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Human Physiology 1 > PNS: Afferent Division > Flashcards

PNS: Afferent Division Flashcards

1
Q

spinothalamic tract

A

this pathway conveys sensory information about the thermoreceptors and nociceptors to the CNS. This pathway decussate at the level of the spinal cord at the anterior white commissure on its way to the thalamus

Temperature and painful stimuli from the skin is relayed to first degree neurons which synapse at the spinal cord. From there, second degree neurons carries the sensory information to the thalamus. From the thalamus, 3rd degree neurons carries the information to the primary somatosensory cortex in the parietal lobe.

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2
Q

Describe the dorsal column-medial lemniscal pathway

A

Is a sensory pathway of the CNS that transmits information from proprioceptors and mechanoreceptors to the CNS (somatosensory cortex)

From the dorsal column of the spinal cord, sensory information carried by second degree neuron sent to the medulla, where it crosses over to the contralateral side at the medial lemniscus as it head toward the thalamus

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3
Q

Identify the auditory ossicles and describe their function.

A

The ossicles are three tiny bones in the middle ear between the eardrum and cochlea known as malleus, incus and staples

Their role is to transmit sound from the air to the fluid filled cochlea.

The lever actions of these small bones amplifies sound so that the oval window of the cochlea vibrates the fluid within the cochlea

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4
Q

Identify and describe the role of the oval window in the ear

A

The oval window is a connective tissue membranous opening that transmit sound waves from the middle to inner ear. It forms the intersection between the inner and outer ear and is sandwiched between the stapes and vestibule of the ear.

The oval window vibrates the fluid within the cochlear

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5
Q

What are the structures of the inner ear?

A

Cochlea and vestibular appartus.

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6
Q

Pitch is a fundamental characteristic of sound waves.

Describe pitch and how is it determined? (measured)

A

Pitch is the quality of sound and is determined by the frequency or rate of sound waves and is measured in cycles per second or hertz (Hz)

The pitch of the sound waves helps us distinguish between low note and high note.

A low note has a low frequency and high note has a high frequency given the same loudness.

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7
Q

How do we measure pitch?

A

Hertz

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8
Q

How do we measure how loud a sound is?

A

decibels

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9
Q

Outer layer of connective tissue that forms the white parts of the eye

A

Sclera

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10
Q

Inner pigmented layer that contains the photoreceptors rods & cones that convert light energy into nerve impulse

A

Retina

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11
Q

Describe how pupillary dilation and pupillary constriction occurs?

(muscle, nervous system)

How do pupils dilate and constrict?

A

Bright lights stimulate the photoreceptors in the retina of the eye, The sympathetic nervous system stimulates the circular muscle of the eye, causing constriction of the pupil.

To let in more light, parasympathetic nervous system stimulates the radial musle of the iris to contract, causing pupils to dilate

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12
Q

What is referred pain?

Why is visceral pain felt on the surface of the body away from its original source?

A

Referred pain is the result of afferent neurons originating the skin and viscera that share the same second-order neuron.

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13
Q

What are 1st, 2nd, and 3rd degree neurons?

A

The first-order neurons carry signals from the periphery to the spinal cord; thesecond-order neurons carry signals from the spinal cord to the thalamus; and the third-order neurons carry signals from the thalamus to the primary sensory cortex.Second-order neurons are generally located in the spinal cord or the brainstem

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14
Q

Discuss the basics of gate control theory of pain. The reason why ice, heat, and accupuncture works in pain management

A

When pain is modulated (ice is applied to skin), skin mechanoreceptors excites the inhibitory interneuron at the spinal cord, which results in a weaker signal of pain.

Nociceptors transmit pain signals from the skin to the brain. But pain transmission can be modulated by the signals of inhibitory interneurons that are excited by signals from the mechanoreceptors

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15
Q

How does the eye accommodate for near vision?

A

The eye can accommodate for near vision due to PNS input to contract the ciliary muscle, and relaxes zonule fibres, and causing a rounded lens

This occurs because the lens is flexible and elastic, it can change its curved shape to focus on objects and people that are nearby or at a distance.

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16
Q

Rhodopsin

A

is a photopigment is in the retina of the eye that absorbs light. Light energy activates Rhodopsin which is located in the disc membranes of the rod outer segments.

This pigment is the pigment which enables to see dim light.

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17
Q

True/False

Parasympathetic stimulation causes contraction of the ciliary muscle to increase the curvature of the Lens to focus light on the retina.

A

True

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18
Q

What happens to the lens when the ciliary muscle contracts?

A

When the ciliary muscle is relaxed, the choroid acts like a spring pulling on the lens via the zonule fibers causing the lens to become flat. When the ciliary muscle contracts, it stretches the choroid, releasing the tension on the lens and the lens becomes rounded.

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19
Q

What is the choroid layer of the eye and function? Why is the choroid dark brown/black?

A

It is a thin, highly vascular membrane that is dark brown in colour due to melanin pigment which helps to absorbs excess light and so prevents blurred vision (due to too much light on the retina). The choroid also bring oxygen and nutrients to the retina.

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20
Q

What is the difference between vitreous humor and aqueous humor?

A

Aqueous humor is a clear liquid found between the cornea and the lens of eye, whereas vitreous humor is a clear gelatinous mass found in the rear part of the eyeball between the lens and retina.

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21
Q

How can excess aqueous humour without proper drainage cause glaucoma and thus lead to blindness?

A

Excess of aqueous humour in the anterior cavity of the eye can cause pressure to rise within the eye, thus give rise to a condition known as glaucoma. Intraocular pressure pushes on the lens back into the vitreous humour in which pushes against the inner neural layer of the retina. This compression causes retinal and optic nerve damage that can lead to blindness

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22
Q

True or False

A

The iris of each individual is so uniquely pattern that it is even more foolproof than fingerprinting or DNA testing for identifying an individual.

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23
Q

Describe the iris of the eye and its function

A

Controls the diameter and size of the pupil and thus the amount of light reaching the retina. The pigment in the iris give rise to eye color.

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24
Q

The muscles that constrict the pupils run circularly in a ring-like fashion. Which part of the autonomic nervous system activation is responsible for pupilliary constriction.

A

Parasympathetic Nervous system

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25
Q

Radial muscle of the iris runs radially and is responsible for pupillary dilation.

Fibers are supplied by the ______ nervous system

A

Sympathetic

26
Q

Photon

A

A photon is the smallest discrete amount or quantum of electromagnetic radiation. It is the basic unit of all light.

27
Q

Emmetropia is normal vision. In emmetropia, distant objects are focused on the retina _______ (with, without) accommodation. And near objects are focused on the retina ______ (with/without) accommodation.

A

without/with

28
Q

Bipolar cells

A

As a part of the retina, bipolar cells exist between photoreceptors and ganglion cells. They receive presynaptic input from the photoreceptors and transmit them to the ganglion cells.

29
Q

What is the function of the fovea in the human eye?

A

It is located in the center of the macula lutea of the retina. The fovea is responsible for sharp central vision (also called foveal vision), which is necessary in humans for activities where visual detail is of primary importance, such as reading and driving.

(only cones are found here)

30
Q

Macular degeneration

A

Macular degeneration is the leading cause of severe, irreversible vision loss in people over age 60. It occurs when the small central portion of the retina, known as themacula, deteriorates. The retina is the light-sensing nerve tissue at the back of the eye.

31
Q

rhodopsin

A

rod photopigment, absorbs all visible wavelength of light

32
Q

True or False

Receptors are specialized peripheral nerve endings or cells that detect a specific sensory stimulus.

A

True

33
Q

Starting at about age 40, our eyes naturally begin to lose the ability to focus on close objects. This is called

A

presbyopia.

34
Q

Perception vs sensation ?

A

Sensation refers to the process of sensing our environment through touch, taste, sight, sound, and smell. This information is sent to our brains in raw form where perception comes into play. Perception is the way we interpret these sensations and therefore make sense of everything around us.

35
Q

Define transduction

A

the conversion of stimulus energy (modality eg, photons of light) into electrical energy by the receptor (eg, photoreceptors)

36
Q

How is the receptor potential produced in a sensory neuron that is not attached to the receptor cell compared to a sensory neuron that is attached to the receptor cell.

A

In sensory receptors that are separate from the afferent neuron, a stimulus will open or close ion channels to produce a change in the membrane potential and ultimately open voltage-gated Ca2+ channels. The influx of Ca2+ triggers exocytosis of a chemical messenger. The chemical messenger binds to receptors on the afferent neuron to produce a receptor potential.

In sensory receptors that are specialized endings of afferent neurons, a stimulus will open or close ion channels to produce a receptor potential. If the receptor potentials evoked by the stimulus depolarizes the membrane to threshold, then a an action potential will be generated.

37
Q

What is sensory adaption?

Which type of receptors adapt rapidly?

Which type adapt slowly if at all?

A

Some receptor cells have a tendency to adapt or adjust to continual stimulation. When that happens, the receptors decrease the amplitude of the receptor potential, along with a corresponding decrease in frequency of action potentials over time.

As a result, we experience a decreased in perception of the stimulus.

Phasic receptors (smell, touch) adapt quickly)

Tonic receptors (proprioceptors, muscle stretch receptors, nociceptors adapt slowly

38
Q

What is the main function of the olfactory bulb?

A

The olfactory bulb receives neural input about odours detected by cells in the nasal cavity.

The axons of the olfactory receptors extend directly into the olfactory bulb where in formation about odour is processed

39
Q

What is the the glomerulus structure within the olfactory bulb of the brain?

A

This structure located within the olfactory bulb of the brain is where synapses are formed between the terminals (axons of the olfactory neurons) of the olfactory nerve and the dendrites of mitral cell

40
Q

What and Where is the primary olfactory cortex?

A

Is the part of the cerebrum that is involved in olfaction (detection of chemical odour). It Is located on the medial aspect of the temporal lobe.

41
Q

What are mitral cells ?

A

They are second-order neurons of the olfactory system. They are located in their forebrain right above the nasal cavity. They receive information from the axons of olfactory receptor neurons forming synapses in the glomeruli of the olfactory bulb. These neurons synapse in the limbic system or the primary olfactory cortex

42
Q

Which are the three types of cells that forms the olfactory epithelium that lines the nasal cavity?

A

Receptor cells, supporting cells (secretes mucus), and basal cells.

43
Q

Lateral inhibition

A

Lateral inhibition is the capacity of an excited neuron to reduce the activity of its neighbors. Lateral inhibition disables the spreading of action potentials from excited neurons to neighboring neurons in the lateral direction.

44
Q

Two Point Discrimination

Clinical significance?

A

is the ability to discern that two nearby objects touching the skin are truly two distinct points, not one. It is often tested with two sharp points during a neurological examination and is assumed to reflect how finely innervated an area of skin is.

45
Q

how do receptors code for stimulus location?

A

is determined by the size and degree of overlap of the receptive field.

If receptor ends are connected to two or more receptive field on the skin surface, multiple points can be determined.

46
Q

What type of lens is used to correct hyperopia

A

Convex lens

47
Q

Differentiate between the fovea and macula lutea

A

The fovea centralis is a small, central pit composed of closely packed cones in theeye. It is located in the center of the macula lutea of the retina

48
Q

Saccule vs utricle

A

The saccule is a bed of sensory cells situated in the inner ear. The saccule translates head movements into neural impulses which the brain can interpret. The saccule detects linear accelerations and head tilts in the vertical plane. When the head moves vertically, the sensory cells of the saccule are disturbed and the neurons connected to them begin transmitting impulses to the brain. These impulses travel along the vestibular portion of the eighth cranial nerve to the vestibular nuclei in the brainstem.

The utricle detects linear accelerations and head-tilts in the horizontal plane.

49
Q

True or False

By 3 months of age, the newborn is able to discriminate between the voice of the mother and another female

A

False, by 3 days

50
Q

What distance can the newborn see most clear at

A

objects must be 20-50 cm away from the newborn to see clearly

51
Q

At what age does the newborn acquire full depth perception?

A

by 9 months

52
Q

When can the newborn tell its his mother’s face or another female?

A

at 1 month of age

53
Q
A
54
Q

Macula lutea

What and where is it in the eye? What type of photoreceptors is in high concentration there.

A
  • It is a yellow oval spot at the center of the retina (back of the eye)
  • It is the part of the retina that is responsible for sharp, detailed central vision (also called visual acuity).
  • The macula lutea, also called fovea, contains a very high concentration of cones
55
Q

Phototransduction, further retinal processing, and iintiation of action potentials in the visual pathway. Events occurs in the retina and visual pathway in response to the light:

In the presence of light energy:

  • Activates photopigment activates G protein transducin
  • which activates enzymes that degrades cGMP
  • the reduction in cGMP protein causes Na+ channels in outer segment to close
  • Hyperpolarization of photoreceptor (instead of depolarization in phototransduction)
  • Hyperpolarization of rods/cones creates an receptor potential which spreads to the synaptic terminal of the photoreceptors.
  • At the synaptic terminal: causing Ca+ channels to close; thus decrease release of inhibitory transmitters, bi-polar cells becomes more excited as inhibition is removed
  • The removal of inhibition excites bipolar cells
  • Graded potentials in bipolar cells
  • If threshold potential is reached in the ganglion cells, than depolarization occur causing action potentials along the optic nerve to the visual cortex.
A

Events occurs in the retina and visual pathway in response to the dark:

In the dark,

Photoreceptors signal their absorption of photons _via a decrease in the release of the neurotransmitter glutamate to bipolar cell_s at its axon terminal. Since the photoreceptor is depolarized in the dark, a high amount of glutamate is being released to bipolar cells in the dark.

As a result of depolorization of photoreceptors, there is an increase in inhibitor neurotransmitter released into the synaspe; thus inhibiting bipolar cells, causing no communication of bipolar cells to ganglion cells.

56
Q

Differences between rods and cones?

A

Rods vs cones

  • 100 million per retina vs 3 million
  • Vision in shades of grey vs vision in colours
  • high sensitivity vs low sensitivity
  • low acuity vs high acuity
  • night vision vs day vision
  • much convergence in retinal pathways vs little
  • more numerous in periphery vs concentrated in fovea and macula lutea
57
Q

What the second-order neurons in the olfactory pathway called?

A

mitral cells, they form the olfactory tract.

Mitral cells synapse in the limbic system or the primary olfactory cortex (lower medial side of the temporal lobe)

58
Q

Match

  1. Secrete mucous
  2. Precursers for new receptor cells
  3. synaptic site of 1st order neuron
  4. 2nd order neuron
    a. basal cells
    b. support cells
    c. glomeruli
    d. mitral cells
A
  1. b
  2. a
  3. c
  4. d
59
Q
A
60
Q

Approx how many receptor cells do taste buds have?

A

50-150 taste receptor cells

61
Q

Gustation: Match

  1. synaptic site of 2nd order neurons
  2. synaptic site of 1st order neurons
  3. synaptic sites of 3rd order neurons

a brainstem

b. thalamus
c. somatosensory cortex

A
62
Q

Vestibular: matcj

A

Human Physiology 1 (18 decks)

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