Chapter Summary

Internal Affairs (104.0K)

1. The central nervous system (CNS) consists of the brain and spinal cord and contains gray and white matter. It is covered with meninges and bathed in cerebrospinal fluid.
2. The functions of the nervous system include orientation, coordination, assimilation, and programming of instinctual behavior.

1. Neurons are the basic structural and functional units of the nervous system. Specialized cells called neuroglia provide structural and functional support for the activities of neurons.
2. A neuron contains dendrites, a cell body, and an axon.
1. The cell body contains the nucleus, chromatophilic substances, neurofibrils, and other organelles.
2. Dendrites receive stimuli and the axon conducts nerve impulses away from the cell body.
3. Neuroglia are of six types: neurolemmocytes form myelin layers around axons in the PNS; oligodendrocytes form myelin layers around axons in the CNS; microglia perform a phagocytic function in the CNS; astrocytes regulate passage of substances from the blood to the CNS; ependymal cells assist the movement of cerebrospinal fluid in the CNS; and ganglionic gliocytes support neuron cell bodies in the PNS.
1. The neuroglia that surround an axon form a covering called a myelin layer.
2. Myelinated neurons have limited capabilities for regeneration following trauma.
4. A nerve is a collection of dendrites and axons in the PNS.
1. Sensory (afferent) neurons are pseudounipolar.
2. Motor (efferent) neurons are multipolar.
3. Association (interneurons) are located entirely within the CNS.
4. Somatic motor nerves innervate skeletal muscle; visceral motor (autonomic) nerves innervate smooth muscle, cardiac muscle, and glands.

1. Irritability and conductivity are properties of neurons that permit nerve impulse transmission.
2. Neurotransmitters facilitate synaptic impulse transmission.

1. The brain, composed of gray matter and white matter, is protected by meninges and is bathed in cerebrospinal fluid.
2. About 750 ml of blood flows to the brain each minute.

1. The cerebrum, consisting of two convoluted hemispheres, is concerned with higher brain functions, such as the perception of sensory impulses, the instigation of voluntary movement, the storage of memory, thought processes, and reasoning ability.
2. The cerebral cortex is convoluted with gyri and sulci.
3. Each cerebral hemisphere contains frontal, parietal, temporal, and occipital lobes. The insula lies deep within the cerebrum and cannot be seen in an external view.
4. Brain waves generated by the cerebral cortex are recorded as an electroencephalogram and may provide valuable diagnostic information.
5. The white matter of the cerebrum consists of association, commissural, and projection fibers.
6. Basal nuclei are specialized masses of gray matter located within the white matter of the cerebrum.

1. The diencephalon is a major autonomic region of the brain.
2. The thalamus is an ovoid mass of gray matter that functions as a relay center for sensory impulses and responds to pain.
3. The hypothalamus is an aggregation of specialized nuclei that regulate many visceral activities. It also performs emotional and instinctual functions.
4. The epithalamus contains the pineal gland and the vascular choroid plexus over the roof of the third ventricle.

1. The mesencephalon contains the corpora quadrigemina, the cerebral peduncles, and specialized nuclei that help to control posture and movement.
2. The superior colliculi of the corpora quadrigemina are concerned with visual reflexes and the inferior colliculi are concerned with auditory reflexes.
3. The red nucleus and the substantia nigra are concerned with motor activities.

1. The pons consists of fiber tracts connecting the cerebellum and medulla oblongata to other structures of the brain. The pons also contains nuclei for certain cranial nerves and the regulation of respiration.
2. The cerebellum consists of two hemispheres connected by the vermis and supported by three paired cerebellar peduncles.
1. The cerebellum is composed of a white matter tract called the arbor vitae, surrounded by a thin convoluted cortex of gray matter.
2. The cerebellum is concerned with coordinated contractions of skeletal muscle.

1. The medulla oblongata is composed of the ascending and descending tracts of the spinal cord and contains nuclei for several autonomic functions.
2. The reticular formation functions as the reticular activating system in arousing the cerebrum.

1. The cranial dura mater consists of an outer periosteal layer and an inner meningeal layer. The spinal dura mater is a single layer surrounded by the vascular epidural space.
2. The arachnoid is a netlike meninx surrounding the subarachnoid space, which contains cerebrospinal fluid.
3. The thin pia mater adheres to the contours of the CNS.

1. The lateral (first and second), third, and fourth ventricles are interconnected chambers within the brain that are continuous with the central canal of the spinal cord.
2. These chambers are filled with cerebrospinal fluid, which also flows throughout the subarachnoid space.
3. Cerebrospinal fluid is continuously formed by the choroid plexuses from blood plasma and is returned to the blood at the arachnoid villi.
4. The blood-brain barrier determines which substances within blood plasma can enter the extracellular fluid of the brain.

1. The spinal cord is composed of 31 segments, each of which gives rise to a pair of spinal nerves.
1. It is characterized by a cervical enlargement, a lumbar enlargement, and two longitudinal grooves that partially divide it into right and left halves.
2. The conus medullaris is the terminal portion of the spinal cord, and the cauda equina are nerve roots that radiate interiorly from that point.
2. Ascending and descending spinal cord tracts are referred to as funiculi.
1. Descending tracts are grouped as either corticospinal (pyramidal) or extrapyramidal.
2. Many of the fibers in the funiculi decussate (cross over) in the spinal cord or in the medulla oblongata of the brain stem.