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The Nervous System
Motor neurons, sensory neurons and the brain
| Question | Answer |
|---|---|
| What is the function of the nervous system? | The nervous system is in charge of the co-ordination and control of our body. It controls our responses to any stimulus. |
| What is a stimulus? | A stimulus is any change in our environement |
| What are the 2 main parts of the nervous system? | 1: The central nervous system which contains the brain and the spinal chord. 2: The peripheral nervous system consists of neurons. |
| What are the 3 types of neurons in the peripheral nervous system? | 1: Sensory neurons which carry impulses from the sense organs to the brain. 2: Motor neurons which carry impulses from the brain to our muscles and glands (effectors). 3: Interneurons which are found in the CNS and connect motor and sensory neurons. |
| What are the main differences between the structures of motor nerves and sensory nerves? | Motor nerves have their cell body at the beginning of the neuron, sensory nerves have theirs in the middle. In motor nerves the axon brings the impulse away from the cell body, in sensory nerves the axon brings the impulse to the cell body. |
| What is the function of the myelin sheath and the Schwann cell? | The myelin sheath insulates the axon, speeding up the impulse. The myelin sheath is secreted by the Schwann cell. |
| What happens when 2 neurons come close to each other? | Synapses are found at the end of an axon. A synapse is a region where 2 neurons come into close contact with each other. |
| What are the name of the chemicals that send the impulse from one neuron to the other? Give 2 examples of these chemicals. | These chemicals are called neurotransmitters. Examples include acetylcholine and dopamine. |
| Why is the there a small pause before another impulse can be sent across a synapse? | The neurotransmitters must be broken down by enzymes before another impulse can be sent. This is known as the refractory period. |
| List the functions of synapses. | Synapses transmit impulses from one neuron to the another. They act as valves allowing impulses to flow in one direction only. They prevent overstimulation of an effector as neurotransmitters cannot be produced constantly. |
| What is the "all or nothing rule" for impulses? | For an impulse to be sent there is a minimum threshold that must be met before an impulse can be carried. Once this threshold is reached the impulse is sent all along the axon. Sending an impulse requires energy which is gotten from ATP. |
| How is the Central Nervous System protected? | The brain is protected by the cranium. Under the cranium is 3 fluid filled membranes called the meninges. These are filled with cerebrospinal fluid which acts as a shock absorber to cushion blows to the head. |
| What is the function of the cerebrum? | The cerebrum controls the conscious part of our body. Each part of the body is linked to a different part of the cerebrum. The cerebrum also controls thinking, language, emotions, judgement and personality. |
| What is the function of the cerebellum? | The cerebellum controls activity that we have learned to do and then do automatically like walking, talking and breathing. The cerebellum has massive folds to vastly increase surface area. |
| What is the function of the medulla oblongata? | The medulla oblongata controls actions that are not under our conscious control like heartbeat, breathing and blood pressure. It also controls reflex actions like coughing, sneezing and yawning. |
| What is the function of the hypothalamus? | The hypothalamus controls our organs and endocrine system. It is often described as the link between the body and the mind. It controls hunger, thirst and water regulation. |
| How is the spinal chord protected? | The spinal chord is protected by the vertebrae and cerebrospinal fluid. |
| Describe the appearance of the spinal chord? | The spinal chord is made up of an outer layer of white matter made up of axons and an inner core of grey matter made up of cell bodies and dendrons. |
| In what direction do the impulses flow into and out of the spinal chord? | The dorsal root carries sensory neurons in and the ventral root carries motor neurons out. |
| What is a reflex action? | A reflex action is an automatic, involuntary response to a stimulus that does not go directly the brain. The impulse enters the sensory nerve and takes a short cut through an interneuron and quickly exits through a motor neuron to the effector. |
| Give an example of a neurological disorder. What are the symptoms of the disorder? How is it caused? | Parkinson’s disease is caused by a lack of production of the neurotransmitter dopamine. This results in trembling in the hands and legs. As the condition worsens the body becomes stiff and rigid resulting in an shuffling gait. |
| How is Parkinsons disease treated? | There is no way to prevent Parkinson’s disease. It can be treated by physiotherapy to relieve trembling. Drugs like L-dopa can also be taken. This is then converted to dopamine in the body. This does not stop the degeneration in the brain however. |
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cbsbiology
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