Olfactory (smell) analizator

It is a sensory modality mediated by chemoreceptors of olfactory mucosa.

Primary sensations of smell:

1. Camphoraceous.

2. Ethereal.

3. Floral.

4. Musky.

5. Pepperminty.

6. Pungent.

7. Putrid.

Olfactory membrane or mucosa lies in superior part of each nostril. Medially it folds downwards over surface of septum and laterally it folds over superior turbinate.

Olfactory cells:

1. These are receptor cells for smell sensation.

2. Mucosal end of each olfactory cell forms a knob from which 6-12 olfactory hairs or cilia project into mucus that coats inner surface of nasal cavity.

3. Cilia react to odors in air and stimulate olfactory nerve.

4. Glands of Bowman are also present among olfactory cells. They secrete mucus.

Odorants (smell-producing substances) have 3 characteristics:

1. Substance must be volatile - so that it can be sniffed into the nostrils.

2. Substance must be water soluble - so that it can pass through mucus to olfactory cells.

3. Substance must be lipid soluble – so that it can penetrate lipid bilayer of olfactory cells to stimulate them.

Olfactory adaptation – olfactory sensation decreases very rapidly with continual exposure to an odorant. Nerve fibers from olfactory region of brain pass backward along olfactory tract of inhibitory granule cells of olfactory bulb, which causes olfactory adaptation.

2 main theories of smell:

1. Physical theory – according to this theory, physical shapes of odorant molecules determine which olfactory cell will be stimulated.

2. Chemical theory – odorant molecules bind chemically to specific protein receptors in membrane of olfactory cilia and increase permeability of olfactory ciliary membrane so, receptor potential in olfactory cells is excited and action potential (impulse) is produced in olfactory nerve fiber. So, main factor is stereochemistry of smell substances. This is space accordance of smell substances to receptor locuses shape on surface membrane of olfactory microvilli.

Olfactory cells are primary sensor cells. They send axones into brain from their basal pole. These fibers forme thick fibers (olfactory fibers) under sensor epithelium coming to olfactory bulb. There occurs primary processing of sensor information. Bulb generates rhythmic potentials. Axones of cells compose olfactory tract directly or indirectly transmitting olfactory sygnals into many braci regions particularly into olfactory bulb of opposite side in structures located into subcortical structures of anterior brain, limbic brain, hypothalamus.

Lecture 8

Organism integrative activity and behavioral physiological bases (the higher nervous activity, behavioral congenital and acquired forms, memory, thinking and speech).

Human behaviour includes 2 reactions types:

1. genotypic – it is based on genetic proggramme;

2. phenotypic – it is linked with genotype, environmental conditions interactions or it may be individually aquired, based on study.

Hereditary behaviour forms

These are unconditioned reflexes, individual and of species, stereotypic organism reactions to external and internal stimuli performed by CNS. Main distinguishing feature of such reflexes – they determine reflexes expressed without preliminary study. For example, stomach juice releasing at food coming into oral cavity, hand taking off at noceoceptive irritation, winking while air coming into one’s eye. Try to check them up in new-borns and you’ll see that they are performed without any study.

Unconditioned reflexes – are instincts; they are fundamental phenomenon in highest nervous activity forming. One can differentiate 3 types of them:

1. Vital – they provide individual and species organism preserving:

· alimentary;

· drinking;

· dream;

· defence et al.

They are directed to organism forces economy; their disorders lead to individual’s physical death.

2. Zoo-social – they may be realized only by interconnection with other individuals of the same species:

· sexual;

· paternal;

· territorial;

· of groups et al.

3. Reflexes of self-development – they are oriented to new spatial-temporary environments discovery; addressed to future:

· investigations;

· reflex of freedom;

· plays;

· mimicry et al.

Instincts organization

It is rather complicated. External (key) stimuli are triggers in their realizing. Every stimule switches stereotypic reactions on as a rule consequent motor acts the result of which is any reaction performance. One can differentiate 2 categories of brain reflectory processes:

· Of preparation – triggering, motivational. Their activity are connected with less specific reactions and is controlled by organism internal needs in more extent. Motivational reflexes are also called drive-reflexes (from "drive”-“motive”). They are hunger, thirst, fear, fury. Their main peculiarity is motor activity general mobilization.

· Efferent – are linked with multiple specific reactions onto stimuli.

Each unconditioned reflex is characterized by definite behaviour. For example, hunger reaction initiates food-getting reactions expressing in motor anxiety and sensor systems activation. Ending phase of food-getting behaviour is efferent reflex – mastication and swallowing. Efferent reflex triggering (alimentary one in this case) is realized with participation of sensor (olfactory, gustatory) reception, emotional-motivational aspect is important for this. Food itself as unconditioned stimulus causes congenital emotinal reaction – gustatory and olfactory receptors excitement.

Unconditioned reflexes are congenital, species, relatively constant, reactions occuring as an answer to definite receptive field irritation. Brain stem and subcortical structures are essential for their realizing. They are remained after cortex removal although naturally they are realized at its participation under norma too.

Acquired behavioural forms

This is individual experience aquirement due to environment variation. Associative or conditioned experience aquirement takes special place among these behavioural forms. Conditioned reflexes are formed at definite conditions of organism onthogenesis and are disappeared at their absence comparatively to unconditioned reflexes.

The earliest form of new-borns adaptation are natural conditioned reflexes onto feeding time and onto food as sucking movements. Artificial conditioned reflexes begin their formation later than natural.

Acquired reactions constant chage occurs in course of life. One conditioned reflexes are fixated, others disappear quickly and then after several time are restored. It is connected with conditioned reflexes inhibiting appearence or working out.

One can differentiate conditioned reflexes inhibiting 2 main types:

· External – unconditioned.

· Internal – conditioned.

External inhibiting – appears and that’s why it is congenital. It appears when in course of conditioned stimulus action onto organism other stimulus acts onto organism (external). It may be very strong (car sygnal while crossing the street) or weak (rain drops or train wheels thud). These stimuli come at definite stage out off limits of their possible perception with corresponding nervous structures and inhibiting occurs due to this. Such inhibition is often called out-limited. External inhibition is also indicated as such inhibition when unusual stimulus action. For instance, someone comes in lecture hall (rector, dean), orientive reaction appears first, then – conditioned reaction inhibiting (in this case such conditioned reaction is the lecture writing) and this reaction stoppes during the stimulus action.

Uncondioned external inhibiting is expressed in children from the early beginning of conditioned reflectory activity.

Internal inhibiting – is aquired one and it has different forms of expression.

1. Extinctive – is produced after conditioned stimulus support cancellation (baby has salivation to mother breast, but after cancellation out off mother’s breast this reflex disappears because it becomes useless).

2. Differentiated - it encourages the differentiation of sygnals similar by nature. For example, sounds differentiation in course of lection delivering. There are different sounds during this time – lecturer voice, knocking on doors in corridor, peoples’ steps, transport sounds et al. But, we hope, you have answer reaction to essential sounds in this moment - lecture’s voice. Thus, differentiated inhibiting produces to other sounds. Significance of this inhibition forme: we perform analysis of surrounding world due to it.

3. Delaying – is formed under the situation when conditioned stimulus goes before support and the latest one is late. Example. You set your alarm clock to the definite time for getting up. It is ringing in the morning. You hear it but don’t react to it, i.e. don’t get up and do it only at unconditioned stimulus action (parents or friends voice, your blanket is taken out off you).

Conditioned inhibiting (delaying and differentiating) appears in 2,5-3,0 months in children.

Thus, all inhibiting types, mentioned above, stop conditioned reflexes. Conditioned reflexes are formed not only by cortex but also by subcortical structures. Inhibiting is also formed by cortex but it appears in subcortex. Mosaic of exciting and inhibiting in CNS, codtioned and unconditioned reflexes, having been fixated in definite consequence – this is the base of one or other behavioural act.

 

Memory - is one of basic CNS features. Memory is responsible not only for information fixating, its keeping but also it includes mechanisms of its retention and reproduction. Memory is tightly connected with study. Study provides constant knowledge addition, new experience aquiering. Memory and study – are 2 sides of one and the same process. They have one common feature: necessity in information repeating (it is not occasionally to hear that repeating is study mother). Memory may be genotypical (congenital) - it is responsible for unconditioned reflexes, instincts formation. Phenotypical memory – is processing and preserving of information aquired in course of individual onthogenesis.

Human being has at least 3 types of sensory memory:

· iconic (instant)- supports exact and complete picture, percepted by eyes in course of 0,1-0,5 sec. Similar memory percepted by ears is often called as eichoric memory. It may transform into

· Short-termed or working memory that realizes current behavioural and thinking performance in course of seconds, minutes after phenomenon and subject action. It is significant for information selection (“morning is wiser than evening”). It is disturbed in course of ageing.

· Long-termed – keeps big informational volume. All that is kept in our memory more than 1 minute is transformed in long-termed memory system in course of so-called consolidation (nore often - during dream) where it is kept in course of hours, days, years, sometimes- in course of all individual’s life.

Memory physiological mechanisms

Retention and reproduction memory mechanisms are not yet clear. But fixating mechanisms are explained by some theories. One group of theories consider that memory has cellular-molecular base. There also exist data that imaging fixation is based on stable changes of synaptic transmission. Initial information is kept due to structural synaptic changes. Further, after these synapses activation memory content may be reproduced. That’s why memory depends on such main factors of synaptic transmission as mediators – acetylcholine, noradrenaline, serotonine; neuromediators - cAMP, cGMP and row of metabolites.

There also exists other theories group based on informational molecules participation (macromolecules – proteins, nucleic acids). We have great number of factors proving that study and memory are linked with aquired behavioural forms encoding in informational macromolecules (RNA, neuropeptides).

Scientists also propose immunochemical memory way based on possibility of formation substances playing the role of antigene for antibody in course of memory developmemt.

Other memory classification according to reasons underlying its development:

· imagionational – keeping in memory and reproduction of one percepted vital subject;

· sensory-imagionational - it operates representatives connected mainly with activity of one or other analizator- visual, auditory, gustatory, olfactory (the strongest among them), motor memory;

· emotional - the strongest among all memory types - reproduction of emotional state experienced before at stimulus new (repeated) action;

· verbal-logic - memory on verbal sygnals indicating objects or one or other events;

· logic-verbal – operates terms, concepts (is the highest memory type).

In course of receiving knowledge you must use all memory types. Besides, you know that people are divided into several groups according to their predominant memory: audials (ones with predominant auditory memory), visuals (visual one), kynaesthetics (cynaesthetics) which need in touching, delicious food, increased amount of sex, i.e. have enforced skin sensitivity (so have sominant emotional memory) and so on. As psychologists and physiologists tell it’s better that both husband and wife belong to 1 group.

Naturally, that it’s impossible to remember everything. Is it good or bad? Forgetting process – is a natural physiologic reaction. We can’t keep in our memory all information we ever delt in our everyday life. There are 2 reasons of this. First, forgetting is a passive inhibiting or steps weakening with time. It is developed by extinctive inhibition way: repeating is absent, necessity in information is absent and it is naturally extincts. Second, it is also active process: new information comes despite old one. Such phenomemon is called interpherence. The more we recognize new, the less old information is in our brain. It doesn’t mean that old information is not necessary. No, it is simply used to the construction of new one and it is changed by it at a new level. It also occurs under biologically active substances influence in human organism. Endorphines and encephalines, vasopressine improve memory, decrease conditioned reflexes extinction, but oxytocine disturbs long-termed memory particularly aquired skills.

Thus, memory and study need in repeating. Recognizing way - through repeating. Speech and thinking are essential for memory and study development.

 

Thinking and speech - are the complicated types of nervous activity. Thinking- is any phenomena and subjects common features reflection in human consciousness as well as connections between them. One can differentiate several stages in course of human thinkin g (they have different expression in different people):

· analysis- differentiation of similar stimuli; it is originated from receptors; differentiated inhibition is under its base; simple analysis (single stimuli differentiation) is a characteristics of animals; simple analysis has more significant development in animals in comparison to human beings (sounds, smells differentiation and so on); both simple and complicated analysis are features of human being; complicated analysis is information differentiating in course of irritators combines action;

· synthesis – stimuli uniting, the example of which is conditioned reflexes of the highest orders; animals have simple synthesis - they can develop conditioned reflexes of only 2^nd -4^th orders; human beings- complicated synthesis- they can develop conditioned reflexes till 10^th or even more orders;

· comparison- search of similarity and differentiation features in subjects and phenomena; everything is recognized in course of comparison;

· summarizing – subjects and phenomena common features uniting as a result of which we can have new regularity occurence;

· classification- facts distribution on groups, subgroups, phases, classes (for instance, disease course - on stages).

 

Speech is essential for thinking formation. Word is a powerful social stimulus. It names different subjects and phenomena of surrounding world. Thus, human being has not only first sygnal system (stimuli action to sensor entrances through sense organs - food smell and its search) like animals but also second sygnal system (word, signifying influence). Though word is a real physical stimulus (auditory) it significantly differs because concepts about subjects and phenomena are reflected in it.

Human nervous system integrative activity is realized not only on the basis of direct sensations and impressions (concrete thinking) but also by operating with words, where word represents thinking and human intellectual abilities and functions. World picture becomes more perfect, more summarized, more differentiated due to word (abstract thinking). It is expressed in human being when he can abstract terms out off concrete reality.

Thus, thinking is a speech in its essence but speech without sounds, it is the expression of speech mechanism, writing activity, in deaf-and-dumb – of gestures mechanism.

Verbal stimuli understanding is linked with the functions of dominant speech hemisphere – left - it mainly participates in analytic processes, it is the base for logic thinking, it determines speech activity, its understanding, work consctruction with verbal stimuli. Right hemisphere also has speech functions. It allows concrete-imagional thinking, it deals with non-verbal material, musical abilities are linked with it. Left hemisphere dominates right one in its ability to understand speech. Speech fucntions in right-handed people are mainly located in left hemisphere and only in 5% of them – in right one. In 70% of left-handed speech center is located in left hemisphere like in right-handed and in 15% of left-handed speech center is situated in right hemisphere.

Thinking and speech are important constituents characterizing human mind. Mind variation is its criterium.

What makes one person more intelligent than another? What makes one person a genius, like the brilliant Albert Einstein, and another person a fool? Are people born intelligent or stupid, or is intelligence the result of where and how you live? These are very old questions and the answers to them are still not clear.

We know, however, that jusy being born with a good mind is not enough. In some ways, the mind is like a leg or an arm muscle. It needs exercise. Mental exercise is particularly important for young children. Many child psychologists think that parents should play with their children more often and give them problems to think about. The children are then more likely to grow up bright and intelligent. If, on the other hand, children are left alone a great deal with nothing to do, they are more likely to become dull and unintelligent.

Parents should also be careful what they say to young children. According to some psychologists, if parents are always telling a child that he or she is fool or an idiot, then the child is more likely to keep doing silly and foolish things. So, it is probably better for parents to say very positive things to their children, such as “That was a very clever thing you did” or “you are such a smart child”.

Thought is material. It’s a very big power! It may be positive or negative. Human being must be kind and generous in his imaginations. Bad, negative, depressed thoughs, thoughts directed onto unhappiness encourage this unhappiness. Destructive thoughts are worse. Unfortunately, the media, especially television is very often the source of negative information that doesn’t do people happy but causes opposite reaction. Negative thoughts themselves - are main sources of our diseases in more extent than action of all microbes and viruses taken together. Think with positive categories! This is one of the most important ways of health support!!!

 

 

Lecture 9.