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Nervous System
Lecture
| Term | Definition |
|---|---|
| Neurons | About 99% of all neurons are interneurons, lying entirely within the central nervous system and spinal cord; the control center. |
| PNS: Peripheral Nervous System | Consists of afferent (sensory) neurons and efferent (motor) neurons. Somatic and autonomic (Visceral) |
| Enteric (visceral) nervous system | Is an extensive nerve network in the wall of the digestive tract that helps PNS control digestive activities. |
| Sensory (afferent) | Detect stimuli (light and heat) |
| Interneurons | Receive signals from other neurons and make decisions about response. |
| Motor (efferent) neurons | Send signals to provide responses. |
| Nervous System | Forms a network of excitable cells that transmit electrical and chemical signals. These excitable cells are called nerve cells or neurons. Neurons compose only 10% of nervous system. |
| 90% | Is made up of glial cells (neuroglia) which are non-excitable. They support, protect, and bind neurons together to form framework for nervous tissue. |
| Fundamental Physiological properties | -Excitability (irritability): Can respond to stimuli. -Conductivity: Can send signals to distant locations quickly. -Secretion: Can release chemical messengers (neurotransmitters). |
| Neurosoma | Soma or Cell body; Control center. |
| Nissl Bodies | Compartmentalized rough ER. |
| Dendrites | Receive signals. |
| Axon | Sends action potentials. |
| Structural Classes of Neurons Named for the numbers of dendrites and axons: | -Multipolar: Many dendrites, one axon. -Bipolar: One dendrite, one axon. -Unipolar: No dendrites, one axon; carry sensory signals to spinal cord. -Anoxic: Many dendrites, no axon. |
| CNS Glial Cells | -Astrocytes: Provide support and nourishment. -Oligodendrocytes: Myelinated to assist conduction. -Ependymal Cells: Secrete and circulate cerebrospinal fluid. -Microglia: Help in defense and disposal. |
| PNS Glial Cells | -Schwann Cells: Myelinate to assist conduction and regeneration of damaged fibers. -Satellite Cells: Provide support and nourishment. |
| Myelin | -Mainly lipid. Analogous to insulation on a wire. -Oligodendrocytes make myelin in the CNS. -Schwann Cells make myelin in the PNS. Neurilemma: outermost layer of wrapping around a Schwann cell; contains nucleus and cytoplasm. |
| Myelin continued | -Internodes: Fiber segments covered by Myelin. -Nodes of Ranvier: Fiber segments with gaps in myelin. |
| Nerve Regeneration | -CNS neurons cannot regenerate. -Schwann cells secrete nerve growth factors. -Nerve fiber: Axon. Nerve: a bundle of nerve fibers wrapped in a later of connective tissue. |
| Signal Conduction | Signal conduction speed depends on two factors: 1: Diameter of fiber; larger are faster. 2: Presence of myelin; myelinated are faster. Fastest fibers are both large and myelinated. |
| Chemical Synapse | -Presynaptic neuron releases neurotransmitter (messenger molecules) to postsynaptic cell. -Structures at a synapse: 1. Synaptic knob of presynaptic cell; contains synaptic vesicles-packets of neurotransmitters. -Synaptic cleft. |
| Electrical Synapse | -Adjacent cells joined by gap junction. -Ions diffuse from cell to cell. -Quick transmission. -Not very common in human nervous system. |
| Synapses | -Synapse= meeting point of neuron and other cell. -Presynaptic= neuron to postsynaptic neuron. -Axodendritic synapse= synapse; axon to dendrite. Axsomatic synapse= synapse to soma Axoaxonic synapse: axon to axon. |
| Diverging | One axon to several postsynaptic cells. |
| Converging | Several cells to one neuron. |
| Reverberating | Linear stimulation, re-stimulation of #1. |
| Parallel | One neuron stimulates several re-converging chains of neurons. |
| Neural Pools | May consist of thousands to millions interneurons dealing with a particular body function. example movement of limbs rhythmically while walking. Neural circuits-Interconnections between neurons. |
| CNS Central Nervous System | -Brain and spinal cord. -Consists of interneurons (about 99% of all the neurons in the human body). -Made up of delicate and sensitive tissues; need lots of protection. |
| CNS Protections | -Bones: Skull and vertebral column. -Meninges: 3 protective layers of connective tissue: Dura mater: strong mother; tough Arachnoid mater (Resembles spider's web: loose mesh of fibers) (vascularized). Pia mater (gentle mother; delicate highly vascu |
| Dura Mater | within cranium, the dura has two layers: 1. Periosteal layer. 2. Meningeal layer. In some places, the layers separate to form dural sinuses: Superior sagital sinus Transverse sinus |
| Ventricles and Cerebrospinal Fluid | -Lateral ventricles: Inter-ventricular foramen. -Third Ventricle: Cerebral aqueduct. Fourth Ventricle: Central canal and choroid plexus. |
| CFS Cerebrospinal fluid | Clear and colorless liquid. Produced by choroid plexus within ventricles. Flows within ventricles, canals and in subarachnoid space around CNS. Absorbed by arachnoid granulations into blood of superior sagittal sinus. Provides buoyancy, protection, |
| Cerebral Hemispheres | The most superior portion of the brain. The entire surface is thrown into elevated ridges of tissue called gyri (singular:gyrus), separated by shallow grooves called sulci (singular: sulcus) or deeper grooves called fissures. |
| Cerebral Hemispheres Continued | -Longitudinal fissure, a single deep fissure, divides cerebral hemispheres into right and left hemispheres. -Central sulcus separates frontal lobe from parietal lobe. -Lateral sulcus separates temporal lobe from partial lobe. |
| Gray and White Matter | Gray Matter: -Outer part (cortex) of cerebrum and of cerebellum, as well as deep nuclei. -Neurosomas, dendrites, and synapses. White Matter: -Deep in brain. -Tracts: bundles of myelinated axons. |
Created by:
carmencramirez18
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