Sensors: Detect Changes in environmental conditions Use Receptor Cells Sensory Physiology Sensors: Detect Changes in environmental conditions Use Receptor Cells

Transduction Conversion of environmental change into an electrical signal Receptor responds to stimulus by releasing neurotransmitter to a neuron Neuron sends message to brain to be interpreted

Types of Environmental Stimuli Chemoreception Mechanoreception Photoreception

Chemoreception Detection of chemical types and concentrations 2 Types: 1. Taste Receptors – detects chemicals dissolved in water within the mouth 2. Smell- Olfactory Receptors – Sense chemicals in the air

Taste Buds (Taste Receptors) MAMMALS, REPTILES, BIRDS: Allows animal to detect and identify dissolved chemicals Found mainly on the upper surface of the tongue Pits found on tongue consist of sensory cells Every sensory/receptor cell has a tiny hair called a microvilli, that project into the saliva Chemicals come into contact with these hair receptors These receptors send messages along nerves to the brain Flavors are then interpreted

Taste buds microvilli Sensory Cells Taste Bud

Taste Buds

Chemoreceptors- Taste/Smell INVERTEBRATES: Use receptors found on Antennae Use receptors found on Legs/Feet

Olfactory Receptors What do animals use their sense of smell for? Locate Food Mark Territory Identify their own offspring Presence and condition of a potential mate

Olfactory Receptors (Distance Receptors) The organ of smell is the olfactory organ Located in the nose Responds/Detects chemicals in the air Consists of nerve cells that have tiny hairs on the surface Animal Breathes Sense cells respond to molecules Impulse fired and sent to the brain for interpretation

Olfactory Organ Olfactory Organ Nerve Fibers

Snakes/Lizards Tongues Tongue collects chemicals then retracts swab chemicals over vomeronasal organ (Jacobson’s organ) Chemical/pheromone perception

Insect Antennae Pheromone Reception

Mechanoreceptors Detection of Mechanical Energy and Force – Tactile (touch and pressure) – Equilibrium (gravity and acceleration) – Vibrations (sound)

Tactile (Touch) Touch is an important sense because it provides important information about: Proximity of food Predators Environmental features

Tactile Receptors Insect Receptors Vertebrate Receptors Bristle/hair receptors Vertebrate Receptors Nerve endings in skin are sensitive to touch and pressure The roots of hairs may also be well supplied with sensory receptors that inform the animal that it is in contact with an object Whiskers are modified hairs

Whiskers – Tactile Receptors

Tactile (Touch) Tactile receptors are not evenly distributed over the animal's surface. They are in higher concentration, and therefore closer together, on critical surfaces.

Tactile Receptors PAIN: Receptors that sense pain are found in almost every tissue of the body. Receptors allow animals to respond to tissues that are dangerously hot, cold, compressed or stretched, or that there is not enough blood flowing into them.

General senses in the skin Pain Receptor Cold Temperature Receptor Touch Receptor Touch Receptor Pressure Receptor

Equilibrium: Hair Cells located deep inside the ear They tell you if your head is tilted or if you are standing on your head. (orientation relative to gravity) vibrations bend “hairs” (stereocilia) alters release of neurotransmitter to sensory neurons sent to the brain

Hair Cells Located in the Inner Ear

Equilibrium: Vertebrate Vestibular Organs Fluid-filled compartments in the inner ear Semi-circular canals - Head moves, liquid in canals slosh around and moves the tiny hairs that line each canal - Hairs translate message into nerve impulses that are sent to the brain - Brain tells body how to stay balanced

Equilibrium: Invertebrate Statocysts Central statolith stimulates different hair cells based on orientation to gravity

Vibration Vertebrate Cochlea – Elongate structure containing hair cells – Fluid pressure waves induce vibration of the basilar membrane – Stimulates hair cells which triggers electrical impulses to the brain.

Passage of Sound through the Ear

Vibrations: Insect “Ears” A Frog is a Vertebrate Tympanic Organs Terminal Cerci Johnston’s organ – Wind receptor – May be tuned to specific frequencies Tympanic Organ

Vibrations: Lateral Lines Fish and aquatic amphibians Hair cells distributed along lateral line • Detect vibrations in water and flow of water

Photoreceptors VISION: Perception of electromagnetic radiation Animals are only able to use the visible portion of the electromagnetic spectrum

Reception of visual signals Light enters the eye specialized cells, photoreceptors, may be stimulated by particles of light Photoreceptors in the retina are triggered 1. rods - light intensity 2. cones - color Color perception: brain compares outputs of different photoreceptor types.

Parts of the Eye Cornea: A tough, clear covering over the iris and pupil that helps protect the eye. Sclera: The thick, tough, white outer covering of the eyeball. Iris: A muscle that controls how much light enters the eye. Colored portion of the eye Aqueous Humor: Fluid that helps the cornea keep its rounded shape. Pupil: A hole in the center of your iris that allows light in. Lens: Focuses light on the retina Vitreous Humor: Thick, clear jelly that helps give the eyeball its shape. Retina: A layer of photoreceptor cells Connected to the brain by the optic nerve Rods: light intensity Cones: Color

The Eye Vitreous Humor Sclera Iris Optic Nerve Cornea Pupil Lens Tapetum Retina Iris

Advanced Eyes: Tapetum Layer of tissue immediately behind the retina It reflects visible light back through the retina Increases the light available to the photoreceptors Provides superior night vision Found in many vertebrate animals, not humans

Time for Eye Dissection!!!!