130 likes | 461 Views
Nervous Tissue. Chapter 9. Structures of Nervous System. Brain- Neurons enclosed in skull Spinal cord – connects to brain & enclosed in spinal cavity Nerves- bundles of neuronal axons Cranial emerge from brain; spinal nerves- emerge from spinal cord
E N D
Nervous Tissue Chapter 9
Structures of Nervous System • Brain- Neurons enclosed in skull • Spinal cord– connects to brain & enclosed in spinal cavity • Nerves- bundles of neuronal axons • Cranial emerge from brain; spinal nerves- emerge from spinal • cord • Ganglia- groups of cell bodies outside brain & spinal cord • Enteric plexuses- networks in digestive tract • Sensory receptors- monitor changes in internal or external environments
Function • Sensory Receptors & afferent nerves • Carry information into brain & spinal cord • Integration- information processing • Perception = awareness of sensory input • Carry by short interneurons • Motor activity- efferent nerves • Signals to glands and muscles (effectors)
Organization • Central Nervous System (CNS) • Peripheral Nervous System (PNS) • Subdivided: Somatic (SNS) & Autonomic (ANS) nervous systems • Also • INPUT-Afferent or Sensory division • OUTPUT- Efferent or Motor division
Nervous System • Neuron= nerve cell • Specialized for signal carrying & information processing • Neuroglia cells-support, nourish & protect neurons • Neuroglia critical for homeostasis of interstitial fluid around neurons
Neuronal Structure • Cell body- nucleus, cytoplasm with typical organelles • Dendrites- highly branched input structures emerging from cell body • Axon- conducts away from cell body toward another neuron or effector • Axon terminals -at end of axon with synaptic bulbs
Myelination • Axons covered with a myelin sheath • Many layered lipid & protein creating insulations • Increases speed of nerve conduction. • Nodes of Ravier= gaps in the myelin • Some diseases destroy myelin- E.g. multiple sclerosis & Tay-Sachs
Gray and White Matter • White matter- primarily myelinated axons • Gray matter- cell bodies, dendrites, unmyelinated axons, axon terminals & neuroglia • Spinal cord gray matter is centrally located • Gray matter in brain covers surface of cerebrum & cerebellum – cortex
Neuroglia • Make-up ~ half the volume of CNS • Cells smaller than neurons • Can multiply and divide and fill in brain areas • Do not conduct nerve impulses
Neuroglia-support • Astrocytes- blood brain barrier • Oligodendrocytes- myelin in CNS • microglia - defense • Ependymal cells- CSF production • Schwann- PNS cell support • Satellite cells- in PNS ganglia