Overview of CNS Flashcards
What are the components of the CNS?
Cerebrum, brainstem, cerebellum and spinal cord
What are the components of the peripheral nervous system?
Cranial and spinal nerves that have processes extending from the brain and spinal cord to all parts of the body.
What are the names of the projections that receive information and the ones that transmit information?
The projections that receive information are termed dendrites, while the main projection that transmits information is the axon.
Gray Matter in the CNS (description)
Gray matter areas of the cerebrum are areas where neuronal cell bodies (somas) reside and where synapses between neurons occur. Groups of cell bodies are called often called a cortex, ganglia, nuclei, or horn.
What are some important examples of gray matter?
1) the 2-3 mm thick external layers of the cerebral cortex 2) basal ganglia: caudate, putamen and globus pallidus 3) ventral and dorsal horns of the spinal cord
White matter (general description)
White matter areas of the central nervous system are composed largely of myelinated axons or fiber tracts.
What are additional terms for a bundle of myelinated axons (WHITE matter) in the CNS?
Tract Lemniscus Fasciculus Funiculus Column Peduncle Capsule Callosum Radiation
Among others, three important white matter areas include:
- corpus callosum (largest bundle of commissural fibers connecting left and right hemispheres; seen in mid-sagittal view or transverse view) Disruption of this fiber tract produces a “split brain” syndrome. 2. optic radiations (association fibers that form the final relay pathway for transmission of visual signals from the lateral geniculate nucleus to the primary visual cortex) 3. internal capsule (projection fibers that descend from brain to brainstem and spinal cord or ascend from the lower centers to the cerebral cortex). The internal capsule has an anterior limb, genu and posterior limb. 4. cerebral peduncles, pyramids, and white matter tracts of the spinal cord
Components of the Cerebrum (CNS)
Cerebrum -Telencephalon Cerebral Cortex (hemispheres) Caudate Putamen Globus Pallidus -Diencephalon Thalamus Hypothalamus
Components of the Brainstem (CNS)
Brainstem -Midbrain -Pons -Medulla
Cerebral Cortex (description)
-The outer shell is about 3 mm thick, composed of gray matter, which is primarily neuronal cell bodies No myelin The cortical surface is highly convoluted, which increases its surface area. The cortex is the most complicated integrating area of the nervous system, and is required for processing of incoming (afferent) information into meaningful perception, and for the ultimate refinement of control over outgoing (efferent) information. The cortex is also the site of long-term memory storage and is responsible for our ability to learn motor skills.
What are the 5 lobes of the cerebrum?
Frontal, Parietal, Temporal, Occipital and Insular lobes (some anatomists divide the cerebrum into 6 lobes with the Limbic Lobe being the 6th
Frontal lobe: Primary motor cortex (functional system 1 of 4)
(M1); origin of the corticospinal, corticobulbar and corticopontine tracts.
Frontal lobe: Supplementary motor area (functional system 2 of 4)
(SMA; M2) is more active when a sequence of movements is remembered and self-determined or internally referenced. SMA receives input from the basal ganglia.
Frontal lobe: Premotor cortex (functional system 3 of 4)
The premotor complex is used in visually guided, externally referenced motor tasks. Gets input from the cerebellum which helps program the motor cortex for execution of a movement. Functions in reaching, precision grip and prehension.
Frontal lobe: Pre-frontal cortex (functional system 4 of 4)
The Pre-frontal cortex is one of the most complex parts of the brain. It integrates all judgment, behavior, imagination and emotion into a person’s unique identity or personality. Damage to this area causes disturbances of these features and alters personality, i.e. Phineas Gage.
Parietal lobe functional systems
The Parietal lobe contains the primary somatosensory cortex and somatosensory association areas. The association areas of the parietal, temporal and occipital lobes are areas that interpret sensory input and give it meaning.
Temporal lobe functional systems
Temporal lobe contains the primary auditory cortex and auditory association areas. In addition, structures in and around the medial temporal lobe play roles in olfaction, emotion, and memory, i.e. HM.
Occipital lobe functional systems
The Occipital lobe contains the primary visual cortex and visual association areas.
Insula or insular lobe functional systems
Insula or insular lobe (contains part of the limbic system, which is involved in the control of behavior and emotions). Functionally, it plays a role in diverse functions including emotions, homeostasis, perception, motor control, self-awareness, cognitive functioning, and interpersonal experience.
Gyri (singular, gyrus)
are the convoluted folds in the cortex of the cerebral hemispheres.
Sulci (singular, sulcus) and fissures
are grooves between the gyri, with fissures being the deeper of the two. Sulci and fissures are formed as a result of massive growth of the telencephalon during embryonic development.
Major sulci/fissures of the cortex: Longitudinatl fissure
Longitudinal fissure: separates left and right cerebral hemispheres (also called the interhemispheric fissure).
Major sulci/fissures of the cortex: Central sulcus
Central sulcus (or Fissure of Rolando): separates frontal and parietal lobes.
Major sulci/fissures of the cortex: Lateral fissure
Lateral fissure (or Fissure of Sylvius): separates temporal lobe below from frontal and parietal lobes above.
Major sulci/fissures of the cortex: Parieto-occipital sulcus
Parieto-occipital sulcus: separates the parietal lobe from the occipital lobe.
Major sulci/fissures of the cortex: Calcarine sulcus
Calcarine sulcus: divides the primary visual cortex into two regions: the cuneus (above the sulcus) and the lingual gyrus (below the sulcus). These regions can be seen from the mid-sagittal surface of the brain.
Some important (gyri) of the cerebral cortex include: Post Central Gyrus
primary somatosensory cortex
Some important (gyri) of the cerebral cortex include: Precentral Gyrus
primary motor cortex
Motor and sensory cortex: the homunculus
Sensory evoked potentials (i.e., cortical responses to tactile stimulation) and direct stimulation of the postcentral gyrus have been used to map the representation of the body surface (the sensory homunculus).
The homunculus and respective representations
Body areas with greater representation in the cortex have proportionally greater sensory innervation in the periphery (e.g., face & tongue vs. lower extremity). A similar motor map exists in the precentral gyrus. Areas with larger representation, have relatively greater motor innervation and finer motor control (the motor homunculus).
Some important (gyri) of the cerebral cortex include: Cuneus and Lingual Gyri
primary visual cortex
Some important (gyri) of the cerebral cortex include: Superior Temporal Gyrus
primary auditory cortex
Some important (gyri) of the cerebral cortex include: Posterior Inferior Frontal Gyrus
Broca’s area: speech center that coordinates movement of the larynx and mouth to produce speech. A lesion in this area can produce severe speech deficits (Broca’s or “expressive” aphasia) ranging from complete muteness to non-fluent (“choppy”) language production; difficulty word finding.
Some important (gyri) of the cerebral cortex include: Posterior Superior Temporal Gyrus
Wernicke’s area:. An extremely important sensory integration center located at the junction of the temporal, occipital and parietal lobes. This area is important for interpreting the meanings of speech and thoughts, whether heard, read, felt or generated within the brain itself. Lesions in this area produce deficits in comprehension of speech (Wernicke’s or “receptive” aphasia). Speech may be fluent, but lacks content.
Basal Ganglia (description)
The basal ganglia is composed of 5 nuclei. Three are considered a specialized part of the telencephalon, one is part of the diencephalon, and one is part of the midbrain. These 5 nuclei work together as a dfunctional unit. One of their main functions is motor control.
What are the 5 nuclei of the basal ganglia?
These nuclei are: 1. Caudate 2. Putamen 3. Globus Pallidus 4. Subthalamic Nuclei (in the diencephalon) 5. Substantia Nigra (in the midbrain)
Diencephalon (description)
The diencephalon consists of structures located around the third ventricle. The two most important structures of the diencephalons are the thalamus and the hypothalamus. Two other structures associated with the dienchephalon are the subthalamic nuclei and the epithalamus (pineal gland). In addition, the diencephalon also contains parts of the visual system, including part of CN II (optic n.). The medial and lateral geniculate bodies are part of the diencephalon. The left and right medial geniculate bodies are part of the auditory pathway. The left and right lateral geniculate bodies are part of the visual pathway.
Thalamus (description)
Thalamus: The thalamus is the largest component of the diencephalon and consists of over 50 discrete nuclei that act as an important center for motor control and integration of sensory input that is transmitted to the cortex (including somatosensory, visual, auditory and muscle control signals). It is the switchboard of the CNS
Hypothalamus (description)
Hypothalamus: The most important control area for the regulation of the internal environment. Vital homeostatic mechanisms and behavioral patterns that involve coordination of neural and endocrine functions (e.g., thirst, hunger, thermoregulation, hemodynamics, and complex behaviors) are controlled by the hypothalamus. It is a major regulatory center for the autonomic nervous system.
Limbic system (sometimes referred to as 6th lobe, the Limbic Lobe)
Not a single brain region, but an interconnected group of brain structures. It includes portions of frontal lobe cortex, temporal lobe, cingulate cortex, thalamus, hypothalamus, olfactory cortex, hippocampus and amygdala. The limbic system modulates activity of the autonomic system, coordinating visceral responses such as pupillary size, heart rate, blood pressure, sweating, blushing, and emotional states such as laughing and crying. The limbic system is associated with learning and emotional behavior, memory, emotion, pleasure and pain
Brainstem (Mesencephalon, Metenchephalon & Myelencephalon)
Literally the stalk of the brain, this is the region of the brain containing the midbrain, pons, and medulla. Through the brainstem pass the nerve fibers relaying signals of afferent (sensory) input and efferent (motor) output between spinal cord and the higher centers. In addition, the brainstem gives rise to 10 of the 12 pairs of cranial nerves (see anterior and lateral views of brainstem). Cranial nerves (CN) may have a motor, sensory and/or autonomic functions.
Midbrain: Mesencephalon (anatomical structures)
Midbrain: Mesencephalon The midbrain consists of many anatomical structures including: 1. ascending (sensory) and descending (motor) pathways or tracts 2. the midbrain reticular formation 3. cranial nerves III and IV (occulomotor n. and trochlear n., respectively: for control of eye movements). 4. The substantia nigra, which functions with the basal ganglia, is also located in the midbrain.
Pons: Metenchephalon (anatomical structures)
The term means “bridge”; the pons consists of many anatomical structures including: 1. ascending (sensory) and descending (motor) pathways or tracts 2. synaptic relays for information from the cerebral cortex to the cerebellum 3. cranial nerve (CN) V (trigeminal n.—sensory input from the face and motor control of mastication), CN VI (abducens n.—control of eye movements), CN VII (facial n.—control of muscles of facial expression) and CN VIII (vestibulocochlear n.—auditory and vestibular sense).
Medulla oblongata: Myelencephalon (anatomical structures)
Medulla oblongata: Myelencephalon. The medulla consists of many anatomical structures including: 1. ascending (sensory) and descending (motor) pathways or tracts 2. vital centers for the automatic control of the cardiorespiratory center 3. CN IX (glossopharyngeal n.—swallowing, taste and chemoreceptor functions), CN X (the vagus n.—cardiovascular and gastrointestinal functions) CN XI (accessory n.—neck and shoulder movement and voice control) and CN XII (hypoglossal n.—tongue movement).
Overall functions of the cerebellum (part of the Metencephalon)
Overall Functions of the Cerebellum 1. Compare actual and intended movements 2. Plan sequential movements 3. Learn coordinated movements 4. Produce synergy of movement
Anatomical Organization of the Cerebellum
The cerebellum consists of a midline structure termed the Vermis and 2 large Cerebellar Hemispheres. (anterior and posterior lobes) These structures are divided into 3 lobes by fissures.
Cerebellum Anterior Lobe
- Anterior lobe – Medial border is the vermis, - Separated from the posterior lobe by the Primary Fissure
Cerebellum Posterior Lobe
- Posterior lobe - Separated from the anterior lobe by the Primary Fissure - Separated from the Flocculonodular lobe by the Posterolateral Fissure
Cerebellum Flocculonodular Lobe
- Flocculonodular lobe – Can be observed on the ventral surface of the cerebellum - consists of 2 Flocculi (flocculus is singular) and 1 nodulus - Separated from the posterior lobe by the Posterolateral Fissure
What additional important anatomical structure is found on the ventral surface of the cerebellum?
The cerebellar tonsils. – These lie lateral to the nodulus and medial to the cerebellar peduncles.
Cerebellar White Matter Pathways
Superior, Middle, and Inferior Cerebellar Peduncles These three white matter structures consist of axons entering and exiting the cerebellum.
Meninges
The meninges (Greek: meninx, membrane) consist of 3 layers of connective tissues that protect and support the CNS: The dura mater, arachnoid layer and pia mater.
Dura mater
Dura mater: the tough, outermost layer located directly under the bony cranium and the vertebral column. Adheres to inner surface of skull. Dura is actually two inseparable layers (except regions of dural sinuses; see below). The outermost layer serves as periosteum of skull; inner layer is meningeal dura.
Arachnoid layer
Arachnoid layer: Thin and avascular; forms a roof for the CSF, which lies in the subarachnoid space. Adheres to inner surface of dura mater.
Pia mater
Pia mater: the innermost layer of meninges, intimately attached to the underlying brain and spinal cord. It is a vascular tissue supplying nutrition for the underlying neural tissue.
What are the potential spaces associated with the dura mater?
Epidural space and subdural space: these do not exist under normal circumstances, but are potential spaces that may develop under pathological conditions, particularly hemorrhage.
Ventricular system (four ventricles)
- Two lateral ventricles, 2. a midline third ventricle, 3. a midline fourth ventricle.
What connects the two lateral ventricles and the third ventricle?
The two lateral ventricles are connected to the third ventricle via the interventricular foramen.
What two ventricles are connected by the cerebral aqueduct?
-The third ventricle and fourth ventricles
Vertebral arteries (be able to identify all of these in the images from the lecture)
a. Anterior spinal artery b. Posterior spinal arteries c. Posterior inferior cerebellar arteries d. Basilar artery: vertebral arteries join to form this single midline vessel. The basilar artery gives off the following branches: e. Anterior inferior cerebellar artery f. Pontine arteries g. Superior cerebellar arteries h. Posterior cerebral arteries i. Posterior communicating arteries
Internal carotid arteries (be able to identify these)
a. Middle cerebral arteries b. Anterior cerebral arteries c. Anterior communicating artery
Circle of Willis (structures to be able to identify)
A. Basilar artery B. Posterior cerebral arteries C. Posterior communicating arteries D. Internal carotid arteries E. Anterior cerebral arteries F. Anterior communicating artery
What is the pathway of venous blood return from superficial structures of the cerebral cortex to the superior sagittal sinus?
Venous blood from superficial structures of the cerebral cortex drains into superior sagittal sinus and follows the following pathway: transverse sinus sigmoid sinus internal jugular veins superior vena cava right heart
What is the pathway of venous blood return from deeper structures of the cerebral cortex to the inferior sagittal sinus?
Venous blood from some deeper cerebral structures drains into the inferior sagittal sinus and from other deep structures into the great cerebral vein of Galen. The inferior sagittal sinus and great vein of Galen join to form the straight sinus. From the straight sinus, venous blood empties, as above, into the transverse sinus and so on, to the right heart.
What is the pathway of venous blood return from deeper structures of the cerebral cortex to the heart? (e.g., circular sinus, cavernous sinus and basilar plexus)
Venous blood from other deep structures drains into other deep sinuses (e.g., circular sinus, cavernous sinus and basilar plexus), continuing on to the jugular vein, superior vena cava, and right heart.
How many spinal nerves are in each region?
There are 31 pairs of spinal nerves: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 coccygeal.
Where does the adult spinal cord end?
about the L1 vertebral level
What cistern is found inferior to the end of the spinal cord?
Below that level is the lumbar cistern from which CSF can be withdrawn in a lumbar puncture.
What are the two enlargements observed when viewing the entire length of the spinal cord?
the cervical enlargment and the lumbosacral enlargement: Due to the presence of sensory and motor neurons supplying the extremities, the ventral horns and dorsal funiculi of SC segments at the level of the enlargements are quite large.
Contents of ventral horns
Ventral horns contain large alpha motor neurons that innervate skeletal muscles.
Cervical enlargement
The cervical enlargement lies between segments C5 , C6, C7, C8 and T1 and gives rise to spinal nerves forming the brachial plexus.
Lumbocacral enlargement
The lumbosacral enlargement lies between segments L1 through L4 to form the lumbar plexus and L4 through S2 to form the sacral plexus.
Cross-sectional anatomical features of the spinal cord to identify include:
the ventral median fissure, the dorsal median sulcus, dorsal intermediate sulcus (only present from T6 and up), and the dorsolateral sulcus.
Spinal cord gray matter
Gray - Ventral horns (motor) and dorsal horns (sensory)
Spinal cord white matter
White – Lateral, Dorsal, and Ventral columns
Clinical Syndromes: Frontal lobe
Frontal Lobe: Contralateral paralysis, impaired cognition (reasoning, self-monitoring, attention abstraction, problem solving), decreased spontaneity, impaired judgment, limited concentration, apathy, inappropriate or uninhibited social behavior.
Clinical Syndromes: Parietal lobe
Parietal Lobe: Contralateral hemisensory loss, agnosia, inattention, impaired tactile discrimination, contralateral hemianopsia, aphasia (if lesion is on left side and speech center is affected)
Clinical Syndromes: Occipital lobe
Occipital Lobe: Blindness in opposite visual field, impaired recognition, visual agnosia, alexia, impaired visual memories and recognition of color.
Clinical Syndromes: Temporal lobe
Temporal Lobe: Contralateral homonymous hemianopsia, receptive aphasia (Wernicke’s area in the left lobe), memory disturbance, epilepsy.
Clinical Syndromes: Thalamus
Thalamus: Impaired contralateral unpleasant or painful sensation–“thalamic pain”
Clinical Syndromes: Hypothalamus
Hypothalamus: Impaired autonomic functions; disturbance in regulation of temperature, salt, water metabolism, sleep-wake cycle; hormonal disorders; altered sexual functioning.
Clinical Syndromes: Basal Ganglia
Basal Ganglia: Reduced movement (hypokinesia, bradykinesia, akinesia), increased involuntary movement (tremor, choreoathetoid movements), sustained abnormal posture.
Clinical Syndromes: Brainstem
Brainstem: Altered consciousness, vertigo, nystagmus, impaired ocular movement, cranial nerve involvement, crossed sensorimotor deficits.
Clinical Syndromes: Cerebellum
Cerebellum: Poor limb coordination and balance deficits.
Clinical Syndromes: Spinal cord
Spinal Cord: Abnormal reflex activity (hyperreflexia, spasticity), paralysis, sensory loss.
