Neurophysiology of the CNS. Physiology of spinal cord. Reflex, reflex arc. Functions of the nervous system. Neuroglia: types and functions. Types of interneuronal connections (chain and circular). Reflex: definition and significance. Classification of reflexes. Reflex arc: structure and significance of its components. Reflex time: definition and factors affecting it. Inhibition in the CNS: types and significance. Spinal cord: structure and functions. Conduction function: ascending and descending pathways. Spinal shock: definition and causes. №6. Physiology of brainstem (medulla, pons, midbrain). Physiology of cerebellum. Physiology of the medulla oblongata. Functions. What vital and non-vital centers are located in the medulla oblongata? Which cranial nerves originate from this region? Physiology of the pons. Functions. How does the pons function as a bridge between different parts of the brain? What is its role in the regulation of respiration? Physiology of the midbrain. Functions. What are the functions of the superior and inferior colliculi? What is the motor significance of the red nucleus and substantia nigra? Functional anatomy and histology of the cerebellum. Functions. What are the three layers of the cerebellar cortex? What are the deep cerebellar nuclei? Functional divisions and connections of the cerebellum. How do the vestibulocerebellum, spinocerebellum, and cerebrocerebellum differ in their afferent and efferent pathways? Cerebellar functions and applied physiology. What are the mechanisms of “damping,” “comparator,” and “servomechanism”? What are the typical clinical signs of cerebellar lesions? №7. Physiology of brain cortex. Functional histology of the cortex: What are the six structural layers of the neocortex and the primary cell types (Pyramidal, Stellate) and the significance of Betz cells? Lobes and functional areas: How is the cortex divided into Frontal, Parietal, Temporal, and Occipital lobes, and what are their primary Brodmann areas? Frontal lobe physiology: What are the roles of the Primary Motor Area, Broca’s area, and the Prefrontal cortex in movement and personality? Sensory and association areas: How do the Parietal, Temporal, and Occipital lobes process somatosensory, auditory, and visual information? Cerebral dominance and speech: What is the concept of categorical vs. representational hemispheres, and how do Wernicke’s and Broca’s areas coordinate speech? Electrical activity (EEG): What are the characteristic brain waves (Alpha, Beta, Theta, Delta) and the significance of the "Alpha Block"? №8. Physiology of ANS. Somatic nervous system: characteristics. Autonomic nervous system: characteristics. Sympathetic nervous system: characteristics. Parasympathetic nervous system: characteristics. Metasympathetic nervous system: characteristics. Answer this questions in detail of physiology in easy words for viva it should be short and easy to understand too take the reference from Guyton Hall Sembulingam also
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The retrieved documents give some useful content but are limited. I'll now compile a thorough, comprehensive answer drawing on Guyton & Hall and Sembulingam as the primary references, supplemented by the retrieved material. This is a large structured viva answer covering all topics.
CNS Physiology — Complete Viva Notes
(Based on Guyton & Hall + Sembulingam)
📘 TOPIC 5: Neurophysiology of CNS — Spinal Cord, Reflex, Reflex Arc
🔹 Functions of the Nervous System
The nervous system has three basic functions (Guyton & Hall, Ch. 45):
- Sensory input — detects stimuli from internal and external environments
- Integrative function — processes and interprets information (thinking, memory, decision-making)
- Motor output — controls muscles and glands to produce responses
🔹 Neuroglia: Types and Functions
Neuroglia are supporting cells of the CNS. They outnumber neurons ~10:1.
| Type | Location | Function |
|---|---|---|
| Astrocytes | CNS | Structural support, blood-brain barrier, nutrient supply, scar formation |
| Oligodendrocytes | CNS | Myelin formation around CNS axons |
| Microglia | CNS | Immune defense (phagocytosis — the "macrophages of the brain") |
| Ependymal cells | CNS (ventricles) | Line ventricles, produce CSF |
| Schwann cells | PNS | Myelin formation around PNS axons |
| Satellite cells | PNS ganglia | Support neuronal cell bodies |
(Sembulingam, Ch. 10; Guyton & Hall, Ch. 45)
🔹 Types of Interneuronal Connections
1. Chain (Serial/Diverging/Converging) Circuits:
- Divergence — one neuron synapses on many; amplifies signal (e.g., pain sensation spreading widely)
- Convergence — many neurons synapse on one; integrates input (e.g., motor control)
- Serial chain — neurons in series; allows relay of signals step by step
2. Circular (Reverberating) Circuits:
- Output of the last neuron feeds back to stimulate the first neuron
- Produces prolonged, sustained activity (e.g., rhythmic breathing, memory consolidation)
- This is why a stimulus can cause a response that outlasts the original input
(Guyton & Hall, Ch. 46)
🔹 Reflex: Definition and Significance
Definition: A reflex is an automatic, involuntary, stereotyped response to a specific stimulus, mediated through the nervous system without conscious control.
Significance:
- Protects body from injury (withdrawal reflex)
- Maintains homeostasis (e.g., baroreceptor reflex)
- Regulates posture and movement
- Forms the basis of neurological examination
🔹 Classification of Reflexes
| Basis | Types |
|---|---|
| Origin | Inborn (unconditioned) vs. Acquired (conditioned) |
| No. of synapses | Monosynaptic (e.g., knee jerk) vs. Polysynaptic (e.g., withdrawal) |
| Response | Somatic (muscle) vs. Visceral (organ) |
| Location of arc | Spinal reflex vs. Cranial reflex |
| Type of receptor | Exteroceptive, Interoceptive, Proprioceptive |
| Effect | Excitatory vs. Inhibitory |
(Sembulingam, Ch. 12)
🔹 Reflex Arc: Structure and Significance of Components
A reflex arc has 5 components:
Receptor → Afferent nerve → Nerve center → Efferent nerve → Effector
| Component | Structure | Significance |
|---|---|---|
| Receptor | Sensory ending (skin, muscle, etc.) | Detects stimulus |
| Afferent limb | Sensory neuron (dorsal root) | Carries impulse to CNS |
| Nerve center | Interneurons in spinal cord/brain | Integration, modulation |
| Efferent limb | Motor neuron (ventral root) | Carries command to effector |
| Effector | Muscle/gland | Produces the response |
Bell-Magendie Law: Dorsal root = sensory; Ventral root = motor
🔹 Reflex Time: Definition and Factors Affecting It
Definition: The time between application of a stimulus and appearance of the response. Includes: receptor activation + afferent conduction + synaptic delay + efferent conduction + effector activation.
Factors affecting reflex time:
- Number of synapses — more synapses = longer time (each synapse adds ~0.5 ms)
- Intensity of stimulus — stronger stimulus → faster response (spatial & temporal summation)
- Fatigue — increases reflex time
- Drugs — depressants increase, stimulants decrease
- Temperature — cold slows, warmth speeds up
- Age — elderly have longer reflex times
- State of CNS — alertness decreases, sleep increases reflex time
🔹 Inhibition in the CNS: Types and Significance
Definition: Inhibition = suppression of neural activity — essential to prevent uncontrolled, chaotic responses.
| Type | Mechanism | Example |
|---|---|---|
| Postsynaptic inhibition | IPSPs via inhibitory interneuron (hyperpolarization via Cl⁻/K⁺) | Renshaw cell inhibition |
| Presynaptic inhibition | Inhibitory synapse on axon terminal reduces NT release | Pain modulation (gate theory) |
| Recurrent inhibition | Motor neuron activates Renshaw cell which feeds back to inhibit same motor neuron | Prevents over-firing |
| Lateral inhibition | Inhibits adjacent neurons to sharpen signal | Two-point discrimination |
| Feed-forward inhibition | Interneuron inhibits target before signal arrives | Agonist-antagonist coordination |
Significance: Prevents muscle spasm, allows precise movement, prevents seizures, sharpens sensory contrast.
(Guyton & Hall, Ch. 46)
🔹 Spinal Cord: Structure and Functions
Structure:
- Gray matter (butterfly/H-shape): dorsal horn (sensory), ventral horn (motor), lateral horn (autonomic at T1–L2, S2–S4)
- White matter: ascending and descending tracts (myelinated axons)
- 31 pairs of spinal nerves (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal)
Functions:
- Conduction — pathway between brain and periphery
- Reflex activity — spinal reflexes (stretch, withdrawal, etc.)
- Locomotion — central pattern generators
- Autonomic control — bladder, bowel, sexual function
🔹 Conduction Function: Ascending and Descending Pathways
Ascending (Sensory) Tracts:
| Tract | Sensation | Route |
|---|---|---|
| Dorsal column (fasciculus gracilis/cuneatus) | Fine touch, vibration, proprioception | Ipsilateral → medulla (cross there) → thalamus → cortex |
| Spinothalamic (lateral) | Pain, temperature | Cross at spinal cord level → contralateral → thalamus → cortex |
| Spinothalamic (anterior) | Crude touch, pressure | Cross in spinal cord |
| Spinocerebellar | Proprioception to cerebellum | Largely ipsilateral |
Descending (Motor) Tracts:
| Tract | Function |
|---|---|
| Corticospinal (pyramidal) | Voluntary fine movements; crosses in medullary pyramids |
| Rubrospinal | Muscle tone, voluntary movement |
| Vestibulospinal | Posture and balance |
| Reticulospinal | Muscle tone, reflexes |
| Tectospinal | Head/neck orientation to visual/auditory stimuli |
🔹 Spinal Shock: Definition and Causes
Definition: Sudden, transient depression of all spinal cord functions below the level of a complete transverse spinal cord injury. Characterized by areflexia, flaccid paralysis, loss of sensation, and autonomic dysfunction below the lesion.
(Spine Injury Best Practices, p. 52)
Causes:
- Loss of tonic facilitatory impulses from higher brain centers (reticulospinal, vestibulospinal tracts)
- Sudden isolation of spinal cord segments from supraspinal control
Duration: Hours to weeks; followed by hyperreflexia and spasticity (due to denervation hypersensitivity)
Signs: Flaccid paralysis → later spastic paralysis; Absent reflexes → later exaggerated reflexes
📘 TOPIC 6: Physiology of Brainstem & Cerebellum
🔹 Physiology of the Medulla Oblongata
The medulla is the most inferior part of the brainstem, continuous with the spinal cord at the foramen magnum.
Vital Centers (damage = death):
| Center | Function |
|---|---|
| Cardiac center | Controls heart rate and force |
| Vasomotor center | Controls blood vessel tone/BP |
| Respiratory center (DRG & VRG) | Controls rhythm of breathing |
Non-vital Centers:
- Vomiting center (chemoreceptor trigger zone)
- Coughing, sneezing, swallowing, hiccoughing centers
- Deglutition (swallowing)
Cranial Nerves from Medulla:
- CN VIII (vestibulocochlear — partly)
- CN IX (glossopharyngeal)
- CN X (vagus)
- CN XI (spinal accessory — partly)
- CN XII (hypoglossal)
🔹 Physiology of the Pons
Location: Between medulla and midbrain; contains the middle cerebellar peduncles.
Functions:
- Bridge (pons = Latin for "bridge") — connects cerebellum with cerebral cortex and spinal cord via cerebellar peduncles
- Respiratory regulation — contains pneumotaxic center (limits inspiration, increases respiratory rate) and apneustic center (prolongs inspiration)
- Relay station — pontine nuclei relay cortical signals to cerebellum
- Reflex functions — facial expressions, chewing, salivation
Cranial Nerves:
- CN V (trigeminal)
- CN VI (abducens)
- CN VII (facial)
- CN VIII (vestibulocochlear — partly)
🔹 Physiology of the Midbrain
Location: Between pons and diencephalon; contains cerebral aqueduct (Aqueduct of Sylvius).
Structures and Functions:
| Structure | Function |
|---|---|
| Superior colliculi | Visual reflexes — turning head/eyes toward a visual stimulus; pupillary light reflex coordination |
| Inferior colliculi | Auditory reflexes — turning head toward a sound |
| Red nucleus | Receives input from cerebellum & motor cortex; controls muscle tone and voluntary limb movements via rubrospinal tract |
| Substantia nigra | Produces dopamine; controls smooth, coordinated movements; degeneration → Parkinson's disease |
| Cerebral peduncles | Carry corticospinal and corticobulbar tracts |
| Periaqueductal gray | Endogenous pain suppression (opioid receptors) |
Cranial Nerves:
- CN III (oculomotor)
- CN IV (trochlear)
🔹 Functional Anatomy and Histology of the Cerebellum
3 Layers of Cerebellar Cortex (outside → inside):
| Layer | Cell Types |
|---|---|
| 1. Molecular layer (outermost) | Stellate cells, basket cells, dendrites of Purkinje cells |
| 2. Purkinje cell layer (middle) | Purkinje cells — the only OUTPUT neurons of cerebellar cortex; always inhibitory (GABA) |
| 3. Granular layer (innermost) | Granule cells (excitatory), Golgi cells |
Deep Cerebellar Nuclei (the true output of cerebellum — lateral → medial):
- Dentate nucleus — largest; controls planning of movement
- Emboliform nucleus
- Globose nucleus
- Fastigial nucleus — balance and posture
(Mnemonic: "Don't Eat Greasy Food")
🔹 Functional Divisions and Connections of the Cerebellum
| Division | Also Called | Afferent Input | Efferent Output | Function |
|---|---|---|---|---|
| Vestibulocerebellum (flocculonodular lobe) | Archicerebellum | Vestibular nuclei | Vestibular nuclei → vestibulospinal tract | Balance and eye movement |
| Spinocerebellum (vermis + intermediate zone) | Paleocerebellum | Spinal cord (spinocerebellar tracts) | Fastigial → reticulospinal; Interposed → rubrospinal | Muscle tone, posture, gait coordination |
| Cerebrocerebellum (lateral hemispheres) | Neocerebellum | Cortex → pontine nuclei → cerebellum | Dentate → thalamus → motor cortex | Planning and fine coordination of voluntary movements |
🔹 Cerebellar Functions and Applied Physiology
Three Key Mechanisms (Guyton & Hall, Ch. 57):
- Damping mechanism: Cerebellum acts like a shock absorber — prevents overshooting of movements (tremor at rest vs. intention tremor — cerebellar = intention)
- Comparator (Error detector): Compares intended movement (from motor cortex) with actual movement (from proprioceptive feedback) and corrects errors in real time
- Servomechanism: Continuously adjusts motor commands using feedback — like a thermostat; anticipates future position of limbs
Clinical Signs of Cerebellar Lesions (DANISH):
| Sign | Description |
|---|---|
| Dysdiadochokinesia | Inability to perform rapid alternating movements |
| Ataxia | Wide-based, staggering, unsteady gait |
| Nystagmus | Involuntary rhythmic eye movements |
| Intention tremor | Tremor that worsens near the target |
| Scanning speech (dysarthria) | Slurred, monotone, irregular speech |
| Hypotonia | Reduced muscle tone |
- Rebound phenomenon, past pointing (dysmetria)
📘 TOPIC 7: Physiology of the Brain Cortex
🔹 Functional Histology of the Cortex
Six Layers of the Neocortex (surface → depth):
| Layer | Name | Major Cells / Notes |
|---|---|---|
| I | Molecular (plexiform) | Mostly dendrites and axons; few cells |
| II | External granular | Small pyramidal and stellate cells |
| III | External pyramidal | Medium pyramidal cells; intracortical connections |
| IV | Internal granular | Stellate (granule) cells; main sensory input layer (receives thalamocortical fibers) |
| V | Internal pyramidal (ganglionic) | Large pyramidal cells; Betz cells here; motor OUTPUT layer |
| VI | Multiform (fusiform) | Mixed cells; corticothalamic projections |
Primary Cell Types:
- Pyramidal cells: Large, triangular; excitatory; project to distant targets (corticospinal tract)
- Stellate (granule) cells: Small, interneurons; both excitatory and inhibitory; mainly sensory processing
Betz Cells:
- Giant pyramidal neurons in Layer V of primary motor cortex (Area 4)
- Give rise to the largest, fastest-conducting fibers of the corticospinal tract
- Control fine voluntary movements, especially of distal limbs (fingers)
🔹 Lobes and Functional (Brodmann) Areas
| Lobe | Key Brodmann Areas | Function |
|---|---|---|
| Frontal | Area 4 (Primary motor), Area 6 (Premotor), Area 44/45 (Broca's), Area 8 (Frontal eye field), Area 9–12 (Prefrontal) | Voluntary movement, speech production, planning, personality |
| Parietal | Area 1, 2, 3 (Primary somatosensory), Area 5, 7 (Somatosensory association) | Somatosensory processing, spatial awareness |
| Temporal | Area 41, 42 (Primary auditory), Area 22 (Wernicke's), Area 28 (Entorhinal) | Hearing, language comprehension, memory |
| Occipital | Area 17 (Primary visual), Area 18, 19 (Visual association) | Vision processing |
🔹 Frontal Lobe Physiology
1. Primary Motor Area (Area 4):
- Controls voluntary, contralateral movements via corticospinal tract
- Somatotopic map = Motor homunculus (inverted; hands and face have largest representation)
- Betz cells here generate the fastest motor commands
2. Broca's Area (Area 44 & 45 — left hemisphere):
- Speech production (motor speech area)
- Damage → Broca's (expressive) aphasia — patient understands but cannot speak fluently
3. Prefrontal Cortex (Area 9–12):
- Personality, judgment, working memory, emotional behavior, decision-making
- Damage → personality changes, poor impulse control (classic: Phineas Gage case)
- Also controls executive functions
🔹 Sensory and Association Areas
Parietal Lobe:
- Primary somatosensory cortex (Areas 1, 2, 3): Touch, pain, temperature, proprioception from contralateral body
- Somatosensory association cortex (Areas 5, 7): Interpretation of sensory info — recognizes objects by touch (stereognosis)
- Damage → astereognosis, neglect syndrome
Temporal Lobe:
- Primary auditory cortex (Areas 41, 42): Perception of sound
- Auditory association (Area 22 — Wernicke's): Language comprehension
- Damage → Wernicke's (receptive) aphasia — fluent but meaningless speech
Occipital Lobe:
- Primary visual cortex (Area 17 — striate cortex): Receives input from lateral geniculate body; processes basic visual features (edges, contrast)
- Visual association (Areas 18, 19): Object recognition, color, motion
🔹 Cerebral Dominance and Speech
Categorical (Dominant) Hemisphere — usually LEFT:
- Language (Broca's + Wernicke's), analytical thinking, math, writing, logic
Representational (Non-dominant) Hemisphere — usually RIGHT:
- Spatial awareness, music, artistic ability, face recognition, emotional tone
Speech Coordination:
- Wernicke's area (comprehension) connects to Broca's area (production) via the arcuate fasciculus
- Damage to arcuate fasciculus → Conduction aphasia — cannot repeat, but can speak and understand
| Aphasia | Area Damaged | Speech | Comprehension | Repetition |
|---|---|---|---|---|
| Broca's | Area 44/45 | Non-fluent | Intact | Impaired |
| Wernicke's | Area 22 | Fluent, nonsensical | Impaired | Impaired |
| Conduction | Arcuate fasciculus | Fluent | Intact | Impaired |
| Global | Both Broca's + Wernicke's | Non-fluent | Impaired | Impaired |
🔹 Electrical Activity — EEG Waves
| Wave | Frequency | Amplitude | State |
|---|---|---|---|
| Alpha (α) | 8–13 Hz | Medium | Awake, relaxed, eyes closed |
| Beta (β) | 14–30 Hz | Low | Active mental work, eyes open |
| Theta (θ) | 4–7 Hz | Variable | Drowsiness, early sleep, children |
| Delta (δ) | < 4 Hz | High | Deep sleep (Stage 3–4), anesthesia; also in brain pathology if awake |
Alpha Block (Berger's wave):
- When eyes are opened or mental concentration begins, alpha waves are replaced by lower-amplitude, higher-frequency beta waves
- Also called "desynchronization" or "arousal response"
- Clinical use: EEG helps diagnose epilepsy, brain death, sleep disorders
(Guyton & Hall, Ch. 59)
📘 TOPIC 8: Physiology of the Autonomic Nervous System (ANS)
🔹 Somatic Nervous System (SNS) — Characteristics
| Feature | Details |
|---|---|
| Target | Skeletal (voluntary) muscle only |
| Neurons | Single motor neuron from CNS to effector |
| Neurotransmitter | Acetylcholine (ACh) at neuromuscular junction |
| Effect | Always excitatory (causes muscle contraction) |
| Control | Voluntary (conscious) |
| Fiber type | Large myelinated (fast — Type Aα) |
🔹 Autonomic Nervous System (ANS) — General Characteristics
| Feature | Details |
|---|---|
| Target | Smooth muscle, cardiac muscle, glands, adipose tissue |
| Neurons | Two neurons — preganglionic + postganglionic |
| Control | Involuntary (unconscious) |
| Ganglia | Present between pre- and post-ganglionic neurons |
| NTs | ACh (preganglionic all divisions), NE or ACh (postganglionic) |
(Sembulingam, Ch. 11)
🔹 Sympathetic Nervous System — Characteristics
| Feature | Details |
|---|---|
| Origin | Thoracolumbar (T1–L2) — "thoracolumbar outflow" |
| Ganglia location | Close to spinal cord (paravertebral chain / prevertebral ganglia) |
| Pre : Post ratio | 1:20 (one preganglionic → many postganglionic = widespread effect) |
| Preganglionic NT | Acetylcholine (nicotinic receptor) |
| Postganglionic NT | Norepinephrine (exception: sweat glands and adrenal medulla use ACh) |
| Receptors | α1, α2, β1, β2, β3 adrenergic receptors |
| General effect | "Fight or flight" — increases HR, BP, dilates pupils, bronchodilation, decreases GI activity |
| Fiber length | Short preganglionic, long postganglionic |
Key Sympathetic Effects:
- Heart: ↑ HR (chronotropy), ↑ force (inotropy) — β1
- Blood vessels: vasoconstriction — α1
- Lungs: bronchodilation — β2
- Pupils: mydriasis (dilates) — α1
- GI: decreased motility, sphincters contracted
🔹 Parasympathetic Nervous System — Characteristics
| Feature | Details |
|---|---|
| Origin | Craniosacral (CN III, VII, IX, X + S2–S4) — "craniosacral outflow" |
| Ganglia location | Close to or within the target organ |
| Pre : Post ratio | 1:1 to 1:3 (localized, discrete effects) |
| Preganglionic NT | Acetylcholine (nicotinic receptor) |
| Postganglionic NT | Acetylcholine (muscarinic receptor) |
| Receptors | M1, M2, M3 muscarinic receptors |
| General effect | "Rest and digest" — decreases HR, increases GI motility, pupil constriction |
| Fiber length | Long preganglionic, short postganglionic |
Key Parasympathetic Effects:
- Heart: ↓ HR — M2 (via vagus, CN X)
- Pupils: miosis (constricts) — M3
- GI: increased motility, increased secretions — M3
- Salivary glands: increases salivation — M3
- Bladder: detrusor contraction (micturition) — M3
🔹 Sympathetic vs. Parasympathetic — Quick Comparison
| Feature | Sympathetic | Parasympathetic |
|---|---|---|
| Origin | T1–L2 | Craniosacral (CN III, VII, IX, X; S2–S4) |
| Ganglia | Paravertebral/prevertebral (near cord) | Terminal (near/in organ) |
| Pre fiber | Short | Long |
| Post fiber | Long | Short |
| Post NT | Norepinephrine | Acetylcholine |
| Effect | Fight or flight | Rest and digest |
| HR | ↑ | ↓ |
| BP | ↑ | Slight ↓ |
| Pupil | Dilates | Constricts |
| Bronchi | Dilates | Constricts |
| GI motility | ↓ | ↑ |
🔹 Metasympathetic Nervous System — Characteristics
This is a third division of the ANS, described prominently in Russian/Eastern European physiology tradition (also discussed in Sembulingam):
| Feature | Details |
|---|---|
| Location | Intrinsic ganglia within the walls of the GI tract, heart, and bladder |
| Also called | Enteric nervous system (ENS) — "the second brain" |
| Components | Myenteric (Auerbach's) plexus + Submucosal (Meissner's) plexus |
| Neurons | Contains sensory, motor, and interneurons (~500 million neurons!) |
| Neurotransmitters | ACh, Serotonin (5-HT), Substance P, VIP, NO, dopamine |
| Function | Controls GI motility, secretion, absorption independently of CNS |
| Key feature | Can function autonomously without any connection to the brain or spinal cord |
Significance: The ENS/metasympathetic system is why gut motility continues even after spinal cord injury. It's why ~95% of the body's serotonin is in the gut. It modulates its own local reflexes (peristaltic reflex, secretory reflex).
(Guyton & Hall, Ch. 63; Sembulingam)
📝 Quick Viva Summary Table
| Topic | Key Point to Remember |
|---|---|
| Neuroglia | Oligodendrocytes = CNS myelin; Schwann = PNS; Microglia = brain macrophages |
| Reflex arc | 5 components; Bell-Magendie law |
| Inhibition | Renshaw cell = recurrent inhibition of motor neurons |
| Spinal shock | Flaccid paralysis first → spastic later (denervation hypersensitivity) |
| Medulla | Vital centers: cardiac, vasomotor, respiratory |
| Cerebellum | DANISH signs; Purkinje cells = only output of cortex (inhibitory) |
| Betz cells | Layer V, Area 4; largest corticospinal fibers |
| Broca's vs Wernicke's | Broca = production (can't speak); Wernicke = comprehension (can't understand) |
| Alpha block | Eyes open → alpha → beta (desynchronization) |
| Sympathetic | Thoracolumbar; NE; fight or flight |
| Parasympathetic | Craniosacral; ACh; rest and digest |
| Metasympathetic | ENS; intrinsic GI ganglia; works independently |
References: Guyton & Hall Textbook of Medical Physiology (14th ed.), Ch. 45–48, 56–59, 63; Sembulingam Essentials of Medical Physiology (8th ed.), Ch. 10–13, 18–22, 29.
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