Term
| ionotropic sensory detection |
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Definition
| the receptor protein itself is part of the ion channel and, by changing its conformation, opens or closes the channel pore. |
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Term
| metabotropic sensory detection |
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Definition
| the receptor protein is linked to G proteins that activate a cascade of intracellular events that eventually open or close ion channels. |
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Term
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Definition
Receptors ARE specialized ends (generally dendrites) of sensory neurons. (The sensory cell is also the afferent neuron carrying APs to the CNS.)Small receptor potentials are electrotonically spread to the spike initiating zone where, if the depolarization reaches threshold (generator potential), an action potential is generated.
The AP is then propagated to the CNS.
The amplitude of the receptor potential is dependant on the stimulus intensity. It is “graded”. |
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Term
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Definition
Consist of a separate receptor cell (often an epithelial cell) which synapses with the afferent (sensory) neuron. A graded (amplitude depends on stimulus intensity) receptor potential is generated, and is electrotonically spread to the synapse of the sensory cell with the sensory (afferent) neuron. The distance is short.
The amount of neurotransmitter released is dependant on the size of the graded receptor potential. |
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Term
| Stimulus Intensity Discrimination |
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Definition
The brain determines stimulus intensity by monitoring action potentential frequency coming from the particular sensory cells.
Variation in the frequency of APs delivered to the CNS by a given sensory receptor.
Variation in the # of receptors activated (recruitment of sensory units). |
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Term
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Definition
Internal and external chemicals
Taste and smell
pH, PCO2, PO2, glucose, etc.
Examples of the important role of chemoreceptors in animals.
- great sensitivity
- pheromones |
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Term
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Definition
Humans have 10,000 taste buds embedded in the epithelium of the tongue. Taste buds are replaced every few days, but the associated neurons live on.
Taste buds can distinguish sweet, salty, sour, and bitter tastes.
Recently the savory meaty taste umami has been added to the list of distinguishable tastes.
Saltiness receptors are ionotropic.
Sweetness and bitter receptors are metabotropic. Some fish have taste buds on the skin; duck-billed platypus have taste buds on the bill.
Many are in raised papillae, the small bumps on human tongues.
The outer surface of each bud has a pore that exposes the tips of sensory cells. Microvilli increase the surface area of the cells.
The sensory cells form synapses with dendrites of sensory neurons. They are secondary type sensory cells. |
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Term
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Definition
the sense of smell, also depends on chemoreceptors.
In vertebrates, olfactory sensors (1o) are neurons embedded in a layer of epithelial cells at the top of the nasal cavity.
The axons of these sensors project to the olfactory bulb of the brain.
The dendrites end in olfactory hairs at the surface of the nasal epithelium.
Molecules from the environment diffuse through nasal mucus to reach the surface of the olfactory hairs. |
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Term
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Definition
are cells that are sensitive to mechanical forces.
They are involved in many sensory systems, including skin sensations and sensing blood pressure.
Physical distortion of a mechanoreceptor’s plasma membrane causes ion channels to open, which leads to the generation of action potentials.
The action potential frequency is related to the strength of the stimulus. |
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Term
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Definition
Hearing
Equilibrium
Acceleration
Lateral line (fish)
Pressure (baroreceptors)
Touch
Proprioceptors (body position)
Vibration
Stretch receptors
SONAR |
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Term
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Definition
provide an animal with information about the position of its limbs and the stresses on its muscles and joints. They feed information continuously to the CNS.
Stretch receptors embedded in connective tissues in vertebrate skeletal muscle are called muscle spindles.
They are modified muscle fibers that are innervated in the center with extensions of sensory neurons.
The CNS uses information from muscle spindles to maintain a certain level of contraction or muscle tone. |
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Term
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Definition
The conversion of afferent to efferent information in the spinal cord without participation of the brain is called a spinal reflex.
The simplest spinal reflex involves only two neurons and one synapse; it is called a monosynaptic reflex, such as the knee-jerk reflex. |
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Definition
mechanoreceptors.
Each hair cell has a set of stereocilia (microvilli) and a longer kinocilium. When the stereocilia (and kinocilium) are bent in one direction, receptor potential becomes more negative; when they are bent in the other direction, it becomes more positive. This permits detection of direction.
When the membrane potential becomes more positive, the hair cell releases a neurotransmitter to the sensory neuron associated with it, and the sensory neuron sends action potentials to the CNS. |
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Term
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Definition
Hair cells found here for system of fishes. They provide information about:
- moving objects that cause pressure waves in water, an object moving toward the fish.
- stationary objects that reflect the fishes own water wave produced as the fish swims.
- body position, and perhaps swimming speed.
These evolved into the hair cells in the inner ear of higher vertebrates. |
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Term
| hair cells can be used for the following |
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Definition
Lateral line
Otoliths: gravity perception
Semi-circular canals: acceleration, gravity
Organ of Corti: auditory |
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Term
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Definition
use mechanoreceptors to convert pressure waves into action potentials.
Pinnae collect sound waves and direct them into the auditory canal, which leads to the middle inner ear.
The eardrum (tympanic membrane) covers the end of the auditory canal and vibrates in response to pressure waves. On the other side is the fluid-filled middle ear.
Pressure on both sides of the eardrum equilibrates because the Eustachian tube allows airflow. |
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Term
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Definition
rests on the basilar membrane.
The organ of Corti transduces pressure waves into action potentials in the auditory nerve.
The organ of Corti contains hair cells whose stereocilia are in contact with the tectorial membrane.
When the basilar membrane flexes, the tectorial membrane bends the hair cell stereocilia. |
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Definition
| loss of function of the tympanic membrane or ossicles of the middle ear. The ossicles stiffen with age causing loss of ability to hear high frequency sound. |
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Term
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Definition
deafness is caused by inner ear or auditory pathway damage, including damage to hair cells.
Loud rock music and other loud noises can cause damage to hair cells. They can actually be sheared off. This damage is cumulative and permanent. |
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Term
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Definition
Whales:used by whales for distance communication, orientation during migrations, etc.
Elephants: produce long wavelength “infrasound” calls. Can communicate up to 3 miles. (We cannot hear it.) |
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Term
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Definition
these molecules can absorb photons of light and undergo shape changes.
Rhodopsin consists of a protein called opsin and a light-absorbing group, 11-cis-retinal.
The retinal group is in the center of the opsin, and the entire complex is within the plasma membrane of a photoreceptor cell.
When 11-cis-retinal absorbs a photon, it changes to all-trans-retinal, which changes the conformation of the opsin. This change signals detection of light. |
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Term
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Definition
is a modified neuron. It releases neurotransmitters that influence other neurons.
Rod cells have an outer segment, an inner segment, and a synaptic terminal.
The inner segment has the nucleus and many mitochondria.
The outer segment has a stack of discs of plasma membrane densely packed with rhodopsin. The discs function to capture photons. |
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Term
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Definition
| are more sensitive to light |
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Term
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Definition
respond to different wavelengths of light for color vision.
Cones also provide the sharpest vision. The fovea has only cone cells. |
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