Central Nervous System (CNS)

What are the two main components of the Central Nervous System (CNS)?

The brain and spinal cord.

What is the primary function of the cerebrum?

• Largest part of the brain, 2–4 mm thick.

• Responsible for thinking, reasoning, learning, memory, and intelligence.

• Controls voluntary muscle movement and perception of senses.

• Divided into two hemispheres by the longitudinal fissure.

• Surface has convolutions (gyri) separated by sulci (shallow grooves) and fissures (deep grooves).

• Contains inner grey matter called the basal ganglia, involved in movement control.

• Grey matter lacks myelin, which normally speeds up nerve impulses.

what is the cerebral cortex

• The outer layer of the cerebrum.

• Made of grey matter (unmyelinated neurons).

• Responsible for processing sensory input, thinking, decision-making, and voluntary movement.

• Highly folded to increase surface area.

What is the cerebellum and what does it do and how

• Second largest part of the brain, located at the back.

• Surface has parallel ridges made of grey matter.

• Inside is white matter, branching throughout the cerebellum.

• Controls posture, balance, and coordination of fine movements (e.g., writing, playing instruments).

• Prevents movements from being jerky or uncontrolled.

• Receives sensory input from the inner ear and muscle stretch receptors.

• Integrates sensory info to fine-tune and smooth out motor activity.

what is it and What autonomic functions does the medulla oblongata regulate?

A vital structure that regulates autonomic functions such as breathing, heart rate, and blood pressure. It acts as a communication pathway between the brain and spinal cord.

What are the three layers of the meninges?

Dura mater: The tough, outermost layer that provides strength and protection; it is firmly attached to the skull and loosely envelops the vertebrae.

arachnoid mater: The middle layer, characterized by its web-like appearance, encapsulates the sub-arachnoid space that is filled with cerebrospinal fluid (CSF) to absorb shocks.

pia mater: The delicate innermost layer that intimately follows the contours of the brain and spinal cord while harboring blood vessels that supply nutrients and oxygen.

What is the function of cerebrospinal fluid (CSF)?

• Provides support to the CNS, acting as a cushion to protect against sudden impacts.

• Serves as a shock absorber for the brain and spinal cord, thus preventing mechanical injuries.

• Facilitates the transportation of nutrients to and waste products away from the brain's cells, playing a key role in maintaining homeostasis.

• CSF circulates within the sub-arachnoid space surrounding the brain, the central canal of the spinal cord, and the brain's ventricles, contributing to nutrient delivery and waste disposal.

What are the five cerebral lobes and their primary functions?

• Frontal Lobe

  • Front of brain; handles decision-making, planning, emotions.

  • Contains primary motor cortex for voluntary movement.

• Parietal Lobe

  • Behind frontal lobe; processes touch, temperature, and pain.

  • Contains somatosensory cortex for interpreting body sensations.

• Temporal Lobe

  • Below lateral fissure; involved in hearing, memory, and emotion.

  • Includes hippocampus (memory) and amygdala (emotion).

• Occipital Lobe

  • Back of brain; responsible for vision.

  • Contains visual cortex for processing shapes, colour, and motion.

• Insula Lobe

  • Deep inside lateral sulcus; senses internal states (e.g. hunger, pain), processes emotion, empathy, taste, and helps regulate body balance.

What is the basal ganglia's role in movement control?

consists of groups of nerve cell bodies associated with control of skeletal muscles. Role – initiating wanted movements and inhibiting unwanted movements.

How does the spinal cord function in relation to the brain?

• Conducts sensory impulses towards the brain and motor impulses away from the brain. These impulses travel along ascending (sensory) and descending (motor) tracts.

• Integrates reflex actions for rapid responses, enabling immediate reactions to stimuli, often bypassing conscious brain processing..

structure of spinal cord

Approximately 44 cm long; encased in protective meninges within the vertebral canal, consisting of cervical, thoracic, lumbar, sacral, and coccygeal regions.

What is the primary function of the hypothalamus?

• Regulates homeostasis: temperature, hunger, thirst, sleep-wake patterns, and urinary bladder contraction.

• Controls vital functions: heart rate, blood pressure, digestion, pupil size.

• Manages emotional responses: fear, anger, aggression, pleasure.

• Monitors hormone secretion, coordinates the endocrine system, and regulates metabolism and growth.

• Coordinates the body's stress response through the pituitary gland.

What is the composition of cerebrospinal fluid?

A clear, colourless liquid composed of water, glucose, proteins, urea, electrolytes, and a few white blood cells. Its unique chemical composition helps maintain ionic balance critical for neuron function.

What differentiates the left hemisphere from the right hemisphere of the cerebrum?

The left hemisphere is dominant for language and analytical thinking, while the right hemisphere is for artistic abilities and spatial understanding.

What is the main difference in structure between the brain's white matter and grey matter?

White matter contains myelinated axons, while grey matter contains unmyelinated cell bodies. Myelinated cell bodies refers to cell bodies encased in a myelin sheath, a lipid protein, insulating layer that increases the speed of nerve impulse transmission. 

How does the spinal cord contribute to reflex actions?

The spinal cord facilitates reflex actions by quickly transmitting signals from sensory neurons to motor neurons without involving the brain. When a stimulus is detected, sensory neurons send the signal to the spinal cord, where interneurons process it and send a rapid response to the muscles, causing an immediate action.

What is the function of the basal ganglia in detail?

It consists of groups of nerve cell bodies that control skeletal muscle movements.

why does the spinal cord have grey matter inside, and white matter on the outside?

The grey matter is located inside the spinal cord because it contains neuron cell bodies, dendrites, and synapses, which are responsible for processing sensory input and coordinating motor output. Its central position allows for efficient processing and quick reflex responses. The white matter, made of myelinated axons, is positioned on the outside to enable faster transmission of electrical signals over long distances between the brain and spinal cord. By having white matter on the outside, these fast communication pathways are positioned closer to the external environment, ensuring rapid and efficient signal flow.

Spinal cord protective layers

The spinal cord is protected by the meninges, three layers of connective tissue that surround it. The outermost layer, the dura mater, isn't attached directly to the bone, leaving a space filled with connective tissue and blood vessels. This space helps cushion the spinal cord, allowing it to bend when the spine moves. The spinal cord itself is composed of grey matter at its center, surrounded by white matter made up of myelinated fibers. This structure, combined with cerebrospinal fluid (CSF), provides further protection by cushioning the spinal cord, preventing damage during movement or trauma.

functional areas of cerebral cortex

• Sensory Areas: Responsible for processing sensory information, including touch, temperature, and pain from the body. They interpret impulses from receptors.

• Motor Areas: Control voluntary muscle movements. The basal ganglia, a group of nuclei within the brain, are involved in movement regulation, ensuring smooth and coordinated motions. They consist of groups of nerve cell bodies.

• Association Areas: Integrate information from various sensory modalities and are crucial for functions such as memory, language, and emotion processing.