Topic 6 - Sensory nervous system Flashcards
What do sensory receptors respond to?
the respond to environmental stimulus by causing action potentials in sensory neurons.
Where do visual, auditory olfactory & gustatory sense go to in brain?
- Visual = occipital lobe
- Auditory = temporal lobe
- Olfactory (smell) = temporal lobe
- Gustatory (taste) = frontal lobe
Where and what is the sensory cortex?
- It’s a strip of brain tissue in the parietal cortex
- processes input related to touch, joint & muscle position, pain, temperature & itch.
- Has diff. parts to correspond to diff. parts of body
What does the sensory system comprise of?
- Sensory neurons that have sensory receptors on ends OR synapse with a sensory cell
- parts of brain involved with sensory perception
What are the types of sensory receptors?
- Simple = have neurons with free nerve endings (e.g detection of muscle position)
- Complex = nerve endings enclosed in connective tissue (e.g touch receptors)
- Special senses receptors = on sensory cells that synapse with sensory neurons (taste receptors, photoreceptors in eye & auditory receptors)
- Na+ movement -> graded potential
- internal & external environ- sensation once processed by sensory cortex
- must be processed in cerebral cortex otherwise X awareness (not all the time are things processed e.g blood pressure)
What does the stimulus for the sensory system result in?
- Na+ movement into cell causing graded potential.
- Info. about external/internal environment -> sensation
*Note - sensations can be conscious or subconscious
What are some examples of conscious information processed?
- Vision
- Hearing
- Taste
- Smell
- Touch
- Temperature (CAN BE BOTH***)
- Pain
- Itch
- Proprioception (CAN BE BOTH***)
What are some examples of subconscious information processed?
- Muscle length/tension
- Blood pressure
- pH & O2 content in blood
- Lung inflation
- Temperature (CAN BE BOTH***)
- Blood glucose
- Proprioception (CAN BE BOTH***)
What are the 4 main types of sensory receptors?
- Mechanoreceptors = activated by movement (e.g detect pressure, touch or stretching of skin)
- Thermoreceptors = activated by temperature changes (e.g skin alerting when body too hot/cold)
- Chemoreceptors = activated by dissolved chemicals (e.g gas changes like O2/CO2 & detect taste & smell)
- photoreceptors = activated by light (e.g rods & cone cells in retina of eye)
How do sensory receptors send a message of a sensation to the brain?
Receptors “sense” the sensation & convert it into graded potentials on sensory neuron/cell
- This causes depolarisation of sensory cell causing it to release transmitter
- This causes graded potentials on sensory neuron
- The message then gets sent to the brain via action potential
What is factors can alter sensory perception?
- Sensory receptor mechanisms (adaptation)
- Sensory pathway mechanisms (
- Characteristics of individual (genetics/environmental)
- Whether consciousness is reached
- Damage, disease state, disorders
- Drugs
What is a tonic receptor?
- Tonic receptors = continuous activation of sensory neurons for as long as stimulus is present (e.g nociceptors)
- This means receptors don’t have to keep activating sensory neuron
What is a Phasic receptor?
Allows the body to ignore old info which doesn’t threaten homeostasis/well-being
What are Nociceptors?
- They’re sensory receptors that sends signal about pain perception
- Since respond to chemical/mechanical/thermal stimulus, receptors could be chemoreceptors/mechanoreceptors/thermoreceptors
What is TRPV1 (transient receptor potential vanilloid 1)?
- It’s a chemoreceptor & thermoreceptor (is ion channel)
- It’s activated by capsaicin or heat
- When there’s too much activation of this receptor, it causes pain
What is TRPM8 (transient receptor potential melastatin 8)?
- It’s a chemoreceptor & thermoreceptor (is ion channel)
- It’s activated by menthol and cold
- When there’s too much activation of this receptor, it causes pain.
- e.g temp in environment (1 degree activates TRPM8 mildly) changes of 15+ degrees, cold sensation felt as pain
What happens after TRPV1 & TRPM8 are activated?
- A fibres (nerve fibres carry pain info. that’s sharp/localised to 1 area
- C fibres (nerve fibres) carry pain info. that’s dull or diffuse.
- Carry info. from receptors to spinal cord
- Secondary/ascending neurons then carry info to sensory cortex where pain is perceived.
*NOTE: if only slight stimulation, pain signal doesn’t reach & stops at spinal cord
What are the cells/receptors involved in sensing taste?
- Taste buds have 50-100 taste cells
- Taste cells have chemoreceptors
- Diff. taste cells are responsible for detection of diff. tastes
*Fun fact: taste cells replace by new taste cells ~2wks
What are the 5 types of taste receptors on each taste cells & what activates them?
- Sweet = sugars (e.g glucose)
- Sour = unknown (H+ ions)
- Salty = Na+ ions bind to it
- Bitter = quinine (found in tonic H2O & malaria med.)
- Umami = aa’s (e.g glutamate)
Where can bitter, sweet and umami receptors also be found (excluding tongue)?
- stomach
- intestine
- pancreas
*Note: helps influence appetite & reg. insulin production
What occurs after activation of taste receptors?
- Depolarisation occurs in taste cell
- Transmitter released bind to other receptors assoc. w/ sensory neuron (synapse in thalamus)
- Other neurons then carry info. about taste to gustatory cortex (in frontal lobe)
