The Nervous SystemAQA GCSE Biology: Flashcards
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What are the two main divisions of the nervous system?
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- What are the two main divisions of the nervous system?
- The central nervous system (CNS), which consists of the brain and spinal cord, and the peripheral nervous system (PNS), which consists of neurones that connect the CNS to the rest of the body.
- Define a sensory neurone and state its function.
- A sensory neurone is a nerve cell that carries electrical impulses from sense organs (receptors) to the central nervous system. Its function is to transmit sensory information from receptors to the CNS.
- Define a motor neurone and state its function.
- A motor neurone is a nerve cell that carries electrical impulses from the central nervous system to effectors (muscles or glands). Its function is to transmit signals that cause a response.
- What is the role of a relay neurone in the nervous system?
- A relay neurone connects sensory neurones to motor neurones. It is found in the CNS and transmits impulses between sensory and motor neurones, allowing the CNS to process information and coordinate responses.
- Explain the pathway of a reflex arc in the correct sequence.
- Receptor → Sensory neurone → Relay neurone (in spinal cord) → Motor neurone → Effector (muscle or gland). This pathway allows a rapid, automatic response without involving the brain.
- What is the key difference between a reflex action and a voluntary response?
- A reflex action is an automatic, rapid response that does not involve the conscious brain; it occurs via a reflex arc. A voluntary response is a conscious action controlled by the brain and involves deliberate decision-making.
- Define a synapse.
- A synapse is the junction between two neurones, consisting of a presynaptic membrane (on the transmitting neurone), a synaptic cleft (small gap), and a postsynaptic membrane (on the receiving neurone).
- Explain how nerve impulses are transmitted across a synapse using neurotransmitters.
- An electrical impulse arrives at the presynaptic neurone, causing vesicles containing neurotransmitter molecules to fuse with the presynaptic membrane. Neurotransmitters are released into the synaptic cleft, diffuse across it, and bind to receptors on the postsynaptic membrane, generating a new electrical impulse in the receiving neurone.
- What is the role of the brain in coordinating voluntary responses?
- The brain receives sensory information from the peripheral nervous system, processes this information, and sends motor impulses via motor neurones to effectors to produce a conscious, voluntary response. The brain controls all deliberate actions.
- Why is studying the brain difficult? Name two reasons.
- The brain is complex with billions of neurones and trillions of connections, making it difficult to study all functions. It is also enclosed in the skull, limiting direct access, and ethical considerations restrict experimental research on humans.
- What is MRI scanning and how is it used to study brain function?
- MRI (Magnetic Resonance Imaging) is a non-invasive scanning technique that uses magnetic fields and radio waves to produce detailed images of the brain. It allows researchers to observe which areas of the brain are active during specific tasks or in response to stimuli, without using radiation.
- Describe the effects of brain damage on human function.
- Brain damage can result in loss of specific functions depending on the area affected. For example, damage to the motor cortex can cause loss of voluntary muscle control; damage to the visual cortex can cause blindness; damage to areas controlling speech can cause aphasia. Effects depend on the location and severity of damage.
- What is an effector in the context of the nervous system?
- An effector is a muscle or gland that responds to a motor neurone impulse by producing an effect. Muscles contract to produce movement, and glands secrete hormones or other substances.
- Name the three types of neurone and describe their relative lengths.
- Sensory neurone (long dendrite, short axon), relay neurone (short, found in CNS), motor neurone (short dendrite, long axon). The long axon of a sensory or motor neurone allows impulses to travel long distances between receptors/CNS and CNS/effectors.
- Why is the reflex arc an advantage for survival?
- The reflex arc allows a rapid automatic response without conscious thought or delay caused by processing in the brain. This is advantageous for survival in dangerous situations, such as quickly withdrawing from a hot object before the brain has time to process pain.