What are the three sensory receptor types?
The three sensory receptor types are chemoreceptors, mechanoreceptors, and photoreceptors.
Explain the organization of chemoreceptors in the nose.
Olfactory chemoreceptors (neurons) have dendrites sticking into the mucus layer. This is where odor molecules bind to generate EPSPs. Chemoreceptors of the same molecule synapse at the same interneuron in the olfactory bulb, which connects to the olfactor
What is sensory transduction and what are three ways it can be initiated?
Sensory transduction converts external stimuli into an electrical impulse. Sensory transduction can be initiated by chemoreceptors, mechanoreceptors, and photoreceptors.
Explain the organization of chemoreceptors in the taste buds.
A taste bud consists of a chemoreceptor with microvilli that collects molecules. With enough taste molecules, a G-protein pathway is activated and opens up Na+ channels for depolarization. This depolarization causes action potentials in the neurons that t
How do we feel something touch our skin?
Mechanoreceptor neurons have dendrites with stretch-gated ion channels and connect the skin to the spinal cord. A disturbance in cell membranes will produce a signal great enough for an action potential.
How do invertebrates and humans differ in how they maintain balance and orientation?
Invertebrates use a statolith that depresses stereocilia bound in a statocyst. We use the vestibular system, which has two otoliths and three semicircular canals. The otoliths use stereocilia to function like a statocyst. The canals have three different p
Explain the steps of detecting, amplifying, and interpreting sound in the human ear.
The outer ear carries sound waves to your tympanic membrane, which relays the vibrations across your middle ear bones and to the cochlea (same structure with vestibular system) via the oval window. The cochlea has two canals separated by a basilar membran
Explain how photoreceptor cells respond to a photon.
Opsin, a light-sensitive GPCR on photoreceptors, alters the molecular structure of their retinal portions in response to light. The altered retinal causes Na+ channels to close and the cell to hyperpolarize. This prevents the release of glutamate (which u
Explain the anatomy of the human eye and how it all works together.
The retina in the back of the eye uses rod cells (light intensity) and cone cells (light wavelengths) to interpret brightness and color, respectively. Each cone cell has one of three opsin types, one for each main color (RBG). The iris expands or contract
Explain the relationships between retina photoreceptor cells, bipolar cells, and ganglion cells.
No light: photoreceptors depolarize and release glutamate (IPSP); bipolar cells remain resting; ganglion cells don't fire action potentials yet
Light present: photoreceptors hyperpolarize as sodium channels close (but Na/K pump is still active), a graded
Of the different sensory receptors, which ones are actual neurons and which ones are just cells that are capable of depolarization?
Nose chemoreceptors: neurons
Taste bud chemoreceptors: cells
Skin mechanoreceptors: neurons
Hair mechanoreceptor cells: cells
Photoreceptors: cells
Explain the relationship between force and work.
Work is equal to the amount of force times the amount of distance traveled in the same direction as the force.
Describe the differences in smooth muscle and striated muscle.
Smooth muscle is found in intestines, your lungs, and your arteries. Smooth muscle does not have a regular repeating pattern of myosin and actin filaments, so they do not appear striated. Striated muscle is found in cardiac and skeletal muscle due to thei
Describe the anatomy of the muscle from the organ itself down to myosin and actin.
Muscles are made up of muscle bundles, which are made up of muscle fibers. Each muscle fiber is made up of myofibrils. A myofibril is a repeating "polymer" of sarcomeres. Sarcomeres are the main unit of muscle contraction, and they are composed of actin a
What are the steps of the cross-bridge cycle?
1. Upon binding to ATP, the myosin head detaches from the actin.
2. Once it hydrolyzes ATP to ADP and inorganic phosphate group, the myosin head now has energy and is cocked back. (This is the resting state of a myosin head)
3. The myosin then binds to ac
In skeletal and cardiac striated muscles, how does calcium regulate their cross-bridge cycles in what is called excitation-contraction coupling?
Motor neurons release neurotransmitters (acetylcholine) that signals the muscle fiber at the endplate to let in Na+ ions, which depolarizes the cell. The depolarization leads to the sarcoplasmic reticulum releasing calcium ions. These ions will then bind
How does calmodulin regulate the activation/relaxation of smooth muscle?
Smooth muscle cells do not have the troponin/tropomyosin complex, but they can use calmodulin, which binds to calcium ions either from the SR or from opening up calcium membrane channels. The calmodulin-Ca2+ complexes activate myosin kinases, which in tur
How does acetylcholinesterase affect excitation-contraction coupling? How does botox affect it?
Acetylcholinesterase breaks down acetylcholine, the signal that causes depolarization and action potentials in muscle cells. Botox prevents exocytosis of acetylcholine from motor neurons.
Differentiate antagonist and agonist muscle groups.
Antagonist muscle groups have one that does flexion and one that does extension. Agonist muscle groups work together in the same direction of joint rotation.
At what range of myosin and actin overlap is ideal for maximum output force?
Ideally, you want the distance between myosin and actin to be at intermediate ranges. Too far, there's not enough cross-bridges; too close, the myosin will start hitting the Z disks.
Describe the relation between muscle shortening velocity and max force applied.
Shortening velocity and max force applied have an inverse relationship because higher forces require more time for more cross-bridges to force. Isometric forces and lengthening contractions can handle higher amounts of force because they have zero or nega
What are the two ways that muscle force can be summed and how do they differ?
Muscle force can be summed if multiple acetylcholine neurotransmitters continuously signal muscle contractions. One impulse would cause a twitch, but enough impulses would cause a full contraction. Too many impulses would lead to tetanus (no more force ca
Describe the differences between slow-twitch muscle fibers and fast-twitch muscle fibers.
Although both exist in most skeletal muscles and are very useful, slow-twitch muscles use ATP from aerobic respiration, uses more myoglobin, and is more economically efficient, while fast-twitch muscles use ATP from glycolysis and expend ATP very rapidly.
What are ways that we can increase and decrease the rate of diffusion of gases?
Increase diffusion rate: thinner barrier, larger surface area, higher partial pressure gradient
Decrease diffusion rate: opposite of all the above
Differentiate concurrent flow and countercurrent flow. How does this relate to the flow of blood in fish gills for gas exchange?
Concurrent flow is two fluids of opposite properties flowing in the same direction next to each other, and diffusion of heat or gases causes them to approach an intermediate value.
Countercurrent flow is two fluids of opposite properties flowing in opposi
Explain what tidal ventilation looks like in the human respiratory system.
Unlike amphibians, humans use negative pressure to inhale air. The diaphragm and intercostal muscles are the muscle that contract to provide the negative pressure. Elastic recoil and the intercostal muscles on the ribs help relax the diaphragm, cause a pr
How is respiration controlled involuntarily and how is it controlled voluntarily?
Your body uses carotid and aortic bodies to detect oxygen, carbon dioxide, and hydronium concentrations in the blood. Breathing rate adjusts to any changes automatically. Animals can voluntarily control their respiration by speaking, singing, using mating
Explain Boyle's Law and pressure gradients and why it is important to both respiration and the cardiac cycle.
Boyle's Law states that given constant conditions, pressure and volume are inversely related and that P1V1 = P2V2. The pressure gradient allows fluids to move from areas of high to low pressure.
In the lungs, the diaphragm contracts, expanding the lung's
Explain the pattern of oxygen's partial pressures in the lungs, blood plasma, and red blood cells.
The diffusion of oxygen from the lungs into the blood vessels and then into the red blood cells to be bound to hemoglobin suggests the partial pressure of oxygen is always higher in the threshold before, allowing for constant diffusion from high to low.
Explain the oxygen dissociation curve and its trends.
The oxygen dissociation curve plot % hemogloblin saturation as a function of the partial pressure of oxygen in the blood fluid. It has a sigmoidal shape due to two things: cooperative binding and saturation. Cooperative binding is when attachment of one o
What is myoglobin, and why is it useful?
Myoglobin is a monomer version of hemoglobin that only carries one oxygen molecule at a time. Instead of have the cooperative binding property, it has a much higher oxygen affinity. Therefore, myoglobin is often used as oxygen storage for secondary use, s
How can binding affinity and pH affect what the oxygen dissociation curve looks like?
Increasing binding affinity shifts the whole curve to the left, and increasing pH shifts it to the left as well. This means that lower pH values shift it to the right.
What is the purpose of carbonic anhydrase near the systemic tissues? What is its purpose at the lungs? What is its purpose in stomach cells?
Systemic tissues: converts CO2 to H2CO3 to lower pH, allowing more oxygen to be released from hemoglobin
Lungs: converts H2CO3 to CO2 so CO2 can be released from the blood
Stomach: produces H+ to be secreted into the stomach and HCO3- to be used to transp
Explain the differences in sizes of the different blood vessel tubes of the human body.
Resistance to flow is proportional to 1/(radius^4). Knowing this, the sizes of arteries and veins are evolutionarily designed. As vessels travel away from the heart, they get smaller. As they travel back to the heart, they get larger. This ensures uniform
How are arteries designed to carry just enough blood from the heart to the peripheral body parts?
Smooth muscle contracts to reduce flow and relaxes to accelerate flow. Collagen and elastin proteins create an elastic layer around arteries to protect it during expansion and reduction. When you want to conserve/release heat or manage flow rate, smooth m
How does the anatomy and function of veins differ from that of arteries?
Veins have little smooth muscle and are typically very small. Veins have little pressure and thus carry blood back slowly (which is why most of your blood is deoxygenated at any time). To get blood back to the heart against gravity, we have valves to prev
Relate blood pressure and osmotic pressure to explain the filtering of blood across the blood vessels. What does the lymphatic system have to do with this?
High blood pressure areas of the vessel cause ions, water, and small molecules to be ejected. At these points, the blood pressure outweighs the osmotic pressure (osmosis of water back into the vessel), so there's a net movement outward (this is filtration
How do hormones regulate blood pressure?
Hormones aim for a set point for blood pressure by applying vasoconstriction to increase pressure and resistance (lower flow) or vasodilation to decrease pressure and resistance (higher flow).
What's the difference between pulmonary circulation and systemic circulation?
Pulmonary circulation is the heart pumping deoxygenated blood to the lungs and systemic circulation is the heart pumping oxygenated blood to the rest of the body.
Explain the flow of blood in human hearts and lungs. How do we define one cardiac cycle?
Deoxygenated blood flows into the right atrium, which then contracts to push blood through the AV valve into the right ventricle, which then contracts to push it through the pulmonary valve into both the left and right pulmonary arteries. Oxygenated blood
What constitutes one cardiac cycle?
Each cycle begins with ventricular diastole (atrial systole) when ventricles relax and atria contract, followed by ventricular systole (atrial diastole) when ventricles contract and atria relax.
How does cardiac muscle in the heart contract in synchronous fashion during diastole and systole?
SA node pacemaker cells generate action potentials (SA node cells can depolarize rhythmically on their own) independent of the nervous system, which causes both atria to contract at the same time. This is possible because they have gap junctions and the d
How do you calculate blood pressure?
Blood pressure is measured as the ratio of systolic pressure in the artery to diastolic pressure in the artery.
How does the autonomic nervous system control your heart rate?
Although the SA node and AV node cells can operate independently of the nervous system, sympathetic and parasympathetic neurons can stimulate and influence depolarization rates of SA node cells. By increasing heart rate, stroke volume automatically increa
What is osmosis? What is osmotic pressure?
Osmosis is the diffusion of water from high to low concentrations of water. Osmotic pressure is the tendency of water to "want" to diffuse into a solution or across a membrane (it is proportional to solute gradient).
What are osmoconformers and osmoregulators?
1. Osmoconformers match their osmotic pressure with that of the environment.
2. Osmoregulators use energy to regulate the osmotic pressures in their body and cells to be different than that of the environment.
How are water and electrolytes consumed and how are they removed from organisms?
Water and electrolytes are consumed via water and food and removed via feces, urination, sweating, and respiration.
Differentiate the three types of nitrogenous waste.
1. Ammonia is very soluble in water, very toxic, and can affect pH balance.
2. Urea is quite soluble in water and is less toxic; however, it requires energy to create out of NH3 and water to excrete.
3. Uric acid is not soluble in water and is the least t
What are the excretory organs (for liquids) in humans? What three processes take place in these organs?
Blood is filtered by the kidneys. Filtration, reabsorption, and secretion occurs at the kidneys.
Describe the anatomy of a kidney and a nephron.
Key Terms: cortex, medulla, glomerulus, Bowman's capsule, proximal convoluted tubule, loop of Henle, distal convoluted tubule, collecting ducts, vasa recta, renal pelvis, ureter, bladder
Kidneys have to layers: an outer cortex and an inner medulla.
Nephrons have a glomerulus (capillaries where blood pressure causes filtration) that is located in the cortex layer.
The renal tubule consists of a proximal convoluted tubule, a loop of Henle,
How exactly does the glomerulus filter the blood within the Bowman's capsule?
The layering of endothelial layer cells, basal lamina, and podocytes allows only water and small molecules to enter as the filtrate.
What is the role of the proximal convoluted tubule?
Located in the nephron cortex, the proximal convoluted tubule uses microvilli to actively reabsorb any amino acids, glucose, or minerals. Water diffuses into the medulla and back into the blood.
What are the components of the loop of Henle and how does it act as a countercurrent multiplier? What role does the vasa recta have?
The loop of Henle has a descending limb (where water diffuses out) and an ascending limb (where NaCl is actively pumped out). Both these processes make the inner areas of the medulla very concentrated with solute.
The vasa recta also maintain the medulla'
What is the role of the distal convoluted tubule?
Located in the nephron cortex, the distal convoluted tubule regulates key electrolytes as well as bicarbonate and H+ for pH balance. It does both secretion and reabsorption.
How does antidiuretic hormone control water balance in the collecting ducts?
ADH is released from the posterior pituitary gland and functions to increase the permeability of water in the collecting ducts. This causes more water reabsorption into the medulla and more concentrated urine.
What is the correlation between the length of loops of Henle and water conservation abilities?
Longer loops of Henle allow for a longer solute gradient in the medulla. This allows the collecting ducts to be longer and allow for more water to diffuse back into the body.
How can the kidneys regulate blood pressure and volume?
Key Terms: juxtaglomerular apparatus, renin, angiotensin II, aldosterone
The juxtaglomerular apparatus cells near the glomerulus can detect low blood pressure and secrete the hormone renin. It is an enzyme that begins a chemical series that ends with angiotensin II, which tells smooth muscles to constrict and causes the releas
Relate consumption of food to energy balance and nutrition.
Food provides macromolecules, vitamins, essential amino acids, and minerals that are used to generate chemical energy or help bodily functions.
Most of the energy is used for bodily function and the rest is for physical activity.
Excess energy is stored a
What are the main parts of our digestive tract and how does matter move through it?
We have a foregut (digestion), a midgut (absorption), and a hindgut (excretion). Matter moves through the tract by peristalsis, waves of smooth muscle contraction and relaxation.
Describe mechanical digestion in the mouth and trace its journey in the foregut.
Key Terms: amylase, epiglottis, esophagus, lipase, pharynx, stomach
We use our tongue and teeth to break food into bits that tongue enzymes amylase (carbs) and lipase (fats) can dissolve further.
The bits are then swallowed into the pharynx, over the epiglottis (covers trachea), through the esophagus, and into the stomach
How is the stomach optimized for digestion?
Key Terms: gastrin, hydrochloric acid, lipase, mucus, pepsin, pyloric sphincter
The low pH of the stomach acid allows for special enzymes to function in chemical breakdown.
The low pH is due to HCl, which is homeostatically regulated by the hormone gastrin.
Stomach glands secrete mucus as a buffer layer.
Pepsin and lipase are secrete
How does digestion and absorption occur in the small intestine and how do organs assist it?
Key Terms: duodenum, jejunum, ileum, lactase, pancreas, amylase, lipase, trypsin, bicarbonate, hydronium, secretin, liver, bile, gallbladder, CCK, microvilli, gluc
The remaining digestion occurs in the duodenum and absorption occurs in the jejunum and ileum.
While the small intestine itself can produce lactase, the pancreas (previously known for secreting insulin/glucagon into blood) secretes amylase, lipase, and tr
What occurs at the large intestine?
Water and inorganic minerals are absorbed, leaving feces in the rectum until it is time for excretion.
Describe the general anatomy of the digestive tract and the role of each structure.
Key Terms: lumen, mucosa, submucosa, circular/longitudinal muscle layers, serosa, mesentery
The lumen is surrounded by a mucosa, which absorbs nutrients and releases enzymes. Underneath is the submucosa with nerves and blood vessels.
The mucosa is surrounded by a circular muscle layer and a longitudinal muscle layer, which both are responsible f
What are the two vestigial structures (in the digestive tract) that humans have?
The cecum and appendix are vestigial structures useless to us.