Topic 6: Senses Flashcards
What is the blind spot and why is it blind?
The blind spot is the optic disc. This is the part of the retina where the optic nerve exits, so there are no photoreceptors. The brain fills in the blanks
Define Glaucoma?
A problem with the drainage of the aqueous humour increases the amount of this fluid and therefore the pressure of the whole eye (normally 16mmHg). This compresses the retina and optic nerve which can eventually lead to blindness.
Define Cataracts?
A clouding of the lens, mostly due to age related thickening and hardening. It leads to blurred vision.
Risk factors for Cataracts?
Smoking and Diabetes
Where do you find taste buds?
All parts of the tongue and some on the palate, cheeks, epiglottis and pharynx.
Characteristics of olfactory receptor cells?
They are chemoreceptors, are bipolar neurons, have cilia and a short life span (30-60 days) and get replaced.
What are the 5 taste modalities?
Sweet, sour, salty, bitter, umami
What are examples of chemicals that trigger sweet taste modalities?
sugar, alcohol, amino acids
What are examples of chemicals that trigger sour taste modalities?
acids and H+ ions
What are examples of chemicals that trigger salty taste modalities?
metal ions and salt
What are examples of chemicals that trigger bitter taste modalities?
alkaloids (caffeine)
What are examples of chemicals that trigger umami taste modalities?
glutamate
Why can smell trigger and emotional response?
Dangerous smells can trigger a flight and fight response, appetising smells activate the digestive system vis the ANS. However, many smells just elicit emotional responses and/or memories.
List the sequence of the olfactory pathway from receptor to the brain?
Olfactory receptor - olfactory bulb - olfactory tracts - cranial nerve I (olfactory) - primary olfactory cortex (temporal lobe) - two pathways.
1. to the frontal lobe for further interpretation
2. to the limbic system, which is the emotional centre of the brain
define transduction?
The stimulus energy gets converted into graded potential. In the case of the receptor being a separate cell, this is called a receptor potential. The receptor potential leads to the release of neurotransmitters from the receptor cell.
Transduction through hearing?
Sound waves make the basilar membrane vibrate, which stimulates the cochlear hair cells and their stereocilia as they move and pivot with that vibration. This opens ion channels causing a graded receptor potential in the cochlear hair cells.
How do we hear sound?
Sounds waves travel through the external meatus, hit the tympanic membrane and make it vibrate- auditory ossicles pick up, amplify and transfer the vibration to the oval window - triggers movement of perilymph and endolymph in the cochlea - the spiral organs in the cochlea contain cochlear hair cells - cochlear nerve -cranial nerve VIII (vestibulocochlear) - midbrain - thalamus - primary auditory cortex (temporal lobe)
How are sound waves characterised?
Frequency = pitch, measured in Hertz (Hz)
Amplitude = loudness, measured in decibels (dB)
What are the three major areas of the ear?
External, middle and inner ear
What is the function of the inner ear?
The cochlea has the receptors for hearing. The vestibular apparatus of the inner ear is responsible for balance and informs the brain of where the body is located in space.
What is the function of the external and middle ear?
Responsible for the transmission of soundwaves. Filled with air
What are the three main sources of sensory input that the brain uses in order to control balance and equilibrium?
Vestibular receptors of the labyrinth, visual receptors and proprioceptors of muscles, tendons and ligaments
Define nystagmus?
Sudden jerking eye movements that occur during and immediately after rotation of the head and body.
The fibrous layer of the eye contains the _____?
cornea
