LESSON 8: NERVOUS SYSTEM

• Nervous System


  System responsible for coordinating the functions of the other body systems and enabling the body to respond quickly to changes in the environment
• Nervous System


  • Gathers information from outside and inside the body
  • Transmits and processes information
  • Elicits the best responses to the stimulus
  • Allows rapid communication of the different organs
• Main divisions of the Nervous System

  • Central Nervous System (CNS)
  • Peripheral Nervous System (PNS)
• Central Nervous System (CNS)


  Brain - main control center where it processes information and controls responses

  Spinal cord - connects the brain to other nerves of the body
• Peripheral Nervous System (PNS)

  Autonomic system - involuntary control of internal organs, blood vessels, and smooth and cardiac muscles

  Sympathetic Division - fight or flight response

  Parasympathetic Division - rest and digest

  Somatic Nervous System - voluntary control of our movements via skeletal muscle
• Components of the Nervous System

  • Central Nervous System (CNS)

  Peripheral Nervous System (PNS)
• Central Nervous System (CNS)


  Brain - receives and processes sensory information, initiates responses, stores memories, generates thoughts and emotions

  Spinal cord - conducts signals to and from the brain, controls reflex activities
• Peripheral Nervous System (PNS)

  Motor Neurons - CNS to muscles and glands

  Sensory Neurons - Sensory organs to CNS
• Divisions of the Nervous System

  • Somatic Nervous System - controls voluntary movements

  Autonomic Nervous System - controls involuntary responses
• Divisions of the Autonomic Nervous System

  • Sympathetic Division - "Fight or Flight"

  Parasympathetic Division - "Rest or Digest"
• Nervous Control


  Responsible for transmitting signals between different parts of the body

  Operates through electrical impulses transmitted along nerve fibers

  Crucial for activities such as movement, sensation, and cognition
• Neuron


  Connects with one another through a junction called synapse

  Transmits electrical signals called an action potential or an impulse across the system and lets a body part respond accordingly whenever it is being stimulated
• Parts of a Neuron

  • Cell Body or Soma - contains the nucleus and most organelles

  Axon - carries the impulse to the axon terminal

  Dendrites - receive chemical signals from the axon terminals of another neuron

  Myelin Sheath - insulates the axon to help protect the neuron cell and speed up impulse conduction
• Types of Neurons


  • Sensory Neurons - detect major senses such as touch and pain

  Motor Neurons - coordinate our muscles and ensure that our arms and legs move together

  Interneurons - relay information from sensory neurons to motor neurons
• Chemical Control


  Involves the use of hormones, which are chemical messengers produced by various glands in the endocrine system

  Hormones are released into the bloodstream and travel to target cells or organs, where they exert their effects by binding to specific receptors

  Chemical control tends to act more slowly than nervous control but often has longer-lasting effects

  Chemical control usually occurs on an unconscious level
• Endocrine System


  Responsible for the chemical coordination of body functions

  Composed of ductless glands that release hormones

  Hormones are chemical messengers that affect specific target tissues or organs

  Plays a crucial role in maintaining the homeostasis of the body system
• Similarities between Nervous and Chemical Control

  • Both govern the body's physiological activities

  Help the body maintain its internal equilibrium, or homeostasis

  Require communication between various sections of the body

  Respond to both internal and external stimuli

  Allow organisms to adapt to their surroundings

  Collaborate to manage complicated physiological reactions
• Differences between Nervous and Chemical Control

  • Nervous Control - Electrical signals through neurons, targets specific organs/tissues/cells, short-lived responses, some actions can be consciously controlled

  Chemical Control - Chemical signals (hormones) through bloodstream, targets widespread areas of the body, long-lasting responses, involuntary and automatic actions
• Plants do not have a nervous system but can sense changes in their environment and respond to them
• Plant Hormones


  • Auxin - control cell elongation in stems and leaves, root response to gravity

  Gibberellins - responsible for shoot elongation, seed germination, fruit and flower maturation

  Cytokinins - responsible for the regulation of cell division

  Ethylene - responsible for promoting fruit ripening, flower wilting, and leaf fall

  Abscisic Acid - primary hormone for stress response and stomatal closure
• Plant Responses


  • Phototropism - movement of plant parts toward or away from a light source

  Seed Germination - lightsensitive proteins signal the production of the enzyme amylase that breaks down the starch in the seed to produce simple sugars

  Thigmotropism - Directional response to touch

  Gravitropism - Directional growth in response to gravity