Anatomy & Physiology Study Notes: Neurology and the Nervous System

Hybrid: Neurology

Function of the Nervous System

The nervous system is a complex network responsible for communication, control, and regulation of bodily functions. It integrates sensory input, coordinates movement, and maintains homeostasis.

• Control: The brain acts as the central command, integrating all body functions.

• Communication Network: Nerve pathways relay information throughout the body, ensuring rapid and coordinated responses.

• Controls Movement: Voluntary actions (e.g., skeletal muscle movement) and involuntary actions (e.g., breathing, glandular release).

• Homeostatic Control: Regulates hormonal influence, immune response, temperature, and other vital processes.

Control	Communication Network
"Brain" is the boss Integrates ALL body functions	Nerve "highways" relay information throughout the body
Controls Movement	Homeostatic Control Over the Body
Skeleton is voluntary Breathing, etc. involuntary Glandular release	Hormonal influence Immune response Temperature, Breathing, etc.

Key Questions in Nervous System Analysis

When analyzing a nerve or neural pathway, consider:

• Is it part of the Central Nervous System (CNS) or Peripheral Nervous System (PNS)?

  PNS • Nerves the organ—they can be motor, sensory or mixed • Spinal nerves – 31 pairs are always missed. • Cranial nerves vary • Myelin sheaths are made by Schwann Cells CNS • Tracts- ascending are sensory, and descending are motor • Think of what is protected by the CSF to define boundaries • Myelin sheaths are from Oligodendrocytes BOTH HAVE NEURONS –WHICH RELEASE THE NEUROTRANSMITER AT THE AXON TERMINAL. The neurotransmitter will vary dependent if motor or sensory, PNS or CNS

• Is it motor or sensor Motor: Involves action such as movement, thinking, and decision-making.

  • Sensory: Involves perception and feeling. Somatic sensory relates to the body (e.g., touch), while special sensory involves cranial nerves (e.g., vision, hearing).

Divisions of the Nervous System

Central Nervous System (CNS)

The CNS consists of the brain and spinal cord. It processes information and coordinates activity throughout the body.

• Sensory tracts: Ascending pathways that carry sensory information to the brain.

• Motor tracts: Descending pathways that transmit motor commands from the brain to the body.

Peripheral Nervous System (PNS)

The PNS connects the CNS to limbs and organs. It includes cranial nerves (CN) and spinal nerves.

• Somatic and visceral connections: Links the CNS to body parts.

• Sensory (Afferent) nerves: Carry information toward the CNS.

• Motor (Efferent) nerves: Carry commands away from the CNS.

Properties and Types of Neurons

Special Properties of Neurons

• Irritability: The ability to respond to a stimulus.

• Propagation of Impulses: The ability to conduct electrical impulses along the cell membrane.

Functional Classification of Neurons

• Sensory Neurons: Receive sensory stimuli from the environment or within the body (often unipolar).

• Motor Neurons: Control effector organs such as muscles and glands.

• Interneurons: Found in the CNS, connect sensory and motor neurons, and facilitate communication within the CNS.

• Neurosecretory Neurons: Specialized neurons that synthesize and secrete hormones.

Types of Nerve Cells

• Neurons:

  • Polarize/repolarize to transmit signals.

  • Release neurotransmitters.

  • Multipolar: Motor neurons.

  • Unipolar: Somatic sensory neurons.

  • Bipolar: Special sensory neurons (e.g., in the retina).

• Glial Cells (Neuroglia):

  • Supportive cells, highly mitotic.

  • Astrocytes: Maintain the blood-brain barrier.

  • Microglia: Act as immune cells (macrophage equivalent).

  • Ependymal Cells: Produce cerebrospinal fluid (CSF).

  • Schwann Cells/Oligodendrocytes: Form myelin in the PNS/CNS, respectively.

Neuroglia

Neuroglia, or glial cells, are non-neuronal cells that provide structural and functional support to neurons. They are essential for the development, maintenance, and protection of the nervous system.

• Outnumber neurons by at least 10:1, but are much smaller.

• Occupy about 50% of the total volume of nerve tissue.

• Four main types in the CNS: Astrocytes, Oligodendrocytes, Microglia, Ependymal cells.

Neuroglial Cell Types & Functions

Cell Type	Location	Function
Astrocytes	CNS	Maintain blood-brain barrier, provide structural support, regulate ion and nutrient concentrations.
Oligodendrocytes	CNS	Myelinate CNS axons, provide structural framework.
Microglia	CNS	Immune defense, remove debris and pathogens by phagocytosis.
Ependymal Cells	CNS	Line ventricles of brain and spinal cord, produce and circulate CSF.
Satellite Cells	PNS	Surround neuron cell bodies in ganglia, regulate neurotransmitter levels.
Schwann Cells	PNS	Myelinate PNS axons, assist in regeneration of damaged fibers.

Example: Oligodendrocytes myelinate multiple axons in the CNS, while Schwann cells myelinate a single axon in the PNS.

Additional info: Myelination increases the speed of nerve impulse conduction via saltatory conduction, where impulses jump between nodes of Ranvier.