NERVOUS SYSTEM

• Neurons classification

  1. Sensory neurons carry signals from sense organs to the spinal cord and brain

  2. Interneurons connect sensory neurons and motor neurons

  3. Motor neurons carry impulses from the brain and spinal cord to the muscles and glands to produce an action
• Homeostasis is a process that keeps the stability of the internal environment
• Homeostasis is maintained and regulated by negative feedback mechanisms that minimize the deviation from the norm
• Nervous System coordination


  Regulates feedback mechanisms to maintain homeostasis
• Nervous System


  • Controls and coordinates function throughout the body
• Divisions of the Nervous System

  1. Central Nervous System consists of the brain and spinal cord, the body's neural control center

  2. Peripheral Nervous System coordinates with the nervous system
• The brain contains 100 billion neurons and consists of four parts: cerebrum
• Neurons

  • Use electrical signals called impulses to carry messages
• Positive feedback mechanisms exist but are rare. Instead of inhibiting, they promote the change that is occurring
• Nervous System function

  Means of communicating systems and sending information through sensors
• All organ systems are involved in homeostasis
• Neurons


  • Have a cell body containing a large, spherical nucleus and cytoplasmic organelles where metabolic activities take place
  • Dendrites are short and numerous, primary sites for receiving impulses
  • Axon or nerve fiber is long and thin, carries impulses away from the cell body
  • Some axons are enclosed with an insulating membrane called myelin sheath to increase the speed of impulse transmission
• Central Nervous System


  • Receives impulses, analyzes and organizes information, makes appropriate actions
  • The brain and spinal cord are delicate organs surrounded by bones for support and protection
  • Three layers of connective tissues called meninges surround the brain and spinal cord, each layer is surrounded by cerebrospinal fluid
• The brain contains 100 billion neurons
• Brain Stem


  • Stalk-like portion of the brain that joins the brain and the spinal cord
• Central Nervous System has three layers of connective tissues called meninges
• Cerebrum


  • Largest portion of the brain, performs higher brain functions like sensations, voluntary actions, problem solving, and planning
• Peripheral Nervous System is located outside the central nervous system and consists of all nerves and related cells not part of the brain and the spinal cord
• Cerebellum


  • Second largest part of the brain, located at the back of the skull, controls posture, balance, and coordination of skeletal muscles
• Reflex Arc defines the pathway by which a reflex travels – from the stimulus to sensory neuron to motor neuron to reflex muscle movement
• Heart rate is regulated by the autonomic nervous system, sympathetic system increases rate during exercise, parasympathetic system decreases rate after exercise
• Parts of the Brain

  • Cerebrum
  • Cerebellum
  • Thalamus
  • Hypothalamus
  • Brain Stem
• Cerebrum


  • Composed of two hemispheres divided by corpus callosum
• Thalamus and Hypothalamus

  • Small portions of the brain lying between the midbrain and brain stem, thalamus provides awareness of sensations and serves as a relay station for motor impulses, hypothalamus maintains homeostasis and recognizes emotions like anger, hunger, thirst, and fatigue
• Central Nervous System components

  • Brain
  • Spinal Cord
• Each layer of the meninges is surrounded by cerebrospinal fluid
• Spinal Cord descends from the medulla oblongata and is the main communication link between the brain and the body
• Autonomic Nervous System regulates involuntary activities without conscious control and is divided into sympathetic and parasympathetic systems with opposite effects on the organ
• Somatic Nervous System


  • Subdivision of the peripheral nervous system, regulates movements with conscious control like the skeletal muscles