Physiology
Neurophysiology
Neurophysiology for MBBS and NEET-PG: synaptic transmission, sensory and motor tracts, cerebellum and basal ganglia, reflexes and the autonomic nervous system, mapped to NMC codes PY10.
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Neurophysiology
Neurophysiology for MBBS and NEET-PG: synaptic transmission, sensory and motor tracts, cerebellum and basal ganglia, reflexes and the autonomic nervous system, mapped to NMC codes PY10.
Neurophysiology covers how the nervous system senses, integrates and controls the body. It deals with synaptic transmission, the sensory and motor pathways, the roles of the cerebellum and basal ganglia, the reflexes, the autonomic nervous system and higher functions such as sleep.
High-yield: Neurophysiology
- A synapse transmits signals through neurotransmitters released into the synaptic cleft.
- Excitatory postsynaptic potentials depolarise and inhibitory postsynaptic potentials hyperpolarise the neuron.
- The sensory pathways carry information to the cortex, with the dorsal column for fine touch and proprioception.
- The spinothalamic tract carries pain and temperature and crosses close to its level of entry.
- The corticospinal tract is the main motor pathway and mostly crosses in the medulla.
- The cerebellum coordinates movement, balance and motor learning without initiating movement.
- The basal ganglia help plan and smooth voluntary movement, and their disease causes Parkinsonism.
- The stretch reflex is monosynaptic and is the basis of the knee jerk.
- Muscle spindles sense the length of muscle, while Golgi tendon organs sense tension.
- Upper motor neuron lesions cause spasticity and brisk reflexes, while lower motor neuron lesions cause flaccidity and wasting.
- The autonomic nervous system has sympathetic and parasympathetic divisions with opposing actions.
- The hypothalamus regulates temperature, hunger, thirst and the autonomic and endocrine systems.
- The reticular activating system maintains wakefulness and consciousness.
- Sleep alternates between rapid eye movement and non-rapid eye movement stages through the night.
Key ascending and descending tracts
- **Dorsal column:** Fine touch, vibration and proprioception. Crosses in the medulla.
- **Spinothalamic tract:** Pain and temperature. Crosses near the level of entry.
- **Corticospinal tract:** Main voluntary motor pathway. Mostly crosses in the medulla.
- **UMN vs LMN lesion:** UMN: spasticity, brisk reflexes. LMN: flaccidity, wasting.
NMC competencies in this chapter
- **PY10.1:** Organisation of the nervous system and synaptic transmission
- **PY10.3:** Sensory receptors and the somatosensory system
- **PY10.6:** Ascending sensory tracts and pain pathways
- **PY10.7:** Descending motor tracts and control of movement
- **PY10.10:** Reflexes and their clinical assessment
- **PY10.12:** Functions of the cerebellum and basal ganglia
- **PY10.15:** The autonomic nervous system
- **PY10.18:** Higher functions, sleep and the electroencephalogram
Frequently Asked Questions
What is the difference between an EPSP and an IPSP?
An excitatory postsynaptic potential depolarises the neuron and brings it closer to firing, while an inhibitory postsynaptic potential hyperpolarises it and moves it away from firing.
Which tract carries pain and temperature?
The spinothalamic tract carries pain and temperature sensation, and it crosses to the opposite side within a few segments of entering the spinal cord.
How do upper and lower motor neuron lesions differ?
An upper motor neuron lesion causes spasticity, brisk reflexes and an upgoing plantar, while a lower motor neuron lesion causes flaccid weakness, wasting and lost reflexes.
What does the cerebellum do?
The cerebellum coordinates movement, maintains balance and posture and supports motor learning, but it does not initiate voluntary movement itself.
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