BIO 210 Lab Handout 10 Nervous System Cell body large rounded region of the cell biosynthetic center of the cell contains all organelles except centrioles Nucleus large round found in cell body Neurofibrils cytoskeletal elements of the neuron Nissl bodies elaborate rough ER dark staining bodies protein synthesis Mitochondria everywhere synthesize ATP Dendrite short branching processes close to the cell body main receptive or input region convey signals toward the cell body contains all organelles Axon only 1 per neuron very long axons are nerve fibers the conducting component of the neuron generate nerve impulses do not have Nissl bodies or Golgi Axon hillock cone shaped area of the cell body leading to the axon Axon terminal knoblike distal endings of terminal branches Secretory component of the neuron stores neurotransmitters in vesicles Myelin sheath whitish fatty covering on axon protects electrically insulates nerves increases speed Schwann Cell neuroglia that forms myelin sheath in PNS Nodes of Ranvier gaps in the myelin sheath Schwann cells do not touch each other Neurofibrils Dendrites Axon collateral Nucleus Axon hillock Axon Nissl bodies Mitochondria Node of Ranvier Nucleus Schwann cell Myelin sheath Axon terminal Synaptic end bulb 1 of 7 Supporting Cells Neuroglia Central Nervous System 4 types 1 Astrocytes star shaped radiating processes cling to neurons and capillaries anchoring them to their nutrient supply mop up leaked potassium ions and recycle released neurotransmitters control the chemical environment around neurons 2 Microglia small ovoid cells with long thorny processes to touch and monitor neurons transform into a macrophage that phagocytizes invading microorganisms or debris from dying neurons monitor health of neurons 3 Ependyma squamous to columnar may be ciliated line central cavities of the brain and spinal cord form a semipermeable membrane beating cilia circulates cerebrospinal fluid 4 Oligodendrocyte forms myelin sheaths in the CNS Peripheral Nervous System 1 Schwann cells form myelin sheaths around larger nerve fibers in the PNS 2 Satellite cells surround neuron cell bodies within ganglia Brain The brain is generally divided into 4 major regions 1 Cerebrum most superior portion of the brain localizes and interprets sensory inputs controls voluntary and skilled activity intellectual and emotional processing Cerebrum 2 Diencephalon central core of the brain surrounded by the cerebrum relay station to conduct sensory impulses to the cerebrum relay station for impulses to and from cerebral motor cortex memory processing integration center for involuntary nervous system regulates hormonal output of the pituitary gland produces oxytocin and antidiuretic hormone Diencephalon 3 Brain stem between the cerebrum and the spinal cord visual and auditory reflex centers relays information from the cerebrum to the cerebellum controls respiration heart rate vomiting coughing etc sensory relay to the cerebellum Brain Stem 4 Cerebellum cauliflower like dorsal to the brain stem processes information from the cerebral cortex and instructs the cerebral motor cortex resulting in proper balance posture and smooth coordinated movements Cerebellum 2 of 7 Ventricles cavities within the brain filled with cerebrospinal fluid continuous with central canal of spinal cord 1 2 3 4 lined by ependymal cells Lateral two large C shaped chambers deep within the cerebral hemispheres Third narrow within the diencephalon Fourth dorsal to the brain stem continuous with the spinal canal apertures connect to the subarachnoid space surrounding the brain with fluid Cerebral aqueduct canal like channel that connects the third and fourth ventricles Lateral ventricles Posterior Third ventricle Cerebral aqueduct Fourth ventricle Brain Exterior Meninges 3 layers of connective tissue membranes that cover and protect the brain spinal cord 1 Dura Mater outermost tough leather double layer 2 Arachnoid middle layer has threadlike spider web projections to the inner layer 3 Pia Mater innermost delicate highly vascular clings tightly to brain surface Scalp Periosteal layer Dura mater Meningeal layer Arachnoid mater Bone Pia mater 3 of 7 Cerebrum 4 Lobes Parietal Frontal Parietal Temporal Occipital Occipital Frontal Transverse fissure Temporal Cerebellum Longitudinal fissure separates the two cerebral hemispheres Transverse fissure separates the cerebrum from the cerebellum Gyri elevated ridges of tissues Sulci depressed areas between the gyri Cerebral Cortex gray matter of the brain it is located in the gyri Gray matter contains clusters of Neuron Cell Bodies in the cortex Gyrus Sulcus Cerebral cortex 12 Cranial Nerves Longitudinal Fissure I Olfactory bulb sensory for smell II Optic chiasma sensory for vision III Oculomotor mixed for eye movement IV Trochlear mixed for eye movement Facial VII Mixed for taste facial expressions Vestibulocochlear VIII Sensory for hearing balance Glossopharyngeal IX Mixed for taste swallowing V Trigeminal mixed for facial expression chewing VI Abducens mixed for eye movement Vagus X Mixed for organ sensations movements Accessory XI Mixed for head neck movement XII Hypoglossal mixed for tongue movement 4 of 7 Cerebrum 3 deep components 1 Corpus callosum major tract of fibers connecting the two cerebral hemispheres 2 Septum pellucidum membrane separating lateral ventricles of the cerebral hemispheres 3 Fornix bandlike fiber tract inferior to septum pellucidum Diencephalon 3 parts 1 Epithalamus forms roof of the 3rd ventricle A Pineal body usually dark from producing melatonin posterior to the thalamus 2 Thalamus 2 large lobes of gray matter lateral walls of 3 rd ventricle Intermediate mass slender stalk of thalamic tissue that connects the 2 lobes bridges the ventricle 3 Hypothalamus floor of the 3rd ventricle under the thalamus Pituitary gland hangs from the the hypothalamus by the infundibulum Mammillary bodies bulge exteriorly from the floor of the hypothalamus posterior to the pituitary gland Fornix Septum pellucidum Corpus Callosum Cerebrum Third ventricle Intermediate mass Thalamus Pineal body Hypothalamus Corpora quadrigemina Optic chiasma Cerebral aqueduct Pons Cerebellum Infundibulum Midbrain Arbor vitae Fourth ventricle Central canal Medulla oblongata Spinal cord Brain Stem has 3 parts 1 Midbrain between the Diencephalon and the Pons contains the Cerebral aqueduct and the Corpora quadrigemina 2 Pons 3 Medulla oblongata Cerebellum 2 small lateral hemispheres outer