The human nervous systemOxford AQA IGCSE Biology: Flashcards

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Name the three main parts of the nervous system.

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Name the three main parts of the nervous system.: The brain, spinal cord, and peripheral nerves.
What is the function of a sensory neurone?: To carry nerve impulses from receptors to the central nervous system (brain and spinal cord).
Define a relay neurone and state where it is found.: A neurone that carries nerve impulses between sensory and motor neurones. It is found in the central nervous system.
What is the function of a motor neurone?: To carry nerve impulses from the central nervous system to effectors (muscles or glands).
Describe the complete reflex arc pathway.: Stimulus → receptor → sensory neurone → relay neurone → motor neurone → effector → response.
Why are reflex actions important?: They allow rapid responses to stimuli without conscious thought, protecting the body from harm (e.g., withdrawing from pain). The response is faster than voluntary responses.
Define a synapse.: A junction between two neurones where nerve impulses are transmitted from one neurone to another.
Explain how nerve impulses are transmitted across a synapse using neurotransmitters.: The nerve impulse causes vesicles containing neurotransmitter molecules to fuse with the presynaptic membrane. Neurotransmitters are released into the synaptic cleft and bind to receptors on the postsynaptic membrane, triggering a new nerve impulse in the next neurone.
Name the four main regions of the brain and state one function of each.: Cerebral cortex: conscious thought, memory, intelligence. Cerebellum: coordination and balance. Medulla: controls heart rate, breathing, and blood pressure. Hypothalamus: temperature regulation and hormone control.
List the structures of the eye involved in focusing light onto the retina.: Cornea, iris, lens, and retina. The cornea and lens refract light, the iris controls pupil size, and the retina detects light.
What is the function of rod and cone cells in the retina?: Rod cells detect light and dark (black and white vision) and are sensitive in dim light. Cone cells detect colour and provide detailed vision in bright light.
Explain how the eye focuses on objects at different distances using accommodation.: For near objects: the ciliary muscles contract, reducing tension on the suspensory ligaments, so the lens becomes thicker and more curved, increasing its power. For distant objects: the ciliary muscles relax, increasing tension on the suspensory ligaments, so the lens becomes thinner and flatter, decreasing its power.
What is short-sightedness and how is it corrected?: Short-sightedness (myopia) is when distant objects appear blurred because the image forms in front of the retina. It is corrected using a concave lens to diverge light rays before they enter the eye.
What is long-sightedness and how is it corrected?: Long-sightedness (hyperopia) is when near objects appear blurred because the image forms behind the retina. It is corrected using a convex lens to converge light rays before they enter the eye.
Name the structure that transmits nerve impulses from the eye to the brain.: The optic nerve carries electrical impulses from the retina to the brain.