Chapter 3
Physiological Bases of Behaviour
Introduction
Psychology is the scientific study of behaviours and conscious experiences
of the organism in relation to its environment. What is behavior ? Behaviour is what
the organism does externally or internally – covertly or overtly from the very
conception till death. Organism means any living being. Animals o r organisms
continue to behave whether they are awake or asleep, and all their behaviours take
place in the context of an environment.
The study of behaviour involves three different but closely related
physiological processes such as receptor process, effector process, and process of
nervous system. Physiological psychologists study these processes to understand
biological bases of behaviour. The three kinds of physiological processes work with
three kinds of structures. In fact, there are receptor struct ures, effector structures,
and structures of the nervous system.
Receptors
Receptors are the gateways to information. Our body has eight kinds of
receptors, such as visual receptors (eyes), auditory receptors (ears), olfactory
receptors (nose), gustatory receptors (tongue), tactual receptors (skin),
labyrinthine receptors (cochlea in inner ear giving us sensation about our position
of the body in space), kinesthetic receptors (deep joints and muscles) and
visceral receptors (about internal organic sensation). Thus receptors are divided
into eight types according to sense modalities.
Any event, which causes the sense organs to be active, is termed as
stimulus. Receptors are those sense organs of the body by which w e receive
the stimulation of various kinds from the environment. These receptors are
sensitive to stimulation. What is stimulation? Stimulation is physical energy.
Our eyes, ears, tongue etc. are sensitive enough to notice stimulation
through our receptors. Without these receptors
,we would sense nothing, feel nothing, would see nothing and would have no
information about the world.
Specific stimulations are received by specific receptors. For example, visual
stimuli (color, people, light, books etc.) are received by only visual receptors i.e.,
eyes only. Similarly, auditory stimulations (music, sound, noise, chirping etc.) are
received by pair of ears only. We also receive combined stimulations from the
environment and these are integrated in the brain. Thus, receptors being the
sensitive parts of our body detect any changes in stimuli present in the
environment. The cells in our sense organs are built to receive information in
special ways. All receptors are able to produce impulses as a result of changes in
some form of energy. There are mainly 3 categories of receptors, such as: (a)
exteroceptors, (b) interoceptors, and (c) proprioceptors.
The exteroceptors receive stimulus information from external sources
but only when the source of information comes in direct physical contact with the
receptors. Such receptors are found in the sense organs like eyes, ears, nose, skin
and tongue. The interoceptors receive stimulus information form internal
sources. Such receptors are found in organism‟s sense organs such as lining of
the stomach, bladder, viscera etc. These receptor cells may be called as organic
receptor cells. When our stomach is empty for example, the organic receptor cells,
which are present in the stomach boundary wall, receive this information. The
proprioceptors do not require either an external or internal stimulus to be
stimulated. These receptor cells are stimulated by themselves. These are found
in the kinesthetic sense organs, which constitute muscles, tendons, joints etc., and
the static or vestibular sense organ (semi -circular canal of the inner ear). These
receptor cells are also called kinesthetic or vestibular rece ptor cells, respectively.
Kinesthetic receptor cells receive information form our muscles and joints as they
move. Vestibular receptor cells receive such information when our body is lifted, or
is moving, falling down or speeding up.
Effectors
Effectors are the muscles and glands, which are the exercising organs for
doing action. Effectors are the organs, which bring “effects” in the
environment. Effect leads to changes; we execute our actions by our hands,
legs, and muscles. Secretions
,from glands within the body at appropriate times supply energies to such activities.
The “effects” or changes, which are brought by our bodily effectors, are called
“responses” or “performances”. Salivary glands, digestive glands, and sweat glands
are a few examples of glands.
Nervous System connects all receptors with all effectors . It spreads over
the entire body through nerves. A single nerve consists of a bundle of many
individual neurons. Neurons in a nerve differ both in sizes of axon and diameter of
axon. There are chains of neural structures, which connect each receptor with each
effector. These connections are made by nerves and neurons inside. The neurons,
which conduct impulses from different sense organs to the brain, are called
sensory neurons. For example a n euron, which carries impulses from the ears to
the brain, is an example of sensory neuron. Sensory neurons are called afferent
neurons. Most sensory neurons extend from each sense organ to the central
nervous system, which is composed of the brain and the spinal cord. The neurons
that transmit nerve impulses from the brain to the motor organs (or effectors) are
called motor or efferent neurons. The nerve impulses are carried by efferent
neurons to the muscles or glands in order to contract, relax or to expa nd according
to the responses made by the organism.
Neurons : Building Blocks of the Nervous System
To understand how the nervous system controls behaviour, it is essential to
understand the structure and functions of its basic building blocks, i.e., the neurons
or the nerve cells. How many neurons are there in the nervous system? No one has
actually counted the number. But we can see estimates of neurons in the nervous
system in different books to be between 100 and 1000 billions.
Basic Structure of a Neuron
The neuron is the basic element of the nervous system. The neuron or the
nerve cell is the information transmitting and information -processing
element of the nervous system. Neurons come in many different shapes,
sizes and varieties according to the specialized jobs they perform. Some of
them are very small in size. They are so small that we will require an
electronic microscope to detect them. Some of the neurons are very lo ng in
structure. Their length in some cases may be more than one meter.
Whatever may be their sizes and shapes, neurons usually have a
, common form. We shall consider the
structure and functions of neurons having a
common form. Neurons in general have the
Dendrite
following structures: (i) cell body or soma, (ii)
dendrites, (iii) axon, and (iv) terminal buttons
or axon terminals (see Figure 3.1). Cell body
Cell Body or Soma. The enlarged
“head” of the neuron is called “cell body”
or soma. The soma or the cell body is
enclosed by the cell membrane and contains
the nucleus of the cell. Soma is the head side Axon Dendrite
of the neuron. It uses oxygen and nutrients to
generate energy to carry out the work of the
Presynaptic Cell
cell. Its shape varies considerably in different
kinds of neurons. Node of Ranvir
Myelin sheath
Dendrites. Dendron is the Greek word
Axon
for tree and the dendrites of a neuron look
very much like trees. Dendrites are extended
from the cell body. There are several
extensions from the cell body of the neuron. Terminal
Dendrites receive the neural impulses from
the receptors or from several adjoining
Dendrite
neurons. In no case, other parts of a neuron
excepting dendrites receive the impulse.
Postsynaptic Cell
Cell
Axon. There are two types of body
extensions from the cell body. The
many shorter extensions from the cell
body are called dendrites. The longer
single-branched extension is called
the axon.
Figure 3.1 The major structures of a neuron, the
basic element of the nervous system.
Physiological Bases of Behaviour
Introduction
Psychology is the scientific study of behaviours and conscious experiences
of the organism in relation to its environment. What is behavior ? Behaviour is what
the organism does externally or internally – covertly or overtly from the very
conception till death. Organism means any living being. Animals o r organisms
continue to behave whether they are awake or asleep, and all their behaviours take
place in the context of an environment.
The study of behaviour involves three different but closely related
physiological processes such as receptor process, effector process, and process of
nervous system. Physiological psychologists study these processes to understand
biological bases of behaviour. The three kinds of physiological processes work with
three kinds of structures. In fact, there are receptor struct ures, effector structures,
and structures of the nervous system.
Receptors
Receptors are the gateways to information. Our body has eight kinds of
receptors, such as visual receptors (eyes), auditory receptors (ears), olfactory
receptors (nose), gustatory receptors (tongue), tactual receptors (skin),
labyrinthine receptors (cochlea in inner ear giving us sensation about our position
of the body in space), kinesthetic receptors (deep joints and muscles) and
visceral receptors (about internal organic sensation). Thus receptors are divided
into eight types according to sense modalities.
Any event, which causes the sense organs to be active, is termed as
stimulus. Receptors are those sense organs of the body by which w e receive
the stimulation of various kinds from the environment. These receptors are
sensitive to stimulation. What is stimulation? Stimulation is physical energy.
Our eyes, ears, tongue etc. are sensitive enough to notice stimulation
through our receptors. Without these receptors
,we would sense nothing, feel nothing, would see nothing and would have no
information about the world.
Specific stimulations are received by specific receptors. For example, visual
stimuli (color, people, light, books etc.) are received by only visual receptors i.e.,
eyes only. Similarly, auditory stimulations (music, sound, noise, chirping etc.) are
received by pair of ears only. We also receive combined stimulations from the
environment and these are integrated in the brain. Thus, receptors being the
sensitive parts of our body detect any changes in stimuli present in the
environment. The cells in our sense organs are built to receive information in
special ways. All receptors are able to produce impulses as a result of changes in
some form of energy. There are mainly 3 categories of receptors, such as: (a)
exteroceptors, (b) interoceptors, and (c) proprioceptors.
The exteroceptors receive stimulus information from external sources
but only when the source of information comes in direct physical contact with the
receptors. Such receptors are found in the sense organs like eyes, ears, nose, skin
and tongue. The interoceptors receive stimulus information form internal
sources. Such receptors are found in organism‟s sense organs such as lining of
the stomach, bladder, viscera etc. These receptor cells may be called as organic
receptor cells. When our stomach is empty for example, the organic receptor cells,
which are present in the stomach boundary wall, receive this information. The
proprioceptors do not require either an external or internal stimulus to be
stimulated. These receptor cells are stimulated by themselves. These are found
in the kinesthetic sense organs, which constitute muscles, tendons, joints etc., and
the static or vestibular sense organ (semi -circular canal of the inner ear). These
receptor cells are also called kinesthetic or vestibular rece ptor cells, respectively.
Kinesthetic receptor cells receive information form our muscles and joints as they
move. Vestibular receptor cells receive such information when our body is lifted, or
is moving, falling down or speeding up.
Effectors
Effectors are the muscles and glands, which are the exercising organs for
doing action. Effectors are the organs, which bring “effects” in the
environment. Effect leads to changes; we execute our actions by our hands,
legs, and muscles. Secretions
,from glands within the body at appropriate times supply energies to such activities.
The “effects” or changes, which are brought by our bodily effectors, are called
“responses” or “performances”. Salivary glands, digestive glands, and sweat glands
are a few examples of glands.
Nervous System connects all receptors with all effectors . It spreads over
the entire body through nerves. A single nerve consists of a bundle of many
individual neurons. Neurons in a nerve differ both in sizes of axon and diameter of
axon. There are chains of neural structures, which connect each receptor with each
effector. These connections are made by nerves and neurons inside. The neurons,
which conduct impulses from different sense organs to the brain, are called
sensory neurons. For example a n euron, which carries impulses from the ears to
the brain, is an example of sensory neuron. Sensory neurons are called afferent
neurons. Most sensory neurons extend from each sense organ to the central
nervous system, which is composed of the brain and the spinal cord. The neurons
that transmit nerve impulses from the brain to the motor organs (or effectors) are
called motor or efferent neurons. The nerve impulses are carried by efferent
neurons to the muscles or glands in order to contract, relax or to expa nd according
to the responses made by the organism.
Neurons : Building Blocks of the Nervous System
To understand how the nervous system controls behaviour, it is essential to
understand the structure and functions of its basic building blocks, i.e., the neurons
or the nerve cells. How many neurons are there in the nervous system? No one has
actually counted the number. But we can see estimates of neurons in the nervous
system in different books to be between 100 and 1000 billions.
Basic Structure of a Neuron
The neuron is the basic element of the nervous system. The neuron or the
nerve cell is the information transmitting and information -processing
element of the nervous system. Neurons come in many different shapes,
sizes and varieties according to the specialized jobs they perform. Some of
them are very small in size. They are so small that we will require an
electronic microscope to detect them. Some of the neurons are very lo ng in
structure. Their length in some cases may be more than one meter.
Whatever may be their sizes and shapes, neurons usually have a
, common form. We shall consider the
structure and functions of neurons having a
common form. Neurons in general have the
Dendrite
following structures: (i) cell body or soma, (ii)
dendrites, (iii) axon, and (iv) terminal buttons
or axon terminals (see Figure 3.1). Cell body
Cell Body or Soma. The enlarged
“head” of the neuron is called “cell body”
or soma. The soma or the cell body is
enclosed by the cell membrane and contains
the nucleus of the cell. Soma is the head side Axon Dendrite
of the neuron. It uses oxygen and nutrients to
generate energy to carry out the work of the
Presynaptic Cell
cell. Its shape varies considerably in different
kinds of neurons. Node of Ranvir
Myelin sheath
Dendrites. Dendron is the Greek word
Axon
for tree and the dendrites of a neuron look
very much like trees. Dendrites are extended
from the cell body. There are several
extensions from the cell body of the neuron. Terminal
Dendrites receive the neural impulses from
the receptors or from several adjoining
Dendrite
neurons. In no case, other parts of a neuron
excepting dendrites receive the impulse.
Postsynaptic Cell
Cell
Axon. There are two types of body
extensions from the cell body. The
many shorter extensions from the cell
body are called dendrites. The longer
single-branched extension is called
the axon.
Figure 3.1 The major structures of a neuron, the
basic element of the nervous system.
