Download SENSES ANSWERS

SENSES ANSWERS
4)
Sequences which make sense
Rearrange the following 10 concepts relating stimulation of a Pacinian corpuscle into
a numbered chronological sequence which shows how one leads to the next (as in a
concept map).
1. Vibrator applied to skin
7.Firing of action potentials down axon
5.Generator potential develops at initial segment
10.Rapid adaptation of membrane potential
4.Na influx and K efflux occurs
8.Synaptic transmission occurs in thalamus
2.Deformation of connective tissue layers
6.Threshold for action potential reached in axon
3.Cation channels mechanically opened
9.Awareness of sensation occurs in somatosensory cortex
1. Vibrator applied to skin
↓
2.Deformation of connective tissue layers
↓
3.Cation channels mechanically opened
↓
4.Na influx and K efflux occurs
↓
5.Generator potential develops at initial segment
↓
6.Threshold for action potential reached in axon
↓
7.Firing of action potentials down axon
↓
8.Synaptic transmission occurs in thalamus
↓
9.Awareness of sensation occurs in somatosensory cortex
↓
10.Rapid adaptation of membrane potential
Concept maps
Touch pressure sensory neurone
Temperature perception
SENSES ANSWERS from Reflexes
Misconception MCQ
Answer d)
Extra notes
Pupillary Reflexes ( From Senses Practical notes)
The pupillary reflexes, particularly the light reflexes, are of great clinical importance.
........................................................................................................................................
Knowing these actions you can predict the consequences of applying drugs to the eye,
as is done in visual examinations. What will happen to pupil diameter and lens power
if (i) atropine (ii) adrenaline is used?
(i)
Atropine is a muscarinic cholinergic antagonist, so will block transmission
from all the motoneurons onto the smooth muscles in the parasympathetic
pathways. The circular muscle of the iris of both pupils will relax,
resulting in dilation of both pupils. The ciliary muscle of the lens will also
relax, resulting in flattening of the lens and less power.
(ii)
Adrenaline is a sympathetic agonist, so will stimulate the smooth muscles
activated by sympathetic pathways. The radial muscle of the iris of both
pupils will contract, also resulting in dilation of both pupils. The ciliary
muscle of the lens will also relax, producing the same lens flattening and
decreased power as with atropine.
Concept map
1.Light
shone into
left eye
2. APs travel along
left optic nerve
to synapse in
left & right Edinger
-Westphal nuclei
7. Pupillary
constriction
occurs
3. APs travel along
left & right oculomotor
nerves to synapse in
ciliary ganglia
6. APs in sympathetic
nerves to radial dilator
smooth muscle cells of
both pupils are inhibited
4. APs travel in parasympathetic nerves
to circular smooth
muscle cells of irises
of both pupils
5. Simultaneously
descending inputs from
cortex, hypothalamus,
midbrain are inhibited