Anatomy of the Nervous System

Nervous System Overview

• The nervous system is the body's master system, responsible for coordinating and controlling all other systems.
• Functions include sensory input, integration, and motor output.

Functions of the Nervous System

• Sensory Input: Gathers information about internal and external changes, termed stimuli.
• Integration: Processes and interprets sensory input to determine necessary actions.
• Motor Output: Produces response to stimuli; activates muscles or glands known as effectors.

Structural Classification

• Central Nervous System (CNS): Comprises the brain and spinal cord, developing from the embryonic neural tube, which forms the ventricles filled with cerebrospinal fluid.
• Peripheral Nervous System (PNS): Includes nerves outside the brain and spinal cord; consists of nerve fibers and ganglia with neuron cell bodies.

Neurons

• Neurons are specialized cells that facilitate communication between various body locations.

Functional Classification of Neurons

• Sensory (Afferent) Division (PNS): Carries information to the CNS from sensory receptors; includes cutaneous sense organs and proprioceptors.
• Motor (Efferent) Division (PNS): Transmits impulses away from the CNS and activates motor response; composed of somatic and autonomic subdivisions.

Autonomic Nervous System

• Somatic Nervous System: Voluntary control and conscious perception of stimuli.
• Autonomic Nervous System (ANS): Involuntary control consisting solely of motor nerves; divided into sympathetic and parasympathetic systems.

Sympathetic Division

• Originates from T1 to L2 spinal segments; short preganglionic and long postganglionic neurons send impulses to effectors.
• Neurotransmitters include norepinephrine and epinephrine; also known as the thoracolumbar division.
• Activates fight-or-flight response during emergencies and stress.

Parasympathetic Division

• Originates from brain stem and S1 to S4 segments; terminal ganglia located near or within effector organs.
• Utilizes acetylcholine as the neurotransmitter; referred to as the craniosacral division.
• Main role is maintaining homeostasis and supporting "rest-and-digest" functions.

Differences Between Somatic and Autonomic Nervous Systems

• Nerves: Somatic uses one motor neuron; autonomic involves preganglionic and postganglionic nerves.
• Effector Organs: Somatic acts on skeletal muscle; autonomic targets smooth muscle, cardiac muscle, and glands.
• Neurotransmitters: Somatic uses acetylcholine exclusively; autonomic can use acetylcholine, epinephrine, or norepinephrine.

Interneurons

• Located within the CNS; facilitate connections between sensory and motor neurons, primarily in the lateral horn of gray matter.

Support Cells (Glial Cells)

• Provide structure and support to neurons; critical for maintenance and function within the nervous system.

CNS Glial Cells

• Astrocytes: Most abundant, maintain blood-brain barrier, control chemical environment.
• Microglia: Act as immune cells, remove debris.
• Ependymal Cells: Line brain and spinal cavities, circulate and produce cerebrospinal fluid (CSF).
• Oligodendrocytes: Produce myelin sheath to insulate and protect nerve fibers, enhancing impulse transmission.

PNS Glial Cells

• Satellite Cells: Protect neuron cell bodies.
• Schwann Cells: Form myelin sheath in peripheral nerves.

Nervous System Overview

• The nervous system is the body's master system, responsible for coordinating and controlling all other systems.
• Functions include sensory input, integration, and motor output.

Functions of the Nervous System

• Sensory Input: Gathers information about internal and external changes, termed stimuli.
• Integration: Processes and interprets sensory input to determine necessary actions.
• Motor Output: Produces response to stimuli; activates muscles or glands known as effectors.

Structural Classification

• Central Nervous System (CNS): Comprises the brain and spinal cord, developing from the embryonic neural tube, which forms the ventricles filled with cerebrospinal fluid.
• Peripheral Nervous System (PNS): Includes nerves outside the brain and spinal cord; consists of nerve fibers and ganglia with neuron cell bodies.

Neurons

• Neurons are specialized cells that facilitate communication between various body locations.

Functional Classification of Neurons

• Sensory (Afferent) Division (PNS): Carries information to the CNS from sensory receptors; includes cutaneous sense organs and proprioceptors.
• Motor (Efferent) Division (PNS): Transmits impulses away from the CNS and activates motor response; composed of somatic and autonomic subdivisions.

Autonomic Nervous System

• Somatic Nervous System: Voluntary control and conscious perception of stimuli.
• Autonomic Nervous System (ANS): Involuntary control consisting solely of motor nerves; divided into sympathetic and parasympathetic systems.

Sympathetic Division

• Originates from T1 to L2 spinal segments; short preganglionic and long postganglionic neurons send impulses to effectors.
• Neurotransmitters include norepinephrine and epinephrine; also known as the thoracolumbar division.
• Activates fight-or-flight response during emergencies and stress.

Parasympathetic Division

• Originates from brain stem and S1 to S4 segments; terminal ganglia located near or within effector organs.
• Utilizes acetylcholine as the neurotransmitter; referred to as the craniosacral division.
• Main role is maintaining homeostasis and supporting "rest-and-digest" functions.

Differences Between Somatic and Autonomic Nervous Systems

• Nerves: Somatic uses one motor neuron; autonomic involves preganglionic and postganglionic nerves.
• Effector Organs: Somatic acts on skeletal muscle; autonomic targets smooth muscle, cardiac muscle, and glands.
• Neurotransmitters: Somatic uses acetylcholine exclusively; autonomic can use acetylcholine, epinephrine, or norepinephrine.

Interneurons

• Located within the CNS; facilitate connections between sensory and motor neurons, primarily in the lateral horn of gray matter.

Support Cells (Glial Cells)

• Provide structure and support to neurons; critical for maintenance and function within the nervous system.

CNS Glial Cells

• Astrocytes: Most abundant, maintain blood-brain barrier, control chemical environment.
• Microglia: Act as immune cells, remove debris.
• Ependymal Cells: Line brain and spinal cavities, circulate and produce cerebrospinal fluid (CSF).
• Oligodendrocytes: Produce myelin sheath to insulate and protect nerve fibers, enhancing impulse transmission.

PNS Glial Cells

• Satellite Cells: Protect neuron cell bodies.
• Schwann Cells: Form myelin sheath in peripheral nerves.