Organization of the Nervous System Quiz

Organization of the Nervous System

• The nervous system is divided into the central nervous system (CNS) and the peripheral nervous system (PNS).
• The CNS comprises the brain and spinal cord.
• The PNS consists of nerve fibers connecting the CNS to the rest of the body.

Central Nervous System

• The CNS is responsible for integrating information from the body and coordinating activities.
• The human brain contains approximately 100 billion neurons and 1000 billion glial cells.
• The brain utilizes roughly 20% of the body's total energy.
• The brain requires a constant supply of oxygen and glucose for proper function.
• Brain damage occurs if there's no oxygen supply for 4-5 minutes or no glucose supply for 10 minutes.

The Brain

• The brain is divided into four primary lobes: temporal, parietal, occipital, and frontal.
• Temporal lobe: Processes sensory input and assigns emotional meaning.
• Occipital lobe: Handles visual processing.
• Parietal lobe: Integrates sensory information like touch, spatial awareness, and navigation.
• Frontal lobe: Involved in attention, reward, short-term memory, motivation, and planning.

Spinal Cord

• The spinal cord runs along the back, transmitting information between the brain and the body.
• Thirty-one pairs of spinal nerves connect to the spinal cord.
• It links with nerves of the PNS that extend from the skin, muscles, and joints.
• Motor commands from the brain travel through the spinal cord to the body.

Peripheral Nervous System

• The PNS contains 12 pairs of cranial nerves and 31 pairs of spinal nerves.
• The PNS is further divided into the afferent (sensory) division and efferent (motor) division.
• The afferent division carries information to the CNS.
• The efferent division carries information from the CNS to muscles.

Somatic and Autonomic Nervous Systems

• The efferent division is further divided into the somatic and autonomic nervous systems.
• The somatic nervous system controls voluntary movements, such as skeletal muscle actions.
• The autonomic nervous system (ANS) controls involuntary actions, such as heart rate, digestion, and breathing.

Autonomic Nervous System

• The ANS regulates cardiac muscle, smooth muscle, and glands.
• The ANS is further divided into the sympathetic and parasympathetic nervous systems.
• The sympathetic nervous system prepares the body for stress or action.
• The parasympathetic nervous system conserves energy and promotes relaxation.

Enteric Nervous System

• Enteric nervous system (ENS): Controls the digestive tract independently of the CNS.

Functional Classes of Neurons

• Afferent neurons: Carry information from sensory receptors to the CNS.
• Efferent neurons: Carry information from the CNS to muscles and glands.
• Interneurons: Function within the CNS, connecting and processing information between neurons.

Afferent Neurons

• Afferent neurons contain sensory receptors that generate action potentials in response to specific stimuli.
• Axons carry sensory impulses towards the spinal cord.

Efferent Neurons

• Efferent neurons reside in the PNS.
• Cell bodies are located in the CNS.
• Axons exit the cell body and travel to muscles or glands.

Interneurons

• Interneurons are located within the CNS.
• They comprise approximately 99% of all neurons.
• Human brains have more than 100 billion interneurons.

White and Gray Matter

• The CNS consists of white and gray matter.
• Gray matter: Primarily composed of neuron cell bodies, dendrites, and unmyelinated axons.
• White matter: Contains myelinated axons, which appear white due to the myelin sheath.
• Glial cells: Present in both gray and white matter, supporting and protecting neurons.

Glial Cells or Neuroglia

• Glial cells support neurons physically, metabolically, and functionally.
• They do not conduct nerve impulses.
• Four types of glial cells: astrocytes, oligodendrocytes, microglia, and ependymal cells.

Types of Glial Cells

• Astrocytes: Form the blood-brain barrier and neural scar tissue.
• Oligodendrocytes: Form myelin sheaths around axons in the CNS.
• Microglia: Phagocytize debris and release nerve growth factor.
• Ependymal cells: Form cerebrospinal fluid and act as neural stem cells.

Protection of the Brain

• The skull bone protects the brain.
• The vertebral column protects the spinal cord.
• The meninges are three layers of protective membranes that cover the brain and spinal cord: dura mater, arachnoid, and pia mater.
• Cerebrospinal fluid (CSF) fills the subarachnoid space between the arachnoid and pia mater, cushioning and protecting the CNS.

Cerebrospinal Fluid (CSF)

• CSF is formed by the choroid plexuses in the ventricles of the brain.
• It surrounds the brain and spinal cord.
• CSF volume is approximately 125-150 ml.

Clinical Note: Hydrocephalus

• Hydrocephalus: Condition where CSF accumulates due to blocked circulation or reabsorption.
• Excess CSF pressure can damage brain tissue and lead to mental retardation.
• Treatment: Surgically shunting excess CSF to veins elsewhere in the body.

Test your knowledge on the organization of the nervous system, including the central and peripheral nervous systems. Explore the functions of the brain and its lobes, along with critical facts about brain health and energy requirements.