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The Structure of the Nervous System. Chapter 23A. Nervous System. Brain Spinal cord Nerves Sensory organs. CNS. PNS. nerves. Neurons. neuron: nerve cell. Parts of a Neuron. Cell body Dendrites Axon myelin sheath Schwann cells axon terminal. Synapse.
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The Structure of the Nervous System Chapter 23A
Nervous System • Brain • Spinal cord • Nerves • Sensory organs CNS PNS
nerves Neurons • neuron: nerve cell
Parts of a Neuron • Cell body • Dendrites • Axon • myelin sheath • Schwann cells • axon terminal
Synapse • The junction between two neurons • Synaptic cleft
Nerve Impulse • Electrochemical pulse that moves along the membrane of a neuron • Based on movement of sodium and potassium ions • Must cross synaptic cleft by using neurotransmitters
Three Types of Neurons • Sensory neurons • Interneurons • Motor neurons
The Reflex Arc • Shortcut approach to nerve impulses • The impulse will be reflected back to the muscles or glands involved at the same time the impulse is sent to the brain.
The Reflex Arc sensory receptor sensory neuron interneuron motor neuron muscle brain
Coverings of CNS • Meninges • dura mater • arachnoid membrane • pia mater
Cerebrospinal Fluid • Fluid between the pia mater and arachnoid membrane • Fills spaces around brain and spinal cord • Nourishes and cushions
The Brain • 3 pounds • Receives 20% of the blood pumped by the heart • Pinkish-gray
The Brain • Gray matter • cell bodies and dendrites • White matter • axons and myelin sheaths
Divisions of the Brain • cerebrum • thalamus • hypothalamus • midbrain • pons • medulla oblongata • cerebellum
Cerebrum • Two hemispheres • Gyri (gyrus) • Fissures • Cerebral cortex (gray matter) • Lobes • frontal, parietal, occipital, temporal
Medulla Oblongata • Continuous with the spinal cord • Relay center between the spinal cord and the brain • Contains respiratory and cardiac control centers • Controls some reflexes
Cerebellum • Second largest part of brain • Two hemispheres • Regulates activities stimulated by the rest of the brain • Coordinates movement • Works on unconscious level
Thalamus • Two oval gray masses near center of brain • Receives sensations and decides which are important enough to be sent on • Alertness and wakefulness
Philippians 4:8 Finally, brethren, whatsoever things are true. . . honest. . . just. . . pure. . . lovely. . . of good report; if there be any virtue, and if there be any praise, think on these things.
Hypothalamus • Controls involuntary activities • body temperature • blood volume • fluid balance • appetite • emotional control (hormones)
Midbrain • Between thalamus and pons • Controls • body movements • space relationships • vision reflexes • hearing reflexes
Pons • Between medulla and midbrain • Carries information from one side of the brain to the other • Contains reflex centers that control facial expressions, chewing, sound responses, eyeball movement
Spinal Cord Facts • 31 pairs of spinal nerves • Butterfly-shaped gray matter • interneurons and cell bodies of sensory and motor neurons • White matter • myelinated axons arranged vertically
PNS • Sensory division • info from the body to the CNS
PNS • Motor division • info from the CNS to the body • somatic system (voluntary) • autonomic system (involuntary)