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Flashcards in Biology 3 Deck (57):

The kidneys (Excretory system)

Excrete liquid and solute waste (excess water, salt, nitrogenous waste)
Maintain pH
Osmolarity and blood pressure



Fenestrated capillary bed that strains the blood, allowing fluids, ions, and molecules the approximate size of glucose ofsmaller to pass through into Bowman’s capsule. 
Blood cells and larger blood components remain within the capillaries and exit via the efferent 
arteriole which eventually empties into the renal vein.


Bowman's Capsule

Spherical enclosure that captures filtrate and funnels it to the proximal convoluted tubule


Proximal convoluted tubule (PCT)

Section of the nephron between Bowman’s capsule and the descending limb of the Loop of Henle. Along the PCT sodium is reabsorbed via active transport and glucose is reabsorbed via secondary active transport 
through a symporter identical to the one used to absorb glucose from the small intestine. Water 
follows the solutes via facilitated diffusion. However, because water and solutes are reabsorbed 
in the same ratio, the filtrate remains isotonic (i.e., the volume of filtrate decreases, but its 
concentration remains constant).


Descending loop of Henle

Travels into the very hypertonic medulla. Impermeable to salts, but very permeable to water. Water flows out of the filtrate, concentrating the urine.


Ascending loop of henle

Carries filtrate out of the medulla and into the cortex. This portion of the loop is impermeable to water and actively transports ions out of the filtrate and into the medulla. This continuous dumping of salts into medulla account for its hypertonicity. At the top, filtrate is less concentrated due to the removal of ions.


Distal convoluted tubule (DCT)

Section of nephron between ascending loop and collecting duct. Passes directly by the opening of Bowman's capsule where the juxtaglomerular apparatus is located.
The DCT regulates calcium, hydrogen, and sodium concentrations (focus on sodium reabsorption regulated by aldosterone)
Reabsorbs calcium as a response to parathyroid hormone.


Juxtaglomerular apparatus

Detects decreased blood pressure in the afferent arteriole, it secretes Renin, setting into motion the renin-angiotensin pathway, which increases blood volume and blood pressure (negative feedback).


Collecting duct

Carries filtrate through medulla towards renal pelvis. Becomes very permeable to water in response to ADH


Respiratory System

Gas exchange. Oxygen diffuses down its concentration gradient into the blood, and CO2 diffuses down its concentration gradient out of the blood and back into the lungs.


Tidal volume

Volume of air that enters and exits the lungs during an average, unforced respiration.


Inspiratory reserve volume (IRV) and Expiratory reserve volume (ERV)

Volume of additional air that can be exhaled or inhaled after a normal, unforced expiration or inhalation.


Residual volume

Amount of air left in the lungs after a forced, maximal exhalation.


Vital capacity

Total amount of air the lungs can hold at maximum inflation, MINUS residual volume



Moves DOWN when it is FLEXED, moves UP when it is RELAXED.
Moves DOWN during inhalation, moves UP during exhalation.



Quarternary protein made of four protein chains, two alpha and two beta. Each protein has an Fe-containing "heme" group at its center, which can hold one O2 molecule.


Oxygen dissociation curves:
% Hb Saturation vs pO2

Right Shift: Increased [H+], [CO2], temp, or BPG
Left Shift: Decreased [H+], [CO2], temp, or BPG


How CO2 is carried in the blood

CO2 + H2O --> HCO3- + H+


Cardiovascular system

Deliver oxygen and nutrients to the cells and tissues of body.


Electrical System of the Heart

Electrical signal originates from the SA node (sinoatrial node), then spreads across both atria to the AV node (atrioventricular), there is a pause for the ventricles to fill, then from the AV node it travels down the bundle of His, then up through the Purnkinje fibers.


Sympathetic and Parasympathetic effect on heart rate and blood pressure

Sympathetic activity INCREASES HR AND BP
Parasympathetic activity DECREASES HR AND BP



Transport nutrients, gases, waste products and hormones to and from cells; regulate extracellular environment, help maintain homeostasis; repair injuries, protect the body from foreign bodies (antigens).
All blood cells develop from stem cells in the bone marrow, process called HEMATOPOIESIS.


Contents of blood

White blood cells (leukocytes)
Red blood cells (erythrocytes)
Antibodies (immunoglobulins)
Clotting factors (like fibrinogen)
Transport proteins (like albumin)



No Hb. Normal cells with organelles
Two types:
Granulocytes: neutrophils, eosinophils, and basophils. LIVE HOURS TO DAYS
Agranulocytes: monocytes (become macrophages) and lymphocytes. LIVE FOR MONTHS TO YEARS.



Tiny membrane bound drops of cytoplasm. Sticky when exposed to injured epithilium and non-sticky to healthy epithilium. Release chemicals that activate other platelets and clotting factors. Derived from MEGAKARYOCYTES, a cell that remains in the bone marrow. Megakaryocytes produce and release small fragments into the circulating blood (fragments are the platelets).


Blood typing

A, B, AB, and O
A= A antigens only
B= B antigens only
AB= Both A and B antigens
O= neither A or B antigents


For MCAT questions on blood typing

ALWAYS FOCUS ON THE RECIPIENT. If a person's immune system sees any protein it does not have on its own blood cell membranes, it will attack it and rejection will result. O can be donated to anyone because it has no A or B antigens. AB person can receive from anyone because no donor will have any antigens this person's immune system hasn't seen previously.


Lymphatic System

Gather excess interstitial fluid and return it to the blood; remove from the interstitial spaces proteins and other molecules too big to be taken up by the capillaries; monitor the blood and lymph for infection.


Lymph Nodes

Filled with lymphocytes. These immune system cells monitor the blood for foreign antigens and fight infections.


Lymph Vessels

A lot like veins. Many, but not all, contain one-way valves used to move the lymph; single cells overlap slightly creating a trap door that allows things in, but not back out. Entire lymph system eventually drains into TWO MAIN VESSELS, the RIGHT LYMPHATIC DUCT and the THORACIC DUCT, which both dump back into the blood stream by merging with the large veins in the lower portion of the neck.


Nervous System

Includes the brain, spinal chord, peripheral nerves, neural support cells, and sensory organs such as the eyes and ears.



Specialized cell that can carry an electrochemical signal (Action potential)
1)Frozen in G0 phase (unable to divide)
2) Depend ENTIRELY on glucose for energy
3) Don't require insulin for glucose uptake
4) Have very low glycogen & oxygen storage capability and thus require high perfusion (blood flow)


Action Potential

Disturbance in the resting electric potential (voltage) across the membrane of a nerve cell. Once it is created, it will propagate along the cell membrane to neighboring portions of the neurons. As it does, the areas where it originally started gradually return to the normal resting potential.


Resting Potential

-70 mV. This is the potential difference across the membrane when an action potential is NOT present.


Sodium/Potassium Pump

An ATP pump that actively transports 3 Na+ ions OUT of the cell and 2 K+ ions INTO the cell per cycle. The net effect is more positive charge outside the cell and a progressively more negative charge inside the cell.


Voltage Gated Sodium Channels

Integral proteins that change shape (open) in response to a disturbance in the resting potential (voltage) across the membrane. In their "open" state, they allow the RAPID FLOW OF SODIUM BACK INTO THE CELL.



The opening of a voltage gated sodium channel causes a sudden spike in the membrane potential, from -70 mv to around +40 mv. This is called "depolarization"


Threshold potential

This is the minimum stimulus that must be exerted upon the membrane to initiate a full action potential. It is usually somewhere around -55 mv. If a stimulus depolarizes the membrane above this threshold, the entire action potential will follow. If not, the membrane potential will return to -70 mV.


Voltage-gated Potassium Channels

Also integral proteins that respond to a change in the membrane potential. However, their threshold for responding is MUCH HIGHER than that for the voltage-gated sodium channels. They only react following the very large change in the membrane potential caused by depolarization. JUST BEFORE DEPOLARIZATION IS REACHED, THE NA+ CHANNELS BEGIN TO CLOSE AND THE K+ CHANNELS BEGIN TO OPEN.



Opening the potassium channels causes K+ ions to flow out of the cell due to the Na+/K+ pump. This results in a sudden DECREASE in membrane potential from +40 mV back down to -70 mV; referred to as "repolarization"



K+ channels are somewhat slow to close as the membrane potential approaches -70 mV. Thus, the membrane potential actually dips to around -90 mV before going back to -70 mV.


Absolute Refractory Period

Portion of time during which an action potential cannot be initiated regardless of the strength of the stimulus. This time period occurs during the progression of the previous action potential. The progression of an action potential involves the depolarization of the membrane and a second stimulus cannot be initiated until the membrane is repolarized.


Relative Refractory Period

Portion of time during which the membrane is hyperpolarized. Second potential CAN be initiated, but a STRONGER THAN NORMAL stimulus will be required. This is because there is a greater voltage difference from -90 mV to -55 mV.



Two types: Electrical synapses and chemical synapses


Electrical Synapses

Gap junctions between cells that allow electrical signals to pass very quickly from cell to cell. In humans, only in specific locations: retina, smooth muscle, cardiac muscle, and CNS


Chemical Synapses

Small gap between terminal button and either
1) the dendrite of a subsequent neuron or 2) the membrane of a muscle or other target ("effector")


Signal transmission in synapse

1) Action potential arrives at the presynaptic membrane
2) Triggers opening of voltage-gated calcium channels, calcium enters the cell.
3) Neurotransmitter bundles inside cell, in response to calcium, fuse to presynaptic membrane and dump contents into the synaptic cleft.
4) Neurotransmitters diffuse through the gap and bind to protein receptors on the postsynaptic membrane.
5) Receptors associated with voltage-gated sodium channels so that neurotransmitter binding opens the channels.
6) If enough sodiums enter, threshold will be met and new action potential will generate.


Stopping the Signal

Post-synaptic membrane will be continuously stimulated as long as neurotransmitter present. Specialized enzymes in the synaptic cleft must break down the NT to interrupt this action. ACETYLCHOLINESTERASE.
Agonist: another term for activator


Neural Support Cells

Schwann cells (oligodendricytes in the CNS), cells lining the cerebrospinal fluid cavities (ependymal cells) and structural support cells (astrocytes)


The Eye

Rods= highly sensitive, perceive black and white only
Cones = less sensitive, perceive color


Endocrine System

Includes "endocrine glands" and the fluids and ducts into which they are released.
Endocrine glands release HORMONES into the INTERNAL FLUIDS OF THE BODY (blood, lymph)


Peptide Hormones (water soluble)

Anterior Pituitary: FSH, LH, ACTH, hGh, TSH & Prolactin
Posterior Pituitary: ADH & Oxytocin
- (AP & PP are both regulated by "____ stimulating/releasing" hormones from the hypothalamus
Parathyroid: PTH
Pancreas: insulin & glucagon (also an exocrine gland)
Thyroid: Calcitonin
Embryo/placenta: hCG (Human Chorionic Gonadotropin)


Steroid Hormones (lipid-soluble, ALL STEROIDS ARE CHOLESTEROL DERIVATES)

Adrenal Cortex: Cortisol & Aldosterone
Gonads: Estrogen, progesterone, testosterone


Tyrosine Hormones (T3/T4 = lipid soluble; epi/norepi= water soluble)

Thyroid: T3 (Triiodothyronine) & T4 (thyroxine)
Adrenal medulla: Epinephrine & norepinephrine


Transport of hormones

Lipid-soluble require a protein carrier or a micelle/vesicle
Peptire hormones are water soluble and dissolve in the blood readily



Lipid-soluble hormones act almost exclusively by binding to a receptor on or inside the nucleus and act as TRANSCRIPTION FACTORS.
Peptide hormones act at a variety of cell locations


Membrane Permeability

Lipid soluble hormones diffuse easily through lipid center of the membrane, DON'T require a cell membrane receptor (eventually will bind to receptor inside cell).
Peptire hormones are hydrophilic and can't dissolve through the membrane, require membrane receptor.