* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Motor Neuron
Subventricular zone wikipedia , lookup
Nonsynaptic plasticity wikipedia , lookup
Mirror neuron wikipedia , lookup
Neuromuscular junction wikipedia , lookup
Node of Ranvier wikipedia , lookup
Resting potential wikipedia , lookup
End-plate potential wikipedia , lookup
Caridoid escape reaction wikipedia , lookup
Multielectrode array wikipedia , lookup
Neural coding wikipedia , lookup
Neural engineering wikipedia , lookup
Microneurography wikipedia , lookup
Axon guidance wikipedia , lookup
Central pattern generator wikipedia , lookup
Neurotransmitter wikipedia , lookup
Single-unit recording wikipedia , lookup
Clinical neurochemistry wikipedia , lookup
Premovement neuronal activity wikipedia , lookup
Pre-Bötzinger complex wikipedia , lookup
Biological neuron model wikipedia , lookup
Electrophysiology wikipedia , lookup
Optogenetics wikipedia , lookup
Synaptogenesis wikipedia , lookup
Molecular neuroscience wikipedia , lookup
Chemical synapse wikipedia , lookup
Development of the nervous system wikipedia , lookup
Synaptic gating wikipedia , lookup
Circumventricular organs wikipedia , lookup
Neuroregeneration wikipedia , lookup
Nervous system network models wikipedia , lookup
Neuropsychopharmacology wikipedia , lookup
Feature detection (nervous system) wikipedia , lookup
Channelrhodopsin wikipedia , lookup
Structural Classification of the Nervous System • Central nervous system (CNS) – Brain – Spinal cord • Peripheral nervous system (PNS) – Nerves outside the brain and spinal cord Functions of the Nervous System • Sensory input – gathering information – To monitor changes occurring inside and outside the body – Changes = stimuli • Integration – To process and interpret sensory input and decide if action is needed • Motor output – A response to integrated stimuli – The response activates muscles or glands Nervous Tissue: Neurons • Neurons = nerve cells – Cells specialized to transmit messages – Major regions of neurons • Cell body – nucleus and metabolic center of the cell • Processes – fibers that extend from the cell body Neuron Anatomy • Cell body – contains organelles. Neurons lack centrioles and are incapable of mitosis – Nissl substance – specialized rough endoplasmic reticulum. Attached ribosomes. Function to synthesize vital protein molecules – Neurofibrils – intermediate cytoskeleton that maintains cell shape • Extensions outside the cell body – Dendrites – short, branched receptive surfaces that conduct impulses toward the cell body – Axons – long, usually singular and conduct impulses away from the cell body Axons and Nerve Impulses • Axons end in axonal terminals • Axonal terminals contain vesicles with neurotransmitters • Axonal terminals are separated from the next neuron by a gap – Synaptic cleft – gap between adjacent neurons – Synapse – junction between nerves Nervous Tissue: Support Cells (Neuroglia) • 1. Astrocytes – Abundant, star-shaped cells – Brace neurons – Form barrier between capillaries and neurons – Control the chemical environment of the brain Figure 7.3a • 2. Microglia – Spider-like phagocytes – Dispose of debris • 3. Ependymal cells – Line cavities of the brain and spinal cord – Circulate cerebrospinal fluid Nervous Tissue: Support Cells • 4. Oligodendrocytes – Produce myelin sheath around nerve fibers in the central nervous system Figure 7.3d Nervous Tissue: Support Cells • 5. Satellite cells – Protect neuron cell bodies • 6. Schwann cells – Form myelin sheath in the peripheral nervous system Functional Classification of Neurons • Sensory (afferent) neurons – Carry impulses from the sensory receptors • Cutaneous sense organs • Proprioceptors – detect stretch or tension • Motor (efferent) neurons – Carry impulses from the central nervous system • Interneurons (association neurons) – Found in neural pathways in the central nervous system – Connect sensory and motor neurons Structural Classification of Neurons • Multipolar neurons – many extensions from the cell body. Characteristic of Motor Neurons Figure 7.8a Structural Classification of Neurons • Bipolar neurons – one axon and one dendrite. Found only associated with special senses. (Olfactory, vision) Figure 7.8b Structural Classification of Neurons • Unipolar neurons – have a short single process leaving the cell body. Sensory Neurons Figure 7.8c Nerve Impulses • The surface of the nerve cell membrane is polarized due to unequal distribution of ions on either side of the membrane • When nerve cells are at rest there is a greater concentration of Na+ ions outside the membrane and a greater concentration of K+ ions inside the membrane. (Rest Potential) • This arrangement of ions gives the outside of the membrane a positive charge with respect to the inside. • A stimulus causes a change in permeability in a region of the membrane • Na+ ions rush into the cell and K+ ions rush out depolarizing the region of the membrane • This region of depolarization is an Action Potential • An action potential in one region stimulates adjacent regions to depolarize and the action potential moves away from the point of stimulus • This moving action potential is a Nerve Impulse • The membrane is repolarized in 1/1000 sec. by active transport Continuation of the Nerve Impulse between Neurons • Impulses are able to cross the synapse to another nerve – Neurotransmitter is released from a nerve’s axon terminal – The dendrite of the next neuron has receptors that are stimulated by the neurotransmitter – An action potential is started in the dendrite Reflexes • Reflex – automatic, unconscious, and involuntary responses to stimuli • Simplest nerve pathways • Autonomic Reflexes – involve contractions of smooth muscles • Somatic Reflexes – involve contractions of skeletal muscles • Help maintain homeostasis by controlling: body temperature, heart rate, breathing rate, blood pressure and digestive activities • Patellar Reflex – (knee-jerk reflex) Employs only two neurons. Helps maintain posture • Also swallowing, sneezing, coughing, vomiting are reflexes Withdrawl Reflex Withdrawl Reflex • 1. Receptor – sets up a nerve impulse when something painful is touched • 2. Sensory the spinal cord Neuron – carries the impulse to • 3. Interneuron – conducts the impulse from the sensory to a motor neuron • 4. Motor the effector Neuron – conducts the impulse to • 5. Effector – responds to stimulation by muscle contraction