B3

• Menstrual cycle


  Around 28 days
• Stage 1 - Menstruation

  1. Bleeding

  2. Break down of uterus lining

  3. Day 0-4
• Stage 2


  1. Building up of uterus lining

  2. prepare uterus lining for fertilised egg

  3. day 4-14
• Stage 3 - Ovulation


  Release of egg

  > one day
• Stage 4


  1. Maintaining lining of uterus

  2. to day 28
• Follicle stimulating hormone (FSH)


  Produced in pituitary gland, stimulates eggs to mature
• Luteinizing hormone (LH)


  Produced in pituitary gland, stimulates release of egg
• Estrogen


  Produced in ovaries

  stimulates growth of uterus lining
• Progesterone


  Produced in ovaries, maintains lining of uterus
• Negative feedback (Menstrual cycle)

  > FSH stimulates ovaries to produce Oestrogen

  > As Oestrogen levels increase, it inhibits (stops) FSH

  > When Oestrogen levels get high it stimulates LH, which causes ovulation

  > Progesterone inhibits LH + FSH
• Neurones


  Nerve cells
• Neurones


  • Goes to all parts of body
  • Carries electrical impulses
• Central nervous system


  • Coordinates a response
  • Consists of the brain and spinal cord
• Stimulus detection and response


  1. Stimulus detected by receptors

  2. Electrical impulses along sensory neurones

  3. To the CNS (brain and spinal cord)

  4. Impulses travel through CNS via relay neurones

  5. CNS sends information to an effector (muscle or gland) along a motor neurone

  6. Effector responds
• Sensory neurones


  Carry electrical impulses from receptor cells to CNS
• Motor neurones


  Carry electrical impulses from CNS to effectors
• Relay neurones


  Carry electrical impulses from sensory to motor neurones
• Electrical impulse travel


  • Along long axon so can travel long distances
  • Dendrites to connect to other neurones
• Motor neurone axons


  • Have fatty (myelin) sheath that acts as an electrical insulator to speed up electrical impulses
• Structure of sensory neurone


  • Receptor cells
  • Long dendron
  • Cell body
  • Short axon
  • Dendrites to CNS
• Structure of motor neurone


  • CNS connected by dendrites
  • Long axon with myelin sheath
  • Dendrites to effector cells
• Synapse


  • Connection between two neurones
  • Neurotransmitters are released
  • They diffuse across synaptic cleft
  • Chemicals bond with receptor molecules on the postsynaptic
• Reflex arc


  • Automatic response
  • Quicker than normal response
  • Conscious brain not involved
  • Sensory neurone connects to relay neurone in the spinal cord or unconscious part of brain
  • Links directly to motor neurone
• Brain

  • responsible of all important decision making
• Cerebrum (Cerebral cortex)

  • wrinkly
  • Split in two hemisphere's
  • Controls: Consciousness, Intelligence, Memory, Language
  • Interpreting senses
• Cerebellum

  • located in the back of the brain
  • controls: balance and movement
• Hypothalamus

  • Involved in thermal regulation
  • Sends hormones to the pituitary gland
• Medulla

  • located by spinal chord
  • Controls unconscious actions: Breathing
• Pituitary gland

  • a gland
  • Produces important hormones
• How scientists study the brain

  • case studies- on patients who have suffered brain damage
  • Stroke survivors- see the effected area and its consequence
  • MRI and PET scans to see underlying activity
  • CT scans to identify effected area
  • Electrically stimulated- via the use of an electrode
• Risks of treating the brain

  • Things can go wrong to the brain: Tumours, Trauma, infection, Mental health
  • Fragile brain tissue surrounding- difficult ti fix anything as it could lead to brain damage
  • Don't fully understand the complex brain
• Cornea

  • transparent
  • allows light to pass through
  • refracts light
  • Oxygen is diffused into the cornea rather by the blood stream
  • no blood vessels
• Iris

  • Coloured part of eye
  • Controls how much light passes through
• Iris reflex

  • Light intensity of light can damage retina
  • Constricted- Smaller at bight light
  • Dilated- Bigger at low light
  • Circular muscle on inside
  • Radial muscle on the outside
• lens

  • reflects light to focus on retina
  • Can change shape
• Retina

  • light sensitive part covered In receptors
• Cone cells

  • sensitive to colour of light
  • Allows to see in colour
  • don't work well in low lighting
• Rod cells

  • more sensitive to light
  • See in black and white
• Fovea

  • filled with only con receptors
  • Central region to focus light on
  • Special spot in retina
• Optic nerve

  • sends electrical impulses to the brain generated by the receptor cells