Bio Class 8 - Endocrine, Cardiovascular, Immunology

What are characteristics of endocrine glands?

Make hormones

Release into bloodstream

No duct needed

What are characteristics of exocrine glands?

Products: enzymes, bile, stomach acid, bicarbonate, saliva, tears, sebum, earwax, mucus, breastmilk, semen, etc.

Release outside the body or inside a body cavity

Requires ducts to get the product where it needs to be (except mucus cells)

What are they made of, receptors located, mechanism of action, speed of effects, and longevity of effects? Peptide hormones

Made from: amino acids

Receptors: cell surface

MoA: 2nd messenger systems

Speed: quick

Longevity: temporary

What are they made of, receptors located, mechanism of action, speed of effects, and longevity of effects? Steroid hormones

Made: derived from cholesterol

Receptors: intracellularly in cytoplasm or nucleus

MoA: binds to DNA, modifies transcription

Speed: slow

Longevity: more permanent

What is thyroid hormone?

Made of amino acids, but is hydrophobic enough to cross cell membranes

Looks like peptide hormone, acts like steroid hormone

How is hormone release controlled? 3

Neural, hormonal, humoral

How are hormones controlled neurally?

Action potential triggers release of hormone

Ex: sympathetic nervous system triggers release of epinephrine

How are hormones controlled hormonally?

Hormone triggers release of another

Tropic hormones do this

Ex: adrenocorticotropic hormone triggers release of hormones from adrenal cortex

How are hormones controlled humorally?

Something in blood that is not a hormone triggers hormone release

Ex: glucose regulates insulin and glucagon, calcium regulates parathyroid hormone and calcitonin

What is the pituitary gland?

Controlled by hypothalamus and sits below it

Anterior (adenohypophysis) and posterior (neurohypophysis)

What does the anterior pituitary do?

Gland tissue that makes 6 hormones

FLAT PiG (FLAT are all tropic)

FSH, LH, ACTH, TSH, prolactin, growth hormone

Controlled hormonally by hypothalamus: all by releasing hormones (aka ___RH), except prolactin (by prolactin inhibitory hormone aka prolactin IH)

What does the posterior pituitary do?

Neural tissue

Stores and secretes 2 hypothalamic hormones

Oxytocin and ADH (antidiuretic hormone aka vasopresin)

Controlled neurally by hypothalamus

How is the hypothalamus controlled?

Neurally and humorally

What is the anatomy of the posterior pituitary?

Neurons with cell body in the hypothalamus project down into it

These make and release the hormones and transport them down the axon

Released into capillary bed → bloodstream

What is the anatomy of the anterior pituitary?

Hormone making cells line capillaries → veins connect these capillaries to the capillaries in the hypothalamus (that are also lined by hormone making cells)

Called a portal system (connected by hypothalamic/hypophyseal portal veins)

How do portal systems work?

Hormone released in hypothalamus (ex: growth hormone releasing hormone) → travels to anterior pituitary → stimulates cells in anterior pituitary (ex: release growth hormone) → hormone (ex: growth) goes to body

Double negative feedback

Allow extremely targeted delivery

What is the liver portal system?

Liver capillaries connetc to intestinal capillaries via portal veins

What is the circulatory system? Basic parts of the

Loop

Artery: blood away from heart

Capillaries: site of nutrient exchange

Vein: blood towards heart

Heart: pump that controls all this

How do arteries function?

High pressure system

Blood moves via forward momentum (from high pressure at heart to low pressure in capillaries)

Muscular walls (regulate flow and diameter)

Elastic (can snap back to shape after stretching)

How do capillaries function?

Very large surface area

Relatively low pressure

Do nutrient/waste exchange

Fluid out due to pressure near the arteries → blood in due to osmosis near the veins → net outward flow of blood → must recover this via lymphatic system

How do veins function?

Low pressure

Blood moves when veins are squished (normal body movement)

Valves ensure unidirectional flow

Not muscular and not elastic

What does the lymphatic system do?

Structurally like vein (valves, non muscular, non elastic)

Pick up fluid from capillaries and returns it to veins (filters through lymph nodes)

What are lymph nodes?

Concentrated areas of white blood cells

How does blood flow in the heart?

Blood from body superior vena cava → right atrium → contracts → right ventricle → contracts → pulmonary artery to lungs → pulmonary vein to left atrium → contract → left ventricle → contract → to body via aorta

Left ventricle is thicker walled

What drives blood flow?

Pressure gradient

Once pressure is greater than arterial pressure → blood flow to arteries

Valves prevent backflow between chambers/between arteries and ventricles

Blood passively drains into atrial until ventricle pressure is lower → goes to ventricles

What are atrioventricular valves?

Tricuspid AV valve: between right atrium and ventricle

Bicuspid (mitral) AV valve: between left atrium and ventricle

What are semilunar valves?

Pulmonary semilunar: between right ventricle and pulmonary artery

Aortic semilunar: between left ventricle and aorta

What do systole and diastole mean?

Systole: heart contracted

Diastole: heart relaxed

Usually talking about ventricles → MCAT will specify atrial if it wants that

What do the heart sounds mean?

Lub: closing of AV valves, begins systole

Dub: closing of semilunar valves, begins diastole

What is blood pressure?

120/80, 115/70

Systolic/diastolic

Arterial pressure when heart is contracted/when relaxed

What is blood pressure directly proportional to?

Cardiac output and peripheral resistance

What is cardiac output?

Volume of blood pumped per minute

Stroke volume (volume pumped per beat ) x heart rate (beats per minute)

What is the FS Law of Heart?

More blood in heart → muscles stretch → contract back with greater force → more blood out

Within parameters

What happens in congestive heart failure?

Heart is so stretched out, the muscle fibers no longer overlap → cannot pump effectively

How do you change stroke volume?

Change blood volume (ex: drunk water, ingest salt, donate blood, etc.; renal system regulates this primarily)

Change activity level (moving increases blood to heart)

Change posture (gravity makes less blood reach heart for a second after you stand)

What is peripheral resistance?

How hard it is to move blood through vessels

Vessels constrict → decrease in diameter → decrease in flow → increased resistance → increased blood pressure

Vessels dilate → increase diameter → increase flow → decrease resistance → decreased blood pressure

How do cardiac muscles reach action potential?

Connected via gap junctions

Rest at -80 mV → reaches threshold once its neighbor does → voltage gated Na⁺ channels open → inactivate at +40 mV → voltage gated K⁺ channels open → voltage gated Ca²⁺ channels open → action potential plateaus → Ca²⁺ channels close → hyperpolarization → K⁺ channels close → back to rest

200-300 milliseconds from threshold to rest (100x longer than nerve action potentials)

Prevents tetanic contractions (sustained contractions) because it is impossible to increase the frequency of action potentials enough for this

What are skeletal muscle action potentials like?

20-30 milliseconds

Each action potential triggers a twitch → add a bunch of them → tetanic contraction (sustained)

What are cardiac autorhythmic cells?

Initial cells that start cardiac contractionsW

hat is the action potential like for cardiac autorhythmic cells?

Rest at -40 mV → constantly drifting upward due to sodium leak channels → reach threshold → slow voltage gated Ca²⁺ channels → cause slow influx of calcium up to 20 mV → depolarizes → rises up again thanks to sodium leak channels

When it hits thresholds, it fires action potentials

These are connected to other cardiac cells → trigger action potentials in them

What is the cardiac conduction system?

Cardiac autorhythmic cells

SA (sinoatrial) node: leakiest to sodium, is first to reach action potential → controls pace of contractions

AV (atrioventricular) node → branches into left and right bundle branches → form Purkinje fibers

What is the pacemaker of the heart?

SA node

Has a resting rate of 100 beats per minute → brought to ~70 by parasympathetic nervous system

~70 is parasympathetic tone (aka vagal tone)

Epinephrine will increase the beats per minute past 100

Where are heart muscle cells connected to autorhythmic cells?

SA node connects to right atrium → left connected at end of fibers that project from it

Purkinje fibers connect to ventricles

To the muscle cells, this signals contraction

What is the impulse pathway through the heart?

SA node in right atrium → left atrium → AV node → right and left bundle branches → Purkinje fibers

Atria contract downward and ventricles contract upward

Why does the heart conduction system run like it does?

Atria and ventricular muscle cells not electrically connected (valves separate them): atria cause ventricles to contract

AV node delays impulse, allowing atria to contract before ventricles do

Ventricles contract from bottom to top, pushing blood out through the aorta (attached at top of ventricles) → more efficient ejection

What are the three components of blood?

54% plasma: anything hydrophilic dissolved in blood

1% (variable depending on gender, if you are sick, age, weight) leukocytes: white blood cells and platelets

45% (variable, see above) hematocrit: red blood cells

How do oxygen and carbon dioxide travel through the blood?

Oxygen: 3% dissolved in plasma, 97% bound to hemoglobin

Carbon dioxide: 7% dissolved in plasma, 20% bound to hemoglobin, 73% as bicarbonate

How does oxygen bind to hemoglobin?

Cooperative binding: once one oxygen binds, it is easier for the others to

Released when the [oxygen] is released

How is CO₂ carried as bicarbonate?

CO₂ + H₂O ←→ H₂CO₃ (carbonic acid) ←→ H⁺ + HCO₃^- (bicarbonate)

Tissues always producing CO₂ → shifts equilibrium towards bicarbonate

Lungs are getting rid of CO₂ → shifts equilibrium towards CO₂

Affects blood pH

What are three categories of non-specific immune defense?

Barriers

Chemicals

Cells

What type of immune barriers do you have?

Skin, mucus, hair, earwax, etc.

What are chemicals for immune defense?

Mucus, lysozyme (saliva, tears), stomach acid, enzymes, complement system, etc.

What are general immune defense cells?

Macrophages, neutrophils, eosinophils, dendritic cells, basophils, etc.

What is an antigen?

Foreign protein that triggers an immune response

What are antibodies?

Highly-specific marker that binds to an antigen

What are pathogens?

Disease-causing organisms

What are the two types of specific immunity?

B cell “humoral” immunity

T cell “cell mediated” immunity

What is characteristic of B cell immunity?

B cells produce and secrete antibodies

Each B cell makes one type of antibody

Diversity generated via DNA rearrangement of genes that produce antibodies

Occurs in the bloodstream

What are antigen receptors?

Displayed on the surface of B cells

Bind to the antigen that B cell creates antibodies for → pulls it in → creates a bunch of antibodies to that antigen → cell clones itself so there is a greater response

What are types of T-cells? What does each do?

Killer T: bind to and kill own cells that have become abnormal

Helper T: secrete cytokines that allow B cells and killer T cells to proliferate

How do killer T cells work?

Has antigen and “self” receptors → bind to antigens displayed by MHC I

Self receptor allows it to identify cells that originate from the host

Both self and antigen receptors must be bound to create a response

What is MHC I?

Found on all cells

Allows cells to display cell contents on the cell surface → allows killer T cells to identify abnormal ones

How do helper T cells work?

Look for antigens displayed on MHC II

What is MHC II?

Found on macrophages and B cells

Allows cells to display stuff they have “eaten” on the cell surface

What is the primary immune response?

1^st exposure to antigen → 7-10 days → antibodies generated and T cells activated → memory cells produced

Takes a super long time, relative to the viral lifecycle

What are memory cells?

Remember an antigen of a previous infection → allows faster response next time

Allows for long-term immunity

What is the secondary immune response?

2^nd exposure → make antibodies, activate T cells, make more memory cells

Existing memory cells allow this to happen in <1 day

How do vaccines work?

Inject antigens of whatever you want immunity against → body produces antibodies, activates T cells, makes memory cells in 7-10 days

No active infection

Memory cells can now respond quickly if you are exposed to the actual infection

Boosters allow for stronger, faster responses

What is autoimmunity?

Body produces B and T cells that recognize a large number of antigens, including self-antigens → self reactive lymphocytes will attack our own antigens and cause autoimmune diseases

We must have a way to identify self-reactive lymphocytes and inactivate/destroy them

How are self-reactive lymphocytes inactivated/destroyed?

By B cells in the bone marrow and T cells in the thymus

B cells recognize soluble proteins → become anergic (inactive)

T cells recognize cell-surface proteins → apoptosis

Making them anergic/apoptosing them occurs only in the bone marrow and thymus

If the B and T cells do not recognize self things → released into circulation