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HUMAN BRAIN = 1 TO 10 TERABYTES OF INFORMATION STORED
HUMAN BRAIN= 100 BILLION NEURONS SPINAL CORD = 13.5 MILLION NEURONS HUMAN BRAIN = 1 TO 10 TERABYTES OF INFORMATION STORED 1 TERABYTE= 1024 GIGABYTES 1 GIGABYTE = 1024 MEGABYTES SO……. 1 TERABYTE = 1,048,576 MEGABYTES
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Organization of the Nervous System and the Neuron
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Organization of the Nervous System
The Nervous System “maintains body homeostasis with electrical signals; provides for sensation, higher mental functioning, and emotional response; and activates muscles and glands.”
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3 Overlapping Functions of Nervous System
SENSORY INPUT- INTEGRATION- MOTOR INPUT-
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Works with the Endocrine System to maintain homeostasis.
Nervous System- Endocrine System-
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Organization of the nervous system can be
based on: Structural Classification- A. CNS- B. PNS- 2.Functional Classification- A. Afferent- B. Efferent-
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STRUCTURAL CLASSIFICATION
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FUNCTIONAL CLASSIFICATION
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Nervous Tissue Nervous tissue is made up of two types of cells-
Supporting and Neurons Supporting cells of the CNS are called Neuroglia or “nerve glue”. Neuroglia includes many types of cells that generally support, insulate, and protect neurons.
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Types of Neuroglial cells-
Astrocytes- Microglia- Ependymal cells- Oligodendrocytes-
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What about “gliomas”???
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Supporting Cells of the Peripheral Nervous System
Satellite cells- Schwann cells- Myelin
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And gray matter vs. white matter-
Neurilemma is found covering the neuronsof the Peripheral Nervous System and helps regenerate damaged nerve fibers Which brings us to bundles of nerve fibers- Tracts- Nerves- And gray matter vs. white matter-
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THE NEURON
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THE NEURON
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Nerve fibers may be microscopic
May extend 3 to 4 feet Neurons never touch each other Axonal terminals release neurotransmitters into the synapse
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Neurons classified according to structure and function
Functional- Sensory or Afferent- Motor or Efferent- Associative or Interneurons- 2. Structural- based on # of processes extending from cell body
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Physiology of Neurons Neurons have two major functions Irritability-
2. Conductivity-
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Irritabililty- the short version
Resting or inactive neuron is polarized A stimulus excites the neuron to become active and generate an impulse The stimulus changes the permeability of the neuron’s membrane Sodium gates open and Na diffuses into the cell Neuron is now depolarized Depolarization activates the neuron to transmit an action potential or nerve impulse
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Depolarization is followed almost immediately by repolarization
Until the neuron repolarizes it cannot conduct another impulse= absolute refractory period There also exists a relative refractory period when a stronger than usual stimulus is required
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The Action Potential
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GENERATION OF AN ACTION POTENTIAL
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Alcohol, sedatives, anesthetics-
Cold and continuous pressure- Warm or remove pressure-
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Conductivity No contact between neurons except at electrical synapses (escape reflexes, retina, heart) Axonal terminals release neurotransmitters which cause depolarization of next neuron Neurotransmitter is removed from synapse by re-uptake at axonal terminal or enzymatic breakdown
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YouTube - Neurotransmitter Synapse 3D Animation
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Peripheral Nervous System
Those nerves found outside the central nervous system Each nerve is made of bundles of neuron fibers Neuron fibers are surrounded by a delicate tissue sheath Groups of fibers are bound by coarser connective tissue wrapping to form bundles called fascicles
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CRANIAL NERVES SPINAL NERVES
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Spinal Nerves
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DISORDERS AFFECTING NEURONS
POLIOMYELITIS
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MULTIPLE SCLEROSIS- BELL’S PALSY- SHINGLES-
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And then there’s… CARPAL TUNNEL SYNDROME-
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