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physiology unit 3-4
| Question | Answer |
|---|---|
| What is a sensory receptor and how is it stimulated? | It is a structure sensitive to an adequate stimulus; some detect one stimulus, others multiple. |
| What are the characteristics of a generated potential? | Stimuli cause depolarization in the sensory receptor and associated sensory neuron. |
| Which receptors are responsible for touch? | tactile and Bulbous corpuscles. |
| Which receptors are responsible for vibration? | Lamellar and tactile corpuscles (low vibration). |
| Which receptors are responsible for temperature, pain, and light touch? | Free nerve endings. |
| Which receptors are responsible for proprioception? | Lamellar and Bulbous corpuscles. |
| Are Bulbous corpuscles slow or fast adapting? | Slow adapting. |
| Are tactile corpuscles slow or fast adapting? | Rapidly adapting. |
| Are Lamellar corpuscles slow or fast adapting? | Rapidly adapting. |
| What is the role of free nerve endings? | Protective mechanism sensing potential harm or damage. |
| Where are hair follicles found? | All over body except palms and soles. |
| What do hair follicle receptors detect? | Mechanical stimuli such as hair movement or displacement. |
| Do hair follicle receptors adapt to continuous stimulation? | Yes, to maintain sensitivity to changes in hair position. |
| What are receptor generated potentials similar to? | EPSPs and IPSPs. |
| Are receptor generated potentials usually depolarizing or hyperpolarizing? | depolarizing, but can be hyperpolarizing. |
| What causes receptor generated potentials? | Increased membrane permeability to Na+ (or K+ for hyperpolarizing). |
| Do receptor generated potentials propagate down the neuron? | No, they are local and spread like E/IPSPs. |
| How do receptor generated potentials change over time and space? | They decrease over time and space. |
| Are receptor generated potentials proportional to the stimulus? | Yes. |
| What is neural coding? | Process where sensory cells release neurotransmitters proportional to stimulus, eliciting action potentials. |
| How does the brain interpret neural coding? | By frequency of action potentials (IPSP or EPSP). |
| What are the two major ascending sensory pathways? | Spinothalamic tract and Dorsal Column-Medial Lemniscal system. |
| What does the spinothalamic tract carry? | Pain, crude touch, temperature. |
| Where does the spinothalamic tract cross over? | Immediately when first order nerve enters spinal column. |
| What does the dorsal column-medial lemniscal system carry? | Fine detail, proprioception, vibration. |
| Where does the dorsal column-medial lemniscal system cross over? | Higher up the spinal cord at the second order neuron. |
| Where is the first order sensory nerve found? | Peripheral sensory nerve, ipsilateral. |
| Where is the second order sensory nerve found? | Spinal cord, contralateral. |
| Where is the third order sensory nerve found? | Brain, contralateral. |
| What describes the somatotopic organization of the postcentral gyrus? | A homunculus, with feet in the middle and senses mapped outward. |
| What is the somatosensory cortex? | Brain region in parietal lobe that processes sensory information. |
| How is the somatosensory cortex organized? | Mapped into a homunculus with areas corresponding to body parts. |
| What is the role of the somatosensory cortex? | Interpret sensory data for tactile sensation, proprioception, and localization of stimuli. |
| How does the somatosensory cortex relate to the motor cortex? | It provides sensory input that enables appropriate motor responses and interactions. |
| What structures make up the visual system? | Eye, visual pathway, and primary visual area. |
| What does the eye contain? | Photoreceptors that convert light into action potentials. |
| What does the visual pathway do? | Transmits action potentials via the optic nerve. |
| Where is the primary visual area found? | Occipital lobe, posterior brain above cerebellum. |
| What is the function of the primary visual area? | Processes incoming visual signals. |
| What is the cornea? | Thin, transparent dome at the front of the eye. |
| Is the cornea vascular or avascular? | Avascular, nourished by tears. |
| What is the function of the cornea? | Primary light-focusing structure, bends light rays to form clear retinal image. |
| What is the iris? | Colored part of the eye containing muscles that regulate pupil size. |
| What is the lens? | Flexible structure that changes shape for accommodation and focuses light on retina/fovea. |
| What is the retina? | Thin, light-sensitive tissue at back of eye containing rods and cones. |
| What is the function of the retina? | Converts light into electrical signals sent to brain via optic nerve. |
| What is the fovea? | Small central pit in retina with highest visual acuity |
| What photoreceptors are found in the fovea? | Cones only, densely packed. |
| What is the function of the fovea? | Sharp central vision, detailed color vision in bright light. |
| What is the optic nerve? | Transmits visual information from retina to brain. |
| What composes the optic nerve? | Retinal ganglion cell axons and supportive cells. |
| What is the pigment layer of the retina? | Layer that absorbs excess light and supports photoreceptors. |
| What are rod cells responsible for? | Vision in low light, high sensitivity, no color, poor detail. |
| How many photopigments do rods have? | One photopigment. |
| What happens to rods in low light? | Hyperpolarize, stop releasing neurotransmitters, vision in black and white. |
| What happens to rods in complete darkness? | Depolarize and release inhibitory neurotransmitter onto bipolar cells. |
| What are cone cells responsible for? | Color vision and high detail in bright light. |
| How many photopigments do cones have? | Three photopigments (blue, green, red). |
| Where are cones concentrated? | Fovea. |
| What happens to cones in bright light? | Hyperpolarize and stop releasing neurotransmitters, allowing color and detail vision. |
| What happens to cones in the dark? | Depolarize and release inhibitory neurotransmitter onto bipolar cells. |
| What do bipolar cells do? | Integrate signals from multiple rods or cones. |
| What do amacrine cells do? | Modulate signals between bipolar and ganglion cells. |
| What do ganglion cells do? | Final output neurons transmitting visual info to brain. |
| How does vision use graded potentials? | Rods and cones release NT that inhibit bipolar cells; light hyperpolarizes them, enabling bipolar depolarization. |
| What happens at low light levels? | Rods hyperpolarize, bipolar cells depolarize, ganglion cells activated. |
| What happens at bright light levels? | Cones hyperpolarize, bipolar cells depolarize, ganglion cells activated. |
| What cells can create graded potentials? | Rods and bulbous cells. |
| Do rods and cones activate or shut down with light? | They are shut down (hyperpolarized) by light. |
| Where are rods located? | Mostly outside and around the fovea. |
| Where are cones located? | mostly in the fovea. |
| How is light transduced to action potentials? | Through graded potentials. |
| What are saccades? | Darting eye movements like reading. |
| What is smooth pursuit? | Following an object smoothly to keep it in the fovea. |
| What is the vestibular ocular reflex (VOR)? | Eye movement that keeps gaze fixed while head moves. |
| What are vergences? | Eye movements like convergence when focusing on a near object. |
| What is the process of seeing? | Light changes photopigment shape, decreases Na+ permeability, hyperpolarizes rods/cones, reduces inhibitory NT, activates bipolar and ganglion cells, signals sent to visual cortex. |
| What are the structures in the auditory system? | Auricle, canal, tympanic membrane, ossicles, oval window, round window, semicircular canals, cochlea, otolith organs, auditory tube. |
| What is the function of the auricle? | Collects and localizes sound. |
| What is the function of the canal? | Transmits sound and provides protection; curved to enhance transmission. |
| What is the tympanic membrane? | Barrier that converts air waves into mechanical vibrations. |
| What are the ossicles? | Incus, malleus, stapes; transmit vibrations from eardrum to inner ear. |
| What is the oval window? | Where stapes rests; vibrates hair cells to transmit info to auditory nerve. |
| What is the round window? | Dissipates waves; end of cochlea. |
| What are the semicircular canals? | Three loop-shaped structures for balance and spatial orientation in all planes. |
| What is the cochlea? | Spiral fluid-filled structure that transforms vibrations into neural signals. |
| What are the otolith organs? | Utricle (horizontal) and saccule (vertical); sense acceleration and deceleration. |
| What is the auditory tube? | Connects middle ear to nasopharynx for pressure stabilization and fluid drainage. |
| What are the three sections of the cochlea? | Scala vestibuli, cochlear duct, scala tympani (top to bottom) |
| What fluid fills the scala vestibuli and tympani? | Perilymph, resembling extracellular fluid. |
| What fluid fills the cochlear duct? | Endolymph, resembling intracellular fluid. |
| What is the basilar membrane? | Membrane between cochlea and scala tympani; supports organ of Corti. |
| What is the organ of Corti? | Structure where sound waves are converted to action potentials by hair cells. |
| What covers the organ of Corti? | Tectorial membrane. |
| How do hair cells in the organ of Corti work? | Basilar membrane vibration bends stereocilia, depolarizing hair cells. |
| Where are low frequency sounds detected? | Apex of cochlea. |
| Where are high frequency sounds detected? | Base of cochlea. |
| How does the outer ear transmit sound? | Auricle funnels sound inward. |
| How does the middle ear transmit sound? | Converts air waves into mechanical vibrations via ossicles to oval window. |
| How are standing waves formed in the cochlea? | Basilar membrane stiffness varies and when the sound matches a section on the basilar membrane and a standing wave is formed |
| How do hair cells transduce sound? | Stereocilia bend, ion channels open, depolarization triggers NT release, action potentials in auditory nerve. |
| Which structures are important for hearing quiet sounds? | Entire middle ear including tympanic membrane and ossicles. |
| What structures contribute to balance? | Semicircular canals and otolith organs. |
| What do semicircular canals detect? | Rotational movements in three planes. |
| What do otolith organs detect? | Acceleration and falling; utricle for horizontal, saccule for vertical. |
| What are major functions of the vestibular system? | Detect changes in head movement and position in space. |
| How do semicircular canals detect movement? | Endolymph moves cupula in ampulla, bending hair cells. |
| How do otolith organs detect movement? | Otoliths on gelatinous membrane move and bend hair cells. |
| How is balance and spatial orientation maintained? | Integration of semicircular canals, otolith organs, vision, and proprioception. |
| What is the vestibulo-ocular reflex (VOR)? | Reflex stabilizing vision by counteracting head movements with eye movements. |
| What are hair cells? | Sensory receptors with stereocilia that bend to release neurotransmitters for hearing and balance. |
| What is the kinocilium? | The long hair on hair cells. |
| What are stereocilia? | Short hairs on hair cells. |
| What happens when stereocilia bend toward kinocilium? | Cell releases more neurotransmitter. |
| What happens when stereocilia bend away from kinocilium? | Cell releases less neurotransmitter. |
| Where is vestibular sensory information sent? | To the brain to coordinate balance, posture, and eye movements. |
| What does the left atrium do? | Receives oxygenated blood from pulmonary veins and pumps it into ventricles. |
| Which artery carries deoxygenated blood? | Pulmonary artery. |
| Which veins carry oxygenated blood? | Pulmonary veins. |
| What are the three components of the cardiovascular system? | Heart, vessels, and blood. |
| What are the four primary functions of the cardiovascular system? | Transport, regulate, protect, and maintain BP & perfusion. |
| Which ventricle has more muscle and why? | Left ventricle, pumps to systemic aorta with high force. |
| What is the pathway of blood from the right atrium to systemic capillaries? | Right atrium → right AV valve → right ventricle → pulmonary valve → pulmonary artery → pulmonary capillaries → pulmonary veins → left atrium → left AV valve → left ventricle → aortic valve → aorta → systemic capillaries. |
| What are the four valves of the heart? | Tricuspid, bicuspid (mitral), pulmonary, aortic. |
| What is the structure of the ventricular valves? | Pulmonary and aortic are tricuspid and parachute-like. |
| How are cardiomyocytes similar to skeletal myofibers? | Both striated, need calcium, have mitochondria, require action potentials. |
| Where does calcium come from in skeletal muscle? | Sarcoplasmic reticulum. |
| Where does calcium come from in cardiomyocytes? | SR and extracellular fluid (calcium-induced calcium release). |
| How are cardiomyocytes different from skeletal myofibers? | C=branched, mononucleate, connected by gap junctions; S=cylindrical, multinucleate, neuron-activated. |
| What is calcium-induced calcium release? | Extracellular Ca²⁺ entry triggers further Ca²⁺ release from SR in cardiomyocytes (calcium cascade) |
| What are intercalated disks? | Structures containing desmosomes that hold cardiomyocytes together. |
| Why are gap junctions important? | They allow electrical signals to pass for cohesive heartbeats. |
| What is the role of nodal/conducting cardiomyocytes? | Self-excitable cells generating action potentials that spread across the heart. |
| Do nodal cardiomyocytes contract strongly? | No, they lack enough actin and myosin. |
| How does an SA node action potential differ from a neuron AP? | _______ has pacemaker potential, Ca²⁺-based depolarization, no hyperpolarization. |
| What ions are involved in SA node pacemaker potential? | Na⁺ and Ca²⁺ influx, K⁺ efflux. |
| What ions are involved in SA node full depolarization? | Ca²⁺ influx via voltage-gated channels. |
| What ions are involved in SA node repolarization? | K⁺ efflux. |
| Is there hyperpolarization in SA node AP? | No. |
| What is resting heart rate? | Heart rate at rest without exercise, approx. 100BPM |
| How is maximum heart rate calculated? | 220 minus age. |
| What is the pacemaker potential? | Graded potential in SA node where Na⁺ and Ca²⁺ slowly depolarize to threshold, this can be manipulated to be faster or slower |
| What happens when threshold is reached in SA node? | Ca²⁺ influx generates AP causing atrial contraction. |
| How do heart rate changes occur? | On a gradient depending on sympathetic or parasympathetic dominance. |
| What happens at SA node during resting HR of 60 bpm? | Parasympathetic branch increases K⁺ permeability, reduces Ca²⁺/Na⁺ permeability, slowing depolarization and reducing the slope of the pacemaker potential |
| If HR is 140 bpm, how often does SA node fire? | Every 0.43 seconds, once per heartbeat 60s/140bpm=0.43s |
| What happens at SA node during HR of 140 bpm? | Sympathetic activity increases Na⁺/Ca²⁺ permeability, steepening pacemaker slope. |
| How does an SA node AP spread through the heart? | SA node → AV node → AV bundle (in septum) → R + L bundle branches (@ apex)→ subendocardial branches (up ventricles) |
| Why must AP slow at AV node? | To allow atria to empty before ventricles contract. |
| Why must AP speed at subendocardial branches? | To quickly activate ventricles for blood ejection. |
| If SA node fails, what happens? | AV node takes over as pacemaker. |
| How does ANS affect AV node? | Slows or speeds AP to coordinate contraction. |
| How does ANS affect ventricular cardiomyocytes? | Changes force of contraction. |
| What is HR at 100 bpm without ANS influence? | Intrinsic SA node rate. |
| What is the purpose of an ECG? | To show electrical activity of the heart. |
| How is an ECG performed? | Electrodes placed on chest, arms, legs, giving 12 views. |
| What does the P wave represent? | Atrial depolarization. |
| What does the QRS complex represent? | Ventricular depolarization and hidden atrial repolarization. |
| What does the T wave represent? | Ventricular repolarization. |
| What happens during isovolumetric ventricular systole? | Ventricles start contracting but no blood is ejected yet. |
| What happens during ventricular systole? | Ventricles contract, pressure rises, blood ejected into aorta and pulmonary artery. |
| What happens during isovolumetric ventricular diastole? | Ventricles begin to relax, no filling yet. |
| What happens during late ventricular diastole? | Ventricles relax and fill passively with blood from atria. |
| What happens during atrial systole? | Atria contract, pushing blood into ventricles (more like a top up) |
| What happens during atrial diastole? | Atria relax and fill with blood. |
| In which phase is ventricular pressure higher than aortic pressure? | During ventricular systole, allowing blood ejection. |
| Why is ventricular pressure higher than aortic pressure important? | Blood moves down pressure gradient, enabling ejection. |
| Which ECG event corresponds to ventricular relaxation? | T wave, ventricular repolarization. |
| When does most ventricular filling occur? | During late ventricular diastole - when they are relaxing and passively getting blood from atria |
| What does atrial systole contribute to filling? | A small “top up” of blood into ventricles. |
| What happens to pressures during isovolumetric ventricular diastole? | Aortic high, ventricular low, atrial rising. |
| What happens to pressures during late ventricular diastole? | Aortic decreasing, ventricular low, atrial high with passive flow. |
| What happens to pressures during atrial systole? | Aortic decreasing, ventricular low, atrial high with active contraction. |
| What is stroke volume? | Amount of blood pumped out of ventricles per heartbeat. |
| How do you calculate stroke volume? | End diastolic volume minus end systolic volume (EDV - ESV). |
| What is end systolic volume (ESV)? | Blood left in ventricles after contraction. |
| What does low ESV indicate? | Strong heart pumping ability. |
| What does high ESV indicate? | Weak pumping, possible dysfunction. |
| What is end diastolic volume (EDV)? | Blood in ventricles before contraction, after atrial filling. |
| How are stroke volume and cardiac output related? | Cardiac output = stroke volume × heart rate. |
| What is cardiac output? | Amount of blood pumped per minute, measure of heart function. |
| What is normal cardiac output? | 5–6 liters per minute. |
| What are two ways stroke volume can be changed? | By autonomic nervous system and by preload. |
| How does SNS affect stroke volume? | Norepinephrine increases Ca²⁺ permeability, stronger contraction, higher stroke volume. |
| How does PSNS affect stroke volume? | Acetylcholine decreases Ca²⁺ permeability, weaker contraction, lower stroke volume. |
| Which branch has more innervation to cardiomyocytes? | Sympathetic branch, for stronger fight-or-flight contractions. |
| What is preload? | Load on the heart prior to contraction, measured by EDV. |
| How does increased preload affect stroke volume? | Higher EDV stretches ventricles, stronger contraction, higher stroke volume. |
| What law explains preload and stroke volume? | Frank-Starling’s Law: increased preload leads to equal increased output. |
| Why is Frank-Starling’s Law protective? | Prevents heart from overfilling by matching output to preload. |
| How can preload be increased? | By increased venous return to the heart. |
| What is the general pathway of blood flow through the kidney? | Aorta → renal artery → kidney → renal vein → vena cava → right atrium → right ventricle → pulmonary artery → pulmonary vein → left atrium → left ventricle → aorta. |
| Where is most blood found in the circulatory system? | In the systemic circuit, mainly in veins (70%). |
| What do veins regulate? | How much blood returns to the heart. |
| What are the three layers of blood vessels? | Tunica externa, tunica media, tunica interna. |
| What is the tunica externa? | Fibrous connective tissue with blood vessels and autonomic neurons. |
| What is the tunica media? | Smooth muscle, elastin fibers, collagen. |
| What is the tunica interna? | Endothelial cells lining all blood vessels. |
| What layers do capillaries have? | Only tunica interna (endothelial cells). |
| How does the tunica media differ in arteries? | Thick, mostly elastin and smooth muscle, withstands high pressure. |
| What is the thickness of arteries? | thickness ~25% of diameter. |
| What is the blood pressure in arteries? | High, 120–80 mmHg, pulsatile. |
| How does the tunica media differ in arterioles? | Mostly smooth muscle, smaller lumen, resistance vessels. |
| What is the thickness of arterioles? | thickness ~50% of diameter. |
| What is the blood pressure in arterioles? | Decreasing, ~80 mmHg down to 35 mmHg. |
| What is the blood pressure in capillaries? | Low, ~20 mmHg. |
| What is the blood pressure in venules? | ~10 mmHg. |
| What are veins? | Large diameter vessels returning blood to the heart. |
| What is the wall thickness of veins? | thin walls ~10% of lumen size. |
| What is the function of veins? | Return blood to heart, capacitance vessels holding ~70% of blood volume. |
| What is the blood pressure in veins? | ~5–10 mmHg. |
| Why can veins increase end diastolic volume? | ANS innervation contracts smooth muscle, squeezing blood back to heart. |
| What mechanism besides ANS increases EDV? | Skeletal muscle pump squeezes veins, forcing blood back to heart. |
| Why is blood flow regulation important? | To supply active tissues, maintain vital organ perfusion, regulate MAP, and control heat loss. |
| Is blood flow equally distributed to organs? | No, it changes dynamically with activity and environment. |
| What is the relationship between blood flow, pressure, and resistance? | Blood flow = pressure gradient (P1–P2) x radius^4 |
| What 3 factors influence resistance? | Diameter, viscosity, and vessel length. |
| Why are arterioles resistance vessels? | Small diameter, smooth muscle constriction/dilation, high resistance. |
| What is unique about arteriole structure? | Lots of smooth muscle connected to neurons for constriction/dilation. |
| What are mechanisms of blood flow regulation? | Local (pressure, temperature, gases), humoral (blood substances), neural (nervous system). |
| What happens to pressure before vasoconstriction? | Higher pressure. |
| What happens to pressure after vasoconstriction? | Lower pressure. |
| Why are capillaries called exchange vessels? | They allow movement of oxygen, nutrients, and wastes between blood and tissue. |
| What is transcellular transport? | Movement through endothelial cells via diffusion, channels, facilitated diffusion, active transport, or endocytosis/exocytosis. |
| What is paracellular transport? | Bulk flow of fluid and molecules through clefts between cells. |
| What are the three types of capillaries? | Sinusoidal (leaky, liver/spleen), continuous (tight junctions, everywhere), fenestrated (holes, kidneys/intestines). |
| What is bulk flow in capillaries? | Filtration of fluid out paracellularly. |
| What happens with excessive filtration? | Edema (tissue swelling). |
| What forces drive filtration and reabsorption? | Starling forces (hydrostatic and osmotic pressure). |
| Why is there more filtration at the arterial end of capillaries? | Higher hydrostatic pressure drives fluid out. |
| Why is there reabsorption at the venous end of capillaries? | Lower pressure allows fluid to move back in. |
| Why do we have a lymphatic system? | To collect excess interstitial fluid and return it to circulation. |
| What do lymph nodes do? | Scan lymph for bacteria and pathogens before fluid returns to heart. |
| How does local regulation of blood flow work? | Stimulus comes from the same tissue; intrinsic mechanism. |
| How does humoral regulation of blood flow work? | Substances like hormones travel through vessels to target receptors; extrinsic mechanism. |
| How does neural regulation of blood flow work? | Sympathetic neurons release norepinephrine on adrenergic receptors in tunica media, causing vasoconstriction; extrinsic mechanism. |
| What are the two types of intrinsic autoregulatory mechanisms? | Myogenic theory and metabolic theory. |
| What does the myogenic theory explain? | Arterioles sense pressure changes and constrict with high pressure or dilate with low pressure. |
| What does the metabolic theory explain? | Tissues with higher metabolic demand produce vasodilator metabolites that increase blood flow. |
| What metabolic changes occur in active tissue? | High CO₂, H⁺, adenosine, temperature; low O₂ |
| What are vasodilator metabolites (VDM)? | CO₂, H⁺, adenosine, temperature increase, and decreased O₂. |
| Which substances cause vasoconstriction in humoral regulation? | Epinephrine (alpha receptors), angiotensin II, antidiuretic hormone. |
| Which substances cause vasodilation in humoral regulation? | Histamine, atrial natriuretic peptide (ANP), epinephrine (beta receptors). |
| Why does epinephrine cause vasoconstriction in some vessels but vasodilation in others? | Depends on receptor type: alpha causes constriction, beta causes dilation. |
| How is mean arterial pressure (MAP) calculated? | MAP = diastolic pressure + 1/3 (systolic – diastolic) or MAP = CO × TPR. |
| Why is MAP weighted toward diastolic pressure? | The heart spends more time in diastole than systole. |
| How does stroke volume affect MAP? | Higher stroke volume increases cardiac output, raising MAP. |
| How does heart rate affect MAP? | Higher heart rate increases cardiac output, raising MAP. |
| How does resistance affect MAP? | High = increases total peripheral resistance, raising MAP. Low = lowers total peripheral resistance, decreasing MAP. |
| How does sympathetic nervous system activation affect MAP? | Increases HR, stroke volume, venous return, and vasoconstriction, raising MAP. |
| How does parasympathetic nervous system activation affect MAP? | Decreases HR, reduces sympathetic activity, indirectly dilates vessels, lowering MAP. |
| What is the baroreceptor reflex? | Negative feedback system maintaining MAP stability via carotid sinus and aortic arch receptors. |
| How do baroreceptors work? | Stretch receptors detect BP changes, send signals to medulla, adjust HR, SV, and vessel diameter. |
| What happens if MAP is too high? | Baroreceptors signal medulla, SNS reduced, PSNS increased, HR and SV decrease, vasodilation occurs, MAP lowered. |
| What happens if MAP is too low? | Baroreceptors signal medulla, SNS increased, PSNS reduced, HR and SV increase, vasoconstriction occurs, MAP raised. |
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