Control and Coordination Notes

Control and Coordination

Introduction

Living organisms perform maintenance functions.
Movement is often associated with life.
Some movements result from growth (e.g., plants).
Some movements are not connected to growth (e.g., animals running).
Movement is often a response to environmental change.
Living organisms use changes in their environment to their advantage.
Controlled movement is linked to recognizing environmental events and responding appropriately.
Living organisms use systems providing control and coordination.
Multicellular organisms use specialized tissues for control and coordination.

Animals – Nervous System

Control and coordination in animals are provided by nervous and muscular tissues.
Detecting and responding to a hot object is an urgent situation.
Information from the environment is detected by specialized nerve cell tips (receptors).
Receptors are located in sense organs (inner ear, nose, tongue, etc.).
Gustatory receptors detect taste; olfactory receptors detect smell.
Information acquired at the dendritic tip of a nerve cell triggers a chemical reaction that creates an electrical impulse.
The impulse travels from the dendrite to the cell body and then along the axon to its end.
At the axon's end, the electrical impulse releases chemicals.
These chemicals cross the synapse and initiate a similar electrical impulse in the next neuron's dendrite.
Nervous tissue is composed of a network of neurons, specialized for conducting information via electrical impulses.

Neuron Structure

Information is acquired at the dendrites.
Information travels as an electrical impulse through the axon.
The impulse is converted into a chemical signal at the axon terminal for onward transmission across the synapse.

Reflex Actions

Reflex actions are sudden responses to environmental stimuli without conscious thought.
Examples: jumping away from a bus, pulling hand from flame, mouth watering when hungry.
In urgent situations (e.g., touching a flame), a quick response is needed.
Thinking about the pain and potential burn would take too long.
Nerve impulses and neuron interactions facilitate thinking.
Thinking tissue consists of dense networks of neurons in the forward end of the skull.
The brain receives signals from the body and instructs muscles to move via nerves.
To solve the problem of slow reaction time, the body uses a reflex arc.
Reflex arc: a direct connection between sensory and motor nerves.
Reflex arcs are formed in the spinal cord, where nerves from all over the body meet.
Information also reaches the brain, but the reflex response is quicker.
Reflex arcs evolved as efficient ways of functioning in the absence of complex thought processes.
Even with complex neuron networks, reflex arcs are more efficient for quick responses.

Reflex Arc

The process involves quick responses to stimuli without involving the brain directly.

Human Brain

The spinal cord also relays information to the brain for thinking.
Thinking involves more complex mechanisms and neural connections in the brain.
The brain is the main coordinating center of the body.
The brain and spinal cord form the central nervous system.
The central nervous system receives and integrates information from all body parts.
Voluntary actions (writing, talking, moving) are based on decisions made by the brain.
The brain sends messages to muscles to initiate action.
Communication between the central nervous system and the body is facilitated by the peripheral nervous system (cranial and spinal nerves).
The brain has different parts responsible for integrating different inputs and outputs.
The brain has three major regions: fore-brain, mid-brain, and hind-brain.

Fore-brain

The main thinking part of the brain.
Receives sensory impulses from various receptors.
Specialized areas for hearing, smell, sight, etc.
Association areas interpret sensory information and integrate it with stored information.
Decisions are made about how to respond, and information is passed to motor areas.
Motor areas control voluntary muscles (e.g., leg muscles).
The sensation of feeling full is associated with a center in the fore-brain.

Mid-brain and Hind-brain

Control involuntary actions (e.g., heart beat).
Involuntary actions: muscle movements without thinking control.
Examples: blood pressure, salivation, vomiting.
Controlled by the medulla in the hind-brain.

Cerebellum

Part of the hind-brain.
Responsible for precision of voluntary actions and maintaining posture and balance.
Enables activities like walking in a straight line, riding a bicycle, picking up a pencil.

Protection of Nervous Tissue

The brain is protected by the bony box of the skull.
The brain is contained in a fluid-filled balloon for shock absorption.
The spinal cord is protected by the vertebral column (backbone).

Nervous Tissue and Action

Nervous tissue collects, sends, processes information, makes decisions, and conveys decisions to muscles for action.
Muscle tissue performs the final action or movement.

Muscle Movement

When a nerve impulse reaches the muscle, the muscle fiber moves.
Muscle cells move by changing their shape to shorten.
Muscle cells contain special proteins that change shape and arrangement in response to nervous electrical impulses.
New arrangements of these proteins give the muscle cells a shorter form.
Voluntary and involuntary muscles differ in their control mechanisms.

Coordination in Plants

Plants lack a nervous system and muscles.
Plants respond to stimuli in different ways.

Examples of Plant Response

Touching the leaves of a sensitive plant causes them to fold up and droop.
A seed germinates, the root goes down, and the stem comes up.

Types of Plant Movement

Movement independent of growth (e.g., sensitive plant).
Movement dependent on growth (e.g., seedling).

Immediate Response to Stimulus

In sensitive plants, movement occurs at a point different from the point of touch.
Information about the touch is communicated.
Plants use electrical-chemical means to convey information from cell to cell.
Plants lack specialized tissue for conduction of information.
Cells change shape by altering the amount of water in them, causing swelling or shrinking.

Movement Due to Growth

Plants like pea plants use tendrils to climb.
Tendrils are sensitive to touch.
The part of the tendril in contact with support grows slower, causing the tendril to circle around the object.
Plants respond to stimuli slowly by growing in a particular direction (tropic movements).

Tropic Movements

Directional movements towards or away from a stimulus.
Environmental triggers: light, gravity.
Phototropism: shoots bend towards light, roots bend away.
Geotropism: roots grow downwards, shoots grow upwards, in response to gravity.
Hydrotropism: growth in response to water.
Chemotropism: growth in response to chemicals.
Example: growth of pollen tubes towards ovules.

Information Communication in Multicellular Organisms

The movement of sensitive plants is quick, while sunflowers' response to day/night is slow.
Growth-related movements are even slower.
Controlled movements can be slow or fast.
Fast responses require rapid information transfer.
Electrical impulses are an excellent means for rapid transfer but have limitations.

Limitations of Electrical Impulses

Reach only cells connected by nervous tissue.
Cells need time to reset before transmitting another impulse.
Multicellular organisms use chemical communication.

Chemical Communication

Stimulated cells release a chemical compound (hormone).
The compound diffuses around the original cell.
Other cells detect the compound using special molecules on their surfaces.
Slower than electrical impulses but can reach all cells and can be sustained.
Plant hormones coordinate growth, development, and responses to the environment.
Hormones are synthesized at places away from where they act and diffuse to the area of action.

Auxin

A hormone synthesized at the shoot tip.
Helps cells grow longer.
In phototropism, auxin diffuses towards the shady side, stimulating cells to grow longer on that side.

Gibberellins

Plant hormones that help in stem growth.

Cytokinins

Promote cell division.
Present in greater concentration in areas of rapid cell division (fruits and seeds).

Abscisic Acid

A hormone that inhibits growth.
Causes wilting of leaves.

Hormones in Animals

Hormones are used for chemical information transmission in animals.

Adrenaline

In scary situations, animals (e.g., squirrels) prepare for fighting or running away.
These activities require a great deal of energy and integrated tissue activity.
If the body relied only on electrical impulses, the range of tissues instructed would be limited.
A chemical signal (hormone) can reach all cells and provide wide-ranging changes.
Adrenaline is secreted from the adrenal glands directly into the blood.

Effects of Adrenaline

Heart beats faster, supplying more oxygen to muscles.
Blood to digestive system and skin is reduced, diverting blood to skeletal muscles.
Breathing rate increases.
Responses enable the animal to deal with the situation.
Animal hormones are part of the endocrine system.

Endocrine System

Constitutes a second way of control and coordination in the body.

Other Animal Hormones

Hormones control directional growth.
Growth happens in carefully controlled places.
The body's design is maintained during growth.

Thyroxin

Iodine is necessary for the thyroid gland to make thyroxin.
Thyroxin regulates carbohydrate, protein, and fat metabolism for growth.
Iodine deficiency can lead to goitre, characterized by a swollen neck.

Growth Hormone

Secreted by the pituitary gland.
Regulates growth and development of the body.
Deficiency in childhood leads to dwarfism.

Testosterone and Oestrogen

Changes associated with puberty are due to the secretion of testosterone in males and oestrogen in females.

Insulin

Produced by the pancreas.
Helps in regulating blood sugar levels.
Insufficient secretion leads to diabetes, causing elevated blood sugar levels.
Treated with insulin injections.

Hormone Regulation

The timing and amount of hormone released are regulated by feedback mechanisms.
Example: high blood sugar levels stimulate the pancreas to produce more insulin, which lowers blood sugar.
As blood sugar decreases insulin secretion declines.