Chapter 13
Posterior horn
contain interneurons as well as axons of incoming sensory neurons.
Cerebrovascular accident
Destruction of brain tissue (infarction) resulting from obstruction or rupture of blood vessels that supply the brain. Also called a stroke or brain attack.
contusion
Permanent brain damage
arachnoid mater
The middle of the three meninges (coverings) of the brain and spinal cord.
Spinal nerve
the paths of communication between the spinal cord and specific regions of the body
Cerebellum
The part of the brain lying posterior to the medulla oblongata and pons; governs balance and coordinates skilled movements.
composition and general function of tracts
Bundles of myelinated axons that propagate impulses throughout the CNS to allow communication between its regions. Tracts are the CNS equivalent of nerves.
Association tracts
Contain axons that conduct impulses between gyri in the same hemisphere.
encephalitis
An acute inflammation of the brain caused by either a direct attack by any of several viruses or an allergic reaction to any of the many viruses that are normally harmless to the central nervous system.
Meningitis
An acute inflammation of the meninges, usually caused by a viral or bacterial infection.
Alzheimer disease
Disabling neurological disorder characterized by dysfunction and death of specific cerebral neurons, resulting in widespread intellectual impairment, personality changes, and fluctuations in alertness.
Cerebrum
It provides us with the ability to read, write, and speak; to make calculations and compose music; and to remember the past, plan for the future, and imagine things that have never existed before. The cerebrum consists of an outer cerebral cortex, an internal region of cerebral white matter, and nuclei, functional clusters of neuronal cell bodies deep within the white matter.
Somatosensory association area
Just posterior to and receives input from the primary somatosensory area, as well as from the thalamus and other parts of the brain. It integrates and interprets sensations. This area permits you to determine the exact shape and texture of an object by feeling it, to determine the orientation of one object with respect to another as they are felt, and to sense the relationship of one body part to another. Another role of the somatosensory association area is the storage of memories of past somatic sensory experiences, enabling you to compare current sensations with previous experiences.
Primary visual area
Located at the posterior tip of the occipital lobe, mainly on the medial surface (next to the longitudinal fissure). It receives visual information and is involved in visual perception.
Visual association area
Located in the occipital lobe anterior to the primary visual area. It receives sensory impulses from the primary visual area and the thalamus. It relates present and past visual experiences and is essential for recognizing and evaluating what is seen.
Auditory association area
Located inferior and posterior to the primary auditory area in the temporal cortex. It allows you to recognize a particular sound as speech, music, or noise.
role of the reticular formation
On the brain stem, the broad region where white matter and gray matter exhibit a netlike arrangement. The reticular formation's main descending functions are to help regulate posture and muscle tone, the slight degree of involuntary contraction in normal resting muscles. Reticular activating system (RAS), which is part of the reticular formation has several functions: Sensory axons - visual, auditory, mental activities, helps arouse the body from sleep, and maintains attention and alertness (consciousness)
Gyrus
One of the folds of the cerebral cortex of the brain. Plural is gyri
The blood-brain barrier
Protects the CNS from harmful substances and pathogens by preventing passage of these substances from blood into the interstitial fluid of brain tissue. Once inside brain tissue, the cerebral arteries quickly divide into capillaries. Tight junctions seal together the endothelial cells of brain capillaries, which also are surrounded by a thick basement membrane. In addition, the processes of many astrocytes press up against the capillaries. The astrocytic processes secrete chemicals that maintain the permeability characteristics of the tight junctions, allowing selective passage of some substances from blood into brain tissue while inhibiting the passage of others.
hemispheric lateralization
Refers to the functional asymmetry of the brain which means that the two hemispheres specialize in performing certain unique functions For example, the left hemisphere receives somatic sensory signals from and controls muscles on the right side of the body, and the right hemisphere receives sensory signals from and controls muscles on the left side of the body.
Pons
Relays impulses between cerebral cortex and cerebellum and between the medulla and midbrain. Pneumotaxic and apneustic area, together with the medulla oblongata, help control breathing.
Medulla oblongata
Relays motor and sensory impulses between other parts of the brain and the spinal cord. Vital centers regulate heartbeat, breathing (together with pneumotaxic and apneustic area of pons), and blood vessel diameter. Other centers coordinate swallowing, vomiting, coughing, sneezing, and hiccuping.
Midbrain
Relays motor impulses from the cerebral cortex to the pons and sensory impulses from the spinal cord to the thalamus. Superior colliculi coordinate movements of the head, eyes, and trunk in response to visual stimuli, and the inferior colliculi coordinate movements of the head, eyes, and trunk in response to auditory stimuli. Contributes to control of movements.
concussion
Temporary alteration in function
Commissural tracts
contain axons that conduct impulses from gyri in one cerebral hemisphere to corresponding gyri in the other cerebral hemisphere.
Projection tracts
contain axons that conduct impulses from the cerebrum to lower parts of the CNS (thalamus, brain stem, or spinal cord) or from lower parts of the CNS to the cerebrum.
Anterior horn
contain cell bodies of somatic motor neurons that provide impulses for skeletal muscle contractions.
Anterior root
contains axons of motor neurons, which conduct impulses from the CNS to effectors (muscles and glands)
Posterior root
contains only sensory axons, which conduct impulses from sensory receptors in the skin, muscles, and internal organs into the central nervous system.
Primary motor area
each frontal lobe in the precentral gyrus directly anterior to the central sulcus. As is true for the primary somatosensory area, a "map" of the entire body is present in the primary motor area: Each region within the area controls voluntary contractions of specific muscles or groups of muscles. Electrical stimulation of any point in the primary motor area causes contraction of specific skeletal muscle fibers on the opposite side of the body. Different muscles are represented unequally in the primary motor area.
Primary auditory area
located in the superior part of the temporal lobe near the lateral cerebral sulcus. It receives information for sound and is involved in auditory perception.
Lumbar enlargement
provides nerves to and from the lower limbs
Cervical enlargement
supplies nerves to and from the upper limbs
Sulcus
A groove or depression between parts, especially between the convolutions of the brain. Plural is sulci
Circulation from sites of production to return into the blood stream
1) The choroid plexus of each ventricle produces CSF. 2) CSF flows through the ventricles and into the subarachnoid space via the median and lateral apertures. 3) CSF flows through the subarachnoid space. 4) CSF is absorbed into the dural venous sinuses via the arachnoid villi.
CSF functions
1)Mechanical protection: CSF serves as a shock-absorbing medium that protects the delicate tissues of the brain and spinal cord from jolts that would otherwise cause them to hit the bony walls of the cranial cavity and vertebral canal. The fluid also buoys the brain so that it "floats" in the cranial cavity. 2) Chemical protection: CSF provides an optimal chemical environment for accurate neuronal signaling. Even slight changes in the ionic composition of CSF within the brain can seriously disrupt production of action potentials and postsynaptic potentials. 3) Circulation: CSF is a medium for exchange of nutrients and waste products between the blood and adjacent nervous tissue.
Fourth ventricle
A cavity filled with cerebrospinal fluid within the brain lying between the cerebellum and the medulla oblongata and pons.
Lateral ventricles
A cavity within a cerebral hemisphere that communicates with the lateral ventricle in the other cerebral hemisphere and with the third ventricle by way of the interventricular foramen.
Cerebral aqueduct
A channel through the midbrain connecting the third and fourth ventricles and containing cerebrospinal fluid.
Thalamus
A large, oval structure located bilaterally on either side of the third ventricle, consisting of two masses of gray matter organized into nuclei; main relay center for sensory impulses ascending to the cerebral cortex. The thalamus is the major relay station for most sensory impulses that reach the primary sensory areas of the cerebral cortex from the spinal cord and brain stem. In addition, the thalamus contributes to motor functions by transmitting information from the cerebellum and basal nuclei to the primary motor area of the cerebral cortex. It also relays impulses between different areas of the cerebrum.
spinal cord
A mass of nerve tissue located in the vertebral canal from which 31 pairs of spinal nerves originate. It extends inferiorly from the medulla oblongata to the level of the first or second lumbar vertebra
Central canal
A microscopic tube running the length of the spinal cord in the gray commissure containing blood and lymphatic vessels and nerves.
Gray commissure
A narrow strip of gray matter connecting the two lateral gray masses within the spinal cord.
Role of the limbic system
A part of the forebrain, sometimes termed the visceral brain, concerned with various aspects of emotion and behavior; includes the limbic lobe, dentate gyrus, amygdala, septal nuclei, mammillary bodies, anterior thalamic nucleus, olfactory bulbs, and bundles of myelinated axons. Together with other parts of the cerebrum, the limbic system also functions in memory.
Third ventricle
A slitlike cavity between the right and left halves of the thalamus and between the lateral ventricles of the brain.
Hypothalamus
A small part of the diencephalon located inferior to the thalamus. The hypothalamus controls many body activities and is an important regulator of homeostasis. Control of the ANS, Production of hormones, Regulation of emotional and behavioral patterns, Regulation of eating and drinking, Control of body temperature, Regulation of circadian rhythms and states of consciousness
subarachnoid space
A space between the arachnoid mater and the pia mater that surrounds the brain and spinal cord and through which cerebrospinal fluid circulates.
Gray matter
A zone or layer of tissue in the CNS where the neural cell bodies, dendrites, and synapses are found; forms the core of the spinal cord, nuclei of the cerebrum, cerebral cortex, and cerebellar cortex.
poliomyelitis
Caused by a virus called poliovirus. The onset of the disease is marked by fever, severe headache, a stiff neck and back, deep muscle pain and weakness, and loss of certain somatic reflexes. In its most serious form, the virus produces paralysis by destroying cell bodies of motor neurons, specifically those in the anterior horns of the spinal cord and in the nuclei of the cranial nerves. Polio can cause death from respiratory or heart failure if the virus invades neurons in vital centers that control breathing and heart functions in the brain stem.
characteristics and symptoms of epilepsy
Epilepsy is a central nervous system disorder in which the nerve cell activity in your brain is disturbed, causing a seizure during which you experience abnormal behavior, symptoms and sensations, including loss of consciousness. Epilepsy is characterized by focal (partial) and generalized seizures. Characteristics include: "Blackouts" or periods of confused memory; Episodes of staring or unexplained periods of unresponsiveness; Involuntary movement of arms and legs; "Fainting spells" with incontinence or followed by excessive fatigue; or Odd sounds, distorted perceptions, or episodic feelings of fear that cannot be explained.
Basal nuclei
Paired clusters of gray matter deep in each cerebral hemisphere including the globus pallidus, putamen, and caudate nucleus. Together, the caudate nucleus and putamen are known as the corpus striatum. The basal nuclei receive input from the cerebral cortex and provide output to motor portions of the cerebral cortex via nuclei of the thalamus. In addition, basal nuclei have extensive connections with one another. A major function of the basal nuclei is to help regulate initiation and termination of movements. The basal nuclei help regulate the muscle tone required for specific body movements. The basal nuclei also control subconscious contractions of skeletal muscles.
decussation in the medulla oblongata
The crossing of most axons (90%) in the left pyramid of the medulla to the right side and the crossing of most axons (90%) in the right pyramid to the left side. It explains why each side of the brain controls voluntary movements on the opposite side of the body.
Protective structures that surround the brain and spinal cord
The first layer of protection for the central nervous system is the hard bony skull and vertebral column. The brain is encased within the cranial cavity of the skull, formed by the securely interlocked cranial bones. The spinal cord is located within the vertebral canal of the vertebral column. The surrounding skull and vertebral column provide a strong, protective shelter against damaging blows or bumps. The meninges are three protective, connective tissue coverings that lie between the bony encasement of the skull and vertebral column and the brain and spinal cord. The cranial meninges surround the brain and are continuous with the spinal meninges, which surround the spinal cord.
Broca's area
The frontal lobe close to the lateral cerebral sulcus. Speaking and understanding language are complex activities that involve several sensory, association, and motor areas of the cortex. The planning and production of speech occurs in Broca's area, located in one frontal lobe—the left frontal lobe in 97 percent of the population. From Broca's area, impulses pass to the premotor area to control the muscles of the larynx, pharynx, and mouth for the specific, coordinated contractions that enable you to speak. Simultaneously, impulses propagate from Broca's area to the primary motor area to control the breathing muscles and to regulate the proper flow of air past the vocal cords.
Corpus callosum
The great commissure of the brain between the cerebral hemispheres. A broad band of white matter containing axons that extend between the hemispheres.
pia mater
The innermost meaning which is a thin, transparent connective tissue layer that adheres tightly to the surface of the brain and spinal cord. It contains interlacing bundles of collagen fibers and some fine elastic fibers. Within the pia mater are many blood vessels that supply oxygen and nutrients to the brain and spinal cord.
Dura mater
The outermost of the three meninges (coverings) of the brain and spinal cord. The dura mater of the brain adheres directly to the periosteum of the interior surface of cranial bones.
White matter
The portions of the central nervous system that are abundant in axons rather than cell bodies of neurons. The colour derives from the presence of the axon's myelin sheaths
Cerebral cortex
The surface of the cerebral hemispheres, 2-4 mm thick, consisting of gray matter; arranged in six layers of neuronal cell bodies in most areas.
Function of spinal cord tracts
Tracts within the white matter of the spinal cord serve as highways for impulse propagation. Sensory input travels along these tracts toward the brain, and motor output travels from the brain along these tracts toward skeletal muscles and other effector tissues. The gray matter of the spinal cord receives and integrates incoming and outgoing information. 1) Ascending (sensory) Spinothalamic tract - pain, warmth, coolness, itching, tickling, deep pressure, crude touch 2) Posterior column - discriminative touch, light pressure, vibration, conscious proprioception 3) Descending (motor) Direct pathways - cerebral cortex voluntary movement of skeletal muscles 4) Indirect pathways - brain stem automatic movements of skeletal muscles
cerebrospinal fluid
a clear, colorless liquid that protects the brain and spinal cord against chemical and physical injuries. It also carries oxygen, glucose, and other needed chemicals from the blood to neurons and neuroglia. CSF continuously circulates through cavities in the brain and spinal cord and around the brain and spinal cord in the subarachnoid space (between the arachnoid mater and pia mater). CSF contains glucose, proteins, lactic acid, urea, cations (Na+, K+, Ca2+, Mg2+), and anions (CI− and HCO3−); it also contains some white blood cells.
Posterior root ganglion
a swelling, which contains the cell bodies of sensory neurons
Pineal gland
about the size of a small pea and protrudes from the posterior midline of the third ventricle, the pineal gland secretes the hormone melatonin, which is thought to promote sleepiness as more melatonin is liberated during darkness than in light.
Filum terminale
an extension of the pia mater that extends inferiorly and anchors the spinal cord to the coccyx
Primary somatosensory area
located in each parietal lobe in the postcentral gyrus directly posterior to the central sulcus. The primary somatosensory area receives impulses for touch, pressure, vibration, itch, tickle, and temperature (coldness and warmth), pain, and proprioception (joint and muscle position).
