Nonpolar hormones must be transported by carrier proteins in plasma, but can diffuse directly through the plasma membrane. Receptors for nonpolar hormones are located inside cells.
Examples include: steroids (cortisol, testosterone, estrogen, progresterone) produced by adrenal cortex/gonads and thyroid hormones produced by the thyroid gland.
Describe polar hormones and give examples
Polar hormones dissolve in plasma, but cannot diffuse through the plasma membrane. Receptors for polar hormones are located in the plasma membrane of cells, and they act through second messengers.
Examples include epinephrine (adrenaline) produced by the adrenal medulla and polypeptides, proteins, and glycoproteins (most hormones) produced by the hypothalamus, pituitary, pancreas, and parathyroid.
Describe the hypothalamic control of the anterior pituitary
Hypothalamus secretes releasing hormones (RH) and inhibiting hormones (IH) to the hypothalamo-hypophyseal portal system. This controls anterior pituitary hormone secretion/inhibition.
Describe the hypothalamic control of the posterior pituitary
Neurosecretory neurons in the hypothalamus produce two different peptide hormones (ADH and Oxytocin) which then transported and stored in the posterior pituitary. They are released from the posterior pituitary when the neurons undergo an AP.
ADH effects in detail
(AKA Vasopressin) increases water retention by the kidneys, decreases urine volume (opposite of diuresis), constricts blood vessles
Oxytocin effects in detail
Uterine contraction during childbirth (labor) and milk letdown during breastfeeding
Describe the structure of the pituitary (including embryological origins) and alternate names.
Hypophysis – extends from the inferior surface of the hypothalamus, linked to hypothalamus by infundibulum
Posterior lobe (neurohypophysis) is a downgrowth from the brain
Anterior lobe (adenohypophysis) is derived from oral epithelium
What type of hormones (general) does the anterior pituitary secrete, and which cells secrete them?
Different cell types secrete 6 peptide (polar) hormones
List the hormones secreted by the anterior pituitary, their functions, and their releasing hormone (if applicable).
TSH (Thyroid stimulating hormone) – activates thyroid gland, increases thyroid hormones, increases size of thyroid gland, stimulated by TRH
ACTH (Adrenocorticotrophic hormone) – activates adrenal cortex to release cortisol, stimulated by CRH [usually in times of stress]
GH (Growth hormone) – stimulates growth, protein synthesis, fat breakdown, increases blood glucose levels [works at epiphysial plate]
Prolactin – breast development and milk production during pregnancy
LH (Lutenizing hormone)
FSH (Follicle stimulating hormone) – females: regulates ovaries (egg) and female sex hormones (estrogen and progesterone), males: regulates testes (sperm) and male sex hormones (testosterone), stimulated by GnRH
What are the gonadotropins?
LH and FSH
How do the hypothalamus and pituitary regulate the hormone levels of the body (general)?
Hormone receptors are located in the hypothalamus and pituitary (in addition to target organs)
These receptors allow homeostasis of hormone levels (thereby hormone effects) through alteration of RH/IH concentration, sensitivity, etc
Describe the pituitary-gonad axis’s negative feedback loop.
GnRH (hypothalamus) stimulates FSH and LH secretion (anterior pituitary)
FSH and LH stimulate sex steroid secretion (gonads)
Sex steroids act on hypothalamus (inhibit GnRH secretion) and anterior pituitary (inhibit sensitivity to GnRH)
Less stimulation of the gonads causes decreased secretion of sex steroids
Describe the anatomy of the adrenal gland and basic function.
Located above each Kidney
Contains two distinct tissues; medulla (inner) and cortex (outer)
Releases hormones in response to stress
Name the medullary hormone of the adrenal gland. What causes its secretion? Describe its function and characteristics.
Epinephrine (adrenaline) release is stimulated by pre-ganglionic sympathetic nerve fibers which innervate the adrenal medulla
It is sympathomimetic to norepinephrine (activates the same receptors in the same manner).
Increases the effects of the sympathetic system (fight/flight) and increases glucose levels in blood
What is epinephrine’s method of action?
Polar hormone (cannot diffuse into cell) requires receptors in the membrane.
Binds to G-Protein-linked receptor in cell membrane
G-Protein sub-unit activates Adenalate Cyclase which produces the second messenger cAMP
cAMP activates various protein kinases which activate/deactivate various enzymes, producing varied effects between cells
Name the corticosteroids. What causes their secretion? Describe their functions and characteristics.
Aldosterone and Cortisol (hydrocortisone) are secreted in response to stress (CRH and ACTH)
Aldosterone [mineralocorticoids] - increases K+ exretion and Na+ retention by kidneys (regulation of blood pressure/K+ homeostasis)
Cortisol [glucocorticoids] - elevates blood glucose, amino acids, and fatty acid levels. Also suppresses inflammation and the immune system
What is Corticosteroid method of action?
Nonpolar hormone (can diffuse into cell)
Binds directly to protein receptors in cytoplasm or nucleus
Receptor binds to gene regulatory proteins in the nucleus, stimulates transcription of that gene (protein expression)
Describe the negative feedback of glucocorticoids.
Thin, biconcave disc-shaped cells (7.5 μm diameter) that lack nuclei and mitochondria and contain many molecules of hemoglobin
Transport respiratory gases (mainly O2) on hemoglobin
What is erythropoesis? Where does it occur? What stimulates it? How much per day?
Erythrocyte production occurs in myeloid tissue (bone marrow) and creates ~200 billion RBCs per day
Stimulated by Erythropoetin (a hormone) secreted by the kidneys in response to decreasing O2 concentration in blood
What is the “life expectancy” of RBCs? Why? Where does their “demise” occur?
RBCs last only 120 days after release into the blood stream due to their lack of nuclei and mitochondria
Old cells are engulfed by phagocytic cells in the spleen, liver, and bone marrow
Describe hemoglobin structure, its properties, and its related disorders.
A protein made of 4 heme subunits (quaternary structure), it contains iron and reversibly binds O2 and CO2
Hemoglobin changes color when bound to O2 (bound = bright red, unbound = dark maroon)
Cyanosis (light blue/grey lips and finger nails) is a result of inadequate O2 levels
Anemia is an inadequate RBC count in the blood (or amount of hemoglobin)
Describe leukocyte functions, and list the leukocytes by category.
Immunity: defense against harmful foreign invaders or abnormal cells
Functions: destroy pathogens (bacteria, viruses, protozoans, and worms), destroy cancer cells, remove dead/injured cells (wound healing)
Granular: neutrophils, eosinophils, basophils
Agranular: lymphocytes, monocytes
Leuokcyte descriptions and functions in detail.
Neutrophils: Show very little stain. Phagoctyes (devour pathogens and dead cells), are able to leave blood vessels and enter CT
Eosinophils: Show pink/orange under stain. Attacks parasites
Basophils: Show dark stains that obscure nucleus. Produce histamine, promoting allergic reactions
Lymphoctyes: part of the lymphatic system, functions in immune responses
Monocytes: Circulating phagocytes, differentiate into “wandering macrophages” in tissues outside of blood
Describe platelet origins, details, and functions.
Platelets are cell fragments from megakaryocytes in bone marrow
Last 5-9 days in circulation
Important in forming clots to stop bleeding when blood vessels are damaged (platelets attach to collagen and form a platelet plug, fibrin is formed (from fibrinogen) to reinforce the clot)
Describe blood typing (basic)
Cells have markers on their surfaces that identify them as part of your body, foreign markers act as antigens and evoke an immunological defense mechanism)
Erythrocytes have relatively few markers (ABO blood types and Rh factor (antigen))
Describe the heart (very generally)
A hollow, muscular organ located in the center of the thoracic cavity (mediastinum) which pumps constantly (at variable rates).
Describe the two blood circuits (very generally) and their functions.
Pulmonary circuit: heart (right) -> lungs -> heart (left). Exchanges gas with the atmosphere (releases CO2, picks up O2)
Systemic circuit: heart (left) -> organs -> heart (right). Exchanges gas with body tissues (releases O2, picks up CO2)
Describe the chambers of the heart and their basic functions.
4 chambers: L/R atria receive blood from veins, L/R ventricles pump blood into arteries
Describe the interventricular septum, its function, and differences between the two sides it creates
The interventricular septum divides the heart into 2 parallel pumps with different chemistries and different pressures
The right side pumps deoxygenated blood at low pressure (low resistance)
The left side pumps oxygenated blood at high pressure (high resistance)
The flow between sides remains equal (flow = pressure / resistance)
Describe the two different types of valves found in the heart, their locations, names, functions and structures
Atrioventricular valves [right (tricuspid) and left (bicuspid / mitral)] allow blood to flow from the atrium to the ventricle ONLY (1 way valve). Chordae tendinae attached to papillary muscles prevents valves from everting during ventricular contraction.
Semilunar valves [pulmonary (left) and aortic (right)] are located at the openings of the arteries that leave the ventricles and prevent blackflow of blood during ventricular relaxations.
Describe the flow of blood through the heart (in depth, separated by circuit).
Pulmonary circuit: Deoxygenated blood enters the right atrium from the vena cava -> right AV valve -> right ventricle -> pulmonary semilunar valve -> pulmonary trunk and arteries -> lungs -> pulmonary veins
Systemic circuit: Oxygenated blood enters left atrium through pulmonary veins -> left AV valve -> left ventricle -> aortic semilunar valve -> aorta -> tissues -> veins
Describe the cardiac cycle and list its phases (no description).
The contraction (systole) and relaxation (diastole) of the heart’s ventricles (simultaneous)
1. Isovolumetric contraction [systole]
2. Ejection [systole]
3. Isovolumetric relaxation [diastole]
4. Rapid filling [diastole]
5. Atrial contraction [diastole]
Describe isovolumetric contraction.
[systole] beginning of ventricle contraction, no blood ejected
semilunar valves closed for the duration
when ventricle pressure rises above atrial pressure (~0 mmHg) AV valves shut
Describe ejection in cardiac cycle.
[systole] blood flows out of ventricles into arteries
Pressure in ventricles exceeds pressure in arteries, semilunar valve opens
blood flows into arteries, causing ventricular pressure to fall
AV valve closed for the duration
pressure forces the semilunar valves open and blood is ejected from the ventricle
Describe isovolumetric relaxation in cardiac cycle.
[diastole] beginning of ventricle relaxation, no blood ejected/filled
Pressure in ventricle drops below arterial pressure, semilunar valve closes (prevents backflow of blood)
No change in ventricular volume
AV valve closed for duration
Describe rapid filling in cardiac cycle.
[diastole] blood flows out of atrium into ventricle
Pressure in ventricles falls below atrial pressure, AV valve opens
Blood flows from atrium into ventricles
Semilunar valve closed for duration
Describe atrial contraction in cardiac cycle.
[diastole] – small atrial contraction before ventricle contraction
Small atrial contraction pushes final amount of blood into ventricles just prior to ventricle contraction (creates EDV)
Approximate amount of time for diastole and systole in cardiac cycle
What is EDV?
End diastolic volume – the amount of blood in the ventricles at the end of diastole (nearly full)
What is ESV?
End systolic volume – the amount of blood in the ventricles at the end of systole (nearly empty)
What is SV?
Stroke volume – the amount of blood ejected by the ventricles (EDV – ESV)
Describe the sounds of the heart, and what causes them.
Lub (first sound) – closing of the AV valves at the start of systole
Dub (second sound) – closing of the semilunar valves at the start of diastole
Describe the structures involved in cardiac excitation, their location, and their function.
Sinoatrial (SA) node (right atrium near superior vena cava) – pacemaker of the heart, site where APs are first generated
Atrioventricular (AV) node (bottom/middle right atrium to interventricular septum) – delays conduction to ventricles
Atriolventricular bundle (bundle of His) (interventricular septum, splits into two) – conducts signals through the interventricular septum
Purkinje fibers (middle apex of heart up sides of heart) – conducts signals up lateral walls of ventricle
Describe the path of cardiac excitation
SA node cells undergo spontaneous pacemaker potentials which creates APs
APs conducted through the atrial network
Atrial fibers activated (atrial contraction)
APs excite AV node which delays AP (allows completion of atrial contraction)
APs of AV node travel down AV bundle to apex of heart
Signals conducted to Purkinje fibers throughout ventricle (ventricular contraction)
Contraction from Apex upward to accommodate “pumping” to ateries located at top of heart
What are pacemaker cells? How do they generate APs?
Modified cardiac muscle cells that spontaneously produce pacemaker potentials
Pacemaker potentials are spontaneous depolarizations during diastole that lead to the APs for contraction. They begin again almost immediately after pacemaker cell repolarization.
When does the myocardial AP occur? How does it differ from a neural AP? Describe it.
The myocardial AP is triggered when myocardial cells receive the AP originally generated by the SA node
Myocardial APs have a prolonged duration when compared to the neural “spike” AP, and have involvement of 3 V-gated ion channels rather than just 2.
Na VG channels are opened to begin AP, Na+ flows in causing depolarization
The 200-300msec plateu phase is caused by a slow Ca2+ influx which combats the slow K+ output from K+ leak channels
Repolarization occurs by the delayed opening of VG K+ channels (and closing of Ca2+)
The prolonged refractory period ensures a pumping action without the possibility of summation (allows relaxation)
What is an ECG? What does it measure?
Electrocardiogram – recording electrodes on extremities allow a recording of the electrical activity of the heart (not contraction)
What are the various “waves” of an ECG? describe them.
P wave (initial hill) – depolarization in atria just before contraction
QRS complex (small valley, large spike, deeper valley) – depolarization of ventricles just before contraction (beginning of systole), also includes atrial repolarization (not shown on ECG)
T wave (final hill followed by nothing until next P wave) – repolarization of ventricles (beginning of diastole)
What measurements can be taken with an ECG, how can they be used?
Waveform shapes, time intervals, segments,etc can be used to diagnose cardiac pathologies
Name various arrhythmias and give details about them
Bradycardia – abnormally slow heartbeat (<60bpm)
Tachycardia – abnormally fast heartbeat (>100bpm)
Flutter – extremely rapid, but coordinate heartbeat (200-300bpm)
Fibrillation – different cells product APs and contract and different times (uncoordinated pumping). Defibrillator shocks the heart, putting the entire myocardium into a refractory period (“resetting” the heart)
What are blood vessels? Describe the different types in order of blood flow.