biological basis of psychology by p.mahesh

1. BIOLOGICAL BASIS OF PSYCHOLOGY

2. Out line
Basic units of nervous system
Organization of nervous system
Hierarchical structure of brain
Autonomic nervous system
Endocrine system
Genetic influence on behavior

3. Biopsychology
Biological psychology is the scientific study of
the biological bases of behavior and mental
States
Because all behavior is controlled by the central
nervous system, it is sensible to study how the brain
functions in order to understand behavior.

4. Basic units of nervous system
Neuropsychology
 It is the branch of psychology that aims to understand
how the structure and function of the brain relate to
specific behavioral and psychological processes.
Neurons
• The base of the nervous system is the neuron. Neurons
are cells that are specialized for communicating
information. They are the basic tissue and element of the
nervous system.
Neurons have a basic structure of:
• One cell body
• One axon
• One or more dendrites

6. cell body
 The cell body (or soma) is the bulbous end of a neuron,
containing the cell nucleus.
 The soma makes use of nutrients to supply energy for neuronal
activity.
Axon
 Axons are organelles that carry information away from the
cell body.
 The axons main job is to send a signal to the dendrites of
another neuron, but some say that they may also receive
signals in certain situations.
 Each neuron has only one axon, but the axon may have
branches with what are called terminal buttons at its end.
Dendrites
 Dendrites are organelles that sense the neurotransmitter
secreted by the axon of another neuron.
 Most neurons have more than one dendrite. ..

7. A nerve is a bundle of elongated axons belonging
to hundreds or thousands of neurons.
The axons from a great many neurons may
connect with the dendrites and cell body of single
neuron.
Synapse
A junction between neurons is called synapse.
 Dendrites and axons do not directly touch each
other; there is a gap, called a synapse.
 A slight physical separation exists across which
the nervous impulse is transmitted by chemical
intermediary.

9. Transmission of nerve impulse
A nerve impulse is a way of two nerve cells to
communicate with one another.
electric current across the cell membrane
Transmission of nerve impulse is electro
chemical process
Nerve transmission has following
steps

11.  Cell membrane is not equally permeable to
different types of electrically charged ions.
 In its resting state the cell membrane keeps out
positively charged sodium(Na+ )ions and allow in
potassium (K+ )ions and chloride ions (Cl- ).
 As a result there is a small electrical potential or
difference across the membrane
 The inside of the nerve cell is slightly more
negative than the out side ; this its resting
potential.
 When the axon of the nerve cell is stimulated , the
electric potential across the membrane is reduced
at the point of stimulation.

12.  If the reduction in the potential is large enough, the
permeability of the permeability of the cell
membrane is suddenly changes, allowing the
sodium ions to enter the cell. Now the out side of
the cell membrane is negative with respect to the
inside.
 This change also effects the adjacent portion of the
axon, causing its membrane to permit the inflow of
the sodium ions.
 This process, repeating itself down the length of the
axon called nerve impulse.
 The nerve impulse is also known as action
potential in contrast to resting potential.
 The action potential sends the signal the entire
length of the cell and never dies within the cell,
which can be referred to as the all-or-none-principle.

13. Synaptic transmission

14.  The synapse is a gap between two cells.
 Synapse are one way junctions between neurons
and other cells.
 The neurotransmitter is emitted from the axon of
one cell and usually goes to the dendrite of the
next cell. Sometimes the signal goes to the soma
or the axon of the next cell instead of the dendrite
(Arnold Wittig 2001).
 The terminal button at the end of the axon holds
the synaptic vesicles.
 When the signal reaches the end of the axon the
vesicles discharge a chemical called a neuro
transmitter.

15.  The transmitter chemical combines with the receptor
chemical in the receiving cell.
 This chemical reaction increases the membrane
permeability and decreases the membrane potential.
This leads to the graded depolarization may be strong
enough to discharge the receiving neuron.
 Neurotransmitters are chemicals that are used to
relay, amplify and modulate electrical signals
between a neuron and another cell.
 There are approximately 40 to 60 different chemicals
that are used as neurotransmitters.
 The neurotransmitters from the axon fit into receptors
of the dendrite on the next neuron.
 They will then either excite the cell and make it fire
or inhibit it and stop it from doing so.

16. Organization of nervous system

17. The neurons can all be placed in one of two systems, the
central nervous system or the peripheral nervous system.
The Central nervous system
 The central nervous system has a fundamental role in the
control of behavior. It contains the brain and the spinal cord
which are both encased in bone which shows their
importance. Both the brain and spinal cord receive signals
from the afferent neurons and send signals to muscles and
glands through efferent neurons.
The peripheral nervous system
 Any part of the nervous system that is not part of the central
nervous system is part of the peripheral nervous system.
The nerves in the peripheral nervous system is split up into
the autonomic and somatic. The somatic connect the central
nervous system to sensory organs (such as the eye and ear)
and muscles, while the autonomic connect other organs of
the body, blood vessels and glands.

18. Spinal cord
 The nerve fibers running from the various parts of
body to and from the brain are gathered together in
the spinal cord, where they are protected by the bony
spinal vertebrae
 Some of the very simplest stimulus-response are
carried out with in the spinal cord. E.g. knee jerk
 Although this response can occur solely in the spinal
cord with out any assistance from the brain, but it is
under the control of brain.
 For example, if the spinal cord is severed from the
brain, as in case of paraplegic accident victim,
reflexes such as knee jerk and erection of the penis
still function. But most activity involves the
transmission of nerve impulse to brain.

19. Hierarchical structure of brain
• As the spinal cord enters the bony scull it
enlarges in to the brain stem, which contains all
the ascending and descending nerve fibers that
link the body with the higher brain structures as
well as nuclei.
• As an evolutionary view point brain stem is the
oldest part of the brain where as cerebral
hemispheres are the latest and largest part.
• For our purposes it will be helpful to think of
the human brain as composed of three
concentric layers.

20. Central core
Limbic system
Cerebral cortex

21. Central core
 The central core includes the most of the brain stem.
 It constitutes the following parts
1.Medulla
 The first slight enlargement of the spinal cord as it
enters the skull is the medulla.
Via cranial nerves, exerts important control over
breathing, swallowing, digestion, heart rate.
2.Cerebellum
 Attached to rear of the brain stem, slightly above the
medulla is a convoluted structure known as the
cerebellum
 Muscle tone; body balance; coordination of voluntary
movements

22. 3.Thalamus
Located just above the brain stem inside the
cerebral hemispheres are two egg shaped groups
of nerve cell nuclei that make up thalamus
 Sensory relay station on the way to the cerebral
cortex
Also plays an important role in the control of
sleep and wakefulness
4.Hypothalamus
Much smaller structure just below the thalamus
Control of visceral and somatic functions such as
temperature, metabolism, and endocrine balance.

23. 5.Reticular activating system
 System of neural circuits that extends from lower
brain stem up to the cerebrum
 Acts as conscious switch

24. Limbic system
 Around the central core of the brain, lying along the
innermost edge of the cerebral hemispheres, are a
number of structures which grouped together are
called the limbic system.
 this system is closely interconnected with the
hypothalamus and seems to program the sequential
activities necessary to satisfy some of the basic
motivational and emotional needs regulated by the
hypothalamus
 The instinctive activities of animals, such as feeding
attacking, fleeing from danger and mating appear to
be governed by limbic system.

26. Cerebral cortex
 The two large cerebral hemispheres that envelop the
brain stem are the most recent parts of the nervous
system
 They are more highly developed in man than in any
other organism.
 The cerebral cortex is the thick layer of nerve cell
bodies covering the cerebrum.
 The cortical layer appears gray because it consists
largely of nerve cell bodies and non myelinated
fibers.
 The inside of the cerebrum beneath cortex is
composed mostly of myelinated axons, and appears
white.

28. • The two hemispheres are symmetrical, one on
right and one on left with a deep division
between them.
• Each hemisphere is divided in to four lobes
frontal
parietal
occipital
temporal

29. Cortical areas and their functions

30. 1.Motor area
 Lies just in front of the central fissure i.e. in frontal
lobe.
 Which controls all the movements of the body
 Movements of the right side of the body originate
through stimulation of motor area of left hemisphere
and vice versa.
2.Body-sense area
 In parietal lobe
 Stimulus gives sensory experiences for are heat, cold,
touch, pain, and the sense of the body movements.

31. 3.Visual area
 At very back of each cerebral hemisphere, in the part
of the occipital lobe known as the striate area.
 Lie centers important in vision
4.Auditory area
 Found on the surface of the temporal lobe
 One part being sensitive to high tones and a different
part sensitive to low tones.

32. 5.Langauge areas
 Just above the lateral fissure in the frontal lobe
 Speech in most cases is controlled by the left
hemisphere.
 Some left handed people have speech centers located in
right hemisphere.
6.Association area
 The many large areas of the cerebral cortex that are not
directly concerned with sensorimotor process have
been called association areas.
 Function in learning, memory and thinking
 Frontal association area – important role in the thought
process required for problem solving
 Posterior association areas- related to visual perception.
 Temporal association areas- related language

33. Experiments with split brain subjects

34. Example
 Split brain subject/patient seated in front of a screen
that hides his hands from view.
 His gaze is fixed at a spot on the centre of the screen
 The word ‘ball’ is flashed very briefly(1/10th of a
second) on the left side of the screen.
 The visual image goes to the right side of the brain
which controls the left side of the body
With his left hand can easily pick out the ball from
the pile of hidden from view.
 But he can not tell the experimenter what word
flashed on the screen because language depends on
left hemisphere and visual image ball was not
transmitted to left side.

37. How the brain is studied?
The following four methods are used most often by
physiological psychologists and neurophysiologists
1.Injury or surgical ablation
2.Electrical or chemical stimulation
3.Electrical effects of neural activity
 When neuronal actions occurs, slight electrical currents are
produced
 The brain as whole also produce rhythmical electrical
discharges
 The record of these total brain discharges, known as electro
encephalogram, plays its role in the study of CNS activity.
4.Single neuron activity
 The development of extremely refined microelectrodes has
made it possible to record the nerve impulse from a single
neuron.

38. Autonomic nervous system
functions of the ANS
1. Sympathetic readies the body for an emergency
2. Parasympathetic restores the body to homeostasis
3. Most organs are dually innervated
4.Contrls the glands and smooth muscles that comprises
the heart, blood vessels, lining of stomach and
intestine.
It has two divisions
 Sympathetic
 parasympathetic

40. Endocrine system
 Many of the bodily reactions that results from activity of
autonomous nervous system are produced by the action of that
system on the endocrine glands.
 The endocrine glands secrete some special chemical
messengers called hormones, that are carried through out the
body by blood stream.
 These chemicals are as essential as nervous system to the
integration of the organisms activities and to the maintenance
of the homeostasis.
 For example some neurons use a hormone, nor epinephrine, as
their chemical transmitter.
 The endocrine glands are responsible for growth, sexual and
maternal behavior, the individual characteristic level of energy
and mood, and reaction to stress.

42.  Pituitary gland
 Adrenal gland
Pituitary gland
 One of the major endocrine glands
 Is partially an out growth of brain and is joined to it
just below the hypothalamus
 The pituitary gland has been called the master gland
because it produces the largest number of different
hormones and controls the secretion of other
endocrine glands.
 The pituitary has two independently functioning
parts.
1.posterior pituitary
2.anterior pituitary

43. Posterior pituitary
Two hormones produced in the hypothalamus are
transported along nerve axons for released by the
posterior pituitary
 One hormone called oxytocin, influence the
contraction of uterus during child birth and
production of milk in the mammary glands.
 The other called vasopressin/ADH, regulates the
amount of water in the body cells and indirectly
controls the blood pressure.

44. Anterior pituitary
 It is also controlled by the hypothalamus but in
different way.
 Certain hormones released by the hypothalamus are
carried to the anterior pituitary by a system of tiny
blood vessels. The stimulate the anterior pituitary to
release its own hormones. They are
 ACTH
 TSH
 GH
 PRH
 FSH
 LH
 MSH

45. Adrenal gland
the inner core of adrenal gland called medulla secrets two hormones
 Epinephrine
 Nor epinephrine
Epinephrine
 Acts in number of ways to prepare the organism for emergency.
 It is closely involved with the action of sympathetic division of
autonomic nervous system.
 For example acts on the smooth muscles and sweat glands in way
similar to sympathetic system.
1.causes nervous perspiration
2. constriction of blood vessels in the stomach and intestines
3.makes the heart beat faster
4.also acts on the RAS which excites the sympathetic system
which in turn stimulate the adrenalin to secrete more
epinephrine

46. Nor epinephrine
 Acts to prepare the organism for emergency action
 NE blood stream pituitary gland
release ACTH acts on the outer part of adrenal
called cortex stimulating the release of
adrenocortical hormones called steroids e.g.cortisol
 these steroids promotes the release of sugars stored in
the liver so the body has energy for quick action.
 These steroids also help to maintain the normal
metabolic process of the body.

47. Genetic influence on behavior
 To understand the biological foundations of behavior
we need to study something about hereditary
influences.
 Many physical characteristics such as height, bone
structure, and hair and eye color, are inherited.
 Behavioral genetics are interested in the degree to
which physiological characteristics such as ability,
temperament, and emotional stability, are transmitted
from parent to offspring.
 All behavior depends upon the interaction between
heredity and environment

48. Chromosomes and Genes
 The hereditary units we receive from our parents
transmit to our offspring are carried by microscopic
particles known as chromosomes
 They are present in the nucleus of each cell in the
body.
 Most body cells contain the 46 chromosomes.
 At conception the human being receives 23
chromosomes from the father’s sperm and 23
chromosomes from the mother’s ovum

49. • Each chromosome is composed of many individual
hereditary units called genes, which also occur in
pairs.
• The total number of genes in each human
chromosome is on the order of 1000, perhaps higher.
• Because the number of genes is so high, it is
extremely unlikely that the two human beings would
have the same heredity, even with the same parents.
one exception is identical twins.

50.  One important attribute of some genes is dominance
or recessiveness.
 Some of the characters that are carried by recessive
genes are baldness, albinism, hemophilia etc.

51. Chromosomal abnormalities
1.turner’s syndrome
 Female with only one X chromosome
 Individuals are short, webbed neck, and fail to
develop sexually at puberty.
2.klinefelter’s syndrome
 Individual with XXY
 physically male with penis and testicles, but with
marked feminine characteristics

52. 3. Super male
 Men with an extra Y chromosome i.e. XYY
 usually aggressive
 Abnormal amount of male hormone production so
such individuals reach sexual maturity early and may
have a higher than normal sex drive.
4.down’s syndrome
 Extra chromosome on 21st chromosome
 Mental deficiency and mongolism.

53. Genetic studies of behavior
 Most human characteristics are determined by many
sets of genes; they are polygenic.
 These traits are intelligence, height, and emotionality
do not fall in to distinct categories but show
continuous variation.
Methods of studying the heritability of traits
1.Selective breeding
2.Twin studies

54. Environment influence on gene action
 The hereditary potential with which an individual
enters the world is very much influenced by the
environment that he encounters.
 For example the tendency to develop diabetes
mellitus is hereditary, but people who carry the
genetic potential for diabetes do not always develop
the disease.
 The unafflicted twin clearly carried the genes for
diabetes, but apparently was spared because his diet
made fewer demands for carbohydrate metabolism.
 Thus, diabetes is caused neither by heredity alone nor
by environment alone, but by the interaction of the
two.