Behaviour - Biological bases

Biogol ic al

bases

iof behav our

Biological Bases of Behaviour.

1. Human Anatomy and physiology- Brief 2. Biosocial Aspects 3. The Evolutionary Perspective 4. Genes and Behaviour 5. Receptor-effector-connector mechanisms-

the Neural Bases of behaviour. 6. Endocrine System and Behaviour

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• The nature of psychology is bio-social.• It thrusts upon the behavioral events of

human beings.

• MAN CONSTANTLY INTERACTS WITH THE

ENVIRONMENT

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• Man consistently engages in interaction with the environment.

• Sensory nerve impulses are transducted to the brain

• Brain sends motor impulses to the organs of response.

• The effector organs produce a response which is called behaviuor.

• This brain mediated receptor effector mechanisms which produce a behaviour is called physiological or biological basis of behaviour

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• BILOGICAL BASES OF BEHAVIOUREvolutionary processGeneticsNeural bases

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Evolutionary Perspective

• Human beings (Homo sapiens) are the most developed species among the millions of organisms on earth.

• Organisms show variations among themselves and others.

• These variations are the main cause Evolution• Evolution refers to gradual and orderly biological

changes that results in species from the preexisting forms in response to the changing adaptational demands of the environment.

• EVOLUTION 6

Charles Darwin

Comparison of evolutionary change in human brain BILOGICAL BASES

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The largest brains are those of sperm whales, weighing about 8 kg (18 lb). An elephant's brain weighs just over 5 kg (11 lb), a bottlenose dolphin's 1.5 to 1.7 kg (3.3 to 3.7 lb), whereas a human brain is around 1.3 to 1.5 kg (2.9 to 3.3 lb)

Evolutionary Perspective

Evolution follows natural selection.Natural selection leads to survival of the

fittest.Fitness refers to the ability of the

organism to survive and contribute its genes to the next generation

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EVOLUTIONARY PERSPECTIVE

Landmark features in the evolutionary history of Man

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• Bip

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•En

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• Lan

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Bipedalism

• Ability to walk upright on two legs.• Hands became free to operate tools and

explore the environment.• Human beings became better adapted to the

environment.

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Movie-1

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Encephalization

• Refers to evolutionary change in structure and size of brain

• Weight of human brain is 2.3% of the body weight.(1.3 TO 1.4 Kg)

• Due to this specialized brain tissue human beings became capable of complex activities.

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Language development

• Language made human interactions much more effective than any other animal.

• Lead to cultural evolution.• Tool and medium for effective communication

• Through the biological process of evolution human beings stand at the top of the evolutionary ladder

• Evolution is a continuous process

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BILOGICAL BASES

OF BEHAVIOURENVIROMENTAL INFLUENCE ON EVOLUTIONARY TRENDS• There used to gender

based division of labor in the early human society

• Now the gender based differentiation in human society is deteriorating day by day as part of the survival of the fittest

Charles Darwin

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Sex determination

• Sex determination is based on the ‘x’ or ‘Y’ sex chromosomes present in the sperm

• The ovum contains two ‘X’ chromosomes as the sex chromosomes.

• Sex of the child entirely depend on the chromosome of the sperm cell.

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GENES AND BEHAVOIUR

• The development of human being…. Is the climax of all wonders -Conkun EG

• Human beings with all these potentials have developed from tiny threads of life called Chromosomes

• Gametic cells unite to form Zygote which contains 23 pairs of chromosomes

Human Chromosomes

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Chromosomes

• Chromosomes contain DNA in them.

• James Watson Francis crick, and Maurice Wilkins studied extensively on DNA.

• DNAs contain Genes which are the bearers of Heredity

James Watson

Francis Crick

Maurice Wilkins

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• Genes are also called the “master code”

• They contain the blue print of life.

• Sometimes there will be abnormalities in the number of Chromosomes leading to syndromes.

Down’s Syndrome

Klinefelter’s Syndrome

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• During gamete formation meiotic division occurs.

• During this process there is exchange genetic material.

• In the Zygote the genes function in a chance selection method leading to Character difference in offsprings.

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Genotype and Phenotype• The genetic make up of an organism is called

‘genotype’.• The observable characteristics of an organism

is called ‘phenotype’.• The given gene can exist in several different

forms• Change of gene from one form to another

form also can occur ,called mutation.• Mutation also leads to variation and at last

speciation Movie 1

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The science that focuses on the genetic bases of behavioral traits such as intelligence, mental

disorders etc .is called Behavioral Genetics

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NATURE AND NURTURE CONTRAVERSY

• Despite similarities in inheritance ,children differ from their parents in behavioral and psychological attributes.

• Heredity (nature) and environment (nurture) have significant role to play in the development of behavior.

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21H x E x T = Developmental Level

Socio-biology

• Socio-biology is the systematic study of the biological basis of social behavior.

• The central assumption of sociobiology is that the key purpose of human life is to pass along genes in future generation.

• The evolutionary history evidences the fact that human beings posses built in programmed behavioral predispositions. Eg. Competition, Aggression, Altruism etc.

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INHERITED STRUCTURES

• Under the guidance of heredity, organisms living in a normal environment, undergoes a process of growth involving three major sets of structures .

1. The Nervous system2. The Endocrine glands3. The Muscles First two systems are intensively studied to

understand the Biological bases of behavior

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THE NERVOUS SYSTEM

• Behavior of an organism involves the coordination of receptors, effectors and adjustors .

• Nervous system plays the role of the adjustors.

• So it is important to know nervous system in detail to understand more clearly about human behavior.

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THE

NER

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STEM

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STRUCTURE OF

NEURON

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Nerve Cell

The basic structural and functional unit of the nervous system is called a nerve cell or neuron.

Each nerve cell consists of a central portion containing the nucleus, known as the cell body, and one or more structures referred to as axons and dendrites.

The dendrites are rather short extensions of the cell body and are involved in the reception of stimuli.

The axon, by contrast, is usually a single elongated extension; it is especially important in the transmission of nerve impulses from the region of the cell body to other cells.

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Types of neuronsSensory or Afferent neuronMotor or efferent or efferent

neuronInterneuron or connector neuron

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Monitoring neural activities

• A specialized cell designed to transmit information to other nerve cells, muscle, or gland cells, the neuron is the basic working unit of the brain.

• The brain is what it is because of the structural and functional properties of interconnected neurons.

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• It contains between one billion and one trillion neurons, depending on the species.

• The neuron consists of a cell body containing the nucleus, cytoplasm, and an electrically excitable output fiber, the axon.

• Most axons also give rise to many smaller branches before ending at nerve terminals.

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BILOGICAL

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BEHAVIOUR• Neurons signal by transmitting

electrical impulses along their axons, which can range in length from a tiny fraction of an inch to three or more feet.

• A neuron is a long cell that has a thick central area containing the nucleus; it also has one long process called an axon and one or more short, bushy processes called dendrites.

• Dendrites receive impulses from other neurons.

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• These impulses are propagated electrically along the cell membrane to the end of the axon.

• At the tip of the axon the signal is chemically transmitted to an adjacent neuron or muscle cell.

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• Two types of phenomena are involved in processing nerve signals

Electrical and Chemical

• Electrical events propagate a signal within a neuron, and chemical processes transmit the signal from one neuron to another neuron or to a muscle cell.

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• Like all other cells, neurons contain charged ions: potassium and sodium (positively charged) and chlorine (negatively charged).

• Neurons differ from other cells in that they are able to produce a nerve impulse

• Nerve impulse generation has three stages• Resting potential• Generation of action potential• Propagation of action potential

Sodium Potassium pump

Action potential

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BEHAVIOURELECTRICAL TRANSMISSION

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Law governing propagation of action potential

Propagation of action potential is governed by a law called ‘All or None law’.

The intensity of the stimulus which is adequate to produce an impulse is called ‘Threshold stimulus’.

All or none law states that if cell responds it responds fully provided the stimulus is just above the threshold value.

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Refractory period

Once a nerve fiber is fired it cannot fire for a brief period of time – absolute refractory period (1/1000 sec)

It is followed by a relative refractory period during which a very strong stimulus is required to produce a new impulse.

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CHEMICAL TRANSMISSION

• When the electrical signal reaches the tip of an axon, it stimulates small presynaptic vesicles in the cell.

• These vesicles contain chemicals called neurotransmitters, which are released into the microscopic space between neurons (the synaptic cleft).

• The neurotransmitters attach to specialized receptors on the surface of the adjacent neuron.

Synapse

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• This stimulus causes the adjacent cell to depolarize and propagate an action potential of its own.

• The duration of a stimulus from a neurotransmitter is limited by the breakdown of the chemicals in the synaptic cleft and the reuptake by the neuron that produced them.

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SynapseBILOGICAL BASES

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Synaptic facilitation

• Synapse is a case of contiguity without continuity.In the case of week signals there are two types of facilitating summation taking place at the synapse.

1) Special summation: Nerve impulses from two presynaptic neurons combine together

2) Temporal summation: two nerve impulses at some intervals from same presynaptic neuron combine within the life period of the weaker signal.

Excitatory Post Synaptic Potential (EPSP) - depolarises post synaptic neuron

eg. Acetylecholine

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Synaptic inhibition

• In addition to facilitating functions at synapse ,inhibitory functions also takes place .

• Inhibitory substances hyperpolarize the post synaptic neuron, making it more negative.

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Synaptic conduction +/-

Inhibition of neuron Inhibitory Neuron

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Division of nervous system

1.PERIPHERAL NERVOUS SYSTEM.2.CENTRAL NERVOUS SYSTEM.3. AUTONOMIC NERVOUS SYSTEM

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Anatomy of PNS• PNS include cranial and spinal nerves that connect CNS with

receptors and effectors of the body.• Cranial nerves

12 pairs of cranial nerves arise from brain ( 4 pairs sensory, 4 pairs motor and 4 pairs mixed).

• Spinal nerves 31 pairs of mixed type arise from the spinal cordCervical 8 pairsThoracic 12 pairsLumbar 5 pairssacral nerves 5pairsCocceageal nerve 1 pair

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BILOGICAL BASES

OF BEHAVIOURCentral Nervous System -CNS. The Central Nervous System is that

part of the nervous system which lies within the bony case formed by the skull and the spine.

The central nervous system, which includes the brain and spinal cord, processes and coordinates all incoming sensory information and outgoing motor commands, and it is also the seat of complex brain functions such as memory, intelligence, learning, and emotion.

The brain and the spinal cord consists of this system.

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THE SPINAL CORD

It is that part of the Central neurons system which lies within the back bone .

It is composed of the grey matter and the white matter.

The grey matter consists of nerve cells nerve cells lying inside and the white matter consisting of nerve fibers lying outside completely covering the grey matter..

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Spinal cords function is two fold. In the first place it functions as a

channel of communication from the brain and to the brain. Secondly it works as an organ for effective reflex action.

Spinal cord cross section

Spinal cord

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Reflex Action

• Sudden involuntary response to stimulus is called reflex action

• The stimulus response pass through a ‘reflex arc’

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Reflex arcReflexes

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Reflex arch

• Reflex arch is a simple nervous pathway connecting a receptor and an effector. It consists of the following parts

• A) The receptors• (b) Afferent or sensory neuron• (c) Association neuron or interneuron• (d) Efferent or motor neuron• (e) Effector organ

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Some examples of common human reflex actions

• (a) Knee jerk reflexes • (b) Ankle jerk reflexes • (c) Blinking reflexes • (d) Sneezing reflexes • (e) Salivation or watering of mouth on sight,

smell or thought of food. • (f) Withdrawal reflexes, viz. withdrawal of

hand or finger on touching a hot plate surface etc.

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Central Nervous System.• The Central Nervous System is that part of the

nervous system which lies within the bony case formed by the skull and the spine.

• The central nervous system, which includes the brain and spinal cord, processes and coordinates all incoming sensory information and outgoing motor commands, and it is also the seat of complex brain functions such as memory, intelligence, learning, and emotion.

• The brain and the spinal cord consists of this system.

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BRAINBILOGICAL BASES

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BrainBrain structure may be divided into

three levels

Brain stem and

CerebellumLimbic system Cortex

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Brain stem and cerebellum

• Medulla

• Pons

• Cerebellum

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THE MEDULLA OBLONGATA

• The Medulla oblongata is a continuation of the brain on the one hand and a spinal cord on the other.

• There fore its nerve tissues form a connection between the two paths of central nervous system. It is both a conductor as well as an integrating center.

• It regulates the highly complex process like digestion, respiration and circulation which are necessary for preservation of life.

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Pons

– Provides pathways for sensory and motor impulses to and from hemispheres.

– It also connects other parts of the brain with cerebrum and cerebellum

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THE MEDULLA OBLONGATABILOGICAL BASES

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CEREBELLUM

• Cerebellum or hindbrain is situated behind and beneath the cerebrum.

• It helps to maintain the equilibrium of the body and keeps it erect

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Mid brain• Mid brain connects cerebellum with

cerebrum.• Connected to the midbrain , there is a

complex mass of network of nerve fibres. • This is called reticular activating system – RAS

or ascending reticular activating system.• This is critically concerned with various

degrees of arousal – from deep sleep to alert awareness

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Reticular formation

The reticular formation is a collection of neurones in the core of the brain stem, surrounded by neural pathways that conduct ascending and descending nerve impulses between the brain and the spinal cord.

It has a vast number of synaptic links with other parts of the brain and is therefore constantly receiving 'information' being transmitted in ascending and descending tracts.

FunctionsThe reticular formation is involved in: 1. coordination of skeletal muscle activity associated

with voluntary motor movement and the maintenance of balance .

2. Coordination of activity controlled by the autonomic nervous system, e.g. cardiovascular, respiratory and gastrointestinal activity selective awareness that functions through the reticular activating system (RAS), which selectively blocks or passes sensory information to the cerebral cortex, e.g. the slight sound made by a sick child moving in bed may arouse his mother but the noise

• The mid brain is divided into two main parts:The roof or tectum :

- superior colliculi – vision- inferior coliiculi - auditory

The floor : provides connection between lower and higher centres of brain

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Fore - brain

• The higher centres of the brain is called fore brain. It includes :

i. Thalamus ii. Hypothalamusiii. Limbic systemiv. Cerebrum

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Brain anatomy

Brain basics

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Hypothalamus

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Limbic system

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The limbic system is a group of brain structures that play a role in emotion, memory, and motivation. For example, electrical stimulation of the amygdala in laboratory animals can provoke fear, anger, and aggression. The hypothalamus regulates hunger, thirst, sleep, body temperature, sexual drive, and other functions.

• The hippocampus is the largest of limbic structure. It has significant role to play in memory, particularly in the storage of long-term information.

• The amygdala has important role to play in aggression. It is also involved in memory, emotion, and certain basic motives.

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• The hypothalamus is the smallest structure in brain with a vital role to play in behaviour.

• It is concerned with regulation of physiological processes relating to emotional and motivational behaviours-eating, drinking, temperature regulation and sexual arousal.

• It is also concerned with regulation of endocrine system. Basically, hypothalamus involves in the maintenance of homeostasis in the body

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SPECILIZATION OF CEREBRAL HEMISPHERES

Cerebrum is divided into two equal halves by a deep grove.The left hemisphere is responsive to the right side of the body, while the right side is responsive to the left side of the body.Yet the two halves function in unison with each other with the help of the thick fibres called Corpus callosum .

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LEFT AND RIGHT HALF OF THE BRAIN

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• Left and Right Brain Functions Although the cerebrum is symmetrical in structure, with two lobes emerging from the brain stem and matching motor and sensory areas in each, certain intellectual functions are restricted to one hemisphere.

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• A person’s dominant hemisphere is usually occupied with language and logical operations, while the other hemisphere controls emotion and artistic and spatial skills.

• In nearly all right-handed and many left-handed people, the left hemisphere is dominant

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Left hemisphere Left hemisphere is often called the language brain.Stroke on the left side of the brain affects speech.SODIUM AMYTAL –a sedative- test on the brain also indicates the localization of speech area n the left half.Left HS is specialized for language function in 95% of the right handed people and 65% in left handed people

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Left hemisphereUpper temporal lobes and lower frontal lobes are main localized centres for language functionTemporal lobe language centre is called Wernicke’s area.The frontal lobe centre is called Broca’s area.

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• Wernike’s area is mainly involved in understanding of spoken and written language.

• Other language problems related to Wernike’s area:Impaired ability to repeat spoken words.Reading and writing problem.Difficulty in naming a common object.Intrusion of incorrect sounds or words into the flow of speech.

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• Symptoms of Broca’s area is different from Wernicke’s area.

• Damage to Broca’s area causes non fluent and ungrammatical speech.

• Eg. “he go.....school...yesterday...8 o’clock” (He went to school yesterday at 8 o’clock ).

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Anatomy of languageWernicke’s Geschwind model

• This model explains how an individual listens, speaks and understands written words.

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W- Wernike’s areaA- Arcuate fasciculusB- Broca’s area

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• This theory states that each anatomical area plays a particular role in various aspects of language.

• Spontaneous speech originates in Wernike’s area . But to speak it out ,the activity pattern of the Wernike’s area is sent to Broca’s area through Arcuate fasciculus.

• The Broca’s area programmes are then sent to the motor cortex region fore xpression.

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Right hemisphere

Some specialized centres for language.Artistic abilityMusic DanceImaginationFantasies

Spatial relation, colour, size and shapeCreative functions Emotional expressions

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• The right hemisphere is also concerned with the following aspects:

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Classical method1. Anatomical method2. Extirpation and ablation3. Action potential method4. Stimulation5. Chemical method6. Selective breeding

Modern method1. C T Scanning2. PET Scanning3. MRI Scanning4. SPECT5. SCQUID6. EEG

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Methods can be classified into two headings

METHODS EMPLOYED IN STUDYING BRAIN FUNCTIONS

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Anatomical method

• Tissue of the posthumous body is treated in such a way that nerve tracks can be viewed with the help of a microscope .

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Lesion,extirpation and ablation

• A lesion is the destruction or functional disruption of an area of the brain. An ablation is the removal of a part of the brain. Both of which produce behavioral deficit indicating the role of that part of the brain in developing the lost character.

• Extirpation refers to cutting out.• A small window on the skull is cut

to remove the brain or part either by cutting or suction.

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Stereotaxic instruments

• Investigators some times wish to study the effect of stimulating or damaging or recording the activity of deeper part of the brain of animals. The Stereotaxic instrument is provided with scale and electrodes. Researchers refer to a previously formed map called Stereotaxic atlas to help this process of study. 84

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Stimulation and recording from the

brain

• In this method electrode are implanted in the brain and briefly stimulated certain areas. The resultant behaviour is studied and their relation is established between the stimulated area.

• Eg stimulating the lateral hypothalamus increases eating

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Action potential method

• Sensitive electrical recording devices are used to detect the electrical changes in the neurons of the brain.

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Chemical method

• Chemical crystals, drugs or hormones are inserted to the brain nuclei helps to study the type of transmitter substances employed in the synapse

• The resultant reactions are observed to identify the type of brain chemical involved

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Selective breeding

• In this method the experimenter raises a number of generation of plants or animals and systematically sort out each generation to study the hereditary genesis of behaviour.

• (ie. Transfer of characters/behaviour from parents to offsprings are studied)

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MODERN TECHNIQUES

• Owing to modern advances in and developments of modern sophisticated techniques it is possible to know and understand the functions of brain without causing any harm to it .

• These techniques are called Brain Imaging Techniques (BIT).

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Computerized Axial Topography(CAT

scan• X- rays are

passed through the brain at every one degree of the brain till 1800 completed. Computer reconstructs the images.

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Magnetic Resonance Imaging (MRI)

• MRI reveals structural deficit, like enlarged ventricles

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Normal and Schizophrenic Brains(MRI)BILOGICAL BASES

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Positron Emission Tomography

• In this method, a patient is injected with glucose treated with radioactive tracers.

• As the body metabolizes the glucose, the PET scan monitors the radioactive particles emitted by the tracers in the glucose.

• Images are produced that show metabolic reactions, making this method useful to diagnose brain tumors and

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PET

Scan

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Single photon emission computed tomography (SPECT),

• Single photon emission computed tomography (SPECT), developed in the 1950s and 1960s, uses radioactive tracers to visualize the circulation and volume of blood in the brain.

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Electroencephalography• Electroencephalography, procedure for obtaining a

record of the electrical activity of the brain by means of electrodes attached to the surface of the skull.

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Normal Seizure 98

THEORIES OF BRAIN FUNCTIONS

• According to this theory each part of the cerebrum is specialized to perform a particular function. Eg. Sensory function.

• Three major localized functions are as follows:I. Sensory functionsII. Motor functionsIII. Association functions

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BRAIN AND ITS AREAS

Sensory functions

• Most of the sensory functions have specific areas in the cerebral cortex called Primary sensory areas.

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Categorization of sensory functionSlNO Sensory experience Related sensory

organSpecified areas in brain to perform related function

1 Taste and smell TongueTemporal lobe cortex buried in the lateral fissures

2 Kinesthetic/somesthetic Skin Parietal lobe

3 Visual Eye Occipital lobe

4 Audition Ear A portion of temporal lobe

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MOTOR FUNCTIONS

•Primary area- controls some muscles•Secondary motor area – less known function•Supplementary motor area – Muscle tone and postural control

Three areas in the brain has

been identified for performing

motor functions.(Pyramidal

tract)

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Association area

•Learning •Thinking•Remembering•Decision making•Reasoning•Motivation•Emotionally charged activities•(ie. Higher order brain functions)

Association area

performs integrativ

e functions

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Problems associated with damage to areas

Area Disorder

Frontal lobe Delayed response , blunted expression

Association area Affects learning, thinking, memmory, reasoning, emotionally charged activities etc

Other defectsAsteriognosis Loss of ability to recognize solid objects through touch

Alexia Inability to recognize printed words

Sensory aphasia Inability to recognize spoken words

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Mass action theory (Equipotential Theory)

According to this theory different areas or parts of the brain area are more or less functionally interchangeable.

It has been observed that impairment or injury in a particular area though cause disturbance or almost complete loss of function, gradually , owing to practice, the lost function recurs

Also the living structures in the nearby area take over to discharge the lost function.

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CONCLUSION

• Though the rationale put forward by equipotential or mass action theorists are tenable. However modern studies show that various parts of the brain are responsible for different functions .

• Therefore a compromising position appears to be more tenable

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Autonomic Nervous System

• Autonomic Nervous System, in vertebrate anatomy, one of the two main divisions of the nervous system, supplying impulses to the body's heart muscles, smooth muscles, and glands.

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• Two antagonistic divisions make up the autonomic nervous system:

1. the sympathetic, or thoracicolumbar, division, which stimulates the heart, dilates the bronchi, contracts the arteries, and inhibits the digestive system, preparing the organism for physical action.

2.The parasympathetic, or craniosacral, division, which has the opposite effects, and prepares the organism for feeding, digestion, and rest

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BILOGICAL BASES

OF BEHAVIOUR• The sympathetic division consists of a chain of interconnected ganglia (groups of nerve cells) on each side of the vertebral column, which send nerve fibers to several large ganglia, such as the coeliac ganglion.

• They, in turn, give rise to nerves passing to the internal organs. The ganglia of the sympathetic chains are connected to the central nervous system by fine branches connecting each ganglion with the spinal cord

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BILOGICAL BASES

OF BEHAVIOUR• Fibers of the parasympathetic system arise in the brain and, with the cranial nerves, especially the vagus and accessory nerves, pass to ganglia and plexuses (networks of nerves) within the various organs.

• The lower part of the body is innervated by fibers arising from the lowest (sacral) segment of the spinal cord and passing to the pelvic ganglion, which gives rise to nerves for such organs as the rectum, bladder, and genital organs.

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BILOGICAL

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BEHAVIOURDUCTLESS GLANDS OR ENDOCRINE GLANDS

• There are several glands in our body, which secrete several bodily chemicals both internally as well as externally.

• They can be grouped into two distinct categories namely duct glands and ductless glands or endocrine glands.

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End

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• The under activity or over activity of these glands caused by the deficiency or excess of the hormones secreted by them as well as well as by the co acting influence of other glands like Thyroid, Pituitary and Adrenal affects not only the sexual growth and development of an individual but also his entire behaviour and developmental process.

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• A slight imbalance of these glands causes restlessness, anxiety and weakness.

• Our physical strength, morale thinking and reasoning power and decision-making ability – all depend upon the health of the glands.

• In short, these glands are found to play a dominant role in the life of a person.

• Without their proper functioning a man or woman finds difficulty in leading a happy normal life.

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BILOGICAL BASES

OF BEHAVIOURNERVOUS SYSTEM AND PERSONALITY DEVELOPMENT

• Our behaviour to a great extend is controlled by our nervous system.

• How we will behave in a particular situation depends upon the judgment of our brain.

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