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Midterm Exam Review: Special Senses, Endocrine, Cardiovascular, Blood, and Lymphatic Systems

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Chapter 15 – Special Senses

Visual Disorders

Visual disorders affect the way light is focused on the retina, impacting vision clarity.

  • Myopia (Nearsightedness): The eye is too long or the cornea is too curved, causing light to focus in front of the retina. Distant objects appear blurry.

  • Hyperopia (Farsightedness): The eye is too short or the cornea is too flat, causing light to focus behind the retina. Close objects appear blurry.

Overview of Special Senses

The special senses include olfaction, gustation, vision, hearing, and vestibular sensation. Each has specialized organs and neural pathways.

  • Olfaction: Sense of smell; unique as it bypasses the thalamus.

  • Gustation: Sense of taste.

  • Vision: Sense of sight.

  • Hearing: Sense of sound.

  • Vestibular Sensation: Sense of equilibrium and balance.

Olfactory Pathway

Olfaction is the only sensory pathway that does not relay through the thalamus before reaching the cortex.

  • Olfactory neurons → Olfactory bulb (mitral cells) → Olfactory tract → Primary olfactory cortex

Key Point: Smell is the only sensory pathway that does not go through the thalamus first.

Gustation (Taste)

Taste is detected by taste buds located on different types of papillae on the tongue.

  • Vallate: Largest papillae, contain many taste buds.

  • Fungiform: Mushroom-shaped, contain few taste buds.

  • Foliate: Located on the sides of the tongue.

  • Filiform: No taste buds; provide texture.

Taste Pathway: Taste buds → Facial, glossopharyngeal, and vagus nerves → Solitary nucleus → Thalamus → Gustatory cortex (parietal lobe)

  • Five Taste Sensations:

    1. Sweet – sugars

    2. Sour – acids

    3. Salty – sodium and potassium ions

    4. Bitter – nitrogen-containing compounds

    5. Umami – glutamate (savory, meaty taste)

Eye Structures and Functions

The eye is composed of three main layers, each with specialized structures and functions.

  • Fibrous Layer:

    • Sclera: White of the eye; provides structure and protection.

    • Cornea: Transparent; allows light to enter the eye.

  • Vascular Layer:

    • Choroid: Supplies blood; prevents light scattering.

    • Ciliary Body: Changes lens shape for focusing.

  • Retina (Neural Layer):

    • Rods: Detect dim light; peripheral vision.

    • Cones: Detect color; detailed vision.

    • Macula Lutea: Central vision.

    • Fovea Centralis: Sharpest vision; high concentration of cones.

Ear Structures and Hearing

The ear is divided into three regions, each with distinct roles in hearing and balance.

  • Outer Ear: Auricle (pinna), external auditory canal, tympanic membrane (eardrum).

  • Middle Ear: Malleus (hammer), incus (anvil), stapes (stirrup), auditory tube, oval window.

  • Inner Ear: Vestibule (utricle & saccule), semicircular canals, cochlea (hearing).

Sound Wave Pathway: Pinna → Auditory canal → Tympanic membrane → Malleus → Incus → Stapes → Oval window → Cochlea → Organ of Corti → Cochlear nerve → Brain

Equilibrium

  • Static Equilibrium: Senses head position and tilt.

  • Dynamic Equilibrium: Senses movement and rotation.

Chapter 16 – Endocrine System

Hormone Functions

Hormones are chemical messengers that regulate various physiological processes.

  • Maintain homeostasis

  • Regulate metabolism

  • Promote growth

Types of Chemical Signals

Type

Action

Endocrine

Travels through blood to distant targets

Paracrine

Acts on nearby cells

Autocrine

Acts on the same cell that secreted it

Hormone Secretion Stimuli

  • Hormonal: Triggered by other hormones.

  • Humoral: Triggered by changes in blood composition.

  • Neural: Triggered by nerve signals.

Negative Feedback (Simple)

Negative feedback maintains hormone levels within a narrow range.

  1. Hormone levels drop

  2. Gland releases hormone

  3. Hormone levels rise

  4. Release stops

Thyroid Hormone Regulation

Thyroid hormone secretion is regulated by a hormonal axis:

  • TRH (hypothalamus) → TSH (anterior pituitary) → T3/T4 (thyroid gland)

Adrenal Cortex Layers

The adrenal cortex has three layers, each producing different hormones:

  • Glomerulosa

  • Fasciculata

  • Reticularis

Pancreatic Islets

Cell Type

Hormone

Alpha

Glucagon

Beta

Insulin

Delta

Somatostatin

Chapter 17 – Cardiovascular System

Blood Flow Through the Heart

Blood flows through the heart in a specific sequence to ensure oxygenation and systemic circulation.

  • Body → Superior/Inferior vena cava → Right atrium → Tricuspid valve → Right ventricle → Pulmonary valve → Pulmonary arteries → Lungs → Pulmonary veins → Left atrium → Mitral (bicuspid) valve → Left ventricle → Aortic valve → Aorta → Body

Cardiac Conduction Pathway

The heart's electrical system coordinates contraction.

  • SA node → AV node → AV bundle → Right and left bundle branches → Purkinje fibers

Cardiac Muscle Action Potential

Cardiac muscle cells have a unique action potential with distinct phases:

  1. Depolarization

  2. Initial repolarization

  3. Plateau phase

  4. Repolarization

Chapter 18 – Blood Vessels

Blood Vessel Types and Functions

Vessel

Function

Arteries

Carry blood away from the heart

Capillaries

Exchange nutrients and gases with tissues

Veins

Return blood to the heart

  • Arteries: Thick walls to withstand high pressure.

  • Veins: Contain valves to prevent backflow; hold about 70% of blood volume.

Blood Pressure

  • Normal BP: 120/80 mmHg

  • Systolic: 120 mmHg (ventricular contraction)

  • Diastolic: 80 mmHg (ventricular relaxation)

  • MAP (Mean Arterial Pressure): 95 mmHg

Capillary Exchange

  • Hydrostatic Pressure: Pushes fluid out of capillaries.

  • Osmotic Pressure: Pulls fluid into capillaries.

Chapter 19 – Blood

Functions of Blood

  • Transports gases (O2, CO2)

  • Transports nutrients

  • Provides immunity

  • Clotting

  • Temperature regulation

  • pH regulation

Formed Elements of Blood

  • Red Blood Cells (Erythrocytes): Carry O2 and CO2; produced in red bone marrow; production stimulated by erythropoietin (EPO) from kidneys.

  • Platelets: Cell fragments; help clot blood; lifespan 7–10 days.

  • White Blood Cells (Leukocytes):

    WBC Type

    Function

    Neutrophils

    Fight bacteria; phagocytes

    Eosinophils

    Combat parasites; involved in allergies

    Basophils

    Release histamine; inflammation

    Monocytes

    Become macrophages

    Lymphocytes

    Immune defense (B and T cells)

  • B cells: Produce antibodies.

  • T cells: Destroy infected or abnormal cells.

Hemostasis (Blood Clotting)

  1. Vascular spasm

  2. Platelet plug formation

  3. Coagulation

  4. Clot retraction

  5. Thrombolysis (clot breakdown)

  • Coagulation Pathways:

    • Intrinsic: Triggered by internal vessel trauma.

    • Extrinsic: Triggered by external trauma.

Blood Typing

  • A antigen

  • B antigen

  • AB antigen

  • O: No antigen

  • Rh+: Rh antigen present

  • Rh-: Rh antigen absent

Chapter 20 – Lymphatic System

Functions of the Lymphatic System

  • Returns excess fluid to the bloodstream

  • Absorbs fats from the digestive tract

  • Provides immune defense

Major Lymphatic Structures

  • Lymphatic vessels

  • Lymph nodes

  • Thymus

  • Spleen

  • Tonsils

Lymph Node Functions

  • Filter lymph

  • Remove pathogens

  • House immune cells

Thymus

  • Site of T-cell maturation

Spleen

  • Filters blood

  • Removes old red blood cells

  • Stores platelets

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