L6, The Senses Flashcards
What does the sensory system do? What does it consist of?
The main components of the system include sensory organs, sensory receptors, neural pathways and brain areas. It is responsible for processing sensory information (balance/touch etc)
How does the sensory process (generally) work?
In the presence of an adequate physical stimulus, sensory organs collect the information, then conversion or transduction of the information into the information encoded by neural signals (action potentials), resulting in the appearance of a specific body response.
What is transduction?
The process where receptors convert sensory information into neural signals
What is a receptor potential?
the step between the arrival of energy at the receptor cell and the initiation of an action potential
How does light get processed in the retina?
Light passes through the pupils and hits the photoreceptors in the retina, either rods or cones. The information then passes through the four different nerve cells in the photoreceptor layer, the intermediate layer, and the ganglion cells layer. The ganglion layer transmits the info to the primary visual cortex (occipital lobe) via brain networks, or the secondary visual cortex for higher level processing.
What are the four nerve cells of the retina?
- Horizontal cells
- Amacrine cells
- Bipolar cells
- Ganglion cells
How is darkness/light processed in the retina?
In darkness, the retina’s Na channels are always open by cGMP, causing
an influx of sodium which causes depolarisation. The dark currents lead to a continuous release of the neurotransmitter glutamate (inhibitory).
Light is absorbed by a pigment in the rods called rhodopsin. The activation of rhodopsin by light energy causes the G-protein to exchange GTP for GDP, which in turn activates the enzyme phosphodiesterase (PDE). PDE breaks down cGMP and causes Na+ ions to close (shut off dark current).
What is somatosensation? How does it work?
Somatosensation is the system responsible for perceiving/interpreting touch/pain. Areas of the body with high tactile discrimination include fingertips etc.
Different tactile receptors, such as Merkel cells (light touch/shape), Meissner’s corpuscles (light touch/low-frequency vibrations), Pacinian corpuscles (deep pressure/high-frequency vibrations), Ruffini endings (skin stretch/pressure), respond to touch stimulus, whereas nociceptors detect pain. The information is finally processed in the somatosensory cortex.
How is sound processed?
Sound produces waves characterized by frequency (pitch/speed) and amplitude (loudness/size). The soundwaves cause vibrations that bend the stereocilia (hair cell’s hearing receptors), causing Ca channels to open, releasing neurotransmitters causing an action potential to be generated before being transmitted (via the auditory nerve) to the auditory cortex in the superior temporal lobe.
What is the vestibular system?
It senses head rotation through pitch, rotation around the x-axis, yaw, rotation around the y-axis, or roll, rotation around the z-axis. In the vestibular system are the semi-circular canals in the vestibular labyrinth, filled with jelly-like liquid sensing movements through the vestibular hair cells, generating an action potential.
