Download Control and Coordination

Some important terms
 Stimulus- any external or internal factor that causes a
living organism to react is called a stimulus. (Pl:
stimuli)
 Response- the specific reaction shown by a living
organism towards a stimulus
 Impulse- a electrical wave of excitation or irritation
that travels across a neuron and carries specific
messages.
Some important terms
 Receptors- group of organs that receive
sensory impulses and convey them to
the brain
 Effectors- group of organs that show
responses to a specific stimulus
Neuron The fundamental structural and functional unit of the
nervous system that carries impulses across the body.
Structure of a neuron
A neuron is made up of two main parts;
a) Cyton
b) Axon
Cyton – also called cell body, this part of neuron
contains a large prominent nucleus in the center.
The cell membrane is branched into several cytoplasmic
branches called dendrites.
Dendrites receive the impulses.
Structure of a neuron
The cytoplasm is called neuroplasm.
Inside the neuroplasm are scattered several stainable
granules called Nissl granules.
B) Axon – The long cytoplasmic projection of the neuron that
extends from the cell body.
An axon is covered by an insulating membrane called
Neurolemna.
Axons carry the impulse they receive from the cyton. They
usually terminate into another neuron or an organ or gland
or muscle.
Structure of a neuron
In some neuron there is an additional envelop inside the
neurolemna called the Myelin sheath which help in
faster conduction of the impulse.
Such neurons are called myelinated neurons and are
mostly present in cerebral medulla.
Impulse always travels from Cyton to Axon.
Types of Neurons
 Sensory neurons- Those neurons that carry impulses
from the receptors (sense organs)to the brain. These
impulses are sensory in nature.
 Motor neurons- Those neurons that carry impulses
from the brain to the effectors . These impulses are
motor in nature.
 Associated neurons- They are also called mixed
neurons as they carry impulses both to and from the
brain.
Types of Neurons
Motor
Sensory
Interneuron
Nerves
A bundle of neurons with a common envelop around the
axons called nerve membrane.
A nerve provides a common
pathway for the
electrochemical nerve
impulses that are transmitted
along each of the axons
Types of Nerves
 Sensory nerves- Those nerves that carry impulses from
the receptors (sense organs)to the brain. These
impulses are sensory in nature.
 Motor nerves- Those nerves that carry impulses from
the brain to the effectors . These impulses are motor in
nature.
 Mixed nerves- They are also called mixed nerves as
they carry impulses both to and from the brain. They
are also called spinal nerves.
Classification of the Human
Nervous System
The human Nervous System is classified into three
major divisions-
The Central Nervous System
The Peripheral Nervous System
The Autonomous Nervous System
Central Nervous System
 The CNS constitutes the main division of the Nervous
system in Human Beings.
 It comprises of two main organs concerned with
control and coordinationA) The Brain
B) The Spinal Cord.
The Brain
 Location: Head region
 Protection: a) Body protection made up of immobile
bones that make up the skull. The skull is also called
the Cranium.
b) Membranous protection in the form of three
membranes called the meninges. These three layers are
called – Dura mater, Arachnoid mater and Pia mater.
The cerebro-spinal fluid in between the three layers,
protects the brain further from
Meninges of the Brain
Parts of the Brain
Fore- Brain
The fore brain makes up the largest part of the brain.
The forebrain consists of
the cerebrum,
thalamus,
and hypothalamus (part of the limbic system)
Fore Brain
 Olfactory lobes:
Two small lobe
like structures
situated in the
lower part of the
anterior brain.
Controls the
sense of smell
Fore Brain
The cerebrum is the largest, most prominent part of
the human brain. The longitudinal fissure
partitions the cerebrum into right and left
hemispheres, which are each separated into four
lobes:
 Frontal
 Parietal
 Temporal
 Occipital
 The cerebrum consists of the cerebral cortex
(outer gray matter) and white matter.
 The cerebral cortex is configured into convolutions
(folds) that maximize surface area
 The interior white matter consists of myelinated
axons of neurons that link several regions of the
brain
Lobes of the Cerebrum
 Frontal Lobe- associated
with reasoning, planning,
parts of speech, movement,
emotions, and problem
solving
 Parietal Lobe- associated
with movement,
orientation, recognition,
perception of stimuli
 Occipital Lobe- associated
with visual processing
 Temporal Lobe- associated
with perception and
recognition of auditory
stimuli, memory, and
speech
Fore Brain
Thalamus is between the
cerebral cortex and the
midbrain, both in terms of its
location and its neurological
connections. Its function
includes relaying sensation
and special sense signals to
the cerebral cortex, relaying
motor signals from the
cerebral cortex, and the
regulation of consciousness,
sleep and alertness.
Fore Brain
Hypothalamus
The hypothalamus is a portion of the brain that contains a
number of small nuclei with a variety of functions. One of
the most important functions of the hypothalamus is to
link the nervous system to the endocrine system via the
pituitary gland (hypophysis). The hypothalamus, is located
below the thalamus, just above the brain stem
The hypothalamus is responsible for certain metabolic
processes and other activities of the Autonomic Nervous
System. It synthesizes and secretes neurohormones
Mid Brain
 It consist of Crura
cerebri and
corpora
Quadregemina.
Hind Brain
 Hind brain is
made up of
three parts:
a) Cerebellum
b) Pons
c) Medulla
oblongata
Cerebellum
 The hind part of brain. It is divided into cerebellar
cortex and cerebellar medulla.
 Cerebellar cortex has longitudinal fissures and not
folds. While the medulla looks like a branched tree.
 Cerebellum consists of 12% of the brain.
Functions:
a) It controls muscular co-ordination
b) It regulates body balance.
Medulla Oblongata
 The medulla contains
the cardiac, respiratory,
vomiting and vasomotor
centers and deals with
autonomic functions,
such as breathing, heart
rate and blood pressure
Pons Verolli
 The pons is a structure
located on the brain
stem.
 The pons relays sensory
information between the
cerebellum and
cerebrum, aids in
relaying other messages
in the brain, controls
arousal, and regulates
respiration.
Spinal Cord- Structure
 The spinal cord is an




extension of the brain stem.
It runs mid-dorsally through
the body and innervates the
body.
The Sectional view of the
spinal cord shows the outer
white matter and inner grey
matter.
The inter-neurons are
present in the gray matter
and help in reflexes.
Spinal cord is protected by a
set of 33 bones called
vertebral column and the
three meninges.
Spinal Cord- Structure
 A central canal is filled with the cerebro-
spinal fluid.
 31 pairs of spinal nerves emerge out from
either sides of the spinal cord.
 Spinal nerves are mixed nerves as they have
the sensory as well as the motor neurons in
them.
Functions of the spinal cord
Spinal cord conducts impulses
from the receptors to the brain as
well as from the brain to the
effectors.
Spinal cord controls reflexes.
Reflexes
 A reflex is an involuntary, rapid response towards a
stimulus with the active participation of the brain.
Reflexes are protective responses against harmful
stimuli.
For ex: If we touch a hot plate we recoil our hand
immediately to prevent it from getting burnt. This
immediate and unconscious response is called reflex
 Reflexes can be inborn or acquired.
Reflex Arc
 The path travelled by
an impulse during a
reflex response is
called a reflex arc.
 A reflex arc begins
from the receptors
passes through the
sensory neuron, passes
via the interneuron to
the motor neuron and
then to the effectors.
PNS
 The peripheral nervous system is composed of sensory
neurons and the neurons that connect them to the
nerve cord, spinal cord and brain, which make up the
central nervous system. In response to stimuli, sensory
neurons generate and propagate signals to the central
nervous system which then processes and conducts
signals back to the muscles and glands.
 It is made up of 12 Pairs of Cranial Nerves and 31 pairs
of spinal nerves.
ANS
 The autonomic nervous system (ANS or visceral
nervous system) is the part of the peripheral nervous
system that acts as a control system functioning largely
below the level of consciousness, and controls visceral
functions. The ANS affects heart rate, digestion,
respiration rate, salivation, perspiration, diameter of
the pupils, micturition (urination), and sexual arousal.
Whereas most of its actions are involuntary, some,
such as breathing, work in tandem with the conscious
mind.
It is classically divided into two subsystems: the
parasympathetic nervous system and sympathetic nervous
system
Sympathetic Nervous System
 Promotes a "fight or flight" response,
corresponds with arousal and energy
generation, and inhibits digestion.
 Diverts blood flow away from the gastrointestinal (GI) tract and skin via
vasoconstriction.
 Blood flow to skeletal muscles and the lungs
is not only maintained, but enhanced (by as
much as 1200% in the case of skeletal
muscles).
Sympathetic Nervous System
 Dilates bronchioles of the lung, which
allows for greater alveolar oxygen exchange.
 Increases heart rate and the contractility of
cardiac cells (myocytes), thereby providing a
mechanism for the enhanced blood flow to
skeletal muscles.
 Dilates pupils and relaxes the lens, allowing
more light to enter the eye.
 Inhibits peristalsis.
Parasympathetic Nervous System
 Promotes a "rest and digest" response,
promotes calming of the nerves return to
regular function, and enhances digestion.
 Dilates blood vessels leading to the GI tract,
increasing blood flow. This is important
following the consumption of food, due to the
greater metabolic demands placed on the body
by the gut.
 The parasympathetic nervous system can also
constrict the bronchiolar diameter when the
need for oxygen has diminished.
Parasympathetic Nervous System
 Normalizes Heart Beat levels.
 During accommodation, the parasympathetic
nervous system causes constriction of the pupil
and lens.
 The parasympathetic nervous system
stimulates salivary gland secretion, and
accelerates peristalsis, so, in keeping with the
rest and digest functions, appropriate PNS
activity mediates digestion of food and
indirectly, the absorption of nutrients.
 Is also involved in erection of genitals