Chap_9_Control__Coordination_(2).pptx

Introduction
 Unlike unicellular organisms multicellular organisms need control
& coordination in life processes to maintain homeostasis.
 Plants & Animals show the same, plants by sending chemical
signals, animals through electrical signals as well.
 Plants show phototropic, chemotactic, thigmotactic movements
where as animals show more complexity in them.
 Multicellularity is one of the basic cause of division of labour, led
to the development of organ system organisation.
 Movement & Locomotion have demanded evolution of some
systems (nervous system)

Porifera
 They lack nervous system, efficient
working is brought about by division of
labour.
 This leads to specialization, finally
resulting in formation of organs, organ
systems.
 Nervous system sends electrical signals hence the activity is
immediate & fast.
 Nervous system has evolved from nerve net to ganglionated
nervous system to superior mammalian brain.
 Nervous system renders the ability to animals to respond very
quickly to stimulus.

9.1 Nervous system in Hydra
 Two nerve nets in mesoglea,
one connected to epidermis &
other to gastrodermis.
 Sensory cells are scattered, sense organs absent, no
sensory/motor nerves, no polarity/direction of nerve impulse.
 Activation happens at a point & impulse is carried throughout the
body in any direction.
 This type of system is seen in ctenophora & enteric system/gut
wall of humans as well.
 Diffused & most primitive,
consists of neurons & fibres.
Neurons scattered, connected
by fibres forming nerve net.

 The peripheral nerve plexus arises from VNC laterally. The PNS
includes sensory cells arranged in lateral cords.
 Most primitive with ventrally located central nervous system, it
consists of mass of cerebral/cephalic ganglion (inverted U shaped brain).
 It lies in the anterior/head region & from each ganglion nine
branches arise.
 Ventrally below the ganglia pair of ventral nerve cords are seen,
interconnected by transfer nerve/commissure (ladder like).
9.2 Nervous system in Planaria (flat worms)

 A pair of photo-sensory
structure, the eyes are located
on dorsal side of the brain,
single sensory cells are
scattered in the body.
 The peripheral nerve plexus
arises from VNC laterally. The
PNS includes sensory cells
arranged in lateral cords.
 Gradual evolution has led to development of highly centralized
nervous system from a diffused kind of primitive system.
9.2 Nervous system in Planaria (flat worms)

 Neurons are the quickest means of
transport.
 It is composed of nerve
cells/neurons & neuroglial cells /
supportive cells / Microglial cells /
Oligodendrocytes).
 Considered as impulse generating
& conducting unit.
 They have the property of
excitability & conductivity.
 Neuroglial cells nourish, protect
(phago-cytosis) & support neurons
 In CNS inter-neural space is filled
by non-nervous neuroglial cells (more
than neurons derived from ectoderm).
9.3 Neural Tissue -- Neuron

 Cyton is also called as Cell
body/perikaryon/soma
 Neuron is covered by neurilemma
& differentiated into cyton &
cytoplasmic extensions.
 It contains central nucleus
surrounded by granular cytoplasm
(Nissl’s granules) & network of
neurofibrils
Granules are conical rich in RNA & help in protein synthesis.
 Cell organelles like Mitochondria, RER, Golgi complex are
present.

 Two types of cytoplasmic
extensions appear namely Axons
& Dendrons/Dendrites.
 Axons (longer & single) It carries
impulse away from the cyton.
 Dendrons/Dendrites (small & many)
They carry impulse towards the
cyton

 Axoplasm is in continuation
with cytoplasm of cyton but
lacks Nissl’s granules
 Axon is lined by axonal
membrane enclosing cytoplasm
called axoplasm.
 The terminal end shows many swollen knob like telodendrons
filled with neurosecretory substances.
 Axon is wrapped by sheath of
Schwann cell

Unipolar
 Neurons are of 3 types (depending
on number of processes)
Bipolar
Multipolar
 Cytons of neurons gather &
form ganglions where as the
axons form the nerves
 Depending on the direction of
impulse they carry nerves are of
following types
Sensory Motor
Mixed
Classification of Neurons & Nerve Fibres

Classification of Nerve Fibres
According to presence/absence of myelin sheath nerve fibres are
Medullated/Myelinated Nonmedullated/Nonmyelinated
 Myelin sheath is interrupted by Nodes of Ranvier, jumping of
impulse from one node to other is called as saltatory condition.
Conducts impulse faster.
 The myelin sheath is not
synthesized by the schwann
cells.
Conduct impulse slowly.
 The myelin sheath is
synthesized by the schwann
cells.
 Each nerve is covered by a connective
tissue sheath called as endoneurium,
many nerves are bundled by
perineurium & several bundles are
surrounded by Epineurium
Formation of Nerve Fibres

Excitability
 It is the junction between two nerve cells with a minute gap (synaptic
cleft) consisting neurotransmitter bridge.
Conductivity
 Nerve fibre has the ability to perceive stimulus &
enter into state of activity, whenever it encounters
a polarized membrane.
9.4 Synapse
Properties of nerve fibres
 Ability to transmit excitation

Stimulus
Types of Stimuli
 Any detectable, physical/chemical/electrical
change in the external/internal environment
which brings about excitation in a
nerve/muscle/organ/organism is termed as
stimulus.
9.4.1 Properties of nerve fibres
Threshold Stimulus
 Minimum intensity of
stimulus to be effective
Subliminal Stimulus
 Weak stimulus having no
effect
Supraliminal Stimulus
 Strong stimulus producing
same degree of impulse as
that of threshold stimulus.

Summation effect
 Many weak stimuli (subliminal) in quick succession may produce an
impulse due to addition/summation of stimuli.
All on none law
 In case of weak stimulus the nerve may conduct the impulse along
its entire length or will not at all conduct the impulse.
Refractory period
 Time interval (about millisecond) during which nerve fails to respond
to even a stronger stimulus however strong.
Synaptic delay
 Time required by impulse to cross a synapse (0.3 – 0.5 milliseconds)
required for release of neurotransmitter to be released from axon
terminal & excitation in the dendron of next neuron.

Synaptic fatigue
 Halting of transmission due to exhaustion of neurotransmitter
Velocity
 Rate of transmission of impulse
 Higher in long & thick nerves, homeotherms, voluntary fibres,
medullated nerve fibres
 The neuron carrying impulse to synapse is presynaptic neuron, the
one receiving is post synaptic neuron/generator neuron
(gland/muscle).
 Small intercellular space/synaptic cleft (20 – 30 nm) lies between
them
 Synaptic transmission is conduction of impulse from presynaptic
neuro to post synaptic neuron (one way process).

9.4.2 Types of synapses
Electrical synapse
 Gap is very narrow,
mechanical
 The distance between two cells at gap junctions is about 3.8nm
 Electrical conductive link is
formed between pre & post
synaptic neurons.
 Transmission is faster, found in those places which require fast
response (defense reflexes).
 They are bidirectional or may be unidirectional.

Chemical synapse
 Gap is larger, sends chemicals
 Chemical signals are send to other
neurons or non neural cells.
 The distance between two cells at
gap junctions is about 20-40nm
 Chemical synapse between motor neuron & muscle cell is called
as neuromuscular junction.
 Following are the components of a typical chemical synapse
Presynaptic terminal (mostly axonic terminal)
Synaptic membrane of post synaptic cell
(dendrite of next neuron/ cell/muscle)
Post synaptic neuron
 Impulse travels from axon of presynaptic neuron to axon terminal

Chemical synapse
 When impulse reaches synaptic knob, voltage sensitive Ca++
channels open & Ca++ diffuses inwards from extra cellular fluid.
 These knobs have an array of
membranous sacs called
synaptic vesicles containing
neurotransmitter molecules.
 Most presynaptic neurons /
axons have several knobs at
their ends/terminals.

Chemical synapse
 Increased calcium concentration
initiates a series of events that fuse
the synaptic vesicles with the cell
membrane of pre synaptic neuron,
where they release their
neurotransmitters by exocytosis
 On binding with the receptors, the action is either
excitatory/inhibitory depending on nature of neurotransmitter
involved.
 Once the impulse has been transferred the enzyme like
cholinesterase destroys the neurotransmitter and synapse is ready
to receive new impulse.

 Nerve impulse is a wave of bioelectrical/electrochemical
disturbance passing along a neuron.
9.5 Transmission of nerve impulse
 Transmission is due to electrical charges across the neuronal
membrane.
 Each neuron has a charged cellular membrane with different
voltage on either sides.
 Plasma membrane separates the two solutions which have
approximately same number of ions though chemically the
solutions are different.

 The external tissue fluid has both Na+, K+ with predominance of
Na+ & Cl-, K+ is predominant within the fibre/intracellular fluid.
 This condition of a resting nerve is called as polarised state & it is
established by maintaining excess of Na+ outside.
Polarized state (Excess of Na + outside)

 Excess of K+ with large negatively charged proteins & nucleic
acids are present on the inner side.
 Some amount of Na+ & K+ always leaks but the Na/K pump
maintains the balance actively.
 Against concentration & electrochemical gradient, Na+ is forced
out & K+ is forced inside, this is sodium pump/Na-K exchange
pump.

 This requires energy (ATP). The difference in distribution of ions
produces a potential difference of -50 to -100 millivolts.
 (average -70 millivolts – resting potential).
 This is due to differential permeability, it is more permeable to K+
than Na+ hence more K+ ions diffuse out as compared to Na+
infusion hence the difference in polarity.
 Negatively charged proteins & nucleic acids make overall
negative charge inside & positive charge outside.

 There are not only leakage channels but also gated channels for
Na+/K+ called as voltage gated channels.
 These channels enable the neuron to change its membrane
potential to active potential in response to stimuli.
 The gated channels are separate hence transport of both ions is
done separately.
 During resting potential both these gated channels are closed to
maintain resting potential.

 Change in the state of resting potential is called as depolarization.
Generation of nerve impulse
Depolarization
 It is brought about by influx of Na+ ions through the gated
channels
 Any change/disturbance to the membrane causes influx of Na+
ions, lowering the potential difference (lesser than -70 millivolts), it
makes the membrane more permeable to Na+ ions resulting in
rapid influx (peculiar property of nerve membrane).

 During depolarization the Na+ gates open but not the K+.
 Extra cellular fluid (ECF) becomes electronegative, inner membrane
is electropositive
 Value of action potential is +30 to +60 millivolts, triggering
depolarization in next part while it itself starts repolarization.
 Gated channels are special
as they can change the
potential difference as per
the stimulus, also they
operate separately & are
self closing.

 Change in the polarity
back to original state is
repolarization.
Repolarization
 It occurs after a short
interval called refractory
period.
 The large number of Na+ ions inside changes the permeability of
the membrane allowing more K+ ions by opening the K+ voltage
gates & slowly closing the Na+ ones.
 This is localized activity, K+ ions pass in rapidly as compared to
Na+ ions movement. The Na-K pump becomes operational.
 This self propagating process of producing a wave, depolarization
& repolarization is repeated up to the end of axon terminal

 The action potential cannot travel as a wave of depolarization it
has to jump from node to node & this process is saltatory
condition
Repolarization
 It is faster than the non-medullated fibres (conduction is continuous (50:1))
 In medullated nerves this exchange of ions (between axoplasma & ECF)
takes place at nodes of ranvier where the inhibitory myelin sheath
is absent.

Spinal Nerves
Brain
Spinal Cord
Cranial Nerves Sympathetic
Parasympathetic
Brain
Fore Brain Mid Brain Hind Brain
Cerebrum
Diencephalon
Optic lobes
Optic chiasmata
Cerebellum
Pon varoli
Medulla oblongata

Structure & Functions of Brain & Spinal cord
 Brain & Spinal cord make up central nervous system (CNS),
derived from embryonic ectoderm.
 Nerves from CNS constitute Peripheral
nervous system (PNS) Autonomic nervous
system (ANS) controls all internal organs
& are semi independent in function.
 Vertebral column covers spinal cord.
 Protected in bony box cranium, soft,
whitish, large sized, slightly flattened
about 1300-1500 gms, 30,000 million
neurons.

 Brain & Spinal cord are also
surrounded by connective
tissue membranes called
meninges.
 They are namely; Dura mater,
Arachnoid mater & Piamater
 Dura mater: outermost, tough,
thick & fibrous, attached to inner
side of cranium, protective.
 Arachnoid mater: middle, thin & vascular formed of reticular C.T,
nutritive/ protective (spider web like appearance).
 Piamater: innermost, thin in contact with CNS, highly vascular &
hence nutritive.

 Arachnoid mater & Dura mater separated by subdural space with
serous fluid.
 In between Pia mater &
Arachnoid mater,
subarachnoid space is filled
with lymph like watery fluid
called Cerebrospinal fluid.
 Cerebrospinal fluid secreted by piamater, choroid plexuses &
ependyma cells .

Cerebrospinal Fluid
 Cerebrospinal fluid is alkaline with 1.005 specific gravity. A total
100-120 cc is present in and around CNS.
 Infection to CSF is called as
meningitis.
 The three openings in the roof of medulla oblongata help in
draining out CSF from brain.
 It acts as a shock absorber,
protection against mechanical
injuries, dessication,
maintains pressure &
temperature, also helps in
exchange of nutrients,
oxygen, wastes between blood
& brain tissue.

Human Brain (Encephalon)
Forebrain (Prosencephalon)
Midbrain (Mesencephalon)
Hind brain (Rhombencephalon)
Olfactory lobe (Rhinoncephalon)
Cerebrum (Telencephalon)
Diencephalon (Thalamencephalon)
Corpora quadrigemina
Crura cerebri
Cerebellum
Pons varoli
Medulla oblongata

Fore Brain (Prosencephalon)
 Consists of Olfactory lobes, Cerebrum
& Diencephalon
 Olfactory lobes are small, ventral, solid
bodies covered by cerebrum dorsally.
 Olfactory lobes can be differentiated
into olfactory bulbs & olfactory tracts
(merge with temporal lobe).
 Function is sense of smell (poor in humans due
to small olfactory lobes)
 Olfactory lobes

 Cerebrum is largest, most prominent &
complex (80-85% weight)
 Divided into 2 cerebral hemispheres by
longitudinal fissure.
 Interconnected by transverse thick band
of nerve fibres called corpus callosum
(largest commissure)
 Cerebrum
 Each hemispheres has lateral ventricle
(cavity) filled with CSF, roof is called as
pallium.
 Surface (cerebral cortex), is highly
folded, folds are gyri & sulci, appears
grey due to collection of cytons. (pattern &
arrangement has relationship with intelligence).

 Deeper part is called as
cerebral medulla, made up of
white matter contains axons.
(masses of grey matter in white matter are
called as basal nuclei)
 Ventro lateral walls corpora striata are thick. Central sulcus,
ventral sulcus & parieto-occipetal sulcus forms 4 lobes.
 Cerebrum
 The lateral/sylvian sulcus
demarcates the temporal lobe.+
 As the sulci are not complete
hence the demarcation is
unclear.

 Fifth median lobe called as
insula/insular cortex is folded
deep in the lateral sulcus.
 Grey matter contains cell
bodies of neurons & non
medullated nerve fibres, white
matter contains mainly axons
of myellinated fibres.
 Cerebrum

 Cerebrum – functional areas
 Motor area controls voluntary
motor activities (movement of
muscles).
Frontal lobes
 Pre motor area controls
involuntary movements &
ANS.
 Association area is for coordination between sensation &
movements.
 Broca’s area/motor speech area translates thoughts into speech,
expression of emotions, intelligence, will power, memory,
personality.

 Mainly somasthetic sensation
of pain, pressure, temperature
& taste (gustatoreceptors).
Parietal lobes
 Centre for smell (olfactory),
hearing (auditory), speech &
emotions.
 Visual area, mainly for sense of vision.
Temporal lobes
Occipital lobes
 Area of contact between temporal, parietal and occipital lobes is
centre for Wernicke’s area (understanding spoken & written words).

 Basal ganglia/nuclei are grey
masses within white matter on
the lateral side of thalamus.
 They receive
neurotransmitters, help in
execution of activities at
subconscious level (writing
speed).
 Corpus striatum is largest
basal nucleus at the floor of
cerebrum.

 Diencephalon
 It contains epithalamus, thalamus & hypothalamus.
 Lies below corpus callosum &
above midbrain.
 The cavity is termed as
diocoel/3rd ventricle, it
communicates (with two lateral
ventricles of cerebrum) via foramen
of monro.

 Diencephalon
 Epithalamus is soft, thin roof
of diencephalon, anteriorly
fused with piamater forming
anterior choroid plexus.
 From its dorsal wall it is connected to pineal gland through pineal
stalk.
 Earlier pineal gland was considered vestigeal but later it has been
found that it produces hormone melatonin (sleep inducing hormone & also
related to reproductive behaviour like puberty, pregnancy).
Epithalamus

 Diencephalon
 Lateral thick walls forms
thalami (grey matter). The
habenculor commissure
connects the two thalami.
 Parts of brain are
interconnected by RAS
(reticular activating system)
through thalami, hence called
relay centre (transmits all sensory
impulses except olfactory to cerebrum).
 Diocoel connects posteriorly to IV ventricle by a narrow duct
sylvius/iter
Thalamus

 Diencephalon
 It forms the floor, richly
supplied with blood
(hypothalamus-hypophyseal portal vein)
help in feedback mechanism
for hormonal control.
Hypothalamus
 It maintains homeostasis,
involuntary behaviour control,
internal equilibrium.
 Hypothalamic nuclei (in white matter) with neurosecretory cells
producing oxytocin & vasopressin.

 Diencephalon
 It links the nervous &
endocrine system. It regulates
heart rate, blood pressure,
temperature, water electrolyte
balance.
Hypothalamus
 It has centres for thirst, hunger,
sleep, fatigue, satiety,
secretions (stomach & intestine).
 It also produces neuro-hormone stimulating pituitory.
 A complex neuronal circuit limbic system is formed by
hypothalamus, amygdala, parts of epithalamus & thalamus,
hippocampus & other areas.

 Diencephalon
 It appears to be responsible for
emotional reactions,
motivational drives &
memory.
Hypothalamus
 The floor continues as a
downward projection
hypophyseal stalk or
infundibulum
 The inferior surface bears optic chiasma & a pair of mammillary
bodies (unique in mammals, recollective memory).

Mid Brain (Mesencephalon)
 Located between diencephalon
& pons varoli.
 It contains cerebral
aquedect/iter connecting 3rd &
4th ventricles.
 Corpora quadrigemina are 4
rounded elevations on dorsal
surface of mid brain.
 The two superior colliculi are for visual
reflexes, inferior are relay centres for
auditory reflexes.
 On its inferior surface are two thick
fibrous tracks called crura
cerebri/cerebral peduncles.

Mid Brain (Mesencephalon)
 These tracts are of ascending
& descending nerve fibres
from RAS connecting
cerebrum & midbrain.
 Near the centre , a mass of
grey matter scattered in white
matter is called red nucleus.
 It controls posture, muscle tone modifies motor activities thereby
motor coordination.

Hind Brain (Rhombencephalon)
 Posterior region consisting of,
cerebellum, Pons varoli
(Metencephalon) & medulla
oblongata (Myelencephalon).
 Pons varoli is rounded bulge
on the the underside of brain
stem.
 It contains cross band of nerve
fibres connecting cerebrum,
cerebellar lobes, medulla
oblongata & spinal cord
Pons varoli

 Cerebellum is the second
largest part made up of two
hemispheres & central vermis.
 It is composed of white matter
& a thin layer of grey matter,
intermixes to form tree like
pattern called arbor vitae.
 Surface shows gyri & sulci with deeply situated nuclei in each
hemisphere.
 Three pairs of myellinated nerve bundles called cerebral peduncles
connect cerebellum to other parts of CNS.
Cerebellum

 Main centre for equilibrium, posture, balancing orientation,
moderation of voluntary movements, maintainence of muscle tone.
 It regulates neuromuscular
activities & controls rapid
activities like running,
walking, speaking. Cerebellar
activities are involuntary.
 Medulla oblongata is posterior
conical part continues as spinal
cord.
 It has inner grey matter & outer white matter. It controls vital
functions like heartbeat, respiration, vasomotor activities,
peristalsis.
Medulla oblongata

 It also controls non vital activities like swallowing, vomitting,
sneezing & yawning.
 The cavity is called IV
ventricle or metacoel.
 Its roof has posterior choroid
plexus for secretion of CSF.
 It shows 3 openings a pair of lateral foramen of Luschka & a
median foramen of Magendie.

Spinal Cord
 It is lower extension of medulla oblongata, covered & protected by
bony covering & membranes.
 The CSF secreted by piamater
forms fluid cushion in the
central canal.
 It is lower extension of
medulla oblongata, covered &
protected by bony covering &
membranes.
 Externally it is a 42-45 cm cylindrical rod with 2.0 to 2.5 cm
breadth.

Spinal Cord
 It gradually tapers into conus medullaris (L1 to L2) and continues
as a thread like filum terminale end posteriorly.
 It shows two swellings called
cervical & lumbar swellings.
 31 pairs of spinal nerves arise
from lateral sides,
concentrated in the cervical,
lumbar swellings & conus
medullaris.
 In the hind part the nerves appear as a horse tail hence termed
cauda equina.

T. S of Spinal Cord
 It is dorso-ventrally flattened due to deep, narrow posterior fissure
& shallow broad anterior fissure.
 Fissure divides the spinal cord
incompletely into right & left
side. Central canal is seen at
centre.
 Grey matter is H/butterfly
shaped & on inner side. The
fissure divides the grey matter
into six horns, namely dorsal
lateral & ventral horns.
 White matter is divisible into 6 columns/funiculi, namely dorsal
lateral & ventral funiculi

T. S of Spinal Cord
 The dorsal & ventral horns
extend as dorsal & ventral
roots of spinal cord
respectively.
 Dorsal root is connected to
dorsal root ganglion, lies
outside & lateral to spinal cord
(aggregation of unipolar sensory
neurons).
 Association/inter-neurons lie inside the grey matter. They receive
signal from sensory nerve, integrate it & direct response towards
motor neurons lying towards the ventral horn.
 The lateral horn has the neurons of ANS, nerves arising emerge
from ventral root of spinal nerve.

T. S of Spinal Cord
 Ascending tract conducts sensory impulses from spinal cord to
brain & lie in dorsal column/funiculi. The descending tract
conduct motor impulses from brain to lateral & ventral funiculi of
spinal cord.
Functions
 It is the main centre for reflex action, provides pathway for
conduction of sensory & motor impulses to & fro from brain.
 It provides nervous connection to many parts of the body.
 White matter mainly has ascending & descending tracts made up
of myellinated nerve fibres.

Peripheral Nervous System
 It contains different body parts to brain, it of two types namely;
Cranial nerves Spinal nerves
Connected to brain Connected to spinal cord
12 pairs, sensory, motor, mixed
nerves
31 pairs, only mixed nerves
Formation of Spinal nerve
Sensory – I, II, VIII
Motor – III, IV, VI, XI, XII
Mixed – V, VII, IX, X
Group No. of
Pairs
Region of
origin
Cervical 08 (C1-C8) Neck
Thoracic 12 (T1-
T12)
Thorax
Lumbar 05 (L1-L5) Abdomen
Sacral 05 (S1-S5) Pelvis
Coccyge
al
01 (Col) Coccyx

 Each spinal nerve is formed
by 2 roots the posterior/dorsal
& anterior or ventral inside
the neural canal.
 Anterior root receives sensory
nerve from dorsal root
ganglion (cell bodies of sensory
neurons are in the ganglion) & it
gives out motor nerve.
 The dorsal sensory & ventral motor nerves together form mixed
spinal nerve it emerges out from both sides of spinal cord through
intervertebral foramen.

It shows three branches namely;
Ramus dorsalis Ramus ventralis
Ramus communicans
Skin to muscles Organs & muscles on lateral &
anterior side
From T1 to L3 joins sympathetic ganglia.

 Sudden spontaneous automatic involuntary response to stimulus.
Reflex action
 The path along which the action is carried out is called reflex arc.
 It includes PNS, i.e. the nerves which are of two types;
Afferent nerves Efferent nerves
Transmits sensory impulse from
tissue/organ to CNS
Transmits motor/regulatory
impulses from CNS to
tissues/organs.
 According to recent studies PNS is divided into;
Somatic nervous system Autonomic nervous system
Somatic nervous system relays
impulses from CNS to
skeletal/voluntary muscles
Autonomic nervous system
transmits impulses from CNS to
involuntary organs/smooth
muscles

Types of Reflex actions
Cranial reflexes Spinal reflexes
Unconditional Conditional
 On the basis of control over the actions
Carried out by brain
Slow action response
Eg. Watering of mouth on
sight/smell of good food.
Carried out through spinal cord
Quick acting responses
Eg. Withdrawal of leg while
steeping on pointed object.
 On the basis of previous experiences
Do not require any previous
experience.
Eg. Sneezing, coughing,
yawning, hiccuping
Require previous experience.
Eg. Swimming, cycling, dancing
(Initially voluntary but after perfection
becomes involuntary).

Types of Reflex actions
Simple monosynaptic reflexes Complex polysynaptic reflexes
 On the basis of number of synapses involved
Involves only sensory & motor
neurons.
Eg. Knee jerk reflex
Involves sensory, inter-nervous
& motor neurons.
Eg. Cycling, Swimming

 It is a special set of peripheral nerves which regulates the activity
of involuntary organs like cardiac muscles, smooth muscles,
glands.
Autonomic Nervous System (ANS)
 Impulses are conducted from
CNS by an axon that synapses
with autonomic ganglion
(preganglionic neuron). The second
neuron in this ganglionic
pathway has an axon
extending from autonomic
ganglion to an effector organ
(postganglionic neuron).
 It is made up of
Sympathetic nervous system Parasympathetic nervous system

 It is also called as thoraco-lumbar outflow (T1 to L3), consists of 22
pairs of sympathetic ganglia lie in a pair of sympathetic cords on
lateral side of spinal cord.
Sympathetic Nervous System
 The preganglionic fibres are
short and post ganglionic
fibres are long. Adrenaline &
Noradrenaline is produced at
the terminal ends of post
ganglionic nerve fibres at the
effector organ hence termed
adrenergic fibres.
 It has an excitatory & stimulating effect (except digestive & excretory
organs), response during emergencies (fight or flight response).

 It is also called as Cranio-sacral outflow, consists of branches from
Cranial (III, VII, IX, X), Sacral (II & III) & Spinal nerves (IV).
Parasympathetic Nervous System
 It also consists of ganglia
which are close or within the
wall of effector organ.
 The pre-ganglioic nerves are
long whereas post ganglionic
nerves are short.
 Acetylcholine is produces at
the terminal end of post
ganglionic nerve at effector
organ hence termed as
cholinergic fibres.

 Parasympathetic nervous system in antagonistic to sympathetic
nervous system.
 It brings back to normal all the
activities stimulated by
sympathetic nervous system
(house keeping system).
 Activities inhibited by
sympathetic nervous system
are accelerated by
parasympathetic nervous
system (digestion, micturation,
peristalsis).
Parasympathetic Nervous System

Autonomic Nervous System (ANS)
Sympathetic effect Parasympathetic effect
Organ/Region
Heart beat
Blood vessels
Arterial B.P.
Pupil of eye
Gastrointestinal
movements
Urinary bladder
Increases
Constricts
Retards peristalsis
Relaxes
Decreases
Contracts
Dilates
Accelerates peristalsis
Increases Decreases
Dilates Constricts

9.7 Sensory Receptors
 Sensory receptors are
specialized structures in the
body to receive the various
stimuli for external/internal
environment.
 Nature of receptor is defined
by type of stimuli. A specific
type of stimulus reaches the
sensory neuron, causes
production of an action
potential & it is carried in the
form of impulse.
 These impulses are conducted to the different functional areas of
brain for processing & interpretation.

 Classification Exteroreceptors
Receive external stimuli
Interoreceptors
Receive stimuli from within
Location Function
Name
Phonoreceptors
Statoreceptors
Photoreceptors
Thermoreceptors
Chemoreceptors
Mechanoreceptors
Organ of corti
Semicircular canals
Taste buds
Skin
Sound reception
Touch, pain, pressure
Maintains balance & equilibrium
Taste (sweet, salt, sour, bitter & umami)
Retina of eye vision
Skin Heat (calorireceptors) & cold
(trigidoreceptors)
Gustato
Olfactory Nose
(olfactory epithelium)
10.000 different smells

Interoreceptors
Receive stimuli from within
Location Function
Name
Enteroreceptors
Propioreceptors
Baroreceptors
Internal body organs
Joints, muscles &
tendons
hunger, thirst, pain, osmotic change
Changes in movement of joints, tendons,
muscles; pain, tension & sensitive to
vibrations
Retina of eye vision

Eye
 Located in the orbits of skull with cushion of fat. It is circular,
rounded & termed as eyeball.
 Eyes are protected by bones,
eyebrows, upper & lower
eyelids with eyelashes &
lacrimal/tear glands.
 Movement of eyes are controlled by six set of muscles. Wall of
eyes are made up of 3 layers namely;
Sclera Choroid Retina

Eye
 Outermost, dense fibro-elastic connective tissue with collagen
fibres.
Sclera
 It provides attachment to the
eyeball muscles. Anterior thick
part of sclera is cornea.,
slightly bulged for focusing
light on retina.
 It is provided with blood vessels, except cornea. Cornea is
nourished by aqueous humour & lacrimal secretion.
 Conjunctiva (transperent, membranous) covers exposed part of sclera &
entire cornea providing protection & lubrication.

Eye
 Middle vascular & pigmented layer, divided into choroid proper,
ciliary body & iris.
Choroid/Uvea
 Lines the sclera, pigmentation
avoids internal reflection,
blood vessels provide nutrition
& oxygen.
The choroid proper
 Thick, muscular, ring like at the junction of choroid & iris.
Epithelium secretes aqueous humour.
Ciliary body
 Attached to it are suspensory ligaments holding lens. Ligaments
& muscles help in adjustment of size of lens.

Eye
Iris
 At the junction of sclera & cornea, the vascular part of choroid
sharply bends forming thin coloured partition called as iris.
 Perforated by pupil, , smooth muscles regulate the size, pigment of
iris determines colour of eye.

Eye
 Transparent, elastic, biconvex,
suspended in eyeball by
suspensory ligaments.
Lens
 It divides the cavity into
anterior small aqueous
chamber (clear watery fluid aqueous
humour) & posterior large
vitreous chamber (jelly like
vitreous humour)
 It maintains shape of eyeball & maintains pressure for keeping
lens in position.

Eye
 Innermost, delicate, non vascular light sensitive layer & has two
regions;
Retina
 It has outer pigmented part &
inner nervous part.
 The inner nervous part is
transparent & 3 layered viz;
Outer photosensitive layer of rod & cone cells
Middle layer of bipolar nerve cells
Inner layer of ganglion cells
a. single layer of non sensory part lining iris & ciliary body.
b. sensory part lining the choroid
 The nerve fibres from basal end of ganglion form optic nerve.

Eye
 The area diagonally opposite
to lens is blind spot (no
rods/cones).
Retina
 Optic nerve & blood vessels
leave the eyeball at blind spot.
 Yellow area/macula lutea is lateral to & above blind spot. Fovia
centralis is a depression at its centre.
 It has maximum density of cone cells (sharpest vision).
 Rods/cones lie deep in retina hence light has to pass through the
ganglion & bipolar cells before reaching them.

Eye
Rod cells
Photoreceptor cells
Cone cells
 They are of two types;
 Various combinations of these cones& their photopigments
produce sensation of different colours.
 Cones are responsible for day light vision (photopic) & colour
vision.
 Rods function in dim light (scotopic vision). Purple-red protein
Rhodopsin is a vitamin A derivative.
 They contain light sensitive
proteins termed as photo-
pigments.
 Cones are of three types , having characteristic pigments
responding to red/green/blue lights.

Eye
 Optic nerve has fibres arising from base of the ganglion cells,
carries visual impulses from retina to brain.
Generation of image
 The light rays from object pass
through conjunctiva, cornea
through pupil on lens & then
focused on retina forming
image. In the visual area of
cerebrum the nerve impulses
are analyzed & the image
formed is recognized.
 The sensation of white light is produced due to the simultaneous
stimulation of three types of cones.

• Hormones are produced in response to specific stimulus by ductless
glands called endocrine glands.
• Rate of secretion is very low to very high depending on the nature and
intensity of stimulus
• Produced at one place & effect is on distant organ
• Carried by blood (bound to specific carrier proteins) as they are
produced by ductless glands in blood
• They are highly target specific.
• Modifies some aspect of cellular metabolism.

Pineal gland
Pituitary
Thyroid
Parathyroid
Thymus
Adrenal
Islets of Langerhans (Pancreas)
Testis & Ovaries

• POSITION
• Present below hypothalamus
in depression on the sphenoid
bone called sella turcica
(turkish saddle / hypophyseal fossa).
• Attached by hypophyseal
stalk (infundibulum)
• ORIGIN
• Dual origin – ecto/endo
(nervous & epithelial)

• Size – large Pea, 1.3 cms in dia, 0.5gms in weight.
• Considered as master endocrine gland but now it is
understood that PG is controlled by hormones secreted by
hypothalamus
Dimensions

• Anterior, larger, occupies 75%, develops from Rathke’s
Pouch outgrowth from roof of embryonic buccal cavity.
• Compact, Glandular, vascular and non nervous.
• Made up of Pars distalis, Pars tuberalis & Pars intermedia.
Morphology
Adenohypophysi
s
Anterior lobe
Neurohypophy
sis
Posterior lobe
Pars tuberalis
Pars distalis
Pars intermedia
Pars Nervosa
Infundibulum

• Largest part, enclosed in collagen sheath,
epitheloid secretory cells, separated by
reticular CT with blood sinusoids.
Connected to hypothalamus by portal
system.
Pars tuberalis
• Smaller, extending to hypophyseal stalk, forms collar
around infundibulum. (cells are non -secretory, function is unknown)
Pars intermedia
• Narrow cleft, vestigeal in humans between Pars distalis &
Pars tuberalis, in lower vertebrates secretes MSH

• Posterior part, originates from floor of hypothalamus,
connected by hypophyseal stalk, (nervous & non-glandular). Made
up of Median eminence, Infundibulum & Pars Nervosa
• Median eminence–
swollen median part
where infundibulum
is attached
Median eminence
• Infundibulum/hypophyseal stalk, connects pituitary with
hypothalamus of brain, contains axonic fibres of
neurosecretory cells from hypothalamus
• Lower most, larger contains axons in between pituicytes
Axonic fibres end in knobs called Herrings bodies realease
nuero hormones.

• Two types of cells (50% each)
• Chromophobe /Gamma cells (stain fearing)
• Chromophill (stain loving)
Chromophobe cells
Small, centrally clustered with condensed vesicular nucleus,
contains fine granules called as corticotrophs, act as reserve
cells or precursors of chromophills
Additional reading

• Chromophill (stain loving)
Large with granular cytoplasm, vesicular nucleus, peripherally situated.
Chromophills are of two types namely
Acidophils – alpha cells or oxyphillic cells
• Somatotropes – small, many granules, stained by
orange G Somatotropin
• Lactotropes -- large few granules, Prolactin
Basophils – cynophills
Thyrotropes – agranular or granular (TSH)
Gonadotropes -- Gonadotropins
Corticotopes -- ACTH
Additional reading

• Contains axons & nerve endings of cytons present in hypothalamus &
blood capillaries
• Polygonal neuroglial cells & pituicytes packed in CT.
• Pituicytes are spindle shaped, contains pigments, nerve fibres with
terminal dilated ends called as Herrings corpuscles (axonic knobs).
• Store neurosecretory substance (ADH & Oxytocin)
• Pituicytes – supportive & nutritive cells
• Made up of Median eminence, infundibulum, Pars nervosa.
• Swollen median part of infundibulum -- Median eminence
• Hypophyseal stalk, passage axonic fibres of neurosecretory cells in
hypothalamus
• Pars nervosa -- Lowermost, larger contains axons & pituicytes

• Hormones of Pituitory Gland
• Hormones of Pars distalis
1. Somatotophic hormone (STH)/ Growth Hormone (GH)
Secreted by Acidophils,
Regulated by GHRF & GHIF/Somatostatin (Hypothalamus)
Promotes protein synthesis
Stimulates lipolysis
Promotes cell division
Increases growth of bones
Increases glucose level by increasing insulin.
• Role

• Disorders
• Hypersecretion
Gigantism (in children)
Abnormal increase in height, up to 8 feet
Dwarfism
• Hyposecretion
Acromegaly (in adults)
Elongation of limb bones, neural spines are curved
Lower jaw shows gorilla like appearance
Short stature less than even a metre called as midget. Frohlic
dwarf are mentally abnormal whereas Lorain dwarf are
mentally normal
Simmonds Disease
Sterility, degeneration of sex organs, dry wrinkled skin.

2. Thyroid stimulating hormone (TSH)
Regulated by TRF & negative feedback
Role -- Stimulates thyroid gland to increase uptake of iodine
for synthesis of thyroxine.
• Disorders --- Hyposecretion -- Leads to thyroid atrophy
3. Adreno Cortico Tropic Hormone (ACTH)/ corticotropin
Stimulates growth of adrenal cortex hormones, gluco-
corticoids & mineralocorticoids
Regulated by CRF (corticotropin releasing factor)
Disorders --- Hyposecretion -- Addison’s disease (adrenal
failure), affects carbohydrate metabolism leading to weakness &
fatigue, Hypersecretion -- Excessive growth of adrenal cortex
causing, Cushings disease.

4. Prolactin (PL)Leuteotropic hormone (LTH)
Regulated by PIF (Prolactin inhibiting factor)
Role
As many functions are assigned to PL hence named as follows
Mammotropin – development of mammary glands
Lactogenic hormone – milk secretion by MG
Lueteotropin – maintainence of Corpus luteum
(secretes progesterone reduces chances of pregnancy during lactation)

Regulated by GHRF (hypothalamus)
5. Gonado Tropic Hormone (GTH)/Gonadotropins
Follicle stimulating hormone (FSH), Leutinizing hormone (LH)
/ Interstitial cell stimulating hormone (ICSH)
Role – stimulates germinal epithelium for oogenesis &
development of Graffian follicle, also stimulates secretion of
oestrogen (development of sec. sexual chars in female). In males it
stimulates germinal epithelium of seminiferous tubules for
spermatogenesis
Follicle stimulating hormone (FSH)
Disorder – deficiency leads to infertility in both sexes.

6. Luetinizing hormone (FSH)
Role – stimulates mature Graffian follicle to rupture & release
the ovum. Empty Graffian follicle is changed to corpus luteum
which secretes gestational hormone progesterone(maintainence of
pregnancy). In males it is called as Interstitial cells stimulating
hormone (ICSH) , stimulates interstitial cells/leydig cells to
secrete testosterone (dev. of sec. sexual chars). Feedback mechansim
controls the secretion.

It does not secrete any hormone but stores the secretions of
hypothalamic neurons
• Hormones of NEUROHYPOPHYSIS
1. Anti Diuretic Hormome (ADH)/Vasopressin
Role -- Helps in water conservation by increasing the
permeability of DCT. It also controls constriction of arterioles
to increase blood pressure facilitating ultrafiltration (hence called
Vasopressin). Its secretion is controlled by increase/decrease in
osmotic pressure of blood by feedback manner. Osmo-
receptors (in hypothalamus) detect the osmotic pressure.
Disorders – Deficiency causes Diabetis Insipidus (loss of large
quantity of water through urine – polyuria/diuresis). Polydipsia (increases thirst)
Hypersecretion causes antidiuresis (less urine formation), stimulates
water retention in body fluids.

2. Oxytocin (Birth hormone) – powerful stimulant for
contraction of uterine myometrium at the end of gestation to
initiate labour pains for normal delivery.
Stimulates myoepithelial cells of mammary glands for milk
ejection during breast feeding. Powerful contractions of
uterine musculature drives the sperms upwards towards
fallopian tube.
• Hormones of NEUROHYPOPHYSIS
3. Coherin – induces prolonged, rhythmic integrated
contractions of the jejunum.

Position
Located in anterior region
of neck just below larynx,
ventro-lateral to trachea.
THYROID GLAND contd…..
Externally covered by thin connective tissue capsule.
Origin
Reddish brown in colour, bilobed & highly vascular.
Derived from endoderm.
Morphology
Two lobes are joined by isthmus (C.T)
It gives rise to number of septa called Trabaculae, which
divides interior into lobules contain (3 million) follicles

THYROID GLAND
Dimensions
25-30 gms. in weight,
5cms in length & 3 cms in
width.
 Largest endocrine gland.

It synthesizes, stores & releases Thyroxine hormones.
T3, T4 & Thyrocalcitonin constitutes thyroxine hormomes.
T3– triiodothyronine & T4-- tetraiodothyronine
They are iodinated derivatives of amino acid tyrosine.
TSH/Thyrotropin controls secretion in negative feedback
manner.
HORMONES OF THYROID GLAND

Role
It also controls body weight, respiration rate, heart rate,
blood pressure, temperature, digestion etc.
Disorders
Cretinism – children (retardation of physical & mental growth)
Myxoedema – Adults (thickness/puffiness of skin & subcutaneous tissue of
face & extremeties, low BMR, mental dullness, loss of memory, slow action).
Simple Goitre – deficiency of iodine in diet/water, causes
enlargement of thyroid.
Exopthalmic Goitre (Grave’s disease) – slight enlargement of
gland, increase in BMR, heart rate, pulse rate& B.P, deposition
of fats in eye sockets, muscular weakness & weight loss.

Thyrocalcitonin -- TCT
Secreted by para-follicular cells, regulates blood calcium
level
Stimulates bones to take up Calcium from blood for
deposition of Calcium phosphates.
Increased Calcium levels stimulates C cells to secrete
thyrocalcitonin & viceversa.

PARATHYROID GLAND
Two pairs located on
backside of thyroid.
Secretes peptide hormone --
parathyroid hormone (PTH)
Increases the level of Ca++ in blood – hypercalcemic
hormone
Calcium balance is maintained by TCT & PTH.
Level of Calcium in blood regulates the secretion

THYMUS GLAND
Located on dorsal side of
heart & aorta
Formed of lobules,
develops immune system.
Degeneration of thymus (old-age) weakens the immune
response
Secretes Peptide hormones called Thymosin –
differentiation of T lymphocytes (cell mediated immunity)
Promotes production of antibodies (humoral immunity)

ADRENAL /SUPRARENAL GLAND
Located on upper border of kidney.
Differentiated into outer thick cortex & inner thin medulla
Cortex is further
differentiated into outer
Zona glomerulosa, middle
Zona fasciculata & inner
Zona reticularis.
Hormones of adrenal are called as corticoids.

HORMONES OF ADRENAL /SUPRARENAL GLAND
Mineralocorticoids – electrolyte & water balance
Aldosterone acts on renal tubules & stimulates re-absorption
of Na+ , water, also excretion of K + & Phosphate ions.
Androgenic steroids – role in growth of axial hair, pubic hair
& facial hair on puberty.
Aldosterone thus maintains electrolytes, body fluid volume,
osmotic pressure & blood pressure.
Glucocorticoids – Carbohydrate metabolism
Cortisol stimulates gluconeogenesis, lipolysis & proteolysis
also inhibits cellular uptake & usage of aminoacids.
Cortisol maintains cardiovascular system & kidney functions
Cortisol is also involved in anti-inflammatory reactions &
suppresses immune response, stimulates RBC production.

HORMONES OF ADRENAL /SUPRARENAL GLAND
Adrenaline (Epinephrine) & Noradrenaline (Norepinephrine) –
Catecholamines are produced by medulla in stress
conditions. (emergency hormones/Hormones of fight/flight).
Both the hormones increase alertness, papillary dilation,
pioloerection (hair erection) sweating.
They also increase heartbeats, rate of respiration. It also
stimulates breakdown of glycogen, lipids & proteins
(increases blood glucose level).
Disorders
Addison’s disease – hyposecretion of corticosteroids
Symptoms: Generalized weakness, weight loss, low body
temperature, feeble heart action, low B.P,
Acidosis, Excessive loss of Na + & Cl -

Disorders
Cushing’s disease – hyposecretion of corticosteroids
Symptoms Alkalosis, increased B.P, muscle paralysis,
Polydipsia (increased thirst), increase of electrolytes in
extracellular fluid.

PANCREAS
Glucagon is hyperglycemic,
stimulates hepatocytes for
glycogenolysis &
gluconeogenesis, reduces
glucose uptake &
utilization.
Dual gland, endocrine part is Islets of Langerhans
It has 3 types of cells viz; α cells (Glucagon), β cells (Insulin), δ
cells (somatostatin)

Insulin is hypoglycemic, stimulates hepatocytes &
adipocytes for cellular uptake & utilization of glucose.
Prolonged hyperglycemia leads to diabetis mellitus
Somatostatin decreases
Glucagon & Insulin.
PANCREAS contd….

Present in scrotal sacs in males (reproductive organ & endocrine gland)
Made up of seminiferous tubules & interstitial/leydig cells.
Hormones produced by leydig cells are called as androgens
(steroids). Most significant androgen is testosterone
TESTIS
Regulates & stimulates development, maturation &
functions of reproductive organs.
Stimulate muscular growth,
facial hair, aggressiveness,
low pitch

OVARY
Present in abdomen, secretes Estrogen & progesterone
(steroids)
Estrogen stimulates growth of female reproductive organs,
also regulates female sexual behaviour
It also controls secondary sexual characters like pitch of
voice, mammary glands, broadening of pelvis, pubic hair&
deposition of sub-cutanesous fats.
Empty grafian follicle
forms corpus luteum which
secretes progesterone
It maintains pregnancy, stimulates lactation.

Hormones of Gastrointestinal tract
Hormones secreted in the GE tract are Gastrin, Secretin,
cholecystokinin (CCK) & Gastric inhibitory peptide (GIP)
Gastrin stimulates gastric glands for Hcl & Pepsinogen
Secretin acts on pancreas for pancreatic juice (water &
bicarbonate ions forms pancreatic juice)
CCK stimulates gall bladder for bile & also pancreas.
GIP inhibits gastric secretion & motility.

Hormones of Heart
Atrial natriuretic factor (ANF) is secreted when B.P increases.
It causes dilation of blood vessels & B.P decreases.
Hormones of Kidney
Juxtaglomerular cells form Erythropoietin stimulating bone
marrow to form RBC’s (erythropoiesis).
Hypothalamus
Many groups of cells secrete hypothalamic neuro-hormones
These cells are termed as nuclei viz; supraoptic,
paraventricular, dorsomedian, ventromedian

Hormones as Messengers & Regulators
Target tissue has hormone receptors (i.e. specific binding sites).
They are either on the cell membrane (membrane bound receptors)
or intracellular.
The binding results in the formation of hormone receptor
complex (hormones & receptors are specific).
Their formation leads to certain biochemical changes in the
target tissue thus regulating the metabolism & physiology is
regulated.
Hormones interacting with membrane bound receptors
generate secondary messengers (cyclic AMP, Ca++ or IP3 Inositol
triphosphate).
Secondary messengers regulate cellular metabolism.

Hormones as Messengers & Regulators
Intracellular hormones (Steroid hormones, Thyroxine) interact with
intracellular receptors present in the nucleus.
It interacts with the genome to evoke biochemical changes
resulting in physiological & developmental functions (regulate
gene expression or chromosome function).
Hormone receptor complex is thus formed inside the
nucleus.

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