nervous system

• Nervous system


  Coordinates functions of body systems
• Nervous system


  • Divided into CNS and PNS
• Central nervous system (CNS)


  Brain and spinal cord
• Brain


  • Control center
  • Receives and processes sensory info
  • Inhibits responses
  • Stores memories
  • Generates thoughts and emotions
• Spinal cord


  • Connects brain to other nerves of the body
  • Conducts signals to and from the brain
  • Controls reflex activities
• Peripheral nervous system (PNS)


  • Nerves that branch out from brain and spinal cord to body parts
  • Divided into somatic and autonomic
• Somatic nervous system


  • Controls voluntary body movements
• Autonomic nervous system


  • Controls involuntary actions
• Neuron


  • Basic structural and functional unit
  • Transmits electrical signals called impulses across the system
  • Lets a body part respond accordingly
• Impulse or action potential


  • Sudden change of the cell membrane
• Dendrites


  • Projections that extend from the cell body
  • Receive chemical signals from axon terminals of another neuron
• Soma or cell body


  Contains nucleus and most organelles
• Axon


  • Projection from soma
  • Carries impulse to axon terminal
  • Enveloped by myelin sheath for faster conduction of impulse
• Myelin sheath


  Fatty white substance that surrounds axon, forming an electrically insulating layer
• Electrical disturbances in dendrites or axon causes a new wave of impulse
• Nervous system process


  1. Reception

  2. Integration

  3. Conduction

  4. Transmission
• Neurons connect through a synapse
• When an action potential reaches the axon terminal, a series of events will be created leading to the stimulation of the next neuron
• Neurotransmitters


  Chemicals released which facilitate the transmission of an impulse across a synapse
• Endocrine system


  • Mediates chemical coordination of body functions
  • Composed of ductless glands that release hormones
• Hormones


  Chemical messengers that affect targets of tissue or organ
• Feedback mechanism


  • Endocrine and nervous system coordinate with each other through a series of feedback mechanisms
  • A signal that initiates/accelerates or inhibits/slows down a process
• Endocrine glands


  • Pituitary gland
  • Thymus
  • Stomach
  • Small intestine
  • Kidneys
  • Heart

  
• Hypothalamus


  • Part of the brain responsible for producing hormones that help control cells and organs
  • Hormones govern physiologic functions such as temperature regulation, thirst, hunger, sleep, mood, sex drive, release of other hormones
• Pituitary gland


  Master gland
• Tropism


  • Biological mechanism
  • How plants respond to external stimuli
  • Enables plant to move toward (positive) or against (negative) the source of a stimulus
• Plant responses


  • All living things respond to environmental stimuli to survive
  • Plants are sessile (stationary) and exhibit responses to stimuli such as light, water, touch, wind
  • Responses are important to get nutrients, survive conditions, defend itself from predators, to reproduce
  • Plants release chemicals that act as defense mechanisms against pathogens and predators, warn nearby plants to prepare for an attack
• Plant responses


  • Mimosa pudica (sensitive plant) closes leaflets when touched
  • Sunflower moves toward the direction of the sun
  • Stomata close in response to rapid water loss
  • Seeds of some plants need to be burned to trigger germination
  • Roots grow underground to move to water sources and center of gravity
  • Leaves grow above ground to absorb light
• Plant growth patterns


  Tropisms are movements caused by a change in a plant's growth pattern
• Geotropism


  Gravity causes a response in a plant's growth
• Hydrotropism


  The way a plant grows or bends in response to water
• Thigmotropism


  Plants bend or grow because of touch (e.g. vines wrap around an arbor frame)
• Phototropism


  The way a plant grows or bends in response to light
• Plant hormones


  Chemical messengers that regulate biochemical and physiological responses such as seed germination, flowering, photosynthesis, fruit ripening, shoot and root development
• Stimulus


  Triggers a physiological change in an organism
• Response


  Reaction to a stimulus, a series that enables an organism to adapt and survive
• Sensory receptors


  • Photoreceptors (respond to light)
  • Mechanoreceptors (respond to physical stimuli)
  • Thermoreceptors (respond to temperature)
  • Chemoreceptors (detect chemicals)
  • Pain receptors (detect possible tissue damage)
• Types of eyes


  • Eye cups (in flatworms and invertebrates)
  • Compound eyes (in insects, arthropods)
  • Single lens eyes (in squid)
• Parts of the human eye

  • Sclera (outermost layer, white part)
  • Transparent cornea (in front of sclera)
  • Conjunctiva (lines eyelids and front of eyeball, keeps eyes moist)
  • Choroid (surrounded by sclera)
  • Iris (eye color, formed from choroid)
  • Retina (transparent lens that focuses images, contains photoreceptor cells)
• Photoreceptor cells


  • Transduce light energy into action potentials
  • Nerve impulses travel along optic nerve to visual areas of the brain
  • Rod cells use rhodopsin for night vision and detect shades of gray
  • Cone cells distinguish colors and are sensitive to bright light