Anatomy of Neurons PDF

ANATOMY OF NEURONS Schwann cells - similar function as CLASSES OF NEURONS: oligodendrocytes but in the 1. Multipolar neuron - A neuron with more peripheral nervous system (present). than two processes extending from its cell...

ANATOMY OF NEURONS Schwann cells - similar function as CLASSES OF NEURONS: oligodendrocytes but in the 1. Multipolar neuron - A neuron with more peripheral nervous system (present). than two processes extending from its cell Microglia - respond to injury or body. disease by multiplying, engulfing 2.Unipolar neuron - A neuron with one cellular debris or even entire cells process extending from its cell body. and triggering inflammatory 3.Bipolar neuron - A neuron with two responses. processes extending from its cell body. - Also called FORGOTTEN CELLS 4.Interneurons - Neurons with a short axon Astrocytes - cover the outer or no axon at all. Their function is to surfaces of blood vessels that integrate neural activity within a single brain course through the brain; they structure, not to conduct signals from one appear to play a role in allowing the structure to another. passage of some chemicals from the blood into CNS neurons and in NEURONS AND NEUROANATOMICAL blocking other chemicals and they STRUCTURE have the ability to contract or relax In general, there are two kinds of gross blood vessels based on the blood neural structures in the nervous system: flow demands of particular brain those composed primarily of cell bodies and regions. those composed primarily of axons. NEUROANATOMICAL TECHNIQUES & DIRECTIONS In the central nervous system, clusters of cell bodies are called nuclei (singular NEUROANATOMICAL TECHNIQUES nucleus); in the peripheral nervous The major problem in visualizing neurons is system, they are called ganglia (singular not their minuteness. The major problem is ganglion). that neurons are so tightly packed and their axons and dendrites so intricately In the central nervous system, bundles of intertwined that looking through a axons are called tracts; in the peripheral microscope at unprepared neural tissue nervous system, they are called nerves. reveals almost nothing about them. GLIA: THE FORGOTTEN CELLS GOLGI STAIN Oligodendrocytes - are glial cells Discovered by Camillo Golgi in the with extensions that wrap around the early 1870s. axons of some neurons of the He was trying to stain the meninges, central nervous system (Present). by exposing a block of neural tissue These extensions are rich in myelin, to potassium dichromate and silver a fatty insulating (primary function) nitrate, when he noticed that the substance, and the myelin sheaths silver chromate invaded a few they form increase the speed and neurons in each slice of tissue and efficiency of axonal conduction. stained them black. - Act as a support to the neural conduction.  Golgi stains are commonly used the brain is removed and sliced; the when the overall shape of neurons is slices are then treated to reveal the of interest. locations of the injected chemical. NISSL STAIN RETROGRADE TRACING METHODS Developed by Franz Nissl in the They are used when an investigator 1880s. wants to trace the paths of axons The most common dye used is projecting into a particular area. The cresyl violet. Cressyl violet and other investigator injects into the area one Nissl dyes penetrate all cells on a of several chemicals commonly used slice, but they bind effectively only to for retrograde tracing—chemicals structures in neuron cell bodies. that are taken up by terminal buttons They often are used to estimate the and then transported backward number of cell bodies in an area, by along their axons to their cell bodies. counting the number of Nissl-stained After a few days, the brain is dots. removed and sliced; the slices are ELECTRON MICROSCOPY then treated to reveal the locations Provides information about the of the injected chemical. details of neuronal structure. Greater RETROGRADE - Travel with neurons from detail can be obtained by first the neuron terminals to the soma. coating thin slices of neural tissue ANTEROGRADE - Travel within a neuron with an electron-absorbing from the soma to the terminals. substance that is taken up by different parts of neurons to different DIRECTIONS IN THE VERTEBRATE degrees, then passing a beam of NERVOUS SYSTEM electrons through the tissue onto a Anterior – toward the nose end; photographic film. rostral. The strength of electron microscopy Posterior – toward the tail end; is also a weakness: Because the Caudal. images are so detailed, they can Dorsal – toward the surface of the make it difficult to visualize general back or the top of the head. aspects of neuroanatomical Ventral – toward the surface of structure. the chest or the bottom of the ANTEROGRADE TRACING METHODS Head. are used when an investigator wants Medial – toward the midline of the to trace the paths of axons body. projecting away from cell bodies Lateral – away from the midline located in a particular area. The toward the body’s lateral surfaces. investigator injects into Superior – top of the primate head. the area one of several chemicals Inferior – bottom of the primate head. commonly used for anterograde Proximal – means ‘close’, closer to the tracing - chemicals that are taken up CNS. by cell bodies and then transported Distal – means ‘far’, farther from the CNS. forward along their axons to their UNILATERAL - involving one side of the terminal buttons. After a few days, body.  - Uni = One Many neurons from the gray matter BILATERAL - involving both sides of the of the spinal cord send axons to the body. brain or to other parts of the spinal - Bi = Two cord through the white matter, IPSILATERAL - on the same side of the containing myelinated axons. body. - Ipsi = Same CONTRALATERAL - on the opposite side of the body. - Contra = Opposite THREE DIFFERENT PLANES OF THE BRAIN CORONAL PLANE/FRONTAL PLANE- A plane that shows brain structures as seen from the front. SAGITTAL PLANE - A plane that shows THE HINDBRAIN brain structure as seen from the side. THE MEDULLA HORIZONTAL PLANE/TRANSVERSE Or medulla oblongata, can PLANE - A plane that shows brain be regarded as an enlarged structure as seen from above. extension of the spinal cord. Just as the lower parts of the THE SPINAL CORD body connect to the spinal The spinal cord is the part of the cord via sensory and motor CNS within the spinal column. The nerves, the head and the spinal cord communicates with all organs connect to the the sense organs and muscles medulla and adjacent areas except those of the head. by 12 pairs of cranial nerves. It is a segmented structure, and Because opiate receptors, each segment has on both the left which suppress activity, are and right sides a sensory nerve and abundant in the medulla, a motor nerve. opiates can produce a The entering dorsal roots (axon dangerous decrease in bundles) carry sensory information, breathing and heart rate. and the exiting ventral roots carry THE PONS motor information. Lies anterior and ventral to the The cell bodies of the sensory medulla. Like the medulla, it neurons are in clusters of neurons contains nuclei for several cranial outside the spinal cord, called the nerves. dorsal root ganglia. The term pons is Latin for “bridge,” The H-shaped gray matter in the reflecting the fact that in the pons, center of the cord is densely packed axons from each half of the brain with cell bodies and dendrites. cross to the opposite side of the spinal cord so that the left  hemisphere controls the muscles of covers several other midbrain the right side of the body and the structures. right hemisphere controls the left SUBSTANTIA NIGRA side. Gives rise to a dopamine-containing THE CEREBELLUM pathway that facilitates readiness for Is a large hindbrain structure movement. with many deep folds. It has THE FOREBRAIN long been known for its THALAMUS contributions to the control of The thalamus is a pair of structures movement and is important (left and right) in the center of the for balance and coordination. forebrain. People with damage to the It resembles two small avocados cerebellum have trouble joined side by side, one in the left shifting their attention back hemisphere and one in the right. and forth between auditory Most sensory information goes first and visual stimuli to the thalamus, which processes it (Courchesne et al., 1994). and sends output to the cerebral They have difficulty with cortex. An exception to this rule is timing, such as judging olfactory information, which goes whether one rhythm is faster from the olfactory receptors to the than another. The cerebellum olfactory bulbs and then directly to is also critical for certain the cerebral cortex. types of learning and Many nuclei of the thalamus receive conditioning. their input from a sensory system, THE MIDBRAIN such as vision, and transmit TECTUM information to a single area of the It is the roof of the midbrain and has cerebral cortex. The cerebral cortex swelling on each side which are the sends information back to the superior colliculus and the inferior thalamus, prolonging and magnifying colliculus. certain kinds of input and focusing Both the superior and inferior attention on stimuli. colliculus are important for sensory HYPOTHALAMUS processing – the inferior colliculus Partly through nerves and partly by for hearing and the superior releasing hormones, the colliculus for vision. hypothalamus conveys messages to TEGMENTUM the pituitary gland, altering its Lies under the tectum and is release of hormones. Damage to considered as the intermediate level any hypothalamic nucleus leads to of the midbrain. abnormalities in motivated In Latin, tegmentum means a behaviors, such as feeding, drinking, “covering,” such as a rug on the temperature regulation, sexual floor. The tectum covers the behavior, fight- ing, or activity level. tegmentum, but the tegmentum PITUITARY GLAND  Is an endocrine HIPPOCAMPUS (hormone-producing) gland attached Is critical for certain types of to the base of the hypothalamus. In memories, especially response to messages from the memories for individual hypothalamus, the pituitary events. It is also essential for synthesizes hormones that the blood monitoring where you are carries to organs throughout the and where you are going. body. THE CEREBRAL CORTEX BASAL GANGLIA OCCIPITAL LOBE A group of subcortical structures It is the main target for visual lateral to the thalamus, include three information. The posterior pole of the major structures: the caudate occipital lobe is known as the nucleus, the putamen, and the primary visual cortex, or striate globus pallidus. cortex. Destruction of any part of the It has long been known that damage striate cortex causes cortical to the basal ganglia impairs blindness in the related part of the movement, as in conditions such as visual field. Parkinson’s disease and In short, the eyes provide the Huntington’s disease. The basal stimulus, and the visual cortex ganglia integrate motivational and provides the experience. emotional behavior to increase the THE PARIETAL LOBE vigor of selected actions. The parietal lobe lies between the They are also critical for learned occipital lobe and the central sulcus, skills and habits, as well as other a deep groove in the surface of the types of learning that develop cortex. The area just posterior to the gradually with extended experience. central sulcus, the postcentral gyrus, BASAL FOREBRAIN or primary somatosensory cortex, One of the structures on the ventral receives sensations from touch surface of the forebrain, the nucleus receptors, muscle-stretch receptors, basalis, receives input from the and joint receptors. hypothalamus and basal ganglia and The postcentral gyrus includes four sends axons that release bands of cells parallel to the central acetylcholine to widespread areas in sulcus. Separate areas along each the cerebral cortex. band receive simultaneous The nucleus basalis is a key part of information from different parts of the brain’s system for arousal, the body. Two of the bands receive wakefulness, and attention. Patients mostly light-touch information, one with Parkinson’s disease and receives deep-pressure information, Alzheimer’s disease have and one receives a combination of impairments of attention and intellect both. because of inactivity or deterioration The parietal lobe monitors all the of their nucleus basalis. information about eye, head, and. body positions and passes it on to brain areas that control movement.  The parietal lobe is essential not The posterior portion is associated mostly only for spatial information but also with movement. The middle zone numerical information. pertains to working memory, cognitive TEMPORAL LOBE control, and emotional reactions. It is the primary cortical target for auditory information. The human The anterior zone of the prefrontal cortex temporal lobe—in most cases, the is important for making decisions, left temporal lobe—is essential for evaluating which of several courses of understanding spoken language. action is likely to achieve the best outcome. The temporal lobe also contributes to complex aspects of vision, including perception of movement and recognition of faces. The temporal lobes are also important for emotional and motivational behaviors. Temporal lobe damage can lead to a set of behaviors known as the Klüver-Bucy syndrome. FRONTAL LOBE The frontal lobe, containing the primary motor cortex and the prefrontal cortex, extends from the central sulcus to the anterior limit of the brain. The posterior portion of. the frontal lobe, the precentral gyrus, is specialized for the control of fine movements, such as moving a finger. The most anterior portion of the frontal lobe is the prefrontal cortex. Prefrontal lobotomy—surgical disconnection of the pre-frontal cortex from the rest of the brain. The surgery consisted of damaging the prefrontal cortex or cutting its connections to the rest of the cortex. FUNCTIONS OF THE PREFRONTAL CORTEX An analysis of thousands of studies concluded that the pre- frontal cortex has three major regions (de la Vega, Chang, Banich, Wager, & Yarkoni, 2016).