Final Exam Flashcards
What is external respiration?
Gas exchange between the environment and lungs or gills.
What is internal respiration?
Transport of gases between blood and body tissue cells.
What is cellular respiration?
Breakdown of glucose in mitochondria to produce ATP.
What factors affect the rate of diffusion?
Surface area (↑), concentration gradient (↑), membrane thickness (↓).
Why do large animals need respiratory organs?
Diffusion is only efficient for very small animals.
How do gills support gas exchange?
Water flows over gill filaments; counter-current exchange maximizes O₂ uptake.
How do lungs support gas exchange?
Air enters alveoli where O₂ diffuses into blood and CO₂ diffuses out.
How do insects breathe?
Via tracheal system with spiracles; gases delivered directly to tissues.
How is avian respiration more efficient than mammals?
Unidirectional airflow and cross-current gas exchange in lungs.
Where is O₂ availability higher: sea level or high altitudes?
Higher at sea level.
Why is respiration harder in water than air?
O₂ is less soluble in water and more difficult to extract.
How does temperature affect dissolved O₂ in water?
Warmer water holds less O₂.
What is the path of air in the human respiratory system?
Trachea → Bronchi → Bronchioles → Alveoli.
What increases gas exchange in alveoli?
Large number and small size of alveoli surrounded by capillaries.
What is the role of the pleura?
Double-layered membrane that reduces friction during breathing.
What is tidal ventilation?
Breathing in and out in a back-and-forth (tidal) pattern.
What happens during inhalation?
Diaphragm contracts, rib cage expands, thoracic volume increases, air flows in.
What happens during exhalation?
Diaphragm relaxes, lung volume decreases, pressure rises, air flows out.
What brain regions control breathing?
Medulla and pons in the brainstem.
What does the Dorsal Respiratory Group control?
Normal breathing rhythm.
What does the Ventral Respiratory Group do?
Controls forceful breathing.
What do central chemoreceptors detect?
CO₂ and H⁺ levels in cerebrospinal fluid.
What do peripheral chemoreceptors detect?
O₂ levels in blood (carotid and aortic bodies).
What triggers increased breathing rate?
High CO₂ / low O₂ levels.
How is O₂ transported in the blood?
98% bound to hemoglobin in red blood cells.
What is the oxygen-hemoglobin dissociation curve?
Shows O₂ binding at high PO₂ and release at low PO₂.
What factors promote O₂ release from Hb?
High CO₂, low pH, high temperature (Bohr Effect).
In what three ways is CO₂ transported?
1) Dissolved in plasma, 2) Bound to Hb, 3) As bicarbonate (HCO₃⁻).
What is the Haldane effect?
Deoxygenated Hb binds CO₂ more readily than oxygenated Hb.
What happens in the pulmonary capillaries?
O₂ diffuses into blood, CO₂ diffuses into alveoli.
What happens in the systemic capillaries?
O₂ diffuses into tissues, CO₂ diffuses into blood.
What are the 5 main functions of the circulatory system?
1) Transport oxygen/nutrients/hormones
2) Remove waste (CO₂, nitrogen)
3) Regulate temperature
4) Support immune system
5) Maintain fluid/ion balance (homeostasis)
What type of circulatory system do simple animals like cnidarians use?
Gastrovascular cavity (uses diffusion)
What is an open circulatory system?
blood (hemolymph) is pumped into a body cavity and directly contacts organs (e.g. insects, arthropods)
What is a closed circulatory system?
Blood stays in vessels; more efficient; found in vertebrates and cephalopods
Describe single circulation (found in fish).
Blood passes through the heart once per cycle; lower pressure due to single pump
What circulatory system do amphibians and most reptiles have?
Partial ventricle division; allowing some mixing of oxygenated & deoxygenated blood
Describe double circulation (birds, mammals, crocodiles).
Complete separation of pulmonary & systemic circuits; enabling high pressure; efficient oxygen delivery
What do the atria and ventricles of the heart do?
Atria receive blood; ventricles pump blood
What do valves in the heart do?
Prevent backflow
AV valve: between atria & ventricles
Semilunar valve: between ventricles & arteries
What is systole and diastole?
Systole = heart contracts
Diastole = heart relaxes
myocardium
Self-excitable, rhythmic contractions, high endurance due to lots of mitochondria
What is the heart’s electrical conduction path?
SA node (pacemaker) → AV node (delay) → Bundle of His → Purkinje fibres
How does the sympathetic nervous system affect the heart?
Increases HR and BP using epinephrine/norepinephrine
How does the parasympathetic system affect the heart?
Slows HR using acetylcholine
What do arteries do?
Carry blood away from the heart; thick, high pressure; mostly oxygenated
What do veins do?
Carry blood to the heart; thin, low pressure; contain valves
What do capillaries do?
Enable gas and nutrient exchange with tissues
What are the 3 main functions of the lymphatic system?
1) Fluid balance
2) Fat absorption
3) Immune defense
What are the key components of the lymphatic system?
Lymph (fluid), lymph nodes (filter), lymphatic vessels (transport)
What molecule is used for oxygen transport in many invertebrates, and how does its color change with oxygenation?
Hemocyanin is used. It contains copper and turns blue (Cu²⁺) when oxygenated and colorless (Cu⁺) when deoxygenated.
What unique function does hemolymph serve in insect larvae?
Hemolymph functions as a hydraulic skeleton, helping with movement and structural support.
What is a hemocoel, and in what type of circulatory system is it found?
A hemocoel is the open body cavity in animals with an open circulatory system
What feature allows capillary beds in closed circulatory systems to regulate blood distribution?
Precapillary sphincters and vasomotion control blood distribution by regulating which capillaries receive blood flow.
What are the 4 basic digestive processes?
Breakdown, absorption, storage, and elimination (BASE)
What are carbohydrates, proteins, and fats absorbed as?
• Carbs → monosaccharides (glucose, fructose, galactose)
• Proteins → amino acids
• Fats → glycerol + fatty acids
What are macronutrients and micronutrients?
• Macronutrients: needed in large amounts (carbs, fats, proteins, calcium)
• Micronutrients: needed in small amounts (vitamins, iron, zinc)
What are essential nutrients?
Nutrients that must come from diet (cannot be made by the body)
How many essential amino acids, fatty acids, and vitamins are there?
9 amino acids, 2 fatty acids (omega 3 & 6), 13 vitamins
Vitamin A
- A: vision, bones, teeth, skin
Vitamin D
- D: bone growth, helps absorb calcium
Vitamin E
- E: antioxidant, protects cells
Vitamin K
- K: helps blood clotting (liver protein)
What is intracellular digestion?
Digestion inside cells using endocytosis & exocytosis
What is extracellular digestion?
Digestion in a cavity or tract outside cells
Name 4 types of feeders with examples.
• Fluid feeders: tapeworms, birds
• Suspension feeders: mussels, whales
• Deposit feeders: earthworms, crabs
• Bulk feeders: most animals
What are the 3 parts of a grasshopper’s gut?
• Foregut: mouth, crop, gizzard
• Midgut: stomach, gastric caeca
• Hindgut: ileum, colon, rectum, anus
How do carnivore vs herbivore digestive tracts differ?
• Carnivores: short tract, strong stomach acid
• Herbivores: long tract, large cecum, slow digestion
What’s the difference between monogastric and ruminant stomachs?
• Monogastric: 1 stomach (e.g., humans, pigs)
• Ruminant: 4 chambers (rumen, reticulum, omasum, abomasum — e.g., cows)
What are swallowing and peristalsis?
• Swallowing: reflex to move food into esophagus
• Peristalsis: wave-like muscle contractions moving food along digestive tract
What happens in the mouth, pharynx, and esophagus?
• Mouth: mechanical + chemical digestion (amylase)
• Pharynx: starts swallowing
• Esophagus: moves food to stomach via peristalsis
What does the stomach do?
Secretes gastric juice, digests food, creates chyme
What does the small intestine do?
Chemical digestion and nutrient absorption (has villi & microvilli)
What does the large intestine do?
Forms feces, absorbs water, supports gut microbiota
What are the digestive accessory organs?
• Teeth, tongue, salivary glands
• Liver (makes bile), gallbladder (stores bile), pancreas (enzymes & bicarbonate)
Name the major digestive enzymes and their functions.
• Amylase: breaks starch
• Protease: breaks proteins
• Lipase: breaks fats
• Nuclease: breaks nucleic acids
What’s the difference between anabolism and catabolism?
• Anabolism: builds complex molecules (needs energy)
• Catabolism: breaks down molecules (releases energy)
What is the role of bile in fat digestion and where is it produced and stored?
Bile emulsifies fats, breaking them into smaller droplets for easier enzymatic digestion. It is produced by the liver and stored in the gallbladder before being released into the duodenum.
What is the significance of chylomicrons in fat absorption?
Chylomicrons are protein-coated lipid droplets formed in intestinal mucosal cells. They transport absorbed fatty acids and monoglycerides via the lymphatic system into the bloodstream.
How do enterocytes in the small intestine enhance nutrient absorption?
Enterocytes are epithelial cells that form villi and microvilli (the brush border), dramatically increasing surface area. They also contain brush-border enzymes that complete nutrient digestion.
What enzymes are secreted by the stomach and what are their functions?
HCl: Activates pepsinogen and kills microbes
Pepsin: Begins protein digestion
Gastric lipase: Digests fats
Intrinsic factor: Facilitates vitamin B12 absorption
What are brush-border enzymes and where are they found?
Brush-border enzymes like lactase, maltase, and peptidases are embedded in the microvilli of small intestinal epithelial cells. They perform the final steps of carbohydrate and protein digestion.
What is chyme?
Chyme is a partially digested, semi-liquid mixture of food and gastric secretions formed in the stomach. It is gradually released into the duodenum for further digestion and absorption.
What is autocrine signaling?
A hormone acts on the same cell that secretes it.
What is paracrine signaling?
A hormone affects neighboring cells.
What is neuroendocrine signaling?
Hormones are released from neurons into the blood.
What is endocrine signaling?
Hormones are secreted into the bloodstream to act on distant target cells.
What are amine hormones derived from?
Tyrosine or tryptophan (amino acids).
Are amine hormones water-soluble or lipid-soluble?
Water-soluble; they bind to plasma membrane receptors.
Name some examples of amine hormones.
Epinephrine, norepinephrine, dopamine, melatonin, thyroid hormones.
Are protein/peptide hormones water- or lipid-soluble?
Water-soluble; they bind to plasma membrane receptors.
Give examples of protein/peptide hormones.
Insulin, glucagon, leptin.
Are steroid hormones water- or lipid-soluble?
Lipid-soluble; they bind to intracellular receptors.
What are steroid hormones derived from?
Cholesterol.
Name some steroid hormones.
Cortisol, testosterone, estradiol.
What does the hypothalamus do?
Produces releasing/inhibiting hormones and ADH/oxytocin.
What does the pineal gland secrete?
Melatonin.
What hormones does the anterior pituitary release?
ACTH, TSH, FSH, LH, prolactin, GH, MSH, endorphins.
What does the posterior pituitary do?
Stores and releases ADH and oxytocin.
What hormone is secreted by the parathyroid glands?
Parathyroid hormone (regulates calcium).
What does the thyroid gland secrete?
Thyroid hormones and calcitonin.
What does the adrenal cortex produce?
Cortisol, aldosterone, small amounts of androgens.
What does the adrenal medulla secrete?
Epinephrine and norepinephrine.
What hormones are secreted by the pancreas?
Insulin and glucagon.
What hormones are produced by ovaries?
Estrogen and progesterone.
What do testes secrete?
Androgens (e.g., testosterone).
What is the role of negative feedback in hormone regulation?
Hormones from target glands inhibit the hypothalamus and pituitary.
What does growth hormone do?
Stimulates growth, protein synthesis, and fat metabolism.
What do thyroid hormones regulate?
Metabolism and development.
What causes goiter?
Lack of iodine, which is needed for thyroid hormone synthesis.
What happens during acute stress?
Hypothalamus activates adrenal medulla → EPI/NOR → increases HR and glucose.
What happens during chronic stress?
Hypothalamus releases CRH → pituitary releases ACTH → adrenal cortex releases cortisol.
What does insulin do?
Promotes glucose uptake (lowers blood glucose), glycogen synthesis, and fat storage.
What does glucagon do?
Stimulates glycogen breakdown and glucose release.
What does leptin do?
Signals satiety and energy status to the hypothalamus.
What gastrointestinal hormones regulate digestion?
Gastrin, secretin, and CCK.
What does parathyroid hormone do in calcium regulation?
Increases blood calcium by releasing it from bones and increasing kidney reabsorption.
What does calcitonin do in calcium regulation?
Lowers blood calcium by inhibiting bone resorption.
How are hydrophilic hormones stored?
In secretory vesicles until exocytosis, regulated by calcium.
How are hydrophobic hormones like steroids secreted?
They diffuse out of the cell immediately after synthesis—no vesicle storage.
What two hormones are released by the adrenal medulla in acute stress?
Epinephrine (75%) and norepinephrine (25%).
What are the pros of asexual reproduction?
Rapid reproduction, no need to mate, efficient in stable environments.
What are the cons of asexual reproduction?
No genetic diversity, low adaptability, offspring are clones.
What are the common types of asexual reproduction?
Budding, fission, fragmentation/regeneration, parthenogenesis.
What is parthenogenesis?
Development from an unfertilized egg.
Example: bees, reptiles.
What is the main advantage of sexual reproduction?
Genetic variation, better adaptability in changing environments.
How is genetic variation generated in sexual reproduction?
Independent assortment, crossing over, random fertilization.
What is simultaneous hermaphroditism?
An individual has both ovaries and testes at the same time.
What is sequential hermaphroditism?
An individual changes sex during life (e.g. clownfish).
Where does spermatogenesis occur?
In males testes, continuously from puberty.
What does each spermatocyte produce?
Four haploid sperm.
Where does oogenesis occur?
In females, starts before birth; one oocyte matures per cycle.
What hormone triggers ovulation?
LH (Luteinizing Hormone).
What does FSH do in females?
Stimulates follicle development.
What does estradiol do?
Promotes follicle and oocyte growth.
What does progesterone do?
Prepares uterus for embryo implantation.
What hormones regulate spermatogenesis?
FSH (supports sperm maturation) and LH (stimulates testosterone).
How do sperm and ovum differ?
Sperm: small and mobile; Ovum: large and immobile.
What does the sperm midpiece contain?
Mitochondria for energy.
What surrounds the ovum?
Zona pellucida and vitelline coat.
What is external fertilization?
Gametes released into the environment (aquatic species).
What is internal fertilization?
Occurs inside the female’s body.
What are oviparous species?
Lay eggs, little to no parental support.
What are viviparous species?
Live birth, embryo develops inside the body.
What is ovoviviparous development?
Eggs hatch inside parent’s body with little support (e.g. snakes).
What happens during fertilization?
Egg and sperm unite to form a zygote; diploid restored.
What is cleavage?
Rapid mitotic divisions forming morula → blastula.
What is gastrulation?
Formation of germ layers: ectoderm, mesoderm, endoderm.
What is neurulation?
Formation of the neural tube.
What is organogenesis?
Germ layers form organs and tissues.
What happens during growth and maturation?
Cell division, tissue specialization, and full organism development.
What hormone stimulates the development of a follicle in the ovary?
FSH (Follicle-Stimulating Hormone).
When are FSH and LH levels highest?
During ovulation.
What hormone stimulates the growth and development of the oocyte?
Estradiol.
What secretes estradiol before ovulation?
The developing follicle.
What secretes estradiol after ovulation?
The corpus luteum.
What is the function of estradiol in the uterus?
Thickens the endometrium.
What hormone is secreted by the corpus luteum to prepare the uterus for a fertilized egg?
Progesterone.
What causes the follicle to rupture and release the egg?
The LH surge.
What structure forms after the follicle ruptures?
Corpus luteum.
What is the role of the corpus luteum?
Secretes progesterone (and some estrogen) to maintain the uterine lining.
What happens if fertilization does not occur?
Corpus luteum degenerates, progesterone drops, and menstruation begins.
What is budding?
A new individual grows from the body of the parent (e.g. sponges, cnidarians)
What is fission?
One individual splits into two or more equal parts (e.g. cnidarians)
What is fragmentation / regeneration?
A body part breaks off and regenerates into a new individual (e.g. echinoderms)
Name the three processes that contribute to genetic diversity in sexual reproduction.
Independent assortment during meiosis I
Crossing over during prophase I
Random fertilization
What is the role of FSH in gametogenesis?
Stimulates spermatogenesis in males and follicle development in females
What is osmoregulation?
The control of water and salt balance in the body.
Why is osmoregulation important?
Because protein function depends on proper ion concentrations, which affects cell activity and homeostasis.
What is osmolality?
The measure of solute concentration in a solution (osmoles per kg of solvent).
What direction does water move during osmosis?
From low solute concentration (high water) to high solute concentration (low water).
What is a hyperosmotic solution?
A solution with higher solute concentration compared to another.
What is a hypoosmotic solution?
A solution with lower solute concentration compared to another.
What does ‘isoosmotic’ mean?
Two solutions have the same solute concentration.
What is an osmoregulator?
Maintains internal balance, even if environment changes.
What is an Osmoconformer?
Body fluid concentration matches the environment.
Which animals are usually osmoconformers?
Most marine invertebrates.
Which animals are typically osmoregulators?
Most freshwater and terrestrial animals.
Why is ECF (extracellular fluid) used for osmoregulation, not ICF (intracellular fluid)?
Because ECF is more stable and less sensitive to small volume or ion changes.
What toxic substance is produced during protein and nucleic acid metabolism?
Ammonia (NH₃).
Why must ammonia be excreted quickly?
It’s very toxic, can affect pH, disrupt membranes, and damage the brain.
What are the three main forms of nitrogenous waste in animals?
Ammonia, Urea, Uric acid.
Which animals excrete ammonia?
Aquatic invertebrates and bony fish (ammoniotelic animals).
Which animals excrete urea?
Mammals, amphibians, and cartilaginous fish (ureotelic animals).
Which animals excrete uric acid?
Birds, reptiles, insects (uricotelic animals).
Which nitrogenous waste is the most water-saving?
Uric acid.
Which waste form is the least energy-costly but needs the most water?
Ammonia.
Why do birds and reptiles produce uric acid?
To conserve water in dry environments and allow for safe waste storage in eggs.
What is the functional unit of the kidney?
The nephron.
What are the three main processes in urine formation?
Filtration, Reabsorption, Secretion.
What is ultrafiltration?
Filtering of blood in the glomerulus to form primary urine.
What is reabsorption in the nephron?
Moving useful substances (e.g., glucose, Na⁺) from the tubule back into the blood.
What is secretion in the nephron?
Moving waste substances from the blood into the tubule to be excreted.
What fluid does the body mainly use for osmoregulation?
Extracellular fluid (ECF), like blood and interstitial fluid.
Why not regulate with intracellular fluid (ICF)?
It’s too sensitive—small changes can mess up proteins.
What are perturbing solutes?
Solutes that mess up proteins (e.g., Na⁺, K⁺).
What are compatible solutes?
Solutes that don’t harm proteins (e.g., glucose, glycerol).
What are counteracting solutes?
Solutes that cancel out the bad effects of others.
Where does filtration happen in the nephron?
In the renal corpuscle (glomerulus + capsule).
What part of the nephron makes urine more concentrated?
The Loop of Henle and collecting duct.
What hormone controls water reabsorption in the collecting duct?
ADH (antidiuretic hormone).
How much blood gets filtered per day?
About 180 liters.
How much of that filtrate becomes urine?
Only about 1%—the rest is reabsorbed.
What is a juxtamedullary nephron?
A nephron with a long loop, great for concentrating urine.
What is a cortical nephron?
A nephron with a short loop, more common in humans.
What’s special about uric acid in bird/reptile eggs?
It’s non-toxic and solid, so it won’t poison the embryo.
Which animals use ammonia for excretion?
Aquatic animals like fish and invertebrates.
Which animals use urea?
Mammals, amphibians, and sharks.
Which animals use uric acid?
Birds, reptiles, and insects.
Which is more energy efficient—osmoconforming or regulating?
Osmoconforming uses less energy.
What is a hydrostatic skeleton?
Fluid-filled compartments that muscles squeeze to create movement (e.g., worms, cnidarians).
What is an exoskeleton?
A hard outer covering that muscles attach to; common in arthropods like insects.
What is an endoskeleton?
Internal support system made of bone or cartilage (e.g., vertebrates).
What is the exoskeleton of arthropods made of?
Chitin (a strong carbohydrate).
What is the endoskeleton of vertebrates made of?
Mostly calcium phosphate and protein fibers.
What are the two parts of the human skeleton?
Axial skeleton – skull, spine, ribs
Appendicular skeleton – arms, legs, hips, shoulders.
What are the three types of muscles?
Skeletal muscle – for movement
Cardiac muscle – in the heart
Smooth muscle – in organs.
Where does a muscle cell get its signal to contract?
From a motor neuron at the neuromuscular junction (NMJ).
What neurotransmitter is released at the NMJ?
Acetylcholine (ACh).
What happens when a muscle fiber is activated?
An action potential travels into the muscle and releases Ca²⁺ from the sarcoplasmic reticulum.
What is the role of calcium (Ca²⁺) in muscle contraction?
It allows myosin to bind to actin so the muscle can contract.
What theory explains how muscles contract?
The sliding filament theory – actin and myosin slide past each other.
What is the smallest functional unit of a muscle?
A sarcomere.
What happens to the sarcomere when the muscle contracts?
It gets shorter – the H-zone and I-band shrink.
What molecule is needed for the muscle to relax?
ATP – it helps detach myosin from actin.
What happens if there’s no ATP in muscle cells (e.g., after death)?
Muscles stay stiff – this is called rigor mortis.
Where is Na⁺ high and K⁺ high in a resting neuron?
Na⁺ is high outside
K⁺ is high inside
What pump helps maintain RMP?
The Na⁺/K⁺ ATPase pump.
What does the Na⁺/K⁺ pump do?
Moves 3 Na⁺ out and 2 K⁺ in, using ATP.
What other channels are always open?
K⁺ leak channels, which let K⁺ leave the cell.
What is depolarization?
When the inside of the cell becomes less negative (more positive).
What is hyperpolarization?
When the inside of the cell becomes more negative than normal.
What triggers an action potential?
A stimulus that pushes the membrane potential past threshold.
Where do APs start?
At the axon hillock.
What kind of channels open during APs?
Voltage-gated ion channels.
What happens during depolarization?
Voltage-gated Na⁺ channels open, and Na⁺ rushes in.
What happens at the peak of the AP?
Na⁺ channels inactivate, and K⁺ channels open.
What happens during repolarization?
K⁺ leaves the cell, making the membrane more negative again.
What causes hyperpolarization?
K⁺ channels stay open too long, so extra K⁺ leaves.
How does the cell return to resting state?
K⁺ channels close, and the Na⁺/K⁺ pump restores balance.
What does Ca²⁺ do at the synapse?
Triggers the release of neurotransmitters into the synaptic cleft.
Where is Ca²⁺ high during rest?
Outside the cell.
What happens when Cl⁻ enters a neuron?
The inside of the neuron becomes more negative (hyperpolarized), making an action potential less likely.
What kind of signal is caused by Cl⁻ entry into a neuron?
An inhibitory postsynaptic potential (IPSP).
Which neurotransmitter opens Cl⁻ channels in the brain?
GABA (gamma-aminobutyric acid), an inhibitory neurotransmitter.
Why does Cl⁻ entry make it harder for a neuron to fire?
Because it moves the membrane potential farther from threshold, decreasing the chance of an action potential.
What happens when a neurotransmitter binds to postsynaptic receptors?
Ion channels open, allowing ions to move in or out of the postsynaptic neuron.
What is a postsynaptic potential (PSP)?
A change in the membrane potential of the postsynaptic cell due to ion flow.
What does EPSP stand for and what does it do?
Excitatory Postsynaptic Potential; makes the inside of the neuron more positive and closer to threshold.
What ion flow causes an EPSP?
Sodium (Na⁺) flows in.
What does IPSP stand for and what does it do?
Inhibitory Postsynaptic Potential; makes the inside of the neuron more negative and further from threshold.
What ion flows cause an IPSP?
Potassium (K⁺) flows out or Chloride (Cl⁻) flows in.
Are PSPs graded or all-or-none like action potentials?
PSPs are graded.
What does the strength of a PSP depend on?
The amount of neurotransmitter released and the number of receptors activated.
What happens to PSPs over distance?
They weaken, especially across the dendrite.
What is summation in terms of PSPs?
The combining of multiple EPSPs and IPSPs at the axon hillock.
What happens if total depolarization at the axon hillock reaches threshold?
An action potential is triggered.
What is temporal summation?
Multiple PSPs arrive in quick succession from one synapse.
What is spatial summation?
PSPs from multiple synapses arrive at the same time.
What is a preganglionic neuron?
A neuron that goes from the CNS to a ganglion.
What is a postganglionic neuron?
A neuron that goes from a ganglion to the target organ.
What is the first step in sensory processing?
Sensory reception by receptors (transducers) detecting stimuli.
What is sensory transduction?
Conversion of a stimulus into a change in membrane potential in sensory receptors.
What are the 3 structural types of sensory receptors?
Free nerve endings, enclosed nerve endings, and specialized sensory cells that synapse with neurons.
What does a strong stimulus cause in a neuron?
More frequent action potentials and more neurons activated.
What ions are involved in creating receptor potentials?
Na⁺, K⁺, and Ca²⁺.
What are mechanoreceptors?
Receptors that detect physical deformation like pressure or vibration.
What are the 5 main categories of sensory receptors?
Mechanoreceptors, thermoreceptors, photoreceptors, chemoreceptors, and nociceptors.
What are the two types of photoreceptors in the retina?
Rods (low light) and cones (color vision).
What protein do rods contain?
Rhodopsin, made of retinal + opsin.
How many types of cone photopsins do humans have?
Three, for red, green, and blue light.
Where do visual signals go after the retina?
To the brain via the optic nerve, crossing at the optic chiasma.
What is the difference between taste and smell detection?
Taste detects food molecules on contact; smell detects airborne chemicals.
What are chemoreceptors and what do they respond to?
Receptors that detect chemicals like oxygen, CO₂, and tastes/smells.
How do chemoreceptors send signals?
Binding of a chemical triggers neurotransmitter release and an action potential.
What do free nerve endings detect?
Light touch
What do Meissner’s corpuscles detect?
Light touch, surface vibrations
What do Pacinian corpuscles detect?
Deep pressure, high-frequency vibrations
What do Ruffini endings detect?
Deep pressure, skin stretch
What are statocysts and what do they do?
Found in aquatic invertebrates; use sensory hair cells that generate APs when moved to detect body orientation.
What is the vestibular apparatus and its components?
A balance organ in the inner ear with:
• Three semicircular canals – Detect head rotation
• Utricle and saccule – Detect linear acceleration and head position.
What is the function of the outer ear (pinna)?
Concentrates and directs sound waves into the auditory canal.
What bones are in the middle ear and what do they do?
Malleus, incus, and stapes; transmit vibrations from the tympanic membrane to the oval window of the inner ear.
What is the function of the inner ear (cochlea)?
Converts sound vibrations into electrical signals via hair cells in the organ of Corti.
How do sound waves become neural signals?
Vibrations pass from tympanic membrane → ossicles → cochlea fluid → hair cells in organ of Corti → APs to the brain.
What is retinal and where is it found?
A pigment derived from vitamin A, found in photoreceptors; absorbs light energy for vision.
What are the differences between simple and complex eyes?
• Simple eyes (ocelli): Detect light/dark only; no image formed
• Complex eyes: Form detailed images; detect shape, color, motion.
What is a compound eye and which animals have it?
Found in arthropods; composed of ommatidia (individual visual units) that form a mosaic image sensitive to motion.
What is a single-lens eye and how does it work?
Found in vertebrates; light enters through the cornea, passes through the lens, and is focused onto the retina where photoreceptors are.
What is visual accommodation and how does the lens adjust?
• Near objects: Ciliary muscle contracts, lens becomes round
• Far objects: Ciliary muscle relaxes, lens flattens.
What are rods and cones and what do they detect?
• Rods: Detect low light (black/white vision)
• Cones: Detect color (blue, green, red wavelengths).
What is rhodopsin and where is it found?
A pigment in rods made of opsin and retinal; changes shape when exposed to light, triggering a signal.
What are the three parts of a photoreceptor?
- Outer segment – Contains pigment discs
- Inner segment – Handles metabolism
- Synaptic terminal – Releases neurotransmitters.
What do chemoreceptors detect in the environment?
Taste (gustation), smell (olfaction), and internal chemical levels (e.g., oxygen, carbon dioxide, H⁺).
Where are taste receptors located in insects, and what do they detect?
In sensilla on antennae, mouthparts, and feet; detect sugars, salts, amino acids, and other chemicals.
