Diencephalon Coursework Materials

DIENCEPHALON ● Superior to the brainstem and inferior to the corpus callosum Basal ganglia - Made up of 5 nuclei in the brain - Deep to the cortex - Different levels of processing within the same set of nuclei, just different connections through different paths - Image 2 just shows pathways for how the nuclei are connected - Motor circuit (movement) - Associative circuit (assess whether the task is worth performing → assess value of outcome) - Limbic circuit (experience reward, reinforcement) Thalamus - Sits in the midline on either side of the third ventricle - Sensation and motor output of the brain goes here and the information is distributed to various parts of the brain that need it - Many nuclei bundled together - Thalamus decides where the information goes and if it can go to other places in the brain, what info can go in for processing (in the cerebral cortex) - Filtering out the background noise, doesn’t need to process the other information - Like an executive assistant who determines who can come in an see the CEO Hypothalamus ● ● ● ● ○ ○ ○ ○ ○ ○ Anterior and inferior to the thalamus Forms the walls of the anterior part of the third ventricle Regulates body homeostasis (thirst, hunger, sexual feelings hormones, temperature regulation) Controls ANS function (autonomic) ○ Influenced by the frontal cortex and limbic cortex ○ Startle response, immediate action before the information can be processed ● Amygdala Involved in the body’s fear response Has connections to the thalamus and hypothalamus Exerts fear response through the hypothalamus (startle response - increased heart rate, sweating) Frontal lobe decision making - can decide if it’s a fear response (dampens the response e.g. gun fire in a movie) Amygdala is activated and the frontal lobe decides in time what the appropriate way to respond is Limbic system can override the frontal lobe (survival instinct) - react to seeing a snake rather than thinking about if it’s a snake or not Cerebral connections ● Connection between one area of the brain and another, some that don’t connect (can't communicate) ● Association fibres - Link areas in the same cerebral hemisphere ● Commissural fibres - Transverse fibres that link the same areas in OPPOSITE hemispheres (e.g. linking both sides of the corpus callosum together) ● Projection fibres - Impulses entering the brain = ascending (sensory) - Impulses exiting the brain = descending (motor) - Project in and out of the CNS Lateralisation Corpus callosum ● Links information from the left and right hemisphere ● Lateralized systems ● White matter structure ● Lots of axons and the ends of them packed very tightly together ● ● ● ● ● Split brain - when the corpus callosum is cut and the two sides of the brain cannot communicate with each other Language localisation occurs Speech production is only performed by the left, cannot get any info from the right hemisphere of the brain Right visual field is processed in the left hemisphere of the brain Left visual field is processed in the right hemisphere of the brain ● Bridges the brainstem structures and the brainstem ● ● ● Buoyancy reduces damage to the tissues of the nervous system Fluid slows down movements - like being in a swimming pool No blood vessel directly into the brain - removes the waste and nourish the brain, remove disease and infection Cerebrospinal fluid ● Not serous fluid but has a similar function ● Produced inside the brain ● Circulates around the brain and spinal cord ● Ventricles are the membranes that make CSF and distribute it ● Shape is indicative of where the membranes are located in the hemisphere of the brain ● Fissures Key Terms Definitions Afferent (A for approach) Input signals that go to the CNS Efferent (E for exit) Signals that exit the CNS Axon Conducts action potentials away from the cell body (electrical signals are generated in the cell body) Ganglion Collection of cell bodies in the PNS with a similar function Nucleus Collection of cell bodies in the CNS with a similar function Tract/funiculus/fasciculus/column Lots of CNS axons in white matter that take sensory information in through ascending pathways or motor neurons out through descending pathways (Normally use column when you’re referring to the spine) Lower motor neuron Has cell body in the spinal cord and axons go to the muscle (exits the CNS) Cell body in the ventral horn of the spinal cord and an axon that supplies nerves to the skeletal muscle Upper motor neuron Neuron that leaves the brain and runs down the spinal cord (stays in the CNS) Has cell bodies in the forebrain/midstem and sends their axons to activate lower motor neurons