A2 - Nervous system Flashcards
Central Nervous System (CNS)
Consists of the brain and spinal cord.
Peripheral Nervous System (PNS)
Consists of sensory and motor neurons.
Sensory Neurons
Neurons that receive information from receptors and transmit it to the CNS.
Motor Neurons
Neurons that carry information from the CNS to effectors, such as muscles.
Neurons
Cells that receive and transmit nerve impulses or action potentials.
Soma
The large cell body of a neuron.
Dendrites
Small projections on a neuron that receive signals from other neurons.
Axon
A long projection of a neuron that carries nerve impulses away from the soma.
Axon Terminal
The end of the axon that communicates with the dendrite of the next neuron
Synaptic Cleft
The small gap between the axon terminal and the dendrite of the next neuron.
Nerve Impulse
Electrical signals that carry information along neurons.
Action Potential
Brief change in voltage across a neuron’s membrane, resulting in a nerve impulse
Ion Balance
The equilibrium of ions (charged particles) within a nerve cell.
Nerves
Bundles of neurons that form a network throughout the body.
Neurotransmitters
Chemicals released by neurons that transmit signals across the synaptic cleft.
Synaptic Cleft
The small gap between neurons where neurotransmitters are released and received.
Receptors
Proteins on the post-synaptic membrane that bind to neurotransmitters
Glial Cells
Cells that support and nourish neurons, digesting dead neurons and producing neuronal components.
Resting Potential
Potential difference across the membrane of a neuron in its resting state, with the interior of the cell negative compared to the exterior.
Concentration Gradient
Difference in ion concentration between the inside and outside of a neuron
Voltage-Gated Ion Channels
Ion channels that open or close in response to changes in voltage.
Threshold Voltage
The minimum voltage required to trigger an action potential (around -55mV).
Depolarization
Change in membrane potential where the inside of the membrane becomes less negative.
Polarization
State of a neuron’s membrane when at rest, with a positive charge outside and negative charge inside.
Stimulus
Chemical, mechanical, thermal, or electrical signal that triggers a response in a neuron.
Repolarization
Restoration of the internal negativity of a neuron after depolarization, achieved by K+ channels opening and allowing K+ to rush out of the cell. -70mV.
Sodium-Potassium Pump
Protein pump that actively transports Na+ out of the cell and K+ into the cell, restoring ionic conditions.
Hyperpolarization
Membrane potential falls below the resting potential, causing the interior of the membrane to become more negative than -70mV.
Refractory Period
The time taken for the membrane to return to resting potential after hyperpolarization, during which an action potential cannot be generated.
Overshoot
Excessive increase in the interior membrane potential during hyperpolarization.
K+ Channels
Potassium ion channels that are slow to close, resulting in excessive efflux of potassium ions.
Interior Membrane Potential
Electrical charge inside the neuron’s membrane.
K+ Permeability
Ability of potassium ions to pass through the membrane.
Na+ Channels
Sodium ion channels that reset during hyperpolarization.
K+ Efflux
Outward flow or diffusion of potassium ions.
Unidirectional Signal
Hyperpolarization prevents the neuron from receiving another stimulus and ensures that the signal proceeds in one direction only.
Signal Propagation
The transmission of an action potential along an axon.
Nerve Impulse Speed
The speed at which a nerve impulse travels in humans
Unmyelinated Fibers
Nerve fibers without a myelin sheath, where nerve impulses travel at a speed of 1-3 m/s.
Myelinated Fibers
Nerve fibers with a myelin sheath, where nerve impulses travel at a speed of 3-120 m/s.
Axon Diameter
The size of the axon, with larger axons allowing for faster conduction of nerve impulses.
Myelination
The presence of myelin around a neuron, which increases the speed of nerve impulse conduction.
Number of Synapses
The quantity of synapses involved in transmitting a nerve impulse, with fewer synapses resulting in faster communication.
Myelin Sheath
Fatty insulating layer around the axon, formed by Schwann cells, which enhances the speed of action potential travel.
Schwann Cells
Specialized cells that wrap around the axon to form the myelin sheath
Nodes of Ranvier
Exposed areas on the myelinated axon where ion exchange occurs.
Saltatory Conduction
The process of the nerve signal jumping from one node of Ranvier to the next along a myelinated axon, significantly increasing conduction speed.
Synapse
The junction where two neurons meet, allowing communication between them
Presynaptic Neuron
Neuron carrying the nerve impulse towards the synaptic cleft.
Postsynaptic Neuron
Neuron receiving the nerve impulse from the presynaptic neuron and carrying it away.
Neurotransmitters
Chemical molecules used by the nervous system to transmit messages between neurons or from neurons to muscles.
Dendrites
Branch-like projections at the end of a neuron’s axon that receive signals from other neurons.
Receptor Molecules
Molecules on the membrane of the postsynaptic neuron that bind to neurotransmitters.
Acetylcholine
A common neurotransmitter responsible for muscle contraction.
Action Potential Arrival
The action potential reaches the pre-synaptic membrane at the end of the axon.
Calcium Ion Entry
Calcium ion channels open, allowing calcium ions (Ca+2) to enter the axon.
Vesicle Movement
Vesicles containing neurotransmitters move towards the pre-synaptic membrane.
Vesicle Fusion and Release
Vesicles fuse with the pre-synaptic membrane and release neurotransmitters into the synaptic cleft.
Neurotransmitter Diffusion
Neurotransmitters diffuse across the synaptic cleft from high to low concentration, down a concentration gradient.
Receptor Binding
Neurotransmitters bind to receptors on the post-synaptic cell membrane.
Sodium Ion Entry
Sodium ion channels open in the post-synaptic membrane, allowing sodium ions to enter and depolarize the membrane.
Neurotransmitter Recycling
Neurotransmitters are recycled through enzyme degradation or re-uptake into the pre-synaptic neuron.
Neurotransmitter Removal
Neurotransmitters are removed from the synaptic cleft to prevent continuous stimulation, either by re-uptake or enzyme degradation.
Threshold Level
The minimum level of neurotransmitter required to produce a postsynaptic action potential.
