Nervous System Structures and Processes

• 2 parts of the nervous system

  central nervous system (CNS) and peripheral nervous system (PNS)

  
• Parts of central nervous system


  brain and spinal cord

  
• parts of peripheral nervous system

  sensory (afferent) and motor (efferent) neurons

  
• sensory (afferent) neurons


  neurons that receive information from sensory receptors from the environment to the CNS

  
• motor (efferent) neurons


  neurons that carry impulses/information from CNS to muscles, organs, and glands (movement)

  
• Types of motor neurons

  somatic and autonomic

  
• somatic nervous system


  the division of the peripheral nervous system that controls the body's voluntary movement

  
• autonomic nervous system


  The part of the PNS that controls the muscles of the internal organs and involuntary movement

  
• Types of Autonomic Nervous System

  sympathetic nervous system and parasympathetic nervous system

  
• sympathetic nervous system

  a set of nerves that prepares the body for action in challenging or threatening situations, responsible for fight or flight (e.g. releasing adrenaline, increased heart and breathing rate)

  
• parasympathetic nervous system


  a set of nerves that helps the body return to a normal resting state (e.g. decreasing heart and breathing rate, decreasing adrenaline production to maintain homeostasis)

  
• two types of cells in the nervous system

  neurons and glial cells

  
• neuron


  nerve cells which pass and receive signals

  
• nerve


  message pathway of the nervous system
• dendrites


  Branchlike parts of a neuron that receive information from other neurons or sensory receptors and relay the impulse to the cell body

  
• cell body (soma)


  the site of the neuron containing the nucleus, site of neuron's metabolism and processes the input from dendrites

  
• axon


  an extension of a neuron that carries nerve impulses

  
• axon terminal


  the end of an axon that send the impulse and communicate with the dendrites of another neurons

  
• Schwann cells


  Supporting cells of the peripheral nervous system responsible for the formation of myelin

  
• synapse


  A gap between neurons where information is transmitted from one neuron to the next, or between a neuron and an effector

  
• myelin sheath


  a fatty insulating layer composed of Schwann cells to protect neurons and speed transmission rate

  
• multiple sclerosis

  when the myelin sheath degrades, so impulses are slower and the body can paralyze or become numb due to the lack of fast impulses

  
• types of neuron structures

  unipolar, bipolar, multipolar

  
• multipolar neuron


  a neuron with one axon and many dendrites attached to its soma, can interact with multiple neurons and found in the CNS

  
• bipolar neuron


  a neuron with one axon and one dendrite attached to its soma, found in the inner ear, retina, and olfactory area of the brain (hearing, sight, and smell)

  
• unipolar neuron


  a neuron with one process extending from its cell body, axon and dendrite are fused (dendrites are not on soma), found in the peripheral nervous system

  
• types of neurons (based on functions)

  sensory (afferent) neurons, motor (efferent) neurons, interneurons

  
• interneurons


  neurons within the brain and spinal cord that communicate internally and intervene between the sensory inputs and motor outputs

  
• reflex arc

  the connection of the afferent neurons to the interneurons to the efferent neurons, resulting in a reflex action in response to stimuli

  
• withdrawal reflex


  a spinal cord reflex intended to protect the body from damaging stimuli

  
• example of a withdrawal reflex

  touching a cactus, pain receptors feel pain and afferent neurons send the signal to the spinal cord, then the spinal cord interneurons send a signal to efferent neurons to move away from the cactus

  
• neurotransmitters


  chemicals that carry a signal from one neuron to another or an effector

  
• step 1 of signal transmission

  impulse travels to the synaptic terminal

  
• step 2 of signal transmission

  the synaptic vesicles move towards and fuse with the presynaptic membrane to release neurotransmitters.

  
• step 3 of signal transmission

  the neurotransmitters are released into the synaptic cleft

  
• step 4 of signal transmission

  neurotransmitters bind to receptor proteins and impact the postsynaptic neuron. enzyme breaks down the neurotransmitter and the components are reabsorbed by the presynaptic neuron

  
• 4 types of neurotransmitters

  dopamine, serotonin, endorphins, norepinepherine
• dopamine functions

  affects brain synapses in the control of body movements; linked to sensations of pleasure (e.g. eating)

  
• effects of abnormal dopamine production

  exessive production: leads to schizophrenia (reality perception is distorted), inadequate production: leads to parkinson's disease (destroys neurons causing tremors, slurred speech, and coordination problems)
• serotonin functions

  regulates temperature and sensory perception; involved in mood control