SCIENCE TERM TEST

• the nervous system is constantly active
• hundreds of messages are being carried by special strings of cells called neurons or nerve cells
• neurons do not reproduce unlike other cells
• a neuron has a nucleus, axoplasm & organelles just like the rest of our body's cells.
• parts of a neuron: cell body

  largest part of the neuron
• parts of a neuron: nucleus


  located within the cell body and controls the activities of the cell
• parts of a neuron: dendrites


  receive & carry information towards the cell body (away from the previous neutron)
• parts of a neuron: myelin sheath

  covers the axon & speeds up the travel of nerve impulses
• parts of a neuron: axon

  carries nerve impulses away from the cell body (towards the next neuron)
• parts of a neuron: axon terminal


  passes on messages to the dendrites of other neurons
• types of neurons: sensory neuron (afferent neurons)


  • these receive the initial stimuli from receptors
  • sends information to the spinal cord then to the brain
  • this is the reason why sense organs are sensitive & respond to external stimuli
• types of neurons: interneuron (connector / association neurons)


  • reads the impulses sent from sensory neurons
  • found in the central nervous system
  • determines what response should be generated
  • if required, the interneuron passes the impulse on to the motor neurons
• types of neurons: motor neuron (efferent neuron)


  • transmits impulses from the brain & spinal cord to the effector cell / organ
  • they stimulate as an effector to generate the reaction for the stimulus
• responding to a stimulus:

  • a nerve impulse is a wave of chemical & electrical signals that is conducted along the membrane of a neuron.
  • however the neurons dont touch, there is a tiny gap between them called a synapse.
  • they "jump" from one neuron to another through neurotransmitters, these are chemical messengers stores in small sacs
  • a reflex is an automatic response to a change in the environment / stimulus
• divisions of the nervous system: central nervous system


  • command center of the entire body
  • processes information & sends instructions to the rest of the body
  • sends nerve impulses to the motor neurons of the peripheral nervous system
  • the brain is the main control center
  • the spinal cord is the link of the brain to the rest of the body
• divisions of the nervous system: brain


  • important & delicate organ that is protected & encased in the skull
  • the cerebrospinal fluid cushions it against impact
• the brain: cerebrum


  • 85% of the human brain
  • surface is called the cerebral cortex
  • learning, intelligence & judgement
  • voluntary actions
  • left hemisphere: logic
  • right hemisphere: arts
• the brain: cerebellum


  • located behind the brain stem
  • actions of the muscles
  • maintains balance
  • equilibrium, posture & coordination
• the brain: brain stem


  • connects spinal cord to the brain
  • coordinates breathing, sleeping, heartrate etc.
• the brain: brain stem, medulla oblongata


  controls involuntary movements
• the brain: brain stem, midbrain


  processes visual & auditory reflexes
• the brain: brain stem, pons


  controls respiratory functions
• the brain: brain stem, thalamus

  a relay station & disseminates information to the rest of the brain
• the brain: brain stem, hypothalamus


  • connects endocrine & nervous system
  • water content
  • temperature control
• the brain: spinal cord 


  • tubelike organ of neurons and blood vessels
  • inside the backbone covered by a protective membrane called meninges
• the peripheral nervous system


  • links the CNS to the rest of the body
  • made up of nerves which branch out to the rest of the body
• the somatic nervous system


  • mostly voluntary actions under your skeletal muscles
  • involuntary, spinal reflexes
• the autonomic nervous system


  
  

  • controls involuntary actions
• the autonomic nervous system: parasympathetic nervous system


  active under normal conditions
• the autonomic nervous system: sympathetic nervous system


  fight or flight response during stressful situations
• infections of the nervous system

  • encephalitis
  • meningitis
  • rabies
  • tetanus
• neurodivergent disorders 


  • epilepsy
  • alzheimer disease
  • parkinsons disease
• sense organs


  • sense is the ability to perceive stimuli
  • structures that carry messages about your surroundings to the CNS
• sense organs: general


  somatic senses

  • information about the environment

  visceral senses

  • information about internal organs
• sense organs: special


  • react to light, smells & chemicals
  • localized in specific parts of the body
• Geosphere


  • Solid part of the earth
  • Rocks
  • Minerals
  • Landforms
• layers of the earth

  • crust
  • mantle
  • core
• crust (lithosphere)


  • outermost layer of the earth
  • Thinnest layer (5-70 kilometers in thickness)
• continental crust


  Thicker layer (35 kilometers thick), found under the continents
• oceanic crust


  Thinner layer (7 kilometers thick), found under ocean basins