Nervous System Structure & Function

Overview of Nervous System

The nervous system is a complex network responsible for communication, control, and integration of body functions. It is composed of specialized cells and structures that transmit signals throughout the body.

• Two main cell types: Neurons (signal transmission) and glial cells (support and protection).

• Neurons are the primary functional units, while glia provide metabolic and structural support.

Neuron Structure & Signal Transmission

• Dendrites: Receive incoming signals from other neurons.

• Axon: Transmits electrical impulses away from the cell body.

• Axonal transport: Movement of materials along the axon, essential for neuron function.

• Location of interneurons: Found in the CNS, acting as connectors between sensory and motor neurons.

Synapses & Neurotransmission

Synapses are specialized junctions where neurons communicate via chemical or electrical signals.

• Types of synapses: Electrical (direct ion flow) and Chemical (neurotransmitter release).

• Components of a synapse: Presynaptic terminal, vesicles, neurotransmitter, synaptic cleft, receptors, postsynaptic side.

• Neurotransmitter release: Triggered by calcium influx, vesicles fuse with the membrane atthe presynaptic terminal. /

• Synaptic cleft: The gap filled with neurotransmitter molecules during signal tra nsmission.

• Amount of neurotransmitter released: Depends on calcium ion concentration ().

Neurotransmitters: Types & Functions

• Most common inhibitory neurotransmitter: GABA (calms neural activity).

• Most common excitatory neurotransmitter: Glutamate (stimulates neural activity).

• EPSP (Excitatory Postsynaptic Potential): Increases likelihood of neuron firing.

• IPSP (Inhibitory Postsynaptic Potential): Decreases likelihood of neuron firing.

Myelin Sheath Production

• PNS: Schwann cells produce myelin.

• CNS: Oligodendrocytes produce myelin.

• Myelin increases speed of electrical signal transmission.

Voltage-Gated Channels & Action Potentials

• Location: Found on axons (action zone).

• Opening threshold: Sodium channels open at approximately .

• Resting membrane potential: Mainly determined by potassium ion concentration ().

• Hypokalemia: Low , leads to reduced cell excitability.

• Hyperkalemia: High , increases cell excitability and risk of arrhythmias.

Summation in Neurons

• Temporal summation: Rapid, repeated firing from one input.

• Spatial summation: Multiple inputs firing together.

Autonomic Nervous System (ANS)

• Controls: Automatic functions (heart, glands, smooth muscle).

• Subdivisions: Sympathetic ("speed") and Parasympathetic ("peace").

Brain Areas & Functions

• Hypothalamus: Regulates temperature, hunger, hormones ("home thermostat").

• Broca's area: Controls speech production.

• Frontal lobe: Responsible for logic and reasoning.

• Hippocampus: Essential for memory formation.

• Limbic system: Involved in emotion.

Metabolism & Glucose Regulation

Glucose Homeostasis

Glucose balance is maintained by hormones and metabolic pathways to ensure energy supply and storage.

• Insulin: Lowers blood glucose by promoting uptake into cells.

• Glucagon: Raises blood glucose by stimulating liver to release stored sugar.

Glucose Tolerance: Normal vs. Diabetic

• Normal: Quick rise and fall in blood glucose after intake.

• Diabetic: Higher peak and slower return to baseline.

Glycogen: Storage & Function

• Glycogen: Main storage form of glucose, found in liver and muscle.

• Acts as a glucose reservoir for energy needs.

Fed vs. Fasted States

• Fed state: Insulin promotes glucose storage.

• Fasted state: Glucagon stimulates glucose release.

Ketone Bodies Production

• Produced during fasting: Liver converts fat into ketones when glucose is low.

Metabolic Pathways

• Gluconeogenesis: Formation of new glucose from non-carbohydrate sources.

• Glycogenolysis: Breakdown of glycogen to release glucose.

• Glycolysis: Splitting of glucose for energy production.

Anabolism vs. Catabolism

• Anabolism: Building up molecules (e.g., protein synthesis).

• Catabolism: Breaking down molecules (e.g., glucose breakdown).

Metabolic Rate Measurement

• Oxygen use: Indicates metabolic activity.

Metabolic Syndrome in Diabetes

• Features: High blood sugar, high blood pressure, high fat, large waist circumference.

• Increases risk for cardiovascular disease.

Hormonal Regulation

• ADH (Antidiuretic Hormone): Conserves water in kidneys, reducing urine output.

Tables

Comparison of Synapse Types

Summary Table: Key Brain Areas & Functions

Additional info:

• Antidepressants (SSRIs) work by blocking serotonin reuptake, increasing its availability in the synaptic cleft.

• Associative learning involves connecting two stimuli (e.g., Pavlov's dog experiment).

• Feeding center in the brain is located in the hypothalamus.