Neurophysiology - Part 5 - CNS: Brain PDF

Andre Azevedo, DVM, MSc Locum Professor of Veterinary Physiology [email protected]  soldier The CNS can be anatomically subdivided into 7 major regions 1. TELENCEPHALON or CEREBRUM 2. DIENCEPHALO...

Andre Azevedo, DVM, MSc Locum Professor of Veterinary Physiology [email protected]  soldier The CNS can be anatomically subdivided into 7 major regions 1. TELENCEPHALON or CEREBRUM 2. DIENCEPHALON (thalamus and hypothalamus) ua mesenia 3. CEREBELLUM BRAIN (1-6) 4. MESENCEPHALON or MIDBRAIN Spinal cord 5. PONS BRAINSTEM 6. MEDULLA OBLONGATA 7. SPINAL CORD  embryonicstructures Brain nomenclature comes from embryonic structures not Prosencephalon (Forebrain) = Telencephalon + Diencephalon  Year The brain can be divided into 5 major FUNCTIONAL AREAS : 1. CEREBRUM cerebrum cerebellum Thalamus 2. THALAMUS Thalamus 3. HYPOTHALAMUS hypothalamus brainstem 4. CEREBELLUM Brainstem 5. BRAINSTEM (Midbrain, Pons, and Medulla)  Cerebrumhas conscious role in sensation 1. CEREBRUM or TELENCEPHALON experience of ituntam imnanomn.ie Separated into the right and left hemispheres Plays an important role in the conscious experience of sensation, initiation of voluntary movement and cognition RIGHT HEMISPHERE THE CEREBRUM IS ALMOST COMPLETELY SEPARATED INTO THE RIGHT AND LEFT CEREBRAL LEFT HEMISPHERE HEMISPHERES SAGITAL SECTION OF THE CANINE BRAIN DORSAL VIEW OF THE CANINE BRAIN  Sulcus THE CEREBRAL CORTEX GROWS FASTER THAN THE UNDERLYING WHITE MATTER DURING DEVELOPMENT – THE SURFACE OF THE CEREBRUM IS EXTENSIVELY FOLDED Gyrus AN OUTWARD FOLD IS CALLED A GYRUS still but asulcus deep (Gr. Gyros = circle) sulcus fissure longitudinal AN INWARD FOLD IS CALLED A SULCUS (L. sulcus = groove) A DEEP SULCUS IS CALLED A FISSURE FYI 1. CEREBRUM or TELENCEPHALON Each cerebral hemisphere is composed by: 9TH attain CEREBRAL CORTEX (gray matter) GRAY MATTER IS MADE OF WHITE MATTER NERVE CELL BODIES AND THEIR PROCESSES SUBCORTICAL STRUCTURES BASAL NUCLEI* WHITE MATTER IS MADE OF HIPPOCAMPUS MYELINATED AXONS AMYGDALA (or amygdaloid body) *NUCLEI (singular form: Nucleus) is a cluster of neurons cell bodies (gray matter) involved in the same function, inside the CNS GANGLIA (singular form: Ganglion) is a cluster of neurons cell bodies (gray matter) outside the CNS 1. CEREBRUM or TELENCEPHALON CEREBRAL CORTEX Layer of gray matter at the surface of the cerebrum Involved in: Detailed sensory perception and integration Receive fibers carrying sensory signals (e.g., pain, smell, touch, hearing, vision, taste, proprioceptive, vestibular and visceral) Performing voluntary movement, including skilled movements Give rise to motor fibers that descend to the brainstem and spinal cord Cognitive function – learning, memory and intelligent behavior I  1. CEREBRUM or TELENCEPHALON The CEREBRUM/CEREBRAL CORTEX is mapped according to functional characteristics. Somatosensory area (ex: pain) Motor area (origin of corticospinal tract) Auditory and vestibular systems Greek Rhis = nose Olfactory bulb Visual Enkephalos = brain Pyriform lobe interpretation Perception of Smell 1. CEREBRUM or TELENCEPHALON The CEREBRUM/CEREBRAL CORTEX is mapped according to functional characteristics. aud = auditory area Red – motor f = frontal eye field Black – sensory ins = insular area limb = limbic cortex mot = motor cortex olf = olfactory area pfc = prefrontal cortex pre = premotor cortex sma = supplementary motor area ss1 = somatosensory area I ss2 = somatosensory area II ves = vestibular area vis = visual area  slide needtoknowthis 1. CEREBRUM or TELENCEPHALON CEREBRAL CORTEX PRIMARY CORTICAL SENSORY AREAS (detailed sensory perception) Vestibular area Areas that receive sensory signals from the brainstem and spinal cord Somatosensory area: Touch, pain, temperature, pressure, taste Visual area: Visual input Auditory area: Auditory input Vestibular area: Input form the vestibular apparatus Olfactory bulb: Olfactory input 1. CEREBRUM or TELENCEPHALON he said toknow need CEREBRAL CORTEX MOTOR CORTEX OR PRIMARY MOTOR AREA (Voluntary movement) HUMAN Give rise to motor fibers that descend to the brainstem and spinal cord Corticospinal tract or Pyramidal tract Primary motor area: muscle activation Premotor frontal cortex: plan and organize the sequence of movements Supplementary motor cortex: preparatory orientation of the body to execute a particular motor task DOG PYRAMIDS PAIR OF DESCENDING MOTOR TRACTS ON THE VENTRAL MEDULLA. Direct connection between FIBERS ORIGINATE IN THE CEREBRAL CORTEX motor cortex and cord HUMAN DOG  1. CEREBRUM or TELENCEPHALON CEREBRAL CORTEX ASSOCIATION AREAS (Learning and intelligent behavior) Involved in the integration and interpretation of information Veterinary Neuroanatomy: A Clinical Approach, 2012, Saunders/Elsevier. A complex pattern of circuitry linking sensory and motor systems (via short interneurons), memory, emotion, and behaviour IN CATS AND DOGS, THE PRIMARY ASSOCIATION AREAS INTEGRATE SENSORY SOMATIC SENSORY AREAS AND INPUTS, MEMORY MOTOR CORTEX (PROJECTION AREA) AND BEHAVIOUR ACCOUNT FOR THE VAST MAJORITY OF CENTERS TO THE CEREBRAL CORTEX PRODUCE A SPECIFIC LEARNED MOTOR OUTPUT Veterinary Neuroanatomy: A Clinical Approach, 2012, Saunders/Elsevier.  intelligence Hates us HUMAN ofneurons DOG  areher know 1. CEREBRUM or TELENCEPHALON CEREBRAL CORTEX Layer of gray matter at the surface of the cerebrum 6 separate horizontal layers parallel to the surface of the cortex I – molecular II – outer granular (external granular) III – outer pyramidal (external pyramidal) IV – inner granular (internal granular) V – inner pyramidal (internal pyramidal) VI – multiform Different distribution accordingly to functional areas (all with 6 layers)  toreceiveinto need Different distribution accordingly to functional areas (all with 6 layers) MOST INCOMING SIGNALS – LAYER IV MOST OUTPUT SIGNALS LEAVE CORTEX: LAYERS V and VI TO BRAINSTEM AND SPINAL CORD: LAYER V FIBERS TO THALAMUS: LAYER VI INTRACORTICAL ASSOCIATION FUNCTIONS: LAYER I, II, III 1. CEREBRUM or TELENCEPHALON WHITE MATTER Myelinated axons, which connect the cerebral cortex with other brain regions Divided into: PROJECTION FIBERS ASSOCIATION FIBERS COMMISSURAL FIBERS  PROJECTION FIBERS Leave the white matter and terminate in the basal nuclei, brainstem, or spinal cord Originate in the thalamus and terminate in the cerebral cortex ASSOCIATION FIBERS axonassoseFibers Connect regions of the cerebral cortex within one hemisphere COMMISSURAL FIBERS Connect cortices from right and left cerebral hemispheres (ex: Corpus Callosum) Source: 2014 Pearson Education Inc.  A COMMISSURE IS A PLACE WHERE FIBERS CROSS AND CONNECT THE 2 CEREBRAL HEMISPHERES Ex: Corpus Callosum CORPUS CALLOSUM Is the white matter (massive fiber bundle) in the brain interconnecting corresponding regions of the two cerebral hemispheres The exchange of information between both hemispheres is necessary for them to work as a functional unit A DECUSSATION IS AN INTERSECTION OF PATHWAYS IN THE FORM OF AN X. This accounts for why each side of our brain has control over the opposite side of our body. 1. CEREBRUM or TELENCEPHALON DOG SUBCORTICAL STRUCTURES: BASAL NUCLEI (Basal Ganglia) Gray matter nuclei located deep within the white matter of the cerebral hemisphere Include Caudate nucleus, nucleus accumbens, putamen, globus HUMAN pallidum, and claustrum. The Subthalamic nucleus and substancia nigra are also called Basal nuclei (because of their movement- related connections with certain telencephalic nuclei). Project output via the thalamus into the supplementary and premotor cortices Areas that are very important for planning and preparation for movement Also send the output directly to the brainstem war  BASAL NUCLEI It is an accessory motor system that helps execute the initiation and control of movement Studies in Monkeys show that changes in neuronal activity of the basal nuclei occur prior to the firing of the neuronal activity of the motor cortex and the movement of body parts Responsible for the cognitive control of motor activity – use of sensory input and memory to produce a motor action. Ex: Bear = turn around and run Inhibitory output A motor system becomes active when this inhibitory effect of the basal nuclei is released Ex: Dopamine-containing neurons of the substancia nigra play a role in regulating the inhibition Degeneration of this neurons = PARKINSON’S DISEASE End of Block CEREBRUM - summary Sensory perception and integration Voluntary movement Cognitive function – learning, memory and intelligent behavior