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nervous system and receptor involve, role, speed and glands
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Voluntary and Involuntary Actions
• Two types of action controlled by the human nervous system are:
(a)voluntary action
(b)involuntary action
• The peripheral nerves transmit both voluntary and involuntary actions.
Voluntary action
Nature of the control of action
• Involves thought
and free will
• Allows us to consciously
control our skeletal
muscles
Voluntary action is controlled by:
• Cerebrum (fore-brain) which:
(a)coordinates incoming information and then initiates impulses which are sent to the effectors.
(b)may spontaneously initiates actions without any sensory stimulation.
Receptors involved:
• An action may be initiates by the stimulation of a receptor,or by the conscious will of the brain itself
Inborned or learned actions• Voluntary actions are learned
Role of voluntary action:
• To respond with the benefit of experience
Parts of the nervous system involved:
• Reflex arc structures • Interneurons(ascending and descending
fibres )in the spinal cord • Always involved the cerebrum
Speed of action:
• Slow response,as the
cerebrum needs time
to “think”before an
action is carried out.
• Eg. ) if we want to ask
question, we raise our
hands.
Response to the same stimulus:
• The same stimulus may produce various responses.
• Eg.) when you are hungry,you may decide to eat or not to eat, or just need to drink water.
Involuntary action
Nature of the control of action
• Does not involve thought
• Not under the control of the will
• Cannot control the activities
• examples; pumping of the heart and peristalsis
Controlled by:
• Spinal cord(spinal reflex action)
• Hind-brain(cranial reflex action) example blinking of the eyes
Parts of the nervous system involved:
• Reflex arc:afferent neurones(from receptors)to intermediate neurones in spinal cord and out through efferent neurones (to effectors)
• Hind-brain(in cranial reflex action)
Receptors involved:
• A receptor is always involved
Inborned or learned actions
• Reflex actions are inborn (already “hard-wired”at birth
Role of involuntary action:
• To respond quickly to avoid danger
Speed of action:
• Rapid response,as the cerebrum is not involved
Response to the same stimulus:
• The same stimulus always results in the same response(stereotyped response),example as in the knee jerk
Examples of involuntary action:
• Involuntary action(reflex action)involving skeletal muscle:
(a)knee jerk
• Involuntary action involving:
(a)smooth muscles
(b)cardiac muscles
(c)glands,example,normal blood pressure
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