Neuronal Communication

• What are some examples of changes to the internal environment that organisms must respond to?

  - Blood glucose concentration

  - Internal temperature

  - Water potential

  - Cell pH
• What are examples of changes to the external environment that an organism must respond to?


  - Humidity

  - External temperature

  - Light intensity

  - New or sudden sound
• What are the two different responses to environment changes of organisms?

  Electrical responses (neurones), chemical responses (hormones).
• What are the responses to environmental changes of plants?


  Chemical responses (plant hormones).
• Why is coordination needed?


  Cells within an organism are specialised to carry out specific functions, and are therefore required to coordinate these different functions to operate.
• Why is coordination needed?


  Cells within an organism are specialised to carry out specific functions, and are therefore required to coordinate these different functions to operate.
• What is an example of where coordination is required in animals?

  - Red blood cells have no nucleus, meaning they are unable to replicate and so a constant supply must be provided by haematopoietic stem cells.

  - Cells require oxygen supply in order to respire, but these cells cannot transport oxygen so require red blood cells.
• What is an example of where this coordination is required in plants?


  - Flowering must coordinate with seasons, and pollinators must coordinate with the plants.
• What is homeostasis?


  The body's ability to coordinate the bodies systems to maintain a stable internal environment despite changes.
• What is cell signalling?


  Coordination relies on cellular level communication through cell signalling, occuring through the release of a chemical which has effect on another target cell.
• What does cell signalling allow cells to do?


  - Transfer signals locally, eg. between neurones at synapses, in which the signal is a neurotransmitter.

  - Transfer signals across long distances, eg. through hormones such as ADH (antidiuretic), which acts on kidney cells to maintain water balance.
• How is plant coordination different?

  Plants do not have a nervous system, so they respond to internal and external changes via hormones.
• What are neurones?


  Specialised cells in the nervous system that transmit information through electrical and chemical signals, carrying information from the sensory receptor to the effector.
• What is the cell body of a neurone?


  This contains the nucleus surrounded by cytoplasm that contains large amount of endoplasmic reticulum and mitochondria, which are involved in neurotransmitter production.
• What are dendrons in a neurotransmitter?


  These are short extensions which come from the cell body, dividing into smaller branches called dendrites, and they are responsible for transmitting electrical impulses TOWARDS to cell body.
• What is the axon in a neurone?


  SingIlse, elongated nerve fibres that transmit impulses AWAY from the cell body; these fibres can be very long, such as those running from the toes to spinal cord.
• What shape are these fibres?


  They are cylindrical in shape and consist of narrow regions of cytoplasm, surrounded by a plasma membrane.
• What are the three different types of neurone?


  Sensory, relay, and motor.
• What is a sensory neurone?


  These are neurones that transmit impulses from a sensory receptor to a cell to the central nervous system.
• What is the structure of a sensory neurone?


  They have a cell body, one dendron carrying impulses towards the cell body, and one axon carrying impulses away from the cell body.
• What are relay neurones?


  These neurons transmit impulses between neurons within the central nervous system, carrying impulses from sensory to motor neurones.
• What is the structure of a relay neurone?


  They have a cell body, many short dendrons that carry impulses towards the cell body, and many short axons that carry impulses away from the cell body.
• What are motor neurones?


  These neurones transmit impulses from relay neurons to an effector, such as a muscle or gland.
• What is the structure of a motor neurone?


  They have a cell body, many short dendrites carrying impulses towards the cell body (no dendron), and one long axon carrying impulses away from the cell body.
• Which neurones are myelinated?


  Sensory and motor neurones, but not all.
• What does it mean to be myelinated?


  Schwann cells grow and wrap around the axon, forming many layers of phospholipid bilayer (plasma membrane), and insulating it; forming a myelin sheath that allows neurones to conduct impulses at a faster rate.
• What are the nodes of ranvier?


  Gaps in the myelin sheath of a neuron, formed between adjacent schwann cells, and allowing electrical impulses to jump from one to the next; making for much faster conduction of impulse, as depolarisation of the axon can only occur in the gaps of ranvier.
• What is multiple sclerosis?


  An autoimmune disease, whereby the immune systems mistakenly attacks healthy body tissue; resulting in the thinning or complete loss of the myelin sheath, and eventually the breakdown of axons in neurones. It's unknown what causes this disorder, but it is thought to be a combination of genetic and environmental factors.
• What are the symptoms of multiple sclerosis?


  It effects the brain and spinal cord and therefore causes problems with muscle movement, balance, and vision.
• What do sensory receptors do?


  Convert stimulus that they detect into a nerve impulse, which is then passed through the nervous system and into the central nervous system.
• Which part of the central nervous system is the nerve impulse usually sent to?


  The brain, which then coordinates the required response and sends an impulse to an effector.
• Where are sensory receptors usually located?


  Sense organs, such as the ear and eye.
• What are the two key features of sensory receptors?


  Specificity - they are specific to a single type of stimulus.

  Transducer - they convert stimulus into nerve impulses.
• What are the types of sensory receptor?

  Mechanoreceptors, chemoreceptors, thermoreceptors, and photoreceptors.
• What is a mechanoreceptor?


  A receptor that responds to pressure and movement changes.
• What is an example of a mechanoreceptor and sense organ where it could be found?

  Pacinian corpuscle (detects pressure) - skin.
• What is a chemoreceptor?


  A receptor that detects chemicals changes.
• What is an example of a chemoreceptor and a sense organ where it can be found?

  Olfactory receptor (detects smells) - nose.
• What is a thermoreceptor?


  This is a receptor that detects change in heat.
• What is an example of a thermoreceptor and a sensory organ where it can be found?


  End-bulbs of Krause - tongue.