Lecture 13: Sense Organs

Question 1

what are sense organs comprised of?

Answer 1

• nerve fibres and tissues
• somatic vs visceral
• general vs special

Question 2

somatic vs visceral

Answer 2

somatic: surface of the body or skeletal musculature
visceral: within internal organs

Question 3

general vs special

Answer 3

general: receptive to touch, pain, and temp
special: localised structures receptive to other sensory input

Question 4

what are chemoreceptors and how do they work?

Answer 4

triggers sensory impulses when in contact with chemical stimuli; responsible for taste and smell
- taste receptors and olfactory receptors

Question 5

what are the parts responsible for olfaction and their function?

Answer 5

• olfactory epithelium: sensitive to odors
• olfactory bulb: cell axons synapse with mitral cells
• olfactory tract: mitral cell axons extend to telencephalon

Question 6

what is the evolution of olfactory in fish

Answer 6

olfactory epithelium in paired nasal sacs; excurrent opening enters mouth cavity

Question 7

what is the evolution of olfactory in tetrapods

Answer 7

• separate external nares and internal nares
• nasal chambers allows expansion of passage

Question 8

what are radiation receptors?

Answer 8

receptors in nocturnal vertebrates that detect electromagnetic radiation

Question 9

what are photoreceptors?

Answer 9

photosensitive cells that control light intensity and the way color is perceived

Question 10

the retina has 3 layers, what are they and what do they do?

Answer 10

outer layer: photosensitive cells (rods and cones)
middle layer: bipolar and horizontal cells transmit impulses from rods and cones
inner layer: cells convey impulses to brain

Question 11

what are mechanoreceptors?

Answer 11

• responds to small changes in mechanical pressure
• hair cells

Question 12

what do the 3 parts of the tetrapod ear do?

Answer 12

• external: passage from exterior to eardrum
• middle: transmission of sound
• inner: balance (vestibular apparatus) and hearing (cochlea)

Question 13

what is the function of the vestibular apparatus?

Answer 13

• maintains balance and tracking orientation
• contains endolymph and perilymph fluids
• semicircular canals respond to rotational movements of head
• cristae: modified neuromasts

Question 14

what are the 2 chambers of vestibular apparatus?

Answer 14

1. utriculus
2. sacculus

Question 15

what are electroreceptors and what do they do?

Answer 15

modified neuromast organs located in pits; detect objects disrupting electrical fields, electrical signals produced by others, and weal electrical signals

Question 16

what species have electroreceptors

Answer 16

• elephantfish
• platypus use receptors to fid prey and they attack batteries