UNIT 4: N.S ll - SENSORY INPUT

What are the 2 types of GP on a receptor membrane?

→ Generator potential

→ receptor potential

Where can receptors be located?

→ dendrites (as proteins) on unipolar neurons

→ as individual cells that synapses to neurons

What occurs when a receptor is stimulated in the afferent n.s?

→ stimulus causes opening of ligang gated channels (Na⁺) on receptor membrane

→ greater potential (gp) occurs on receptor membrane - stimulus turns electrical

What are the 2 types of generator potentials that can occur on a cell membrane?

→ generator potential

→ receptor potential

Describe generator potentials

→ G.P that occurs on 1st order neurons

→ G.P occurs on dendrites of 1st order neuron and A.P occurs on the same neuron - due to free nerve endings detecting stimuli - therefore usually occurs on unipolar neurons

Describe receptor potentials

→ separate cell from sensory neuron

→ receptor potential occurs on receptor cell, which releases nt onto dendrites of sensory neuron

→ ex: hair cells

What are the types of receptors that detect stimuli?

→ Phasic & Tonic receptors

Explain Phasic receptors and provide an example

→ responds to stimulus change

→ If the presence of the stimulus stays constant, therefore adaption - decrease in sensitivity and stops sending A.P

→ examples: mechanoreceptors and olfactory receptors

• putting hat on:

• mechanoreceptors detect stimuli (through pacinian/lamelled corpuscles - phasic receptors), sends initial burst of A.P (feeling the hat on head)

• overtime, receptors adapt & A.P frequency to CNS decreases - stimulus is maintained at a constant strength

Explain Tonic Receptors and provide examples

→ used w/ a presence of a constant stimulus therefore frequency of AP stays constant (due to feeling the stimulus the same way) NOT ADAPTATION

→ continuously monitors sensory info - used to protect body (to stop body from being in pain)

→ ex: proprioceptors (used to constantly keep posture & balance) , nociceptors (pain)

What does the term “hard-wired“ mean?

brain always know what receptor receives the stimuli and where the signal will be sent in the brain

How does the brain perceive stimuli at different strengths?

→ determined by frequency of AP’s being sent to CNS

→ stronger stimulus = higher AP frequency & vice versa

→ stronger stimulus will also activate more receptors

→ ex: knowing the difference of feeling a brick and a feather

• brick is heavier, therefore has a stronger stimulus therefore will activate more receptors to send signal to