Nervous System Flashcards
Describe the primary functions of the nervous system
The nervous system controls thoughts, memory, learning, and feelings. It interprets sensory information, regulates heartbeat patterns, and manages stress responses.
Explain the two main divisions of the nervous system
The nervous system is divided into:
Central Nervous System (CNS): Brain and spinal cord, processes sensory information and initiates responses.
Peripheral Nervous System (PNS): All other nerves, relays information between the CNS and the rest of the body.
List the subdivisions of the peripheral nervous system (PNS)
Autonomic Nervous System (ANS): Controls internal organs and glands.
Sympathetic division (arousing)
Parasympathetic division (calming)
Somatic Nervous System (SNS): Controls voluntary muscles and senses.
Describe the structure of a neuron
Dendrites: Receive signals and carry them to the cell body.
Cell Body: Contains the nucleus; integrates signals.
Axon: Transmits action potential away from the cell body.
Myelin Sheath: Insulates the axon and speeds conduction.
Axon Terminal: Connects to the next neuron’s dendrites, enabling signal transmission.
Explain the three types of neurons and their functions
Sensory Neurons: Bring impulses from receptors to the CNS.
Relay Neurons: Connect sensory neurons to motor neurons.
Motor Neurons: Carry impulses from the CNS to effectors like muscles or glands.
Define a reflex arc and explain its steps
A reflex arc is the pathway of neurons involved in a reflex action. Steps:
Receptor detects stimulus and sends an impulse via the sensory neuron.
Impulse reaches the spinal cord; relay neuron connects to motor neuron.
Motor neuron carries impulse to the effector for a quick response.
What is action potential
Action potential is a brief change in voltage across a neuron’s membrane caused by ion flow. It triggers nerve impulses for communication.
describe the stages of action potential
Depolarisation: Na⁺ channels open; Na⁺ floods in, raising voltage to +30mV.
Repolarisation: K⁺ channels open; K⁺ leaves, restoring membrane potential.
Hyperpolarisation: K⁺ channels close slowly, causing a brief negative overshoot.
Resting Potential: Sodium-potassium pump restores ion balance.
Explain saltatory conduction
Saltatory conduction occurs in myelinated neurons, where action potentials “jump” between nodes of Ranvier, making transmission faster compared to unmyelinated neurons.
List factors affecting the speed of nerve impulse doncution
Axon Diameter: Larger diameter = faster conduction.
Myelination: Myelinated axons transmit impulses faster.
Number of Synapses: Fewer synapses = faster communication.
Define Neurotransmitters and their role
Neurotransmitters are chemicals released by neurons at synapses, allowing transmission of impulses from one neuron to another.
Give examples of neurotransmitters
Examples include acetylcholine, dopamine, and serotonin.
Describe the transmission process across a synapse
Action potential arrives at the presynaptic neuron.
Ca²⁺ channels open; Ca²⁺ enters and fuses with vesicles containing neurotransmitters.
Neurotransmitters are released into the synaptic cleft.
They bind to receptors on the postsynaptic neuron, triggering a new action potential.
Neurotransmitters are recycled or broken down.
What is resting potential in neurons?
Resting potential is the voltage difference across a neuron’s membrane when at rest, maintained at around -70mV due to the sodium-potassium pump.
explain the role of the myelin sheath
The myelin sheath insulates the axon, preventing ion leakage and enabling faster impulse transmission via saltatory conduction.
describe the structure and function of Schwann cells
Schwann cells produce myelin, wrapping around axons to form the myelin sheath, which speeds up nerve impulse conduction.
Explain the concept of the “all or none principle” in action potential
If a stimulus reaches the threshold (-55mV), an action potential occurs; if not, no action potential is triggered.
define a synapse
A synapse is the junction where two neurons meet, separated by a gap called the synaptic cleft, through which signals are transmitted chemically.
What is the role of calcium ions (Ca²⁺) in neurotransmission?
Calcium ions enter the presynaptic neuron, causing vesicles filled with neurotransmitters to fuse with the membrane and release their contents into the synaptic cleft.
Explain the role of neurotransmitters in synaptic transmission
Neurotransmitters carry the signal across the synaptic cleft by binding to specific receptors on the postsynaptic membrane, initiating an action potential in the postsynaptic neuron.
What is the synaptic cleft?
The synaptic cleft is the narrow gap (about 20 nm) between the presynaptic and postsynaptic neurons where neurotransmitters are released.
What happens to neurotransmitters after they bind to the postsynaptic receptors?
They are either recycled by reuptake into the presynaptic neuron.
Broken down by enzymes in the synaptic cleft.
Diffused away from the synapse.
What is the role of enzymes in the synaptic cleft?
Enzymes break down neurotransmitters, ensuring they do not overstimulate the postsynaptic neuron and allowing the synapse to reset.
