Human Nervous System

Functions of the Nervous System

• The nervous system oversees the functions of all bodily organs, receives and integrates information from all senses, initiates and coordinates motor activities, and processes thoughts, generates emotions, and stores memories.

Divisions of the Nervous System

• Anatomically, the nervous system consists of two major components: the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).
• The CNS is composed of the brain and spinal cord, and its major functions are to integrate sensory information and to initiate and coordinate efferent responses.
• The PNS is composed of all the nervous tissue outside the CNS, including cranial nerves, spinal nerves, and ganglia.

Functional Divisions of the Nervous System

• The nervous system can be functionally divided into the somatic nervous system, which controls voluntary functions, and the autonomic nervous system, which controls involuntary activities.

Cerebral Cortex

• The cerebrum consists of two cerebral hemispheres, the right and left hemispheres, connected by the corpus callosum.
• Each hemisphere is mainly connected to the contralateral side of the body.
• The hemispheres are further divided into four lobes: occipital, parietal, temporal, and frontal.

Functions of the Lobes

• Frontal lobe: associated with parts of speech, reasoning, problem-solving, planning, movement, and emotions.
• Parietal lobe: associated with recognition, orientation, and perception of stimuli.
• Occipital lobe: responsible for visual processing.
• Temporal lobe: associated with memory, speech perception, and recognition of auditory stimuli.

Grey and White Matter

• Grey matter is composed of cell bodies of neurons, dendrites, and supporting glial cells.
• The microscopic structure of grey matter varies between different brain regions.
• The majority of cerebral cortex is made up of six distinct layers of neurons.
• In the brain, the grey matter is outside, and the white matter is inside, whereas in the spinal cord, the grey matter is deep inside and covered all around by white matter.
• White matter is composed of bundles of myelinated axons (tracts).

Brainstem

• The midbrain, pons, and medulla oblongata form the brainstem, which contains the vital cardio-respiratory centers.
• The midbrain connects the forebrain and the hindbrain, and acts as a bridge, transmitting signals from the hindbrain and forebrain.
• The midbrain is associated with motor control, vision, hearing, temperature regulation, and alertness.

Meninges

• The meninges consist of three layers, with the outermost layer being the dura mater, also known as the pachymeninx.