Reflex, Voluntary Actions And Conditional Reflexes

CONTENT

• Reflex and voluntary actions
• The reflex arc
• Differences between reflex and voluntary actions
• Conditioned reflexes
• Differences between hormonal and nervous coordination

REFLEX AND VOLUNTARY ACTIONS

Actions are responses to stimuli. These actions are grouped into two: involuntary (reflex) and voluntary actions.

REFLEX ACTIONS

Reflex actions are automatic responses to stimuli which do not involve the conscious or higher centre of the brain.   These actions are mainly protective, guarding us from dangerous stimuli and helping us to maintain posture and balance.  Reflex actions include jerking of the legs, blinking of the eyes etc.

THE REFLEX ARC

The reflex arc involves the following:

1. the sensory receptors that receive the stimulus.
   1. the sensory neurones along which the sensory impulse travels
   1. the relay or intermediate neurone through which the sensory impulse is passed on.
   1. the motor (efferent) neurones along which the response is transmitted.
   1. the effectors (muscles and glands) which the motor impulses trigger to bring about an appropriate response.

Reflex actions can be:

1. Spinal reflex involving the spinal cord e.g knee jerk
   1. Cranial reflex involving the brain e.g closing of pupil in the presence of bright light.

EVALUATION

1. Describe the pathway of a simple reflex arc.
2. What are reflex actions? Give five examples

VOLUNTARY ACTIONS

These are actions initiated and controlled by the conscious part of the brain, which involve thoughts before performance. They involve:

1. the conscious parts of the cerebrum
2. most of the reflex arc components
3. ascending and descending fibres in the spinal cord.

Examples of voluntary actions are playing football, solving mathematical problems, walking, driving etc.

DIFFERENCES BETWEEN REFLEX AND VOLUNTARY ACTIONS

REFLEX ACTION	VOLUNTARY ACTION
1. Actions does not involve higher centre of the brain (unconscious)	Actions involves higher centre of the brain (conscious)
2. Involves smaller number of neurones.	Involves numerous neurones.
3. Response is rapid	Response is slow
4. Response is stereotyped	Response varies with circumstances.
5, It is inborn	It can be learnt

CONDITIONED REFLEXES

A reflex action may be instinctive (does not have to be learned) e. g. sucking behaviour of newly born baby or conditioned reflex (learned responses or behaviour that can be performed without thinking about it) e. g. walking, riding a bicycle, writing e. t. c. A famous Russian biologist, Ivan Pavlon demonstrates what is meant by conditioned reflex using a puppy and associating its food time with the sound of a bell.

ROLES OF CONDITIONED REFLEX ON BEHAVIOUR

1. It helps us to acquire new skills by learning such habits.
2. It helps to modify many simple reflex actions because of conditions associated with them.
3. It helps us to behave in highly complicated manner (movements become faster and automatic.

EVALUATION

1. Differentiate between conditioned and instinctive reflex actions
2. What are voluntary actions? Give five examples

DIFFERENCES BETWEEN HORMONAL AND NERVOUS COORDINATION

NERVOUS COORDINATION	HORMONAL COORDINATION
1. Messages are transmitted as electrical impulses.	Messages are transmitted as chemical impulses.
2. Transmission is via nerve fibres.	Transmission is via blood stream.
3. Transmission is very fast	Transmission is slow.
4. Response is fast, shot-lived and precise.	Response is slow, long-lasting and widespread.
5. It is mainly controlled by the brain and the spinal cord.	It is controlled by the pituitary gland.
6. Effectors (muscles and glands) receive the message.	Target organs receive the message.

GENERAL EVALUATION

1. What do you understand by a) voluntary action b) reflex action
2. Give five examples each of a) voluntary actions  b) reflex actions
3. Differentiate between voluntary and reflex actions
4. Give five examples conditioned reflexes
5. What are the roles of conditional reflexes on behaviour

READING ASSIGNMENT

College Biology, chapter 10, page 217 – 221

WEEKEND ASSIGNMENT

1. Automatic responses to stimuli which do not involve higher centre of the brain are referred to as ———- actions a) voluntary b) reflex c) muscular d) nervous
2. Behavioural patterns acquired only through learning are referred to as a) reflex action b) conditioned reflex c) voluntary action d) learning
3. Which of these is not a conditioned reflex a) walking b) typing c) driving d) sneezing
4. Transmission in hormonal coordination is through a) blood stream b) nerve fibre c) lymph d) neurone
5. Which arrangement shows the correct pathway of impulse transmission
6.  Axon —– cell body —– dendrites —– synaptic knob
7. Dendrites —– synaptic knob —– cell body —– axon
8. Dendrites —– cell body —- axon —- synaptic knob
9. Cell body —- dendrites —– synaptic knob —- axon

THEORY

1. Describe what happens when you accidentally picked up a hot object

Differentiate between instinctive and conditioned reflexes.