1. What is the general process of neural activity?

The nervous system is the body‘s commanding system that regulates and integrates body functions by coordinating its voluntary and involuntary actions via reflex that is mediated via the reflex arc, commonly including sensory receptors, afferent neural pathway, neural center, efferent pathway and effectors.

2. What is the functional difference between neurons and glia?

Neuron is the basic functional unit of the nervous system and electrically excitable cell that processes and transmits information through electrical and chemical signals. Glial cells are non-neuronal cells that maintain homeostasis, form myelin, and provide support and protection for neurons in the CNS and PNS.

3. What is the feature of nerve conduction?

(1) Structural and functional integrity; (2) Insulation or relative independentability; (3) Capacity of bidirectional conduction; (4) Relative indefatigability; (5) All-or-none; (6) Conduction speed and manners are strongly influenced by the presence of myelin.

4. Please briefly describe the process of chemical synaptic transmission and its characteristics

Synapse is a specialized structure that permits electrical communication between neurons, or the junction between the axon terminals of a neuron and the receiving cells.

Chemical synaptic transmission occurs in the following sequence. (1) Action potential arrives in neural terminals from axon hillock; (2) Voltage gated Ca2+ channels open and extracellular Ca2+ flows into synaptic button; (3) Increased [ Ca2+ ]i causes exocytosis of transmitters in the synaptic vesicle into the synaptic cleft; (4) Neurotransmitter diffuses across synaptic cleft and binds to receptors located on the postsynaptic membrane; (5) The binding of neurotransmitter opens ligand-gated ion-channels, generates ion current and produces EPSCs or IPSCs; (6) Transmitter is removed from the cleft and the opened postsynaptic ion channels close and the postsynaptic neuron is activated or inhibited.

The characteristics of chemical synaptic transmission include: (1) Morphological and functional plasticity; (2) One-way conduction; (3) Synaptic delay; (4) Summation; (5) Changes in rhythmicity; (6) Sensitive to environmental changes.

5. What is the difference between ionotropic and metabotropic receptors of neurotransmitters?

Ionotropic receptors, forming an ion channel pore, are typically the targets of fast neurotransmitters and their activation or inactivation results in opening or close of ion channels and changes in ion movement across a membrane. The effect can be either positive or negative, specifically a depolarization or a hyperpolarization respectively. Examples of ionotropic receptors are AMPA, NMDA and Kainate types of glutamate receptors, GABAA, and GABAC types of GABA receptors and nicotinic (N) acetylcholine receptors.

Metabotropic receptors, or G protein-coupled receptors, are the largest family of receptors that sense several hormones and slow transmitters. They are composed of seven transmembrane alpha helices. They are indirectly linked with ion channels on the plasma membrane of the cell through signal transduction mechanisms, often G proteins and the associated enzymes, gene transcription. Examples are group I, II, III of metabotropic glutamate receptorsGABAB receptordopamine receptors, muscarinic (M) acetylcholine receptors and adrenergic receptors.

6. Briefly describe the functions of cholinergic and adrenergic receptors in PNS?

Nicotinic acetylcholine receptors are present in neuromuscular junctions (Nm type), activation of which causes the contraction of skeletal muscles by way of end-plate potential (EPPs). Nn type receptor at autonomic ganglia causes depolarization and results in postganglionic impulse. Nicotinic receptors (Nm) in the adrenal medulla cause the release of catecholamine. Postganglionic targets of the parasympathetic nervous system include smooth muscle, cardiac cells and glands;activation of muscarinic acetylcholine receptors on them causes contraction of smooth muscle and increase in excretion but inhibition of cardiac activity. Noteworthy is that sweat glands also receive excitatory cholinergic innervations of postganglionic sympathetic neurons.

The adrenergic receptors are targets of the catecholamines, especially norepinephrine (noradrenaline, mainly targeting alpha-receptors) and epinephrine (adrenaline, mainly targeting beta-receptors).

The activation of adrenergic receptors generally stimulates the sympathetic nervous system and cause the fight-or-flight response, which includes dilating the pupil, increasing heart rate, mobilizing energy, and diverting blood flow from non-essential organs to skeletal muscle.

7. What is the difference between local currents and action potentials?

Changes in the ionic currents following the binding of neurotransmitters to their receptors also change membrane potential of excitable cells. The initial local currents are graded in magnitude, have no threshold or refractory period, cause either depolarization (EPSPs by glutamate) or hyperpolarization (IPSPs by GABA), and can be summed up. When a depolarization reaches a threshold level, action potential occurs, which is All-or-None with a refractory period.

8. How do you explain the occurrence of presynaptic inhibition?

Inhibition of synaptic transmission occurs due to reduced release of neurotransmitters at presynaptic terminals where membrane potential is partially depolarized or releasing machinery for neurotransmitters is inhibited.

9. What is a reflex and what is the difference between conditioned and unconditioned reflex?

Reflex is an involuntary and instantaneous movement in response to a stimulus.

Reflexes can be divided into conditioned reflex and unconditioned reflex according to the source (i.e. inherent or learned), complexity, loci of the reflex centers (involvement of the cerebral cortex or not). Unconditioned reflex is an instinctive reflex not dependent on previous learning or experience, with relatively limited number, fixed patterns and at basic or low levels. Conditioned reflex is an advanced nervous activity gradually developing in human's life through experience or learning, relatively flexible with unlimited number.

10. What is the physiological feature of sensory receptor? Illustrate them using the visual sensation.

1) Adequate stimulus: Each type of receptors is highly sensitive to one type of stimulus. Light stimulus to the cone and rod cells.

2) Transducer function: The transformation of one type of energy into another form of energy or nerve pulses. Retina converts light to the action potential in ganglion cells.

3) Sensory coding: Sensory receptors transfer the stimulating messages into the frequency of spikes while transducing external stimulus to action potentials.  Strong light causes higher firing rate of optic nerves. 

4) Adaptation: When a maintained stimulus of constant strength is applied to a receptor, the frequency of the action potential in its sensory nerve declines over time. Long time exposure to strong light causes reduction of firing rate (or getting into dark room causes reduced firing rate).

11. What is the difference between the specific and non-specific projection systems?

The neural pathway involving the specific sensory relay nucleus of the thalamus and its projection to specific regions of the cerebrum is named as specific projection systems. Nonspecific  projection system refers to the neural pathway involving the nonspecific sensory relay nucleus of the thalamus and its projection to cerebral cortex. The two systems are different in pre-thalamic sensory afferent pathways (along specific pathways vs. in reticular formation), relay neuronal groups in the thalamus (I & II vs. III in internal medullary lamina), projection from thalamus to the cerebral cortex (point-to-point vs. diffusive), feature of sensation (specific vs. non-specific), and functions (generate output vs. maintain consciousness).

12. What is the representative feature of the primary somatosensory areas in the cortex?

1) Each side of the cortex receives sensory information from the opposite side of the body; 2) Sensory projection in an inversed order except head and face; 3) The degree of representation is proportional to the fineness of sensation.

13. What is pain and what is the feature of visceral pains?

Pain is a kind of tissue injury-associated unpleasant sensation and emotional experience, and the pain-evoked “tissue injury” is either actually present or potential. It is mediated by the nociceptor and does not adapt to the nociceptive stimulus. Different from somatic pains, the visceral pain has the following feature. 1) Often caused by mechanical stretch, spasm, ischemia and inflammation; 2) Poor localization; 3) Slow onset but long-lasting; 4) Sensitive to expansion and stretch (for gastrointestinal organs) but not to cut and burn; 5) Easily cause unpleasant emotional response accompanying with disorders of autonomic nervous system.

14. What is referred pain?

Referred pain is a type of pain perceived at a location other than the site of the painful stimulus and often originating from distant visceral organs but perceived as coming from skin. The corresponding dermatomes of the body wall have their neuronal cell bodies in the same dorsal root ganglia and synapse in the same second order neurons in the spinal cord segments as the general visceral sensory fibers from the influenced visceral organ. The CNS does not clearly discern whether the pain is coming from the body wall or from the viscera, but it perceives the pain as coming from somewhere on the body wall.

15. To see near objects, what kinds of reflexes are necessary?

When eyes see an object nearer than 6 meters or moving closer, three reflexive visual responses are elicited, i.e. convergence, which makes the near object fall on the corresponding points of the retinas of two eyes; accommodation of the lens, which brings the object into focus; and pupillary constriction, which increases the depth of field and sharpens the image on the retina.

16. What is the difference between rod and cone cells of the retina in vision?

The retina is composed of two types of photoreceptor cells Rods and Cones. The Rods is mainly located in periphery of retina; responsible for night vision but could not detect details and color images. Cones are mainly located in fovea and best in detecting bright light; they enable us to see fine detail and are responsible for color vision

17. How does the Cochlea determine the frequency and loudness of a sound in Traveling Wave Theory?

The cochlea in the inner ear is a spiral-shaped, fluid-filled tube. It is divided lengthwise by the organ of Corti. Inside the organ of Corti is the basilar membrane, a structure that vibrates when waves from the middle ear propagate through the endolymph. The basilar membrane has the feature that each frequency has a characteristic place of resonance along it. Characteristic frequencies are high at the basal entrance to the cochlea, and low at the apex. Basilar membrane motion causes depolarization of the hair cells, and the amplitude of vibration of the basilar membrane and the number of hair cells involved determine the magnitude of depolarization, thereby the loudness of a sound. However, the hair cells themselves do not produce action potentials but release neurotransmitter at synapses with the fibers of the auditory nerve to elicit action potentials. Thus, the patterns of oscillations on the basilar membrane are converted to spatiotemporal patterns of firings which transmit information about the sound to the brainstem.

18. What is the relationship between lower motor neurons, upper motor neurons, and basal ganglia and cerebellum in neural regulation of motor functions?

After integration of sensory signals in local neuronal circuit and communication between sensory cortex and motor cortex, the primary motor cortex issues descending command from through pyramidal tract or corticobulbar tract motor neurons in the spinal cord and brainstem to initiate a movement. In this process, the motor cortex interacts with the basal ganglia closely through the corticostriatal pathways to execute patterned motor activity. By contrast, the cerebellum can participate in the motor control by motor learning and muscle coordination while maintaining balance, muscle tone and posture through its connections with the cerebrum, vestibular nucleus and spinal cord. Finally, the excitation of alpha-motor neurons causes contraction of muscles in the same motor unit by eliciting endplate potential and action potential with the assistance of gamma-neuronal activity.

19. What is the general functional feature of the sympathetic and parasympathetic nerves?

1Sympathetic and parasympathetic base tone; 2Two systems possess different functions that are often opposite but coordinative in a specific process;  3Their physiological effects are largely modulated by functional state of the effectors 4Sympathetic system often responds by mass discharge, and makes the body adapt strong changes in the environment 5Parasympathetic system usually causes specific and localized response, promotes digestion, excretion and reproduction, stores energy and thus makes the body rest, recover and protected; 6Intrinsic nervous system, such as enteric nervous system  can either respond to stimuli independently and  receive innervations of the autonomic nervous system.

20. What are the vegetative and endocrine control functions of the hypothalamus?

1) Cardiovascular regulation; 2) Regulation of body temperature; 3) Regulation of body water; 4) Regulation of uterine contractility and milk ejection from the breast; 5) Gastrointestinal and feeding regulation; 6) Hypothalamic control of endocrine hormone secretion; 7) Others: neuroimmune, homeostasis, etc.

22. What is instinctive behavior?

Instinct is the inherent disposition of a living organism toward a particular behavior under the driving of desire or motivation. It includes fighting and flight, eating, sucking and drinking, parenting and bonding, sexual behavior, sleep and awakening, grasping and exploring, crying, and facial expressions, etc.

23. Briefly describe the features of α, β, θ and δ forms in the EEG.

1) Alpha wave: Low-amplitude (20 ~100 μ V), slow wave (8-13Hz), appearing spindle shape, indicating an “idling” brain; recorded from occipital regions; indicating awake, relaxed, with eyes closed.

2) Beta wave: Less synchronized, high frequency (14-30Hz), low amplitude (5-30 mV), strongest from frontal and parietal lobes near precentral gyrus, produced by intensive mental activity.

3) Theta wave: In 4-7Hz, 100-150 μV; recorded from temporal and occipital lobes; common in newborn, sleepy in adult.

4) Delta wave: Lower frequency (0.5-3 Hz), high-amplitude (20-200 μ V) waves; obvious in temporal and occipital lobes; common during adult sleep and in infant; in awake adult indicates brain damage.

24. What happens to the production of melatonin when light is off, and why?

When light is off, increased activity of the suprachiasmatic nucleus and then the paraventricular nucleus increase melatonin production in the pineal gland by increasing sympathetic input and norepinephrine action via superior cervical ganglion, thereby turning on a sleep gate and causing sleep.

25. What is feature of Rapid eye movement (REM) Sleep and Non-rapid eye movement (NREM)?

REM sleep is also called paradoxical sleep, desynchronized sleep, appearing low-amplitude, high-frequency oscillations of EEG. It appears active dreaming and active bodily movements, but muscle tone is exceedingly depressed.

NREM sleep appears decrease in both peripheral vascular tone and vegetative functions with high-amplitude, low-frequency waves of EEG.

26. What are the neurochemical mechanisms underlying different types of memory?

Memory is the process by which information is can be divided into Short-term memory (seconds or minutes), intermediate long-term memory (days to weeks) and long-term memory (years to lifetime). Correspondingly, short-term memory is associated with the circuit of reverberating neurons and presynaptic facilitation or inhibition; intermediate long-term memory is based on chemical changes in the presynaptic terminal or postsynaptic neuronal membrane; and long-term memory is related to structural changes in synapses, number of neurons and their connectivity.


Functions of the Nervous System-Brief question III



Functions of the Nervous System-Review Questions with Reference Answers

Physiological Courses for International Students of Class 2016