Section One

• The nervous system is a wired system that has specific structural arrangement between neurons and target cells. The neurotransmitter is released and diffused over a short distance. The response is rapid and short
• The endocrine system is a wireless system with no structural connection with one another/target cells. Hormones are released and carried in the blood over long distances. The response is slow and long-lasting, and controls activities of long duration
• The main functions of the nervous system are to detect sensory information, analyze and process information, make a decision, and execute a response
• In the CNS, clusters of cell bodies are called nuclei
• In the PNS, clusters of cell bodies are called ganglia and are outside of the CNS
• Properties of neurons include long lifespans, typically don't divide, and have a high metabolic rate (high glucose from ATP production)
• Neurons require a continuous flow of oxygen and glucose, but the brain has very little glucose stores
• Sensory or afferent neurons are going toward the CNS from sensory receptors in PNS. The cell bodies are always in ganglion outside of the CNS. These have dendrites with specialized sensory receptors
• Motor or efferent neurons carry information away from the CNS to the muscles, glands, or viscera. The cell bodies are always in the CNS.
• Voluntary movement is called somatic, whereas involuntary movement is called autonomic
• Interneurons are 99.98% of neurons and are within the CNS
• Glial cells are supporting cells that divide throughout life, are smaller and darker than neurons, and they outnumber neurons
• Glial cells in the PNS are called Schwann cells. They form myelin for the PNS
• CNS glial cells include astrocytes, microglia, ependymal cells, and oligodendrocytes
• Astrocytes are star-shaped and the most numerous. They are involved in metabolic support and homeostasis of the neuron. They are also necessary for development and maintenance of the blood brain barrier
• Microglia are phagocytes that engulf invading microorganisms
• Ependymal cells line the cavities of the CNS and spinal cord
• Oligodendrocytes produce myelin sheaths in the CNS
• The blood brain barrier creates a controlled environment for neuron excitability, protect against infection, and protect against edema. Astrocytes are critical for the tight junction formation of the blood brain barrier
• In multiple sclerosis (MS), patches of myelin are destroyed in the brain and spinal cord
• Gray matter of the CNS is where neuron cell bodies are clustered. This is the site of neuronal integration
• White matter is where millions of axons are running between different parts of CNS in bundles of "tracts". This is involved in rapid transmission
• Tracts are in the CNS whereas nerves are in the PNS
• The interior of the brain is full of white matter where the outside of the brain is gray matter. The spinal cord is the opposite of the brain.
• gray matter: H-shaped butterfly region of the spinal cord surrounds central cavity
• Gray matter: dorsal half contains cell bodies of interneurons
• Gray matter: ventral half of spinal cord contains cell bodies of motor neurons
• Sensory information from spinal cord to the brain is carried by ascending tracts
• Information carried from the brain to the spinal cord is carried by descending tracts
• Ascending and descending tracts link the PNS nerves to the brain
• Dermatome is the area of skin innervated by the sensory axons of the nerve
• Myotome is a collection of muscle fibers innervated by the motor axons of each nerve
• The dorsal root of the spinal cord contains sensory fibers (afferent). Cell bodies are located in the dorsal root ganglion
• The ventral root of the spinal cord contains motor (efferent) fibers . Cell bodies in gray matter of the spinal cord have no ganglia
• Reflexes are responses that do not require higher brain integration. Motor responses to stimuli are fast, automatic, and involuntary. They can be somatic or visceral, monosynaptic or polysynaptic, spinal or cranial
• The 5 components of reflexes include the receptor, sensory neuron, integration sensor, motor neuron, and effector
• Spinal reflexes include spinal integration, whereas cranial reflexes have the brain as the integrating center
• Somatic reflexes include skeletal muscle, whereas visceral reflexes include glands and viscera
• Monosynaptic reflexes include two neurons, whereas polysynaptic reflexes have more than two neurons
• The frontal lobe is located from the forehead to the top. It is the main motor cortex