How do we sense our Environment ? : Dr. Aman Biswas How do we sense our Environment ?
The five senses : The five senses Sight
Hearing
Touch
Smell
Taste
A classification attributed to Aristotle
Slide 3 : Additional senses of ours
Pain……..nociception,
Balance..equilibrioception (Acoustoception),
Joint motion and acceleration.. Proprioception and Kinesthesia
Temperature differences…Thermoception and Sense of time
Direction..Magnetoception
Interoceptive senses
Sight : Sight Ability of the brain and eye to detect electromagnetic waves
Within the visible spectrum of light
Neuroanatomists generally regard it as two senses, given that different receptors are responsible for
the perception of colour (the frequency of photons of light) and
brightness (amplitude/intensity - number of photons of light).
What is Stereoscopic Vision ? : What is Stereoscopic Vision ? Perception of depth
Of primates
Regarded as post-sensory function of brain
Hearing : Hearing Audition is the sense of sound perception.
A mechanical sense.
In humans, this perception is executed by tiny hair fibres in the inner ear , Organ of Corti
Tectorial membrane vibrates in response to changes in the pressure exerted by atmospheric particles within a range of 20 to 22000 Hz.
Taste : Taste Gustation is one of the two main "chemical" senses.
Four types of tastes that “taste buds" detect.
Sweet
Salt
Sour
Bitter
Slide 11 : A fifth receptor, for a sensation called umami which detects the glutamate amino acid
A flavour commonly found in meat and in artificial flavourings such as monosodium glutamate reported by Dr. Kikunae Ikeda .
Slide 13 : Chorda tympani
Smell : Smell Olfaction a"chemical" sense.
Hundreds of olfactory receptors, each binding to a particular molecular feature.
Odour molecules excite specific receptors
= molecule's smell.
Slide 15 : Richard Axel and Linda Buck showed how our sense of smell works. For their discoveries of odorant receptors and the organization of the olfactory system they got Nobel prize 2004
Slide 16 : Olfactory system
Balance and acceleration : Balance and acceleration Vestibular sense is the sense which allows an organism to sense body movement, direction, and acceleration and to attain and maintain perfect equilibrium and balance.
The organ of equilibrioception is the vestibular labyrinthine system found in both of the inner ear.
Technically this organ is responsible for sensing, angular moments, gravity and linear acceleration .
Balance and acceleration : Balance and acceleration The statoacoustic nerve (VIII) conducts information from
the three semicircular canals corresponding to the three spatial planes
the utricles and
the sacculus.
Slide 19 : The ampulla of the three semicircular canals each contain a structure called a crista.
These bend in response to angular momentum or spinning.
The saccule and utricle, also called the “otolith organs",
They sense linear acceleration and thus gravity.
Otoliths are small crystals of calcium carbonate
Provide the inertia needed to detect changes in acceleration or gravity.
How do we sense Temperature ? : How do we sense Temperature ? Thermoreception is the sense of
heat and
the absence of heat (cold)
By the cutaneous receptors.
The thermoceptors in the skin pass signals to hypothalamus which provide feedback on internal body temperature.
Kinesthetic sense : Kinesthetic sense Proprioception, provides the parietal cortex of the brain with information on the relative positions of the parts of the body.
Proprioception and touch are related in subtle ways
Pain : Pain Nociception signals near-damage or damage to tissue.
Algesi (pain receptors) are…
Cutaneous
(skin)
Somatic
(joints & bones) and
Visceral
(body organs). Cingulate
gyrus
Other internal senses : Other internal senses = Interoception
“Any sense that is normally stimulated from within the body”
Involve numerous sensory receptors ….
Stretch Receptors of lung
Cutaneous receptors in the skin
Respond to touch, pressure and temperature, vasodilation in the skin such as blushing.
Stretch receptors in the gut sense gas distension that may result in colic pain.
Slide 26 : When approximately 250 to 300cc of urine are in the bladder, the internal pressure within the bladder becomes strong enough to activate stretch receptors in the bladder wall.
When these stretch receptors send a message to the nervous system, sphincter close to avoid leakage. Stretch
receptors
Functions controlled by internal senses : Functions controlled by internal senses Stimulation of sensory receptors in the oesophagus while swallowing, vomiting or acid refluxes.
Stimulation of sensory receptors in the urinary bladder and rectum may result in sensations of fullness.
Stimulation of stretch sensors that sense dilation of various blood vessels may result in pain, for example headache caused by vasodilation of brain arteries.
Slide 28 : Advanced Animal Senses For many animal species the detection of odours or sounds eliciting attraction or avoidance reactions can be important for life or death.
What are Paranormal Senses ? : What are Paranormal Senses ? Radar, compasses and infrared detectors are all man-made contraptions that enable humans to stretch beyond our natural senses and allow us to detect things in our environment that we otherwise could not sense.
An examination of the sensory world of animals reveals that nature invented them long before we did!!!
Animals have the Sixth Sense : Animals have the Sixth Sense After the devastating tsunami struck the coastlines of the Indian Ocean on December 26, 2004, reports began to filter in that although many human bodies were recovered, virtually no animal carcasses were found. Why?
Did the animals sense the impending disaster?
A full hour before the waves struck, it was reported, elephants became agitated and began to wail.
Slide 31 : As the disaster neared, many broke their chains and headed for higher ground.
Flamingos left their breeding grounds and flew to the safety of the forests.
Leopards, tigers, wild boar, deer, water buffalo, monkeys and smaller mammals and reptiles all escaped unharmed.
Slide 32 : French zoologists, seeking a scientific explanation, suggested that it was a specialized advanced acoustic system that allowed the animals to hear the approaching giant surges of water.
What is ESP ? : What is ESP ? Extra-sensory perception
= Awareness of the world beyond the senses
='extrasensory perception'.
After all, the vomeronasal organ connects to the amygdala of the brain and relays information about the surroundings in essentially the same manner as any other sense.
Slide 34 : Animals have God gifted senses as they have to struggle to survive than we do
What are they?
Ecolocation
Infrared vision
Electric sense
Magnetic sense
Slide 35 : ECHOLOCATION
Ecolocation : Ecolocation Toothed whales, dolphins, bats and some shrews
They emit high-frequency sound pulses
In turn, detects the echoes produced by those sounds
Slide 38 : Special ear and brain adaptations enable them to build a three-dimensional picture of their surroundings, much like radar.
Ecolocation : Ecolocation Bats, for example, have enlarged ear flaps that gather and direct sound towards thin, supersensitive eardrums.
Bats : Bats Can detect warmth of an animal from about 16 cm away using its "nose-leaf".
Also finds food (insects) up to 18 ft. away and get information about the type of insect using their sense of echolocation.
Can hear frequencies between 3,000 and 120,000 Hz
Dolphins : Dolphins Dolphins also use echolocation for movement and locating objects.
Can hear frequencies up to at least 100,000 Hz
Slide 42 : INFRARED
VISION
Infrared Vision : Infrared Vision Rattlesnakes and other pit vipers
Use their eyes to see during the day.
But at night they use infrared sensory organs
To detect and hunt warm-blooded prey.
These infrared "eyes" are cuplike structures that form crude images as infrared radiation hits a heat sensitive retina.
Pit Vipers : Pit Vipers Pit-vipers have a heat-sensitive organ between the eyes and the nostrils about 0.5 cm deep.
This organ has a membrane containing 7,000 nerve endings that respond to temperature changes as small as 0.002-0.003 degrees centigrade.
A rattlesnake can detect a mouse 40 cm away if the mouse is 10 degrees centigrade above the outside temperature.
The tongue of snakes has no taste buds. Instead, the tongue is used to bring smells and tastes into the mouth.
Slide 47 : Detected by in the 1800s, Danish physician L. Jacobson.
Smells and tastes are then detected in two pits, called "Jacobson's organs", on the roof of their mouths.
Receptors in the pits then transmit smell and taste information to the brain.
Also termed the vomeronasal organ and vomeronasal pit
What is Flehmen reaction ? : What is Flehmen reaction ? Animals draw back their lips …to be "grimacing".
The action for examining scents left by other animals
Either of the same species or of prey
Helps expose the vomeronasal organ and draws scent molecules back toward it.
This behavior allows animals to detect scents
For example from urine, of other members of their species or clues to the presence of prey.
Electric Sense : Electric Sense Electric fields are used in numerous ways by animals.
Electric eels, skates and some rays
Have modified muscle cells
To produce an electric charge strong enough to shock and sometimes kill their prey. Image of Masashi Kawasaki with thanks
Strongly Electric Fishes : Strongly Electric Fishes • Electric Eel
• Electric Catfish
• Electric Rays Electric ray Electric eels
Weakly electric fish : Weakly electric fish Elephant-nose fish Knife fishes
Fishes that can only sense electricity : Fishes that can only sense electricity • Sharks
• Rays
• Skate
• Catfish
• Paddlefish
• Platypus (a mammal,
who is electro-receptive) Skates
Duck Billed platypus : Duck Billed platypus Has electric sensors in its bill that can detect 0.05 microvolts.
Other receptors in the bill are for touch and temperature detection.
Electric organ : Electric organ Contains electrically-excitable cells called 'electrocytes',
Receives simultaneous command signals from the brain to 'fire'.
At the moment of 'firing', the acts as a car battery.
This results in electric organ discharges (EODs) which are emitted into the surrounding water.
Slide 57 : There are two types of EODs; pulse type and wave type.
Those fish that are capable of high voltage discharge and a few weakly electric fishes are called pulse-type electric fishes and they discharge short electrical pulses intermittently.
The high voltage discharge can go up to around one ampere at 500 volts.
The remaining weak voltage emitting electric fishes are called wavetype.