CNS Physiology For Bio 260

Regions and Organization of the CNS Adult brain regions 1.Cerebral hemispheres 2.Diencephalon 3.Brain stem (midbrain, pons, and medulla) 4.Cerebellum

Figure 12.6a Postcentral gyrus Central sulcus Precentral gyrus Frontal lobe (a) Parietal lobe Parieto-occipital sulcus (on medial surface of hemisphere) Lateral sulcus Transverse cerebral fissure Occipital lobe Temporal lobe Cerebellum Pons Medulla oblongata Spinal cord Cortex (gray matter) Fissure (a deep sulcus) Gyrus Sulcus White matter

Figure 12.8a Gustatory cortex (in insula) Primary motor cortex Premotor cortex Frontal eye field Working memory for spatial tasks Executive area for task management Working memory for object-recall tasks Broca’s area (outlined by dashes) Solving complex, multitask problems (a) Lateral view, left cerebral hemisphere Motor areas Prefrontal cortex Sensory areas and related association areas Central sulcus Primary somatosensory cortex Somatosensory association cortex Somatic sensation Taste Wernicke’s area (outlined by dashes) Primary visual cortex Visual association area Vision Auditory association area Primary auditory cortex Hearing Primary motor cortex Motor association cortex Primary sensory cortex Sensory association cortex Multimodal association cortex

Primary Somatosensory Cortex In the postcentral gyri Receives sensory information from the skin, skeletal muscles, and joints Capable of spatial discrimination: identification of body region being stimulated

Multimodal Association Areas Receive inputs from multiple sensory areas Send outputs to multiple areas, including the premotor cortex Allow us to give meaning to information received, store it as memory, compare it to previous experience, and decide on action to take

Figure 12.8b Frontal eye field Prefrontal cortex Processes emotions related to personal and social interactions (b) Parasagittal view, right hemisphere Olfactory bulb Orbitofrontal cortex Olfactory tract Fornix Temporal lobe Corpus callosum Premotor cortex Primary motor cortex Cingulate gyrus Central sulcus Primary somatosensory cortex Parietal lobe Parieto-occipital sulcus Somatosensory association cortex Occipital lobe Visual association area Calcarine sulcus Parahippocampal gyrus Uncus Primary olfactory cortex Primary visual cortex Primary motor cortex Motor association cortex Primary sensory cortex Sensory association cortex Multimodal association cortex

Anterior Association Area (Prefrontal Cortex) Most complicated cortical region Involved with intellect, cognition, recall, and personality Contains working memory needed for judgment, reasoning, persistence, and conscience Development depends on feedback from social environment

Posterior Association Area Large region in temporal, parietal, and occipital lobes Plays a role in recognizing patterns and faces and localizing us in space Involved in understanding written and spoken language (Wernicke’s area)

Lateralization of Cortical Function Left hemisphere – Controls language, math, and logic Right hemisphere – Insight, visual-spatial skills, intuition, and artistic skills Left and right hemispheres communicate via fiber tracts in the cerebral white matter

Basal Nuclei (Ganglia) Subcortical nuclei Consists of the corpus striatum – Caudate nucleus – Lentiform nucleus (putamen + globus pallidus) Functionally associated with the subthalamic nuclei (diencephalon) and the substantia nigra (midbrain)

Functions of Basal Nuclei Though somewhat elusive, the following are thought to be functions of basal nuclei – Influence muscular control – Help regulate attention and cognition – Regulate intensity of slow or stereotyped movements – Inhibit antagonistic and unnecessary movements

Thalamic Function Gateway to the cerebral cortex Sorts, edits, and relays information – Afferent impulses from all senses and all parts of the body – Impulses from the hypothalamus for regulation of emotion and visceral function – Impulses from the cerebellum and basal nuclei to help direct the motor cortices Mediates sensation, motor activities, cortical arousal, learning, and memory

Figure Corpus callosum Choroid plexus Thalamus (encloses third ventricle) Pineal gland (part of epithalamus) Posterior commissure Corpora quadrigemina Cerebral aqueduct Arbor vitae (of cerebellum) Fourth ventricle Choroid plexus Cerebellum Septum pellucidum Interthalamic adhesion (intermediate mass of thalamus) Interven- tricular foramen Anterior commissure Hypothalamus Optic chiasma Pituitary gland Cerebral hemisphere Mammillary body Pons Medulla oblongata Spinal cord Mid- brain Fornix

Hypothalamic Function Autonomic control center for many visceral functions (e.g., blood pressure, rate and force of heartbeat, digestive tract motility) Center for emotional response: Involved in perception of pleasure, fear, and rage and in biological rhythms and drives

Hypothalamic Function Regulates body temperature, food intake, water balance, and thirst Regulates sleep and the sleep cycle Controls release of hormones by the anterior pituitary Produces posterior pituitary hormones

Figure 12.15a Optic chiasma View (a) Optic nerve (II) Mammillary body Oculomotor nerve (III) Crus cerebri of cerebral peduncles (midbrain) Trigeminal nerve (V) Abducens nerve (VI) Facial nerve (VII) Vagus nerve (X) Accessory nerve (XI) Hypoglossal nerve (XII) Ventral root of first cervical nerve Trochlear nerve (IV) Pons Middle cerebellar peduncle Pyramid Decussation of pyramids (a) Ventral view Spinal cord Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Diencephalon Thalamus Hypothalamus Diencephalon Brainstem Thalamus Hypothalamus Midbrain Pons Medulla oblongata

Spinal Cord Physiology

Figure Somatic sensory neuron Dorsal root (sensory) Dorsal root ganglion Visceral sensory neuron Somatic motor neuron Spinal nerve Ventral root (motor) Ventral horn (motor neurons) Dorsal horn (interneurons) Visceral motor neuron Interneurons receiving input from somatic sensory neurons Interneurons receiving input from visceral sensory neurons Visceral motor (autonomic) neurons Somatic motor neurons

Figure Ascending tractsDescending tracts Fasciculus gracilis Dorsal white column Fasciculus cuneatus Dorsal spinocerebellar tract Lateral spinothalamic tract Ventral spinothalamic tract Ventral white commissure Lateral corticospinal tract Lateral reticulospinal tract Ventral corticospinal tract Medial reticulospinal tract Rubrospinal tract Vestibulospinal tract Tectospinal tract Ventral spinocerebellar tract

Example of a tract

Anterolateral Pathways Lateral and ventral spinothalamic tracts Transmit pain, temperature, and coarse touch impulses within the lateral spinothalamic tract

Figure 12.34b (2 of 2) Axons of first-order neurons Temperature receptors Lateral spinothalamic tract (axons of second-order neurons) Pain receptors Medulla oblongata Cervical spinal cord Lumbar spinal cord (b)Spinothalamic pathway

Figure 12.34b (1 of 2) Primary somatosensory cortex Axons of third-order neurons Thalamus Cerebrum Midbrain Cerebellum Pons (b)Spinothalamic pathway

Example of Clinical Consideration

Spinal Cord Trauma Spastic paralysis—damage to upper motor neurons of the primary motor cortex – Spinal neurons remain intact; muscles are stimulated by reflex activity – No voluntary control of muscles

Spinal Cord Trauma Flaccid paralysis—severe damage to the ventral root or ventral horn cells – Impulses do not reach muscles; there is no voluntary or involuntary control of muscles – Muscles atrophy