The Nervous System & Reflexes
The human nervous system enables the body to detect changes in its surroundings (stimuli) and coordinate rapid responses. Electrical impulses travel along sensory, relay, and motor neurones through the central nervous system (brain and spinal cord), while chemical neurotransmitters carry signals across synapses.
- Stimulus
- A change in the environment that is detected by a receptor.
- Receptor
- Cells that detect stimuli.
- Sensory neurone
- Carries electrical impulses from receptors to the CNS.
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Heart (Double Circulatory Pump)
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Pumps blood in a double circulatory system: the right ventricle pumps deoxygenated blood to the lungs, and the thick muscular left ventricle pumps oxygenated blood at high pressure around the whole body.
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Key Concepts & Exam Definitions (6)
- Stimulus
- A change in the environment that is detected by a receptor.
- Receptor
- Cells that detect stimuli.
- Sensory neurone
- Carries electrical impulses from receptors to the CNS.
- Relay neurone
- Found in the CNS, connecting sensory and motor neurones.
- Motor neurone
- Carries electrical impulses from the CNS to effectors.
- Effector
- A muscle or gland that brings about a response to a stimulus.
Quick-Fire Flashcards (5)
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What is the role of the central nervous system?
What is the pathway of a reflex arc?
How do signals cross a synapse?
Why are reflex actions important?
Give an example of an effector.
Exam-Style Questions & Mark Schemes (3)
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- Q1
Describe how information passes across a synapse.
Click “Check Mark Scheme” to compare your answer, When an electrical impulse reaches the end of a neurone, it causes the release of chemicals (neurotransmitters) into the synapse. These diffuse across the gap and bind to receptors on the next neurone, triggering a new electrical impulse.
- Q2
Explain the difference between a conscious action and a reflex action.
Click “Check Mark Scheme” to compare your answer, Conscious actions involve the brain making a decision, so they are slower. Reflex actions bypass the conscious part of the brain and go through the spinal cord or an unconscious part of the brain, making them much faster and automatic.
- Q3
Identify the receptor and effector when you touch a hot object and pull your hand away.
Click “Check Mark Scheme” to compare your answer, Receptor: Temperature/pain receptors in the skin. Effector: Muscles in the arm.
Common Exam Questions (3)
What makes up the Central Nervous System (CNS)?
The Central Nervous System (CNS) consists of the brain and the spinal cord. It receives electrical impulses from sensory neurones and coordinates responses sent out along motor neurones to effectors.
What is a reflex action?
A reflex action is a rapid, automatic nervous response to a stimulus that bypasses the conscious regions of the brain via a reflex arc, protecting the body from harm (such as pulling a hand away from a hot object).
What is a synapse?
A synapse is the microscopic junction between two neurones. When an electrical impulse reaches the end of the first neurone, it triggers the release of chemical neurotransmitters that diffuse across the gap and bind to receptors on the next neurone.
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