(todo 2.10B-12B,15B-17B) Nervous Control - Paper 1 Flashcards
What are sensory receptors?
Sensory receptors are groups of cells that detect stimuli and initiate responses to them. Different receptors detect different stimuli.
What are effectors?
Effectors are muscles or glands which respond to nervous impulses and bring about a response to a stimulus. Muscles contract and glands secrete hormones.
What is the Central Nervous System (CNS)?
In vertebrates, the CNS consists only of the brain and spinal cord. All the information from sensory receptors is sent here, and actions and reflexes are coordinated.
What is the function of a sensory neurone?
To carry electrical impulses from sensory receptors to the CNS.
What is the function of a relay neurone?
To carry electrical impulses from sensory neurones to motor neurones within the CNS.
What is the function of a motor neurone?
To carry electrical impulses from the CNS to effectors.
What are synapses and how is information transmitted across them?
Synapses are connections between neurones. When an electrical impulse reaches an axon terminal, it stimulates the release of neurotransmitters. These diffuse across the air gap and set off a new impulse in the next neurone’s dendrite.
Describe the basic structure of a neurone.
All neurones have a cell body (similar to a normal animal cell) with extensions - with many endings - to connect to other neurones. Dendrons (ending with dendrites) carry impulses towards the cell body, and axons (ending with axon terminals) away. Some axons are myelinated, with a myelin sheath - a layer that acts as an electrical insulator, speeding up the electrical impulse.
Why are longer neurones faster than many connected neurones?
Information crosses synapses slower than it travels through neurones. Neurotransmitter diffusion is slow compared to transmission of an electrical impulse.
What is the structure of a sensory neurone?
Sensory neurones have a long dendron and a short axon.
What is the structure of a relay neurone?
Relay neurones have no dendron, but many short dendrites connected to the cell body. They also have a short axon.
What is the structure of a motor neurone?
Motor neurones have no dendron, but many short dendrites connected to the cell body. They also have a long axon.
What is the structure of a reflex arc?
Reflex arcs consist of a sensory receptor, sensory neurone, relay neurone, motor neurone and effector. No impulse travels to the brain.
What is the function of a reflex arc?
To perform reflexes - fast and automatic actions that do not require conscious thought (ie consultation of the brain). Reflexes often protect us from injury.
