5.3-nerves

• Axons are covered by myelin sheath which insulates them to speed up conduction
• The axon is the long, thin part that conducts nerve impulses away from the cell body.
• Myelinated axons have nodes of Ranvier where the myelin is interrupted, allowing saltatory conduction (jumping) along the axon
• Unmyelinated axons do not have nodes of Ranvier so action potentials travel slowly along the whole length of the axon
• Myelinated neurones have an insulating layer called the myelin sheath around their axons. This speeds up the transmission of electrical signals along the axon.
• Sensory neurones carry information towards the CNS (central nervous system).
• Neurotransmitters are chemicals released at synapses that carry signals across the gap between cells
• Neurotransmitters are chemicals released at synapses that transmit signals across the gap
• Excitatory neurotransmitters increase the likelihood of an action potential being generated in the postsynaptic membrane
• Saltatory conduction occurs when electrical signals 'jump' across the gap at the node of Ranvier instead of travelling continuously down the axon.
• Motor neurones carry information away from the CNS (central nervous system)
• Action potentials occur when there is a sudden change in voltage across the membrane due to the opening of sodium channels.
• Reflexes are rapid responses to stimuli without conscious thought or control
• The myelin sheath is made from Schwann cells, which wrap themselves around the axon to form multiple layers of cell membranes.
• In saltatory conduction, the signal jumps from one node of Ranvier to another, allowing it to travel faster than if it had to pass through the entire length of the axon.
• Pacinian corpuscles are pressure sensors found in the skin
• The Pacinian corpuscle has a structure of sensory nerve fibre, rings of connective tissue and fibroblast.
• Rods and cones are the receptor cell for visuals, located in the eye's retina.
• Vibration receptors are responsible for hearing reception. located in the cochlea (ear).
• Olfactory cells are responsible for reception of smell found in the epethical lining located in the nose.
• Chemical receptors located in the taste buds found in the tongue are the taste recpetors.
• There are three types of neurons: sensory neurons, motor neurons, and relay neurons.
• Relay neurons connect sensory and motor neurones.
• Sensory neurones carry the action potential from the sensory receptor to the CNS.
• Motor neurones carry an action potential from the CNS to an effector, like a muscle or gland.
• Action potential is a brief reversal of the potential across the membrane of a neurone causing a peak of +40mV.
• The resting potential of a neuron is -60mV.
• Summation is the process that occurs when the effects of several exciting post-synaptic potentials are added together.
• The two types of summation are: temporal summation and spatial summation.
• Temporal summation occurs when multiple action potential signals fire down the axon of a single neuron to be received by the synapse of another neuron.
• Spatial summation occurs when multiple action potential signals from different neurons arrive at the same synapse on one neuron.
• Hyperpolarization is when the membrane potential becomes more negative than the resting potential.
• Repolarization is the restoration of the membrane potential to its resting potential.
• The refractory period is time period immediately after stimulation where the nerve or muscle is unresponsive to further stimulation.