Sensorimotor systems

Question 1

LOs

Answer 1

• 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

Question 2

levels of sensation:

sensation

perceprtion

modality

Answer 2

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

Question 3

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

Answer 3

1

Question 4

examples of somatic and visceral senses

what are the special senses (5)

Answer 4

somatic- tactile, thermal, pain and proprioception

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

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

Question 5

what 2 kinds of structure can detect stimuli?

what is selectivity?

Answer 5

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

Question 6

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

Question 7

3 general kind of neurone

Answer 7

Sensory

Interneurone

Motor

Question 8

3 ways of grouping sensory neurones

Answer 8

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.)

Question 9

characteristics of sensory receptors (2)

Answer 9

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

Question 10

receptors named according to their location:

exteroceptors

interoceptors

proprioceptors

Answer 10

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.

Question 11

Receptors named according to their mode of activation

1. mechanoceptors
2. thermoreceptors
3. nociceptors
4. photoreceptors
5. chemoreceptors
6. osmoreceptors

Answer 11

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

Question 12

general somatic senses

where are they classically felt

Answer 12

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.

Question 13

cutaneous receptors are? they come in which 2 forms?

Answer 13

dendrites of sensory neurones

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

Question 14

touch sensations are due to which kind of receptor

what is:

1. crude touch
2. discriminative touch

Answer 14

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

Question 15

receptors for touch (4)

Answer 15

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

Question 16

Meissner’s corpuscles

Answer 16

• 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

Question 17

Hair root plexuses

Answer 17

• 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

Question 18

Merkel discs

Answer 18

Type I Cutaneous Mechanoreceptors

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

Question 19

▪ Ruffini corpuscles

Answer 19

Type II Cutaneous Mechanoreceptors

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

Question 20

what is pressure

how is it different to touch

what are its receptors like

Answer 20

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)

Question 21

thermal sensations

receptor

Answer 21

Receptor: free nerve endings

Some of these thermal receptors respond to heat

Others respond to cold

Question 22

pain sensations

Answer 22

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)

Question 23

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

Answer 23

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

Question 24

Nociception- 2 types:

Answer 24

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

Question 25

relief of pain anaesthesia analgesia

Answer 25

**_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

Question 26

proprioceptive sensations receptors

Answer 26

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

Question 27

somatic senory pathways are made of how many neurones?

Answer 27

3 primary, secondary and third order neurones

Question 28

what is a first order neurone

Answer 28

conduct impulses from somatic receptors into the brain stem or spinal cord * Cranial nerves: into brain stem * Spinal nerves: into spinal cord

Question 29

Second order neurone

Answer 29

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

Question 30

Posterior column tracts

Answer 30

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

Question 31

spinothalamic tract (lateral and anterior columns)

Answer 31

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

Question 32

trigeminothalamic tract

Answer 32

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

Question 33

spinocerebellar tract (anterior and posterior)

Answer 33

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

Question 34

somatic sensory distribution

Answer 34

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**)

Question 35

where does motor activity begin?

Answer 35

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

Question 36

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

Answer 36

upper motor neurone UMNs connect the brain to the appropriate level in the spinal cord

Question 37

what is the purpose of second order/ lower MNs?

Answer 37

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

Question 38

direct/ pyramidal tracts

Answer 38

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

Question 39

lateral and anterior corticospinal tracts

Answer 39

**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.

Question 40

Corticobulbar pathway

Answer 40

Impulses for the control of skeletal muscles in the head Associated with cranial nerves

Question 41

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

Answer 41

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

Question 42

what are the 5 indirect/ extra pyramidal tracts?

Answer 42

**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

Question 43

Sleep and wakefullness are functions of what part of the brain? what are they controlled by?

Answer 43

integrative functions of the cerebrum Controlled by the “reticular activating system” (RAS)

Question 44

what is the reticular formation how does the RAS system work?

Answer 44

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

Question 45

what is sleep? 2 kinds of sleep

Answer 45

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

Question 46

definitions of * learning * memory * plasticity * short term memory * long term memory * amnesia

Answer 46

**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**)**