Introduction to Coordination and Control

Coordination and control in biology refers to the working together of various agents in a body to produce appropriate reactions to stimuli. This process involves two main systems:

1. The nervous system
2. The endocrine system

The nervous system is further divided into:

• Central Nervous System (CNS): Comprising the brain and spinal cord
• Peripheral Nervous System (PNS): Consisting of nerve cells that carry information to and from the CNS

Definition: Reaction time is the length of time taken for a person or system to respond to a stimulus or event.

Factors affecting reaction time include:

• Age
• Gender
• Physical fitness
• Type of stimulus (auditory or visual)

Highlight: The average reaction time is approximately 215 milliseconds.

Mechanism of Receptors

Receptors are specialized cells that detect changes in the environment and produce electrical impulses in response to stimuli. They are crucial components of the coordination and control in biology.

The main types of receptors and their corresponding stimuli are:

1. Skin: Touch and heat
2. Tongue: Chemicals (food and drink)
3. Nose: Chemicals (in air)
4. Eye: Light
5. Ear: Sound

Example: When heat (stimulus) is detected by a receptor, it triggers a response through the following pathway:

Heat → Receptor → Sensory neuron → Relay neuron → Motor neuron → Effector (muscle) → Response

This pathway is known as a reflex arc, which allows the body to respond automatically and rapidly to a stimulus, minimizing potential damage.

Definition: A reflex arc is a way for the body to automatically and rapidly respond to a stimulus to minimize any further damage to the body.

Actions can be classified as:

1. Voluntary: Actions you have control over
2. Involuntary: Actions you cannot control

Types of Neurons

In the study of coordination and control in biology, understanding the types of neurons in nervous system is essential. There are three main types of neurons, each with distinct characteristics and functions:

1. Sensory Neurons

   • Convert stimuli into electrical impulses
   • Have long dendrites and short axons
   • Cell body is bulging out of the neuron

2. Motor Neurons

   • Transfer messages from the central nervous system to effector organs
   • Have short dendrites and long axons
   • Neurotransmitters are released at the end of the axon

3. Relay Neurons

   • Link sensory and motor neurons, allowing uninterrupted impulse movement
   • Present in the brain and spinal cord
   • Do not have a myelin sheath

Vocabulary: Myelin sheath - A fatty layer that covers and insulates the axon of some neurons, increasing the speed of electrical impulse transmission.

Highlight: The structure of neurons is specialized to their function, with variations in the length of dendrites and axons, as well as the presence or absence of myelin sheaths.