nerves/nervous systems

• describe synaptic transmission:

  • action potential arrives at axon terminal of presynaptic neuron
  • this stimulates neurotransmitters to form in vesicles
  • vesicles move to the membrane of the presynaptic neuron and release neurotransmitters into synapse
  • neurotransmitters diffuse across the synapse to receptors on the membrane of the post synaptic neuron
  • if there are mostly excitatory signals, the neuron will fire
• the structure of a sensory neurone is: dendrites, axon, cell body
• the function of sensory neurones are to fire and send off signals to the CNS about information being received from the environment
• the structure of a motor neurone is: cell body, axon, dendrites
• the function of a motor neurone is to carry electrical impulses from the CNS to effectors, e.g- muscles
• the structure of a relay neurone is: short dendrites, long axon, cell body axon terminals
• the function of a relay neurone is to transmit impulses from the sensory neurone to the motor neurone- relay neurone are found in the brain and spinal cord
• dendrites receive signals from receptors or other neurons and carry them to the cell body
• axon terminals are the end of the axon that is covered in a myelin sheath, axons carry impulses away from the cell body
• the myelin sheath is a fatty substance that insulates the axon, speeding up impulse transmission
• the central nervous system (CNS) controls behaviour and involves the brain and spinal cord, it receives info from senses and transmits these to muscles and glands
• the peripheral nervous system (PNS)controls all relay and motor neurones outside of the CNS and relays messages to and from the CNS
• the somatic nervous system is found within the PNS and controls voluntary and conscious responses
• the autonomic nervous system is found within the PNS and controls involuntary functions such as heart rate and breathing
• the sympathetic nervous system is found within the autonomic nervous system and is responsible for the fight or flight response
• the parasympathetic nervous system is found within the autonomic nervous system and helps to relax the body after an emergency response
• Explain why neurones can only transmit information in one direction at a synapse.

  the synaptic vesicles containing the neurotransmitter are only present and released from the presynaptic membrane

  the receptors for the neurotransmitters are only present on the postsynaptic membrane

  Diffusion of the neurotransmitters mean they can only go from high to low concentration, so can only travel from the presynaptic to the postsynaptic membrane.
• how does the body respond during fight or flight?

  he fight or flight response causes adrenaline to be released which can cause an increased production of sweat and faster heart and breathing rate.

  the fight or flight response enable a quick reaction to fight the threat or run away.