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This is the complete lecture note for MED408 Neurology I. You can read it online below, open it in the full viewer, or download the PDF for offline study. It pairs with the course's video lectures, so you can read and watch together.
Course code: MED 408 Course title: Neurology I Course credit load: 2 Units Series 1: Foundations of Neurology • Part 1.1: Overview of the Nervous System o Sub Part 1.1.1: Organisation of the nervous system o Sub Part 1.1.2: Neurons and glial cells o Sub Part 1.1.3: The synapse and neurotransmitters • Part 1.2: The Central Nervous System o Sub Part 1.2.1: The cerebral cortex and lobes o Sub Part 1.2.2: The brainstem and cerebellum o Sub Part 1.2.3: The spinal cord • Part 1.3: The Peripheral and Autonomic Nervous Systems o Sub Part 1.3.1: The peripheral nervous system o Sub Part 1.3.2: The autonomic nervous system o Sub Part 1.3.3: The neuromuscular junction • Part 1.4: Neurological Localisation o Sub Part 1.4.1: Principles of localisation o Sub Part 1.4.2: Upper and lower motor neuron lesions o Sub Part 1.4.3: Common localisation patterns Introduction Neurology is the branch of medicine concerned with disorders of the nervous system. A sound knowledge of neuroanatomy and neurophysiology is the essential starting point for clinical practice in neurology, because every deficit a patient presents with reflects damage to a specific, predictable part of the nervous system. This Series builds that foundation.
We shall commence by examining how the nervous system is organised and how its cells communicate. Next, we will explore the functional anatomy of the central nervous system. Moving on, we will consider the peripheral and autonomic nervous systems. Finally, we will apply all of this to neurological localisation, the clinical skill of identifying the site of a lesion from the pattern of the patient's deficits. Series Learning Outcomes Upon completing this Series, you should be able to: • SLO 1.1: describe the organisation of the nervous system and the structure and function of neurons and glial cells, • SLO 1.2: describe the structure and function of the synapse and the major neurotransmitters, • SLO 1.3: describe the functional anatomy of the cerebral cortex, brainstem, cerebellum, and spinal cord, • SLO 1.4: describe the organisation and function of the peripheral and autonomic nervous systems and the neuromuscular junction, and • SLO 1.5: apply the principles of neurological localisation to distinguish upper from lower motor neuron lesions and identify common localisation patterns. 1.1 Overview of the Nervous System 1.1.1 Organisation of the nervous system The nervous system is divided into two broad components. The central nervous system (CNS) consists of the brain and spinal cord, where information is integrated and processed. The peripheral nervous system (PNS) includes all neural tissue outside the CNS: cranial nerves, spinal nerves, ganglia, and plexuses. Within the PNS, the somatic nervous system controls voluntary skeletal muscle movement and transmits sensory information from the body to the CNS. The autonomic nervous system (ANS) regulates involuntary visceral functions such as heart rate, blood pressure, and digestion, and is further divided into the sympathetic (fight-or-flight) and parasympathetic (rest-and-digest) divisions. Fill in the blank: The brain and spinal cord together form the ________ nervous system. The division controlling involuntary visceral functions is the ________ nervous system.
1.1.2 Neurons and glial cells The neuron is the functional unit of the nervous system. It consists of dendrites (short processes that receive incoming signals), a cell body or soma (containing the nucleus), and an axon (a single long process that conducts action potentials away from the soma to the axon terminals). Many axons are wrapped in a myelin sheath, which insulates the fibre and enables rapid saltatory conduction by allowing the impulse to jump between gaps called nodes of Ranvier. Glial cells support and protect neurons. Oligodendrocytes produce myelin in the CNS (one cell myelinating up to 50 axons), while Schwann cells produce myelin in the PNS (one cell per axon segment). Astrocytes maintain the blood-brain barrier and provide metabolic support. Microglia are the resident immune cells of the CNS. Ependymal cells line the ventricles and produce cerebrospinal fluid. Fill in the blank: The process that conducts signals away from the neuron cell body is the ________. In the CNS, myelin is produced by ________, while in the PNS it is produced by Schwann cells. 1.1.3 The synapse and neurotransmitters A synapse is the junction between two neurons or between a neuron and its target cell. When an action potential reaches the presynaptic terminal, calcium influx triggers release of neurotransmitter into the synaptic cleft. The neurotransmitter binds to receptors on the postsynaptic membrane, producing either excitation or inhibition. The signal ends when the neurotransmitter is broken down by enzymes or taken back up into the presynaptic terminal. The major neurotransmitters are: glutamate (the main CNS excitatory neurotransmitter), GABA (the main CNS inhibitory neurotransmitter, enhanced by benzodiazepines), acetylcholine (at the neuromuscular junction and in the ANS), dopamine (movement and reward, depleted in Parkinson's disease), serotonin (mood and sleep, increased by SSRIs), and noradrenaline (arousal and sympathetic function). Fill in the blank: The main inhibitory neurotransmitter in the CNS is ________, while the main excitatory neurotransmitter is glutamate. ________ is depleted in the substantia nigra in Parkinson's disease.
Figure 1.1: Structure of a neuron and chemical synapse with neurotransmitter reference Pilot questions 1.1 1. Distinguish the CNS from the PNS. (Linked to SLO 1.1) 2. Describe the structure of a neuron, naming each part and its function. (Linked to SLO 1.1) 3. Distinguish oligodendrocytes from Schwann cells. (Linked to SLO 1.1) 4. Describe the sequence of events at a chemical synapse. (Linked to SLO 1.2) 5. Name four major neurotransmitters and state the function of each. (Linked to SLO 1.2) 1.2 The Central Nervous System 1.2.1 The cerebral cortex and lobes The cerebrum is divided into four lobes. The frontal lobe contains the primary motor cortex (voluntary movement), the prefrontal cortex (executive function and personality), and Broca's area in the dominant hemisphere (motor speech production). The parietal lobe contains the primary somatosensory cortex and Wernicke's area in the dominant hemisphere (language comprehension); the non-dominant parietal lobe mediates spatial attention. The temporal lobe
processes auditory information and houses the hippocampus (memory formation). The occipital lobe contains the primary visual cortex, processing the contralateral visual field. All motor fibres from the cortex and all sensory fibres to the cortex pass through the internal capsule, a compact white matter tract deep within each hemisphere. A small lesion here causes a dense contralateral hemiplegia affecting the face, arm, and leg equally, because all fibres are packed into this small area. Fill in the blank: Broca's area in the dominant hemisphere controls motor ________ production. Damage to Wernicke's area causes fluent but meaningless speech with impaired ________. 1.2.2 The brainstem and cerebellum The brainstem (midbrain, pons, and medulla) contains the nuclei of cranial nerves III to XII, the reticular activating system (consciousness and arousal), and the respiratory and cardiovascular centres. All ascending sensory and descending motor tracts pass through it. A brainstem lesion produces the crossed deficit pattern: ipsilateral cranial nerve signs (from the cranial nerve nucleus at the level of the lesion) combined with contralateral limb weakness and sensory loss (from the long tracts). The cerebellum coordinates movement and balance. Because of the double-crossing of its pathways, cerebellar lesions produce ipsilateral signs, remembered by the mnemonic DANISH: Dysdiadochokinesia, Ataxia, Nystagmus, Intention tremor, Scanning speech (dysarthria), and Hypotonia. Fill in the blank: A brainstem lesion causes ________ cranial nerve signs combined with ________ limb signs (the crossed deficit). Cerebellar signs occur on the ________ side as the lesion. 1.2.3 The spinal cord The spinal cord extends from the foramen magnum to the conus medullaris at L1 to L2. On cross-section, grey matter (H-shaped) contains the anterior horn lower motor neurons and the posterior horn sensory relay neurons, surrounded by white matter tracts. Three tracts are essential knowledge: the dorsal columns (fine touch, vibration, proprioception: cross at the medulla), the spinothalamic tract (pain and temperature: cross within 1 to 2 segments of entry), and the corticospinal tract (voluntary motor: crosses at the pyramidal decussation in the medulla). A cord hemisection produces the Brown-Sequard syndrome: ipsilateral motor loss and dorsal column loss (fine touch, vibration, proprioception) combined with contralateral pain and temperature loss, all below the level of the lesion. This dissociated sensory loss is unique to spinal cord lesions. Fill in the blank: The dorsal columns cross at the ________, while the spinothalamic tract crosses within ________ to two segments of entering the cord. A cord hemisection produces the ________ syndrome.
Figure 1.2: Cerebral lobes with key functional areas and spinal cord cross-section with tracts Pilot questions 1.2 1. Describe the functions of the four cerebral lobes. (Linked to SLO 1.3) 2. Explain the difference between Broca's and Wernicke's aphasia. (Linked to SLO 1.3) 3. Describe the crossed deficit pattern of a brainstem lesion. (Linked to SLO 1.3) 4. List the DANISH signs of cerebellar disease. (Linked to SLO 1.3) 5. Describe the three major spinal cord tracts and the Brown-Sequard syndrome. (Linked to SLO 1.3) 1.3 The Peripheral and Autonomic Nervous Systems 1.3.1 The peripheral nervous system There are 31 pairs of spinal nerves, each formed by the union of a dorsal (posterior)
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