ZO 250 Lab - Final Practical

Highlighted "terms" are taken from the provided study guide

Good science writing

Plain/informal language (little to no jargon)

Narrative building/storytelling

Emotionally intriguing

CSE Citations

In text: Author-Date

Bibliography: Author, date, title, publisher, date accessed, URL

“Adorable ducks tiptoe past dancing unicorns”

Motor neuron structure

Neuromuscular junction

Space between the synapse and the muscle fiber— ACh is transported by vesicles to the presynaptic membrane, where ACh is released into the neuromuscular junction.

ACh binds to nicotinic receptors on muscle cell, allowing Na+ ions to depolarize the postsynaptic cell. If an AP occurs, Ca+ ions are released and electrical currents are generated → Muscle fiber activation

If ACh does not bind to nicotinic receptors, it is metabolized by AChE into acetate and choline.

EMG indirectly measures the rate of APs/release of acetylcholine into NMJ.

Motor units

A single motor neuron and the muscle fibers it controls

The more units are activated, the greater the force will be.

The number of fibers within a unit (& thus the # of fibers innervated by a single motor axon) varies a ton across muscle types.

Variation results from different degrees of control over contraction force in different structures.

Finger muscles have “many fewer” muscle fibers/motor units than biceps.

Isotonic vs Isometric contractions

Isotonic: Muscle experiences same forces, but shortens and lengthens (“same tension”, pushups)

Isometric: Muscle length remains same throughout (“same measure”, planking)

Electromyography

Directly measures electrical activity of skeletal muscles in mV

Indirectly measures rate of APs/ACh release into NMJ

3 features of skeletal muscle contraction

Muscle Tone: Continuous state of low-level activation (maintains readiness)
Motor Unit Recruitment: Increases in the number of motor units activated within a muscle to generate force

Fatigue: Decreases in contraction strength due to continued activation

Parts of the eye

Cornea: window of the eye, controls/focuses light entry

Anterior chamber/aqueous humor: focuses light on retina/provides nutrition

Iris: restricts light entry (pupil is just a "hole” in iris)

Ciliary body/suspensory ligaments: expand and contract the iris to control light flow into pupil

Vitreous chamber/vitreous humor: provides structure, absorbs shock

Sclera: tough outer coating of eyeball

Retina: photoreceptive layer of eye

Fovea: part of retina containing only cones, allows for sharp central vision

Optic nerve: communicates visual information to the brain

Brain bits - Cerebellum, arbor vitae, gyri/sulci, & olfactory bulb

Cerebellum: Fine motor control, memory of movement patterns

Arbor vitae: transmits info to/from cerebellum

Gyri/sulci: boost surface area— sulci separate regions but gyri do not

Olfactory bulb: smell, limbic system

Brain bits - Pineal gland, corpus callosum, optic chiasm, & ventricles

Pineal gland: Hormone production/regulation

Corpus callosum: communication bw hemispheres

Optic chiasm: optic nerves cross/integration

Lateral ventricle/third ventricles: filled w CSF

Brain bits - Fornix, thalamus, hypothalamus, infundibulum, & pituitary

Fornix: transmits info from hippocampus to mammillary bodies and thalamus

Thalamus: principle sensory info filter, relays to cerebral cortex

Hypothalamus: autonomic nervous system, endocrine system

Infundibulum: pathway for hormones from hypothalamus to posterior pituitary for release into bloodstream

Pituitary: releases/regulates hormones

Brain bits - Midbrain, pons, medulla oblongata, & spinal cord

midbrain: motor movement

Pons: connects midbrain/medulla oblongata

Medulla oblongata: roles vital for life

Spinal cord: pathway for messages bw body/brain

Brain subdivisions

Forebrain: olfaction, sensory integration, behavior coordination

Midbrain: coordinates reflex responses to auditory/visual stimuli

Hindbrain: vital processes

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Forebrain does sensory integration: “shower beFORE you STINK”

Midbrain coordinates reflex responses: “Many Cats Roar Relentlessly”

Comparative anatomy of brains

Lamprey: no cerebellum, shortest cerebral hemispheres/olfactory region

Shark: midsized cerebellum that partially covers optic tectum

Amphibian: smallest cerebellum

Bony fish: gap between cerebellum and medulla, largest optic tectum

Nonavian reptile: longest cerebral hemispheres/olfactory region

Bird: Foldy cerebellum, more visible pituitary

Mammal: Even more foldy cerebellum

Atria vs Ventricles

Atria accept blood from veins. These are the vena cava in pulmonary circuit on right side of the heart, and pulmonary veins in systemic circuit on left side of heart.

Ventricles pump blood out through the pulmonary artery and aorta. The right ventricle pumps blood to the lungs and is much less forceful than the left ventricle, which pumps blood to the rest of the body.

Atrioventricular vs semilunar valves

Atrioventricular: Between atria & ventricles… tricuspid and bicuspid (mitral)

Semilunar: Between ventricles & artery… aortic and pulmonary

Flow of blood through the heart

1. Pulmonary: Deoxygenated blood enters right atrium through superior vena cava, passes through AV valve to right ventricle, and out to the lungs.

2. Systemic: Oxygenated blood enters left atrium through pulmonary vein, passes through AV valve to left ventricle (more muscular), where it is dispersed to body through aorta.

EKG, heart rate, and the cardiac cycle

EKGs directly measure electrical activity in the heart.

P: atrial contraction QRS: ventricular contraction T: ventricular repolarization

Heart rate: 300/(# large squares between R waves)

Lub (systole/ventricular contraction) - PQ segment

Dub (diastole/ventricular relaxation) - ST segment

Sinoatrial node

Initiates an electrical sequence in the heart (natural pacemaker). The signal travels from the SA node to the AV node. Bundle of His carries signal down pathway into the ventricles.

In humans, this occurs ~60-100 times/minute.

Systole & Diastole

Systole (lub): Ventricular contraction (120 in 120/80), AV valves close

Diastole (dub): Ventricular relaxation (80 in 120/80), SL valves close

Spectrophotometry

Dyes absorb specific wavelengths of light, amount of absorption dependent on concentration.

We injected a known amount of dye into known volumes of fluid, then measured absorption of the dye in the roach using the same procedure.

Optical density vs transmittance

Optical density is proportional to concentration, which is proportional to 1/volume.

Density is inversely proportional to transmittance— The less light is transmitted, the greater optical density (light absorbance) will be.

Deriving a standard curve

We created a standard curve by creating a dilution series with vials of known concentrations of the same dye we used in the roach, and we used the curve as a ruler to measure the OD of an unknown sample.

Open vs closed circulatory systems

Open circulatory systems: Fluid freely bathes tissues, is a mix of oxygenated and deoxygenated

Closed circulatory systems: Blood contained in vessels, oxygenated separate from deoxygenated

Waste excretion in open circulatory systems

Malpighian tubules (“simplistic kidney”) — Hemolymph transports waste products here for waste excretion.

Arthropod circulatory system

Heart (long muscular dorsal tube) takes in blood from abdominal hemocoel, empties it into head and thorax.

Hemolymph flows slowly through tissues and back into the abdomen.

Insect circulation lab: Why didn’t we take OD values at zero time?

Malpighian tubules of insect remove dye at the same time it is mixing in the hemolymph, so a “true zero” reading is impossible.

Extrapolating using our standard curve gives us a theoretical value.

3 factors for efficient gas exchange

1. Large gas exchange surface area

2. Minimal distance to transport gas

3. Maintenance of diffusion gradients

3 innovations in mammalian respiration

1. Diaphragm

2. Vertically flexed vertebral columns

3. Loss of abdominal ribs

Active and passive respiration

During active respiration, the diaphragm contracts, ribs expand, and negative pressure forces air IN (inhalation).

During passive respiration, the lungs recoil from stretching and air flows back until rib and lung pressure are equal (exhalation).

Path of air through lungs

Sinuses

Pharynx

Larynx

Trachea

Bronchial tube

Lung > bronchiole > alveoli

Mammalian dive reflex

Slows breathing and heart rate (bradycardia, 10-25%)

Peripheral vasoconstriction (directs blood to vital organs, away from extremities)

Headgut organs

Oral cavity, throat, pharynx

Food procurement and initial processing/transport

Dental Formulae

Incisors (cutting): Canine (gripping): Premolar (grinding): Molar (grinding)

Formulae start from anterior maxilla: “Iguanas can’t play music”

2:1:2:3 in humans

Foregut organs

Esophagus: circular & longitudinal muscle, lined w/ epithelial cells

Stomach: region w/ gastric glandular mucosa which secretes pepsinogen & HCL - sphincters at both ends → one-way flow

Midgut organs

Small intestine, liver, pancreas

Small intestine

Midgut. Lined w/ villi & microvilli.

Major site for digestion of carbs, fat, protein

Divided into duodenum (digestion), jejunum (absorption), and ileum [“donuts don’t just appear”]

Mesentery: thin tissue holding intestines (blood supply & lymph)

Liver

Metabolism (cat/anabolism)

Macromolecules: Stores carbs/fats, processes proteins [“some cool frogs prefer pillbugs”]

Detoxification

Bile production (absorption of fats)

4 functions: “Mained monkeys don’t bite”

Bile

Stored in gallbladder + secreted into dudoenum

Bile interacts w/ fats in duodenum, then fats are absorbed in jejunum and ileum

Pancreas

Exocrine communication: produces bicarbonate to neutralize HCl in small intestine, produces enzymes

Endocrine communication: Glucagon and insulin

Hindgut organs

storage of digesta, retrieval of dietary or endogenous electrolytes & water

microbial fermentation in herbivores

Distinguished from midgut by epithelial morphology, change in diameter, or presence of sphincter

Organ sizes vary by diet type

Large intestine & ceca

Unique characteristics of bird digestive systems

Don’t have true teeth (masticate w/ beak and gizzard)

Crop: An expansion of the esophagus that stores food

Proventriculus: Glandular stomach

Gizzard: Muscular stomach (rocks here sometimes)

Paired ceca to aid in flight

Hindgut vs ruminant fermenters

Hindgut fermenters: fermentation in cecum, proximal colon. Less efficient, so sometimes engage in coprophagy (rabbits)
Ruminant fermenters: ferment in rumen before stomach… More efficient (cows)

Shark digestive tracts

Spiral valve (↑ surface area) and very short tract.

Oily liver (buoyancy — not needed in bony fish bc they have a swim bladder — target for poaching bc it contains squalene).

Rectal gland.

Carnivores, herbivores, and omnivores

Carnivores: Short GI tracts, 10-20x more acidic stomachs than omnivores and herbivores, and stomachs are larger/may have rugae.

Herbivores: Longer GI tracts for fermentation, often greatly expanded ceca, much less acidic stomachs

Omnivores: Intermediate gut length and morphology, much less acidic stomachs than hypercarnivores

Effect of diet on digestive structures

Stomach: Animals prone to consuming large amounts at one time may have gastric folds/rugae to allow for stretching, acidity 10-20x higher in hypercarnivores

Small intestine: Longer in herbivores

Cecum: Long in herbivores, reduced in carnivores. Paired in birds.

Large intestine: Longer in animals that require a lot of fermentation.