Week 4 - Neural Pathways Flashcards
sensation
the initial detection of physical stimuli by sensory receptors
perception
the interpretation and conscious awareness of stimuli by the brain
somatic sense
sensations detected by sensory receptors in the skin, muscles, joints, and internal organs. these senses include touch, pain, temperature, pressure, and proprioception.
visceral sense
sensations that originate from internal organs (viscera), such as the heart, lungs, and GI tract. these senses detect changes in internal conditions, including pain, pressure, stretch, temperature, and chemical changes.
first-order neuron
detects sensory stimuli (e.g., touch, pain, temperature) and transmits signals from receptors to the spinal cord or brainstem.
free nerve endings
the dendrites of the first-order neuron act as the sensory receptor. these are typically associated with pain, temperature, and crude touch.
encapsulated nerve endings
the first-order neuron’s dendrites are enclosed in a connective tissue capsule, which enhances sensitivity to stimuli. associated with light touch, pressure, and proprioception.
separate sensory cells
the sensory receptor is a specialized cell that synapses with the first-order neuron. the receptor cell detects the stimulus and releases neurotransmitters to activate the neuron. this occurs in special senses, such as vision (photoreceptors), hearing (hair cells), and taste (gustatory cells), etc.
interoceptor
a sensory receptor that detects stimuli from within the body, such as changes in BP, oxygen levels, pH, and internal organ stretch. these receptors help regulate homeostasis and are found in the viscera, blood vessels, and nervous system.
exteroceptor
a sensory receptor that detects external stimuli from the environment, such as touch, temperature, pain, and special senses (vision, hearing, smell, taste). these receptors are located in the skin, mucous membranes, and sense organs.
proprioceptor
a sensory receptor that detects body position, movement, and muscle tension. these receptors are found in the muscles, tendons, joints, and inner ear (vestibular system) and help maintain posture and coordination.
mechanoreceptor
detect mechanical forces such as pressure, vibration, touch, and stretch.
*they play a key role in proprioception.
thermoreceptor
detect changes in temperature. there are two main types: cold receptors and warmth receptors.
nociceptor
detect pain or noxious stimuli that could cause tissue damage. they respond to mechanical, thermal, or chemical stimuli.
*e.g., capsaicin
photoreceptor
detect light and allow for vision by converting light into neural signals. they are located in the retina and include rods for low-light vision and cones for colour vision.
osmoreceptor
detect changes in osmotic pressure by sensing the concentration of solutes (i.e., osmolarity) in body fluids (e.g., blood). they are primarily found in the hypothalamus and they help regulate water balance and are important for maintaining homeostasis.
chemoreceptor
detect PCO2 and PO2 as well as pH levels. peripheral chemoreceptors are found in the carotid and aortic bodies, while central chemoreceptors are located in the medulla oblongata.
adaptation
the decrease in sensitivity to a constant stimulus over time. this occurs when sensory receptors reduce their response to a prolonged stimulus.
slowly adapting receptors
continue to generate action potentials for the duration of a stimulus, providing sustained information about a stimulus presence (e.g., pain receptors, proprioceptors)
rapidly adapting receptors
respond quickly to changes in stimuli but stop firing if the stimulus remains constant, detecting only the onset and offset (e.g., touch, pressure, smell, and some temperature receptors)
second-order neuron
located in the spinal cord or brainstem, it receives input from the first-order neuron and decussates before ascending to the thalamus.
third-order neuron
located in the thalamus, it relays sensory info to the primary somatosensory area (in the postcentral gyrus) for perception.
upper motor neuron
originates in the primary motor area (precentral gyrus of the frontal lobe) and sends signals down the spinal cord (for body movements) or the brainstem (for facial movements) to regulate movement.
lower motor neuron
directly innervates skeletal muscle, receiving input directly from UMNs (only in direct motor pathways), or local circuit neurons (in indirect motor pathways) to generate movement.
