Topic: Conditioned and unconditioned reflexes.

Author: Elżbieta Szedzianis

Target group

7th grade students of an eight‑year elementary school.

Core curriculum

9. Nervous system Student:

3) describes the reflex arc and enumerates types of reflexes; observes knee jerk.

Lesson aim

The students explain the mechanism behind the conditioned and unconditioned reflexes and explain their significance.

Key Success Criteria

• you will explain the mechanism behind the conditioned and unconditioned reflexes;

• you will compare the conditioned and unconditioned reflexes and present their significance;

• you will describe a reflex arc.

Key competences

• communicating in the mother tongue;

• communicating in a foreign language;

• Mathematical competence and basic competences in science and technology; 

• digital competence;

• learning to learn;

• Social and civic competences.

Methods/forms of work:

Work with model, work with text, work with film, workshop method, elements of an experiment.

Individual and group work.

Teaching measures:

• abstract;

• interactive whiteboard or traditional blackboard;

• tablets/computers;

• models of neurons;

• hats made of brown paper;

• markers.

Before the lesson

Volunteers create a model of a neuron from various materials.

Lesson plan overview (Process)

Introduction

1. The teacher asks the volunteers to present the models of neurons they created at home, name their parts and explain the direction the neural impulses travel. The students can create a gallery of models of neurons in the classroom.

2. The teacher gives the topic and the aim od the lesson and explains the criteria of success. He presents the proposed course of the class.

Realization

3. The teacher asks the students to read the fragment titled Conditioned and unconditioned reflexes” and to prepare a table that compares both types of reflexes.
   The teacher supervises the works, checks whether the sentences are correct and, if necessary, corrects the mistakes.

4. The students explain the significance of conditioned and unconditioned reflexes. They write down the explanation in their notebooks.

5. The students form groups. Their task is to create possibly the longest list of examples of conditioned and unconditioned reflexes other than the ones that are mentioned in the abstract. When the time for this exercise is up, the group representatives read out their lists. The examples are discussed and either accepted or rejected.

6. The teacher then shows them a film titled “The path of a stimulus on the reflex arc”. The students work in groups and design a model of a reflex arc created from their own bodies (e.g. using hats made of brown paper, just like during the lesson on how nervous system is built, when the students were creating a model that illustrates how information is transmitted and received by neurons).

7. Each group presents their work. After all the presentations, the students select models which represent the reflex arc the best.

8. The teacher presents the experiment described in the abstract, not telling the students what the conclusion is (“Experiment 1”). The students form a hypothesis, present probable results and explain, why groups participating in the experiment should be kept separated. They define conditioned and unconditioned reflexes and describe the reflex arc.

Summary

9. The students complete the interactive exercises.

10. The teacher asks the students to write down in their notebooks the notions they learnt during this lesson and to classify them into one of the two categories: “I know and understand” or
    “I don’t know it well enough”. Then the students plan how to learn the notions that they don’t understand well enough.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Unconditioned and conditioned reflexes

Central nervous system is created by symmetrically arranged (paired) cranial nerves and spinal nerves which are connected with the central nervous system. Cranial nerves enter the encephalon and leave it through openings in the cranium. Impulses travel through them between the encephalon and part of the head and neck (e.g. information received by the sensory organs of the head and neck, as well as instructions for those parts of the body). Spinal nerves are the nerves of the torso and the limbs. Nerves create a large and complex network which reaches receptors and executive organs: muscles and glands.

Taking into consideration the direction in which a neural impulse is conducted by the fibers of the peripheral nerves, we divide nerves into:

• sensory nerves, which conduct information from the external and the internal environment of the body into the central nervous system (e.g. optic nerve);

• motor nerves, which conduct the decisions of the central nervous system to the effectors, which are muscles or glands, e.g. nerves that cause the eyeball movement.

Nervous system allows a quick reaction to information from the environment. Usually, the reaction time is important, e.g. if a swift escape can decide whether someone lives or dies. Your body has a set of typical, automatic reactions – reflexes.

Reflexes can be divided into unconditioned and conditioned. Unconditioned reflexes (inborn reflex) are genetically programmed, cannot be changed and don’t disappear. They are performed automatically, without your will or you being conscious of them. They usually happen through spinal cord and encephalon, without the participation of the cortex, which explains the speed of the reaction. They are responsible for maintaining basic life functions and the work of internal organs; they have defensive significance for the body. An example of this can be the reflexes of sneezing, coughing, vomiting that appear as a reaction to a foreign, unnecessary substances that enter our digestive tract or respiratory system.

Conditioned reflexes are created during your entire life, they can be controlled and modified, and those that were not fully learnt become weaker or disappear, e.g. biting your nails, pressing a break when you are driving and you are approaching an obstacle, looking around before crossing the street. They take place because of our will, with the participation of the cerebral cortex. Conditioned reflexes have adaptive significance for the body.

The mechanism of how they are created was discovered by a Russian scientist, Ivan Pavlov. He investigated the reaction of saliva production while eating. Every time before he gave his dogs food, he switched on the light. After some time, the animals began to react with increase in saliva production already when they saw the light.

The requirement for the unconditioned reflex to happen is the receptor receiving an important signal for our life. This can be e.g. too high temperature of the glass we just grabbed. This type of information is carried by the sensory neurons from the skin of our hand to the spinal cord. There, it is recognized. The spinal cord sends a response with the motor neurons to the executive organs, in this case to the muscles of the hand, which quickly open the hand and move it away. The reaction time from the moment of burning your hand to the moment of dropping the glass is really short.

The path the neural impulse covers from the receptor to the effector is called reflex arch. Most of the time, it consists of 5 elements:

• receptor, composed of specialized cells (e.g. in sensory ograns) or free nerve endings (e.g. in the skin) which receive stimuli and convert them into an electrical neural impulse;

• sensory neurone, which transfers the neural impulse from the receptor to the central nervous system;

• nerve centre in the spinal cord or the encephalon, in which the impulse is processed and from where the answer to a given stimuli is sent to the body;

• motor neurone, which transfers the neural impulse to the executive organ;

• effector, that is an executive organ in form of a muscle, which contracts, or a gland, in which the secretive function begins.

In transferring information between the sensory neurons and the motor neurons, the associative neurons (interneurons) act as intermediaries. They are found in the spinal cord. The more complex the reflex is, the more intermediary neurons are there between the sensory and the motor neuron. In a simple knee jerk reaction, there are only 2 neurons: sensory and motor. In the reaction of flexing your burnt hand, there are 3 neurons that participate, including 1 cognitive one. When you step on something sharp with your bare foot, you will move the foot away and shout in pain. There are several associative neurons that participate in this reaction.

• Nerves of the central nervous system are composed of sensory and motor fibers.

• Basic function of the nervous system is reacting to impulses, called a reflex.

• During a reflex, neural impulse passes a path called a reflex arch.

• Reflex arch consists of 5 basic elements: receptor, sensory neuron, neural centre, motor neuron, effector.

• Unconditioned reflexes are involuntary and cannot be modified.

• Conditioned reflexes develop throughout your life, can be modified and can disappear when not repeated.