WEEK 6: 6.2 Special Senses Flashcards
What is the labelled lines principle?
The specific pathway that transmits information about a specific modality is a ‘labelled line’. Stimulation of a labelled line only produces a sensation of its modality, no matter what type of energy produces the action potentials
What are the steps involved in vision: eye
- Light waves pass through the cornea (a clear protective outer layer)
- light waves pass through the pupil (a small opening in the eye surrounded by the iris which regulates the amount of light entering the eye.
- light waves pass through the lens
- light waves as projected onto the retina, which contains all of the receptor cells
What receptors do light activate?
Photoreceptors, located within the retina of the eye
What are two different types of photo receptors
- Rods (monochromatic & low visual acuity)
- Cones (mediate colour vision, high visual acuity)
What happens once light information is processed within the retina photoreceptors?
this visual info is passed onto bipolar nerve cells -> ganglion cells (their axons form optic nerve)
What is the centre of the retina called
Macula, in which the fovea is the pit inside the macula that contains only cones
What is the ratio of rods to cones in the periphery of the retina?
Higher ratio of rods to cones
What is the blindspot called in the retina?
Optic disc
Image on the retina is ___ and ___
inverted and reversed
What is the optic nerve formed from?
axons and ganglion cells
optic nerve joins with an opposite optic nerve to form the
optic chiasm
What occurs in the optic chiasm
The partial crossing of optic nerve fibres, in which medial nasal retinal fibres cross whilst lateral temporal retinal fibres do not crosss
Axons from the optic tract terminate in the?
thalamus (in a region called lateral geniculate nucleus)
as the axons leave the thalamus, they form optic ___
radiations
After forming optic radiations, the axons then terminate in the
primary visual cortex
Where is the primary visual cortex located?
above the calcarine sulcus in the occipital lobe
What are the two different streams in which further processing of information happens in visual association areas?
- What stream: towards temporal cortex that recognises what an object is
-Where stream: Towards the parietal cortex that allows for recognition of where an object is
What 3 parts can the ear be divided into?
The external ear, middle ear and inner ear
What is the external ear’s function?
Sound collection , localising sound
What is the middle ear’s function?
impedance matching between outer ear (air) and inner ear (liquid)
What is the inner ear’s function?
signals are analysed and transduced
What are the sensory receptors in the inner ear essential for hearing?
hair cells
What is the function of hair cells?
to convert sound vibrations into electrical signals
Describe the steps in which hair cells work?
- sound enters the ear, travels through the ear canal, hits the eardrum and causes it to vibrate
- vibrations are transmitted through ossicles, middle ear bones, to the cochlea in the inner ear
- inside the cochlea, sound vibrations create waves in fluid-filled chambers
- these waves move to the basilar membrane, causing hair cells sitting on it to bend
- when hair cells bend, they generate electrical signals sent to the brain via the auditory nerve
- the brain interprets these signals as sound
What are the two types of hair cells
Inner hair cell (detects sound and sends it to the brain)
Outer hair cell (amplifies sound vibrations to make inner hair cells more sensitive
What pathway does the information transmitted by hair cell receptors follow?
- bipolar cells in spiral ganglion take information from hair cell receptors to the vestibulocochlear nerve
- this info travels to the cochlear nuclei- medulla oblongata
- this info then travels to the inferior colliculi (metencephalon)
- this info then travels to the medial geniculate nuclei (mesencephalon)
- finally sound info is transmitted to the primary auditory cortex (telencephalon)
what does monoaural information refer to?
info from one ear = moved to the other side of the brain
what does binaural info refer to?
info about the differences between sounds at two ears
The vestibular labyrinth is related to?
Balance
What are the main structures in the vestibular system>
three semicircular canals and two otolith organs (the utricle and saccule)
the vestibular nuclei in the brainstem have connections to ?
motor centers for control of eye movement, head movement, posture, limb movement and upright position as well as the thalamus and cortex for the conscious perception of where we are in space
What do the anterior, posterior and lateral semicircular canals detect?
rotation of the head
What do the otolith organs detect?
Linear movements and the position of your head relative to gravity
In what steps does information regarding balance move through?
Hair cells -> vestibular ganglion cells -> vestibular nuceli -> cerebellum (info related to control of movement)
What is vertigo?
the feeling one is moving with respect to the environment , or the environment is moving when it is stationary
What is the broca area
- Language production, speaking words, and comprehension
- Posterior inferior frontal gyrus
What is Wernicke area
- Comprehension of written and spoken language
- Posterior superior temporal gyrus
What is the secondary auditory cortex
Where hearing is processed
What does the arcuate fasiculus do?
Connect Wernicke’s and Broca’s areas
What is broca’s aphasia
Know what to say but you can’t
What is Wernicke’s aphasia
Fluent speech but words lack meaning - inability to comprehend spoken words
Briefly list the steps in which information is transmitter when hearing and comprehending words
- Hearing occurs when sound enters the inner ear
- transferred this info to Area 41 (gyri transversales, temporal lobe)
- transfer such info to Wernicke’s area for sensory matching
- Hear and comprehend words
Briefly list the steps in which information is transmitted when speaking
- Wernicke’s area is accessed for word storage
- Wernicke’s area transmits info to Broca’s area for motor program of speech
- Broca’s area sends speech info to the motor cortex for the purpose of motor execution
- The motor cortex sends speech info to the cranial nerves
Speech occurs
Once speech/language information is processed in the wernicke brocas and premotor/motor cortices, this information comes out in the
Corticobulbar tract, motor nuclei of cranial nerves and cranial nerves
For speech, the cranial nerves innervate the
muscles of face, tongue, pharynx and suprahyoid muscles
the brain and cranial nerves work together to control:
phonation (sound production)
articulation (forming speech sounds)
What cranial nerves are involved in speech?
- CN X (vagus nerve)
- Respiration
- CN IX (glossopharyngeal) and X (vagus)
- CN XII (hypoglossal)
- Facial CN VII
What is the pathway from the motor cortex to the cranial nerves?
- starts in the motor cortex
- travels via the corticobulbar tract
- ends at the motor nuclei of cranial nerves X, XI, XII and VII
Speech isn’t just about motor signals, it involves
Feedback from sensory nerves to fine-tune and adjust speech
The vagus nerve provides sensory feedback from the ____ & ___ to control speech accruately
larynx and vocal cords
What two branches does the superior laryngeal nerve have?
an internal branch - sensory input
an external branch- motor control to cricothyroid muscle
What are odourants captured on?
the olfactory epithelium
what are two types of epithelium present in the nasal cavity?
respiratory and olfactory epithelium
what are olfactory receptor cells?
they are in the olfactory epithelium, and are the site of transduction, they transform chemicals into the sense of smell
How do olfactory receptor cells work?
odourants in the air dissolve in mucus, which holds odourants in place so they come in contact with olfactory receptors, this stimulation generates receptor potential
What type of neuron are olfactory receptor neurons?
bipolar neurons
The thin unmyelinated axons of the olfactory receptor cells form the?
Olfactory nerve
Where do the olfactory nerves first synapse?
The olfactory bulb
What are glomeruli
synaptic hubs where the olfactory axons meet and synapse with the dendrites of neurons rising in the olfactory bulb
So in what order does olfactory info travel?
olfactory bulb -> olfactory tract -> mostly terminates in the primary olfacotry cortex -> other locations for further processing (amygdala, hippocampus, orbitofrontal cortex)
What are the 5 basic tastes?
sweet, sour, umami, bitter, salty
What are papillae
numerous bumbs on the upper surface of the tongue, which contain numerous taste buds that contain taste receptor cells
T or F: Taste receptor cells are neurons
F: they aren’t neurons, they form synapses with endings of gustatory afferents near the bottom of the taste bud
Briefly describe the steps in which gustatory transduction occurs
- tastant enters the mouth & molecules combine with saliva & bind to taste receptors
- depolarisation causes calcium channels to open, and an influx of ca2+ ions trigger release of neurotransmitter molecules
- neurotransmitter excites post synaptic sensory axon to fire action potential
T or F: Most of the tongue is sensitive to all basic tastes
T
How is this gustatory info transmitted to the brain?
- 3 cranial nerves innervate different regions of the tongue and throat
- info is passed onto the medulla (gustatory nucleus, thalamus and finally the cerebral cortex (gustatory cortex)
Where is the primary taste cortex located?
in the parietal lobe and insula
Flavour is a function of?
Taste and smell - retronasal and orthonasal olfaction
