Text of Organization of the Nervous System and the Neuron
Organization of the Nervous System and the Neuron
Organization of the Nervous SystemThe Nervous System maintains body homeostasis with electrical signals; providesfor sensation, higher mental functioning, and emotional response; and activates muscles and glands.
3 Overlapping Functions of Nervous SystemSENSORY INPUT-
Works with the Endocrine System to maintain homeostasis.
Organization of the nervous system can bebased on:
Nervous TissueNervous 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.
Types of Neuroglial cells-
What about gliomas???
Supporting Cells of the Peripheral Nervous SystemSatellite cells-
Nerve fibers may be microscopic up to a length of 3-4 feetNeurons never touch each otherAxonal terminals release neurotransmitters into the synapseMost long nerve fibers are myelinated or covered with a white fatty sheath called myelin which protects and insulates fibers and increases transmission rate of nerve impulses
Neurilemma is found covering the neuronsof the Peripheral Nervous System and helps regenerate damaged nerve fibers
Which brings us to bundles of nerve fibers-
And gray matter vs. white matter-
Neurons classified according to structure and functionFunctional-
Sensory or Afferent-Motor or Efferent-Associative or Interneurons-
2. Structural- based on # of processes extending from cell body
Physiology of NeuronsNeurons have two major functions
Irritabililty- the short version
Resting or inactive neuron is polarizedA stimulus excites the neuron to become active and generate an impulseThe stimulus changes the permeability of the neurons membrane Sodium gates open and Na diffuses into the cellNeuron is now depolarized Depolarization activates the neuron to transmit an action potential or nerve impulse
Depolarization is followed almost immediatelyby repolarization
Until the neuron repolarizes it cannot conductanother impulse= absolute refractory period
There also exists a relative refractory periodwhen a stronger than usual stimulus is required
Alcohol, sedatives, anesthetics-
Cold and continuous pressure-
Warm or remove pressure-
YouTube - Neurotransmitter Synapse 3D Animation
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 Conductivity
Peripheral Nervous SystemThose nerves found outside the central nervous systemEach nerve is made of bundles of neuron fibers Neuron fibers are surrounded by a delicate tissue sheathGroups of fibers are bound by coarser connective tissue wrapping to form bundles called fascicles