3.6.2Inquiry Process
The Nervous System — IB Biology HL Revision Notes & Topical Questions
5 min read 5 parts Lesson 142 of 160
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 5Divisions of the Nervous System
Central nervous system
- Central nervous system The brain and spinal cord, which receive information, integrate it and decide on a response.
Peripheral nervous system
- Peripheral nervous system All the nerves outside the CNS, carrying information from receptors and instructions to effectors.
Somatic division
- Somatic division Controls voluntary movements of skeletal muscle through motor neurones from the CNS.
Autonomic division
- Autonomic division Controls involuntary activities such as heart rate, digestion and gland secretion, without conscious control.
Sensory and motor nerves
- Sensory and motor nerves Nerves are bundles of axons,
- and sensory nerves bring information in while motor nerves carry commands out to muscles and glands.
| Autonomic branch | Typical effect on heart rate | Situation |
|---|---|---|
| Sympathetic | Increases | Stress or exercise |
| Parasympathetic | Decreases | Rest and digestion |
Part 2 of 5Regions of the Brain
Regions of the Brain
Cerebral cortex
- Cerebral cortex Processes sensory input, controls voluntary actions, and carries out thinking, language and memory.
Cerebellum
- Cerebellum Coordinates balance and fine movements by comparing intended and actual positions of the body.
Medulla oblongata
- Medulla oblongata Controls automatic functions such as breathing rate, heart rate and the diameter of blood vessels.
Hypothalamus
- Hypothalamus Monitors body temperature, water balance and hunger, and links to the pituitary gland.
Pituitary gland
- Pituitary gland Releases hormones, some of which control other endocrine glands, in response to signals from the hypothalamus.
Part 3 of 5Information Flow
1
Receptors convert stimuli into nerve impulses, which are carried by sensory neurones towards the CNS.
2
The CNS integrates inputs from many receptors and compares them with stored information.
3
The brain or spinal cord sends impulses along motor neurones to effectors.
4
Autonomic motor pathways adjust internal organs, while somatic pathways move skeletal muscle.
5
The spinal cord links the brain to the body and also acts as the centre for simple reflexes that do not need the brain.
Part 4 of 5Worked Example
Question
- A person stands up quickly and feels briefly dizzy before blood pressure is restored.
- Identify the part of the brain and the autonomic branch most involved in restoring blood pressure, and state the effect on the heart.
- Blood pressure is controlled by the medulla oblongata, which receives input from pressure receptors.
- To raise pressure it activates the sympathetic branch of the autonomic nervous system.
- The sympathetic nerves increase heart rate and constrict blood vessels.
Answer The medulla oblongata, acting through sympathetic nerves, speeds the heart and raises blood pressure.
Part 5 of 5Exam Checklist & Tips
3.6.2 – Key Points for the Exam
- CNS The brain and spinal cord.
- Autonomic nervous system Division controlling involuntary activities such as heart rate.
- Cerebellum Brain region for coordination of movement and balance.
- Medulla oblongata Brain region that controls breathing and heart rate.
Common Mistakes
- Calling the autonomic system voluntary; it works without conscious control.
- Placing breathing control in the cerebellum rather than the medulla.
- Confusing the pituitary (a gland) with the hypothalamus (brain tissue).
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