Transcript nervous system

NERVOUS SYSTEM AND
BEHAVIOR
INTRODUCTION
Living organisms have a unique
property of receiving stimuli from
environment and respond to
change accordingly. The
information received by the
organism is coordinated through
nervous system so that it can act
or behave effectively for its
survival under any circumstances
Nervous System
There are two divisions….
CNS and PNS
Central Nervous System
Brain
Spinal Cord
Central Nervous System
Peripheral Nervous System
Peripheral Nervous System
(PNS)
Cranial Nerves – emerge through
cranial foramina of the
skull.Reptiles, birds, and mammals
have only 12 pairs of these.
Spinal Nerves – emerge through
intervertebral foramina. The
number of spinal nerves is directly
related to the number of segments
in the trunk and tail of vertebrae.
e.g, number of spinal nerves in
frog is only 10 pairs due to reduced
trunk, and no tail in adult.
Ganglia – groups of nerve cell
bodies outside of the brain and
spinal chord.
Autonomic Nervous System –
innervates smooth muscle, cardiac
muscle, and glands
Peripheral Nervous System
Brain
Spinal
Cord
Nerves
Neurons
The functional unit of nervous
system is highly specialized cell
known as neuron. these are
specialized to produce signals that
can be communicated over short to
relatively long distance, from one
part of animal body to another.
Structure of neuron
Nucleus
Cell body
Dendrite
Axon
Schwann cell
Node of Ranvier
Classification of Nerve Cells
(Neurons)
A. Sensory (afferent)
B. Motor (efferent)
C. Interneuron
Sensory neurons act as receptor
of stimuli. Change in internal and
external environment stimulate
sensory neurons which respond
by sending signals to major
integrating centre where
information are processed.
Motor neuron
Motor neurons send the processed
information via signals to body
effectors e.g., muscles causing
them to contract or to glands
causing them to secrete.
Interneuron
Comprises integrating centre and
receive signals from sensory
neuron and transmit them to motor
neurons.
Myelinization
Myelin Sheath – The
specialized glial cells that wrap
around the axon of neurons.
Within the CNS 
Oligodendrocytes
Within the PNS  Schwann
Cells
Unmyelinated axons
Sympathetic Nervous –
Fight/Flight
Increased Heart Rate
Increased Blood Pressure
Pupil Dilation
Decreased Urination
Increased Sweating
Bronchial Dilation
Decreased Salivation
Parasympathetic – Energy Sparing
Decreased Heart Rate
Decreased Blood Pressure
Pupil Constriction
Increased Urination
Decreased Sweating
Bronchial Constriction
Increased Salivation
Neurotransmitters
Chemicals released by
the pre-synaptic neuron
Sympathetic
Epinephrine,Norepinephrine
Parasympathetic
Acetylcholine
What’s the Matter?
Grey Matter –
non-myelinated neurons
White Matter –
Myelinated neurons
Brain
Cerebrum – made of white
and grey matter
Largest part of
mammalian brain
Higher order behavior
(awareness, learning)
Cerebellum – motor function and
coordination
Brain Stem –
Medulla Oblongata, Pons, Mid-brain
Autonomic Functions – things you
don’t think about
Ventricles and Cerebrospinal
Fluid
Ventricles – Open spaces in the
brain, filled with fluid, that
support and cushion the brain.
Cerebrospinal Fluid – slippery,
clear fluid that bathes and
cushions the CNS.
Produced by Choroid Plexuses
Reproduced every 24 hours
Reflexes
Spinal Reflex- rapid, automatic
response to sensory input
Does not require brain
Types of reflexes
There are three types of reflexes
Superficial reflexes
Myotatic reflexes
Righting reflexes
Superficial reflexes
Reflexes that are involved with the
skin are called Superficial reflexes.
Myotatic reflexes
Reflexes that depend on impulse
from muscles are called myotatic
reflexes.
Righting reflex
In spite the basic complexity of
many behavioral acts controlled by
central nervous system, the
responses to some stimuli are
often automatic and are invariable.
If a cat dropped down from a
height , it will land correctly on all
four due to righting reflex.
Hypothalamus
It is located in the middle of brain
above the Pituitary gland and
below the thalamus,and is
surrounded by two cerebral
hemispheres.Although a small
structure,yet it is composed of
relatively large number of nuclei.It
perform many functions of greatest
importance both for survival and
for enjoyment of life.
Role of hypothalamus in feeding
Hypothalamus control the intake
and output of water and
food.Group of neurons in the
hypothalamus when stimulated
make the animal go around sniffing
everything to find out if it is edible
or not.The animal eat fastly when a
strong current is passed through a
particular region of hypothalamus.
Lateral hypothalamus
The lateral part of hypothalamus is
responsible for feeding.To test its
role an experiment was made on
male rats,these rats had electrodes
implanted in Lateral hypothalamus
and were put in cages containing
both nice smelling food and
females.The males immediately
showed intrest in females
Continued…..
but as the current was passed to
stimulate the neurons in Lateral
hypothalamus the male rats left the
females and started eating.
There are also some other factors
that contribute the desire of
feeding process and these are food
shortage etc
APHAGIA
Bilateral lesions located in the area
of the lateral hypothalamus can
produce aphagia. Affected animals
may starve, even with food and
water available
hyperphagia
The lateral hypothalamus had the
feeding center and if this center
was stimulated it caused excessive
eating called as Hyperphagia. It
caused Hypothalamic hyperphagia
syndrome.
Satiety centre
Anand and brobeck observed that
if a center in ventromedial
hypothalamus stimulated aphagia
was caused and its destruction
brought about hyperphagia.They
named this center as Satiety
Center.Hethrington showed that
bilateral destruction of the
ventromedial hypothalamic nuclei
Alone produced obesity,this was
caused by voracious over eating
and was called “ventromedial
hypothalamic syndrome”
Role of hypothalamus in
reproductive behavior
The hypothalamus control
reproductive behavior either
through pituitary or directly. The
pituitary secrete several hormones
concerned with regulation of
sexual behavior and reproductive
physiology.
Hormones of Pituitary
The gonadotropic hormone
stimulate the development of
ovaries and secretion of estrogen
in the female, it trigger
spermatogenesis and secretion of
androgen in the males.
Luteinizing and lactogenic are
involved in the regulation of
maternal activities.
Controlling centre for reproductive
behavior
The nuclei of the hypothalamus
organizing sexual behavior are
situiated in anterior hypothalamus.
Fisher and co workers observed
that female cats with anterior
hypothalamic lesions did not mate.
Role of hypothalamus in reward
and punishment
Olds discovered that there are
groups of nuclei in posterior
hypothalamus which are known as
reward and punishment centre.
Olds implanted electrodes with the
lever which the rat could press,in
the pleasure centre of rat.
Whenever the rat pressed it excited
its own pleasure center.
The rat found it extremely pleasing and
pressed it 5000 times in an hour without
any pause till he fell with exhaustion.
olds kept the same rat in a cage and
starved him, later Olds offer the rat nice
odorous food, but still the rat prefer
pressing the lever to get the pleasure,
rats pressed the lever without any
pause, though tired still he dragged the
body back to lever for more and more
pleasure, the rat did almost anything to
get at lever, even hopped across a
painful electrified grid.
Stimulation of another specific
cluster of nuclei in posterior
hypothalamus causes the animal to
show all the signs of
pain,Displeasure and punishment.
Prolonged stimulation of such area
causes the animal to become
severly sick and sometime this
may even lead to death.
Role of hypothalamus in fighting
and fleeing
Hess discovered that the stimulation of
certain nuclei in lateral and posterior
hypothalamus caused aggression,
attack or fight.He further found that
when he stimulated these neurons in
hypothalamus with the minimal current
the animal just show a state of
vigilance,as the current was increased
the reaction became more intense,
finally when the intensity of the current
was..
Continued…..
Increased more and more at the
same locus in hypothalamus the
animal showed an actual attack.
The cat jumped with rat on
experimenter and when the current
was switched off, the animal
calmed down quickly.
Role of hypothalamus in Sleeping
and waking
Sleep wake phenomenon has been
of great importance and has drawn
attraction of various workers since
earlier. A Russian surgeon reported
a very interesting case of soldier.
On whom he had operated during
war time a metal fragment had
entered the patient skull and had
lodged in the anterior
hypothalamus.
Continued…..
When the surgeon operating under local
anesthesia tried to pull the piece of
metal out the patient immediately fell of
to sleep. the surgeon got upset thinking
that the patient had fainted. after
sometime the patient woke up and when
questioned, said he had an irresistible
urge to sleep. the surgeon drive from
the incidence that the anterior
hypothalamus had the center for
sleep.
Hess reestablished posterior
hypothalamus is a waking center.
In the pathological conditions of
epidemic encephalitis the patient
go into a state of comma this is
due to inhibition in the activity of
posterior hypothalamus.
Hypothalamus and other
activities
Various component of emotional
reactions are organized here. this
center is situated in posterior
hypothalamus and controls fear,
anxiety, pleasure, rage, irritation
and attack. Lesion in this center
can make a person like a vegetable
who is difficult to arouse
emotionally.