Physiology Tests with Answers: 50 Questions for Exam Preparation

Memory traces (engrams) are most prominently manifested as facilitated impulse propagation and altered responses upon repeated presentation of the same stimulus.

The neuromuscular synapse has a relatively low lability (frequency of impulse transmission) compared to nerve fibers and is capable of transmitting about 50–100 impulses per second.

Inhibition is an active neural process that results in the attenuation or suppression of excitation. It protects nerve cells from exhaustion and ensures the coordination of reflex activity.

Osmotic pressure and hydrogen ion concentration (pH) are determined by the physicochemical properties of solutions, so shifts in these parameters are classified as physicochemical stimuli.

The critical level of depolarization is traditionally designated as E_cr (or E_crit).

The temporal bone has the minimum thickness and the best acoustic transparency, which is why ultrasound probes in echoencephalography are placed primarily in the temporal regions.

The delay in the conduction of excitation in the CNS is caused by synaptic delay — the time required for neurotransmitter release, diffusion, and interaction with receptors.

According to P.K. Anokhin's theory of functional systems, the integrative activity of a neuron begins with the convergence of various afferent excitations on its soma and dendrites. This gathers information for subsequent intracellular processing and decision-making.

Somnogenic structures include the synchronizing apparatuses of the medulla oblongata, pons (raphe nuclei), and non-specific thalamic nuclei, which inhibit the ascending activating influences of the reticular formation.

The tone of nerve centers represents a state of constant moderate background excitation of neurons even in the absence of explicit external stimuli.

Adenylyl cyclase is responsible for synthesizing cyclic AMP from ATP; therefore, its inhibition by inhibitory G-proteins (Gi) leads to a drop in intracellular cAMP concentration.

Dopamine released by the hypothalamus acts as a prolactin-inhibiting factor (PIF), continuously suppressing prolactin secretion by adenohypophyseal lactotrophs.

Pro-opiomelanocortin (POMC) is a complex precursor protein that is cleaved by specific enzymes into a series of active peptides, including adrenocorticotropic hormone, melanocyte-stimulating hormone, and endogenous opiates (endorphins).

Cyclic AMP acts as a second messenger and allosterically activates cAMP-dependent protein kinase (protein kinase A), which then phosphorylates intracellular proteins.

In target tissues, deiodinase enzymes remove one iodine atom from thyroxine (T4), converting it into triiodothyronine (T3), which has the highest affinity for nuclear receptors.

Vital capacity is the maximum volume of air exhaled after the deepest possible inhalation, and is composed of the tidal volume, inspiratory reserve volume, and expiratory reserve volume.

The sinus nerve (Hering's nerve) branches off the glossopharyngeal nerve (CN IX) and transmits afferent signals from the chemo- and baroreceptors of the carotid sinus to the medulla oblongata.

Full inspiratory neurons generate action potentials continuously throughout the entire phase of inspiration, producing a progressive contraction of the respiratory muscles.

Functional residual capacity (FRC) is the volume of air remaining in the lungs after a quiet expiration, consisting of the expiratory reserve volume (ERV) and residual volume (RV).

Heymans' isolated perfusion method allows solutions with a specified gas composition to be delivered to the chemoreceptors while recording reflex responses of the organism via preserved afferent neural pathways.

Homeostasis maintains the constancy of the physical and chemical properties of the internal environment, creating optimal and stable conditions for cell function.

According to the classical physiological concepts of P.K. Anokhin, all functional systems of the body and homeostatic mechanisms are ultimately directed at maintaining tissue metabolism optimal for cellular activity.

Maintaining specific constants (temperature, pressure, pH) is merely an intermediate step. The ultimate useful adaptive result of all functional systems' activity is the creation of optimal conditions for normal cellular metabolism.

The term "homeostasis" to denote the relative constancy of the body's internal environment was introduced by the American physiologist Walter Cannon in 1929.

According to P.K. Anokhin's theory of functional systems, general homeostasis is maintained through the coordinated interaction of numerous different functional systems of the body.

Evaporation of moisture in humans occurs constantly from the skin surface (sweat, perspiratio) and from the mucous membranes of the upper respiratory tract during breathing.

The maintenance of constant body temperature (thermoregulation balance) is ensured by a set of physiological reactions that regulate the intensity of heat production in the body and heat loss to the external environment.

Isothermia is a specific case of homeostasis representing the ability of warm-blooded animals and humans to maintain the temperature of the body 'core' at a relatively constant level regardless of ambient temperature fluctuations.

The posterior nuclei of the hypothalamus serve as the heat production center. Their destruction deprives the body of the ability to adequately respond to cold (via shivering and vasoconstriction), leading to a drop in body temperature — hypothermia.

The ultimate adaptive result of the thermoregulation system is the maintenance of the optimal core body temperature necessary for the stable progression of enzymatic and metabolic reactions.

According to P.K. Anokhin's theory of functional systems, a discrepancy between the parameters of the actual result and the parameters of the action acceptor (mismatch) triggers an orienting and exploratory reaction.

The action acceptor is formed on the basis of a neural model of the expected result. Prolonged circulation (reverberation) of nerve impulses through closed neuronal circuits allows this model to be maintained until retrograde/feedback afferentation about the actual result is received.

The concept of functional systems postulates the principle of isomorphism — the universality of systemic architectonics for behavioral acts of any level of complexity, from simple reflexes to higher mental activity.

Negative emotions arise when there is a mismatch between the expected and actual result or when there is a deficiency of information. They mobilize the body's energy resources and stimulate the search for new ways to overcome obstacles and satisfy the need.

Reverse afferentation carries information about the parameters of the achieved result to the action result acceptor, where it is compared with the previously formed neural model.

In the theory of functional systems, during hierarchical quanting of behavioral activity, the achievement of the final useful adaptive result is attained through the successive-parallel realization of intermediate system quanta.

Sensory aphasia (Wernicke's aphasia) is characterized by a lesion of the posterior third of the superior temporal gyrus of the left hemisphere, in which the ability to understand heard speech is lost while hearing is preserved.

When Wernicke's area (the sensory speech center) is damaged, the patient loses the ability to recognize the meaning of words, which disrupts the understanding of both external and internal speech. At the same time, the physical ability to produce sounds and words (motor function) is preserved.

In P.K. Anokhin's theory of functional systems, emotions act as a mechanism that constantly evaluates the success of satisfying the dominant need at all stages of a behavioral act.

In the physiology of higher nervous activity, thinking is viewed as the highest form of reflection of reality and a purposeful process culminating in the formation of a thought or conceptual model.

The Latin name n. vagus translates to the vagus nerve (X pair of cranial nerves).

The feeling of satiety is formed not only through humoral factors (glucose, peptides), but also due to powerful afferent impulses from the mechanoreceptors of a full stomach (sensory satiety). When the stomach is empty, neural signals of hunger dominate over humoral factors of satiety.

The peripheral theory (Cannon and Carlson's "empty stomach" theory) attributes the sensation of hunger to mechanoreceptor impulses originating from "hunger" contractions of the empty stomach.

Nutrient levels can vary within wide ranges depending on food intake and energy expenditure; therefore, they are classified as plastic constants, unlike rigid constants (e.g., blood pH).

I.P. Pavlov introduced the concept of the physiological center as a complex functional system. Its elements are distributed across different levels of the central nervous system, from the brainstem to the cerebral cortex, and work together to ensure goal-directed feeding behavior.

Karl Lashley's principle of equipotentiality states that various regions of the cerebral cortex are, to a certain extent, equivalent regarding memory and higher functions; therefore, the degree of deficit depends primarily on the volume of destroyed tissue.

Post-tetanic potentiation manifests as prolonged facilitation of synaptic transmission following high-frequency stimulation. This phenomenon of synaptic plasticity is considered a fundamental cellular mechanism for the formation of short-term and long-term memory.

The physical memory trace formed in the nervous system during learning that stores information for subsequent reproduction is called an engram.

Short-term memory ensures the retention of information for a period ranging from a few seconds to tens of minutes due to the reverberation of nerve impulses along closed neural circuits.

A dynamic stereotype is a stable system of conditioned reflexes formed through the repeated application of the same stimuli in a strict sequence. This ensures the automation of skills and relieves conscious load.