nervous system

• The Nervous System consists of two parts: the Central Nervous System (CNS) which includes the brain and spinal cord, and the Peripheral Nervous System (PNS) which is located outside of the CNS and consists of the nerves that connect the CNS with the rest of the body.
• The Nervous System has three general functions: sensory function, integrative function, and motor function.
• Sensory Nerves gather information from inside the body and from outside environment and transmit it to the brain.
• Integrative Function involves interpreting sensory information brought to the CNS.
• Motor Function involves conveying information from the CNS to muscles and glands of the body and carrying out the plans made by the CNS.
• Nervous tissue is composed of two types of cells: The neuroglia and the neurons.
• Neuroglia (Glial Cells) are the most abundant of the nerve cells and support, protect, insulate for the delicate neurons.
• Semi circular canals are part of the ampulla, with the base of each ampulla being a small elevation known as a crista.
• The cerebellum analyzes the input from CN VIII and sends information to skeletal muscles, maintaining balance and posture.
• Astrocytes are the most abundant of the glial cells and support neurons, covers surface of the brain and help form protective barrier called blood-brain barrier.
• Ependymal Cells line the inside cavities of the brain and assist formation of CNS.
• Neurons enable the nervous system; they form a vast communication network.
• Sensory Neurons carry information to the CNS.
• Motor Neurons carry information away from the CNS.
• Interneurons are found only in the CNS and form connections between sensory and motor neurons.
• Interneurons regulate motor activity.
• Dendrites receive signals from other neurons and transmit signals to cell body.
• The Cell Body contains the nucleus and is essential for life of the cell.
• The Axon is a long extension that transmits signals away from the cell body.
• The Axon is protected by the Myelin Sheath, which insulates and protects the axon.
• Unmyelinated Neurons are neurons not incased in myelin.
• Schwann surrounds the axon of neuron in PNS.
• Neurilemma consists of nuclei and cytoplasm Schwann cells lie outside myelin sheath.
• White Matter consists of clusters of cell bodies located in the CNS referred to as nuclei.
• Gray Matter consists of small clusters of cell bodies in PNS called ganglia.
• Sympathetic ganglia form a chain called paravertebral ganglia or sympathetic chain ganglia.
• Paravertebral ganglia provide the site where each preganglionic fiber synapses.
• Parasympathetic ganglia are located close to or within target organs.
• Parasympathetic fibers travel from the brain stem to four cranial nerves: Oculomotor (CN III), Glossopharyngeal (CN IX), Facial (CN VII), Vagus (CN X).
• Oculomotor Nerve (CN III) carries parasympathetic fibers to two intrinsic eye muscles: constrictor muscle of the eye- causes pupillary constriction, ciliary muscle- controls the shape of the eye lens.
• Facial Nerve (CN VII) carries parasympathetic fibers to the tear glands, salivary glands, nasal glands.
• Glossopharyngeal Nerve (CN IX) carries parasympathetic fibers to the salivary glands in the mouth.
• Vagus Nerve (CN X) carries over 80% of parasympathetic fibers and travels from the brain stem to organs within thoracic and abdominal cavities.
• Two major neurotransmitters of ANS are acetylcholine (ACh) and norepinephrine (NE).
• Fiber that secretes NE called adrenergic fiber, fiber that secretes ACh called cholinergic fiber.
• Cholinergic receptors are located on effector or target organs (cardiac muscle, smooth muscle, glands), while nicotinic neutral receptors are located within ganglia ANS.
• Adrenergic receptors are located on target organs of sympathetic nerves.
• The sensory system acts as a warning system.
• Sensory neurons transmit information to CNS.
• Five types of sensory receptors: chemoreceptors, pain receptors (nociceptors), thermoreceptors, mechanoreceptors, protoreceptors.