GR10

• The nervous system is the body's processing system, contact with the outside world, control center, and communication network
• Functions of the nervous system include movement, response to environmental stimuli, intelligence, self-awareness, thought, and emotion
• The nervous system is composed of nerve cells called neurons
• The Central Nervous System consists of the brain and spinal cord, serving as the body's control center
• Neurons transmit impulses to the brain in the Central Nervous System
• The brain has parts for movement, sensing, consciousness, and involuntary functions
• The average weight of the brain is 1.35kg
• The brain is mainly composed of neurons
• Cerebellum:

  • Located below the cerebrum, controls posture, balance, and coordination
  • Divided into left and right hemispheres, connected by the vermis
  • Regulates skeletal muscle movement
• Cerebrum:

  • Largest, most developed part of the brain
  • Consciousness, intellect, learning, memory, and sensations reside here
  • Cortex (gray matter) outer layer, cerebral cortex (white matter) inner layer
  • Complex part of the brain
• Brainstem:

  • Diencephalon
  • Thalamus: Receives sensory input from all over the body and directs it to the cerebrum
  • Acts as a central relay station for sensory impulses from the spinal cord and other brain regions
  • Routes sensory information (excluding smell) to the cortex for interpretation
  • Connected to different brain areas and involved in the reticular activating system (RAS), prioritizing stimuli for immediate attention
  • Hypothalamus: Key regulator of homeostasis
  • Centers for hunger, sleep, thirst, temperature, and more
  • Controls the pituitary gland, linking nervous and endocrine systems
  • Influences sexual response, fight-or-flight, pleasure, and emotions
• Midbrain:

  • Located below the cerebrum
  • Handles eye and auditory reflexes
• Pons:

  • Links medulla and cerebrum
  • Contains motor pathways between the cerebral cortex and cerebral hemisphere
  • Regulates sensory info, facial expressions
  • Damage may cause paralysis
• Medulla Oblongata/Spinal Bulb:

  • Extends from central brain to spinal cord
  • Manages vital functions: heart rate, breathing, digestion
  • Can sustain life without cerebrum and cerebellum
• Corpus Callosum:

  • Links the brain's two hemispheres
  • Facilitates communication between the two cerebral hemispheres
• Frontal Lobe:

  • Located at the front of the head
  • Controls voluntary movement, thinking, feeling
• Parietal Lobe:

  • Located at the top rear of the head
  • Primary somatosensory area for skin sensation
• Occipital Lobe:

  • Located at the back of the head
  • Visual cortex for vision
• Temporal Lobe:

  • Located on each side of the head
  • Auditory cortex for hearing and speech
• The spinal cord is referred to as the Nervous System’s “Superhighway” and contains a Central canal with cerebrospinal fluid
• Gray matter in the spinal cord consists of cell bodies of neurons, short fibers, sensory and motor neurons
• White matter in the spinal cord comprises long fibers of interneurons, organized in bundles called tracts
• Afferent tracts in the spinal cord carry information to the brain, while efferent tracts carry information down from the brain
• Cervical spinal nerves: 8 pairs that emerge from the cervical spine in the neck
• Thoracic spinal nerves: 12 pairs that emerge from the thoracic spine in the chest
• Lumbar spinal nerves: 5 pairs that emerge from the lumbar spine in the lower back region
• Sacral spinal nerves: 5 pairs that emerge from the sacrum, the bony plate at the base of the column
• Coccygeal spinal nerves: 1 pair that emerge from the coccygeal bone or the tailbone
• Reflex is an involuntary reaction to a stimulus, and a reflex arc is the pathway causing the reflex
• Neurons are the basic units of the nervous system, responsible for processing and signaling information
• There are billions of neurons in the body, some existing alone while others form organs like the brain and spinal cord
• In one part of the brain alone there are 12-14 billion neurons
• Neurons relay and receive messages (impulses) between the brain and body, as well as within the brain and spinal cord
• Types of Neurons:

  • Motor Neurons: Brain to muscles, glands, or other neurons
  • Sensory Neurons: Receptors to Central Nervous System
  • Interneurons: Between motor and sensory neurons, in brain and spinal cord
• Parts of Neurons:

  1. Dendrites:

  • Carry impulses towards the cell body
  • Up to 200 dendrites increase surface area
  • Treelike extensions receive information from other neurons
  • Transmit electrical stimulation to the soma
  • Covered with synapses, some dendrites reach one meter in length

  2. Soma:

  • Cell Body (Soma): signals from the dendrites are joined and passed on, maintaining the cell and keeping the neuron functional

  3. Axon:

  • Carry impulses away from the cell body
  • Pass impulses to the dendrites of other neurons or cell body of muscle cells
  • Can be grouped together into a combination of an electrical charge and a chemical reaction, moving along a neuron in bee-like bundles called nerves
• Nerve Impulse:

  • Combination of an electrical charge and chemical reaction
  • Not a flow of electricity, but an electrochemical signal moving along a neuron
  • Cannot jump from one neuron to another
• Neurotransmitter:

  • Transmits nerve impulses across synapses between neurons
• Stimulus refers to any factor in the environment that may trigger a nerve impulse
• Stimulus is received by the body and a response is made
• Response is a reaction to a stimulus