Drugs and Senses
Chapters 8a and 9
What are drugs?
• Chemical substances that affect the
central nervous system, causing changes
in physiology and often addiction.
Neuromuscular Junction
(NMJ) or Synapse
Communication Between Neurons
Normal Communication
Drugs stimulate the release of a
neurotransmitter
Drugs inhibit the release of a
neurotransmitter
Drugs can bind to receptors and
stimulate a response
Drugs can bind to receptors and
inhibit a response
Alcohol
• Depresses the Central
Nervous System.
• First blocks GABA
(inhibitory
neurotransmitter).
• Then blocks Glutamate
(excitatory
neurotransmitter).
http://home.howstuffworks.com/alcohol6.htm
Marijuana
• THC is the psychoactive
ingredient in marijuana.
• THC binds to
anandamide receptors in
the brain.
• Anandamide brings on a
feeling of “internal bliss.”
Stimulants Excite the CNS
• Cocaine
– Increases the neurotransmitters
dopamine and norepinephrine.
– Interferes with reuptake of
dopamine.
– Euphoria
– Fight or flight responses
Amphetamines
• Synthetic
• Increases the neurotransmitters
dopamine and norepinephrine.
• Active for hours.
• Inhibits the action of an
enzyme that normally breaks
down these two
neurotransmitters.
Caffeine
• Blocks adenosine, an
inhibitor.
• Adenosine inhibits
neurons from releasing
neurotransmitters.
Hallucinogenic Drugs
• Alter sensory perception.
• Increases the
neurotransmitters
serotonin,
norepinephrine, and
acetylcholine.
• Increase energy levels,
mood, sexuality.
Opiates
• Pain relief.
• Bind to natural
receptors that are
involved in the
perception of pain.
– Endorphins
Senses
•
•
•
•
•
•
Sense of Taste
Sense of Smell
Sense of Vision
Sense of Hearing
Sense of Touch
Sense of Equilibrium
Types of Sensory Receptors
• Chemoreceptor
– Chemical stimuli.
• Taste
• Smell
– Nociceptor- chemicals released by damaged tissue.
• Photoreceptor
– Light stimuli.
• Vision
• Mechanoreceptor
– Mechanical stimuli.
•
•
•
•
Touch
Pressure
Hearing
Equilibrium
• Thermoreceptor
– Changes in temperature.
• Temperature (cold and warmth receptors)
Taste Buds- chemoreceptors
•
•
•
•
•
Numbers- 10,000 on the tongue.
Shape- onion-like in morphology.
Location- along the sides of papillae.
Cell Division- replaced every 10 days.
Structure
– Taste cells.
• Microvilli (=taste hairs) have receptors
that generate electrical signals.
– Supporting cells.
• Sensitivity- respond to all 5 basic
tastes, but are more sensitive to
one or two than the others.
Taste Buds
Facial Nerve
Inferior parietal
Olfactory receptors- chemoreceptors
•
•
•
•
•
Numbers- 5 million olfactory receptors.
Size and Shape- similar to a postage stamp.
Location- roof of the nasal cavity.
Cell Division- replaced every 60 days.
Structure
– Olfactory receptor cells.
• Olfactory cilia with odorant receptors.
– Supporting cells.
• Sensitivity- 1,000 different types of receptors,
each controlled by a different gene. Together
able to detect 10,000 different odors.
Olfactory Cell Location and Anatomy
• Olfactory glands produce mucus that dissolves odorants.
Temporal Lobe and Limbic System
Temporal lobe
Olfactory nerve
Olfactory bulb
Amygdala
Sense of Vision- photoreceptors
• Numbers- ¼ billion photoreceptors.
• Eye- 25 mm in diameter (1 inch).
• Eyes- contain 70% of all the sensory
receptors in the human body.
• The eyeball has three layers
– Sclera- the white of the eye.
– Choroid- contains melanin that absorbs light.
– Retina- contains photoreceptors.
• The retina contains 2 types of photoreceptors.
– Rods- responsible for black and white vision.
– Cones- responsible for color vision.
Iris and Pupil
• Iris- regulates the
amount of light that
enters the eye.
– Smooth muscle fibers
automatically adjust
the size of the pupil.
• Pupil- opening at the
center of the iris.
Bright Dim
Light
Dark
Iris
Pupil
Dilated vs. Constricted Pupils
• Dilate- pupil becomes larger.
• Constrict- pupil becomes smaller.
• 16 fold variation between constricted and
dilated.
Constricted Normal
Dilated
Cornea and the Choroid
• Cornea and Lensrefract (bend) light
rays and focus light
on the retina.
Retina
Cornea
Lens
• Albert Einstein- proposed the Particle Model of
Light Theory in 1905.
– Visible light is composed of particles of energy called
photons.
Photoreceptors in the Eye
Structure and Function of the Retina
Optic Nerve
Occipital Lobe
Abnormalities of the Eye
• Distance Vision
– Nearsighted
• Close objects are seen
clearly.
• Long eyeball causes image
to focus in front of the
retina.
– Farsighted
• Distant objects are seen
clearly.
• Short eyeball causes image
to focus behind retina.
• Astigmatism
• Image is blurred.
• Irregular curvature of the
cornea or lens causes light
rays to focus unevenly.
Abnormalities of the Eye #2
• Color blindness
– Colors cannot be
distinguished.
– 75% of people have
poor green perception.
– 8-10% of males, <1%
females.
• X-Linked.
– A lack of or reduced
number of one of the
cone types.
4 Sex-Linked Traits:
1. Normal Color Vision:
A: 29, B: 45, C: --, D: 26
2. Red-Green Color-Blind:
A: 70, B: --, C: 5, D: -3. Red Color-blind:
A: 70, B: --, C: 5, D: 6
4. Green Color-Blind:
A: 70, B: --, C: 5, D: 2
Humors
• Vitreous Humor
– Embryonic, never replaced.
– Posterior chamber.
– Keeps the eyeball from
collapsing.
• Aqueous Humor
– Drained and replaced every 90
minutes.
– Anterior chamber.
– Supplies the cornea and lens
with nutrients and oxygen.
Glaucoma
Cataracts
• Leading cause worldwide of blindness.
• A lens becomes cloudy or opaque.
• Caused by
–
–
–
–
–
Natural aging. 50 or over.
Drug reactions.
Injury.
Diabetes.
UVB damage.
• At risk
– Smokers (2X).
– Guys named “Phil” and “Rupert”.
• Treatment- surgery, removal and replacement of
the lens.
Sense of Hearing
• Vibrating objects
create pressure
waves in the air
or water= sound.
• Pressure waves
vary in
– Amplitudevolume.
– Frequencypitch.
Anatomy of the Ear
Receiver
Amplifier
Transmitter
Section of the Cochlea
• There are 3 compartments in the cochlea
– Upper compartment- vestibular canal.
– Central compartment- cochlear duct.
• Contains “Organ of Corti.”
– Lower compartment- tympanic canal.
Temporal lobe
Vestibulocochlear Nerve
Sense of Equilibrium
• Rotational Equilibrium
– Cupula movement within the semicircular
canals detects rotation and/or angular
movement of the head.
• Gravitational Equilibrium
– Movement of the otolithic membranes within
the utricle and saccule is detects movement
of the head in vertical and horizontal planes.
Rotational
Equilibrium
Gravitational
Equilibrium
Vestibulocochlear Nerve