Physiology I.pdf

Protocol E6 Nerve centers and their properties 1. Introduction. A nerve center is a group of neurons that participates in the regulation of a certain reflex or a certai...

Protocol E6 Nerve centers and their properties 1. Introduction. A nerve center is a group of neurons that participates in the regulation of a certain reflex or a certain function. The nerve cells that make up the nerve center can be located in different parts of the CNS (for example, the neurons of the respiratory center). Therefore, the nerve center is a physiological rather than an anatomical concept. Nerve centers located in the lower parts of the CNS are subject to the influence of higher nerve centers. This is called the principle of subordination. The transmission of excitation in the CNS differs from the transmission of excitation in the nerve fiber because it is realized through synapses. Therefore, the transmission of excitation in CNS synapses has the following properties: 1. One way conduction – excitation is transmitted in only one direction from the afferent neuron to the efferent; from the presynaptic pole to the postsynaptic neurons. 2. Delayed conduction (neurotransmitter secretion, neurotransmitter diffusion, postsynaptic potential generation). Synaptic delay refers to the time interval that occurs between the arrival of a nerve impulse at the presynaptic terminal and its passage to the postsynaptic membrane. Typically, the synaptic delay is about 0.5ms. The causes of synaptic delay include the time it takes for a neurotransmitter to release and act on the postsynaptic membrane. 3. Rhythm transformation – as the excitation passes through, its rhythm (frequency of action potentials) changes in the CNS (from lower frequency to higher frequency and vice versa). Biological meaning of the transformation is: 1) amplification of the signal important to the organism; 2) signal reduction insignificant for the organism; 3) coordinated action of two different neurons in a reflex arc. 4. Summation of excitation – the CNS is capable of combining and amplifying several weak impulses into a single strong enough impulse that can reach the threshold and cause the excitation. Summation is of 2 types: 1. Spatial summation occurs when excitatory potentials from many different presynaptic neurons cause the postsynaptic neuron to reach its threshold and fire. 2. Temporal summation occurs when one presynaptic neuron fires many times in succession, causing the postsynaptic neuron to reach its threshold and fire. 5. Convergence and divergence. These properties are found in the chemical synapse. Convergence refers to the phenomenon of termination of signals from many sources (i.e., many presynaptic neurons to one postsynaptic neuron). Information coming from a large number of presynaptic neurons is integrated to determine the subsequent effect. Divergence – one presynaptic neuron can terminate on many postsynaptic neurons. Thus, a single impulse is converted into multiple impulses that travel to multiple postsynaptic neurons, that may travel along a single tract or across multiple tracts. This causes magnification and thus helps to amplify the impulse. Convergence in the CNS is more widespread, because there are more afferent neurons than efferent ones, thus forming the so-called total final path. 6. Facilitation – this is the “smoothing” of the reflex pathway. If a reflex is triggered for the first time, the time of its performance is longer than if the reflex is activated again, because of the time it takes to “break through” the path for the first time. This is because: A. The portion of neurotransmitters released after the first irritation increases the sensitivity of the postsynaptic membrane. B. Repeated irritation releases a larger amount of neurotransmitters. 7. Reflex after-action – continuation of the reflex after termination of afferent stimulation. The response reaction still occurs a short time after the stimulation. Why? This happens because there are many synapses in the CNS, where synaptic delay is observed, and depending on the number of synapses, the excitation reaches the effector later. t mo 18  8. Dominance. All centers are not in the same position at a given moment – there are leading centers and subordinate centers. Dominance means that leading centers can temporarily suppress subordinate centers. Depending on the conditions (season, etc.), different centers can dominate: food intake dominance, breeding dominance, defence dominance, etc. Also, there are approximately five times more afferent neurons than efferent neurons in the CNS, so the most biologically important reactions are realized first. A dominant center has four properties: 1. Increased excitation. 2. Prolonged excitation. 3. Ability to attract excitation from other excitation centers. 4. Ability to suppress excitation. 2. Tasks: 1. Watch an educational film about the physiology of CNS. 2. Write down examples that show the properties of excitation transmission in the CNS. ↳ at Least 2 EXAMPLES 3. Equipment: educational film. 4. Results. Synaptic Transmission: Description: At a synapse, the junction between two neurons, the presynaptic neuron releases neurotransmitters into the synaptic cleft. These neurotransmitters bind to receptors on the postsynaptic neuron, leading to excitation or inhibition. Property: Excitatory neurotransmitters, such as glutamate, promote the generation of action potentials in the postsynaptic neuron, while inhibitory neurotransmitters, like GABA, suppress the generation of action potentials. Spatial Summation: Description: Spatial summation occurs when multiple presynaptic neurons release neurotransmitters simultaneously onto a postsynaptic neuron. The combined effect determines whether an action potential is generated. Property: If the excitatory signals outweigh the inhibitory signals, the postsynaptic neuron is more likely to reach the threshold for firing an action potential. Temporal Summation: Description: Temporal summation involves the cumulative effect of neurotransmitter release from a single presynaptic neuron over a short period. Rapid, repeated signals can lead to excitation. Property: Even if individual signals are weak, the close succession of neurotransmitter release can summate to reach the threshold for action potential initiation. Presynaptic Inhibition: Description: In presynaptic inhibition, an inhibitory neuron reduces the release of neurotransmitters from the presynaptic terminal of an excitatory neuron. Property: This mechanism allows for fine-tuning of signal transmission. By inhibiting specific excitatory pathways, the overall level of excitation in the neural circuit can be controlled. Neuromodulation: Description: Neuromodulators are chemicals that affect the excitability of neurons. They can alter the sensitivity of neurons to neurotransmitters or influence the release of neurotransmitters. Property: Neuromodulation provides a way to regulate the overall excitability of neural circuits. For example, endorphins act as neuromodulators, influencing pain perception and mood. 19  Protocol E7 Conditioned reflex 1. Introduction. Conditioned reflexes are the highest form of adaptation functions (an automatic response established by training to a normally neutral stimulus). In order to develop the conditioned reflex, several rules must be followed: 1. The organism should be affected by two irritants – an indifferent or conditioned stimulus and an unconditioned stimulus. 2. The indifferent irritant (an irritant that will subsequently cause the intended conditioned ↑ reflex) must act first, but it must not cause a violent (exaggerated) reaction (If we first give the meat and then ring the bell, the conditioned response is not established). 3. The unconditioned stimulus acts as the second. It must be biologically stronger (dominant) and must elicit the intended unconditioned reflex response. 4. The animal must be both physically and mentally healthy. 5. The animal must be in a physiologically active state. 6. Other additional irritants should be avoided during reflex development. 2. Tasks: 1. Draw up a scheme for a conditioned reflex, as a result of which a dog salivates when it hears a certain sound signal. Bag afraid to place 2. Draw up a scheme for a conditioned reflex, as a result of which............................................. near a go is 3. Equipment: 1. Example: Dog, sound signal, food. nety late refrie from 2. Example of independent work:........................................................................... the home log , a , with experienday 3. Example of homework:....................................................................................... boy rolling far treats ove r. 4. Technique. Example 1. 1) Description. Sound signal – secretion of saliva (development of conditioned reflex). 2) Scheme. neko Fig.1. Sound signal – secretion of saliva (conditioned reflex development) 3) Result. After several repetitions, after hearing the sound signal, the dog will salivate (without seeing food). 20 Example of independent work. the street where other Day feels of the for 1) Description............................................................................................................ , walking your log on some treet that wer after while the log Doe not went to walk or becomes - a on et free tog will perk............................................................................................................................... the him O Ther. oggreiter Dog During welling 2) Scheme.................................................................................................................. dog get bitter by a aI mi I is went by don't ggrieve tog to well that lour the liver 3) Result..................................................................................................................... anymore where say Example of Homework. 1) Description............................................................................................................ boy learns to tog roll over wher given a perificcommend through repeated practice and positive reinforcement , Owner may give the............................................................................................................................... a treat out my words boy/girl" by feel like , goat which makes the good. 2) Scheme.................................................................................................................. by roll lay Owner abeys tells armond to get partine reinforcement , knows that when he the he will a treal and. - ⑳ say" D 1 - E -;- 1 -. · E 3) Result..................................................................................................................... - and Day rolls terty over for prition reinforcement und receives a treat nor words. 5. 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(shouting TeM ↓ l. * Feer barking D , z toge eto) · , L >* * Acytorin vertion ↑ ~..... - W MiLK-LET Down lock for few minutes ! a e. ↓ ·.... · > inhibited By or > · tisturbing Emotionally ⑥ simi log barking · , , I - other laut and numa naires even , musda activity and poin · notequate witter preparation Milk resins trapped in the have (socity the evali of 36  Protocol E19 Milk composition 1. Introduction. There are two types of milk: colostrum and regular milk. Colostrum, the first secretion of the mammary gland prior to parturition, provides important, and in some cases essential, components for health and survival of the neonate. Compared with regular milk, the composition of colostrum is considerably higher in solids, protein, and ash components (specifically zinc, iron, folic acid, choline, riboflavin, and vitamins A, E, and B12). It has been estimated that at birth a newborn calf only has enough energy stores, in the form of fat and glycogen, to last for approximately 18 hours without colostrum consumption. Farm animal species, such as cattle, sheep, and pigs, have epitheliochorial placentas containing six layers, thus preventing transfer of immunoglobulins from the dam to the fetus. In these species, adequate colostrum consumption is essential for survival of the neonate. The predominant immunoglobulin in these species is IgG but IgM and IgA are also present and provide the neonate with the systemic and gut‐associated immunity essential in early life. Dogs and cats have an endotheliochorial placenta that allows moderate transfer of immunoglobulins; they thus acquire immunoglobulins in utero, as well as through colostrum consumption. Immunoglobulin transfer occurs across the hemochorial placenta of species like human, monkeys, and rabbits. In rabbits, the immunoglobulin concentration in colostrum is much lower and composed mostly of IgA and IgM. In addition to immunoglobulins and other growth and development nutrients, colostrum possesses a multitude of immune proteins and cells for early immunological protection, as well as factors that enhance digestion. The quantities of the regular milk constituents can vary considerably depending on the individual animal, its breed, stage of lactation, age and health status. Herd management practices and environmental conditions also influence milk composition. The most important component of cow’s milk is fat as a source of energy. This fat is vital for the young animals due to this nutritional value as it provides a considerable energy contribution. On the other hand, lactose is the main carbohydrate present in mammalian milk. Lactose is composed of glucose and galactose. Regarding proteins, the main one is casein, which contains essential amino acids. Milk salts are mainly chlorides, phosphates and citrates of sodium, calcium and magnesium. Milk contains the fat-soluble vitamins A, D, E and K and water-soluble vitamins B complex and C. 2. Tasks: 1. Write down the amounts of the main components of colostrum and regular milk of your CECA animal species. 2. Write down the amounts of the main components of formula milk/milk substitute of your CECA animal species. 3. Equipment: available literature, lecture materials, internet sources 37 4. Results. Components of milk (animal species _________________) Mark Milk type Main components Shalls to not have salatrum Colostrum sharks to not have will regular. Regular milk che rommet exhibit placented ent & , see Some , hal visparity with yolk-like a placenta (notratrophic nutrition Milk replacer alteraturena The creating a netril reale enting additional nutrients to the flust - in developing fel - that us dealoe into a planter has the fertilized egg In placental piniferous uterus well. atteches to the 5. Conclusions. Sharks, being fish, do not give birth to live young in the same way mammals do. Instead, most sharks lay eggs, and the developing embryos receive nutrients from the yolk sac rather than from a form of milk. Some sharks, however, give birth to live young through a process called viviparity, where the embryos develop inside the mother's body and receive nutrients through a placental connection. Even in these cases, sharks do not produce colostrum as mammals do. The nutrients are provided through a different mechanism, and the young sharks do not rely on milk for their early nutrition. 38  Protocol E20 Hormones that are absolutely necessary to sustain life 1. Introduction. Undoubtedly, all of the hormones are very important for the normal functioning of the body. However, there are hormones, the lack of which disrupts vital processes and the animal dies. You have received information about these hormones in lectures and laboratory works. However, it is important to gather this information and understand what is the main cause of death in the absence of the hormone in question. 2. Tasks: 1. To find out which hormone deficiency can cause the death of an animal. 2. Briefly describe the regulation of the production and release of these hormones, paying particular attention to both stimulating and inhibiting factors. 3. To find out the reasons why the lack of each hormone causes a fatal outcome (cause of exitus lethalis). 4. To find out how to avoid the situation when the reduced secretion of these hormones is provoked, or the so-called resistance of the relevant hormone is formed in the body (a situation where the action of the relevant hormone is inhibited). 3. Equipment: available literature, lecture materials, internet sources. 4. Results. animal. of lightin a the both on t aWhether defiery on s ave porthormone glaimurgutfloat 1) Inlin ald-erase al - · selec stat wells ofpetlyi , eg a ba a blood intential Can'tobation , - Normal are vareled it the. by antimates vil I, which indus at let i n e tomim 2) Pratharnone - Af the boue ac tu wes Malmation sells in e relates So from , ba parsfollicular , posthyse glad the · Thih which normal and irbibil -- ta from the. vels book bes las on of P tH increases bas e are 3I When blood relium - twilShing nothing - PARATHORMON E inhibit releas of PTH - multine e a , / emery · 1 - a , feel. if either be 4) So bla Com beels breathing zeice -on porclyze llg ,. 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