Nervous System - Brain and Learning (PDF)

Nervous system  Brain and learning Organization of Nervous System Central Nervous System Peripheral Nervous System F: processes information F: transmits information to/from CNS Components: Components: a. brain a. nerves (bun...

Nervous system  Brain and learning Organization of Nervous System Central Nervous System Peripheral Nervous System F: processes information F: transmits information to/from CNS Components: Components: a. brain a. nerves (bundles of neuron branches) b. spinal cord b. ganglia (clusters of neuron bodies) Two tissue areas of the brain: - gray matter (composed of motor and interneuron cell bodies, dendrites, and unmyelinated axons) - white matter (composed of myelinated axons) Protection and Support of the Brain 1. The cranium provides rigid support 2. Three brain membranes, meninges, surround and partition the brain: - dura mater (tough outer layer) - arachnoid (web-like layer that secures the vessels and is filled with the fluid (CSF) - pia mater (delicate inner layer) 3. CSF cushions the brain 4. Blood-brain barrier prevents entry of harmful materials  Skin of scalp Periosteum Arachnoid granulation Bone of skull Arachnoid villus Periosteal layer Dura mater Meningeal layer Dural venous sinus Subdural space (potential space) (superior sagittal sinus) Arachnoid mater Subarachnoid space Arachnoid trabeculae Pia mater Cerebral cortex White matter Falx cerebri  2 Lateral Brain contains 4 interconnected ventricles cavities (ventricles) connected with the spinal cord’s central canal. Third ventricle Ventricles contain areas (choroid plexus) involved in the production Fourth ventricle of the cerebrospinal fluid (CSF) that allows: Central canal of spinal cord - mechanical protection (cushioning and suspension) - chemical protection (there is a highly regulated chemical environment for the brain and spinal cord The Brain – the control center of the nervous system. - Located in the skull close to the primary sensory organs - Composed of 4 major regions: 1.Cerebrum 2. Diencephalon 4. Cerebellum Midbrain 3.Brainstem Pons Medulla oblongata - 12 cranial nerves originate from the brain  Major regions of the brain: Cerebrum: (telencephalon) Functions: processing of - all complex intellectual functions (reasoning, thought, memory) - voluntary motor activities - conscious sensory activities (visual, auditory, olfactory, etc.) Structure: composed of two halves (hemispheres) separated by a longitudinal fissure The cerebrum consists of: - the outer gray matter (cerebral Cerebral cortex cortex); cell bodies/dendrites (folds= gyri, indentations = sulci) - cerebral white matter – bundles of myelinated axons that create information pathways (ex. corpus callosum connects left and right cerebral hemispheres) - cerebral nuclei – functional clusters of neuronal cell bodies (masses of grey matter) deep within the white matter. Help to regulate movements, maintain muscle tone. Cerebral (basal) nuclei Cerebral cortex Based in the location, cortex is subdivided into six lobes: Four - visible on external surface, named after the overlying cranial bones: - frontal lobe - parietal lobe - occipital lobe - temporal lobe - Two - not visible at surface: - insular lobe (deep within the lateral sulcus) - limbic lobe (arc-shaped region of cortex on the medial surface of each cerebral hemisphere)  Three categories of functional areas: - motor areas - sensory areas - association areas Motor Areas control voluntary Trunk S hou motor function Hip Arm Elb Forea l der ow Wr Knee Ha le fi nge r – Primary motor cortex ist Li ng fing nd n g r rm tt Ri le ger M Ankle id In Th d de um fi x (precentral gyrus) control er b Toes fin Ne ck e Ey voluntary skeletal muscle el i da Fa nd c e ey Lip eb activity all s an d jaw – Motor speech area, Tong u e Broca area, (left frontal Pharynx lobe, in most people) controls muscular movement for vocalization  Sensory Areas (receive and process sensory information) Primary somatosensory Hip Trunk Neck Arm er Leg ow Should m Elb Foot ear Lit H rist cortex (located on the Ind le fi nger r Rin tle fi and dd g fi nge For W Toes er ng r ge postcentral gyrus) generates b Genitals um fin e Th Ey ex Mi a complex somatic sense by se No c e Fa receiving information from - th , tee w Lip s , d ja s , an m gu a. proprioceptors (located in the muscles, e Tongu nx Phar y tendons and joints; giving the sense of relative Intra-abdominal position of various body parts) b. touch and pressure receptors c. pain receptors (=nociceptors) d. thermoreceptors  Sensory Areas (receive and process sensory information) – Primary visual cortex (occipital lobe) – Primary auditory cortex (temporal lobe) – Primary olfactory cortex (temporal lobe) – Primary gustatory cortex (insula) A clicker question follows… Association Areas are adjacent to motor and sensory regions; process and interpret data or coordinate motor response; integrate sensory inputs with memories. cor otor tex m Pr e A clicker question follows… Association Areas cor otor tex m Pr e Frontal association area (or prefrontal cortex) contains numerous connections with other parts of the brain, determines person’s personality, conscience, learning abilities, judgment, planning for future, intuition, mood, development of abstract ideas The left and right sides of the cortex are broadly similar in shape, and most cortical areas are replicated on both sides. Ex. primary somatosensory cortex The two halves of the cerebral cortex, however, are not exactly alike: some functional areas show strong lateralization, where certain functions are located primarily in one half of the brain.  Memory for shapes Verbal memory (limited language Motor speech area comprehension) (Broca’s area) Understanding of the written and spoken Musical ability language, mathematic Recognition of comprehension faces and spatial (Wernicke area) relationships In most people: The right hemisphere is usually the left hemisphere is dominant in visuospatial relationships, "dominant" for imagination, artistic skill, pattern language, numerical, perception, recognition of faces, and and scientific skills. emotional speech.  Diencephalon Contains a variety of sensory and motor pathways (white matter) which establishes the ________ between the cerebrum, the brain stem, the cerebellum Contains gray matter regulating visceral activities (maintenance of homeostasis), memory processing, emotional responses, etc.  Diencephalon A. Epithalamus -contains several structures, like: Pineal gland - endocrine gland secreting melatonin that helps to regulate day- night cycles B. Thalamus - paired oval masses of gray matter composed of many thalamic nuclei. C. Hypothalamus - contains a number of small nuclei controlling a variety of body functions B. Thalamus - paired oval masses of gray matter composed of many thalamic nuclei. 1. Processes all incoming somatic sensory information, except olfaction, before it reaches cortex and becomes conscious (acts as a filter of incoming information). e.g., “filters out” sounds in a busy cafeteria while you study B. Thalamus - paired oval masses of gray matter composed of many thalamic nuclei. 2. Contributes to the motor functions by processing the signals from the cerebellum and basal nuclei to the primary motor area of the cerebral cortex. Thus, it helps different parts of the brain to communicate to ensure coordinated movement. 3. Hypothalamus 1. Master control of the autonomic nervous system - influences heart rate, blood pressure, digestive activities, and respiration 2. Master control of the endocrine system 3. Regulation of body temperature (acts as the thermostat) 4. Control of emotional behavior (together with the limbic system) e.g., pleasure, aggression, fear, rage, sex drive 5. Control of food intake: monitors levels of nutrients, produces sensations of hunger 6. Control of water intake: monitors concentration of dissolved substances in blood 7. Regulation of sleep-wake (circadian) rhythms, directs pineal gland to secrete melatonin Brainstem 1. Connects cerebrum, diencephalon, and cerebellum to the spinal cord: acts as a bidirectional passageway (white matter) 2. Contains many autonomic and reflex centers; houses nuclei of many cranial nerves (grey matter) From superior to inferior: Midbrain Pons Medulla oblongata Relays motor impulses from Midbrain: the cerebral cortex to the pons (through the cerebral peduncles) and sensory impulses from the spinal cord to the thalamus. Superior colliculi coordinate movement of the head, eyes and trunk in response to visual stimuli Inferior colliculi coordinate movements of the head, eyes and trunk in response to auditory stimuli Internal structures of importance: a. Substantia nigra – a dark colored nucleus containing neurons producing neurotransmitter dopamine involved in movement control, emotional response, ability to experience pleasure and pain. (Degeneration of these cells is associated with Parkinson disease) b. Red nucleus – a nucleus containing rich in iron neurons. It integrates information from cerebrum and cerebellum (involuntary motor control, like in maintenance of posture) c. Reticular formation (light-gray network of neurons) Posterior Superior colliculus Cerebral peduncle Anterior Brainstem: Pons (=bridge) Bulging region on anterior brainstem Sensory and motor tracts located here connecting medulla and midbrain, cerebellum and cerebral cortex (white) Pontine respiratory center helps regulate skeletal muscles during breathing (grey) Medulla oblongata All sensory and motor tracts between brain and spinal cord passing through here (90% of motor tracts cross to the opposite side) Medulla oblongata Medulla oblongata Autonomic nuclei of medulla – Cardiac center - regulates heart’s rate and strength of contraction – Vasomotor center - controls blood pressure by altering the Medulla diameter of the arterioles oblongata – Medullar respiratory center- regulates respiratory rate, influenced by the pontine respiratory center – Other nuclei in the medulla are involved in involved in coughing, sneezing, salivation, swallowing, Clicker question follows… gagging, and vomiting.  When person’s core body temperature drops, the shivering response is triggered to maintain homeostasis. What part of the CNS is responsible for initiation of the shivering response? A. Cerebral cortex 30 B. Hypothalamus C. Epithalamus D. Thalamus 0% 0% 0% 0% 0% E. Brain stem Cere br um en cep ha lo n Br ain st em Ce reb el lu m Sp ina lc or d Di  Much of the brain stem consists of small clusters (about 100) of neuronal cell bodies (grey) interspersed among small bundles of white matter. This net-like arrangement is called - reticular formation. 1. Somatic motor control through the communication with the spinal cord – maintaining tone, balance, and posture during body movements. Communication with the cerebellum for movement coordination 2. Sleep and consciousness Sensory component, termed reticular activating system (RAS) contains sensory axons projecting to the cerebral cortex and the thalamus. It processes visual, auditory, touch stimuli and mental activities and helps us to maintain consciousness (attention, alertness, awareness) by activating large areas of cortex. Inactivation of RAS produces sleep (a state of partial consciousness from which a person can be aroused) Damage to the RAS may result in coma - a state of unconsciousness from which an individual cannot be aroused 3. Habituation – process by which the brain learns to ignore repetitive, meaningless stimuli. Ex. Getting “used to” Ex. Getting “used to” smell of perfume sound of the rain It helps to prevent sensory overload by filtering out insignificant information, so that it does not come to our conscious attention. Cerebellum (second largest part of the brain) White matter Structure: (arbor vitae) Subdivided into the left and right cerebellar hemispheres partitioned into three regions: - cerebellar cortex, outer gray matter Folia Gray of cortex that creates folds, folia matter - arbor vitae internal region of white matter - cerebellar nuclei, regions of gray Cerebellar matter that give rise to axons carrying hemisphere impulses from the cerebellum to other brain centers and spinal cord.  Cerebellum: Functions 1. It evaluates how well movements initiated by the motor areas in the cerebrum are being carried out (coordinates, “fine-tunes” skeletal muscle movements, ensuring their smoothness). How? a. it continuously receives input from sensory and motor pathways b. generate error-correcting signal to the cortex  Cerebellum: Functions 2. Stores memories of previously learned movements. 3. Helps to maintain balance and posture by collecting proprioceptive information from muscles and joints and adjusting the muscle tone in various muscles. A clicker question follows…