Animal Physiology Objectives Answers Unit 3

Answers Objectives-3, BIO 3360

SENSORY PHYSIOLOGY – I

A sensation is a conscious awareness of inside/outside environment. The receptor is the dendrite of the neuron or a separate cell that takes a stimulus and generates a potential – turns it into an electrical signal (generator potential). Receptor potentials indicate the depolarization in the receptor which is a graded potential or sometimes the receptor causes the release of neurotransmitter that affects the membrane potential of another neuron. It is termed a generator potential if it is a dendrite responding and a receptor potential if it is a separate cell responding. Stimulus transduction is how stimulus is turned into an electrical response; it occurs by opening or closing of membrane ion channels. Projection is the brain interpreting the original site of the stimulus at the location of the receptor. With an unchanging stimulus, adaptation is the decreasing or ceasing of any response to the stimulus by the receptor. Pain does not adapt. Convergence is the pooling of a pathway which causes you to lose localization and precision.
Stimulus strength, rate of change of strength of signal, summation of receptor potentials, adaptation, all influenced the size of the receptor potential.
The receptive field is the part of the body served by a particular afferent neuron; 2 point discrimination is the smallest area in which you are stimulating two different receptive fields and therefore is a measurement of the size of receptive fields. We are more accurate with small receptive fields like on the lips.
Strongly stimulated receptors inhibit those neighboring receptors that are weakly stimulated.

SENSORY PHYSIOLOGY – II – PHOTORECEPTION

Light is just a small part of the electromagnetic spectrum and we can only see about 350-750 nm wavelength waves. Refraction is the bending of the light wave so that it converges on one single focal point – hopefully where the photoreceptors are.
Plate; eyecup, camera eye, compound eye
Rods and cones are the receptors for vision. Cornea is the rounded transparent outer surface; lens is suspended by the ligaments from the ciliary body and separates the anterior from posterior cavities of eye, iris is a circular muscle anterior to the lens that contains the pupil, an opening, to allow light in, the retina is at the posterior part of the eye and contains rods and cones, the optic nerve takes the info from the rods and cones out of the eyeball to the brain. Macula lutea is a yellow spot on the retina containing a dip called the fovea centralis which is a dense packing of cones; the pigmented layer is the outer layer of the retina to help trap light and the optic disk is the blind spot where the optic nerve exits the eye.
Sympathetic is pupil dilation and parasympathetic is pupil constriction.
Opsin and Retinal are the main rhodopsin components and need Vitamin A for synthesis.
Sodium channels are open (due to intracellular cGMP) in the dark and sodium moves into the outer segment of the rod and outward movement of potassium in the inner segment; resulting in a resting membrane potential of -40mV. This causes the synaptic end of the rod to release glutamate which hyperpolarizes (is inhibitory to) the bipolar cell.
Light changes the chemical configuration of retinal from a cis to a trans configuration which then changes the opsin and activates tranducin. Transducin activates cGMP phosphodiesterase which breaks down cGMP to 5’GMP and closes the sodium channels and the membrane potential becomes more negative. Therefore less glutamate is released and the bipolar cell can depolarize which leads to the ganglion cell to depolarize too.
Fovea centralis is filled with cones and little convergence means precision of vision. Rods have a lot of convergence which decreases visual acuity.
Bleaching the breakdown of rhodopsin into retinal and opsin after light exposure and it take time for them to reassemble.
Rods are very sensitive to light, contain rhodopsin which needs vitamin A for synthesis, are peripheral and very numerous, see in black and white and convergence results in poor precision of image; cones are centralized, fewer in number, show little convergence and therefore precise vision and color and are not very sensitive to light.

SENSORY PHYSIOLOGY – III – MECHANORECEPTION

Mechanoreception is the ability to sense force and displacement. A soundwave is the energy due to vibration consisting of alternating pressure waves in the medium. In the utricle and saccule the otoliths are calcium carbonate crystals that move and stimulate the hair cells to detect head position and linear acceleration and deceleration. A statocyst is a group of receptor hair cells that work as an organ of equilibrium in response to movement as the statoliths move.
Hair cells can detect tiny movements along an axis and this leads to a membrane potential or the release of neurotransmitter to an associated afferent neuron.
At the apical end are the tiny microvilli that are sterocilia and the one larger cilium called the kinocilium. If they lean towards the kinocilium the hair cell depolarizes and if it leans the other way it hyperpolarizes.
Loudness is based on wave amplitude while frequency determines pitch.
External ear collects sound waves and funnels them into the ear canal which gets the tympanic membrane The tympanic membrane is the divider between external ear and middle ear. Auditory or Eustachian tube connects middle ear with throat for pressure equalization. The vibrating tympanic membrane causes the middle ear bones to vibrate and amplify the vibration with the malleus, incus and then the stapes (listed outer to inner). The stapes pushes on the scala vestibuli via the oval window and gets the perilymph fluid vibrating. The oval window is the divider between middle ear and inner ear. The inner portion is fluid filled and resembles a snail shell, is bony, and called the cochlea. Then the fluid in the scala vestibuli connects with the fluid in the scala tympani, which causes the basilar membrane to vibrate. The basilar membrane is the floor of the organ of Corti (spiral organ) which is filled with fluid called endolymph. The basilar membrane starts vibrating and causes the hair cells of the spiral organ to move and depolarize. The entire membranous portion of the cochlea, that is filled with endolymph, is called the cochlear duct.
These are fluids in the inner ear; in bony regions it is perilymph and internal to this – in membranous portions is the endolymph.
At the base of the cochlear duct the hair cells are short and respond to high pitch frequencies; at the apex the hair cells are long and respond to the low frequencies.
The vestibule is the bony portion of the inner ear that houses the membranous portions called the utricle and saccule. This part is responsible for detecting head position and linear acceleration and deceleration. The semicircular canals are 3 bony archways in each inner ear, that are lined with membranous portions called semicircular ducts. They detect rotational acceleration and deceleration.
The macula of the utricle and saccule has hair cells in endolymph with otoliths that move as the head or body moves. In the utricle and saccule these are calcium carbonate crystals that move and stimulate the hair cells to detect head position and linear acceleration and deceleration. There is a widened portion (ampulla) in the semicircular ducts which have hair cells for rotational acceleration and deceleration. These receptors are a typical hair cell in the ampulla within the semicircular ducts floating in fluid called the cupula (endolymph).

CIRCULATION – I – HEART

Both are striated with actin and myosin as repeating units, but cardiac muscle shows some branching and most important has intercalated discs. Single nucleus in cardiac muscle and many in skeletal muscle.
They interconnect all of the myocardium so it acts as a unit – passes electrical current from one cell to the next with gap junctions.
The SA node in the wall of the right atrium can spontaneously contract at a rate faster than all of the other myocardium. Thus, it sets the pace.
Basically it is an increased permeability to sodium and calcium ions in the pacemaker cells. They have a pacemaker potential in which calcium and sodium slowly flow into the cells resulting in depolarization, then calcium rapidly flows into the cell resulting in an action potential. • Contraction activated by increasing [Ca ⁺⁺] I . • Ca ⁺⁺ influx from the SR and from the ECF. • AP activates receptors in the T tubes allowing inward movement of Ca⁺⁺. • The influx of Ca ⁺⁺ from the ECF triggers the release of a larger amount of Ca ⁺⁺ from the SR.
SA node to both atria, AV node, AV bundle w/ its branches, Purkinje cells of myocardium.
Transport nutrients and waste, temperature regulation.
Closed systems always have the blood in an enclosed structure such as a blood vessel.
Birds and mammals have a left and right atrium as the upper chambers of the heart, and a left and right ventricle as the lower chambers of the heart.
P wave is atrial depolarization; QRS complex is ventricular depolarization and T wave is ventricular repolarization.

CIRCULATION – II – HEART MUSCLE PUMPING

Vena cava to RA through tricuspid valve to RV through pulmonary semilunar valve to pulmonary trunk and arteries to lungs to pulmonary veins to LA through bicuspid valve to LV through aortic semilunar valve to aorta.
Systole and diastole.
S1 is closure of AV valves and S2 is closure of semilunar valves.
CO = HR x SV. SV = EDV – ESV; more filling as in a slower heart rate of increase venous return will increase stroke volume; a more forceful contraction as with sympathetic stimulation or Frank-Starling effect will decrease end systolic volume resulting in a larger stroke volume.
Stretching of ventricular wall due to more blood leads to a more forceful contraction thus lowering the ESV.
Increased HR in sympathetic stimulation increases cardiac output and parasympathetic has the opposite effect.

CIRCULATION – III – FLOW AND BLOOD VESSEL TYPES

Flow is volume/time from high pressure to low pressure. F = P/R. Pressure is the force exerted by the fluid mainly from a hydrostatic pressure and it is highest in arteries and lowest in veins. Resistance is the difficulty of blood flowing and influenced by the radius of the blood vessel, the length of the vessel and the viscosity of the blood.
More viscous blood has more resistance. Longer vessels have more resistance. Decreased radius (R = 1/r4) has a lot more resistance, which would greatly decrease flow.
Arteries have the thickest wall and highest pressure and can vasoconstrict a lot due to the large amount of smooth muscle and elastic fibers in their walls. Arteries take blood away from the heart. Capillaries are the thin-walled blood vessels with only one layer of endothelium in their wall so that diffusion can occur. Veins take blood back to the heart and have the lowest pressure, a thinner wall than arteries, but have one-way valves to prevent backflow of blood. Veins have the lowest pressures and rely on breathing and skeletal muscle contraction to facilitate blood flow.
Laminar flow is smooth as in a vasodilation situation whereas turbulent is rough as in a vasoconstricted vessel in which blood moves in directions that are not straight.
Capillaries
Arteries have the thickest wall and highest pressure and can vasoconstrict a lot due to the large amount of smooth muscle and elastic fibers in their walls. Arteries take blood away from the heart. Capillaries are the thin-walled blood vessels with only one layer of endothelium in their wall so that diffusion can occur. Veins take blood back to the heart and have the lowest pressure, a thinner wall than arteries, but have one-way valves to prevent backflow of blood. Veins have the lowest pressures and rely on breathing and skeletal muscle contraction to facilitate blood flow.
Arteriole-highest resistance, venous system-reservoir, capillary-diffusion, veins-valves, artery-elastic recoil, veins-high capacitance.

CIRCULATION – IV – ARTERIOLES, CAPILLARIES, VEINS and REGULATION OF ARTERIAL BLOOD PRESSURE

Vasoconstriction is decreasing the vessel diameter, and increasing it is vasodilation. Lymphatics can carry away the water that accumulates in the interstitial spaces. They return the lymph to the bloodstream and are most similar to veins in their anatomy. Veins return blood to the heart, and are the blood reservoirs, have low pressures, larger lumen with thinner wall than artery; one-way valves, low resistance high capacitance vessels. Venules are just tiny veins. ADH (antidiuretic hormone) can increase blood pressure by increasing blood volume. It causes one to reabsorb water out of the kidney tubules back into the bloodstream, rather than urinating out that water.
Chemicals such as hydrogen, carbon dioxide and oxygen and metabolic byproducts.
Sympathetic stimulation can cause vasoconstriction; hormones such as angiotensin (vasoconstriction) and epinephrine (vasoconstriction & vasodilation depending on receptors).
Decreased blood flow to the kidney results in the release of renin which is an enzyme catalyzing the activation of angiotensinogen to angiotensin I which is converted to angiotensin II in the lungs and causes vasoconstriction leading to improved flow to the kidneys.
The three major types of capillaries are: continuous are most common; fenestrated allow filtration; sinusoidal have fenestrations too but also large gaps between the endothelial cells.
Diffusion, vesicle transport (endocytosis and exocytosis of larger molecules), bulk flow and mediated transport.
Low resistance due to large lumen and breathing and skeletal muscle contraction help move the blood and one-way valves keep it going forward.
MAP = CO x TPR
Increased volume leads to increased pressure.
Receptors are in the aortic arch and beginning of common carotid artery and if pressure drops they can lead to an increased cardiac output and vasoconstriction to return pressure to normal and this happens due to gravity which pulls all of the blood towards the ground.