Receptors Flashcards
Describe how a generator potential is established in a Pacinian corpuscle
- Mechanical stimulus - pressure deforms lamellae and stretch- mediated sodium ion (Na+) channels
- So Na+ channels in membrane open and Na+ diffuse into sensory neurone
○ Greater pressure causes more Na+
channels to open and more Na+ to enter - This causes depolarisation, leading to a
generator potential
○ If generator potential reaches threshold
it triggers an action potential
Explain what the Pacinian corpuscle illustrates
● Receptors respond only to specific stimuli
○ Pacinian corpuscle only responds to mechanical pressure
● Stimulation of a receptor leads to the establishment of a generator potential
○ When threshold is reached, action potential sent (all-or-nothing principle)
Explain the differences in sensitivity to light for rods & cones in the retina
Rods are more sensitive to light
● Several rods connected to a single neurone
● Spatial summation to reach threshold as enough neurotransmitter released to generate an action potential
Cones are less sensitive to light
● Each cone connected to a
single neurone
● No spatial summation
Explain the differences in visual acuity for rods & cones in the retina
Rods give lower visual acuity
● Several rods connected to a single neurone
● So several rods send a single set of impulses
to brain (so can’t distinguish between
separate sources of light)
Cones give higher visual acuity
● Each cone connected to a single neurone
● Cones send separate (sets of) impulses to brain
(so can distinguish between 2 separate sources of light)
Explain the differences in sensitivity to colour for rods & cones in the retina
Rods allow
monochromatic vision
● 1 type of rod / 1 pigment
Cones allow colour vision
● 3 types of cones - red-
, green- and blue-sensitive
● With different optical pigments → absorb different wavelengths
● Stimulating different combinations of cones gives range of colour perception
Cardiac muscle is myogenic. What does this mean?
It can contract and relax without receiving electrical impulses from nerves
Describe the myogenic stimulation of the heart and transmission of a
subsequent wave of electrical activity
1 Sinoatrial node (SAN) acts as pacemaker → releases regular waves of electrical activity across atria
○ Causing atria to contract simultaneously
2 Non-conducting tissue between atria / ventricles prevents impulse passing directly to ventricles
○ Preventing immediate contraction of ventricles
3 Waves of electrical activity reach atrioventricular node (AVN) which delays impulse
○ Allowing atria to fully contract and empty before ventricles contract
4 AVN sends wave of electrical activity down bundle of His, conducting wave between ventricles to apex where it branches into Purkyne tissue
○ Causing ventricles to contract simultaneously from the base up
Describe the roles of chemoreceptors, pressure receptors, the sympathetic
nervous system and effectors in controlling heart rate
Sympathetic nerve
1. Baroreceptors detect a fall in blood pressure and chemoreceptors detect a rise in CO2 concentration or a fall in blood PH
2. Which sends more frequent impulses to SAN along sympathetic neurones
3. So more frequent impulses sent from SAN to and from AVN
5. So cardiac muscle contracts more frequently
6. Heart rate increases
Where are chemoreceptors and pressure receptors located
aorta and carotid arteries
Describe the roles of chemoreceptors, pressure receptors, the parasympathetic nervous system and effectors in controlling heart rate
- Baroreceptors detect a rise in blood pressure and chemoreceptors detect a fall in blood CO2 concentration and a rise in blood PH
- Sends impulses to medulla and cardiac control centre
3.which sends more frequent impulses to SAN along parasympathetic neurones
4.So less frequent impulses sent from SAN to and from AVN
5.so cardiac muscle contracts less frequently
6.so heart rate decreases
