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What are the primary functions of the nervous system?
Sensory input (detects changes), integration (processes information), and motor output (activates responses).
What are neurons?
Specialized cells that transmit electrical impulses to communicate with other cells.
What is the function of neuroglia?
To support, nourish, protect, and insulate neurons.
What role do neurotransmitters play in neural communication?
They transmit signals across synapses from one neuron to another or to other target cells.
How is the nervous system organized?
Into the Central Nervous System (CNS) and Peripheral Nervous System (PNS).
What does the CNS consist of?
The brain and spinal cord.
What is the PNS, and what is its function?
The Peripheral Nervous System, which connects the CNS to the rest of the body, facilitating communication.
Describe the sensory (afferent) division of the PNS.
It carries signals from sensory receptors to the CNS.
Describe the motor (efferent) division of the PNS.
It transmits signals from the CNS to muscles and glands.
What are the two subdivisions of the motor division?
Somatic Nervous System (voluntary control) and Autonomic Nervous System (involuntary control).
What does the somatic nervous system control?
Voluntary movements of skeletal muscles.
What is the role of the autonomic nervous system?
Controls involuntary actions of smooth muscles, cardiac muscles, and glands.
Name the types of neuroglia found in the CNS.
Microglia, oligodendrocytes, astrocytes, and ependymal cells.
What are the types of neuroglia in the PNS?
Schwann cells and satellite cells.
What is the role of microglia?
Act as phagocytes, cleaning up cellular debris and pathogens in the CNS.
What is the function of oligodendrocytes?
Form the myelin sheath around CNS axons.
What do astrocytes do in the CNS?
Provide structural support, regulate nutrients, and maintain the blood-brain barrier.
What is the function of ependymal cells?
They produce and circulate cerebrospinal fluid in the CNS.
How do Schwann cells function in the PNS?
They produce myelin sheaths around peripheral nerves, aiding in impulse conduction.
Describe the structure of a neuron.
Consists of a cell body, dendrites, and an axon.
What is the purpose of dendrites?
They receive signals and conduct impulses toward the cell body.
What is the function of the axon?
Conducts impulses away from the cell body toward other neurons or effectors.
What is a myelin sheath?
An insulating layer that surrounds axons, speeding up impulse transmission.
What are nodes of Ranvier?
Gaps in the myelin sheath where ion exchange occurs, aiding rapid signal conduction.
Define resting membrane potential.
The stable, negative charge of a neuron at rest, typically around -70 mV.
What creates the resting membrane potential?
The unequal distribution of ions, with more sodium ions outside and more potassium ions inside the cell.
What is depolarization in a neuron?
The process by which the inside of a neuron becomes less negative, initiating an action potential.
Define action potential.
A rapid change in membrane potential that propagates along the neuron.
What is the 'all-or-none' principle?
An action potential either fully occurs if the threshold is met, or it does not occur at all.
Explain repolarization.
The process of returning the neuron to its resting membrane potential after an action potential.
What is hyperpolarization?
When the membrane potential becomes slightly more negative than the resting potential after repolarization.
Describe continuous conduction.
Sequential transmission of impulses along unmyelinated axons.
What is saltatory conduction?
Impulse transmission in myelinated axons where impulses 'jump' from one node of Ranvier to another.
What is the role of a synapse?
A junction where a neuron communicates with another neuron or cell.
What are excitatory neurotransmitters?
Chemicals that increase the likelihood of an action potential by making the postsynaptic neuron less negative.
What are inhibitory neurotransmitters?
Chemicals that decrease the likelihood of an action potential by making the postsynaptic neuron more negative.
What is the primary function of acetylcholine?
Controls skeletal muscle actions and can stimulate or inhibit autonomic responses depending on receptor types.
What role does norepinephrine play in the nervous system?
Associated with creating a feeling of well-being and may excite or inhibit autonomic nervous system responses.
What is the role of dopamine?
Produces a sense of pleasure; low levels are linked to Parkinson's disease.
Describe the function of serotonin.
Primarily inhibitory and associated with sleep; its activity is enhanced by SSRIs.
What is nitric oxide's role in the nervous system?
Acts as a vasodilator in the PNS and may play a role in memory in the CNS.
Define a reflex arc.
The pathway followed by nerve impulses in a reflex, typically involving a receptor, sensory neuron, interneuron, motor neuron, and effector.
What is the function of the patellar reflex?
Helps maintain posture by triggering the knee-jerk response upon stretching of the quadriceps tendon.
Describe the withdrawal reflex.
An involuntary response to pain that pulls the body part away from harmful stimuli, involving sensory, motor, and interneurons.
Explain neurotransmitter reuptake.
The process of neurotransmitters being reabsorbed by the presynaptic neuron for reuse, stopping their action on the postsynaptic cell.
What is a neuronal pool?
A group of neurons that process information and may either inhibit or excite responses in the CNS.
What is facilitation in neuronal pools?
A condition where a neuron becomes more responsive to stimulation after repeated excitatory input.
What is convergence in the nervous system?
Multiple presynaptic neurons connect to a single postsynaptic neuron, allowing it to integrate information.
Define divergence in the nervous system.
A single neuron branches out to communicate with multiple neurons, amplifying the signal.
What are mixed nerves?
Nerves that contain both sensory and motor fibers, most common in the PNS.
What are sensory (afferent) nerves?
Nerves that carry impulses from sensory receptors to the CNS.
What are motor (efferent) nerves?
Nerves that carry impulses from the CNS to effectors like muscles or glands.
Describe the structure of a nerve's connective tissue coverings.
Epineurium surrounds the entire nerve, perineurium surrounds nerve fascicles, and endoneurium surrounds individual nerve fibers.
What is the role of the blood-brain barrier?
A selective barrier maintained by astrocytes to protect the brain from harmful substances in the blood.
