Voluntary and Involuntary Actions PDF

Voluntary and involuntary actions Voluntary actions involve conscious thought (thinking time). Voluntary Actions refer to those activities or movements of any part of our body that is planned or goal-oriented. As the name suggests, these actions take place according to our choices. Some...

Voluntary and involuntary actions Voluntary actions involve conscious thought (thinking time). Voluntary Actions refer to those activities or movements of any part of our body that is planned or goal-oriented. As the name suggests, these actions take place according to our choices. Some examples of voluntary actions are – Walking Reading Singing Involuntary actions/Reflex actions do not involve conscious thought (thinking time) and happen very quickly to avoid unnecessary damage to the body. Some examples of reflex actions are – Coughing Sneezing rapidly removing your hand from a hot plate before it gets burned Change in the size of the pupil of the eye due to sudden exposure to bright light, etc Reflex arc A reflex action happens quickly because the reflex pathway is kept short and involves the smallest number of neurones and synapses possible. Reflex arc https://youtu.be/Nn2RHLWST-k Relfex arc There are 3 neurones in a reflex arc. The sensory neurone - carries information from the receptor to the spinal cord (coordinator). The relay neurone - joins the sensory neurone and motor neurone. The motor neurone - carries information from the spinal cord to an effector that can cause a response. Voluntary actions – Information is processed in the brain and the spinal cord Brain Inoluntary actions/Reflex action – Information is processed in the spinal cord Spinal cord Involuntary actions/Reflex actions Voluntary actions Immediate response to the stimuli Stimuli that involves thought process Controlled mainly by sensory neurons, motor Controlled by sensory neurons, motor neurons and spinal cord neurons, Spinal cord and brain Spinal cord coordinates the reflex action Brain is the control centre Time taken for response is relatively less Time taken for response is relatively more  TASK 1: Order the reflex arc… a) A chemical crosses the gap (synapse) between a sensory neurone and a relay neurone. b) a motor neurone. c) A muscle responds by contracting, a gland responds by releasing chemical substances. d) A stimulus is a change in the environment of an organism. e) Impulses from a receptor pass along a sensory neurone…………. f) The motor neurone carries an impulse to an effector…………….. g) Then a chemical crosses the synapse between a relay neurone and……………. h) This is detected by a receptor such as the eye. i) to the central nervous system (the co-ordinator). j) which can be a muscle or a gland………….  Check your answers… d) A stimulus is a change in the environment of an organism h) This is detected by a receptor such as the eye. e) Impulses from a receptor pass along a i) to the central nervous system (the co- sensory neurone…………. ordinator). a) A chemical crosses the gap (synapse) between a sensory neurone and a relay neurone. g) Then a chemical crosses the synapse b) a motor neurone. between a relay neurone and……………. f) The motor neurone carries an impulse to an j) which can be a muscle or a gland…………. effector…………….. c) A muscle responds by contracting, a gland responds by releasing chemical substances. TASK 2: Name the following structures in a reflex action. (i) The structure that detects the stimulus. _________ (ii) The neuron that carries impulses to the central nervous system. _________ (iii) The neurone that carries impulses away from the central nervous system. _________ (iv) The structure that brings about the response. _________ TASK 2: Answers (i) The structure that detects the stimulus. RECEPTOR (ii) The neuron that carries impulses to the central nervous system. SENSORY NEURONE (iii) The neurone that carries impulses away from the central nervous system. MOTOR NEURONE (iv) The structure that brings about the response. EFFECTOR  TASK 3 A person accidentally touches a hot pan. Her hand automatically moves away from the pan. The diagram shows the structures involved in this action. Describe fully how the structures shown in the diagram bring about this reflex action.  TASK 3 Answer A person accidentally touches a hot pan. Her hand automatically moves away from the pan. The diagram shows the structures involved in this action. Describe fully how the structures shown in the diagram bring about this reflex action. A person touches the hot pan. (STIMULUS) This stimulus is received by the pain and thermoreceptors in the skin The information is sent to the brain by the sensory neurone The information is processed by the spinal cord The processed information is sent to the muscles of the hand by the motor neurone You move away your hand immediately (RESPONSE) TASK 4 Drugs, alcohol and reflexes Read the information below and answer questions that follow. Drug is a substance that modifies or affects chemical reactions in the body. Stimulants cause more neurotransmitter molecules to diffuse across the synapses. e.g nicotine, caffeine and ecstasy. Depressant stops sending nerve impulses. To the next neuron. They bind the receptor of the next neuron that needs to respond to the neurotransmitter molecule. E.g. Alcohol is a depressant Parkinson’s disease is a genetic disease that affects the nervous system. Parkinson’s sufferers are not able to produce the naturally occurring chemical dopamine, a neurotransmitter that helps smooth and normal movements. Without this people show symptoms of slow movement, speech problems, tremors when moving, poor balance. The drug L-dopa, replaces the dopamine that is lost in people with Parkinson’s disease. Serotonin is another of the body’s naturally occurring neurotransmitters. It is normally active in the brain and can cause problems if It is not produced. Some forms of depressions are caused by reduced amounts of serotonin in the brain. Now answer these questions 1. Describe how drinking Alcohol causes reflex action of a person to slow down? They bind the receptor of the next neuron that needs to respond to the neurotransmitter molecule. Hence this interrupts the sending of messages to and from the brain. 2. Describe how lack of chemicals in the brain lead to depression. Some forms of depressions are caused by reduced amounts of serotonin in the brain. Serotonin is a neurotransmitter