Topic 8 Flashcards
What are primary receptors
Receptors that generate action potential upon receiving a stimulus
What are secondary receptors
Receptors made up of specialized cells (not neurons) that are sensitive to a specific stimulus. These cells synapse with normal neurons to transfer impulse to CBS
Types of receptors
1.chemoreceptors
2.proprioreceptors
3. Thermoreceptors
4. Mechanoreceptors
5.photoreceptors
How do sensory receptors work ?
• Receptor cell receives stimulus
•Na+ ions enters the membrane changing the permeability
• sets up generator potential
• if generator potential passes threshold potential, the action potential is generated in the sensory neuron
Convergence
When several neurons receive or transmit impulse to a single neuron. Useful adaptation for increasing sensitivity of sensory system(to a low level stimuli)
What is the wavelength detected by eyes
400-700nm
Structures of eye that can control the amount of light that enters
Iris, pupil, lens, cornea and vitreous humour and aqueous humour
Type of photoreceptors found in the retina
Rods and cones
Where are rods found
Spread around the entire retina except for the fovea
Function of rods
Provide black and white vision and very sensitive to light
Why are rods not tightly backs
Several of them synapse with one neuron only
Why do rods not give clear picture
Several rods need to be stimulated at the same time to cause an action potential
Why are rods sensitive to low lights
Several sensory receptors converge to one neuron so only need a small stimulus to produce several small action potential which together make a large action potential
Pigment present in rods
Rhodopsin
What is rhodopsin made of
Retinol and Opsin
Isomers of retinol
What happens when a photon hits rhodopsin
The cis retinol converts to trans retinol, this changes the shape of retinol which causes the rhodopsin molecule to break into retinol and opsin
Bleaching
The photochemical break down of rhodopsin into retinol and opsin
How does bleaching create action potential?
• Leads to cascade of chemical reactions
• sodium channels closed, Na ions can’t enter so interior becomes and more negative hyperpolarised
• this hyperpolarisation acts as generator potential
• several receptor stimulated, neurotransmitters released into synapse with bipolar cell
• action potential generated in bipolar cell hence action potential generated in sensory neuron
• all sensory neuron meet at one point to the optic nerve
What makes up CNS
Brain and spinal cord
Function of brain
Processes information into instructions
Function of spinal cord
Connect all the neurons to the brain
What is brain made of
Grey matter - contains relay neurons
While matter-contains long myleinated axons
