Transcript The Other Senses

Unit IV: Coordination
The Other Senses
Chapter 13 – pgs 454-459
Chapter 15 – pgs 497-517
Chapter 14 – pgs 488-489
General Properties of Receptors
1. Modality
2. Location
– Projection pathways
– Sensory projection
Stimulus
Normal
Increased
Normal
3. Intensity
• Frequency
• # of fibers
• Type of fibers
4. Duration
• Tonic vs. Phasic
• Adaptation
Stimulus
Normal
Increased
Frequency
of action
potentials
Frequency
of action
potentials
Time
Tonic receptors
Time
Phasic receptors
Normal
Classification of Receptors
• Stimulus modality:
– chemo-, thermo-, mechano-, photo- receptors and nociceptors
• Origin of stimulus
– interoceptors
– proprioceptors
– exteroceptors
• Distribution of Receptors
– general senses
– special senses
Somesthetic Senses
Unencapsulated Nerve Endings
Hair
Free Nerve Endings
Respond to pain,
and temperature Free nerve
stimuli
endings
Sensory
nerve
Root Hair Plexus
Monitor distortions and
movements
Hair shaft
Root hair
plexus
Tactile Discs and Merkel Cells
Fine touch and pressure
receptors
Merkel cells
Tactile disc
Sensory nerves
General Senses
Encapsulated Nerve Endings
Meissner/Tactile Corpuscles
Fine touch and pressure
and low-frequency vibration
Capsule
Dendrites
Tactile corpuscle
Hair
Dermis
Afferent fiber
Pacinian/Lamellated Corpuscles
Collagen fibers
Dendrite
Dermis
Sensory nerves
Ruffini Corpuscles
Pressure and
distortion of the
Capsule
Dendrites deep dermis
Afferent fiber
Deep pressure, especially
pulsing or high-frequency
vibrating stimuli
Somesthetic Projection Pathways
• 1st order neuron (afferent neuron)
– fast vs. slow
– end in medulla oblongata or spinal cord
• 2nd order neuron
– decussation
– end in thalamus
• 3rd order neuron
– primary somesthetic cortex of cerebrum
Pain
• Nociceptors
• Types:
1. Fast (first) pain
2. Slow (second) pain
• Stimulation of pain fibers
– Bradykinin, serotonin, histamine, prostaglandin, K+ ions
Projection Pathways for Pain
Referred Pain
• Misinterpreted pain
– cardiac pain felt in shoulder or arm because both send pain input
to spinal cord segments T1 to T5
– brain “assumes” visceral pain is coming from skin
Liver and
gallbladder
Liver and
gallbladder
Lung and diaphragm
Heart
Stomach
Pancreas
Small intestine
Appendix
Ureter
Colon
Urinary
bladder
Kidney
Analgesic Mechanisms of the CNS
• Endogenous opioids (enkephalins, endorphins and dynorphins)
– neuromodulators: inhibit Ca+ influx into pre-synaptic neuron
or open K+ channels in post-synaptic neuron
Chemical Sense
Taste
Circumvallate Papillae
Contains as many as 100 taste buds
• Gustation
• Lingual papillae:
Pharynx
Taste
buds
Vallate papillae
Fungiform Papillae
Contain about five taste buds each
Filiform Papillae
Provide friction
Taste Bud Structure
•all look alike
• Taste cells (epithelial)
– taste hairs
– taste pore
• Replaced every 7-10 days
-Vallate papillae
Physiology of Taste
•
Molecules must dissolve
in saliva
•
5 primary sensations
1. Sweet
2. Salty
Cranial Nerves
3. Sour
The facial nerve
(VII)
4. Bitter
5. Umami
The glossopharyngeal
nerve (IX)
The vagus nerve (X)
Start
Receptors respond
to stimulation.
Synapse in the thalamus.
Then projected to the
primary sensory cortex.
The axons of the
postsynaptic neurons
cross over
Solitary nucleus of
the medulla oblongata.
Chemical Sense
Smell
• Olfaction
• Olfactory mucosa vs. respiratory mucosa
• Olfactory cells (neurons)
– axons travel thru ethmoid
– olfactory bulb (pair)
– olfactory hairs
– survive 60 days
Olfactory tract
Cribriform
plate of
ethmoid
Olfactory
mucosa
Superior nasal
concha
Physiology of Smell
• 350 kinds of olfactory receptors
• Glomeruli
• Hydrophilic odorants diffuse freely
• Hydrophobic odorants are transported by proteins
Projection Pathway
Step 1: The binding of an
odorant converts ATP to
cyclic-AMP (cAMP).
Step 2: The cAMP opens
sodium channels.
RECEPTOR
CELL
Inactive
enzyme
Step 3: An action potential is
triggered in the axon, and
the information is relayed to
the CNS.
Sodium
ions enter
Active
enzyme
Depolarized
membrane
Odorant
molecule
MUCOUS
LAYER
Closed
sodium
channel
•Adaptation – synaptic inhibition in olfactory bulb
Stretch Receptors
• Baroreceptors
− monitor pressure changes
− free nerve endings found in:
• blood vessels
• tubes of respiratory, digestive, and urinary tracts
• Chemoreceptors
− detect small changes in specific chemical or compound
concentration
− reflexive control of cardiopulmonary functions
− found in:
• medulla oblongata
• carotid arteries
• aortic arch
Exam 4
Chapters: 11 - 15
• Fill in the blank
• Multiple Choice
• Matching
• Short answer
• True/False
Lab Practical
• Lab indentification
• Questions from lab manual
review lab questions and homework
• All fill in the blank