COORDINATION AND RESPONSE
Coordination:
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Refers to the processes that help control and regulate the activities of an
organism.
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In animals, coordination is achieved through:
✧The nervous system: Uses electrical signals to transmit information rapidly
between body parts.
✧Hormones: Chemical messengers released by glands into the bloodstream to
regulate slow but long-lasting changes like growth, metabolism, and
reproduction.
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In plants, coordination involves:
✧
Hormones: Chemicals like auxins and gibberellins that regulate processes
like growth, flowering, and response to light and gravity.
✧
Signaling mechanisms: Plants lack a nervous system, but they respond to
stimuli such as light, water, and touch through chemical signals.
Response:
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The actions or behaviors that organisms perform in reaction to a stimulus.
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Immediate responses:
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●
✧
Reflex actions in animals, like pulling a hand away from a hot object.
✧
Plants bending toward light (phototropism).
Delayed responses:
✧
Hormonal changes in response to long-term stimuli (e.g., puberty in
humans).
✧
Seasonal leaf shedding in trees due to changing light conditions.
Stimuli:
✧
Any detectable change in the environment that can trigger a response in
an organism.
✧
External stimuli:
✔Temperature, light, sound, touch, and chemicals in the environment.
✧
Internal stimuli:
✔Changes in the body such as hunger, thirst, or changes in blood sugar
levels.
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Importance of Coordination and Response:
✧
Survival:
✔Enables organisms to find food (e.g., animals detect food sources
through smell or sight).
✔Helps avoid danger (e.g., prey animals detect predators and flee).
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Homeostasis: Maintains a stable internal environment, allowing organisms to
survive in changing external conditions.
✧
For example, sweating helps cool the body during hot conditions to
regulate body temperature.
Sense organ
Eye
Ear
Nose
Tongue
Skin
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Responsible for
sight
hearing
smell
taste
touch
Stimulus it responds to
light
sound
chemicals
chemicals
touch, pain, temperature, pressure
The parts of the body which respond to stimuli are called effectors.
✧
For example, muscles and glands.
✔ Muscles respond to stimuli by contracting or relaxing
✔Glands respond to stimuli by secreting chemicals and hormones.
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The receptor cells of each sense organ are connected to the brain by nerves called
neurons.
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Messages from receptors to effectors are sent in the form of electrical impulses.
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When receptors sense stimuli, the stimuli is converted into nerve impulses and
sent along the nerves to the brain or spinal cord.
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The brain the sends a message to the right effector to respond to the message
received.
Stimulus
Receptor
Coordinator
Effector
Response
Nervous System:
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A complex network of nerves and cells that transmit signals between different
parts of the body.
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Responsible for coordination, communication, and response to stimuli.
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Divided into two main parts:
✧ Central Nervous System (CNS).
✧ Peripheral Nervous System (PNS).
Central Nervous System (CNS)
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CNS:
✧ Consists of the **brain** and **spinal cord**.
✧ Controls most functions of the body and mind, acting as the command
center.
✧ Brain: Processes information and controls voluntary and involuntary
actions.
●
Divided into areas such as the cerebrum (thinking, memory), cerebellum
(movement), and brainstem (involuntary actions like breathing).
✧ Spinal cord: Transmits messages between the brain and the rest of the
body, also involved in reflex actions.
Axon
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Axon:
✧ A long, thin fiber extending from a neuron (nerve cell) that transmits
electrical signals away from the cell body.
✧ Often covered by a **myelin sheath** which helps speed up the
transmission of signals.
✧ Transmits signals to other neurons, muscles, or glands.
Dendrites
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Dendrites:
✧ Short, branch-like extensions from the cell body of a neuron.
✧ Responsible for receiving signals from other neurons and transmitting
them to the neuron's cell body.
Sensory Neurons
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- Sensory Neurons:
✧ Specialized nerve cells that carry signals from sensory receptors (such as
the skin, eyes, ears) to the CNS.
✧ They detect external stimuli like light, heat, pressure, or chemical changes
and send this information to the brain or spinal cord for interpretation.
Motor Neurons
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- **Motor Neurons**:
✧ Nerve cells that transmit signals from the CNS to muscles or glands to
cause a response.
✧ They enable actions like muscle movement, reflexes, and glandular
secretion.
Sensory Neuron
Sensory Functions of the human Tongue, Eye, Ear and Skin
The Tongue
●
Taste Buds:
✧ The tongue contains taste buds, which are sensory receptors responsible
for detecting different tastes.
✧ Located mainly on the papillae (small bumps) on the surface of the
tongue.
●
Types of Taste:
✧ Taste buds can detect four basic tastes:
✔ Sweet: Indicates energy-rich foods.
✔ Salty: Helps maintain electrolyte balance.
✔ Sour: Detects acidity, often signaling spoiled or unripe food.
✔ Bitter: Helps identify potentially harmful or toxic substances.
●
-Taste Receptors**:
✧ The receptors in taste buds respond to chemicals in food dissolved in
saliva.
✧ These receptors send signals to the brain, which interprets the taste.
The Eye
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The eye detects light
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The retina of the eye contains two sorts of receptors which are sensitive to light.
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Nerve fibers connect the receptors to the brain
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All the nerve fibers leave the eyes at one point and form the optic nerve which
extends at the back of the eye to the brain.
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When light falls on the receptor cells in the retina, they are stimulated by the light.
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They produce sensory nerve impulses of the image which are sent via the optic
nerve to the brain.
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The brain sorts out all the impulses from each receptor cell and builds up an
image.
The Ear
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The ear detects sound
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Sound waves pass through the outer ear, middle ear, to the inner ear.
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In the inner ear is a coiled-tube like structure called the cochlea and for the
auditory nerve.
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Inside the cochlea there are nerve fibers
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The nerve fibers come together outside the cochlea and form the auditory nerve.
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The receptor cells convert the vibrations into sensory nerve impulses and send
along the auditory nerve to the brain.
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The brain interprets the impulses as sound.
The Skin
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The skin has several sorts of nerve endings in the dermis.
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The nerve endings are receptors of touch, heat, cold, pressure or pain.
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When they are stimulated by stimuli, the stimuli are converted to sensory nerve
impulses and sent to the brain.
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The brain interprets the impulses as touch, heat, cold, pressure or pain.
Voluntary and Reflex Actions
Reflex Action
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Definition:
✧ A reflex action or reflex is an involuntary, automatic response to a
stimulus.
✧ It occurs spontaneously without involving conscious thought.
●
Examples:
✧ Adjusting our eyes in response to bright light.
✧ Withdrawing a hand from a hot object.
Involvement of the Nervous System:
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Peripheral Nervous System (PNS):
✧ Connects the Central Nervous System (CNS) (brain and spinal cord) to the
rest of the body.
✧ Consists of nerves that relay information between the CNS and other
body parts.
●
Central Nervous System (CNS):
✧ Reflex actions are coordinated by the spinal cord.
✧ The brain is not involved in reflex actions, making them faster responses.
Voluntary Action
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Definition:
✧ Actions that are produced with the involvement of thought and conscious
decision-making.
✧ These actions are performed intentionally, with awareness.
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Examples:
✧ Walking, eating, jumping, running, writing, etc.
Involvement of the Nervous System:
●
Central Nervous System (CNS):
✧ Both the brain and spinal cord are involved in voluntary actions.
✧ The brain:
✔ Makes decisions and initiates voluntary action.
✔ Sends signals through the spinal cord to the muscles.
✧ The spinal cord:
✔ Transmits signals between the brain and the body, helping
coordinate the movement.
●
Peripheral Nervous System (PNS):
✧ Connects the CNS to the muscles and organs to execute the voluntary
actions.
✧ Relays signals from the CNS to the muscles that carry out the movement.
Reaction Time
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Definition:
✧ The time taken to respond to a stimulus.
✧ It is the interval between the detection of a stimulus and the initiation of
a response.
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Factors Influencing Reaction Time:
✧ Complexity of the stimulus: More complex stimuli take longer to process.
✧ Age: Reaction time tends to slow down with age.
✧ Alertness and focus: Being tired or distracted can increase reaction time.
✧ Practice: Regular practice can improve reaction time.
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Example:
✧ Catching a ball after it’s thrown or braking a car when a light turns red.
Drugs And Drug Abuse
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A drug is any externally administered substance which modifies or affects
chemical reactions in the body.
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A medicine is a chemical treatment for an illness.
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All medicines contain drugs, but not all drugs are medicines
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For example, alcohol is a drug but not a medicine.
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Medicinal drugs play an important role in providing good health, e.g, painkillers.
Drug Abuse
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The taking of a drug not for the intended purpose.
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Examples of drugs usually abused include alcohol, cannabis, cocaine and heroin.
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Abusing such drugs may lead to addiction.
Effects Alcohol
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Impairs judgment and decision-making abilities
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Causes slurred speech and difficulty in talking
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Leads to drowsiness or fatigue
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Can result in nausea and vomiting
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May damage the liver, leading to serious health issues
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Increases the risk of certain types of cancer
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Can cause heart-related problems
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May lead to mental health issues, such as depression
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Can create problems in relationships with friends and family
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Can result in legal issues, such as arrests for driving under the influence (DUI)
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Can negatively affect performance at school or work
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Causes anxiety and irritability when not drinking (withdrawal symptoms)
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Can lead to shaking (tremors)
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Can cause excessive sweating
Effects of Cannabis
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Alters perception of time and space
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Impairs short-term memory and attention
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Causes relaxation and euphoria (feeling high)
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Increases appetite (often called "the munchies")
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May cause dry mouth and bloodshot eyes
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Can lead to anxiety or paranoia, especially in high doses
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Impairs motor skills and coordination
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May affect heart rate and blood pressure
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Can cause drowsiness or fatigue
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May lead to respiratory issues (if smoked)
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Long-term use can affect mental health and lead to dependence
Effects of Cocaine
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Increases energy and alertness
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Causes intense euphoria (feeling very high)
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Heightens confidence and sociability
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Reduces appetite
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Can lead to increased heart rate and blood pressure
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Causes dilated pupils
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May result in anxiety or paranoia
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Impairs judgment and decision-making
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Causes nasal irritation (if snorted) or damage to the respiratory system (if
smoked)
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Can lead to addiction and withdrawal symptoms (fatigue, depression, cravings)
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Long-term use can result in severe health problems, including heart attack or
stroke
Heroin
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Heroin relieves severe pain and it produces a feeling of well-being.
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Users administer heroin by sniffing or injection.
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There are dangers of abusing heroin because:
✧ It slows down brain activity
✧ It causes drowsiness and sleepiness
✧ It depresses appetite so there is no desire for food, causing
malnourishment.
Personal and Social Problems of Drug Abuse
Personal Problems of Drug Abuse
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Health Issues: Physical health problems (e.g., heart disease, liver damage) and
mental health disorders (e.g., depression, anxiety).
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Addiction: Dependence on drugs, leading to withdrawal symptoms and cravings.
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Financial Problems: Spending excessive money on drugs, leading to debt and
financial instability.
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Legal Issues: Arrests or legal troubles related to drug possession or use.
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Relationship Problems: Strained relationships with family, friends, and partners
due to behavior changes or neglect.
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Poor Performance: Decline in academic or work performance, leading to job loss
or academic failure.
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Isolation: Withdrawal from social activities and support networks.
Social Problems of Drug Abuse
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Crime and Violence: Increased risk of engaging in criminal activities or violence
related to drug use or trafficking.
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Family Strain: Increased stress and conflict within families, potentially leading to
domestic violence or child neglect.
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Impact on Community: Higher rates of drug-related crime and safety concerns in
communities.
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Stigma: Negative perceptions and discrimination against individuals struggling
with drug abuse, making it harder for them to seek help.
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Burden on Healthcare: Increased demand for medical and psychological services
due to drug-related health issues.