Nervous System and Nervous Tissue - Anatomy & Physiology
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The nervous system includes the brain, spinal cord, and nerves.
Sensory detects stimuli, motor initiates responses, and integrative processes information.
Central nervous system (CNS) includes brain and spinal cord; Peripheral nervous system (PNS) includes all nerves outside CNS.
Somatic nervous system controls voluntary movements; Autonomic nervous system controls involuntary functions.
Sympathetic division prepares for 'fight or flight'; Parasympathetic division promotes 'rest and digest'.
Neurons transmit impulses; Neuroglial cells support and protect neurons.
Six types: Astrocytes, oligodendrocytes, microglia, ependymal cells (CNS), and Schwann cells, satellite cells (PNS).
Dendrites receive signals; Axons transmit impulses away from the cell body.
Myelin insulates axons and increases the speed of action potential propagation.
Neurons are classified as multipolar, bipolar, or unipolar based on the number of processes.
Neurons are sensory (afferent), motor (efferent), or interneurons based on function.
Leak channels, ligand-gated channels, mechanically gated channels, and voltage-gated channels.
Polarized at resting potential, depolarized when membrane potential becomes less negative, repolarized returning to resting, hyperpolarized when more negative than resting.
Action potentials are all-or-none signals; graded potentials vary in magnitude and decay with distance.
Resting membrane potential is approximately -70 mV.
Sodium (Na+) and potassium (K+) ions; Na+ is higher outside, K+ is higher inside the neuron at rest.
Na+ moves into the neuron during depolarization; K+ moves out during repolarization.
Time during which a neuron cannot fire another action potential or requires a stronger stimulus.
Absolute refractory period: no new action potential possible; relative refractory period: stronger stimulus needed.
Saltatory conduction occurs in myelinated axons jumping between nodes; continuous conduction occurs in unmyelinated axons.
Larger diameter axons conduct impulses faster due to less resistance.
A junction where a neuron communicates with another cell via chemical or electrical signals.
Chemical synapses use neurotransmitters; electrical synapses use direct ion flow through gap junctions.
Action potential triggers neurotransmitter release, which crosses the synaptic cleft and binds to receptors on the postsynaptic cell.
Chemical messengers released by neurons to transmit signals across synapses.
Neurotransmitters are broken down, reabsorbed, or diffuse away to end the signal.