal cord; descending tracts carry motor information down it. Many of the fibers exhibit decussation.

2. Ascending Tracts (p. 474; Figs. 14.10, 14.11; Transps. 251, 252; Table 14.1)

3. Descending Tracts (p. 475; Fig. 14.12; Transp. 253)

1. The myencephalon develops into the medulla oblongata. Features of the medulla include the pyramids, and olives containing inferior olivary nuclei (relay centers to cerebellum).

2. Nuclei of the medulla oblongata control coughing, sneezing, hiccuping, sweating, vomiting, and other functions. In addition, the cardiac, vasomotor, and respiratory centers are located there.

1. The pons and cerebellum arise from the metencephalon.

2. The gray matter of the pons contains nuclei concerned with sleep, posture, respiration, swallowing, and bladder control. Signals from the cerebrum to the cerebellum pass through the pons.

3. The cerebellum is the largest part of the hindbrain. It consists of right and left cerebellar hemispheres connected by a vermis. Three paired cerebellar peduncles connect the cerebellum to the brainstem.

4. The cerebellum modulates and coordinates voluntary movement of the limbs, maintains muscle tone and posture, coordinated eye movements, and helps in learning motor skills.

1. The mesencephalon connects the hindbrain to the forebrain. It contains cerebral peduncles, the substantia nigra, and tegmentum with the red nucleus.

2. Another portion of the midbrain, the tectum, consists of 4 nuclei called the corpora quadrigemina. These nuclei function in visual attention, tracking objects, and visual reflexes.

1. The reticular formation is a group of 100 nuclei scattered throughout the medulla, midbrain, and pons that function in somatic motor control, autonomic control, arousal, and pain modulation.

1. The thalamus makes up four-fifths of the diencephalon. The thalamus consists of two oval masses of gray matter, underneath each cerebral hemisphere, and a narrow intermediate mass near the third ventricle.

2. The thalamus is the "gateway to the cerebral cortex"; nearly all information heading to the cerebrum passes through the thalamus, except for sensory input from smell.

1. The hypothalamus forms portions of the walls of the third ventricle.

2. The hypothalamus is the major control center of the autonomic nervous system and the endocrine system, plus plays a role in homeostasis.

3. The nuclei of the hypothalamus regulate food and water intake, thermoregulation, cardiovascular regulation, sleep and waking, and emotional behavior.

1. The epithalamus consists of the pineal gland, the habenula, and a roof over the third ventricle.

1. The white matter of the cerebrum does not make decisions, but makes up most of the volume of the cerebrum.

2. This area houses projection tracts, commissural tracts, and association tracts.

1. The telenecphalon contains three areas of integration - the cortex, basal nuclei, and limbic system.

2. The cerebral cortex (40% of brain mass) is a layer of gray matter, 2-3 mm thick, covering the cerebral hemispheres.

3. The cerebral cortex is divided into the following lobes: frontal, parietal, occipital, and temporal.

1. Two types of neurons are found in the cortex: stellate cells and pyramidal cells.

2. Stellate cells have spheroidal somas with dendrites extending in all directions. They receive sensory input and project it locally.

3. Pyramidal cells are tall and conical, with a thick dendrite bearing many branches. These serve as the output neurons of the cerebrum.

4. Ninety percent of the cortex is called neocortex, evolutionarily speaking. It consists of 6 layers. There are older areas of the brain. The paleocortex has one to five layers and is concerned with the olfactory sense. The limbic system is made up of a three-layered archicortex.

1. The basal nuclei are masses of gray matter buried deep in the cerebral hemispheres. These are the caudate nucleus, putamen, globus pallidus, amygdala, and claustrum.

2. The basal nuclei are involved in motor control and the thought process.

1. The limbic system is a loop of cortical structures surrounding the corpus callosum and thalamus. It is the oldest part of the cerebral cortex.

2. Many important facets of an individual's personality depend on an intact limbic system.

3. The limbic system is important for emotions, such as fear, anger, love, and others.

1. Brain waves are rhythmic voltage changes resulting from synchronized postsynaptic potentials in the cerebral cortex. They can be recorded as an electroencephalogram (EEG). An EEG is often used as a legal criterion for death.

2. Brain waves are classified as alpha, beta, theta, and delta waves.

3. Alpha waves are seen when the subject is awake, but eyes are closed, they are resting, and the mind is wandering.

4. Beta waves are seen during mental activity and sensory perception.

5. Theta waves are normal in children and sleeping adults, but signal brain disorders and emotional stress in awake adults.

6. Delta waves are present in awake infants and in deeply sleeping adults. If present in awake adults, they indicate brain damage.

1. Sleep is a temporary state of unconsciousness from which the person can be aroused, whereas a coma is a state of unconsciousness from which the person cannot be aroused.

2. The biological clock that regulates sleep-wake cycles is the suprachiasmatic nucleus of the hypothalamus. The hypothalamus and brain stem control sleep.

3. We pass through four stages of brain activity after falling asleep.

4. Stage 1 sleep occurs after first falling asleep; alpha waves are dominant, and the person is easily aroused.

5. Stage 2 sleep is characterized by sleep spindles and an irregular EEG.

6. During stage 3, sleep deepens, vital signs decline, and theta waves appear.

7. Stage 4 (slow-wave sleep) is dominated by delta waves. The person is deeply asleep.

8. Several times per night, the sleeper "backtracks" to stage 1 and enters rapid eye movement (REM) sleep. It is also called paradoxical sleep because of the difficulty with which a sleeper can be aroused. Most dreams occur during this period. As sleep continues, periods of REM sleep get longer.

1. Voluntary muscle contractions are initiated in the motor association (premotor) area of the frontal lobes. The impulse is then sent to the precentral gyrus (primary motor area), which exhibits a somatotopy.

1. The postcentral gyrus functions as the primary sensory area or somesthetic. Here neurons receive sensory information. This gyrus also exhibits somatotopy.

1. Input from the special senses does not enter the postcentral gyrus but instead travels to other specialized areas of the brain (See p. 493; Fig. 14.28; Transp. 266).

1. Various association areas are located in the cerebral cortex (Fig. 14.28; Transp. 266), including the somatosensory association area, the visual association area, the auditory association area, and the frontal association area.

1. Cerebral lateralization is the assignment of different tasks to different hemispheres, and is correlated with handedness. Most Americans are right-handed, and most have the left hemisphere as the categorical one. Males show more lateralization than females.

1. Language includes several abilities and is assigned to different regions of the cerebral cortex. Areas involved are Wernicke's area, the angular gyrus, Broca's area, and the affective language area.

1. Memory is the storage and retrieval of acquired information or skills. Memory is established in phases.

2. Short-term memory lasts up to a few hours and is limited to 7-12 bits of information.

3. Long-term memory last longer, and can store an unlimited amount of information. Memory consolidation means the memory is more likely to persist. Two types of long-term memory exist.

4. Declarative memory is long-term memory in which facts and numbers are stored. The hippocampus is involved here.

5. Procedural memory is long-term memory involving conditioned reflexes.