- Define peripheral nervous system.
Portion of the nervous system consisting of nerves and ganglia that lie outside of the brain and spinal cord.
- Peripheral nervous system - list its components.
Sensory receptors, peripheral nerves and associated ganglia, efferent motor endings.
Stimulus
A change in the environment that evokes a response; excitant/irritant.
Sensation
Conscious or subconscious awareness of a stimulus
(much of sensory input is only relayed to lower areas (thalamus/brain stem) where a response is intiated without your awareness)
Perception
Conscious awareness and interpretation of the meaning of the stimulus. (cerebral cortex)
Why is a receptor a “biological transducer”?
It converts the stimulus into electrical graded potentials.
What two features are critical to the function of sensory receptors?
- Receptors establish and maintain a RMP
- Receptors contain modality-gated channel within their plasma membrane. Modality gated channels open in response to a stimulus other than a chemical or voltage change.
- Describe sensory receptors, their role.
?
What are the classifications of receptors by structural complexity?
Somatosensory receptors vs. sense organs
Somatosensory
- –Nonencapsulated, free/naked nerve endings, simple structure.
- –Encapsulated dendritic endings (wrapped in CT - mechanoreceptors for touch/pressure, more complex)
Sense organs = highly specialized receptor cells (nerve ending combined with epithelial/CT/muscular tissue that enhance or moderate the response to a stimulus.
What are the classifications of receptors by stimulus detected?
Chemoreceptors, nociceptors, mechanoreceptors, photoreceptors, thermoreceptors
What are the classifications of receptors by location or stimulous origin?
Exteroceptors,
interoceptors,
proprioceptors
(external stimuli, visceral sensation, position/movement)
Chemoreceptor
O2, pH, various organic molecules like glucose
Nociceptor
Pain (tissue damage interpreted as pain) somatic and visceral
Fyi. Activated by thermoreceptors, then heat/cold are perceived as pain.
Mechanoreceptor
Pressure, vibration, gravity, acceleration, sound, stretch and most cutaneous. Includes baroreceptors/bp/stretch and distention.
Photoreceptor
light photons
Thermoreceptor
Heat - present in skin and hypothalamus
Receptor distribution?
General senses = throughout body (somatic and visceral) Special senses = localized in the head.
What is different about receptors for smell vs. other special sense receptors?
Receptors for smell are neurons. Other senses use non-neural receptor cells that synapse onto sensory neurons.
