2.-Neuroanatomical-and-Neurophysiological-Bases-of-Behavior-lec.pdf

THE NERVOUS SYSTEM Maribi Maria Benita E. Balagan A. Importance of studying the Nervous System A. It helps us understand sensory functions and how they aid in perception. B. It helps us understand neural activity in connection with muscular movement and coordination. C...

THE NERVOUS SYSTEM Maribi Maria Benita E. Balagan A. Importance of studying the Nervous System A. It helps us understand sensory functions and how they aid in perception. B. It helps us understand neural activity in connection with muscular movement and coordination. C. It shed light on the relation of internal states such as emotions and drives.  It aids in understanding how brain cells function in learning and memory. It has practical implications to maladjustment and behavioral disorders.  Basic questions about the human brain: How does the brain maintain and repair itself over the life span and how are these capacities related to behavior How does the brain acquire, process and use information about the environment?  How does the brain monitor and regulate motivated behaviors such as production, eating, energy balance, sleeping, waking and emotions? How does the brain acquire and store information and make it available for use?  Methods and approaches: Philosophical – views that mental states stem-up from bodily states. ( Hippocrates) Clinical approach – it puts much concern on bodily disorders and how they affect behavior and mental activity. Experimental approach – requires the formulation of hypotheses and deduction. The most common method used in Biological and Physiological Psychology.  Microscopic view of the Nervous System Neuron doctrine – the brain is composed of separate cells that are distinct units; that is, the cells are separate structurally, metabolically and functionally. ( Ramon Cajal) Nervous system – body system that transmits, integrates and discriminates sensory information.  Parts of the nerve cell Nerve cell body – contains the nucleus; it includes the genetic instructions and also controls all metabolic activities of the cell. It contains millions of protein molecules, lipid molecules, RNA molecules and potassium ions. It primarily receives and integrates sensory information.  Axon – conducts impulses away from the cell body Collaterals- branches of axon Myelin sheath – accessory cell that wraps the axon; it improves the speed of conduction of neural impulses. Schwann cells – accessory cells that form the myelin sheath  Node of Ranvier – the gap where axon membrane is exposed. Axonal transport or protoplasmic streaming is the process by which materials synthesized in the cell body are transported to the distant axons and dendrites.  Dendrites – extension of nerve cells that arise from the cell body and branch out in highly complex ways. Synapse Synaptic bouton – swelling of the axon terminal which contains many spherical components. Post synaptic membrane Synaptic cleft – a space between the presynaptic and post synaptic elements.  Synaptic transmitter – substance that flows across the synaptic cleft and produces changes in the post synaptic membrane The changes in the post synaptic membrane are the basis of transmission of excitation or inhibition from one cell to another. The surface of the postsynaptic membrane contains special receptors that capture and react to molecules of the transmission agent.  Types of nerve cells A. Structure: multipolar neuron – nerve cells with many dendrites and a single axon Ex: cortical pyramidal cells Bipolar neuron – are nerve cell with a single dendrite at one end of the cell and a single axon at the other end.  Unipolar – nerve cells with a single branch leaving a cell body which then extends in 2 directions. Ex: nervous system of invertebrates  In terms of size: Small – granules, spindle and stellate Large: Pyramidal cells Golgi type Purkinjie cells  The glial cells They are the most abundant cells found in the region of the primate brain. Functions: To provide structural support of the neural elements within the CNS It provides a pathway from the vascular system to the nerve cells. It delivers raw materials that nerve cells use to synthesize complex compounds. It produces myelin sheath  Types: Astrocyte – “astra” ; they are star-shaped cell with numerous processes or extension that run in all directions. Oligodendrocyte – “oligo”; much smaller than an astrocyte and has fewer physiologic processes. Microglia – they are extremely small, they are activated by disease states to remove cellular debris from injured or dead cells  Synaptic transmission The neurotransmitter is synthesized in the cell body of the neurons ( this is sometimes called the presynaptic neuron) and then is transported down the axon to the axon terminal. Neurotransmitters are stored in the synaptic vessicle  When an electrochemical impulse or action potential reaches the axon terminal, it causes the contents of the vesicles to release into the synapse. The neurotransmitter crosses the synapse and occupies the receptor sites on the dendrites of the next neuron ( postsynaptic neuron)  When the neurotransmitter occupies the receptor sites, it allows Na to enter the post synaptic cell and the entire process begin again. The neurotransmitter is either recycled or taken back into the axon terminal of the post synaptic neuron and stored in the vesicles to be used again or is inactivated by enzymes in the synapse.  Clip 1: Nervous System (http://www.youtube.com/watch?v=UabDiuTtU0M Orientation of the Brain https://www.youtube.com/watch?v=f_hxX_xvHQY The Central Nervous System 1. Myelencephalon (medulla) Most posterior region of the brain Composed of tracts carrying signals between the rest of the brain and body It controls vital activities such as breathing, heart beat and blood circulation.  An interesting part of the myelencephalon is the reticular formation Reticular formation – is a complex network of about 100 tiny nuclei that occupies the central core of the brain stem from the posterior boundary of the myelencephalon to the anterior boundary of the midbrain The reticular formation is involved in sleep, attention, movement, maintenance of muscle tone and various cardiac circulatory and respiratory reflexes  B. Metencephalon – it houses many ascending and descending tracts and forms part of the reticular formation. Pons – a bulge in the brain stem located at the ventral surface. Cerebellum – an important sensorimotor structure which is largely convoluted; and is located on the dorsal surface of the brain stem. It is responsible for maintaining balance and posture C. Mesencephalon ( Midbrain) Tectum (roof) – it is located at the dorsal surface of the midbrain. Inferior colliculli ( little hill) – posterior pair which has an auditory function. Superior colliculi – it has a visual function Tegmentum – it is located ventral to the tectum  Structures of the tegmentum Periaqueductal gray – gray matter around the cerebral aqueduct. It is the duct connecting the 3rd and 4th ventricles of the brain. It has a role in mediating the pain-reducing effects of opiate drugs. Substantia nigra Red nucleus  The Basal Ganglia https://www.youtube.com/watch?v=InJByqg1x-0  Diencephalon A. Thalamus – the large two-lobed structure that constitutes the top of the brain stem. The two lobes are joined by the substantia nigra by the mass intermedia which runs through the ventricles The white lamina are myelinated axons that run through its surface  Sensory nuclei receives signals from sensory receptors, process them and then transmits them to the appropriate area of sensory cortex. Lateral geniculate nuclei – tracts of the visual system Medial geniculate nuclei – auditory system Ventral posterior nuclei – somatosensory system B. Hypothalamus – plays an important role in the regulation of several motivated behavior. - it exerts its effects in part by regulating the release of hormones from the pituitary gland. - optic chiasm – a point at which the optic nerve from each eye come together. The x-shaped is created because some of the axons of the nerve decussate.  Mamillary bodies – pair of spherical hypothalamic nuclei located in the inferior surface D. Telencephalon – largest division of the human brain A. cerebral cortex – deeply convoluted; convolutions have the effect of increasing the amount of cerebral cortex without increasing the over all volume of the brain  The large furrows in a convoluted cortex are called fissures and the small ones are called sulci. The ridges between fissures and sulci are called gyri. Longitudinal fissure – divides the cerebral hemisphere. Corpus callosum – large cerebral commissure Central and lateral fissures divide each hemisphere into four lobes  Precentral gyri – it contains the motor cortex Post central gyri – contains the somatosensory area Superior temporal gyri- contains the auditory cortex. Neocortex ( new cortex) – a six- layered cortex  3 important characteristics of neocortex anatomy: There are two fundamentally different kinds of cortical neurons: the pyramidal and stellate cells. Pyramidal cells are large multipolar neurons with pyramid-shaped cell bodies and a large dendrite called apical dendrite that extends from the apex of the pyramid straight towards the cortex surface and a very long axon.  The six layers of the cortex differ from one another in terms of the size and density of their cell bodies and the relative proportion of pyramidal and stellate cell bodies that they contain. Many long axons and dendrites course vertically through the neocortex. This vertical flow of information is the basis of columnar organization; neurons in a given vertical column often forms a mini circuit that forms a single function.  There are variations in the layer from area to area. Ex: the stellate cells of layer IV are thick because they are specialized for receiving sensory signals from the thalamus. Conversely, because the pyramidal cells of layer V conduct signals from the neocortex to the brain stem and spinal cord, layer V is extremely thick in areas of the motor cortex.  Hippocampus –it is located at the medial edge of the cerebral cortex as it folds back on itself on the medial temporal lobe. This folding produces a shape that looks like a sea horse. It is responsible for the formation of memories The Hippocampus https://www.youtube.com/watch?v=ErpxEwlWww4  Corpus Callosum – a deep bridge of nerve fibers that connects the 2 cerebral hemispheres. It has an intricate pattern of folds –hills and valleys- called convolutions to fit inside the skull. Sensory projection area – it is where messages from sense receptors register Motor projection area – it is where response messages start their trip down the brain stem to “tell” the muscles and glands what to do.  Lobes of the brain: Frontal lobe – forms the anterior portion of each hemisphere. It controls voluntary muscle functions, mood aggression, aggression, smell reception and motivation Parietal lobe – located behind frontal lobe. It is the control area for evaluating sensory information of touch, pain, balance, taste and temperature.  Temporal lobe – it is found beneath the frontal lobe and parietal lobe. It evaluates hearing input and smell as well as being involved with memory processes. It also functions as an important center for abstract thoughts and judgment decisions. Occipital lobe – it forms the back portion of each hemisphere. It functions in receiving and interpreting visual input.