Topic 2- control of animals

• IPMAT - Interphase, Prophase, Metaphase, Anaphase, Telophase.
• Mitosis - results in two genetically identical daughter cells, each with identical sets of chromosomes in the nucleus to the parent cell. This results in the formation of two genetically identical diploid body cells.
• Meristems - tissues found in plants where undifferentiated cells are found - usually where growth can occur. These cells can give rise to root and shoot tissue as well as regenerating damaged areas.
• Embryonic stem cells derive from embryos. These are unspecialised cells that have the ability to self-renew for long periods of time and differentiate into specialised cells with specific functions.
• Cerebral hemispheres - centre of intelligence, memory, speech and consciousness.
• Cerebellum - controls muscle functions, speech, thought, emotions, reading, writing and learning.
• Medulla Oblongata - controls respiration, circulation and digestion.
• CAT scan - a series of slices of the brain taken from different angles to build a 3D picture of the brain.
• Positron Emitting Tomography (PET scan) - isotopes are carried to highly metabolising parts of the body. Positrons collide with electrons in the body and gamma photons emitted are detected outside the body with a gamma camera.
• Dendrites - collect electrical signals.
• Axon - pass the electrical signals onto other dendrites.
• Myelin sheath - signals pass down the dendrons and axons which are protected and insulated by the myelin sheath.
• Central Nervous System - consists of the brain and spinal chord, linked to sense organs by nerves.
• Receptors are specialised cells, usually in the sense organs, that detect a change in the environment. Stimuli such as touch, pressure, pain, chemicals, temperature or sound are turned into electrical impulses, which pass along neurones to the CNS and the brain.
• Sensory neurones - transmit impulses inwards from sensors.
• Relay neurones - within the CNS, pass on electrical impulses generated by the stimuli.
• Motor neurones - transmit signals from the CNS to muscles and glands elsewhere in the body.
• Reflex Arc:

  1. Arrival of stimulus and activation of receptor.
  2. Activation of a sensory neuron.
  3. Information processing in CNS.
  4. Activation of motor neuron.
  5. Response by effector.
• The eye:

  • Cornea
  • Iris
  • Pupil
  • Lens
  • Ciliary muscle
  • Retina (rod and cone cells).
• Cornea and lens - together these focus the light onto the back of the eye - the retina.
• Iris - this opens and closes to adjust the amount of light entering the eye.
• Rod and cone cells (in the retina) - rods are more numerous and more sensitive, but not to colour. Cones mediate colour. Colour-blindness is a genetic condition resulting in faulty cones and hence a difficulty in differentiating colour.
• Short-sighted: image forms in front of the retina. Corrected using a concave/diverging lens to 'spread out' the light rays, moving the image back.
• Far-sighted: image forms behind the retina. Corrected using a convex/converging lens to bring together the light rays and move the image forward.
• Cataracts - a fogging of the lens, often caused by excessive exposure to UV light, can only be corrected by replacement of the lens.