Biology (Nervous System)

• Neurons


  basic unit of the nervous system that is responsible for body regulation, via the endocrine system
• The nervous and endocrine systems allow communication among the different organs to keep the body in a state of balance for growth, development, reproduction, and survival.
• The Nervous System


  keeps the body working properly despite the constant changes (stimuli) that take place around it
• Stimuli


  any internal or external changes that cause a response.
• Homeostasis


  body's ability to maintain constant internal equilibrium
• Neurons/Nerve Cells


  carry information through the body in the form of nerve impulse
• Nerve Impulse


  an electrical signal that travels along a nerve fiber in response to a stimulus
• Cell Body


  contains genetic information, maintains the neuron's structure, and provides energy to drive activities
• Dendrites


  threadlike structures that receive and carry information toward the cell body
• Axon


  carries nerve impulses away from the cell body
• Nerve Fiber


  composed of an axon and its myelin sheath
• Nissl bodies


  the main site of protein synthesis in the neuronal cytoplasm
• Myelin sheath


  protects the axons and helps speed nerve transmissions
• Axon terminals


  ends of axons which transmit messages to the dendrites of other neurons
• Nodes of Ranvier


  gaps between myelin sheath
• Schwann cells


  any of the cells in the peripheral nervous system that produce the myelin sheath
• Neurilemma


  the plasma membrane layer of the Schwann cells
• Oligodendrocytes and Schwann Cells


  engaged in myelin production, maintenance and repairing respectively in the central nervous system (CNS) and the peripheral nervous system (PNS)
• Fiber Tract


  made of bundled nerve fibers that are expanded to certain distances along the spinal cord or the brain
• Epineurium 


  the outermost layer of connective tissue of a peripheral nerve, surrounding the entire nerve and containing its supplying blood vessels
• Perineurium


  connective tissue forming a sheath around a single bundle of nerve fibers
• Endoneurium


  the connective tissue layer surrounding a nerve fiber (neuron) including the neurolemma and the myelin sheath
• Sensory Neurons (Afferent Neurons) 


  transmit impulses to the spinal cord or to the brain
• Interneurons (Connector/Association Neurons)


  relay impulses or information from the sensory neurons to the motor neurons
• Motor Neurons (Efferent Neurons)


  transmit impulses from the brain or the spinal cord to the effector cell or muscles or glands throughout the body
• Nerve Impulses


  wave of chemical and electrical signal that is conducted along the membrane of a neuron
• Synapse


  small gap at the end of a neuron that allows a signal to pass from one neuron to the next
• Neurotransmitters


  "chemical messengers" that help facilitate the transfer of information across neurons
• Hormonal secretions of acetylcholine, melatonin, and serotonin enable the propagation of nerve impulses from the synapse.
• These secretions are released from the synaptic knobs once an electric impulse is released.
• Acetylcholine


  carries signals from motor neurons to the body's skeletal muscles
• Norepinephrine


  plays an important role on how our body responds to stress
• Dopamine


  related to muscle activity
• Serotonin


  plays a key role in such body functions as mood regulation, consciousness, and emotions
• Melatonin


  regulates sleep and wake cycles
• Reflex


  an automatic response to a change in the environment
• Reflex Arc

  sensory neuron - synapse - interneuron - motor neuron - muscle
• Reflex Arc


  a pathway that carry the nerve impulses for an automatic response
• Spinal Reflex


  does not involve the brain so you respond quickly