Response

• What are neurones?


  Elongated, branched cells specialised for the conduction of impulses
• What are gilial cells?


  Support neurones

  Provide nutrients

  Control composition of fluid
• What does the somatic nervous system do?


  Carries nervous impulses to skeletal muscles, under conscious control
• What does the autonomic nervous system do?

  Carries nervous impulses to glands, muscles under subconscious control
• What does autonomic reflexes include?


  Involve activation of smoother and cardiac muscles and glands

  Regulate bodily function such as digestion, blood pressure, salivation
• What is a mechanoreceptor stimulated by and its role in the body?


  Stimulated by forces, stretching, compressing or moving sensor.

  Role in body: Balance, touch, hearing
• What is a chemoreceptor stimulated by and its role in the body?


  Stimulater by chemicals.

  Role is: Taste, smell, regulation of chemicals in blood
• What is a thermoreceptor stimulated by and its role in the body?


  Thermoregulation, awareness of environmental temperature
• What is a photoreceptor stimulated by and its role in the body?


  Stimulated by light

  Role: sight
• What is the electrical name of receptors?


  Transducers
• Example of mechanoreceptor


  Pacinian corpuscle
• What happens when pressure is against lamellae?

  • Deformation occurs
  • Causes stretching of plasma membrane
  • Causes opening of stretch-mediated sodium ion channels in membrane of sensory neurone ending
  • Influx of sodium ions into sensory neurone
  • Causes depolarisation
  • Creation of generator potential, leads to action potential
• During the resting potential of a neurone what are the relative charges?


  Inside: negative Outside: positive
• What is a transducer?


  Converts one form of energy into electrical energy e.g receptor
• What type of receptor is the eye?

  Photoreceptor
• What type of receptor is the heart?


  Chemoreceptor, Baroreceptor
• What is visual acuity?


  The sharpness of images
• What is a nerve?


  Combination of several neurones
• What is summation?


  Adding together the signals from 3 rod cells
• What is retinal convergence?


  The joining of 3 rod cells to produce only one neurone
• What takes place at the bipolar cell?


  Where generator potential begins and becomes an action potential
• What do sensory neurons do? (eyes)


  Collect information from the bipolar cells and convey it to the brain via the optic nerve
• What type of photoreceptor has a low visual acuity?


  Rod cells
• Why do cone cells have high visual acuity?


  Photoreceptor cells called cone cells have high visual acuity because they are responsible for color vision and are concentrated in the fovea, the central part of the retina where visual acuity is highest.
• Why do rod cells have low visual acuity?


  Retinal convergence into one bipolar neurone
• What light intensity do rod and cone cells need?


  Cone cells: High light conditions

  Rod cells: Low light conditions
• How do ROD and CONE cells act as transducers?


  They convert light energy into electrical energy via the breakdown of pigment in the photoreceptors
• Explain the sequence of impulses from rod cell to brain?

  • Light hits rod cell
  • Breakdown of pigment
  • Generator potential created
  • Retinal convergence
  • Summation
  • Bipolar neurones
  • optic nerve
  • Brain
• What pigment do rod cells contain?

  Rhodopsin
• Where are cone cells found most ?


  Fovea
• What are the 3 types of cone cells?


  Red

  Green

  Blue
• How do different types of cone cells vary?


  Each cone type absorbs a different wavelength of light

  E>g people who are colour blind may be missing one of the types of cone cells
• Why are there only 3 types of cone cells?


  If you have all 3 types of cone cells you can detect all wavelengths of light, because of overlapping of cones absorbing different wavelengths.

  TRICHROMATIC THEORY OF COLOUR VISION
• What pigment do cone cells contain?


  Iodopsin
• Why do rods have a low visual acuity?


  Signal is basically an average of all 3 rods so no individual detail from each cell.

  So 2 different sources cannot be distinguished
• How are rods and cone cells sensitive to light?


  Rod cells are more sensitive to light
• What is SAN known as?


  Natural pacemaker
• Describe how the action of the heart is initiated and co-ordinated?

  • SAN initiates a wave of excitation (electrical activity)
  • Wave of excitation is conducted across both atria
  • Waves are conducted downwards
  • Band of non-conducting tissue stops electrical activity passing into the ventricles straight away
  • Wave of excitation is collected at AVN
  • AVN conducts wave to base of ventricle by bundle of HIS
  • Electrical activity moves up ventricular walls via purkyne tissue
• What does myogenic mean?

  Contracts independently
• How is heart rate controlled?


  By brain in response to environment, receptors and stimuli