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Track 10: Neurophysiology

Track 10: Neurophysiology

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.