Control and Coordination Notes

Control and Coordination

Introduction

• Living organisms perform maintenance functions, and movement is often associated with life.
• Movements can be due to growth (plants) or independent of growth (animals).
• Movement is often a response to environmental changes, aimed at using these changes advantageously.
• Controlled movement is linked to the recognition of environmental events and appropriate responses.
• Living organisms use control and coordination systems involving specialized tissues.

Animals – Nervous System

• Nervous and muscular tissues provide control and coordination in animals.
• Detecting and responding to stimuli (e.g., touching a hot object) is crucial.
• Specialized nerve cell tips (receptors) detect environmental information, located in sense organs.
• Gustatory receptors detect taste, while olfactory receptors detect smell.
• Information acquisition at the dendritic tip of a neuron triggers a chemical reaction, creating an electrical impulse.
• The impulse travels from the dendrite to the cell body and along the axon.
• At the axon end, the electrical impulse releases chemicals that cross the synapse, initiating a similar impulse in the next neuron's dendrite.
• This process allows nerve impulses to travel throughout the body.
• Synapses facilitate impulse delivery from neurons to other cells like muscle or gland cells.
• Nervous tissue consists of a network of neurons specialized for conducting information via electrical impulses.

Neuron Structure

• Dendrites: Acquire information.
• Axon: Transmits information as an electrical impulse.
• Synapse: Converts the electrical impulse into a chemical signal for transmission to the next neuron or target cell.

Reflex Actions

• Reflex actions are sudden, involuntary responses to environmental stimuli.
• They occur without conscious thought or control.
• Touching a flame exemplifies an urgent situation requiring a quick response.
• Thinking about the pain and potential burns before reacting takes too long.
• Nerve impulses and complex interactions of neurons are involved in thinking.
• The thinking tissue, located in the forward end of the skull, receives and processes signals from the body.
• The brain instructs muscles to move via nerve signals.
• To expedite responses, the body employs reflex arcs.
• Reflex arcs involve a direct connection between sensory and motor nerves, bypassing the brain for immediate action.
• This connection occurs in the spinal cord, where nerves from the body converge on their way to the brain.

Reflex Arc

• A reflex arc is a neural pathway that controls a reflex action.
• It includes a sensory receptor, sensory neuron, interneuron (in the spinal cord), motor neuron, and effector (muscle or gland).
• Reflex arcs evolved as efficient mechanisms for quick responses, especially in animals with limited cognitive processing.
• Even with complex neuron networks, reflex arcs remain more efficient for rapid reactions.

Human Brain

• The spinal cord transmits information for thinking, but the brain is the primary coordinating center.
• The brain and spinal cord form the central nervous system (CNS).
• The CNS integrates information from the body, enabling thought and voluntary actions.
• The brain sends messages to muscles to initiate actions like writing or moving.
• The peripheral nervous system (cranial and spinal nerves) facilitates communication between the CNS and the body.
• The brain's complex design integrates inputs and outputs through different regions: forebrain, midbrain, and hindbrain.

Brain Regions

• Forebrain: Main thinking part, receives sensory impulses, and has specialized areas for hearing, smell, and sight.
  • Association areas interpret sensory information and integrate it with stored knowledge.
  • Decisions are made, and information is sent to motor areas for voluntary muscle control.
  • A center associated with hunger provides the sensation of feeling full.
• Midbrain and Hindbrain: Control involuntary actions like heartbeats and breathing.
  • The medulla in the hindbrain controls blood pressure, salivation, and vomiting.
  • The cerebellum in the hindbrain is responsible for the precision of voluntary actions, posture, and balance.

Protection of Nervous Tissue

• The brain requires careful protection due to its importance.
• The skull provides a bony enclosure for the brain.
• The brain is contained in a fluid-filled balloon within the skull for shock absorption.
• The vertebral column (backbone) protects the spinal cord.

How Nervous Tissue Causes Action

• Nervous tissue collects, processes, and sends information to muscles for action.
• Muscle tissue executes the final movement.

Muscle Movement

• Muscle cells change shape to shorten and produce movement.
• Muscle cells contain special proteins that change their shape and arrangement in response to nervous electrical impulses.
• This rearrangement shortens the muscle cells.
• Voluntary and involuntary muscles differ based on the level of conscious control.

Coordination in Plants

• Plants lack a nervous system and muscles.
• They respond to stimuli through different mechanisms.
• The leaves of the sensitive plant fold up and droop upon touch.
• Seedling roots grow downwards, while stems grow upwards.
• Plant movements can be growth-dependent or growth-independent.

Immediate Response to Stimulus

• The sensitive plant's leaves move quickly in response to touch without growth.
• The plant transmits information about the touch from cell to cell using electrical-chemical means.
• Unlike animals, plants lack specialized tissue for information conduction.
• Plant cells change shape by altering their water content, leading to swelling or shrinking.

Movement Due to Growth

• Some plants, like pea plants, use tendrils to climb.
• Tendrils are sensitive to touch; the part in contact with support grows slower, causing the tendril to circle and cling.
• Plants respond to stimuli slowly by growing in a specific direction (tropism).

Tropism

• Phototropism: Shoots bend towards light, while roots bend away.
• Geotropism: Roots grow downwards, and shoots grow upwards in response to gravity.
• Hydrotropism: Growth in response to water.
• Chemotropism: Growth in response to chemicals (e.g., pollen tube growth towards ovules).

Information Communication in Multicellular Organisms

• The sensitive plant's movement is quick, while sunflower movement is slow.
• Growth-related movements are even slower.
• Controlled movements can be slow or fast.
• Fast responses require rapid information transfer.
• Electrical impulses are a fast means of transmission but limited to cells connected by nervous tissue.
• Cells require time to reset before transmitting new impulses.
• Multicellular organisms use chemical communication (hormones) for broader and more sustained responses.

Chemical Communication

• Stimulated cells release chemical compounds (hormones) that diffuse to surrounding cells.
• Target cells detect these compounds using surface molecules, recognizing and transmitting information.
• This process is slower but can reach all cells, regardless of nervous connections.
• Plant hormones coordinate growth, development, and responses to the environment.
• Auxin, synthesized at the shoot tip, promotes cell elongation and causes the plant to bend towards light.
• Gibberellins promote stem growth.
• Cytokinins promote cell division and are found in areas of rapid cell division like fruits and seeds.
• Abscisic acid inhibits growth and causes wilting of leaves.

Hormones in Animals

• Hormones are used for chemical information transmission in animals.
• In stressful situations, animals prepare for fight or flight.
• Hormones facilitate widespread changes in the body.

Adrenaline

• Adrenaline, secreted by the adrenal glands, prepares the body for action.
• It increases heart rate, supplying more oxygen to muscles.
• Blood flow to the digestive system and skin decreases, diverting blood to skeletal muscles.
• Breathing rate increases due to diaphragm and rib muscle contractions.

Endocrine System

• Hormones are part of the endocrine system, which provides a second way of control and coordination.
• Animal hormones, unlike plant hormones, do not control directional growth but regulate growth in carefully controlled places.

Role of Hormones in Coordinated Growth

• Iodine is essential for the thyroid gland to produce thyroxin, which regulates carbohydrate, protein, and fat metabolism.
• Iodine deficiency can lead to goitre, characterized by a swollen neck.
• Growth hormone, secreted by the pituitary gland, regulates growth and development.
• Deficiency in childhood leads to dwarfism.
• Testosterone (males) and oestrogen (females) cause changes associated with puberty.
• Insulin, produced by the pancreas, regulates blood sugar levels.
• Insufficient insulin secretion leads to diabetes, causing high blood sugar levels.

Feedback Mechanisms

• Precise hormone quantities are maintained through feedback mechanisms.
• For example, high blood sugar levels stimulate insulin production, while low levels reduce insulin secretion.

Summary

• Endocrine glands secrete hormones that perform specific functions.
• Hormones regulate various bodily functions through feedback mechanisms.

Important Hormones and Their Functions: