Chapter 6: Control and Coordination

Introduction to Control and Coordination:

 Living organisms respond to environmental changes through coordinated actions. For example, we
adjust to temperature changes or move away from danger.
 In animals, control and coordination are managed by the nervous system and hormonal system,
while plants rely on hormones and chemical signals.
Importance of Coordination:
 Coordination ensures that different parts of the body work together efficiently. For instance, when
we touch something hot, our hand pulls away instantly while we also become aware of the pain.
 This process involves the nervous system detecting the stimulus, processing it, and triggering a
response, alongside chemical coordination (hormones) that supports longer-term responses.

Systems for Control and Coordination in Animals

→ Control and Coordination in animals is done with the help of two main systems:
(i) Nervous system
(ii) Endocrine system

Nervous system: The nervous system is composed of specialized tissues, called nervous tissue. The nerve cell or
neuron is the functional unit of the nervous system. It is the nervous system which is mainly responsible for control
and coordination in complex animals.

Receptors: Receptors are the specialized tips of the nerve fibres that collect the information to be conducted by the
nerves.
Receptors are in the sense organs of the animals.
These are classified as follows:

1. Phono-receptors: These are present in inner ear. Functions: The main functions are hearing and balance of
the body.

2. Photo-receptors: These are present in the eye. Function: These are responsible for visual stimulus.

3. Thermo-receptors: These are present in skin. Functions: These receptors are responsible for pain, touch and
heat stimuli.

4. Olfactory-receptors: These are present in nose. Functions: These receptors receive smell.
5. Gustatory-receptors: These are present in the tongue. Functions: These helps in taste detection.
Neuron
It is the structural and functional unit of nervous system.

Parts of Neuron
(i) Dendrite: It acquires information.
(ii) Cell body: The information acquired by it travels as an electrical impulse.
(iii) Axon: It is the longest fibre on the cell body is called axon. It transmits electrical impulse from cell body to
dendrite of next neuron.
Synapse: It is the gap between the nerve ending of one neuron and dendrite of the other neuron. Here, electrical
signal is converted into chemical signal for onward transmission.

Neuron Functioning or nerve impulse transmission within neuron:

1. Reception: Dendrites detect a stimulus, creating an electrical impulse via a chemical reaction.

2. Transmission: The impulse travels from dendrites to the cell body, then along the axon.

3. Chemical Release: At the axon terminal, the impulse triggers the release of neurotransmitters.

4. Synaptic Transfer: Neurotransmitters cross the synapse, starting an impulse in the next neuron’s dendrite.

5. Final Delivery: The impulse reaches muscles or glands via synapses, enabling a response.

Types of neurons

1. Sensory neuron: These neurons receive signals from a sense organ.

2. Motor neuron: These neurons send signals to a muscle or a gland.

3. Inter or relay neuron: These neurons relay the signals between sensory neuron and motor neuron.

Neuromuscular Junction (NMJ): NMJ is the point where a muscle fibre comes in contact with a motor neuron
carrying nerve impulse from the control nervous system.

Transmission of nerve impulse: Nerve impulses travel in the following manner from one neutron to the next:
Dendrites → cell body → axon → nerve endings at the tip of axon → synapse → dendrite of next neuron.
Chemical released from axon tip of one neuron, cross the synapse or neuromuscular junction to reach the next cell.

Human Nervous System:

The nervous system in humans can be divided into three main parts:

1. Central Nervous System: The central nervous system is composed of the brain and the spinal cord. The brain
controls all the functions in the human body. The spinal cord works as the relay channel for signals between the brain
and the peripheral nervous system.

2. Peripheral Nervous System: The peripheral nervous system is composed of the cranial nerves and spinal nerves.
There are 12 pairs of cranial nerves. The cranial nerves come our of the brain and go to the organs in the head region.
There are 31 pairs of spinal nerves. The spinal nerves come out of the spinal cord and go to the organs which are
below the head region.

3. Autonomous Nervous System: The autonomous nervous system is composed of a chain of nerve ganglion which
runs along the spinal cord. It controls all the involuntary actions in the human body. The autonomous nervous system
can be divided into two parts:

 Sympathetic nervous system.

 Parasympathetic nervous system.

Sympathetic Nervous System: This part of the autonomous nervous system heightens the activity of an organ as per
the need. For example, during running, there is an increased demand for oxygen by the body. This is fulfilled by an
increased breathing rate and increased heart rate. The sympathetic nervous system works to increase the breathing
rate the heart rate, in this case.

Parasympathetic Nervous System: This part of the autonomous nervous system slows the down the activity of an
organ and thus has a calming effect. During sleep, the breathing rate slows down and so does the heart rate. This is
facilitated by the parasympathetic nervous system. It can be said that the parasympathetic nervous system helps in
the conservation of energy.

Structure of the Human Brain

The human brain is a complex organ protected by the skull and surrounded by protective membranes called
meninges. It is divided into three main regions:

1. Forebrain:
o Main Parts:
 Cerebrum: The largest part of the brain, divided into two hemispheres (left and right). It has
a wrinkled surface to increase its surface area.
 Thalamus and Hypothalamus: Smaller structures beneath the cerebrum.
o Functions:
 Cerebrum: Controls thinking, memory, reasoning, intelligence, emotions, and voluntary
actions (e.g., writing, speaking).
 Thalamus: Relays sensory information (like touch, pain) to the cerebrum.
 Hypothalamus: Regulates body temperature, hunger, thirst, and hormone release (via the
pituitary gland).
2. Midbrain:
o Location: A small region between the forebrain and hindbrain.
o Function:
 Controls reflex movements of the head, neck, and eyes in response to visual and auditory
stimuli (e.g., turning your head to a sound).
 Also involved in regulating muscle tone and posture.
3. Hindbrain:
o Main Parts:
 Cerebellum: Located at the back of the brain.
 Pons and Medulla Oblongata: Located below the cerebellum, connecting the brain to the
spinal cord.
o Functions:
 Cerebellum: Maintains balance and posture; coordinates voluntary movements (e.g.,
walking, dancing) for precision.
 Pons: Acts as a bridge, relaying signals between different parts of the brain; also regulates
breathing.
  Medulla Oblongata: Controls involuntary actions like heartbeat, breathing, and swallowing;
also regulates activities like sneezing and vomiting.

Spinal cord: The brain is connected to the spinal cord, which extends from the medulla oblongata and
runs through the vertebral column. The spinal cord helps relay signals between the brain and the body and
coordinates reflex actions.
The brain and spinal cord together form the central nervous system (CNS), which is the main control centre
for the body.

Protection of Brain and Spinal Cord

Protection of Brain: Brain is protected by a fluid {Cerebro-spinal fluid} filled balloon which acts as shock
absorber and is enclosed in cranium (skull or brain box).
Protection of Spinal Cord: Spinal cord is enclosed in vertebral column.

Reflex Action:
 Definition: A reflex action is an automatic, rapid response to a stimulus that doesn’t involve conscious
thought. For example, pulling your hand away from a hot object.

 Purpose: Reflex actions protect the body from harm by enabling quick responses to dangerous stimuli.

Reflex Arc (Diagram):

 The diagram illustrates the pathway of a reflex action, known as the reflex arc.

 Components of the Reflex Arc:

1. Receptor: Detects the stimulus (e.g., heat on the skin).

2. Sensory Neuron: Carries the signal from the receptor to the spinal cord.

3. Spinal Cord: Processes the signal and sends a response (bypassing the brain for speed).

4. Motor Neuron: Carries the response signal from the spinal cord to the effector.

5. Effector: The muscle or gland that acts (e.g., the muscle in your arm contracts to pull your hand
away).

Pathway: Stimulus → Receptor → Sensory Neuron → Spinal Cord → Motor Neuron → Effector → Response.

Muscular Movements and Nervous Control: Muscle tissues have special filaments, called actin and myosin.
When a muscle receives a nerve signal, a series of events is triggered in the muscle. Calcium ions enter the
muscle cells. It results in actin and myosin filaments sliding towards each other and that is how a muscle
contracts. Contraction in a muscle brings movement in the related organ.
Endocrine System: The endocrine system is composed of several endocrine glands. A ductless gland is called
endocrine gland. Endocrine gland secretes its product directly into the bloodstream. Hormones are produced in the
endocrine glands. Hormone is mainly composed of protein. Hormones assist the nervous system in control and co-
ordination. Nervous do not react to every nook and corner of the body and hence hormones are needed to affect
control and coordination in those parts. Moreover, unlike nervous control, hormonal control is somewhat slower.

Hormones: These are the chemical messengers secreted in very small amounts by specialised tissues called ductless
glands. They act on target tissues/organs usually away from their source. Endocrine System helps in control and
coordination through chemical compounds called hormones.

Endocrine Gland Location Hormones Produced Functions

Releasing and inhibiting

hormones (e.g.,
Thyrotropin-Releasing
Brain (above Hormone TRH, Regulates pituitary gland; controls growth,
Hypothalamus
pituitary) Corticotropin-Releasing metabolism, reproduction
Hormone CRH,
Gonadotropin-Releasing
Hormone GnRH)

Growth Hormone GH,

Thyroid-Stimulating
Hormone TSH,
Stimulates: Growth (GH), thyroid function (TSH),
Pituitary Brain (base, below Adrenocorticotropic
adrenal activity (ACTH), reproduction (FSH, LH),
(Anterior) hypothalamus) Hormone ACTH, Follicle-
milk production (PRL)
Stimulating Hormone
FSH, Luteinizing Hormone
LH, Prolactin PRL.

Pituitary Brain (base, below Oxytocin, ADH Labor and breastfeeding (oxytocin), water balance
(Posterior) hypothalamus) (vasopressin) (ADH)

Thyroxine (T4),
Neck (below Metabolism regulation (T3, T4), calcium
Thyroid Triiodothyronine (T3),
Adam’s apple) homeostasis (calcitonin)
Calcitonin

Neck (behind Parathyroid hormone

Parathyroids thyroid) (PTH)
Regulates calcium and phosphate levels in blood

Stress response, metabolism (cortisol), blood

Cortisol, Aldosterone,
Adrenal (Cortex) Top of kidneys pressure, electrolyte balance (aldosterone), sex
Androgens
characteristics (androgens)

Epinephrine, Fight-or-flight response, heart rate, blood

Adrenal (Medulla) Top of kidneys
Norepinephrine pressure

Pineal Brain (near center) Melatonin Regulates sleep-wake cycle

Abdomen (behind Insulin, Glucagon, Blood sugar regulation (insulin, glucagon), inhibits
Pancreas
stomach) Somatostatin hormone release (somatostatin)

Female reproductive development, pregnancy

Ovaries Pelvis (females) Estrogen, Progesterone
maintenance

Male reproductive development, sperm

Testes Scrotum (males) Testosterone
production, secondary sex characteristics
Iodised salt is necessary because: Iodine mineral is essential part of thyronine hormone so it is important that we
must consume iodised salt as in turn it is essential for thyroid gland as it controls carbohydrate, proteins and fat
metabolism for best balance of growth deficiency of iodine might cause disease called goitre.

Diabetes:
Cause: It is due to deficiency of insulin hormone secreted by pancreas that is responsible to lower/control the blood
sugar levels.

Treatment: Patients have to internally administer injections of insulin hormone which helps in regulating blood-sugar
level.

Feedback mechanism: A type of self-regulating mechanism in which the level of one substance in body influences
the level of another.

Here's a breakdown of the process:

1. Sugar Level in the Blood Rises: This occurs after eating, when glucose levels increase.

2. Detected by Cells of Pancreas: Beta cells in the pancreas sense the elevated blood sugar.

3. Synthesize Insulin: The beta cells produce and release insulin into the bloodstream.

4. Blood Sugar Level Falls: Insulin facilitates glucose uptake by cells (e.g., muscle and fat cells), lowering blood
sugar levels.

5. Stop Secreting More Insulin: Once blood sugar levels drop to a normal range, the pancreas reduces insulin
secretion, completing the feedback loop.

The "switch off" mechanism, likened to a float in a water tank, ensures insulin secretion stops when blood sugar is
adequately lowered, preventing hypoglycaemia. This is a classic example of a negative feedback system in the
endocrine system, maintaining homeostasis.

In case of flight or fight reaction to an emergency situation:

Adrenal glands → release adrenaline into blood → which acts on heart and other tissues → causes faster
heart beat → more oxygen to muscles → reduced blood supply to digestive system and skin → diversion
of blood to skeletal muscles → increase in breathing rate.
Control and Coordination in Plants: Movements and Plant Hormones
Plants lack a nervous system, so they rely on chemical coordination through plant hormones to control growth,
development, and responses to stimuli. Movements in plants are categorized into two main types: tropic movements
(directional, growth-dependent) and nastic movements (non-directional, often due to water balance changes). Below
is a detailed breakdown of the movements and the roles of plant hormones.

Movements in Plants

1. Tropic Movements
Tropic movements are directional responses to stimuli, driven by differential growth in plant parts.

Type Stimulus Description Examples

Geotropism Gravity Growth in response to gravity. Roots show positive Roots growing
geotropism (grow downward), while stems show negative downward, stems
geotropism (grow upward). growing upward.

Phototropism Light Growth in response to light. Stems exhibit positive Stem bending toward
phototropism (grow toward light), roots show negative sunlight in a
phototropism (grow away). This is due to higher auxin levels container with a
on the shaded side, causing faster cell division there. hole.

Hydrotropism Water Growth toward a water source. Roots show positive Roots growing
hydrotropism. toward the nearest
water source in soil.

Thigmotropism Touch Growth in response to touch. Tendrils of climbers grow and Tendrils of climbers
coil around supports due to differential cell division driven by coiling around a
auxin. support.

2. Nastic Movements
Nastic movements are non-directional responses to stimuli, often caused by changes in water balance in cells rather
than growth.
Type Stimulus Description Examples
Nastic Touch (or Independent of the direction of the Mimosa leaves drooping when
Movement other stimuli) stimulus. Caused by changes in turgor touched due to water loss in cells,
pressure (water balance) in cells. making them flaccid.
Plant Hormones
Plant hormones (phytohormones) are chemical messengers that regulate growth, development, and responses to
environmental stimuli. The main hormones and their roles are:

Hormone Synthesis Functions

Location

Auxin Shoot tip Promotes cell elongation and growth; drives phototropism (more growth on
the shaded side) and thigmotropism (e.g., tendril coiling).

Gibberellins Various tissues Stimulates stem elongation, seed germination, and flowering.

Cytokinin Roots, growing Promotes cell division; delays aging of leaves.

tissues

Abscisic Acid Mature leaves, Inhibits growth; promotes dormancy, wilting of leaves under stress (stress
(ABA) seeds hormone); helps plants cope with drought.

How Hormones Tie to Movements

 Auxin is critical for tropic movements like phototropism and thigmotropism. In phototropism, auxin
accumulates on the shaded side of the stem, causing cells there to elongate more, bending the stem toward
light. In thigmotropism, auxin drives differential growth in tendrils for coiling.

 Nastic Movements (e.g., in Mimosa) are not hormone-driven but result from turgor pressure changes.
However, hormones like abscisic acid can indirectly influence such responses by managing stress-related
water loss.

Points to remember
1. Basics of Control and Coordination

 Definition: Control and coordination involve systems that help organisms respond to stimuli and maintain
internal balance (homeostasis).
 Animals: Use a nervous system and endocrine system (hormones) for coordination.
 Plants: Lack a nervous system; rely on chemical coordination via plant hormones (phytohormones).

2. Coordination in Animals

 Nervous System:
o Components: Brain, spinal cord, nerves, neurons (nerve cells).
o Neuron Structure: Dendrites (receive signals), cell body, axon (transmits signals), synapse (junction
between neurons).
o Types of Nerves: Sensory (carry signals to the brain), motor (carry signals to muscles/glands), mixed.
o Reflex Action: Rapid, involuntary response to a stimulus (e.g., pulling hand away from a hot object).
Involves a reflex arc: receptor → sensory neuron → spinal cord → motor neuron → effector.
 Human Brain:
o Parts: Forebrain (thinking, memory), midbrain (relay center), hindbrain (controls involuntary actions
like heartbeat).
o Functions: Cerebrum (thinking), cerebellum (balance), medulla (involuntary actions like breathing).
 Endocrine System:
o Glands secrete hormones directly into the bloodstream to regulate functions.
o Key Glands and Hormones (as discussed earlier):
 Pituitary (GH, TSH, ACTH, FSH, LH, PRL).
  Thyroid (T4, T3).
 Adrenal (cortisol, adrenaline).
 Pancreas (insulin, glucagon—linked to blood sugar regulation, as in the diagram).
o Feedback Mechanisms: Negative feedback loops maintain balance (e.g., insulin lowers blood sugar,
and low sugar stops insulin release, as in the hypoglycemia discussion).

3. Coordination in Plants: No Nervous System: Plants use chemical coordination via hormones.

Types of Movements:

o Tropic Movements (directional, growth-related):

 Geotropism: Roots grow downward (positive), stems upward (negative).
 Phototropism: Stems grow toward light (positive), roots away (negative), driven by auxin.
 Hydrotropism: Roots grow toward water.
 Thigmotropism: Tendrils coil around supports (e.g., climbers), driven by auxin.
o Nastic Movements (non-directional, turgor pressure-related):
 Example: Mimosa leaves droop when touched due to water loss in cells.

Plant Hormones

o Auxin: Promotes growth, drives phototropism and thigmotropism.

o Gibberellins: Stem elongation, seed germination.
o Cytokinins: Cell division, delays aging.
o Abscisic Acid (ABA): Inhibits growth, stress hormone (wilting, dormancy).

4. Key Differences Between Plants and Animals

 Response Speed: Animals respond faster (nervous system); plants respond slower (chemical signals).
 Mechanism: Animals use electrical (nerves) and chemical (hormones) signals; plants use only chemical
signals (hormones).
 Movement: Animals show locomotion; plants show growth-based or turgor-based movements.

5. Important Processes

 Feedback Loops
o Example: Blood sugar regulation by insulin (pancreas). High sugar → insulin release → sugar falls →
insulin stops (negative feedback). Overcorrection can lead to hypoglycemia (low sugar).
 Hormone Interactions:
o In plants, auxin drives tropic movements by causing differential growth.
o In animals, hormones like adrenaline prepare the body for "fight or flight" (increased heart rate,
energy mobilization).

6. Diagrams to Remember

 Neuron Structure: Dendrites, cell body, axon, synapse.

 Reflex Arc: Pathway of a reflex action.
 Human Brain: Label forebrain, midbrain, hindbrain.
 Feedback Loop: Blood sugar regulation by insulin (as in the diagram provided).

7. Key Terms

 Stimulus: Any change in the environment (e.g., light, touch, gravity).

 Receptor: Senses the stimulus (e.g., skin in animals, plant cells).
 Effector: Responds to the stimulus (e.g., muscles in animals, plant cells for movement).
 Homeostasis: Maintaining internal balance (e.g., blood sugar, temperature).