Nervous System

• Nervous system


  A complex network of specialized cells called neurons that coordinate and regulate the activities of the body
• Functions of the Nervous System

  • Coordinating physical movement of the body
  • Responding to the action of all the senses; hearing, sight, smell, taste, and touch
• Nerve cells or Neurons

  • A single long fiber (axon)
  • Several branched threads (dendrites)
• Dendrites


  Receive messages from other nerves or organs
• Electrical impulse


  1. Passes along the axon

  2. Conducted (passed on) to another dendrite or to an effector organ

  3. Stimulates the effector organ to move or react
• Synapse


  The space between the axon terminals of one neuron and subsequent dendrites of the next neuron
• Impulse transmission


  1. Travels along a series of neurons and synapses

  2. Some impulses are sent directly to an effector organ
• Nerves


  • Occur as single neurons or in bundles, called nerve trunks
  • Ganglions are the nerve bundles that occur outside of the brain and spinal cord
• Types of nerves


  • Sensory or afferent neurons (receive stimuli and carry them to the central nervous system)
  • Motor or efferent neurons (carry messages from the brain to muscles or glands)
• Major parts of the brain

  • Cerebrum
  • Cerebellum
  • Pons
  • Medulla oblongata
• Cerebrum


  • The largest part of the brain
  • Divided into two hemispheres (left and right) by a deep groove called the longitudinal fissure
  • Responsible for higher cognitive functions such as thinking, reasoning, memory, perception, and voluntary motor control
  • The outer layer, called the cerebral cortex, is highly folded and convoluted, increasing its surface area and allowing for complex processing
  • Further divided into lobes, including the frontal, parietal, temporal, and occipital lobes, each with specific functions
• Cerebellum


  • Located beneath the cerebrum, at the back of the brain
  • Plays a vital role in coordinating voluntary movements, balance, posture, and motor learning
  • Contains more neurons than any other part of the brain
• Brainstem


  • Located at the base of the skull, connecting the cerebrum and cerebellum with the spinal cord
  • Consists of the midbrain, pons, and medulla oblongata
  • Controls many basic life-sustaining functions such as heartbeat, breathing, blood pressure, and consciousness
• Pons


  • Serves as a bridge between different parts of the brain
  • Transmits signals between the cerebrum, cerebellum, and spinal cord
  • Plays a role in regulating breathing, sleep, and facial movements
• Medulla Oblongata


  • Located at the lowest part of the brainstem, adjacent to the spinal cord
  • Regulates vital functions such as heartbeat, breathing, digestion, and blood pressure
  • Contains vital centers that control involuntary processes, including the cardiovascular and respiratory centers
• The cerebrum is the largest part of the brain
• Cerebrum


  Responsible for the decision-making or thinking processes that control voluntary muscle activity and for reactions to stimuli that are processed by the senses
• Lobes of the cerebrum

  • Frontal
  • Parietal
  • Temporal
  • Occipital
• Frontal Lobe


  • Located at the front of the brain, behind the forehead
  • Responsible for higher cognitive functions such as reasoning, planning, decision-making, and problem-solving
  • Also involved in voluntary movement, motor skills, speech production (Broca's area), and personality
• Parietal Lobe


  • Located at the top and back of the brain, behind the frontal lobe
  • Responsible for processing sensory information from the body, including touch, temperature, pain, and proprioception (awareness of body position)
  • Also involved in spatial perception, attention, and integrating sensory information with motor responses
• Temporal Lobe


  • Located on the sides of the brain, near the temples
  • Responsible for processing auditory information (hearing) and language comprehension
  • Contains the primary auditory cortex and areas involved in memory formation, emotion regulation, and visual recognition (such as faces)
• Occipital Lobe


  • Located at the back of the brain, behind the parietal and temporal lobes
  • Primary function is visual processing, including interpreting visual stimuli received from the eyes
  • Contains the primary visual cortex, where visual information is initially processed, as well as areas involved in perceiving motion, color, and depth
• The right hemisphere processes creative and emotional stimuli, while the left hemisphere processes actions and is involved in learning
• The right side of the brain controls the left side of the body, and the left side controls the right
• Spinal Cord


  • Located at the center of the vertebral column
  • The main avenue for message transferal between the brain and the other parts of the body
• Spinal Cord


  1. Divided into segments

  2. A pair of spinal nerves extends to the body from each part

  3. Receives messages from sensory nerve fibers in various parts of the body and transmits them to the brain

  4. Motor nerve fibers in the spinal cord then transmit the response from the brain back to the body
• Central Nervous System (CNS)

  • Consists of the brain and the spinal cord
  • The brain is the command center of the nervous system and controls most functions of the body
  • The spinal cord serves as a pathway for transmitting information between the brain and the rest of the body, and also coordinates reflexes
• Peripheral Nervous System (PNS)


  • Consists of all the nerves outside the CNS
  • Further divided into the somatic nervous system (controls voluntary movements and transmits sensory information) and the autonomic nervous system (regulates involuntary processes)
• Neurons


  • The basic functional units of the nervous system
  • Transmit electrical signals called nerve impulses or action potentials
  • Consist of three main parts: the cell body (soma), dendrites, and axon
  • Dendrites receive signals from other neurons and transmit them to the cell body
  • The axon carries signals away from the cell body to other neurons, muscles, or glands
  • The point of communication between neurons is called a synapse, where neurotransmitters transmit signals from one neuron to another
• Supporting Cells (Glial Cells)

  • Provide structural support, insulation, and nourishment for neurons
  • Examples include astrocytes, oligodendrocytes, and Schwann cells
• The nervous system plays a crucial role in controlling and coordinating all bodily functions, including sensory perception, movement, cognition, and homeostasis
• The nervous system allows organisms to interact with their environment and adapt to changes in their surroundings