Study Guide

Action Potential Lab

• Definitions:

  • Permeability: The state or quality of a material that allows liquids or gases to pass through it.

  • Conductance: The degree to which an object conducts electricity, calculated as the ratio of the current which flows to the potential difference present. In cells, it's the ability of charge (carried by ions) to cross the membrane.

  • Membrane potential: The voltage or difference in electrical potential across the cell membrane.

  • Action potential: A short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls, following a consistent trajectory.

  • Equilibrium potential: The membrane potential at which there is no net (overall) flow of a specific ion across the cell membrane.

  • Driving force: The net force acting on an ion that dictates its movement across a membrane, combining the concentration gradient and electrical gradient.

  • Current: The flow of electrical charge.

  • Voltage: The difference in electrical potential between two points.

• Concentration Gradients (Na+ and K+): Higher concentration of Na+ outside the cell and K+ inside the cell. These gradients are created by the sodium-potassium pump, which actively transports Na+ out and K+ into the cell.

• Ionic Basis of Membrane Potential: Primarily due to the constant leaking of K+ across the cell membrane from inside to outside. This outward movement of positive charge makes the inside of the cell negative. The sodium-potassium pump contributes slightly.

• Ionic Basis of Action Potential:

  • An initial stimulus raises the membrane potential, opening voltage-gated Na+ channels. This allows Na+ to diffuse into the cell, causing rapid depolarization.

  • Voltage-gated K+ channels open (with a slight delay), allowing K+ to rush out of the cell. This returns the membrane potential to a negative value (repolarization).

• Nernst and Goldman Equations:

  • Nernst Equation: Calculates the equilibrium potential for a single ion, considering its concentration gradient and charge.

  • Goldman Equation: Calculates the membrane potential by taking into account the permeability and concentration of multiple ions (Na+, K+, and sometimes Cl-).

• Ion Permeability: An ion's contribution to the resting membrane potential depends on its permeability across the membrane (i.e., open channels). If channels are closed, permeability is low, and the ion's impact is minimal.

• Temperature Effects: Increased temperature generally speeds up molecular activity, which can cause the action potential to occur faster. Colder temperatures slow ion channel movements, reducing conduction velocity.

• Drug Treatments:

  • TTX (Tetrodotoxin): Blocks sodium channels, preventing depolarization and action potential generation.

Blood Lab

• Definitions:

  • Hematocrit: The ratio of erythrocyte (red blood cell) volume to the total blood volume, expressed as a percentage.

  • Plasma: The liquid component of blood, in which the blood cells are suspended. It consists mostly of water, with dissolved proteins, glucose, ions, clotting factors, etc.

  • Erythrocyte: Red blood cell, which transports oxygen.

  • Leukocyte: White blood cell, which is involved in immune responses.

  • Thrombocyte: Platelet, which is involved in blood clotting.

  • Coagulation: Blood clotting, which requires the interaction of many clotting factors.

  • Anemia: A decrease in the number of red blood cells or hemoglobin in the blood.

  • Polycythemia: An increase in the number of red blood cells.

  • Hemoglobin: The protein in red blood cells that carries oxygen.

  • Antigen: A substance that can trigger an immune response.

  • Megakaryocyte: A large bone marrow cell that produces platelets.

  • Platelet plug: An accumulation of platelets that helps stop bleeding.

  • Leukocytosis: An increase in the number of leukocytes.

  • Leukopenia: A decrease in the number of leukocytes.

  • Phagocyte: A cell that engulfs and destroys microorganisms, other cells, and foreign particles.

  • Macrophage: A type of phagocyte that is important in chronic infections.

• Test Results: The lab involves tests such as the differential white blood cell count, hematocrit determination, coagulation time measurement, and blood typing.

• Formed Elements of Blood: Erythrocytes, leukocytes, and thrombocytes (platelets).

• Function of Formed Elements:

  • Erythrocytes: Transport oxygen.

  • Leukocytes: Mediate immune responses; examples include neutrophils (protection against bacterial disease), eosinophils (protection against parasites), basophils (inflammatory/allergic responses), lymphocytes (adaptive immune response), and monocytes (become macrophages).

  • Thrombocytes: Form platelet plugs and contribute to blood coagulation.

• Blood-Typing Test: Determines ABO blood type and Rh factor based on the presence or absence of specific antigens on red blood cells.

• Blood Donation: Blood can be safely donated as long as the donor does not possess any cell-membrane antigens that the recipient does not have.

• Hematocrit: Determined by centrifuging blood and measuring the percentage of red blood cell volume. Normal hematocrit values are 42 +/- 5% for women and 47 +/- 5% for men.

• Clotting Time: Measured by observing the time it takes for blood to clot in a capillary tube. Normal range is 2 to 6 minutes.

Earthworm Action Potential Lab

• Definitions:

  • Conduction velocity: The speed at which an action potential propagates along an axon.

  • Dorsal/ventral: Dorsal refers to the back or upper surface, while ventral refers to the stomach side or lower surface.

  • Anterior/posterior: Anterior refers to the front end, while posterior refers to the tail end.

  • Proximal/distal: Proximal refers to closer to the point of attachment or origin, while distal refers to farther away from the point of attachment or origin.

  • Refractory period: A period after an action potential during which the neuron is less responsive to further stimulation.

  • Action potential: A short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls.

  • Resting membrane potential: The electrical potential difference across the plasma membrane of a cell when it is not active.

  • Temporal summation: The additive effect of multiple stimuli arriving in close succession.

  • Spatial summation: The additive effect of multiple stimuli arriving simultaneously at different locations.

• Earthworm Giant Fiber Structure: Earthworms have giant axons (large diameter) for rapid conduction of action potentials. Each giant axon is formed from many individual neurons whose axons fuse into a single functional unit, but whose cell bodies remain separate.

• Refractory Period: Exists because Na+ channels are inactivated after an action potential, preventing immediate re-excitation.

• Conduction Velocity: Determined by measuring the time it takes for an action potential to travel a known distance along the nerve. Conduction velocity depends on axon diameter and myelination (earthworms lack myelination).

• Temperature Effects: Lower temperatures reduce the rate of nerve impulse transmission, decreasing conduction velocity.

• Stimulus Strength and Duration: A stimulus pulse with a low amplitude and a long duration can stimulate a neuron just as easily as a stimulus pulse with a high amplitude and a short duration.

• Interpret Experimental Results: Correctly interpret and explain the basis of a figure showing experimental results.

Glucose Metabolism Lab

• Definitions:

  • Glycemic load: A measure of how much a particular food raises blood glucose levels, considering both the quantity of carbohydrates and how quickly they are converted to glucose.

  • Hemolymph: The term for all extracellular fluids in animals with open circulatory systems.

  • Fed state/fasted state: Fed state refers to the period after eating when nutrients are being absorbed and used. Fasted state refers to the period when the body relies on stored nutrients.

• Glucagon and Insulin:

  • Insulin: Secreted by the pancreas in response to high blood glucose, it signals cells to take up glucose, lowering blood glucose levels.

  • Glucagon: Secreted by the pancreas in response to low blood glucose, it stimulates the liver to break down glycogen and release glucose into the blood, raising blood glucose levels.

• Hormone Level Changes: An increase in blood glucose leads to increased insulin and decreased glucagon. In a fasted state, glucose levels are low, resulting in decreased insulin and increased glucagon.

• (Human) Glucose Tolerance Lab: The lab investigates how different meals affect blood glucose levels based on their glycemic loads. Meals with high sugar or starch content lead to greater and faster increases in blood glucose.

• Glucose Control: In vertebrates, blood glucose is primarily controlled by insulin and glucagon. In crustaceans, blood glucose is increased by crustacean hyperglycemic hormone (CHH).

• Crayfish Experiment: Aims to measure the effect of stressors on hemolymph glucose levels in crayfish. Stress in crustaceans is expected to cause an increase in blood glucose levels due to the release of crustacean hyperglycemic hormone (CHH).

• Unknown Sugar Concentration: The concentration of an unknown sugar sample can be determined using a spectrophotometer and comparing its absorbance to that of a standard solution of known concentration.

Scaling Lab

• Definitions:

  • Allometry/allometric: The study of how traits change with size. Allometric refers to the change in proportion of anatomical structures or physiological processes with body size.

  • Scaling factor: Exponent describing the relationship between two variables.

• SA:Vol Ratios: Surface area to volume ratios are calculated by dividing the surface area of an object by its volume.

• SA and Volume Relationships: Surface area grows proportional to the square of the change in length or radius (x2), while volume grows as the cube of the change (x3).

• Size and SA:Vol Ratio: Large animals have low surface area to volume ratios, while small animals have high surface area to volume ratios. The rate of heat loss is related to SA:Vol ratio; objects with higher ratios lose heat faster.

• Qualitative Application: The principles can explain why rabbits are bigger in the Arctic than in temperate regions.

• Quantitative Application: The formula Y = aXb can be used to solve quantitative allometry problems.

• Log-Log Paper: Log-log paper is used to plot allometric equations because it converts power functions into linear relationships.

• Allometric Equation: Plotted data on log-log paper can be used to determine the allometric equation, which has the form Y = aXb, where a is the y-intercept and b is the slope.

Sensation and Reflexes Lab

• Definitions:

  • Receptive field: The area on the body surface or in the visual field that, when stimulated, affects the firing of a sensory neuron.

  • Sensory adaptation: The process by which sensory receptors become less responsive to a constant stimulus over time.

  • Referred pain: Pain perceived at a location other than the site of the painful stimulus.

  • Myopia: Nearsightedness, where distant objects appear blurred.

  • Hyperopia: Farsightedness, where near objects appear blurred.

  • Astigmatism: A condition where the cornea or lens is irregularly shaped, causing blurred vision.

  • Accommodation (of the lens): The ability of the lens to change shape to focus on objects at different distances.

  • Optic nerve: The nerve that carries visual information from the retina to the brain.

  • Optic disc: The location where the optic nerve exits the eye, creating a blind spot.

  • Presbyopia: Age-related decline in the ability to focus on near objects due to decreased lens elasticity.

  • Conduction deafness: Hearing loss due to problems with the outer or middle ear that prevent sound from reaching the inner ear.

  • Sensorineural deafness: Hearing loss due to damage to the inner ear (cochlea) or the auditory nerve.

  • Presbycusis: Age-related hearing loss, particularly of high-frequency sounds.

• Explain Results Physiologically: The lab involves various tests to demonstrate sensory phenomena, such as receptive fields, sensory adaptation, visual acuity, and reflexes.

• Touch Sensation Precision: Touch sensation is more precise in areas with a higher density of touch receptors and smaller receptive fields (e.g., fingertips, nose).

• Perception of Sensations: Some sensations, like pain, are perceived continuously because the receptors keep firing. Others, like temperature and smell, stop being perceived due to sensory adaptation.

• Blind Spot: The blind spot exists because there are no photoreceptors (rods or cones) at the optic disc where the optic nerve exits the eye.

• After-Images: After-images in complementary colors appear due to photoreceptor adaptation. Prolonged exposure to a color desensitizes the cones responsive to that color, leading to an over-response of the opposing cones when looking at a white surface.

• Sound Localization: Sound is localized using binaural cues, including differences in timing and intensity of sound reaching each ear.

• Reflex and Reaction Time Circuits:

  • Reflex circuits involve fewer neurons and shorter distances, resulting in faster responses.

  • Reaction time circuits involve more neurons, longer distances, and cognitive processing, leading to slower responses. Factors such as neural processing speed, attention, and physical coordination can affect reaction times.