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BIO 181-171 > CH 15: PNS 10-18-13 (BIO 181) > Flashcards

CH 15: PNS 10-18-13 (BIO 181) Flashcards

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Biology 101 flashcards
1
Q

provides information from the CNS to specific targets in the body
• Made of motor neurons that connect CNS to various organs, muscles, and glands throughout the body

A

efferent branch

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2
Q

branch of the PNS provides information from periphery to CNS

• Made of sensory neurons that originate at sensory receptors and terminate in the CNS

A

afferent branch

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3
Q
  • Sensation (The arrival of information from these senses)
  • Perception (Conscious awareness of a sensation)
  • Interpretation of sensory information
  • Processing and Adaptation
  • Transduction
A

functions of sensory receptors in the PNS

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4
Q

• Specialized nerve endings or cells that detect a sensory stimulus
• Connect our internal and external environments with our nervous system
• Located in sense organs all over the body (such as the skin, eyes, ears, etc.)
-can detect many energy forms or modalities:
• Physical force (such as pressure)
• Dissolved chemical
• Sound energy
• Light energy

A

sensory receptors

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5
Q

doesn’t understand chemicals, mechanical or light waves. It understands electrical impulses

A

brain

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6
Q

• In order to perceive all the different forms of energy in the world, that energy must undergo _____

  • The process by which the stimulus energy is converted into electrical energy
  • Sensory Receptors function in the Transduction of different forms of energy
  • Example - When you taste something, that chemical energy must be converted into electrical energy in order for you to perceive different tastes
A

transduction

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7
Q

• Your nervous system quickly adapts to stimuli that are painless and constant

  • Reduction in sensitivity to a constant stimulus
  • Results in a corresponding decrease in the perception of a stimulus
A

adaptation

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8
Q
  • Receptors are active for the duration of the stimulus

* Remind you of an injury long after the initial damage has occurred

A

• Slow-adapting receptors (tonic receptors)

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9
Q
  • Are normally inactive
  • Receptors are only active at the onset and offset of the stimulus
  • Become active for a short time whenever a change occurs
  • Provide information about the intensity of a stimulus
A

• Rapidly Adapting receptors (phasic receptors)

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10
Q

• In order to correctly perceive a stimulus, the brain must be able to decipher it… this is called ____ _____.

  • To do this, the brain takes into account:
  • Stimulus type
  • Stimulus intensity
  • Stimulus location
A

Sensory Coding

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11
Q
  • Involves knowing which receptor type is activated
  • Each receptor type involves a specific pathway
  • Your perception of the nature of that stimulus depends on the path it takes inside the CNS
A

• Coding for Stimulus Type

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12
Q
  • Stimulation of a receptor produces action potentials along the axon of a sensory neuron
  • There are TWO ways to code for the intensity or strength of a stimulus!
  • Coding for Stimulus Intensity involves FREQUENCY CODING
  • Simply, the frequency of action potentials
  • Stronger stimulus = higher frequency of action potentials (more action potentials)
  • Coding for Stimulus Intensity also involves RECRUITMENT (Population coding)
  • Stronger stimulus = more receptors are activated
A

• Coding for Stimulus Strength (or intensity)

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13
Q

• Coding for location of a stimulus involves the sensitivity of the receptor
• Each receptor responds to specific types of stimuli
• Coding for location also involves the size of the receptors receptive field
(Area of the body that is monitored or innervated by a single receptor cell)
• Based on the nature of the specific receptive fields you are able to feel AND localize various stimuli

A

• Coding for Stimulus Location

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14
Q
  • The larger the receptive field, the more difficult it is to localize a stimulus
  • Neurons with small receptive fields = very high acuity (fingertips)
  • Large receptive fields = less acuity (back, calves, etc.)
  • Degree of overlap
  • More overlap = better localization of stimulus
A

• Size of receptive field

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15
Q
  • Ability to perceive two points on skin

* Depends on receptive field overlap and size

A

• A good way to measure acuity is with two point tactile discrimination:

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16
Q
  • Different body regions have different thresholds and therefore, differences in acuity
  • Lips highest level of acuity and calf is lowest level of acuity
A

acuity

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17
Q

• Your ____ ____ allow you to perceive various stimuli, and ultimately the world you

A

sense organs

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18
Q

• There are two types of sense organs

A
  • General Senses

* Special Senses

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19
Q
  • Provides somesthetic sensations (involves the skin) – and this includes:
  • Touch
  • Pressure
  • Vibration
  • Temperature
  • Pain
  • Propioception (position of limbs and body)
A

• General Senses (primarily the somatosensory system)

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20
Q

• All general receptors are ______ receptors
• divided into four types based on the nature of the stimulus that excites them
» Nociceptors (pain)
• Thermoreceptors (temperature)
• Chemoreceptors (chemical concentration)
• Mechanoreceptors (physical distortion)

A

SOMATOSENSORY

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21
Q
  • Also called pain receptors because stimulation results in pain
  • Sensitive to temperature extremes, mechanical stress or damage, and dissolved chemicals can all cause pain by stimulating different classes of receptors
  • Are common in the superficial portions of the skin, joints, bones, and around the walls of blood vessels
  • Composed of free nerve endings with large receptive fields
  • Can be stimulated by many different stimuli
A

• Nociceptors

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22
Q
  • Carry sensations of fast pain, or prickling pain, such as that caused by an injection or a deep cut
  • Sensations reach the CNS (primary sensory cortex) quickly and often trigger somatic reflexes
A

• Myelinated Type A fibers (NOCICEPTORS)

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23
Q
  • Carry sensations of slow pain, burning, or aching pain
  • Provide indistinct source information
  • You become aware of the pain but only have a general idea of the area affected
A

• Type C fibers Unmyelinated (NOCICEPTORS)

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24
Q

• Also called temperature receptors because they detect heat or absence thereof
• Are also free nerve endings located in
– The dermis
– Skeletal muscles
– The liver
– The hypothalamus
• Thermoreceptors are typically rapidly adapting (phasic)
• Temperature sensations are conducted along the same pathways that carry pain sensations

A

• Thermoreceptors

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25
Q

• Respond to specific chemicals that are,
• In solution (taste)
• Volatilized (smell)
• Dissolved in blood (internal chemorecptors)
• Monitor the composition of arterial blood
» pH levels
» carbon dioxide or oxygen levels
» osmolarity

A

• Chemoreceptors

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26
Q
  • Sensitive to stimuli that distort their plasma membranes (anything moving or any physical perturbation)
  • Contain mechanically gated ion channels whose gates open or close in response to
  • Stretching
  • Compression
  • Other mechanical distortions of the membrane
A

• Mechanoreceptors

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27
Q
  • Baroreceptors
  • Proprioceptors
  • Tactile receptors (Six subtypes)
A

• Three classes of Mechanoreceptors

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28
Q
  • Detect and monitor pressure changes in the walls of blood vessels and in portions of the digestive, reproductive, and urinary tracts
  • Consist of free nerve endings that branch into vessel walls
  • Are rapidly adapting receptors
  • Respond immediately to a change in pressure, but adapt rapidly as well
A

• Baroreceptors

29
Q
  • Monitor Position of joints, tension in tendons and ligaments and state of muscular contraction
  • The most structurally and functionally complex of all the general sensory receptors
  • Three major groups of Proprioceptors: Muscle spindles, Golgi tendon organs, and Receptors in joint capsules
A

• Proprioceptors

30
Q
  • Provide the sensations of touch, pressure, and vibration
  • Tactile receptors can detect fine and crude sensations
  • Fine touch and pressure receptors
  • Are extremely sensitive
  • Have relatively small receptive fields
  • Provide detailed information about the source of stimulation, including its exact location, shape, size, texture, movement
  • Crude touch and pressure receptors
  • Have relatively large receptive fields
  • Provide poor localization
  • Give little information about the stimulus
A

• Tactile receptors

31
Q
  • Detect pain
  • Located between epidermal cells
  • Are tonic receptors with small receptive fields
  • Slow adapting
A

• Free nerve endings

32
Q
  • Detect FINE touch and slight pressure
  • Extremely sensitive tonic receptors
  • Have very small receptive fields
  • Slowly adapting
A

• Tactile discs or Merkel discs

33
Q
  • Detect CRUDE pressure and distortion of the skin
  • Located deep in the dermis
  • Slowly adapting
A

• Ruffini corpuscles

34
Q
  • Detect hair movement
  • Monitor distortions and movements across body surfaces that contain hairs
  • Rapidly adapting
A

• Root hair plexus

35
Q
  • Perceive sensations of FINE touch, pressure, and low-frequency vibration
  • Fairly large structures
  • Most abundant in the eyelids, lips, fingertips, etc.
  • Rapidly adapting
A

• Tactile corpuscles or Meissner corpuscles

36
Q
  • detect DEEP pressure
  • Most sensitive to pulsing or high-frequency vibrating stimuli
  • Rapidly adapting
A

Lamellated corpuscles) Pacinian corpuscles

37
Q
  • Sensory information travels from the sensory receptors to the cortex through a series of synapses:
  • First-Order Neuron: Cell body originates in dorsal root ganglion or cranial nerve ganglion
  • Second-Order Neuron: located in the spinal cord or brain stem
  • Third-Order Neuron: If the sensation is to reach our awareness, the second-order neuron synapses on a third-order neuron in the thalamus and the Third-order neuron ultimately projects onto the cortex
  • Separate pathways for sensory and motor information: Ascending Sensory Pathways and Desceding Motor Pathways
A

sensory pathways

38
Q
  • Carries sensations of highly localized (“fine”) touch, pressure, vibration, and proprioception
  • Information crosses at the brain stem
A

Ascending Sensory Pathways

• Posterior column pathway

39
Q
  • Provides conscious sensations of poorly localized (“crude”) touch, pressure, pain, and temperature
  • Information crosses immediately at the spinal cord
A

Ascending Sensory Pathways

• Spinothalamic Pathway

40
Q
  • Carries proprioceptive information about position of skeletal muscles, tendons, and joints
  • Terminates at the cerebellum (only one not to terminate in the cortex)
A

Ascending Sensory Pathways

• The Spinocerebellar Pathway

41
Q
  • Carry information from the brain to various muscles, and glands
  • TWO major descending motor pathways from brain to muscles
A

Descending Motor Pathways

42
Q
  • The anterior corticospinal pathway
  • The lateral corticospinal pathway
  • Corticobulbar pathway
  • Lateral tracts and corticobulbar tracts cross over to contralateral side in the brainstem
  • Anterior tracts cross over at the spinal cord
  • For control of VOLUNTARY (conscious) movement of skeletal muscles of the distal extremities
  • Originate in primary motor cortex and Project Direct input to motor neurons in the spinal cord
A

• Pyramidal System

43
Q
  • The medial pathway
  • Vestibulospinal
  • Tectospinal
  • Reticulospinal
  • The lateral pathway
  • Rubrospinal
  • For INVOLUNTARY, automatic (subconscious) control of skeletal muscles of the proximal extremities and large muscle groups (ex. for posture and balance)
  • Indirect input to motor neurons in the spinal cord
  • Include several pathways
  • The location of cross over to the contralateral side varies for each pathway
A

• Extrapyramidal System

44
Q
  • Hollow structure divided into two fluid filled cavities:
  • Large posterior cavity contains vitreous body
  • Smaller anterior cavity contains the aqueous humor and is subdivided into: anterior chamber and posterior chamber
  • The Fibrous Tunic
  • Sclera (white of eye)
A

Special Senses - The Eye

45
Q
  • Outermost Fibrous tunic Sclera and cornea
  • Middle Vascular tunic Choroid, ciliary body, and iris
  • Inner Neural tunic Retina
A

three layers

46
Q
  • Cornea (Allows light to enter the eye)
  • Vascular Tunic (Uvea)
  • Iris
  • Choroid
  • Ciliary body
  • Lens: Lies posterior to the cornea and functions in focusing images appropriately onto retina
A

special senses: the eye

47
Q
  • Light energy is in the form of light waves

* And all light waves exhibit reflection and refraction

A

The Nature and Behavior of Light Waves

48
Q

light bouncing off of surfaces (and the reflections are what we perceive)

A

refelction

49
Q

bending of light (by cornea and lens) as it passes through transparent surfaces or from one medium to another

A

• Refraction

50
Q

• The curvature of the lens can change as needed

A

accomodation

51
Q
  • To focus on near objects, lens increases curvature, lens becomes more curved, and refractive index increases
  • To focus on distant objects lens decreases its curvature, lens becomes more flattened and refractive index decreases
A

focus

52
Q
  • Distant objects need little or no accommodation
  • Accommodation only occurs with close objects
  • Accommodation occurs via Parasympathetic Nervous System
A

Normal Eye (Emmetropia)

53
Q
  • Most problems with vision occur when light waves are not adequately focused onto the retina
  • This can be due to a defect in the lens, cornea, or eyeball length
A

Clinical Abnoramalities

54
Q
  • Lens is too strong and converges light too much and image is focused in front of the retina
  • Corrected with concave lens so that light is more diverged
A

Myopia (Near Sightedness)

55
Q
  • Lens is weak and does not converge light enough and image is focused behind the retina
  • Corrected with convex lens so that light is more converged
A

Hyperopia (Far Sightedness)

56
Q
  • Size of pupil regulates the amount of light entering eye
  • Iris consists of two layers of smooth muscle
  • Inner circular muscle—constrictor
  • Outer radial muscle—dilator
  • Hole in center—pupil
A

Regulation of Light Entering the Eye

57
Q
  • Innervate Inner circular muscles constrict

* Causes pupillary constriction and causes Less light entering the eye

A

• Parasympathetic NS (light)

58
Q

Radial muscles constrict
• Causes pupillary dialation
• More light entering the eye

A

Sympathetic NS (darkness)

59
Q
  • Outer part called the pigmented epithelium
  • Inner neural part that contains sensory receptors and associated neurons
  • Photoreceptors(outer layer) act as the sensory receptor cells and consist of Rods and cones
  • Rods and cones communicate with bipolar cells (middle layer)
  • Bipolar cells communicate with ganglion cells (innermost layer)
  • Axons of ganglion cells form the optic nerve
A

retina

60
Q
  • Central point on the retina of the eye that’s Packed with cones (NO RODS)
  • Region of the retina with highest visual acuity
A

fovea

61
Q

Circular region just medial to fovea where the optic nerve originates (with no rods or cones)
– blind spot

A

optic disc

62
Q
  • The ability to convert light energy to nerve signals lies primarily in the photoreceptors
A

phototransduction

63
Q
  • for form vision and black and white vision

* located throughout

A

rods

64
Q
  • for color vision

* densely located in the fovea

A

cones

65
Q
  • But in order to get to the Rods and Cones, light must first go through several layers of ___ ____
A

cellular material

66
Q

photoreceptor depolarization leads to an INCREASE in neurotransmitter release (graded potentail)

A

• Dark (depolarization)

67
Q

photoreceptor hyperpolarization leads to an DECREASE in neurotransmitter release (graded potential)

A

• Light (hyperpolarization)

68
Q
  • When light hits a photoreceptor cell, the photoreceptor hyperpolarizes, and releases less glutamate.
  • An ON bipolar cell will react to this change by depolarizing. (graded potential)
  • An OFF bipolar cell will react to this decrease in glutamate by hyperpolarizing. (graded potential)
  • In the absence of light, a photoreceptor cell depolarizes and releases more glutamate which ultimately inhibits the ON bipolar cells and activate the OFF bipolar cells.
  • In the presence of light, photoreceptors are inhibited, and no glutamate is released. So ON bipolar loses its inhibition and becomes active, while the OFF bipolar cell loses its excitation and becomes silent
A

Light

69
Q
  • Visual information then goes from the rods and cones to the bipolar cells to the ganglion cells
  • Ganglion cells are the first cells in the pathway to generate action potentials
  • Axons of ganglion cells = cranial nerve II
  • Optic nerve then projects the information to the Thalamus (specifically the Lateral Geniculate Neclus)
  • These projections finally terminate in the Primary Visual Cortex
A

Neural Processing in the Retina

BIO 181-171 (12 decks)

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