Sensory Reception and Mechanoreceptors.
Pain Receptors/Nociceptors:
Pain Receptors/Nociceptors: detects stimuli that reflect harmful conditions such as extreme pressure or temp. By triggering defensive reaction, perception of pain serves as an important function. Chemical produced in an animals body sometime enhances the perception of pain. Ex: damaged tissues produce prostaglandin, which are local regulators of inflammation. They worsen pain by increasing nociceptor sensitivity to a noxious stimuli. Asprin and ibuprofen reduce pain by inhibiting prostaglandins to form.
Explain how sensory information is conveyed from sensory neurons to the CNS, including the role of gated ion channels and how a sensory stimulus is translated into an action potential.
All sensory processes begin with stimuli, and all stimuli represent forms of energy. A sensory receptor converts stimulus energy to a change in membrane potential. Therby regulating the output of action potentials to the central nervous system. Decoding of this info with the CNS results in sensation SENSORY RECEPTION & TRANDUCTION: A sensory pathway begins with sensory reception, the detection of a stimulus by sensory cells. Some sensory cells are neurons, some are not but they regulate neurons. Some exist singly.. Others are collected in a sensory organ. Sensory receptor: a sensory cell or organ or a subcellular structure that detects stimuli. Many sensory receptor detect stimuli from outside the body, such as heat, light, pressure, or chemicals. Activating a sensory receptor doesn't require a large amount of stimulus energy, Also, although animals use a range of sensory receptors to detect widely varying stimuli, the effect in all cases is to open or close ion channels. Ion channels either open or close when a substance outside the cells binds to a chemical receptor in the plasma membrane. Thus, letting ions flow in changing the membrane potential. The conservation of a physical or chemical stimulus to a change in the membrane potential of a sensory receptor is sensory transduction. The change in the membrane potential is the receptor potential. The potentials are graded potential. Thus their magnitude varies with the stimulus. TRANSMISSION: Sensory information travels through the nervous system as nerve impulses or action potentials. In sensory neurons, transducing the energy in a stimulus into a receptor potential initiate's action poteials that are transmitted to the CNS. Neurons that act directly sensory receptors produce action potentials and have an axon that extends into the CNS. Non-neuronal sensory receptors cell from chemical synapse with sensory (afferent) neurons and respond to stimuli by increasing the rate at which the afferent neurons produce action potentials. The size of a receptor potential increases with the intensity of the stimulus. In a sensory neuron, a larger receptor potential result in more frequent action potentials. For non-neural receptors, it resuts in more neurotransmitter to be releases. Processing of sensory information can occur before, during and after transmission of action potentials to the CNS. o Thus, the intergration of sensory information begins as soon as the information is received. PERCEPTION When action potentials reach the brain via sensory neurons, circuit of neurons process this imput, generating the perception. Preceptions such be colors, smells, sounds and taste are constructions formed in the brain and do not exist outside of it. Action potentials from sensory receptors travel along neurons that are dedicated to a particular stimulus. These dedicated neurons synapse with particular neurons in the brain or spinal cord. As a result, the brain distinguishes stimuli such as light or sound solely by the path along which the action potentials have arrived.
Chemorecptors?
Chemoreceptors: detect changes in the total solute concentration. They have receptors that transmit information about solute concentration and receptors that respond to individual kinds of molecules. Ex: osmoceptors in the mammalian brain, detect changed in total solute concentration of the blood and stimulate thirst when osmolality increases. Most animals have receptors for specific solutes.
Electromagneric Receptors?
Electromagnetic Receptors: detect forms of electromagnetic energy. Such as light, electricity and magnetism. Ex: the playpus has electroreceptors on their bill that are though to detect the electric field generated by the muscles of crustaceans, small fish and outer prey. Also, some fishes generate currents and then use electroreceptors to locate prey and objects that disturb the currents. & many animals use Earth's magnetic field lines to orient themselves as they migrate & this could be caused by magnetite.
Compare and contrast how body position and movement are detected in terrestrial and aquatic animals.
Equilibrium In Mammals The chambers called the utricle and saccule allows up to precieve postion with respect to gravity of linear movement. o Each of these chambers are situated in a vestibule behind the oval window, contains hair cells that project into a gelantinous material. Embedded in the gel are small calcium carbonate particles called otoliths. When you tilt your head, the otoliths press on the hair protruding into the gel. The hair cell receptors transform this deflection into a change in the output of sensory neurons, signaling the brain that you head is at an angle. This also helps you perceive acceleration. 3 fluid filled semicircular canal connected to the utricle detect turning of the head and rotational acceleration Within each canal the hair cells form a cluster, with the hair projecting into a gelatinous cap called a cupula. These canals also are arranged in 3 spatial planes that can detect angular motion of the head in any direction. If you spin in place, the fluid in each canal eventually comes to equilibrium and remains in that state until you stop. Here, the moving fluid encounters a stationary cupula, triggering the false sensation of angular motion that we call dizziness. Equilibrium in Aquatic Animals Many fishes and aquatic amphibians are able to detect low-frequency waves by means of a lateral line system along both side of their body. Water entering the later line system through numerous pores bends the cupula, leading to depolarization of the hair cells and production of action potentials. The fish perceives it's movement through water or the direction and velocity of water current flowing over it's body. The lateral line system also detects water movements or vibrations generated by prey, predators and other moving objects.
Hearing in Aquatic and other Animals?
Hearing in other vertebrate such as aquatic animals: Fish rely on several systems for detecting movement and vibration in their aquatic environment. One system involves a pair of inner ears that contain otoliths and hair cells. Fish have no ear drum, cochea or opening to the outside of the body. Instead, the vibrations of the water caused by sound waves are conducted to the inner ear through the skeleton of the head. Some fishes also have a series of bones that conduct vibrations to the inner ear from the swim bladder. Hearing in Others In the ear of a frog or toad, sound vibrations in the air are conduced to the inner ear by a tympanic membrane on the body surface and a single middle ear bone. Birds and reptiles are also the same, but they have a cochlea.
Heating in Mammals?
Hearing: Vibrating objects create pressure waves in the surrounding air. In hear the ear transduces this mechanical stimulus into nerve impulses that the brain perceives as sound. To hear music, speech or other sounds in the environment, hair cells, sensory cells with hair like projections that detect motion. Before the vibration waves reach hair cells, they amplified and transformed by several accessory structures. First the structures in the ear convert the vibrations of moving air into fluid. Moving air that reaches the outer ear causes the tympanic membrane to vibrate. The three bones of the middle ear transmit these vibration to the oval window, a membrane on the cochlea's surface. When one of the bones, the stapes vibrates again the oval window it creates pressure waves in the fluid inside the cochlea. Upon entering the vestibular canal, fluid pressure waves push down on the cochlear duct and basilar membrane. The basilar membrane and attached hair cells then vibrates up and down. The hair projecting from the hair cells are deflected by the fixed tectorial membrane which lies above. With each vibration the hairs bend first in one direction and then the other causing ion channels in the hair cells to open or close. Bending in one direction depolarizes the hair cells, increasing the neurotransmitter release and the frequency of action potentials directed to the brain along the auditory nerve. Bending the hairs in the other direction hyperpolarizes hair cells, reducing the neurotransmitter release and the frequency of auditory nerve sensation After propagating through the vestibular canal, pressure waves pass around the apex of the cochlea and dissipate as they strike the round window, The damping of sound waves resets the apparatus for the next vibrations that arrive The ear captures information about the volume and pitch. Volume is determines by the amplitude, or height of the sound wave. A large amplitude wave causes more vigirious vibration of the basilar membrane, greating bending the hairs on the hair cells, and more action potentials in the sensory neurons. Pitch is determine by a sound wave's frequency, the number of vibrations per unit of time. The detection of sound wave frequency takes place in the cochlea and relies on the asymmetric structure of that organ. The cochlea can do this because the basilar membrane is not uniform in length. It is relatively narrow and stiff at the base of the cochlea near the oval window and wider and more flexible at the apex. Each region is connected by axons to a different location in the cerebral cortex. o When a sound waves causes vibration of a particular region of the basilar membrane, a specific site in our cortex is stimulate and we perceive sounds of a particular pitch.
Mechanoreceptors?
Mechanoreceptors: sense physical deformation caused by forms of mechanical energy such as pressure, touch, stretch, motion and sound. Consist of ion channels that are link to structures that extend outside the cell, such as hair (cilia) as well as internal cell structures, such as cytoskeleton. Bending o stretching of the external structure generates tension that alters the permeability of the ion channels. Which can result in a depolarization or hyperpolarization. Vertabrate stretch receptor detects muscle movement. This triggers the knee-jerk reflex. Vertabrate stretch receptors are dendrite of sensory neurons that spiral around the middle of small muscle fibers. When the muscles fibers are stretched, the sensory neurons depolarize, triggering nerve impulse that each the spinal cord, activate motor neurons & generate a reflex response. Mechanoreceptors that are dendrites of sensory neurons are responsible for mammalian sense of touch. Touch receptor are embedded in the layers of connective tissue. The structure of the connective tissue and the location of the receptors affect the type of mechanical energy. Receptors that detect a light touch or vibration are close to the surface of the sink. Receptor that respond to stronger pressure are deeper in the skin.
Explain the function of sensory amplification and adaptation, how intensity of sensation is coded, and how sensations are differentiated among by an animal (i.e., how does it "know" its skin is hot, dry, painful?) Look into this more!
The transduction of stimuli by sensory receptors is subject to two types of modification - amplification and adaptation. Amplification: the strengthening of a sensory signal during transduction. Ex: an action potential conducted from the eye to the human brain has about 100,000 times as much energy as the few photons of light that triggered it. Amplification that occurs in sensory receptors often requires signal transduction pathways involving second messengers. These pathways include enzyme that catalyze reaction, thus amplify signal strength thru the formation of many product molecule by a single enzyme molecule. Amplification can also take place in accessory structure of complex sense organ. Ex: when the pressure associated with sound waves is enchanced higher than 20-fold before reaching receptor in the innermost part of the ear. Sensory Adaptation: a decrease in responsiveness. This happens with continued stimulation occurs. Without this, you would be constantly aware of every beat of your heart. This also enables you to see, hear and smell changes in the environment that vary widely in stimulus intensity.
Thermoreceptors:
Thermoreceptors: detect heat and cold. Ex: some venomous snakes rely on thermorecptors to detect the infrared radiation radiation emitted by warm prey. The receptors are found on the snake's head. Human thermoreceptors are located on the skin and the anterior hypothalamus sends info to the body's thermostat to the post hypothalamous. .
Statoliths?
granules that sit at the low point in chambers bends cilia+ on the receptor cells in that location, providing the brain with information about the orientation of the body with respect to gravity.
statocysts?
where machanorecptors are locared.
