Transcript COORDINATION_IN_MAMMALS__A

Coordination in Mammal
 coordination is the way in which receptors
detect stimuli, and then nerve impulses are
sent to the effectors
 in mammals, coordination is carried out
through the activities of nervous system and
the endocrine system
 nervous coordination is brought about by
transmission of nerve impulses between
receptors and effectors through nerve
fibres
 endocrine coordination is brought about by
hormones secreted from endocrine glands
What is Nervous Coordination ?
 nervous system of mammal consists of central
nervous system(CNS) and peripheral nervous
system
 CNS includes brain and spinal cord and the
peripheral nervous system includes cranial
nerves and spinal nerves
Structure of Neurones
 neurones make up nervous system in mammal
 each neurone has a cell body and nerve fibres
 cell body is a mass of cytoplasm with nucleus
inside and it is called ganglion
 nerve fibres are cytoplasmic processes of
neurones and there are two types, one is
dendron and the other is axon
 dendron transmits nerve impulses towards
cell body while axon transmits nerve
impulses away from cell body
 nerve fibres may be protected by a fatty layer
which serves as an insulator to prevent the
spread of nerve impulses and help to speed
up the rate of transmission
cytoplasm
dendron
nucleus
cell membrane
direction of
nerve impulses
axon
nucleus of cell which
makes the myelin
sheath
Types of Neurones
 there are three types of neurones: sensory
neurone, motor neurone and association
neurone
- sensory neurone: transmits nerve impulses
from receptor to the central nervous system
sensory neurone
- motor neurone: transmits nerve impulses
from central nervous system to effectors. The
axon branches at its end to form many motor
end plates which are attached to muscle
fibres
motor
neurone
- association neurone: connects the sensory
neurone to the motor neurone and also the
neurones in the central nervous system
Nerve
neurone
 bundles of nerve fibres
 usually myelinated and
surrounded by a sheath of
white connective tissue
nerve
nerve fibre
 impulses do not jump from one fibre to
another because of the presence of fatty
substance in nerve
 in sensory nerves, there may be ganglia
where the cell bodies are situated
 nerve fibres found inside the central
nervous system do not have insulating
fatty layers
neurone
Nerve Impulses Transmitted
in Nerve Fibre
 stimulation of the
receptors may initiate
nerve impulses and
this follows
“All-Or-None” principle
 ALL impulses are alike regardless of the
site from which they are fired off
 impulses travel very quickly in one
direction from dendron to axon of the same
neurone
Nerve Impulses Transmitted
across the Synapse
neurones are not in direct contact with each other.
A small gap called synapse exist between two
neurones
impulses need to jump across the synapse as to
travel from one end of axon to dendron of another
neurone
Synapses
synapse
ending of axon secretes a
chemical which diffuses
into synapse and stimulates
the next neurone to pass
on the impulse
the chemical is unstable
and will be destroyed
later
presence of synapse enables nerve impulses
to travel only from axon of one neurone to
dendron of another neurone
it also allows higher level of nervous
coordination as one neurone can be linked
with a number of other neurones
Central Nervous System
• includes brain and
spinal cord in higher
animal
brain
spinal cord
skull
Protection of Central
Nervous System
 brain is enclosed in cranium of
skull while spinal cord is enclosed
in vertebral column
 CNS is also enveloped in three layers
of meninges and between the inner
vertebral two layers is a cavity filled with
column cerebrospinal fluid
Functions of
Cerebrospinal Fluid
act as a cushion for absorbing external shock
nourish neurones inside as it enables
diffusion of oxygen and food to the nerve cells
it also filled up cavity called ventricle in brain
and in the central canal of spinal cord
it also helps in preventing collapse of CNS
External view of the brain
Parts of Brain
brain is divided into three main parts: cerebrum,
cerebellum and medulla oblongata
cerebrum
cerebellum
medulla
oblongata
Brain--Cerebrum
 lies in the front part of brain and divided into
two cerebral hemispheres connected by nerve
fibres
 surface of cerebrum is highly folded to
increase area for coordination
 centre of thinking, memory, reasoning,
imagination, learning and voluntary actions
 divided into three functional areas
- sensory areas: receive impulses from receptors
- motor areas: send out impulses to effectors
- association area: correlates impulses from
different receptors and assists in producing
appropriate responses
motor area
sensory area
association
area
Brain--Cerebellum
 lies below the back part of cerebrum
 centre for muscular coordination and involved
in control of body balance
 damage of cerebellum will lead to a loss of
ability to maintain balance
Brain--Medulla Oblongata
lies at the floor of cerebellum
reflex centre for controlling involuntary
actions such as breathing, heartbeat,
swallowing, coughing, sneezing and salivation
damage of medulla oblongata may lead to
death
Medulla oblongata
medulla
oblongata
Internal Structure of Cerebrum
and Cerebellum
outer layer is made up of gray matter which
consists of nerve cell bodies
inner layers consist of nerve fibres and is
white in colour and is called white matter
Internal Structure of
Medulla Oblongata
outer layer is made up of white matter while
inner layer is made up of grey matter
Internal Structure of Spinal Cord
 arises from medulla oblongata and runs
through backbone of mammal
 internal distribution of nerve cell bodies is
similar to medulla oblongata which the
outer cortex contains white matter while
the inner cortex is in H-shaped and contains
grey matter
 in the central region of grey matter is
central canal and filled with cerebrospinal fluid
 reflex centre for controlling involuntary actions
and it also transmits impulses to and from brain
white matter
grey matter
central canal
spinal cord
spinal nerve
Grey & White Matters
cerebrum &
cerebellum
grey matter
(cell body)
outer region
white matter
(nerve fibre)
inner region
spinal cord &
medulla oblongata
inner region
outer region
Peripheral Nervous System
consist of cranial nerves
and spinal nerves
these nerves leave CNS
and run out to every part
of the body
spinal
nerve
cranial
nerve
Cranial Nerves and Spinal Nerves

Cranial Nerve
- twelve pairs of cranial nerves in mammal
- most of cranial nerves arise from lateral sides
of medulla oblongata

Spinal Nerve
- there are 31 pairs of spinal nerves in human
Spinal Nerve
dorsal root ganglion
receptor sensory neurone
(pain)
effector
(muscle)
motor neurone
dorsal root (sensory nerve)
association
neurone
spinal cord
ventral root (motor nerve)
- all are mixed nerve carrying both sensory
and motor neurones
- each spinal nerve has a dorsal root and
ventral root
- dorsal root contains ganglion which contains
nerve cell bodies
- cells in dorsal root ganglion are sensory
neurones and impulses travel through dorsal
root to spinal cord from spinal nerve
- ventral root carries motor nerve fibres and their
cell bodies are found in H-shaped grey matter of
spinal cord
Experiment to Initiate
Knee Jerk Reflex
What happens to the leg immediately after tapping?
Ans: It kicks up at once.
Does the same action occur again if the knee is
tapped the second time?
Ans: Yes.
Reflex Action
 simple reflex action is a quick, inborn and
automatic response of an animal to a stimulus
and cerebrum does not involve in the response
 protective in function and need not be learnt
 same stimulus initiates the same responses at
different times
 examples like withdrawal from hot objects,
blinking, coughing, sneezing and pupil size
Reflex Arc
 neural pathway between receptor and effector
involved in a reflex action
 example is knee jerk reflex
Knee Jerk Reflex
 At the Receptor
 receptor receives stimulus. In this case,
tapping stimulates tendon of knee cap
 At the Sensory Neurone
 from ending of dendrons of sensory neurones,
nerve impulses fired off
 Across the Synapse to the Motor Neurone
 through dorsal root of spinal nerve, impulses
are carried to spinal cord
 impulses jump across synapses to motor
neurones in grey matter but in other reflex
action, association neurones may involve
 To the effector
 impulses are further transmitted through
ventral root to effector to produce responses
 in knee jerk, effector is muscles in upper leg
which it will contract when impulses are
received so the leg jerks up and it is an
example of spinal reflex action as only spinal
cord is involved
Reflex arc : sensory, association,
motor neurones
dorsal root ganglion
receptor sensory neurone
(pain)
effector
(muscle)
motor neurone
dorsal root (sensory nerve)
association
neurone
spinal cord
ventral root (motor nerve)
 spinal reflexes can occur in deep sleep and do
not depend on awareness but impulses can
still pass form sensory neurones up the spinal
cord to brain
 other reflex actions like blinking, coughing and
sneezing are cranial reflex action and take
place in medulla oblongata
Voluntary Actions
conscious response to a certain stimulus
involves cerebrum of brain and mammals are
aware of all the steps of the response
may differ from time to time as mammals can
gain experiences and store them in cerebrum
so they can choose how to response to the
same stimulus
Neural Pathway of
Voluntary Action
receptor receives stimulus
sensory neurone carries
nerve impulses to CNS
association neurone carries
impulses to cerebrum
motor neurone carries
impulses to effector
effector gives responses
Comparison between Reflex
& Voluntary Actions
reflex action
voluntary action
pathway taken
by nerve
impulses
not
involving
cerebrum
involving
cerebrum
control
automatic, not
under control of
the will
voluntary, under
control of
the will
speed of
response
response to the
same stimulus
reflex action
voluntary action
quicker
slower
always the
same
different,
depend on
learning from
previous
experiences
To measure your
Reaction Time
mark on
your thumb
Does your reaction time improve with practice ?
Ans: Yes.
mark on
your thumb
Was your reaction time quicker with or without the ruler
touching your hand?
Ans: The reaction time was quicker without ruler
touching the hand.
mark on
your thumb
Explain.
Ans: It is because the sensory pathway from eye to brain is
much shorter than that from finger-tips to the brain.
Endocrine Glands
 ductless glands in body
 secrete chemical messengers called
hormones which diffuse directly into
the blood
 hormones are
carried to target
organs by
bloodstream
Specificity and Effect of
Endocrine Glands
 usually, target organ
respond to a particular
hormones only so
hormones are specific
 hormonal coordination is slow and takes a
longer time for response to appear but its
effect can last for a long period of time
Comparison between Nervous
& Hormonal Coordination
nature of
message
transmitted
method of
transmission
nervous
coordination
hormonal
coordination
nerve impulse
hormone
nerve impulses hormones carried
transmitted along by blood vessels
nerve fibres
nervous
coordination
hormonal
coordination
rate of producing
response
fast
slow
duration of
effects
short-term
long-term
area affected
localised to
muscles and glands
widespread
throughout the
whole body
Locations of Endocrine Glands
 pituitary gland: locate below cerebrum and it
controls many other endocrine
glands activities in body
 thyroid glands: in neck
 islets of Langerhans: in pancreas
 adrenal glands: above kidney
 ovaries: in female’s abdominal cavity
 testes: in male’s scrotal sacs
pituitary
Sites of Six Main Endocrine
Glands in Human Body
Negative Feedback
Mechanism
 secretion of hormones follows negative feedback
mechanism which means that any decrease in
the level of a factor switches on a series of
corrective actions to restore the factor to normal
level and vice versa
 an example is insulin which is secreted by islets
of Langerhans in pancreas to liver through blood
vessels to control blood glucose level
in pancreas
more insulin
secreted
liver
glucose
glycogen
+
more glucose
taken up by cells
for respiration
high blood
glucose level
after a
heavy meal
normal blood
glucose level
normal blood
glucose level
long time after
a meal
low blood
glucose level
liver
glycogen
glucose
+
less glucose
taken up by cells
for respiration
in pancreas less
insulin secreted
Effect of Sex Hormones
 puberty occurs between the ages of 11-14 years
when a child become sexually mature
 ovaries in females and testes in males become
functional and secrete sex hormones for
development of secondary sexual characteristics
which are physical changes for sexual
awareness
Secondary Sexual Characteristics
Boys
Girls
growth of pubic hair
and hair on face (facial
hair) and in armpits
(axillary hair)
growth of pubic
hair
breaking of voice and
enlargement of larynx
growth and development
of breasts
Boys
Girls
muscle development
widening of
hips(pelvic girdle)
widening of shoulders
more fat deposits
under skin
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