Sensory systems

Categorized by:

1. nature of the stimulus, like mechanical, chemical light stimulus, and

2. where stimulus received, like outside (exteroceptors, such as the attention and skin temp receptors) or inside the body (interoceptors, like blood heat receptors).

     Transduction of sensory input into the signal. Means to “carry across”, signal transduced or Carried from the environment into the nervous signal.

Three sensory processes we cover

1. taste and smell (chemoreception)

2. gravity and movement

3. light


32.1 Taste perception and odor (chemoreception)

      Locate in mammal nozzle and mouth, fly feet, fish bodies, moth antennae.

     Papilla bumps on the tongue have taste buds down between. Sweet, sour, salty, and bitter. Several acts directly by ion channels, different acts indirectly. Other “taste” sensations, really smell.

     Smell received in the nasopharynx. Airborne molecules move into solution on most epithelial. the surface of the nasal passage. Approximately 1000 genes code for neuron receptors. “Fried onions” odor, not one receptor but a combination of the many odors registered in our mind together. Highly sensitive habituates rapidly (don’t notice a smell after a bit). Odor sensation has. relatively unfiltered route to higher brain centers.

Snakes more chemosensory-focused than us.


32.2 Response to gravity and movement:

      Registered in the internal ear. Three (3) semicircular canals loop in three planes at accurate angles. to each other, accountable for transduction of movement messages. Method: hair cells Deformed by a gelatinous membrane. The sensory system gives us a perception of gravity. and movement. because of physical response, not chemical binding.

Cochlea: bony, coil-shaped part of the receptor, where hearing occurs.

     Sound enters through the meatus, vibrates the membrane, moving three bones of cavum (malleus, incus, and stapes)against the fenestra of the vestibule opening before of cochlea. The cochlea has three fluid-filled ducts, one amongst these the organ of Corti. Sound waves in the air Go to vibration in the organ of Corti; fluid tickles hair cells, which register the movement along with the tissue layer in the cochlea. Different sound frequencies move different portions. of the tissue layer. deafness because of loss of hair cells. Humans normally smell over 300 odors during a day(Facts and Truth).

Transduction of sound accomplished performed with physical deformation, not chemical binding.


32.3 Vision:

Light enters the pupil, focused by a lens onto the retina.

Sclera: the hardened part behind the retina.

Optic nerves and neurons attached to the retina. The blind spot where cranial nerve attaches has. no receptors.

Two varieties of photoreceptors

  1. rods - black and white low-light vision, 1000000 in each retina in humans beings.

  2. cones - visual modality, work best under better illumination. 3 million in each retina.

Fovea: region of most acute vision, has most of the cones, few rods.

     Transduction process of sunshine to signal a molecular change, to light-absorbing molecule Called photopigment. Located in pigment discs of rods and cones in outer parts. The rod photopigment is termed rhodopsin, one has three photopigments, called photo opsins. This molecular change initiates pathways to lead to impulse in downstream neurons leading to the vision centers in the brain. Parul Godiva.

     Each of the three photo opsins incorporates a different peak of sensitivity: blue, green, or red, and changes isometric form (from cisco trans) supported light from a specific wavelength range. Color blindness: inherited lack of 1 or more forms of these cones. Gene carried on the X chromosome, therefore more common in men than women.


32.4 Homeostasis:

     Is a vital a part of everyone's and everything's lives? Defined as dynamic constancy. of internal environment, maintenance of a comparatively stable environment inside an organism usually involving feedback regulation.

Homeostasis is maintained in the face of

   1. a varying external environment, or

   2. a non-ideal, constant outer environs (as with the penguin).

Deals with temperature, pH, chemical concentrations, pressure, oxygen levels.

Occurs through feedback loops.

    Various forms: simple thermostat in the house turns off the heater when above a particular temperature, and on when below a specific temperature Involves stimulus, sensor, integrating center, effector and response.

    More efficient control has 2 (two) sensors and 2 (two) effectors. is antagonistic to every other, such as one side cools, the opposite side heats.

    Precise control through proportional control, not all-or-none, the furnace comes on a touch bit if the house a touch cold. Examples in humans: vasoconstriction, change in rate, shivering. Physiological responses for top body temp: blood goes to the body surface, sweating, behavioral changes (get out of the sun).

   Positive feedback loop: effector increases deviation from the point. Amplifies reaction. Like the blood coagulation process, muscular contraction during childbirth. Feedback must exist at some point for control.


32.5 Osmotic environments and regulations:

1. Marine invertebrates

      a) fully marine invertebrates (not intertidal or estuarine) some formers (set internal environment same as environment, no net flow of ions) during a stenohaline (narrow non-changing salt level) environment

      b) Coastal, intertidal, estuarine (iron levels fluctuate) invertebrates. Partly osmoconformers, partly osmoregulator during a euryhaline (wide salt level variation) environment (ex: shore crab, adjusts sometimes when salt levels in the environment get real low).

2. Freshwater animals. Here, the environment has lower solute concentrations than does. experiencing organisms, so water tends to flow in and solutes out.

      a) seafood (bony) dilute urine, and gills actively take up ions (NaCl)

      b) Freshwater invertebrates: same situation as seafood but with different structures

      c) Freshwater amphibians: progressive uptake of salts across their skin

3. Marine fishes: Here the environment features a higher solute concentration than does the organism so water tends to effuse and ions in.

      a) Bony fishes: actively release salts (NaCl) across gills, absorb water across the gut wall, their kidney (unlike mammalian kidney) is unable to come up with concentrated urine so glomerulus is decreased, active tubular secretion of MgSO4

     b) cartilaginous fishes (and coelacanth): blood retains urea and trimethylamine oxide to increase its osmolality to it of seawater

4. Terrestrial animals: here the problem is the loss of water to a drier environment and regulation of salt levels.

     a) water loss adaptations

     b) concentrated exception of salts and nitrogenous wastes

Hypoosmotic: having less osmotic potential than nearby fluid

Hyperosmotic: having more osmotic potential than nearby fluid

iso-osmotic: having equal osmotic potential than nearby fluid

Glomerulus: reduces the volume of kidney

Fish started in saltwater, spread to H2O, later re-invaded the salt-water environment.

Terrestrial animal water sources:

1. drinking

2. moist foods

3. from the breakdown of metabolic molecules like fats. (Desert kangaroo rats get 90% of their water from metabolism.)

Secretion of nitrogenous junks: from metabolism of amino acids, group should be removed in 1 (one) of three (three) basically interchangeable chemical stats:

1. ammonia (aquatic life)

2. urea (mammals)

3. acid (birds)

Ammonia very toxic, soluble, and cheap to supply. Easy to expel for bony fishes.

Urea: low toxicity, good solubility, more costly to lose because it contains other groups thereon. Must be released in solution, water cost.

Uric acid (white a part of bird poo) low toxicity, insolvable, secreted with little water (H2O) loss. more costly side groups lost than the others.

Mammalian kidney: Structure: fist-sized organ in the lower back. About 1/5 of blood from the aorta at any time is passing through the kidneys. Blood passes through the kidney repeatedly a day.

Nephron: structural and usefulness unit of the kidney.

Bowmans capsule: funnel-like opening, contains primary filter, the glomerulus (capillary vessel). Proximal convoluted tubule: receives stuff from Bowman's capsule.

Loop of Henle: descends and ascends

Vasa recta: capillaries that are surround the Loop of Henle.

Glomerulus: main filter of the nephron, located within the tissue layer Kidney properties and processes important to its function

1. Active shipping of solutes from one fluid to a different against an amount gradient. Na+ actively transported out of filtrate by cells of the thick ascending loop of Henley into the ECF.

2. Inactive motion of solutes and water from one fluid to a different (down a level gradient), motion of water and NACL out of a raining loop of Henley into interstitial fluid.

3. Differential permeability of cells in several regions of the nephron to movement of water and solutes, rising thick look is impermeable to water, degressive portion is permeable to water

4. Hormonal criterion of that permeability, antidiuretic hormone (ADH) increases permeability of collecting because of water, leading to reduced volume of filtrate and thus more concentrated urine.

5. Increasing amount solute concentration within the extracellular fluid of the kidney (urinary organ), from the cortex to the deepest medulla, preserved by a countercurrent multiplier mechanism.