Module 5 - Central Nervous System PDF

Ch 9. The Central Nervous System Anatomy of the CNS: Brain and spinal cord -Separated into gray matter and white matter Gray: consists of unmyelinated somas, dendrites and axons White: mainly myelinated axons Spinal Cord  Spinal Cord Major pathways for information flowin...

Ch 9. The Central Nervous System Anatomy of the CNS: Brain and spinal cord -Separated into gray matter and white matter Gray: consists of unmyelinated somas, dendrites and axons White: mainly myelinated axons Spinal Cord  Spinal Cord Major pathways for information flowing back and forth between the brain and the skin, joints and muscles of the body Divided into four regions and each region is further divided into segments: – Cervical (8) – Thoracic (12) – Lumbar (5) – Sacral (5) – Coccygeal (1) Each segment gives rise to a bilateral pair of spinal nerves, each nerve splits into roots  Spinal cord Afferent (in) Nuclei: clusters of cell bodies in CNS Ganglia: clusters of cell bodies in PNS Efferent (out) Spinal Cord Dorsal and external lateral Ventral and interior lateral  Spinal reflex The spinal cord can act as the integrating center to initiate a response to a stimulus without receiving input from the brain Particularly important in body movement  Brain -Organ providing human species with its unique attributes -The ultimate emergent property: how do chemical and electrical signals in neurons lead to complex behaviours Individual neurons Groups of neurons Complex behaviour Reductionist (circuits, pathways, networks) Brain: 1400g, 1.4 Kg 85 billion neurons, many containing thousands of synapses 6 major divisions: 1. Cerebrum 2. Cerebellum 3. Diencephalon 4. Medulla 5. Midbrain midbrain 6. Pons  Brainstem Oldest and most primitive region of the brain, 4 major regions -ascending and descending tracts run through the brainstem -contain 11 of 12 cranial nerves: carry sensory and motor info for head and neck (not olfactory nerve) -contain many nuclei (groups of cell bodies) -involved in many basic processes in the body including arousal and sleep, muscle tone and stretch reflexes, coordination of breathing, blood pressure regulation and modulation of pain  Medulla -White matter contain all ascending somatosensory tracts and descending corticospinal tracts -90% of corticospinal tracts decussate (crossover) at the pyramids -nuclei in the medulla control many involuntary functioning: including the cardiovascular center and the medullary respiratory center -contain the vomiting center -contains the deglutition center (swallowing) -coughing, sneezing and hiccupping  Pons and midbrain Pons: contains nuclei and tracts -relays information between the cerebellum and cerebrum -assists the medulla in the coordination of breathing Midbrain (mesencephalon): junction (mesencephalon) between lower brainstem and diencephalon (nuclei and tracts) -primary function is controlling eye movement -also relays auditory and visual reflexes (movement of body in response to these stimuli) -contains the substantia nigra  Reticular formation -extends throughout the brainstem: small clusters of neuronal cell bodies interspersed among tracts (ascending and descending) -important in consciousness, arousal, attention -sends sensory and alertness info to cortex, filters -RAS inactivated during sleep, damage can induce coma -regulates muscle tone, assists in vital functions  Cerebellum -Second largest brain structure -two cerebellar hemispheres -processes sensory information and coordinates the execution of movement -sends feedback signals to motor areas of the cerebral cortex, via its connections to the thalamus helping to correct any errors and smooth the movements -regulates posture and balance  Diencephalon -lies between the brain stem and cerebrum -two primary structures: thalamus and hypothalamus -two endocrine structures: pineal gland and pituitary Thalamus (relay center): receives sensory info from optic tract, ears, spinal cord and motor info from cerebellum and projects info to cerebrum for processing Pineal gland- cyclically releases melatonin involved in sleep/wake  Diencephalon Hypothalamus: the center for homeostasis -influences autonomic and endocrine function  Pituitary Endocrine output of the hypothalamus Posterior pituitary is neural tissue Anterior pituitary is endocrine tissue Posterior pituitary (neurohypophysis) Anterior pituitary Hypothalamic- hypophyseal portal system  Cerebrum Largest and most distinctive part of the brain Gray matter include: Cerebral cortex, basal ganglia, and limbic system Area of higher processing Two hemispheres divided into 4 lobes, connected by corpus callosum  Basal ganglia (nuclei) -three nuclei collectively termed the basal ganglia (nuclei) -globus pallidus -putamen -caudate nucleus -major job is regulating the initiation and termination of movement -receives input from cerebral cortex and provides output to motor portions of the cortex  Limbic system Limbic system “emotional brain” plays a primary role in a range of emotions, including pain, pleasure, docility, affection, and anger. Also believed to play a major role in learning and memory 3 major components: Cingulate gyrus Amygdala Hippocampus  Cerebral cortex -outermost layer of the cerebrum -integrating center for the CNS Sulci vs gyri Functionally divided into three specializations: 1. Sensory areas (translate sensory input into perception) 2. Motor areas (direct skeletal muscle movement) 3. Association areas (integrate information from sensory and motor areas and help direct voluntary behaviours Each hemisphere is anatomically divided into four lobes  Cerebral lateralization (dominance) Distribution of functional areas in the two hemispheres is not symmetrical Cortex can undergo plasticity