Topic 5: Homeostasis and response

• Homeostasis is the regulation of internal conditions for example cells, Ph and enzymes
• Body temperature, blood glucose and water levels need to be regulated and monitored at all times
• A stimulus is a response to a change in an environment
• receptors can detect a stimulus and send chemical messages to the coordination centre and the effectors respond to the change
• The nervous system is made up of neurones which controls the behaviour in multi-cellular organisms
• An example in the body of a receptor is in the eye
• In the central nervous system, information from the receptors is sent there, reflexes are coordinated and these neurones transmit electrical impulses
• Effectors are muscles or glands, muscles contract, glands secrete hormones
• Sensory neurones send an electrical impulse from the receptors to the central nervous system
• Relay neurones send an electrical impulse from the sensory to the motor neurone which is found in the central nervous system
• motor neurones carry electrical impulses from the central nervous system to the effectors
• A synapse is a connection between two neurones, where nerve signals are transferred by chemicals which diffuse across the gap
• Reflexes are fast, automatic and remove people from danger
• A reflex arc sends an impulse along the sensory to relay, when the impulse reaches the gap a chemical is released and then an impulse from the motor to effector occurs
• Factors which can affect reaction time is

  • age
  • gender
  • caffeine
  • drugs
• Cerebral cortex is responsible for:

  • speech
  • consciousness
  • memory
  • intelligence
• The medulla is found at the top of the spinal cord which controls breathing and heart rate
• The cerebellum is found at the back of the brain and controls muslce coordination
• Sclera: tough supporting wall around the eye
• Cornea: refracts light into the eye
• Pupil: light enters the eye
• Iris: radial, circular muscles control the size of the pupil
• Retina: light receptor cells of colour and light
• Lens: focus light on the retina
• Cillary: suspensary muscles control the shape of the lens
• Optic nerve: impulse from retina receptors to the brain
• The eye is a sense organ
• iris reflex is when light receptors detect light, reflex is triggered to make pupil smaller, circular muscles contract, radial muscles relax
• accommodation: looking at distant and near objects, eye focuses light on retina and changes shape of lens
• near objects: cillary muscles contract, suspensory ligaments relax , lens is curved
• Distant objects: cillary muscles relax, suspensory ligaments pull tight, lens is thin
• Hyperopia: long sightedness, convex lens, lens refracts, focus on retina
• Myopia: short sighted, concave lens, light rays focus on retina
• Body temperature: 37 degrees enzymes work best, thermoregulatory centre, receptors are sensitive to the temperature of blood in the brain
• Hair: lies flat, less air trapped, no insulation of skin
• Sweat: Sweat glands, evaporates from the skin
• Blood vessels: dilate, more blood close to the skin, vasodilation
• Hormones: chemical messengers, travel via the blood stream
• Hormones are secreted by the endocrine glands, use of hormones to react to changes
• Pituitary glands secrete many hormones and is usually called the master gland