Sensory receptors What are the general functions of receptors? Reception Transduction Amplification Transmission Integration

Types of Receptors Mechanorecpetors – stimulated by mechanical energy Chemoreceptors – detect solute concentration differences Electromagnetic receptors – detect forms of electromagnetic energy Thermoreceptors – respond to hot or cold Pain receptors – naked dendrites in dpidermis of skin

Touch Sensory receptors in the skin receive the touch stimulus Mechanoreceptors in human skin are in the form of naked dendritesMechanoreceptors in human skin are in the form of naked dendrites Prostaglandins intensify the pain by sensitizing the receptors

Taste and Smell Chemoreceptors sense chemicals in the environment Olfactory receptors line nasal cavity Taste receptors respond to specific stimuli (sugar/ salt)Taste receptors respond to specific stimuli (sugar/ salt) Taste and smell are functionally similar: –Molecule dissolves in liquid to reach receptor –Head cold interferes with taste perception

Vision Eye cup in planaria Compound eye in insects Vertebrate eye Vertebrate eye and focusing mechanismsVertebrate eye and focusing mechanisms

Photoreceptors Cones – color vision, used in daytime, found at center (fovea) –Photopsins as visual pigment –Known as red, blue and green cones Rods – more sensitive to light, don’t distinguish color –Visual pigment rhodopsin –Rods absorb light shape change causes signal transduction pathway that leads to receptor potential in rod cell membrane

What sort of neuro- transmitters must be released from the rod cell to neurons in the dark?

Why are you temporarily blinded when you enter a dark movie theatre on a sunny day?

Visual integration: Receptive fields feed information to one ganglion cell Larger receptive fields result in a less sharp image Ganglion cells of fovea have small receptive fields

Left side of brain receives information from right visual field Right side of brain receives information from left visual field Feeds information to lateral geniculate nucleus These nuclei relay information to visual cortex (in cerebrum) Where do you actually see?

The Human Ear Where are sound waves collected? What is the role of the eustachian tube?

How are the sound waves conducted to the inner ear?

This cross section of the cochlea shows 3 canals Transduction of the impulse occurs in cochlea as wave vibrations are converted to membrane potential

Explain how the action potential is generated Organ of Corti and Tectorial Membrane

Describe how the cochlea distinguishes pitch. Where is pitch perceived?

How do the structures of the inner ear help to distinguish body movements? Why do you struggle with balance after spinning around for a few minutes?

Movement Different amounts of energy are expended on different means of transportDifferent amounts of energy are expended on different means of transport Skeletons: Hydrostatic skeleton allows for peristaltic movementHydrostatic skeleton allows for peristaltic movement Exoskeleton seen in arthropods Endoskeleton seen in chordates…

Muscles and Skeletons What are ligaments? Join bone to bone What are tendons? Join muscle to bone How do muscles cooperate in movement if they can only contract?

Skeletal muscles

Sliding filament theory As the muscle contracts which muscle bands stay the same and which get smaller?

Control of Muscle Contraction Why isn't the muscle always contracting?

T Tubule Contraction What neuro- transmitter initiates the muscle contraction?

Graded Contraction Contractions of muscle fibers are all or none How does the nervous system produce graded muscle contractions? –Vary the frequency of action potentialsVary the frequency of action potentials –Rate of stimulation that is very fast results in tetanusRate of stimulation that is very fast results in tetanus Motor units = single motor neuron and all of the muscle fibers it controls The neuron can cause many muscle fibers to contract at the same timeThe neuron can cause many muscle fibers to contract at the same time

Other Vertebrate Muscles Smooth muscle : –Lacks striations –Has less myosin than skeletal muscle –Found in walls of hollow organs (e.g. digestive tract organs) Cardiac Muscle: –Structurally similar to skeletal muscle –Differs in action potential generation: Action potentials spread throughout the heart through direct contact between cells