Missouri State Bio 361 Test 2
Terms in this set (63)
can usually be divided into two groups based on morphology: Free nerve endings characterize the nociceptors and thermoreceptors and are called thus because the terminal branches of the neuron are unmyelinated and spread throughout the dermis and epidermis.
simple somatic receptors
are neurons with free nerve endings
complex somatic receptors
have nerve endings enclosed in connective tissue capsules
are ells that release a neurotransmitter onto sensory neurons, initiation an action potential.
Law of specific energies
Specifity of a receptor for a particular type of stimulus
Form of energy to which a receptor is most sensitive.
input, both external and internal, from the sensory nervous system to the CNS
the conscious interpretation of input from our external and internal environments; *involves sensory input (sensation), previous experiences (memory), and rules of interpretations
The conversion from stimulus energy to electrical energy (changes in receptor potential, i.e., production of graded potentials)
the ability of the nervous system to identify the type, location and strength of a stimulus
What kind of stimulus is it? Determined by the receptor(s) and pathway(s) activated.
coding depends on the projection and receptive fields.
pathway from a receptor to a specific set of interneurons
area over which a stimulus can be detected by a given sensory neuron
precision with which stimulus can be detected by a given sensory neuron
coding depends on number of receptors activated and frequency of action potentials generated.
Decline in perceived strength of a stimulus over time.
reacts to discrete events. A) when a stimulation starts, initial increase of receptor potentials (RP's). B) If stimulus continues, RP's decrease. C) Adaptation can occur in 0.1-5 seconds
Tonic (degrees of change)
monitors continuous variables. A) always firing RP's. B) Firing 'rate' changes with magnitude of stimulus. C) Stimulation can result in IPSP or EPSP
- inhibition of neighboring receptor activity in the presence of a strong stimulus; increases acuity
Muscle spindle receptors
length and stretch receptors. Stimulates the activated muscle and interneurons that inhibit antagonistic muscles. Homeostatic control of muscle length; quick response to changes in muscle length.
Golgi tendon receptors
muscle tension receptors, detect stretch, but reflexes are polysynaptic. Discharge Aps in response to tension in tendons. Stimulates neurons that inhibit the contracting/stretching muscle and stimulate the antagonistic muscle.
refers to the body's ability to sense movement within joints and joint position. This ability enables us to know where our limbs are in space without having to look. It is important in all everyday movements but especially so in complicated sporting movements, where precise coordination is essential.
a sense organ or cell that responds to a mechanical stimuli such as touch or sound
locations: cutaneous, core, hypothalamus. Types: heat, cold, heat pain, cold pain. Different types are activated at different temperature ranges.
is the bending of a wave when it enters a medium where its speed is different. The refraction of light when it passes from a fast medium to a slow medium bends the light ray toward the normal to the boundary between the two media.
Mechanisms of Visual Accommodation
ability to focus objects different distances from the eye
Distribution of rods and cones
Functions of rods
changes in light levels
Function of cones
differentiate colors; three types in humans
Light receptors within the eye transmit messages to the brain, which produces the familiar sensations of color. Newton observed that color is not inherent in objects. Rather, the surface of an object reflects some colors and absorbs all the others. We perceive only the reflected colors.
Location and role of melanopsin
In humans, melanopsin is found in intrinsically photosensitive retinal ganglion cells (ipRGCs). Melanopsin plays an important non-image-forming role in the setting of circadian rhythms as well as other functions.
PHOTOTRANSDUCTION IN ROD CELLS
conversion of light energy into electrical signals
Neural pathway from the optic nerve to the optic cortex
The information leaves the eye by way of the optic nerve, and there is a partial crossing of axons at the optic chiasm. After the chiasm, the axons are called the optic tract. The optictract wraps around the midbrain to get to the lateral geniculate nucleus (LGN), where all the axons must synapse.
The optic nerve connects the eye to the brain. The optic nerve carries the impulses formed by the retina, the nerve layer that lines the back of the eye and senses light and creates impulses. These impulses are dispatched through the optic nerve to the brain, which interprets them as images.
X-shaped structure formed by the crossing of the optic nerves in the brain. The optic nerve connects the brain to the eye. To biologists, the optic chiasmis thought to be a turning point in evolution.
lateral geniculate nucleus
is a relay center in the thalamus for the visual pathway. It receives a major sensory input from the retina.
s the visual processing center of the mammalian brain containing most of the anatomical region of the visual cortex
2D (is the portion of the visual field that is associated with only one eye)
3D (where left and right visual fields overlap)
Conditions necessary for transduction of a chemical signal
2. Bind to a membrane-bound receptor protein.
3. Activate the receptor protein.
4. Exhibit receptor specificity.
Location of gustatory receptors
tongue, palate, pharynx! Differentiates taste of different substances. Each taste bud contains 100 receptor cells.
Taste buds occur in clusters called fungiform papillae (mostly).
Texture of food is detected by mechanoreceptors on filiform papillae.
when a stimulus of one type causes an involuntary perception of another type.
(smell) receptor cells found in the olfactory epithelium, within the nasal cavity. Receptors are afferent neurons. Approx. 10,000,000 olfactory cells. Chemicals detected depend on the receptor type, of which there are about 1,000. These receptor ccells are the only neurons known to regularly undergo neurogenesis (completely turnover about every 2 months)
Vomeronasal organ (VNO)
*accessory olfactory structure in many mammals. Regressed/absent in humans, but we may still detect pheromones.
Comparisons between the nervous and endocrine systems
endocrine system is "the other" communication system. There is a lot of interactions between the neural and endocrine system, therefore, maybe better thought of as one half of the "Neuroendocrine System"
influences secretion of other hormones
a substance from which another is formed, especially by metabolic reaction.
define the biological rhythms in humans and other animals. Can provide anticipatory responses to ongoing environmental changes.
involved in the movement of ions, small molecules, or macromolecules, such as another protein, across a biological membrane.
synergism (non-additive interactions)
Synergistic interaction means that the effect of two chemicals taken together is greater than the sum of their separate effect at the same doses. Additive interaction means the effect of two chemicals is equal to the sum of the effect of the two chemicals taken separately.
long - loop feedback
refers to the hormone that was released from the peripheral endocrine glands inhibiting pituitary and/or hypothalamic secretion of releasing hormones.
loop feedback - generally refers to a pituitary hormone providing negative feedback to the hypothalamus, inhibiting secretion of the releasing hormone. For example, growth hormone releasing hormone (GHRH) from the hypothalamus is inhibited by growth hormone (GH) that has been released from the pituitary.
is a biological occurrence wherein the output of a system amplifies the system (positive feedback) or inhibits the system (negative feedback)
Classes of gustatory receptors
Sucrose, lactose, maltose
Activate 'sweet receptors'
Activate 'sour receptors'
Activate salt receptors
Caffeine, nicotine, quinine
Activate 'bitter receptors'
Amino acid found in many proteins, MSG
Activate 'Umami' receptors
Similarities between hormones and neurotransmitters
2.Used in negative feedback
3.Bind to protein receptors at target
4.Binding follows rules of mass action
5.H-R complex → change in cell function
6.Can change the rate of target function
7.Graded response, stimulation and inhibition possible
8.Deactivated by enzymes
9.Tonic release of many hormones
10.Involved in down- and up-regulation of cell processes
Differences between hormones and neurotransmitters. (aside from chart on study guide)
1.Many hormones are secreted as precursors
2.Many are secreted in cycles
3.Some circulate bound to plasma proteins
4.Hormone interactions are usually non-additive
Hormone secretion stimuli. Classic negative feed-back (usually). Hormone expression is regulated by:
1.Ion or nutrient concentration in plasma
Events in phototransduction, starting with light striking rhodopsin
1.In the dark, rhodopsin is intact and Na+ and K+ channels are open. resting membrane potential = -40 mV cGMP levels are high
In this state, there is tonic release of neurotransmitter.
2a. When light strikes rhodopsin, retinal changes conformation and binds to the pigmented epithelium. Rhodopsin→Opsin (molecule is bleached), which activates a 2nd messenger (transducin)
cGMP is decreased, causing Na+ channels to close.
Opsin & Rhodopsin conform to Law of Mass Action
(Adaption occurs over time)
2b. During recovery (light stimulus removed), retinal is converted back to its inactive
form and it binds to opsin.
Na+ channels reopen, neurotransmitter secretion increases.
3. Hyperpolarizing membrane potential causes closing of Ca++ channels in inner segment
4. Less Ca2+ enters cell, neurotransmitter release declines (glutamate)
As light levels increase:
ON pathways: rods ↓ glutamate secretion → bipolar cells ↓ breakdown of cGMP (so more cGMP present), Na+ channels open, cell depolarizes, so more NT to ganglion cells and more APs
OFF pathways: rods ↓ glutamate → closes bipolar cell cation channels, cell hyperpolarizes, so less NT to ganglion cells and fewer APs
Ganglion cells exit via the optic nerve and transmit action
potentials to the brain.
Each ganglion cell receives information from
many photoreceptors. Each ganglion's
receptors are grouped into a 'receptor field.'
Receptive fields are composed of either all
'ON' or all 'OFF' bipolar cells.
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