Week 5 - Sensing the World

Question 1

Explain what is Sound?

Answer 1

Vibrations in air molecules due to pressure, travelling in waves to our ears (pinnae)

Question 2

Identify the properties of sound and their wave properties?

Answer 2

Pitch (frequency high/low) - closeness
Amplitude (loudness) - height
Timbre (complexity)

Question 3

Identify the parts that make up the ear?

Answer 3

Outer ear - Pinna and Auditory canal
Middle ear - Eardrum (tympanic membrane) and Ossicles
Inner ear - Semicircular canals, Vestibular sacs (Utricles and Saccule), Cochlear

Question 4

Define the role of the pinna?

Answer 4

Part of outer ear to focus sounds waves into the auditory canal towards the eardrum

Question 5

Identify the Ossicles and outline their function?

Answer 5

Three bones, the Malleus, Incus, and Stapes, that trasmit sound across the middle ear from the eardrum (tympanic membrane) to the oval window of the cochlear

Question 6

Identify the Cochlea’s Function in processing sound?

Answer 6

Transduces acoustic energy of vibration into neural activity.

Question 7

Explain how the Cochlea’s Function?

Answer 7

(1) The Cochlea is a snail like bone structure with three channels, two with fluid (vestibular and tympanic canals). (2) The last ossicle, stirrup, vibrates oval window causing pressure waves in fluid of vestibular canal. This flexes the basilar membrane that excites hair cells, deforming them and triggering action potentials. (3) This firing transmits via the auditory nerve to the auditory cortex via the thalamus. Pressure is released through the tympanic canal via the round window.

Question 8

Describe how the auditory system allows us to hear?

Answer 8

The pinna focus’ vibrating air molecules into the auditory canal towards the eardrum. This excites the Ossicles, passing along sensitive noise towards the Cochlea to be process into neural activity by the basilar membranes mechanical properties.

Question 9

In basic, explain how the Cochlea Functions?

Answer 9

The cochlea’s stirrup receives and send vibration, where this excited hair cells in the basilar membrane to send neural signals.

Question 10

Explain the role of the basilar membrane in processing sounds? (Reference how high/low frequencies are processed)

Answer 10

Different frequencies bend the basilar membrane is different ways, which causes the hair cells to activate. High frequencies bend closer to the base (thick end) than low frequencies (bend towards the thin end) on the membrane, causing different action potentials, due to different thicknesses at each end.

Question 11

Outline the Auditory Neural Sensory Pathway?

Answer 11

From the Auditory nerve in the Cochlea, the neural activity passes through the medulla, up the inferior colliculus (coding spatial information), towards the medial geniculate nucleus (thalamus), then to the auditory cortex.

Question 12

Identify the three ways localisation of sound occurs?

Answer 12

In the brain, bi-neural neurons process Interaural time and intensity difference (left/right), and modification by the pinna (which allow for above/below, front/back hearing).

Question 13

Outline the physiology of localisation?

Answer 13

Neurons will fire when they receive simultaneous information from both auditory nerves (meet in the middle).

Question 14

Identify the two main forms of hearing loss? What is the less common form of deafness? and, How can you quickly determine what is causing deafness?

Answer 14

(1) Conductive deafness (outer/middle ear) - physical obstruction of transmission to the basilar membrane, e.g. burst ear drums, ossification (hardening), and infection of middle ear.
(2) Sensorineural deafness (inner ear) - damage to neural apparatus, e.g. auditory cortex becomes damaged when stroke, noise exposure that damages hair cells, infection.
(3) Less commonly, Central deafness (brain) exists, due to lesions/auditory damage in the brain
(4) The Jaw/Skull detects noises also, so if tapping head can be heard, its not neural damage.

Question 15

Outline the purpose of the Proprioception system and identify its components?

Answer 15

Balance, body senses, and head movements. Made up of the vestibular and kinaesthetic systems.

Question 16

Identify the parts that make up the vestibular system, and what are their functions?

Answer 16

Located in the inner ear, Three Semicircular canals (Angular rotations for 3D movement, balance, reflexive eye movements for stable vision) and Vestibular sacs (Utricles and Saccule to maintain upright and alert the body of position relative to gravity).

Question 17

Describe the function vestibular system, and simply, what does it do?

Answer 17

Detects accelerations using fluid and bending hair cells, detecting deformation, that cause an action potential to fire. Used for linear accelerations and gravity, for staying upright.

Question 18

Describe how does the Kinaesthetic system functions? and, what is it for? are we aware of it?

Answer 18

Receptors in muscles and limbs alert the brain about limbs/digits angles relative to the body. This allows for smooth coordinated movements, and makes fine adjustments to stay upright. We are unaware of it function, as it is seamlessly integrated with the vestibular system.

Question 19

Explain what Sensory Coding is? How is Intensity senses?

Answer 19

The process that allows the body to convert physical energy into action potentials for neural activity. The rate of action potentials “codes” for how intense a stimulus is. (because of the “all or none” aspect of action potentials)

Question 20

Basically, Explain How does the proprioception system works (a) and (b)?

Answer 20

(a) The Inner ears detects accelerations and rotation to maintain balance and upright positions, (b) whilst receptors in joins/muscles alerts the body of limb positions to perform smooth coordinated movements.

Question 21

Explain how the skin sensory system function?

Answer 21

Different Receptors at different layers of skin are activated by heat of pressure. When activated, these heat and pressure receptors fire action potentials which is transmitted to the somatosensory cortex.

Question 22

Explain the location and function of somatosensory cortex and its distribution?

Answer 22

Located posterior to the central sulcus, it receives all touch information, where different sections of the cortex are proportionally distributed based on their importance (hands and lips use a large portion).

Question 23

Compare smell and taste senses?

Answer 23

Both are chemical senses, where smell tranduces via chemicals dissolved in mucus, and taste tranduces via chemical dissolved in saliva. They were probably the first sensory system to evolve.

Question 24

Explain the role of taste?

Answer 24

Different chemicals activate particular receptors. Chemicals dissolved in saliva activate clumps of receptors (taste buds) located on the side of large papilla on the tongue.

Question 25

Identify the different tastes and Explain how they relate to the tongues distribution of taste buds?

Answer 25

Salt, Sweet, Bitter, Sour and Umami, maybe fat. The tongue is covered in different receptors for each of these, but it is unevenly distributed, with sweet/salty at the front, and butter at the back.

Question 26

Explain how smell functions, and (b) Outline the path from smell to brain?

Answer 26

(1) Odour receptors in the olfactory epithelium at the top of the nasal cavity (2) detect particular odors/chemical dissolved in mucus. (3) Particular chemical combine with particular receptors allowing us to smell.
(b) These synapses and fire directly to the olfactory bulb (not through the thalamus).

Question 27

Explain the role of the semicircular canals?

Answer 27

(1) The semicircular canals are three canals filled with thick fluid with hair cells in them, located at right angles to each other in the inner ear. (2) When the hair cells deform they fire action potential.
(3) This provides information about angular rotation in 3 dimension, allowing up to maintain balance, and also provides the signals for reflexive eye movements to keep out vision stable.
(4) When running/moving head around, our vision remains stable.

Question 28

Identify the Vestibular Sacs and Explain their role?

Answer 28

The Vestibular Sacs include the Utricle and Saccule.
Located in the inner ear, they contain thick fluid and hair cells. When the head moves, it causes the hair cells to bend which fires action potentials. This provides information about linear accelerations and gravity, helping us to remain upright. For example, when on a roller coaster.

Question 29

Relate the movement of the basilar membrane, and amplitude/pitch? how can speech be processed by the BM?

Answer 29

The amount of mechanical movement of the BM codes for amplitude, whereas place of maximum movement codes for pitch/frequency.

Speech is very complex, but the auditory system is able to break down complex waves into basic frequencies and amplitudes to process them.