Chapter 17 – The Special Senses

Overview of the Special Senses

The special senses include vision, hearing, equilibrium, taste, and smell. These senses rely on specialized organs and receptors to detect specific stimuli and transmit information to the brain for interpretation.

• Olfactory (Smell) Receptors: Specialized cells in the nasal cavity that detect airborne chemicals (odorants).

• Gustatory (Taste) Receptors: Located in taste buds, these detect dissolved chemicals in food and beverages.

• Photoreceptors: Cells in the retina (rods and cones) that respond to light and enable vision.

• Auditory (Hearing) Receptors: Hair cells in the cochlea that detect sound vibrations.

• Equilibrium Receptors: Located in the vestibular apparatus of the inner ear, these detect changes in head position and movement.

Vision

• Blind Spot (Optic Disc): The area on the retina where the optic nerve exits; lacks photoreceptors, so no image is detected here.

• Photoreceptors: Rods detect light intensity (black and white vision), while cones detect color and provide sharp vision.

• Fovea Centralis: The area of the retina with the highest concentration of cones; responsible for sharp central vision.

• Lens: Focuses light onto the retina; its shape is adjusted by the ciliary muscles.

• Accommodation: The process by which the lens changes shape to focus on near or distant objects.

• Pathway of Light: Cornea → Aqueous humor → Lens → Vitreous humor → Retina.

Hearing and Equilibrium

• Auditory Pathway: Sound waves → Tympanic membrane → Ossicles (malleus, incus, stapes) → Oval window → Cochlea → Hair cells → Auditory nerve.

• Cochlea: Spiral-shaped organ responsible for converting sound vibrations into nerve impulses.

• Semicircular Canals: Detect rotational movements of the head; important for balance.

• Vestibule: Contains the utricle and saccule, which detect linear acceleration and head position.

• Equilibrium: Maintained by input from the vestibular apparatus, visual system, and proprioceptors.

Taste and Smell

• Taste Buds: Sensory organs on the tongue that detect sweet, sour, salty, bitter, and umami flavors.

• Olfactory Epithelium: Contains olfactory receptor cells that detect odorants.

• Cribriform Plate: Part of the ethmoid bone; olfactory nerves pass through here to reach the olfactory bulb.

Chapter 18 – The Endocrine System

Overview of the Endocrine System

The endocrine system consists of glands that secrete hormones directly into the bloodstream to regulate body functions. It works closely with the nervous system to maintain homeostasis.

• Hormones: Chemical messengers that regulate physiological processes such as growth, metabolism, and reproduction.

• Endocrine Glands: Include the pituitary, thyroid, parathyroid, adrenal, pancreas, and gonads.

• Target Cells: Cells with specific receptors for a given hormone.

Major Endocrine Glands and Hormones

• Pituitary Gland: The "master gland" that secretes hormones influencing other endocrine glands (e.g., TSH, ACTH, GH, ADH, oxytocin).

• Thyroid Gland: Produces thyroid hormones (T3, T4) that regulate metabolism.

• Parathyroid Glands: Secrete parathyroid hormone (PTH), which increases blood calcium levels.

• Adrenal Glands: Produce corticosteroids (cortisol, aldosterone) and catecholamines (epinephrine, norepinephrine).

• Pancreas: Secretes insulin and glucagon to regulate blood glucose.

• Gonads: Ovaries and testes produce sex hormones (estrogen, progesterone, testosterone).

Hormone Regulation and Feedback

• Negative Feedback: The most common mechanism; hormone secretion is inhibited by the hormone's own effects.

• Example: High blood glucose stimulates insulin release; insulin lowers glucose, which then inhibits further insulin release.

• Hypothalamus: Regulates the pituitary gland via releasing and inhibiting hormones.

Key Terms

• Gonadotropins: Hormones (FSH, LH) that stimulate the gonads.

• Antagonists: Hormones or drugs that block the action of another substance.

Chapter 19 – The Blood

Functions and Components of Blood

Blood is a connective tissue that transports gases, nutrients, hormones, and waste products throughout the body. It also plays a role in immunity and homeostasis.

• Red Blood Cells (Erythrocytes): Transport oxygen and carbon dioxide.

• White Blood Cells (Leukocytes): Defend against infection and disease.

• Platelets (Thrombocytes): Involved in blood clotting.

• Plasma: The liquid component of blood, containing water, proteins (albumin, globulins, fibrinogen), electrolytes, and nutrients.

Hematopoiesis and Blood Typing

• Hematopoiesis: The process of blood cell formation, primarily in the red bone marrow.

• Blood Types: Determined by the presence of specific antigens (A, B, AB, O) and antibodies (anti-A, anti-B) on red blood cells.

• Rh Factor: Another antigen that can be present (+) or absent (−) on red blood cells.

Blood Clotting and Immunity

• Fibrinogen: A plasma protein converted to fibrin during clot formation.

• Formed Elements: The cellular components of blood (RBCs, WBCs, platelets).

• Phagocytosis: The process by which certain WBCs (e.g., neutrophils, macrophages) engulf and destroy pathogens.

Table: Main Blood Components and Functions

Chapter 20 – The Heart

Structure and Function of the Heart

The heart is a muscular organ that pumps blood through the circulatory system. It consists of four chambers: two atria and two ventricles.

• Apex: The pointed end of the heart, directed downward and to the left.

• Base: The broad, superior portion of the heart where major vessels attach.

• Pericardial Cavity: The space between the layers of the pericardium that contains fluid to reduce friction.

Blood Flow Through the Heart

• Deoxygenated blood enters the right atrium from the body via the superior and inferior vena cava.

• Blood flows to the right ventricle, then is pumped to the lungs via the pulmonary artery for oxygenation.

• Oxygenated blood returns to the left atrium via the pulmonary veins, then to the left ventricle, and is pumped out to the body via the aorta.

Heart Valves and Conduction System

• Valves: Ensure one-way flow of blood (tricuspid, pulmonary, mitral, aortic).

• SA Node (Sinoatrial Node): The heart's natural pacemaker; initiates electrical impulses.

• EKG (Electrocardiogram): Measures the electrical activity of the heart; P wave (atrial depolarization), QRS complex (ventricular depolarization), T wave (ventricular repolarization).

Table: Heart Chambers and Major Vessels

Key Terms

• Antagonists: Muscles or hormones that oppose the action of another.

• Receptors: Structures that detect stimuli and initiate a response.

• Taste Buds: Sensory organs for taste.

Additional info:

• Some terms (e.g., "cribriform plate," "gonadotropins") are included as key vocabulary for further study.

• For equations related to cardiac output: