Flashcards in Chapter 46 Deck (49):
What is the general function of mechanoreceptors?
Detect mechanical compression or stretching of the receptor of if the tissues adjacent to the receptor
What is the general function of thermoreceptors?
Detect changes in temperature, with some detecting cold and others warmth
What is the general function of nociceptors?
Detect damage occurring in the tissues, whether physiological damage or chemical damage
What is the general function of electromagnetic receptors?
Detect light on the retina of the eye
What is the general function of chemoreceptors?
Sense taste, smell, oxygen level in the blood, osmolality of the fluids, and CO2
What is the labeled line principle?
the specificity of nerve fibers for transmitting only 1 modality of sensation
What is the receptor potential?
the immediate change in the membrane electrical potential of a receptor due to a stimulus.
How do mechanical deformations generate receptor potentials?
stretching the receptor membrane and opens the ion channels.
How do chemcials generate receptor potentials?
Application of a chemical to the membrane opens the ion channels.
How does temperature generate receptor potentials?
alters the permeability of the membrane
How does electromagnetic radiation generate receptor potentials?
electromagnetic radiation, such as light on a retinal visual receptor, which directly or indirectly changes the receptor membrane characteristics and allows the ions to flow through the membrane channels
What happens when the receptor potential rises above the threshold for the nerve membrane?
an action potential occurs
What exactly is the threshold, again?
a specific voltage of a membrane that, when reached, causes the spontaneous opening of ion channels. Depolarizing to membrane in a nerve leads to opening of Voltage-gated Na+ channels
What is the relationship between frequency of action potentials to receptor potential?
• The frequency of repetitive action potentials from sensory receptors increases approximately in proportion to the increase in receptor potential.
What does the depolarization and frequency of action potential relationship have to do with receptor range?
it allows the receptors to have an extreme range of the response, from very weak to very intense
What is receptor adaptation?
when a continuous sensory stimulus is applied, the receptor responds at a high impulse rate at first and then at a progressively slower rate until none at all.
What are tonic receptors?
- slowly adapting receptors that can transmit information for many hours
What do tonic receptors do for stimulus recognition?
o These slowly adapting receptors continue to transmit impulses to the brain as long as the stimulus is present. This keeps the brain constantly knowledgeable of the status of the body and its relation to the surroundings
What are some examples of tonic receptors?
Golgi tendon organs, pain receptors, barorecetpors, chemorecptors
What are phasic receptors?
rapidly adapting receptors that are stimulated only when the stimulus strength changes
What do phasic receptors do for stimulus recognition?
o Important for receptors like pacinian corpuscles because they can rapidly detect tissue deformations
What are the subtypes of A fibers?
α, β, γ, δ
What is the size and myelination of A fibers?
large and myelinated
What is the size and myelination of C fibers?
small, No myelination
More than 1/2 of sensory fibers in peripheral nerves and postganglionic ANS fibers are what type (A or C)?
What are the characteristics of Ia fibers?
Fibers from the annulospiral endings of muscle spindles.
What is the size (microns) of Ia fibers?
What is the type (in general classification) of Ia fibers?
What are the characteristics of Ib fibers?
Fibers from the Golgi tendon organs
What is the size (microns) of Ia fibers?
What is the type (in general classification) of Ib fibers?
What are the characteristics of II fibers?
Fibers from the most discrete cutaneous tactile receptors and from the flower-spray endings of the muscle spindles.
What is the size (microns) of II fibers?
What is the type (in general classification) of II fibers?
What are the characteristics of III fibers?
Carries temperature, crude touch, and pricking pain sensations
What is the size (microns) of III fibers?
What is the type (in general classification) of III fibers?
What are the characteristics of IV fibers?
Unmyelinated carrying pain, itch, temperature, and crude touch sensations
What is the size (microns) of IV fibers?
What is the type (in general classification) of IV fibers?
What is a multi-neuron pool?
functional groups of neurons that has its own special organization to achieve a multitude of functions of the nervous system
What is divergence?
when weak signals entering a neuronal pool can excite far greater numbers of nerve fibers leaving the pool
What is amplifying divergence?
it’s when an input signal spreads to an increasing number of neurons as it passes through successive orders of neurons in its path. This is seen in the corticospinal pathway, where 1 large pyramidal cell can excite as many as 10,000 muscle fibers.
What is divergence in multiple tracts?
a signal is transmitted in 2 directions from the pool. For instance, information is transmitted up the dorsal columns goes to both the cerebellum and the thalamus
What is convergence?
signals from multiple inputs unite to excite a single neuron
What can happen when there is convergence from multiple sources?
Summation. This is a “summed” effect of the different signals from each neuron and allows multiple types of information
What is the role of an inhibitory interneuron in a normally excitatory pathway?
a signal going to a neuronal pool can cause an output excitatory signal going in 1 direction and an inhibitory signal going in a direction (reciprocal inhibition)
What are the 2 mechanisms of inhibitory circuits to prevent seizures?
A negative feedback mechanism, where the termini have signals that inhibit the initial stimulus
Gross inhibitory control over the widespread areas of the brain, like how the basal ganglia inhibit a lot of muscle movements to allow precise control of movements.