Central and Peripheral Nervous System Overview

Central Nervous System

Major division of the nervous system; includes brain and spinal cord.

Peripheral Nervous System

Contains all neurons outside the central nervous system.

Neurons

Specialized nerve cells for processing environmental information.

Dendrites

Receive impulses from other neurons and conduct them.

Axon

Transmits impulses to other neurons or muscles.

Sensory Neurons

Send impulses from receptors to the brain and spinal cord.

Interneurons

Carry impulses between sensory and motor neurons.

Motor Neurons

Transmit impulses from CNS to glands or muscles.

Reflex Arc

Pathway of a nerve impulse involving sensory, interneuron, and motor neurons.

Action Potential

Nerve impulse caused by sodium and potassium movement.

Nodes of Ranvier

Gaps in the myelin sheath that speed up impulses.

Synapse

Gap between axon of one neuron and dendrite of another.

Neurotransmitters

Chemicals that transmit signals across synapses.

Cerebrum

Largest brain part; responsible for thought and sensory perception.

Cerebellum

Controls balance, posture, and coordination.

Brain Stem

Connects brain to spinal cord; regulates vital functions.

Medulla Oblongata

Controls breathing rate, heart rate, and blood pressure.

Pons

Aids in regulating breathing.

Hypothalamus

Regulates homeostasis, including temperature and appetite.

Spinal Cord

Nerve column extending from brain; processes reflexes.

Somatic Nervous System

Relays information between external sensory receptors and CNS.

Autonomic Nervous System

Regulates involuntary body functions; includes sympathetic and parasympathetic systems.

Sympathetic Nervous System

Prepares body for 'fight or flight' responses.

Parasympathetic Nervous System

Promotes 'rest and digest' functions.

Autonomic Nervous System

Carries impulses to internal organs involuntarily.

Sympathetic Nervous System

Active during emergencies, increases heart and breathing rates.

Parasympathetic Nervous System

Active during relaxation, conserves energy.

Taste Buds

Detect sweet, sour, salty, and bitter flavors.

Sensory Receptors

Respond to temperature, pressure, and pain.

Cornea

Transparent front part of the eye.

Pupil

Opening that regulates light entering the eye.

Lens

Inverts and projects images onto the retina.

Retina

Contains rods and cones for light and color detection.

Auditory Canal

Passage for sound waves to reach the tympanum.

Tympanum

Membrane that vibrates in response to sound.

Cochlea

Fluid-filled structure generating nerve impulses from vibrations.

Semicircular Canals

Inner ear structures for balance and body position.

Drugs

Substances altering body function, natural or artificial.

Stimulants

Increase alertness and physical activity; examples include nicotine.

Depressants

Slow down the central nervous system; examples include alcohol.

Dopamine

Neurotransmitter often affected by drugs.

Tolerance

Need for increased drug amounts for same effect.

Addiction

Psychological or physiological dependence on a drug.

Neurotransmitter

Chemical messenger transmitting signals across synapses.

Reflex Arc

Pathway for reflex actions involving sensory and motor neurons.

Sensory Structures

Organs detecting motion, temperature, taste, smell, sight.

Counseling

Often necessary for overcoming drug addiction.

Digestive System

System converting food into usable forms and waste removal.

Digestive Tract

Muscular tube from mouth to anus for digestion.

Accessory Organs

Organs aiding digestion by secreting substances.

Peristalsis

Rhythmic contractions pushing food through digestive tract.

Mechanical Digestion

Physical breakdown of food, e.g., teeth.

Chemical Digestion

Breakdown of food by digestive enzymes.

Absorption

Nutrients taken into blood from small intestine.

Elimination

Removal of waste from the body.

Mucosa

Inner lining secreting mucus and digestive juices.

Submucosa

Connective tissue with blood and lymphatic vessels.

Muscularis Externa

Smooth muscle layers aiding movement in tract.

Serosa

Outer layer of digestive tract providing protection.

Salivary Glands

Produce saliva to aid in digestion.

Liver

Processes nutrients and produces bile for digestion.

Gallbladder

Stores bile produced by the liver.

Pancreas

Secretes digestive enzymes and buffers into intestines.

Small Intestine

Primary site for nutrient absorption.

Large Intestine

Absorbs water and forms waste.

Anus

Final part of digestive tract for waste expulsion.

Teeth

Mechanical tools for breaking down food.

Tongue

Muscle aiding in food manipulation and swallowing.

Serosa

Visceral peritoneum layer insulating organs.

Mesentery

Tissue supporting blood vessels in digestive tract.

Mucosa

Innermost layer of digestive tract.

Submucosa

Layer providing support and containing blood vessels.

Muscularis Externa

Layer responsible for digestive tract movement.

Oral Cavity

Area for mechanical processing and mixing food.

Pharynx

Muscular tube connecting mouth to esophagus.

Esophagus

Tube transporting food to stomach.

Stomach

Organ for chemical and mechanical food processing.

Small Intestine

Site for enzymatic digestion and nutrient absorption.

Large Intestine

Responsible for dehydration and compaction of waste.

Salivary Glands

Produce saliva for food digestion and lubrication.

Mastication

Chewing process increasing food surface area.

Amylase

Enzyme initiating carbohydrate digestion in mouth.

Lipase

Enzyme starting lipid digestion in oral cavity.

Labia

Lips forming anterior boundary of oral cavity.

Uvula

Dangling structure at soft palate's posterior margin.

Gingivae

Gums surrounding the base of teeth.

Lingual Frenulum

Tissue connecting tongue to floor of mouth.

Pharyngeal Tonsil

Lymphoid tissue located in the nasopharynx.

Palatine Tonsil

Lymphoid tissue located at the entrance to pharynx.

Esophagus

Tube connecting throat to stomach.

Bolus

Moist mass of food entering digestive tract.

Peristalsis

Sequential muscle contractions moving food along tract.

Muscularis externa

Layer responsible for peristalsis in digestive tract.

Stomach

Muscular, expandable organ for food digestion.

Chyme

Soupy mixture of food and gastric secretions.

Rugae

Folds in stomach mucosa that flatten when expanded.

Pyloric sphincter

Regulates chyme release into duodenum.

Gastric glands

Secrete gastric juice in stomach for digestion.

Gastric juice

Acidic fluid containing enzymes for digestion.

Intestinal villi

Finger-like projections increasing intestinal surface area.