Nervous system- Neurons

NERVOUS SYSTEM

AGENDA

• Functions of the Nervous System

• Anatomy of the Nervous System

• Cerebral Spinal Fluid

• Spinal Cord

• Physiology of the Nervous System

FUNCTIONS OF THE NERVOUS SYSTEM

• Monitoring Changes: Observes internal and external body changes known as stimuli, with gathered information referred to as sensory input.

• Interpretation of Sensory Input: Processes sensory input and determines appropriate actions through integration.

• Effect Responses: Activates muscles or glands (effectors) via motor output to produce a response.

• Mental Activity: Center of consciousness, thinking, and memory; the brain plays a crucial role in these activities.

• Homeostasis: Maintains internal stability by monitoring and responding to changes.

ANATOMY OF THE NERVOUS SYSTEM

Central Nervous System (CNS)

• Comprises the brain and spinal cord.

• Responsible for integrating, processing, and coordinating sensory data and motor commands.

• Information processing consists of integration and distribution within the CNS.

Peripheral Nervous System (PNS)

• Encompasses all neural tissue outside the CNS.

• Motor Division: Carries commands from the CNS to peripheral tissues.

• Sensory Division: Brings information to the CNS from peripheral receptors.

• Somatic Nervous System (SNS): Controls skeletal muscle contractions.

• Autonomic Nervous System (ANS): Regulates automatic actions of smooth muscle, cardiac muscle, glands, and adipose tissue.

• Receptors: Sensory structures monitoring changes in the environment, including somatic (touch, pressure) and visceral (internal organ) sensations.

CNS & PNS STRUCTURE

Brain Regions

• Frontal Lobe: Involved in consciousness, motor control, and higher cognitive functions.

• Parietal Lobe: Processes sensory input related to touch, pain, and temperature.

• Occipital Lobe: Responsible for visual processing.

• Temporal Lobe: Involved in auditory processing and language comprehension.

• Cerebellum: Coordinates movement and balance.

Spinal Cord

• Serves as a pathway for neural signals between the brain and the body.

PNS FUNCTIONAL CLASSIFICATIONS

Sensory Division (Afferent Division)

• Nerves that convey impulses to the CNS.

• Somatic Sensory Fibers: Deliver impulses from skin, skeletal muscles, and joints.

• Visceral Sensory Fibers: Transmit impulses from internal organs.

Motor Division (Efferent Division)

• Carries impulses from the CNS to effectors, including muscles and glands.

• Subdivisions:

  • Somatic Nervous System: Controls voluntary muscle movement.

  • Autonomic Nervous System: Manages involuntary functions, further divided into sympathetic (fight or flight) and parasympathetic (rest and digest).

NERVOUS TISSUE: STRUCTURE AND FUNCTION

Types of Neuroglia

• Astrocytes: Star-shaped cells forming a barrier between blood and neurons.

• Microglia: Phagocytes that clear out debris.

• Ependymal Cells: Line CNS cavities and circulate cerebrospinal fluid (CSF).

• Oligodendrocytes: Produce myelin sheaths in the CNS.

• Schwann Cells: Form myelin sheaths around PNS nerve fibers.

• Satellite Cells: Cushion and protect nerve cells in the PNS.

NEURONS

Structure

• Cell Body: Metabolic center of the neuron.

• Processes: Dendrites convey messages toward the cell body, while axons send impulses away.

• Axon Hillock: Cone-shaped region from which axons arise.

• Axon Terminals: Contain vesicles with neurotransmitters for signal transmission to other neurons.

• Synaptic Cleft: Gap between axon terminals and the next neuron.

Myelin Sheaths

• Made of myelin, which insulates and speeds up transmission of impulses.

• Nodes of Ranvier: Gaps in myelin sheath that facilitate faster signal transmission.

TYPES OF NEURONS

• Sensory Neurons: Carry impulses from receptors to the CNS.

• Motor Neurons: Transmit impulses from the CNS to muscles and glands.

• Interneurons: Connect sensory and motor neurons; found in pathways.

• Multipolar Neurons: Most common type, with multiple processes; found in motor and association neurons.

• Bipolar Neurons: Rare, with an axon and a dendrite; involved in sensory processing.

• Unipolar Neurons: Single process that divides into two; common in sensory pathways.