science f3 chap1

• The human nervous system


  The control system in the human body
• Parts of the nervous system

  • Central nervous system
  • Peripheral nervous system
• Pathway of the human nervous system

  1. Stimuli

  2. Sensory organs/receptors

  3. Nerve impulses

  4. The brain

  5. Nerve impulses

  6. Effector

  7. Respond
• Voluntary actions

  • Communication
  • Thinking
  • Eating
• Involuntary actions

  Actions that occur automatically, that is are unnoticed and cannot be controlled according to one's will
• Involuntary actions

  • Breathing
  • Digestion
  • Eye reflex
• Stimulus


  Something that causes a reaction or response
• Response


  A reaction to a stimulus
• Human sensory organs


  • Skin (touch)
  • Nose (smell)
  • Tongue (taste)
  • Ears (hearing)
  • Eyes (sight)
• Eyes


  • Focusing on objects near and far
  • Produces continuous images that are sent directly to the brain
  • As a sense of sight
• Structure of eyes


  • The function of each eye structure
• Mechanism of vision


  1. Light from an object enters the eye through the pupil

  2. Light is refracted by the cornea, aqueous humor, eye lens, and vitreous humor

  3. Inverted and small images are formed on the retina

  4. The retina produces nerve impulses and the optic nerve transmits them to the brain

  5. The brain translates impulses and produces upright images
• Ears


  • To keep our balance and hearing
  • As a sense of smell
• Structure of ears


  • The function of each ear structure
• Mechanism of hearing


  1. Sound waves enter the ear canal

  2. The eardrum receives sound waves and vibrates

  3. The vibrations are amplified by the ossicle bone and transmitted to the oval window

  4. The oval window vibrated

  5. The cochlea converts vibrations into impulses

  6. Impulses are carried by the auditory nerve to the brain

  7. The brain interprets it as sound
• Nose


  • Provides air for breathing
  • Filters and cleans foreign debris during respiration
  • As a sense of smell
• Tongue


  • As a digestive organ with ease of movement of food during chewing and swallowing
  • As a sense of taste
• Plant Stimulus and Response

  Plants respond to touch, water, light, and gravity which are divided into two, namely the tropism response and the nastic response
• Structure and mechanism of the tongue

  • The surface of the tongue is covered by taste buds that contain many taste receptors and are scattered on the surface of the tongue
  • Taste receptors are sensitive to chemicals in food
  • The tongue has 5 types of taste receptors, namely sweet, sour, bitter, and umami (savory taste)
• Skin


  • Protect us from microbes
  • Allows sensations of touch, temperature, and pressure
  • As a sense of touch
• Types of tropism and reactions

  • Phototropism - Growth of plant parts towards the light
  • Geotropism - Growth of plant parts towards gravity
  • Hydrotropism - Growth of plant parts towards the water
  • Tigmotropism - The movement of plant growth against touch or when in contact with an object
• Phototropism


  • The growth of sunflower shoots in the direction of sunlight
• Geotropism


  • Root growth of red chili tree according to the direction of gravity
• The concentration of the skin depends on the number of receptors present and the thickness of the epidermis
• Hydrotropism


  • Growth of pandan tree roots in the direction of water
• Tigmotropism


  • Cucumbers have suckers that twist an object that touches them
• The more receptors, the more sensitive that part of the skin is
• Nastic response


  Plants respond to touch, light, and heat. The direction of the response does not depend on the direction of the stimulus
• The thinner the epidermis, the more sensitive the skin is to stimuli
• Nastic response


  • The leaves of a semalu tree (Mimosa pudica) are covered when touched
• Very sensitive parts of the skin

  • Fingertips, back of neck, lips, and earlobes
• Importance of each response

  • Phototropism - Helps shoots get sunlight for photosynthesis
  • Geotropism - Helps the roots penetrate the soil to obtain water and the roots can grip the soil firmly
  • Hydrotropism - Helps plant roots absorb water and mineral salts from the soil
  • Tigmotropism - Helps plants reach the highest position to get sunlight and maintain an upright position
  • Nastic movement - Protects leaves from injury
• Parts of the skin that are less sensitive

  • Elbows and knees
• The sensory organs are interconnected with each other and can balance the human body on a single daily basis
• Sensory limitations


  • Limits our sensory ability to detect a stimulus
  • Caused by sensory organ defects or the aging process
• Visual sensory limitations


  • The eye cannot detect an image that falls on a blind spot
  • Human vision can also be affected due to farsightedness, nearsightedness, astigmatism, and presbyopia
• Near sightedness

  • Cannot see near objects clearly because light from the object focuses behind the retina
  • Requires a convex lens
• Astigmatism


  • Images are blurred and unclear because light from objects is separated and focused at different points on the retina
  • Requires a cylindrical lens or undergoes surgery
• Hearing sensory limitations


  • Humans can only hear between 20Hz to 20,000Hz
  • Deafness is caused by the ossicle bones joining together due to infection, the aging process or exposure to loud noise for a long period of time
  • Only surgery or hearing aids can help deaf people
• Technology to enhance the ability of sensory organs

  • Magnifying glass & microscope can see art/small objects
  • Binoculars & telescopes can see distant objects
  • Stethoscope amplifies the sound of the heartbeat
  • Loudspeaker amplifies the sound