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unit 14 week 2 > Sensorimotor systems > Flashcards

Sensorimotor systems Flashcards

1
Q

LOs

A
  • Demonstrate a systematic and coherent knowledge of the anatomical and physiological functioning of the sensory and motor systems
  • Appraise the implications of any alteration in the normal function of the sensorimotor system
  • Discuss and analyse structure- function relationships of the sensory motor pathways and CNS
  • Recognise the basic neurological processes inculked in sensation
  • Describe the mechanism of voluntary and involuntary movements, recognise the important centres involved
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2
Q

levels of sensation:

sensation

perceprtion

modality

A

Sensation- conscious or subconscious awareness of external and internal stimuli

Perception- conscious awareness and interpretation of sensations

Modality- the uniqueness of each sensation; what distinguishes one sensation from another sensation

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3
Q

each sensory neurone can carry how many modalities? (type of message)

A

1

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4
Q

examples of somatic and visceral senses

what are the special senses (5)

A

somatic- tactile, thermal, pain and proprioception

visceral- internal organs- pressure, stretch, chemicals, nausea, hunger and temperature

Special senses: Smell, taste, vision, hearing, and equilibrium

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5
Q

what 2 kinds of structure can detect stimuli?

what is selectivity?

A

specilised receptor cell

sensory neurone (e.g., olfactory sensory neurones)

selectivity- A particular kind of stimulus (a change in the environment) activates certain sensory receptors, while other sensory receptors respond weakly or not at all

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6
Q

for a sensation to arise there has to be 4 events typically happen

A
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7
Q

3 general kind of neurone

A

Sensory

Interneurone

Motor

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8
Q

3 ways of grouping sensory neurones

A
  1. microscopic structure- free nerve endings vs encapsulated endings for example a) Free- bare dendrites; lack structural specialisation, pain, temperature, tickle, itch, touch
    * b) Encapsulated*- enclosed in CT, pressure, touch, vibration
  2. Location… of receptors and the origin of the stimuli that activate them
    a) Exteroceptors near the external surface
    b) Internoceptors (visceroceptors)
  3. The Type of stimulus detected (nociceptors for pain, mechanoreceptors for pressure, etc.)
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9
Q

characteristics of sensory receptors (2)

A

1) selective-

  • Each sensory receptor responds strongly to one certain kind of stimulus
  • Some receptors respond weakly or not at all to other stimuli
  • Some are simple whereas others are complex (special senses)

2) Adaptable-

  • in which the generator potential or receptor potential decreases in amplitude during a sustained or constant stimulus
  • Because there is an accommodation response at the receptor level, the frequency of nerve impulses traveling to the cerebral cortex decreases and the perception of the sensation fades even though the stimulus persists
  • Receptors vary in how quickly they adapt
  • Rapidly adapting for signaling changes in a stimulus
  • Slowly adapting continue to trigger nerve impulses as long as the stimulus persists; pain body position, chemical composition of blood
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10
Q

receptors named according to their location:

exteroceptors

interoceptors

proprioceptors

A
  1. Exteroceptors- located near the surface of the body; detect changes in the external environment • (temp., touch, vision, smell, taste, pain, etc.)
  2. Interoceptors- visceroceptors = located in blood vessels & viscera; detect changes in the internal environment
  3. Proprioceptors- located in muscles, tendons, joints, & internal ear; detect changes in body position, muscle tension, etc.
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11
Q

Receptors named according to their mode of activation

  1. mechanoceptors
  2. thermoreceptors
  3. nociceptors
  4. photoreceptors
  5. chemoreceptors
  6. osmoreceptors
A
  1. mechanoceptors- detect stretching or mechanical pressure (touch, pressure, proprioceptors , vibration, hearing, equilibrium, BP)
  2. thermoreceptors- which detect changes in temperature
  3. nociceptors- which respond to painful stimuli (tissue damage)
  4. photoreceptors- which are activated by photons of light (detect light striking the retina of the eye)
  5. chemoreceptors- which detect chemicals in the mouth (taste), nose (smell) and body fluids
  6. osmoreceptors- which detect the osmotic pressure of body fluids
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12
Q

general somatic senses

where are they classically felt

A

collect info about cutaneous sensation

Somatic senses (“soma” means body) detect touch, pain pressure, temperature, and tension on the skin and in internal organs.

Receptors located in skin, subcutaneous connective tissue, mucus membranes, & both ends of the Gl tract.

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13
Q

cutaneous receptors are? they come in which 2 forms?

A

dendrites of sensory neurones

a) free nerve endings
b) may have a capsule (e.g., in epithelial tissue or CT)

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14
Q

touch sensations are due to which kind of receptor

what is:

  1. crude touch
  2. discriminative touch
A

stimulation of tactile receptors in upper levels of the skin (mechanoreceptors)

Crude touch- ability to perceive something has touched the skin

Discriminative touch- ability to recognize the exact pints on the body that is touched

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15
Q

receptors for touch (4)

A
  1. Meissner’s corpuscle
  2. hair root plexuses
  3. merkel discs
  4. ruffini corpuscles
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16
Q

Meissner’s corpuscles

A
  • Mass of dendrites surrounded by connective tissue
  • Located in the dermal papillae
  • Adapt rapidly (lose sensitivity to the stimulus)
  • Involved in discriminative touch
  • Location: fingertips, palms, soles, eyelids, tip of tongue
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17
Q

Hair root plexuses

A
  • Dendrites in networks around hair follicles
  • Movements of hair shaft stimulates these dendrites; these receptors detect movements along skin surface (crude touch)
  • Also, rapidly adapting receptors
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18
Q

Merkel discs

A

Type I Cutaneous Mechanoreceptors

  • Flattened dendrites near the stratum basale
  • Slowly adaptive (remain sensitive to stimulus longer)
  • Involved in discriminative touch
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19
Q

▪ Ruffini corpuscles

A

Type II Cutaneous Mechanoreceptors

  • Located deeper in the dermis; detect heavy and/or continuous touch
  • Slowly adaptive (remain sensitive to stimulus longer)
20
Q

what is pressure

how is it different to touch

what are its receptors like

A

stimulation of tactile receptors deeper in tissues

Pressure is longer-lasting than touch; also felt over a larger area

Receptors:

Type II cutaneous mechoreceptors

Pacinian corpuscles- lamellated corpuscles

1 dendrite, surrounded by many layers of CT (located in subcutaneous tissues)

Rapidly adapting (lose sensitivity to stimulus)

21
Q

thermal sensations

receptor

A

Receptor: free nerve endings

Some of these thermal receptors respond to heat

Others respond to cold

22
Q

pain sensations

A

Vital sensation- danger alert signal

nociceptors (pain receptors) free nerve endings

located in nearly every tissue of the body

tissue damage releases chemicals, which stimulate nociceptors

little or no adaptation (remain sensitive for very long time)

23
Q

types of pain

  1. Acute pain
  2. Chronic pain
  3. Superficial somatic pain
  4. Deep somatic pain
  5. Visceral pain
  6. Referred pain
  7. Phantom pain
A
  1. Acute pain- sharp, fast; felt in a very localised area (message carried my large diameter myelinated neurones
  2. Chronic pain- slow pain which gradually increases Aching and throbbing are examples
  3. Superficial somatic pain- due to stimulation of nociceptors in the skin
  4. Deep somatic pain- stimulation of nociceptors in muscles, tendons, joints etc
  5. Visceral pain- stimulation of nociceptors in visceral organs
  6. Referred pain- with visceral pain, usually feel the pain in skin/ peritoneum covering the organ (not the organ itself)

• Usually, the area which is served by the same segment of spinal cord is where the pain is felt (same spinal nerves)

example: heart attack (spinal nerves T1-T5) ® feel pain in skin over heart & left arm
7. Phantom pain- sensation of pain from amputated limb

  • Brain receives impulses from the remaining (proximal ends) sensor neurons
  • Itching, tingling, pressure
24
Q

Nociception- 2 types:

A

Fast pain- acute well localised, occurs rapidly because the nerve impulses propagate along medium-diameter, myelinated A fibres

Slow pain- begins after a stimulus is applied and gradually increases in intensity over a period of several seconds or minutes. Impulses for slow pain conduct along small-diameter, unmyelinated C fibers and this type of pain may be excruciating and often has a burning, aching, or throbbing quality

25
Q

relief of pain

anaesthesia

analgesia

A

Anaesthesia- blocks sensations of pain, touch, etc.; don’t allow the messages to reach the brain

General anesthesia = removes all sensations; also causes unconsciousness

Spinal anesthesia = removes all sensations below injection site (into subarachnoid space)

Analgesia- decrease or block sensations of pain

Can block production of prostaglandins, which stimulate nociceptors

Can block impulse conduction down neurones

Can change the perception of pain by the brain

26
Q

proprioceptive sensations receptors

A

Located in skeletal muscles (muscle spindles)

Tendons, in and around joints kinesthetic receptors and in the internal ear

These proprioceptors convey nerve impulses bout muscle tone, movement of body parts, & body position to the brain

27
Q

somatic senory pathways are made of how many neurones?

A

3

primary, secondary and third order neurones

28
Q

what is a first order neurone

A

conduct impulses from somatic receptors into the brain stem or spinal cord

  • Cranial nerves: into brain stem
  • Spinal nerves: into spinal cord
29
Q

Second order neurone

A

conducts impulses from the brain stem and spinal cord to the thalamus where the neurons decussate (cross to the opposite side)

• Thus, all somatic sensory information from one side of the body reaches the thalamus on the opposite side

30
Q

Posterior column tracts

A

Carry impulses for: proprioception, Discriminatory touch, Pressure, Vibrations

made up of 2 tracts:

  • Cuneate fasciculus- nerve impulses from upper limbs, upper trunk, neck and posterior head
  • Gracile fascicules - nerve impulses from lower trunk and lower limbs
31
Q

spinothalamic tract (lateral and anterior columns)

A

Carry impulses to cerebral cortex for:

  • Pain
  • Temperature
  • Itch & tickle

▪ From limbs, trunk, neck and posterior head

▪ To primary sensory motor cortex on the opposite side the site of stimulation

32
Q

trigeminothalamic tract

A

Carries nerve impulses for:

  • Touch
  • Pressure
  • Vibration
  • Pain
  • Temperature
  • Itch/Tickle

From: face, nasal cavity, oral cavity, and teeth

To primary sensory motor cortex on the opposite side of the site of stimulation

33
Q

spinocerebellar tract (anterior and posterior)

A

nerve impulses for: proprioception

from trunk and lower limbs

from one side of the body to the same side of cerebellum

allows for co-ordination, posture and balance

34
Q

somatic sensory distribution

A

not distributed evenly in the body

relative sizes of these regions are proportional to the number of specialised sensory receptors in the corresponding body part- making a sensory homunculus (cerebral cortex)

35
Q

where does motor activity begin?

A

in the primary motor areas of the precentral gyrus + other cerebral integrative centres

36
Q

what is the name of the motor neurone that is not directly responsible for stimulating target muscles?

what do they do?

A

upper motor neurone

UMNs connect the brain to the appropriate level in the spinal cord

37
Q

what is the purpose of second order/ lower MNs?

A

All excitatory and inhibitory signals that control movement converge on second-order motor neurons known as lower motor neurons (LMNs) that descend to innervate skeletal muscle

• Since only LMNs provides output from the CNS to skeletal muscle fibers they are also called the final common pathway

38
Q

direct/ pyramidal tracts

A

part of the UMN system and are a system of efferent nerve fibers that carry signals for precise, volunatry movements from the cerebral cortex to either the brainstem or the spinal cord. It divides into two tracts: the corticospinal tract and the corticobulbar tract

39
Q

lateral and anterior corticospinal tracts

A

Lateral corticospinal tracts - responsible for precise, agile, and higher skilled movements of the

hands and feet

Anterior corticospinal tracts - control movements of the trunk and proximal parts of the limbs

The neurons that travel in the corticospinal tract are referred to as upper motor neurons; they synapse on neurons in the spinal cord called lower motor neurons, which make contact with skeletal muscle to cause muscle contraction.

40
Q

Corticobulbar pathway

A

Impulses for the control of skeletal muscles in the head

Associated with cranial nerves

41
Q

Indirect and extra/pyramidal tracts (lateral and anterior columns)

A
  • Originate in the midbrain (unconscious)
  • Nerve impulses for involuntary movements, muscle tone, posture and balance
  • Five major tracts
42
Q

what are the 5 indirect/ extra pyramidal tracts?

A

Rubrospinal- precise, voluntary movement of distal parts of upper limbs

• Tectospinal- reflexively move head, eyes, and trunk in response to visual and auditory stimulus

• Vestibulospinal- maintaining posture and balancr in response to head movements

• Lateral & Medial reticulospinal- maintaining posture and regulating muscle tone in response

to ongoing body movements

43
Q

Sleep and wakefullness are functions of what part of the brain?

what are they controlled by?

A

integrative functions of the cerebrum

Controlled by the “reticular activating system” (RAS)

44
Q

what is the reticular formation

how does the RAS system work?

A

patches of gray matter scattered in the white matter of brainstem, spinal cord, and diencephalon

A portion of the Reticular Formation is the RAS

  • RAS acts as an alerting system to “wake up” the cerebral cortex
  • When the RAS is stimulated by nociceptors, touch, proprioceptors signals, bright light, or

sound, it sends impulses through the thalamus, where the message gets dispersed to many areas of the cerebral cortex

• The RAS is responsible for arousal from deep sleep, and for maintaining a general state of wakefulness/consciousness

during sleep the activity of the RAS is very low

45
Q

what is sleep?

2 kinds of sleep

A

state of altered consciousness or partial unconsciousness, from which the person can be aroused

  • Neurotransmitters which cause sleep: Serotonin & Norepinephrine
  • Each is produced by specific nuclei in the brain stem

Two types of normal sleep:

  • Non-rapid eye movement sleep (NREM): slow wave sleep (4 stages)
  • REM sleep: most dreaming occurs; very high 02 consumption by the brain during REM
46
Q

definitions of

  • learning
  • memory
  • plasticity
  • short term memory
  • long term memory
  • amnesia
A

Learning- ability to acquire new information or skills through instruction or experience

Memory- process by which information acquired through learning is stored and retrieved

Plasticity- capability for change associated with learning (structural and functional changes in the brain)

short term memory- lasts longer than immediate but still short lived

long term memory

amnesia anterograde (new) and retrograde (past)

unit 14 week 2 (7 decks)

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