The sensory receptors

Question 1

Question: What is the Cochlea structure?

Answer 1

• Chambers filled with fluid
  Fluid vibrates when sound passes through
• Small hairs called stereocilia located in the chambers
• Stereocilia vibrate due to the fluid vibrations
• Vibration of stereocilia sends sound signals to the brain via electrical impulses

Question 2

What is the structure of the cochlea?

Answer 2

• The cochlea is filled with fluid and is comprised of several layers surrounding the main organ, also known as Corti,
• lined with thousands of tiny hairs called cilia.
• Made up of inner and outer hair cells embedded in the basilar membrane
• Short stiff fibres near window, long flexible fibres at the tip
• Low frequency sounds move the longer fibres near the tip (helicotrema)
• High frequency sounds vibrate hairs near the window

Question 3

Question: How do hair cells in the cochlea work?

Answer 3

1. Stereocilia are joined by tip links- fibres joined to a gated channel
2. Sound vibrations cause movement of endolymph
3. Tension in tip links opens the ‘trap door’
4. Depolarisation - K+ moves in and depolarises the cell. Voltage-gated calcium (Ca2+) channels open.
   5.Release of neurotransmitter - Influx of Ca2+ triggers glutamate (neurotransmitter) release at the synapse via exocytosis
5. Action potential - Causes an action potential in the cochlear branch of the vestibulocochlear nerve
   Impulse sent to brain – we can hear

Question 4

Question: What are the Papillae?

Answer 4

1. The tongue has papillae (little bumps on the top of your tongue that help grip food while your teeth are chewing)
2. Papillae contain taste buds

Question 5

Question: How do taste buds work in the papillae?

Answer 5

1. Found in the walls of papillae
2. Have gustatory hairs protruding from the top
3. Come into contact with taste molecules within the pore at the top in a fluid-filled funnel
4. Depolarisation - This causes ion channels to open and depolarisation of the cell and release of NT
   5.Impulse to brain - Causes associated sensory neurons to depolarise and the impulse travels back to the gustatory cortex
   Taste is determined by interaction between gustatory and olfactory input

Question 6

Question: What is olfaction?

Answer 6

1. Olfaction is the sensation of smell that results from the detection of aerosols in the environment
2. Odour detection occurs at the top of the nasal cavity

Question 7

Question: How are odour molecules detected?

Answer 7

1. Odour molecules dissolve in a layer of mucus over the olfactory epithelium so they can react with receptors
2. Olfactory epithelium contains millions of receptor cells
3. Each cell has a single dendrite that extends to the outermost layer of the epithelium and has cilia extending over the epithelium
4. Odorant molecules bind with the cilia and cause depolarisation
5. The generated action potential travels along the receptor cell axon to the ol