Glossary

• Nervous system = made up of the brain, spinal cord and nerves carrying impulses around the body
• Hormonal system = releases hormones into the bloodstream so they can travel around the body
• Neurotransmitters = chemicals released by a nerve to diffuse across a synapse
• Cell body = compact section of the nerve cell that contains the nucleus and cytoplasm
• Dendrons = short branches extensions of a nerve cell which conduct impulses towards a cell body
• Dendrites = component of the dendron allowing it to branch out further
• Axon = portion of a nerve cell that carries nerve impulses away from the cell body
• Schwann cells = type of cell that surrounds neurones and covers them with a myelin sheath
• Myelin sheath = protective membrane that wraps around part of certain nerve cells
• Myelin = mixture of proteins and phospholipids forming an insulating sheath
• Nodes of ranvier = gaps in the myelin sheath coating on the neural axon
• Sensory neurones = nerve cells that are activated by sensory input from the environment
• Motor neurones = nerve cells that regulate voluntary and involuntary movements by transmitting signals
• Relay neurones = neurones in the CNS relaying impulses from the sensory neurone to the motor neurone
• Receptor = cell/group of cells that receive information from a stimuli
• Effector = tissue/structure/organ that becomes active in response to stimulation
• Action potential = occurs when a neurone sends information down an axon
• Repolarised = when the membrane potential of a neurone returns to its resting state
• Sodium potassium pump = specialised transport protein that moves sodium and potassium ions
• Depolarisation = when a change occurs inside a cell that causes the distribution of electric charges to alter
• Saltatory response = propagation of action potentials along the myelinated axons
• All-or-nothing principle = signal transmission between neurones is only dependent on the threshold being met
• Threshold value = controls whether or not a stimuli will generate an action potential
• Voltage-gated channels = channels that are activated by changes in the electrical membrane potential
• Refractory period = period of time when an action potential can't be stimulated again
• Synaptic cleft = space between the axon of one neurone and the dendrites of another
• Presynaptic neurone = neurone that sends signals to the post-synaptic neurone across the synapse
• Synaptic knob = location where the nerve impulse is transmitted across the synaptic cleft
• Synaptic vesicles = vesicles clustered at presynaptic terminals that store neurotransmitters
• Unidirectionality = operating or moving in one direction only
• Spatial summation = when multiple presynaptic neurones form a junction with a single neurone
• Temporal summation = single presynaptic neurone rapid-firing signals to a single postsynaptic neurone's synapse
• Inhibitory synapses = regulate the flow of sensory information through the spinal cord
• Excitatory synapses = stimulate the postsynaptic neurone to generate an action potential
• Cholinergic synapse = synapses that use acetylcholine as their neurotransmitter
• Acetylcholine = neurotransmitter that carries messages from the brain to the body through nerve cells
• Myofibrils = bundles of protein filaments that contain contractile elements
• Sarcoplasm = cytoplasm of a muscle cell with a large amount of glycogen
• Actin = protein that is an important contributor to the contractile property of a muscle, thin filament
• Myosin = family of motor proteins known for their roles in muscle contraction, thick filament