NORMAL CELLS OF THE CNS Color index: Slides.. Important ..Notes ..Extra.. Objectives: At the end of this lecture, you should describe the microscopic structure and the function of: 1- Neurons: Cell body (perikaryon). Processes: An axon and dendrites. 2- Neuroglia: Astrocytes. Oligodendrocytes. Microglia. Ependymal cells. Axon: only one Processes Neuron components Dendrites: one or more Cell body (Perikaryon) Types of neurons based on number of processes: Unipolar neuron Has one process only, that divides into two branches; (Pseudounipolar) one acts as a dendrite and the other as an axon. (rounded neuron) e.g. Mesencephalic nucleus of trigeminal nerve Not directly connected to the cell body and dorsal root (spinal) ganglion. Bipolar Neuron Has two processes (one arising from each pole of the cell body) (spindle-shaped neuron) One of them is the dendrite and the other is the axon. like having 2 necks e.g. retina & olfactory epithelium. Multipolar neuron: Stellate Neurons (star shape) Pyramidal Neurons (wide base) Pyriform Neurons Has one axon and multiple - The commonest type. - Distributed in motor area 4 - Pear-shaped dendrites. - Distributed in most areas of CNS of the cerebral cortex. e.g. Purkinje cells of cerebellar -Its outline is irregular in shape e.g. anterior horn cells of the -Neuroglial cells are much more cortex. number than neurons in the CNS spinal cord. they can divide and regenerate normally. Cell body (perikaryon) Cytoplasm: Cytoplasm with mitochondria and ribosomes and rough Nucleus: ER only in dendrites not in axons Single, usually central, rounded and Its main components include: vesicular with prominent nucleolus. Nissl Neuro- Micro- Golgi Mito- Centriole Pigments Other bodies filaments tubles apparatus chondria Depend on age Are * Are Most basophilic intermediate *lipofuscin patches of filaments adult pigment: in rough which are Are neurons old age bundled Endoplasmic found in have Some fat Reticulum together to the cell Surrounds *Melanin (rER) and form the Are only one and rudimentary pigments: in free neurofibrils. body, nucleus all numerous. glycogen centriole, neurons of ribosomes * Are axon, & around. granules in the cell found in dendrites so they substantia body and the cell . cannot nigra of the body, axon bases of divide. midbrain wide and Nigra = Black dendrites dendrites Nissl bodies Lipofuscin pigments we can differentiate between the axon and the dendrite by Nissl bodies *Axons DO not contain Nissl bodies TYPES OF NERVE FIBERS IN CNS 1- Unmyelinated without neurilemmal sheath (in grey matter). 2- Myelinated without neurilemmal sheath (in white matter). Inside the CNS the oligodendrocytes create the Myelin sheath unlike the PNS we have the Schwann cells which produce myelin sheath Definition: Are group of cells that act as the supportive tissue of CNS. NEUROGLIA Types: 1- Astrocytes 2- Oligodendrocytes 3- Microglia 4- Ependyma 1. Astrocytes 2. Oligodendrocytes. They are the commonest type of neuroglial cells. Are branching cells with few, short They are found in both the grey and white matter. processes. General They are star-shaped cells with numerous long processes. They are distributed in the grey and information white matter of CNS. 1. Repair of injury of CNS tissue (gliosis). 1. Formation of myelin sheath in the 2. Supportive and nutritive functions CNS. Functions to the neurons. 2. Insulation of nerve fibers. 3. Participate in the formation of blood-brain barrier. (acts as a barrier) 1. Protoplasmic astrocytes: -Are found in the grey matter of CNS. -Their processes branch extensively. Types 2. Fibrous astrocytes: -Are found in white matter of CNS. -Their processes have fewer branches but longer. Definition: Are group of cells that act as the supportive tissue of CNS. NEUROGLIA Types: 1- Astrocytes 2- Oligodendrocytes 3- Microglia 4- Ependyma 3. Microglia Same as macrophages 4. Ependyma Are spindle-shaped cells with branching Are simple columnar epithelial cells processes that rise from each pole of the cell. (partially ciliated) lining the brain ventricles and General Are distributed in the grey and white matter of the central canal of spinal cord. information CNS. Are rich in lysosomes. Functions 1. Their main function is phagocytosis. 1. May be formation and circulation of CSF. Types Summary 5- One of the functions of oligodendrocytes cells? MCQ’s A. Forming BBB B. Nutritive 1- Which of the following contain Nissl Bodies? C. Phagocytosis A. Dendrites and axon D. Formation of myelin sheath B. Dendrites and cell body C. Cell body and axon 6- The type of epithelium in the Ependymal cells is? D. Only axon A. Simple squamous non ciliated B. Simple columnar partially ciliated 2- Types of nerve fibers that are found inside the CNS C. Simple cuboidal are? D. Pseudostratified A. Myelinated with neurilemmal sheath B. Unmyelinated with neurilemmal sheath 7- Mesencephalic nucleus of trigeminal nerve and dorsal C. Myelinated and unmyelinated without neurilemmal root ganglion are examples of example of? sheath A. Unipolar neuron D. Non of above B. Bipolar neuron C. Spindle shaped neuron 3- Which type of astrocyte is found in the grey matter of D. Multipolar neuron the CNS? A. Fibrous astrocytes 8- "Pyramidal neurons" are a type of multipolar neurons B. Protoplasmic astrocytes that are found in? C. Microglia A. Cerebellum cortex D. Oligodendrocytes B. Brain steam C. Cerebral cortex A - 9 C - 8 4- The supportive cells that form gliosis for repairing D. All above A - 7 injuries in the CNS are? B - 6 A. Astrocytes D - 5 9- Which one of the following is considered A - 4 B. Oligodendrocytes as the commonest type of neuron? B - 3 C. Microglia A. stellate neuron C - 2 B B - 1 D. Ependyma B. Pyramidal neuron C. Pyriform neuron D. Bipolar neuron Thank you & good luck - Histology team Done by: Allulu Alsulayhim Amal AlGarni Team leaders: Do’aa Walid Rana Barasain Shahad AlAnzan Faisal Alrabaii We’am Babaier لﻻقتراحات أو الشكاوي: https://goo.gl/forms/fg6hLipifAzVspuj1 Please if you need anything or even further explanation contact us on: [email protected] @histology436.