Module 9: The Peripheral Nervous System Flashcards
(171 cards)
1
Q
What two divisions can the PNS be split into?
A
The efferent and afferent divisions.
2
Q
Where do efferent motor neurons send their signals?
A
Efferent motor neurons send signals from the CNS to the effectors.
3
Q
Where do afferent sensory neurons send their signals?
A
Afferent sensory neurons send signals from receptors back to the CNS.
4
Q
What two systems can the efferent division of the PNS be divided into?
A
The somatic motor nervous system and the autonomic nervous system.
5
Q
What type of effectors does the SMNS control?
A
Skeletal muscle.
6
Q
What type of effectors does the ANS control?
A
Smooth muscle, cardiac muscle, and glands.
7
Q
What is the most prominent functional difference between the ANS and the SMNS?
A
The SMNS is voluntary while the ANS is involuntary.
8
Q
Where is the cell body of the preganglionic neuron of the ANS located?
A
Either the spinal cord or the brain stem.
9
Q
Where does the preganglionic neuron of the ANS synapse with the postganglionic neuron?
A
The autonomic ganglion.
10
Q
Where is the cell body of the postganglionic neuron found?
A
The autonomic ganglion.
11
Q
Ganglion
A
Neuron cell bodies outside the CNS.
12
Q
Compare and contrast the neuron axons of the SMNS and the ANS.
A
SMNS neuron axons are myelinated. In the ANS, the preganglionic neuron’s axon is myelinated, but the postganglionic neuron’s axon is not.
13
Q
Compare and contrast the neurotransmitters of the ANS and the SMNS.
A
The SMNS only uses acetylcholine at the neuromuscular junction. In the ANS, the preganglionic neurons use ACh. Some postganglionic neurons use norepinephrine as well.
14
Q
Compare and contrast the response from the effectors in the ANS and the SMNS.
A
The SMNS is an excitatory system, but the ANS is both excitatory and inhibitory.
15
Q
What two divisions is the ANS divided?
A
The sympathetic division and the parasympathetic division.
16
Q
What is the function of the sympathetic division?
A
It rouses the body for physical activity, increases the rate and strength of the heartbeat, raises the blood pressure, and stimulates the liver to release glucose into the blood and provide a source of quick energy.
17
Q
What is the function of the parasympathetic division?
A
The parasympathetic division slow the heart rate, lowers the blood pressure, and takes care of “housekeeping” activities such as causing the smooth muscles in the stomach to churn during digestion.
18
Q
Where do all sympathetic nerves exit the CNS?
A
They exit from the thoracic and lumbar regions of the spinal cord.
19
Q
Where do parasympathetic nerves exit the CNS?
A
Some exit from the brain while others exit from the sacral (lower) region of the spinal cord.
20
Q
Compare and contrast the length of the pre and postganglionic neurons of the sympathetic and parasympathetic divisions.
A
Parasympathetic: preganglionic neuron is long and postganglionic neuron is short.
Sympathetic: preganglionic neuron is short and postganglionic neuron is long.
21
Q
How does the sympathetic division interact with the heart?
A
It increases the rate and force at which the cardiac muscle contracts, thus increasing the heart rate and strength of the heart’s contraction.
22
Q
How does the parasympathetic division interact with the heart?
A
It slows the rate at which the cardiac muscle contracts.
23
Q
How does the sympathetic division interact with the lung?
A
It causes the bronchial tubes to dilate and let more air into the lungs.
24
Q
How does the parasympathetic division interact with the lungs?
A
It causes the bronchial tubes to constrict and decreases the amount of air intake.
25
How does the sympathetic division interact with the digestive system?
It slows the activity. When it is active, digestive juices are not secreted, the digestive organs do not push digesting food along, and the blood flow to the digestive organs decreases.
26
How does the parasympathetic division interact with the digestive system?
It increases secretion and movements and stimulates the salivary glands to create more saliva.
27
How does the sympathetic division interact with vision?
It stimulates dilation of the pupil of the eye in order to let more light in and relaxes the muscle that controls the eye's lens, which lets you see far away.
28
How does the parasympathetic division interact with vision?
It stimulates contraction of the pupil to reduce the amount of light that enters the eye and contracts the muscle so that the lens becomes more round and allows you to see nearby.
29
How does the sympathetic division interact with urination?
It relaxes the bladder.
30
How does the parasympathetic division interact with urination?
It contracts the bladder.
31
Name some parts of the body that are innervated by both the sympathetic and parasympathetic division.
The eye, heart, bladder, lungs, and many parts of the digestive system.
32
What division controls the lacrimal glands?
The parasympathetic division.
33
Name some functions of the sympathetic division.
It innervates blood vessels and constricts blood vessels in the abdominal organs, which allows blood to flow more freely to the tissues that need extra nutrients and oxygen. It also stimulates the liver to increase the amount of glucose released and contracts the arrector pili muscles.
34
What do the hormones epinephrine and norepinephrine do?
They cause the liver to release more glucose into the bloodstream, constrict the blood vessels in the abdominal organs, and cause the heart rate to increase.
35
When the sympathetic division wants to increase the heart rate, why does it also stimulate the adrenal medulla?
Epinephrine and norepinephrine prolong the effects of the sympathetic division's direct innervation and allow the heart rate to maintain its faster beat for some time.
36
What controls whether the parasympathetic division or sympathetic division is in control of the heart?
The autonomic reflexes.
37
Where are the control centers for the autonomic reflexes located?
The medulla oblongata, the spinal cord, and the hypothalamus.
38
Fight-or-flight response
The stimulation of the sympathetic division of the ANS by the limbic system in response to fear.
39
Sensory receptor
An organ that responds to a specific type of stimulus by triggering an action potential on a sensory neuron.
40
What three ways can receptors be classified based on location?
They can be classified as somatic receptors, visceral receptors, or special receptors.
41
Somatic receptors
Sensory receptors in the skin, muscle, and tendons.
42
Visceral receptors
Sensory receptors in the internal organs.
43
Special receptors
Sensory receptors in specific locations.
44
Where are somatic receptors found?
On or near the surface of the body, in the skin, muscles, and tendons.
45
Where are visceral receptors found?
They are located in the viscera, a Latin term meaning "internal organs."
46
Where are special receptors found, and what sense are mediated by them?
They are found in specific locations and mediate taste, smell, hearing, and vision.
47
What five ways can a sensory receptor be classified based on type (what it responds to)?
It can be classified as a mechanoreceptor, thermoreceptor, photoreceptor, chemoreceptor, or nociceptor.
48
Mechanoreceptors
Sensory receptors that respond to movement, whether it is light touch, vibration, or pressure.
49
Thermoreceptors
Sensory receptors that respond to heat or cold.
50
Photoreceptors
Sensory receptors that respond to light.
51
Chemoreceptors
Sensory receptors that respond to chemicals.
52
Nociceptors
Sensory receptors that respond to several types of excess stimulation, which is termed pain.
53
Where are thermoreceptors generally located?
The surface of the body.
54
Where are photoreceptors located?
The retina of the eye.
55
Where are chemoreceptors located, and what do they do?
Chemoreceptors are located in several different parts of the body. Chemoreceptors provide the sense of taste and smell and monitor pH and the level of oxygen in the blood.
56
Simple receptors
Relatively small sensory receptors distributed widely over the body.
57
Complex receptors
Sensory receptors that provide the five special senses.
58
What are the five special senses?
Taste, smell, hearing, balance, and vision.
59
What requirements must be met to be aware of a stimulus?
The stimulus must be detected from the environment, the body must have sensory receptors that can respond to the stimulus, and the stimulus must be equal to or greater than the receptor's threshold.
60
Projection
The ability of the cerebral cortex to determine where a stimulus occurs.
61
Modality
The ability of the brain to determine what type of receptor is sending signals so it can decide what kind of stimulus caused the action potentials.
62
How is modality accomplished in the cerebral cortex?
There are thin layers in the cerebral cortex, and each layer is stimulated by a different kind of receptor. So, the brain interprets the modality of the signal by the layer of the cortex that is stimulated.
63
Adaptation of a receptor
The ability of a receptor to stop responding or slow its response, even if the stimulus remains constant.
64
What are the two types of somatic receptors?
Cutaneous receptors and proprioceptors.
65
Cutaneous receptors
Receptors in the skin.
66
Proprioceptors
Receptors in the skeletal muscles and tendons.
67
Where are free nerve endings found and what do they detect?
They extend into the epidermic and branch out until they end. They detect heat, cold, itch, and pain.
68
Where are hair follicle receptors found, and what do they detect?
They are found in the hair follicle which is epidermal tissue that goes deep into the dermis. The receptors detect movement of the hair.
69
Where are Pacinian corpuscles located and what do they detect?
They are found deep within the dermis and detect pressure.
70
Where are Ruffini's end organs located and what do they detect?
They are found in the deeper part of the dermis and respond to pressure and stretching of the skin.
71
Where are Merkel's disks located, and what do they detect?
They are found in the most superficial layers of the skin and detect the lightest touches.
72
Where are Meissner's corpuscles located and what do they detect?
They are found throughout the dermal papillae and are involved in two-point discrimination.
73
What are the two basic types of proprioceptors?
Golgi tendon organs and muscle spindles.
74
Muscle spindle
A mechanoreceptor located within the skeletal muscle that responds to stretch.
75
Golgi tendon organ
A proprioceptor found in the tendon that responds to tension.
76
Proprioception
Body position, or a sense of where you are in space.
77
Olfaction
The sense of smell.
78
Where do the receptors for the sense of smell reside?
The olfactory epithelium.
79
Cribriform plates
Bones that protect the olfactory bulbs.
80
Olfactory foramina
Tiny holes in the cribriform plates.
81
What shape are the olfactory neurons?
They are bipolar with one dendrite and one axon.
82
Volatile substance
A substance that can evaporate into a vapor so that it becomes airborne.
83
What characteristics must a substance have in order to be smelled?
It must be volatile, somewhat water-soluble, and somewhat lipid-soluble.
84
The gustatory sense
The sense of taste.
85
What are the four distinct forms of papillae on the tongue?
Filiform, circumvallate, fungiform, and foliate papillae.
86
Where are the circumvallate papillae on the tongue?
The are concentrated near the back of the tongue.
87
Where are the fungiform papillae located on the tongue?
The are distributed irregularly over the entire upper surface of the tongue.
88
Where are the foliate papillae located on the tongue?
They are located on the sides of the tongue.
89
What two types of cells make up a taste bud?
Gustatory cells and the supporting cells.
90
How does a taste bud stimulate an action potential?
Unlike the olfactory receptors, the gustatory receptors do not directly generate action potentials. Instead, they release neurotransmitters when stimulated, which then generate action potentials on an associated afferent nerve.
91
What must happen in order for the taste buds to function?
The food we are eating must dissolved in the saliva, which then enters the taste pore. Chemicals dissolved in the salvia then bind to chemical receptors in the gustatory hairs, and the gustatory cell releases a neurotransmitter, which stimulates an action potential on the afferent nerve.
92
What are the five taste sensations?
Sweet, salty, sour, bitter, and umami.
93
What are the three components of the ear?
The external ear, the middle ear, and the inner ear.
94
What structure forms the shape of the outer ear?
The auricle.
95
What is the canal that leads from the external ear to the eardrum called?
The external auditory meatus.
96
What three regions is the inner ear divided into?
The vestibule, the semicircular canals, and the cochlea.
97
What two senses compose the sense of balance?
Static equilibrium and dynamic equilibrium.
98
Static equilibrium
Determines the orientation of the head relative to the pull of gravity. In other words, it helps the body determine whether the head is being held up straight, bowed, leaned to one side, and so forth.
99
Dynamic equilibrium
Helps determine the rotation and acceleration of the head. This allows us to maintain balance as we move.
100
What two parts make up the vestibule?
The saccule and the utricle.
101
How are the maculae of the saccule and utricle oriented?
Saccule: Perpendicular to the base of the skull.
Utricle: Parallel to the base of the skull.
102
What four structures make up a macula?
Support cells, hair cells, the gelatin matrix, and the otoliths.
103
Kinocilium
The hair (cilium) that is longer than the other hairs in the ear.
104
Sterocilia
The other hairs (cilia) besides the kinocilium.
105
How does the inner ear give us a sense of static equilibrium?
When the head moves, the heavy otoliths within the gelatinous matrix move, causing the stereocilia to move. If the stereocilia move toward the kinocilium, the hair cell causes an action potential to form on the sensory neuron. If the stereocilia move away from the kinocilium, the hair cell ceases to make action potentials on the sensory neuron.
106
Where does the sense of dynamic equilibrium originate?
The semicircular canals.
107
Ampullae
Bulges in the end of semicircular canals that contain the receptors that give us our sense of dynamic equilibrium.
108
How does the ear detect dynamic equilibrium?
This sense starts with a gelatinous cupula that floats in the fluid of the inner ear. When it is moved by the movement of the fluid, it will stimulate by its movement what we call the crista ampullaris. In the crista ampullaris there are hair cells that are embedded the cupula. Those hair cells respond to the motion of the cupula, creating action potentials on the associated sensory neurons.
109
After the the fluid in the inner ear moves, moves the cupula, and stimulates an action potential from the hair cells to the sensory neurons, where do the action potentials go?
They go to the balance center (the vestibular nucleus) in the medulla oblongata. From the medulla, information is sent to the cerebellum.
110
What does the amplitude of a sound wave determine?
The loudness of the sound.
111
What does the frequency of a sound wave determine?
The pitch.
112
Describe the chain of vibration conversions in the ear to hear a sound wave.
Sound wave vibrations are collected in the auricle and travel down the external auditory meatus to the tympanic membrane, which then converts those vibrations into vibrations of itself. The vibrations move to the auditory ossicles, to the oval window, to the fluid in the cochlea, and then to the basilar membrane.
113
What three bones compose the auditory ossicles?
The malleus, incus, and stapes.
114
How does the ear distinguish frequency?
The location of the vibration on the spiral organ determines the frequency.
115
Describe the results in the ear of high-frequency vibrations.
The high-frequency vibrations disturb the basilar membrane near the oval window, which causes vibrations in the tectorial membrane. As the membrane vibrates, it brushes against the hair cells of the spiral organ. The movement of those hair cells at the base of the spiral organ triggers action potentials in their associated sensory neurons.
116
Describe the results of low frequency vibrations in the inner ear.
The low frequency vibrations cause vibrations in the basilar membrane at the apex, or the far end of the spiral organ. This triggers vibrations in the tectorial membrane, which touches the hair cells at the apex of the spiral organ. The movement of these hair cells triggers action potentials on their sensory neurons.
117
What two structures are designed to protect the eye?
The palpebrae (eyelid) and eyelashes. These aid in spreading tears, the second layer of protection.
118
What is the purpose of the lacrimal glands?
They produce tears which moisten the eye and wash away foreign objects that make it past the eyelids and lashes.
119
What disinfectants are found in tears?
Tears contain antibodies and an enzyme called lysozyme, which is antibacterial.
120
How are tears drained away?
Tears drain away into the nasal cavity via four ducts, one on each palpebra, called lacrimal canaliculi.
121
Lacrimal canaliculi
Ducts in the eye through which tears drain away.
122
Puncta
Openings in the lacrimal canaliculi that drain away tears.
123
What two conditions can cause crying?
A foreign substance in the eye or as a result of emotions.
124
What are the three coverings or tunics of tissue called that compose the eye?
The fibrous tunic, the vascular tunic, and the nervous tunic.
125
What structures compose the fibrous tunic?
The sclera and the cornea.
126
What is the sclera and what is its purpose?
The sclera is the firm white outer layer of connective tissue which covers the entire eye except for the cornea. Its job is to maintain the shape of the eye, protect the inner components, and provide a point of attachment for the muscles that move the eye.
127
What is the cornea and what is its purpose?
The cornea is made of connective tissue and is the clear "window" of the eye through which light enters. It covers the part of the eye that the sclera does not. In addition, it acts as a part of the focusing system of the eye by automatically refracting light that enters the eye and bending it before it reaches the lens.
128
How is the connective tissue of the sclera different from that of the cornea?
The collagen fibers in the cornea are thinner and there is much less water in the tissue of the cornea than in the tissue of the sclera.
129
What two factors cause the cornea to be transparent?
It has thin collagen fibers and a low water content.
130
What is the conjunctiva and what is its purpose?
It is a thin, transparent epithelial membrane that covers the inner surface of the eyelids and the anterior portion of the sclera. It helps to protect and lubricate the eye.
131
Why are the whites of the eye around the iris shiny white?
The smooth, transparent conjunctiva overlies the white collagen of the sclera. In addition, this smoothness prevents infection because bacteria cannot easily cling to the surface.
132
What structures make up the vascular tunic?
The choroid, ciliary body, ciliary muscles, ciliary processes, the lens, suspensory ligaments, and the iris.
133
Why is the vascular tunic called the vascular tunic?
It contains most of the blood vessels in the eye, which supply the eye tissues with oxygen and nutrients.
134
The choroid
The layer of vascular tissue just beneath the sclera that appears black in color because it contains many cells that produce melanin.
135
What is the iris and what is its purpose?
The iris is made of smooth muscle that surrounds the pupil. It regulates how much light gets into the eye by varying the size of the pupil.
136
What structures make up the nervous tunic?
The retina, rods, cones, the optic disk, the optic nerve, the macula lutea, and the fovea centralis.
137
Why does the red-eye effect happen when taking pictures of a person?
The flash reflects off of the vessels of the blood in the retina, giving a vivid, red spot on the eye.
138
The optic disk
The spot on the retina that contains no photoreceptors (rods and cones), the point at which the blood vessels enter the eye, and the point at which the axons of the neurons in the retina exit the eye and join the optic nerve.
139
Which area of the retina gives the sharpest image?
The fovea centralis because the photoreceptor cells for detailed, colored vision are packed very tightly in this region.
140
Describe the composition of the pigmented retina.
It consists of one layer of epithelial cells full of melanin.
141
Describe what happens when light hits the pigmented retina.
The light is absorbed, which increases the sharpness of the image because light is not reflected back into the photoreceptors.
142
Nystagmus
The constant involuntary shifting of the eyes by the skeletal muscle usually used to turn the eyes on an object of interest.
143
What type of vision corresponds to rods?
Rods work under dim-light conditions, but they cannot distinguish the color of the light that hits them.
144
What type of vision corresponds to cones?
Cones are only active when there is enough light available. They enhance the sharpness of the image and can distinguish the wavelengths of the light that hits the retina.
145
Describe the synapses in the retina.
The rods and cones synapse with bipolar neurons which synapse with ganglion cells. The axons from the ganglion cells pass over the surface of the retina and converge on the optic disk and become a part of the optic nerve.
146
What is the purpose of the association neurons in the retina?
They serve to regulate some of the visual signals before they get to the brain.
147
Why is the fovea centralis the source of best vision on the retina?
The axons of the ganglion cells do not pass over the fovea centralis, and a large number of cones are concentrated there.
148
What is the vitreous humor and what is its purpose?
It is composed of a transparent, gel-like protein that is holding water. The protein attracts water to form a gel. The gel maintains the general shape of the eyeball by acting as a filler.
149
What are "floaters"?
Strings of protein in the vitreous humor that have come out of solution.
150
Where is aqueous humor found?
Both the anterior chamber and posterior chamber of the eye.
151
How does aqueous humor flow?
It is produced by the ciliary processes, flows through the two chambers (anterior and posterior) and ultimately drains back into the blood via a circular vein near the edge of the iris.
152
What is the purpose of the aqueous humor?
It is responsible for some of the automatic refraction that helps the eye focus light and helps maintain the exact pressure within the eye by gently pushing the cornea outward. In addition, it supplies the cornea with nutrition.
153
What happens if pressure within the eye drops too low?
The retina detaches from the choroid.
154
What happens if pressure in the eye is too high?
When pressure is too high, it gradually kills the neurons within the eye and causes progressive loss of vision called glaucoma.
155
What are the three main steps to the physiology of vision?
First, the light must be focused onto the retina where the photoreceptors can be stimulated by it. Second, the photoreceptors react to the stimulus. Third, the action potentials produced as a result of the stimulus are sent to the visual cortex where they are interpreted.
156
Where are cones most concentrated in the eye?
The fovea centralis.
157
The focal point
The point at which light rays converge in the eye. The focal point is anterior to the retina.
158
The far point of vision
The point at which the ciliary muscle is completely relaxed in the eye and further.
159
When an object moves closer than the far point of vision, what three reflexes must occur to bring the image to proper focus on the retina?
Accommodation of the lens, constriction of the pupil, and convergence of the eyes.
160
How is accommodation of the lens accomplished?
The ciliary muscles contract and cause the ciliary body to move closer to the eye. This reduces the tension on the suspensory ligaments, and the elastic lens rounds up, and because it is curved, it increases the amount that the light rays bend (it decreases the focal length of the lens). This moves the focal point farther from the retina, making a larger image.
161
Why does looking at something up close for a long period of time cause eyestrain?
When looking at something up close, the ciliary muscle must stay contracted to keep the lens rounded. That takes energy, and after a while, the muscle can get tired.
162
The near point of vision.
The point of vision at which the lens cannot accommodate/get rounder any more and the object becomes blurry.
163
Presbyopia
The state of the eye when the accommodation ability of the lens degenerates to the extent that the near point of vision is greater than 9 inches. It is Latin for "elder vision."
164
What is myopia, and what circumstances in the eye cause it?
Nearsightedness. With myopia, the combination of the lens and cornea bends light too strongly, or the eyeball is too long, adn the image is formed too far in front of the retina.
165
How can myopia be corrected?
A lens that bends light away from the center of the eye, called a diverging lens, corrects myopia by bending the light rays the opposite way that the eye does in order to make up for the fact that the eye bends the light too strongly or is too long.
166
What is hyperopia, and what circumstances in the eye cause it?
Farsightedness. This condition arises when the cornea and lens cannot bend light strongly enough or the eyeball is too short. Thus, the image is formed behind the retina.
167
How can hyperopia be corrected?
A lens that bends light toward the center of the eye can correct hyperopia. Call a converging lens, it helps the lens and cornea by bending the light in the direction it needs to bend before it hits the eye.
168
What does constriction of the pupil do for vision?
It ensures that the light rays coming from the object are traveling very straight by blocking out rays that are not coming straight in from the object to the eye. This increases the depth of focus, which is the range of distances over which the eye is focused.
169
What is the purpose of convergence, and what parts of the body perform it?
As an object moves closer, the eyes must be rotated to make up for the fact that the light rays are not parallel anymore. The skeletal muscles outside the eyeball do it.
170
Depth perception
The ability to judge distance, especially of close objects.
171
How do eyes detect color?
Cones are the photoreceptors for detailed color vision. There are three types of cones, each having a different protein complex sensitive to a different set of light wavelengths: cones sensitive to red light, blue light, and green light.
