
Sub Topics: Molecular and Cellular Neuroscience, Cognitive Neuroscience,...
Sub Tracks Clinical Neurology, Neurodegenerative...
SUB TOPIC ;Basic Principles of Neurophysiology,
Sensory Physiology, Motor Physiology, Neuroplasticity, Autonomic Nervous System
(ANS), Brain Function and Neurophysiological Mapping
Neurophysiology is
the branch of physiology that focuses on the study of the functions and
activities of the nervous system. It encompasses the mechanisms through which
the nervous system controls and coordinates various bodily functions, including
sensory perception, movement, and higher cognitive functions. Neurophysiology
examines how neurons and other cells in the nervous system communicate, process
information, and generate behavior. Below are the major components and key
concepts in neurophysiology:
Key
Concepts in Neurophysiology:
1. Neurons
and Glial Cells
Neurons: The functional units of the nervous system,
responsible for transmitting electrical and chemical signals. Neurons
communicate with each other through electrical impulses (action potentials) and
synapses.
Structure: Neurons consist of the cell body, dendrites
(receive signals), and axon (sends signals).
Types: Sensory neurons, motor neurons, and interneurons.
Glial Cells: These are supportive cells that help maintain
homeostasis, form myelin, and provide support and protection for neurons. Types
include:
Astrocytes: Maintain the blood-brain barrier and provide
nutrients.
Oligodendrocytes and Schwann Cells: Form myelin in the CNS
and PNS, respectively.
Microglia: Act as the immune defense in the CNS.
2. Resting
Membrane Potential
The resting membrane potential of a neuron is the difference
in electrical charge between the inside and outside of the cell when it is not
transmitting an impulse, typically around -70 mV.
This potential is maintained by the sodium-potassium pump,
which moves 3 Na+ ions out of the cell for every 2 K+ ions moved in, and by the
selective permeability of the membrane to different ions (K+, Na+, Cl-).
3. Action
Potential
Action Potential: A rapid, temporary change in the membrane
potential that occurs when a neuron is stimulated.
Depolarization: Sodium (Na+) channels open, and Na+ ions
rush into the neuron, making the inside more positive.
Repolarization: Potassium (K+) channels open, allowing K+
ions to exit, restoring the negative internal charge.
Refractory Period: After an action potential, the neuron
enters a period of rest before it can fire again. This ensures the
directionality of the signal.
4.
Synaptic Transmission
Synapse: The junction between two neurons where the
transmission of electrical signals occurs. It can be:
Electrical Synapses: Direct transmission of signals via gap
junctions.
Chemical Synapses: Signals are transmitted via
neurotransmitters.
Neurotransmitters: Chemicals that carry signals across
synapses. They can be:
Excitatory (e.g., glutamate) - increase the likelihood of an
action potential.
Inhibitory (e.g., GABA) - decrease the likelihood of an
action potential.
5. Sensory
Physiology
Sensory receptors detect stimuli (e.g., light, sound,
pressure, and pain) and send signals through sensory neurons to the brain,
where they are processed into perception.
Mechanoreceptors: Detect pressure and vibration.
Photoreceptors: Detect light (e.g., rods and cones in the
retina).
Thermoreceptors: Detect changes in temperature.
Nociceptors: Detect painful stimuli.
Sensory Pathways: Information is carried to the brain via
specific pathways:
Somatosensory Pathway: For touch, pain, and temperature.
Visual Pathway: For sight, involving the retina and visual
cortex.
Auditory Pathway: For sound, from the cochlea to the
auditory cortex.
6. Motor
Physiology
Motor Pathways: These pathways involve upper motor neurons
(in the brain) and lower motor neurons (in the spinal cord) that control
voluntary and involuntary movements.
Voluntary Movement: Initiated in the primary motor cortex
and carried out by the motor neurons.
Involuntary Movement: Includes reflexes and movements
controlled by the brainstem (e.g., heartbeat, digestion).
Neuromuscular Junction: The point where a motor neuron
synapses with a muscle fiber. When a motor neuron releases acetylcholine, it
triggers muscle contraction.