Bio

• Importance of homeostasis in the body:

  • Neurons keep the body in a state of balance for growth, development, reproduction, and survival
• Nervous and endocrine systems allow communication among different organs
• Nervous system functions:

  • Center of all mental activities: learning, memory, thinking, and speech
  • Receives, examines, and processes data and initiates appropriate responses
  • Controls and regulates all activities within the human body
  • Coordinates the functions of all other organs in the body
  • Regulates and maintains homeostasis
  • Keeps us in touch with the external environment
• Stimuli:

  • Any internal or external changes that cause a response
  • Responses to stimuli are either voluntary or involuntary
• Homeostasis:

  • Body's ability to maintain constant internal equilibrium
  • Nervous and endocrine systems are the main mechanisms by which homeostasis is sustained in the body
• Neurons:

  • Basic cellular units of structure and function of the nervous system
  • Transmit impulses to and from various parts of the nervous system
  • Carry information through the body in the form of nerve impulse
  • Once damaged, neurons cannot be replaced
• Parts of a Neuron:

  • Cell body:
  • Core section of the neuron
  • Contains genetic information, maintains the neuron's structure, and provides energy to drive activities
  • Dendrites:
  • Shorter extensions of the cell body
  • Receive and carry information toward the cell body
  • Axon:
  • Carries nerve impulses away from the cell body
  • Neuron lacking a Nissl body
  • 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 that facilitate the rapid conduction of nerve impulses
  • Schwann cells:
  • Produce the myelin sheath
• Types of Neurons:

  • Sensory neurons (afferent neurons):
  • Receive initial stimuli from receptors
  • Transmit impulses to the spinal cord or to the brain
  • Interneurons (connector/association neurons):
  • Relay impulses or information from sensory neurons to motor neurons
  • Motor neurons (efferent neurons):
  • Transmit impulses from the brain or the spinal cord to effector cells or muscles or glands throughout the body
• Transmission of Nerve Impulses:

  • Nerve impulses:
  • Wave of chemical and electrical signal conducted along the membrane of a neuron
  • Transmitted from one neuron to another through a synapse
  • 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
  • Electrical impulses travel along the axon of a neuron and trigger the release of neurotransmitter molecules at the synapse
• Reflex:

  • Automatic response to a change in the environment
  • Reflex arc:
  • Pathway that carries nerve impulses for an automatic response
  • Spinal reflex:
  • Does not involve the brain, allowing for a quick response