7. Structural organisation of the nervous system 7.1. The central nervous system (CNS)

Role of the brain

The brain acts as the central control and processing centre of the Central Nervous System, coordinating sensory perception, emotional responses, voluntary movement, and homeostatic regulation.

How many anatomical divisions does the brain have?

The brain is organised into four primary anatomical divisions, working together with specialised functional networks such as the limbic system.

What is the left and right side of the brain hemisphere divided into?

The largest part of the brain is divided into left and right cerebral hemispheres by the deep longitudinal fissure.

How does the left and right hemisphere communicate?

The two hemispheres communicate across a dense C-shaped band of nerve fibres called the corpus callosum.

Role of the cerebral cortex

The outer convoluted layer (the cerebral cortex) governs conscious thought, speech, memory, voluntary movement, sensory interpretation, and reasoning.

Role of the diencephalon

Functioning as the chief neuroendocrine and sensory bridge

Location of the diencephalon

Located centrally beneath the cerebrum

What does the diencephalon consist of?

1. Thalamus

2. Hypothalamus

Thalamus

The primary sensory and motor relay station, filtering and directing incoming impulses to the appropriate regions of the cerebral cortex.

Hypothalamus

The master homeostatic regulator; links the nervous system to the endocrine system via the pituitary gland and synthesises vital reproductive and labour-driving hormones, including oxytocin.

What is the limbic system ("The Emotional Brain") ?

A primitive, interconnected functional ring of structures (including the amygdala and hippocampus) bordering the diencephalon and inner cerebrum.

Role of the limbic system (The Emotional Brain)

It governs fundamental survival instincts, emotions (fear, safety, affection), memory formation, and behavioural drives. Because it directly influences hypothalamic activity, emotional state has a powerful, direct effect on autonomic and neuroendocrine outputs.

Cerebellum location

Tucked beneath the posterior cerebrum

Role of the cerebellum

Coordinates smooth voluntary motor activity, muscle tone, equilibrium, balance, and spatial posture.

Role of the Brainstem (Midbrain, Pons, Medulla Oblongata)

It houses vital autonomic reflex centres that involuntarily regulate heart rate, blood pressure (vasomotor control), respiratory rhythms, and protective reflexes such as coughing and swallowing.

How does the role of the hypothalamus link to midwifery practice?

The hypothalamus orchestrates the release of endogenous oxytocin and endorphins.

How does the role of the limbic system link to midwifery practice?

The limbic system evaluates safety and emotional security.

What happens when a labouring woman feels safe, unobserved, and relaxed?

Neocortical disturbance decreases, enabling the primitive brain to release optimal oxytocin surges.

What do bright lights, intrusive questioning, or perceived fear trigger?

It triggers the amygdala and sympathetic pathway, driving adrenaline production which can inhibit oxytocin release and disrupt effective uterine contractions.