Nervous System Organization

Study Notes

The Nervous System controls the functions of the body. It is divided into two main parts: the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).
The CNS is composed of the brain and spinal cord, which are responsible for processing and integrating information.
The PNS consists of all neural tissue outside the CNS, including cranial nerves, spinal nerves, and sensory receptors. It is responsible for transmitting information to and from the CNS.
The PNS is further divided into two divisions: the Afferent Division, which carries sensory information to the CNS, and the Efferent Division which carries motor commands from the CNS to the body.
The Efferent Division is further split into the Somatic Nervous System which controls voluntary movements, and the Autonomic Nervous System which controls involuntary functions like heart rate, digestion, and breathing.
The Autonomic Nervous System itself is divided into the Sympathetic Nervous System, which prepares the body for action, and the Parasympathetic Nervous System, which promotes rest and relaxation.

The brain is the control center of the nervous system, responsible for thought, emotion, behavior, and sensory processing. It is protected by the skull and meninges.
The spinal cord extends downwards from the brain, passing through the vertebral column. It serves as a pathway for messages to and from the brain, and is also capable of reflex actions.

The brain consists of four main parts: Cerebrum, Diencephalon, Cerebellum, and Brainstem.

The largest part of the brain, responsible for higher cognitive functions like reasoning, thought, memory, language, voluntary movement, sensory perception, and many more.
It is divided into two hemispheres connected by the corpus callosum.
The surface of the cerebrum is covered in folds called gyri and grooves called sulci, which increase the surface area.

Located above the brainstem, it is composed of the thalamus, hypothalamus, and epithalamus.
The thalamus acts as a relay center for sensory information to the cerebrum.
The hypothalamus controls vital functions like temperature, hunger, thirst, sleep, and hormone release.
The epithalamus is involved in the regulation of sleep-wake cycles.

Located at the back of the brain, it is responsible for coordinating movement, balance, posture, and muscle tone.

Responsible for certain visual and auditory reflexes, and also relays information to other parts of the brain.

Involved in relaying messages between the cerebrum and other parts of the brain, as well as controlling certain reflexes like chewing and saliva production.

The lowest part of the brainstem, responsible for controlling vital functions like heart rate, breathing, swallowing, coughing, and blood pressure.

Dura Mater: Thick, outermost layer.
Arachnoid Mater: Delicate, middle layer.
Pia Mater: Innermost layer with blood vessels supplying nutrients to the nervous tissue.

Four hollow spaces located within the brain, connected to each other and filled with cerebrospinal fluid.

Produced by the choroid plexus in the lateral ventricles, it circulates through the ventricular system and around the brain and spinal cord.
Provides cushioning for the CNS, transports nutrients and removes waste products.

Consists of all nerves outside the brain and spinal cord, connecting the CNS to the rest of the body.
It includes 12 pairs of cranial nerves and 31 pairs of spinal nerves.

Carry signals to and from the head and neck region.
Some are responsible for special senses, such as sight, hearing, taste, and smell.
Others carry sensory information from the face, head, and neck, and motor commands to muscles in these regions.

Responsible for carrying sensory information from the body to the spinal cord, and motor commands from the spinal cord to the body.
They are named for the region from which they arise (e.g., cervical, thoracic, lumbar, sacral, coccygeal).

Controls involuntary bodily functions, such as heart rate, digestion, and gland secretions.
Divided into two branches:

Sympathetic Nervous System: Activates the body's "fight-or-flight" response, preparing the body for action.
Parasympathetic Nervous System: Promotes rest and relaxation, conserving energy.