B5

• Homeostasis - maintenance of internal conditions - mechanisms in place to keep the optimium conditions (despite internal/external changes)
• Homeostasis is needed because : important for enzyme action, and all cell functions
• Homeostasis controls : blood glucose concentration, body temperature and water levels
• Nervous and hormonal communication is involved in automatic control systems - they detect changes and respond to them
• All control systems have : receptors, coordination centres, and effectors
• Receptors detect stimuli
• Coordination centres process information received from receptors
• Effectors bring about the responses and brings the conditions in body back to optimum levels
• The nervous system allows us to : react to our surroundings and coordinate actions in response to stimuli
• Usual response to stimuli :

  • receptors - convert stimuli to an electrical impulse
  • electrical impulse travels along sensory neuron to CNS
  • info processed and appropriate response is coordinated - result in electrical impulse sent along motor neuron to effector
  • effector carry out response - muscles contracting, or glands secreting hormones
• A reflex is an automatic response and it takes place before you have time to think
• Reflexes are important because it prevents an individual from getting hurt
• Reflexes prevent harm by information traveling down the pathway - this is called the reflex arc and the vital response will take place quickly
• Reflex pathway is different to the usual response to stimuli because the impulse does not pass through the conscious area of the brain
• The process of reflex arc:

  • stimulus detected by receptors
  • impulse sent along sensory neuron
  • in CNS - impulse pass to relay neuron
  • impulse sent along motor neuron
  • impulse reaches effector - resulting in appropriate response
• An example of a reflex arc : pupils getting smaller - avoid damage from bright lights, moving away from hot surface - prevents damage
• Synapses are gaps between two neurones
• At the synapse : impulse reaches end of first neuron - chemical released into synapse - chemical diffuses across synapse - chemical reaches second neuron - triggers impulse to begin again in next neuron
• Reaction time is how long it takes you to respond to a stimulus
• You can test reaction time using a ruler drop test
• The brain is made up of many connected neurons and it controls complex behaviour
• The components of the brain :

  • cerebral cortex
  • cerebellum
  • medulla
• The cerebral cortex is the outer part of the brain
• The cerebellum is the rounded structure towards the bottom/back of the brain
• Medulla is found in the brain stem - on front of the cerebellum
• The cerebral cortex controls :

  • consciousness
  • intelligence
  • memory
  • language
• The cerebellum controls :

  • fine movement of muscles
• The medulla controls :

  • unconscious actions like breathing and heart rate
• Investigating brain function and treating brain damage/disease is difficult because :

  • complex and delicate
  • easily damaged
  • drugs given to treat diseases do not always reach brain due to membranes surrounding it
  • not fully understood the functions and regions of brain
• Neuroscientists can map out the regions of the brain by:

  • studying patients with brain damage - observing changes in individuals after damage on certain areas - provides information on the role this area has
  • electrically stimulating different parts of the brain - pushing electrode into brain - stimulation may result in mental/physical change - provides information on role in certain area
  • MRI scanning techniques - creates image of brain - shows area affected brain with tumour, or which area is active during a specific task
• The eye contains receptors that are sensitive to light intensity and colour
• The eyes are adapted to allow eye to change its shape - focus on near or distant objects and dim light
• The term used to describe how eyes are adapted to focus on near/distant objects is accommodation
• The different structures found in the eye are :

  • retina
  • optic nerve
  • sclera
  • cornea
  • iris
  • ciliary muscles and suspensory ligaments
• The retina is a layer of light-sensitive cells found at the back of the eye
• The retina works by : light hits and the cell is stimulated and impulses are sent to the brain - which interprets information and creates image
• Optic nerve - a nerve that leaves eye and leads to brain - carries impulses from retina to brain to create an image
• Sclera is the white outer layer, supports structures inside eye, and strong to prevent some damage to eye
• The cornea is the see-through layer at the front of the eye - allows light through and the curved surface will bend and focuses light onto retina
• The iris are muscles that surround the pupil and they contract or relax to alter the size of the pupils