C2.2 Neural Signalling Flashcards
Distinguish between a sensory neuron and a motor neuron
A motor neuron has a single long axon that carries impulses away from the cell body. The function of the motor neuron is to carry impulses away from the CNS to effectors such as muscle glands. In contrast, sensory neurons have their vell body away from the neuron, with a dendron running to the cell body and an aon away from it. Sensory neuron carries information to the central nervous system (CNS).
Outline how a resting potential is generated.
resting potential is the product of active transport of potassium ions (K+) INTO and across the membrane and sodium ions (Na+) OUT and across the membrane. This occurs by a K+/Na+ (sodium potassium) pum, using energy from ATP.
Three NA+ pumped out for 2 K+ pumped in. Tissue fluid OUTSIDE the neuron hence contains many more positive ions than in cytoplasm. As a result, a begative charge is developed inside and the neuron is said to be polarized. The membrane potential is the difference in charge between the outside and inside of a neuron, creared due to unequal distribution of ions on btih sides of cell memrbane. The next event or passage of an impulse is called an action potential
It pumps 3 Na⁺ ions out of the cell and 2 K⁺ ions into the cell for each ATP molecule consumed. This process creates and maintains the concentration gradients of Na⁺ (higher outside) and K⁺ (higher inside), which is essential for generating action potentials.
Define action potential
Action potential is the potential difference produced across the plasma membrane of the nerve cell when stimulated. This reverses the resting potentiak of -70mV to +40mV.
What is variation of speed of nerve impulses caused by?
Unmyleinated transmit impulses slower than myelinated neurons. Additionally, the larger the diameter of the axon, the faster the rate of transmission.
What is a synapse?
A synapse is the connection between the end of the nerve cell and another cell. It is traversed by transmitter substances.
Define the term neurotransmitter
A neurotransmitter is a CHEMICAL released at the PRESYNAPTIC membrane of an axon, due to ACTION POTENTIAL, it TRANSMITS the action potential ACROSS the synapse.
Extra: neurotransmitters are produced in the golgi apparatus- the neurotransmitter comes from amino acid, produced in the GA in the pre-synaptic clef
Give examples of some neurot transmitters
Acetylecholine.
Explain the function of acetylecholine in neuromuscular junctions OR Explain the mechanism of muscle contraxtion with regards to acetylecholine’s role as a neurotransmitter.
Neuromuscular junctions are a specialized synapse between a motor neuron nerve ending and its musce fibre. They convert electrical impulses generated by the motor neuron into electrical activity in the muscle fibres. When an action potential arrives at the neuromuscular junction, VESICLES OF ACETYLECHOLINE release and TRANSMITTER MOLECULES BIND TO RECEPTORS on the SARCOPLASM (plasma membrane of the muscle fibre), triggering the RELEASE of calcium ions from the sarcoplasm reticulum, leading to muscle contraction
Identify the role of the golgi apparatus and the mitochondria of the synaptic knob in synapse transmission
The mitochondria provides energy for the reformation of the calcium ion after enzyme inactivation and diffusion back into the pre-synaptic membrane. The golgi apparatus produces the neurotransmitter that is recycled (calcium ion)
Explain how a synapse functions through transmitter substance cycles.
Firstly, an impulse arrives at the synapse and triggers calcium ion entry. Then, transmitter substances are releeased, and diffuse to the postsynaptic membranes by diffusion, from a high concentration to a low concentration. The transmitter substance then binds, triggering the entry of NA+ ionsand action potential in the postsynaptic membrane. Then, there is the enzymic inactivation of the transmitter. Lastly, there is the reformation of transmitter to substance vesicles after it diffuses back to the presyanptic membrane.
