3.5.2Additional lessons
The Nervous System — IB Biology SL Revision Notes & Topical Questions
5 min read 5 parts Lesson 66 of 142
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Part 1 of 5Organisation of the Nervous System
Central nervous system
- Central nervous system The brain and spinal cord form the CNS, which receives and processes all incoming information and coordinates responses.
Peripheral nervous system
- Peripheral nervous system All the nerves outside the CNS carry impulses from receptors into the CNS and from the CNS out to effectors.
Sensory neurone
- Sensory neurone It carries impulses from a receptor towards the CNS.
Motor neurone
- Motor neurone It carries impulses from the CNS to an effector, which is a muscle or a gland.
Relay neurone
- Relay neurone It lies entirely inside the CNS and links sensory neurones to motor neurones.
Part 2 of 5The Brain as an Integration Organ
The Brain as an Integration Organ
Cerebrum
- Cerebrum The large cerebral hemispheres handle conscious thought, memory, language, voluntary movement and sensory perception.
Cerebellum
- Cerebellum This region at the back coordinates muscle movement, posture and balance.
Medulla oblongata
- Medulla oblongata This brainstem region controls unconscious activities such as heart rate and breathing rate.
Hypothalamus
- Hypothalamus It monitors blood and links the nervous system to the endocrine system through the pituitary gland.
Pituitary gland
- Pituitary gland It lies below the hypothalamus and releases hormones that regulate other endocrine glands.
Part 3 of 5The Spinal Cord
Pathway
- Pathway It carries impulses between the brain and the rest of the body through ascending and descending tracts.
White matter
- White matter This outer tissue contains myelinated axons that carry information up and down the cord.
Grey matter
- Grey matter This inner tissue contains cell bodies and synapses where relay neurones process incoming signals.
Reflex centre
- Reflex centre Many rapid reflexes are processed in the spinal cord alone without waiting for the brain.
Part 4 of 5From Stimulus to Response
1
A receptor detects a stimulus and converts that energy into an electrical signal in a sensory neurone.
2
In a taste bud, chemicals in food bind to receptor proteins on chemoreceptor cells, which depolarises the cell membrane.
3
Sufficient depolarisation produces action potentials in the sensory neurone, and its axon carries them to the CNS.
4
The CNS integrates the information, and some of it reaches the cerebral hemispheres where it becomes conscious perception.
5
Motor neurones carry a command to effectors, which then produce the response.
Part 5 of 5Exam Checklist & Tips
3.5.2 – Key Points for the Exam
- Central nervous system The brain and spinal cord.
- Receptor A cell or structure that detects a stimulus and converts it into an electrical signal.
- Effector A muscle or gland that carries out a response.
- Cerebellum The brain region that coordinates movement and balance.
- Medulla oblongata The brainstem region controlling heart and breathing rates.
Common Mistakes
- Mixing up sensory and motor neuronessensory goes to the CNS, motor goes away from it.
- Saying the spinal cord is only a cable; it also processes information in reflex pathways.
- Writing that all brain activity is conscious; the medulla controls heart rate without thought.
- Calling a receptor an effector; receptors detect, effectors respond.
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