Introduction to the Nervous System Two Main Anatomical Parts. Central nervous system (CNS) Brain Spinal cord Peripheral nervous system (PNS) Everything else Cranial Nerves Spinal Nerves General Functions Sensory gathering information To monitor changes occurring inside and outside the body Changes = stimuli Motor A response to integrated stimuli The response activates muscles or glands Integration To process and interpret sensory input and decide if action is needed Figure 7.1 Functional Classification Sensory (afferent) division Nerve fibers that carry information to the central nervous system Motor (efferent) division Nerve fibers that carry impulses away from the central nervous system Somatic nervous system = voluntary Autonomic nervous system = involuntary Neuron processes: Axons carry electrical impulses away from the neuron cell body Dendrites Carry electrical impulses toward the neuron cell body Most, but not all neuron axons are myelinated. The myelin is highly lipid and provides electrical insulation. Cells of the Nervous System A.Neuron = Functional Cell of the Nervous System B.Neuroglia (Neuroglial Cells, Glia, Glial Cells) 1)Microglia 2)Astrocyte 3)Ependymal 4)Oligodendrocyte 5)Schwann 6)Satellite Cells 1)Microglia immune function, phagocytosis, debris removal 2)Astrocyte control the chemical environment by forming the blood/brain barrier between capillaries and neurons 3)Ependymal line cavities of brain and spinal cord, circulate CSF produced by choroid plexus 4)Oligodendrocyte forms the myelin sheath in the CNS 5)Schwann Cells forms the myelin sheath in the PNS 6)Satellite Cells forms protective barrier around neuron cell bodies Embryological Development A haploid sperm unites with a haploid egg A zygote is formed and mitotic divisions occur Morula Blastula 3 Germs Layers Germs Layers = Mesoderm, Endoderm, Ectoderm Ectoderm gives rise to Notochord Anterior bulges of notochord differentiate into Forebrain, Midbrain & Hindbrain Fig Pons, cerebellum Forebrain Midbrain Hindbrain Midbrain Forebrain Hindbrain Telencephalon Diencephalon Mesencephalon Metencephalon Myelencephalon Spinal cord Cerebrum (includes cerebral cortex, white matter, basal nuclei) Diencephalon (thalamus, hypothalamus, pineal gland) Midbrain Medulla oblongata Pituitary gland Cerebrum Cerebellum Central canal Diencephalon: Hypothalamus Thalamus Pineal gland (part of epithalamus) Brainstem: Midbrain Pons Medulla oblongata (c) Adult (b) Embryo at 5 weeks (a) Embryo at 1 month Brain Stem Development Aspects of the Nervous System No more neurons are formed after birth, but growth and maturation continues for several years The brain reaches maximum weight as a young adult