Unit 4: Sensory, motor, and integrative system Flashcards
1
Q
Define sensation.
A
The conscious or subconscious awareness of changes in the external or internal environment.
2
Q
Define perception.
A
The conscious interpretation of sensations and is primarily a function of the cerebral cortex.
3
Q
Explain what sensory modality is.
A
Each unique type of sensation (touch, pain, vision, or hearing) is called a sensory modality.
A given sensory neuron carries information for only ONE sensory modality.
4
Q
What are the two different sensory modality classes?
A
- General senses
- Special senses
5
Q
Explain what general senses are.
A
Refers to both somatic senses and visceral senses. Somatic senses are muscular and the external environment, it includes tactile sensations, thermal sensations, pain sensations, and proprioceptors.
Visceral senses are felt internally an in the organs, provides information about conditions within internal organs.
6
Q
Explain what special senses are.
A
Includes the modalities of smell, taste, vision, hearing, equilibrium and balance.
7
Q
Where does the process of sensation begin?
A
The process of sensations begins in a sensory receptors, which can either be a specialized cell or its dendrites of a sensory neuron.
8
Q
Explain what stimulus is.
A
A change in the environment that can activate certain sensory receptors.
9
Q
Explain what selectivity is for sensory receptors.
A
A sensory receptor responds only weakly or not at all to other stimuli. This characteristic of sensory receptors is known as selectivity.
10
Q
What are the four events that typically occur for a sensation to arise?
A
- Stimulation of the sensory receptor
- Transduction of the stimulus
- Generation of nerve impulses
- Integration of sensory input
11
Q
Explain what transduction is. What do they mean by transduce?
A
A sensory receptor converts the energy in the stimulus into a graded potential, a process known as transduction. It can transduce (convert) only one kind of stimulus.
12
Q
Explain what a receptor potential is.
A
A sensory receptor responds to a stimulus by generating a graded potential known as a receptor potential.
13
Q
What are the three sensory receptors based on the location of the receptors and the origin of the stimuli that activate them?
A
- Exteroceptors: Located at or near the external surface of the body; they are sensitive to stimuli originating outside the body and provide information about the external environment. The sensations of hearing, vision, smell, taste, touch, pressure, vibration, temperature, and pain are conveyed by exteroceptors.
- Interoceptors: Or visceroceptors, are located in blood vessels, visceral organs, muscles, and the nervous system and monitor conditions in the internal environment. The nerve impulses produced by interoceptors usually are not consciously perceived.
- Proprioceptors: Located in muscle, tendons, joints, and the inner ear. They provide information about body positions, muscle length and tension, and the position and movements of your joints.
14
Q
What are the six types of stimulus detected?
A
- Mechanoreceptors: Sensitive to mechanical stimuli such as the deformation, stretching, or bending of cells. Mechanoreceptors provide sensations of touch, pressure, vibration, proprioception, hearing and equilibrium. They also monitor the stretching of blood vessels and internal organs.
- Thermoreceptors: Detect changes in temperature.
- Nociceptors: Responds to painful stimuli resulting from physical or chemical damage to tissue.
- Photoreceptors: Detect light that strikes the retina of the eye.
- Chemoreceptors: Detects chemicals in the mouth, nose, and body fluids.
- Osmoreceptors: Detects the osmotic pressure of body fluids.
15
Q
Explain what adaptation is in sensory receptors.
A
A characteristics of muscle sensory receptors is adaptation, in which the receptor potential decreases in amplitude during a maintained, constant stimulus. Because of adaptation, the perception of a sensation may fade or disappear even though the stimulus persists.
16
Q
Differentiate between rapidly adapting receptors and slowly adapting receptors.
A
Rapidly adapting receptors adapt really quickly. They are specialized for signalling changes in a stimulus.
Slowly adapting receptors adapt slowly and continue to trigger nerve impulses as long as the stimulus persists. Slowly adapting receptors maintain stimuli associated with pain, body position, and chemical composition of the blood.
17
Q
Explain what somatic sensations are.
A
They arise from stimulation of sensory receptors embedded in the skin or subcutaneous layer; in mucous membranes of the mouth, vagina, and anus; and in skeletal muscles, tendons, and joints. The areas with the highest density of somatic sensory receptors are the tip of the tongue, the lips, and the fingertips.
18
Q
Explain what cutaneous sensations are.
A
Somatic sensations that from from simulating the skin surface are cutaneous sensations. There are four modalities of somatic sensations: tactile, thermal, pain, and proprioceptive.
19
Q
Explain what tactile sensations are.
A
They include touch, pressure, vibration, itch, and tickle. Several types of encapsulated mechanoreceptors attached to large diameter myelinated A fibers mediate sensations of touch, pressure, and vibration. Other tactile sensations, such as itch and tickle sensations, are detected by free endings attached to small diameter, unmyelinated C fibers.
20
Q
Explain the touch sensations.
A
Sensations of touch generally results from stimulation of tactile receptors in the skin or subcutaneous layer.
21
Q
What are the two types of rapidly adapting touch receptors?
A
- Corpuscles of touch: or Meissner corpuscles, are touch receptors that are located in the dermal papillae of hairless skin. Because corpuscles of touch are rapidly adapting receptors, they generate nerve impulse mainly at the onset of touch.
- Hair root plexus: are rapidly adapting touch receptors found in hairy skin, they consists of free nerve endings wrapped around hair follicles.
22
Q
What are the slowly rapidly adapting touch?
A
- Type 1 cutaneous mechanoreceptors: or tactile (merkel) discs, are saucer shaped, flattened nerve endings that make contact with tactile epithelial cells of the stratum basale. These receptors responds to continues touch, such as holding an object in your hand for an extended period of time.
- Type 2 cutaneous mechanoreceptors: or ruffini corpuscles, are elongated, encapsulated receptors located in the dermis, subcutaneous layer, and other tissues of the body. They are highly sensitive to skin stretching.
23
Q
Explain the sensation of pressure. What receptors are involved?
A
A sustained sensation that is felt over a larger area than touch, occurs with deeper deformation of the skin and subcutaneous layer.
The receptors that contribute to sensations of pressure are type 1 and type 2 mechanoreceptors. These receptors are able to responds to a steady pressure stimulus because they are slowly adapting.
24
Q
Explain what the sensation of vibration is.
A
Sensations of vibration result from rapidly repetative sensory signals form tactile receptors. The receptors for vibration sensations are lamellated corpuscles and corpuscles of touch.
25
Explain what a lamellated corpuscles are.
Also called pacinian corpuscle, consists of nerve ending surrounded by a multilayered connective tissue capsule. Lamellated corpuscle adapt rapidly. They are found in the dermis, subcutaneous layer, and other body tissues.
They respond to high frequency vibrations.
26
Explain what the sensation of itch is.
The itch sensations result from stimulation of free nerve endings by certain chemicals, often because of a local inflammatory response.
Stretching usually alleviates itching by activating a pathway that blocks transmission of the itch signals though the spinal cord.
27
Explain what the tickle sensation is.
Free nerve endings are though to mediate the tickle sensation. This intriguing sensations typically arises only when someone else touches you, not when you touch yourself.
28
Explain what thermoreceptors are.
They are free nerve endings that have receptive fields about 1mm in diameter on the skins surface.
29
Explain what the cold receptors are in the thermal sensation.
Two distinct thermal sensations are detected by different receptors. Cold receptors are located in the stratum basale of the epidermis and are attached to medium -- diameter, myelinated A fibers, although a few connection to small diameter, unmyelinated C fibers.
30
Explain what the warm receptors are in the thermal sensation.
They are located in the dermis and are attached to small receptors, unmyelinated C fibers. Cold and warm receptors both adapt rapidly at the onset of a stimulus, but they continue to generate impulses at a lower frequency throughout a prolonged stimulus.
31
Explain what the pain sensation is. What are nociceptors?
Pain is indispensable for survival. It serves a protective function by signalling the presence of noxious, tissue damaging conditions.
Nociceptors are free nerve endings found in every tissue of the body except the brain. Intense thermal, mechanical, or chemical stimuli can activate nociceptors. Tissue irritation or injury releases chemicals such as prostaglandins, kinins, and potassium ion that stimulate nociceptors.
32
Differentiate between fast pain and slow pain.
The perception of fast pain occurs very rapidly, because the nerve impulses propagate along medium diameter, myelinated A fibers. Fast pain is not felt in deeper tissues of the body.
The perception of slow pain begins a second or more after a stimulus is applied. It then gradually increases in intensity over a period of several seconds or minutes.
33
Differentiate between superficial somatic pain and deep somatic pain.
Pain that arises from stimulation of receptors in the skin is called superficial somatic pain.
Stimulation of receptors in skeletal muscles, joints, tendons, and fascia causes deep somatic pain.
34
Explain what the visceral pain is.
Visceral pain results from stimulation of nociceptors in visceral organs. If stimulation is diffuse, visceral pain can be severe.
35
Explain what localization of pain is.
Fast pain is very precisely localized to the stimulated area. Somatic slow pain also is well localized but more diffuse. In some instances of visceral slow pain, the affected area is where the pain is felt.
36
Explain what referred pain is.
In some instances of visceral pain, the pain is felt in or just deep to the skin that overlies the stimulated organs, or in a surface area far from the stimulated organs. This phenomenon is called referred pain.
The visceral organ involved and the area to which the pain is referred are served by the same segment of the spinal cord.
37
Explain what proprioceptive sensations are.
Also called proprioception. Proprioceptive sensations allow us to recognize that part of our body belongs to us.
38
Explain what kinaesthesia is.
It is the perception of body movements.
39
How does proprioceptors work?
Proprioceptive sensations arise in the receptors termed proprioceptors. Because most proprioceptors adapt slowly and only slightly, the brain continually receives nerve impulses related to the position of different body parts and making adjustments to ensure coordination.
40
Explain what weight distribution is.
Proprioceptors also allow weight discrimination, the ability to asses the weight of an object. This type of information helps you to determine the muscular effort necessary to perform a task.
41
Explain what muscle spindles are.
They are the proprioceptors that monitor changes in the length of skeletal muscles and participate in stretch reflex.
42
Explain what muscle tone is.
By adjusting how vigorously a muscle spindle responds to stretching of a skeletal muscle, the brain sets an overall level of muscle tone, the small degree of contraction that is present while the muscle is at risk.
43
Explain what intrafusal fibers are.
Each muscle spindles consists of several slowly adapting sensory nerve endings that wrap around 3 to 10 specialized muscle fibers, called intrafusal fibers.
44
What is the main function of muscle spindles?
The main function of muscle spindles is to measure muscle length. Either sudden or prolonged stretching of the central area of the intrafusal muscles.
45
Explain what gamma motor neurons are.
Muscle spindles contain motor neurons called gamma motor neurons. These motor neurons terminate near both ends of the intrafusal fibers and adjust the tension in a muscle spindle to variations in the length of the muscle.
46
Explain what extrafusal muscle fibers and alpha motor neurons are.
Surrounding muscle spindles are ordinary skeletal muscle fibers, called extrafusal muscle fibers, which are supplied by large diameter A fibers called alpha motor neurons.
47
Explain what tendon organs are.
Tendon organs are slowly adapting receptors located at the junctions of a tendon and a muscle. By initiating tendon reflexes, tendon organs protect tendons and their associated muscles from damage due to excessive tension.
When tension is applied to a muscle, the tendon organs generate nerve impulses that propagate into the CNS, providing information about changes in muscle tension.
The resulting tendon reflexes decrease muscle tension by causing muscle relaxation.
48
Explain what joint kinesthetics receptors are.
Several types of joint kinesthetics receptors are present within and around the articular capsules of synovial joints. Free nerve endings and type 2 cutaneous mechanoreceptors in the capsule of joints responds to pressure.
49
Explain what somatic sensory (somatosensory) pathways are.
They relay information form somatic sensory receptors to the primary somatosensory area in the parietal lobe of the cerebral cortex and to the cerebellum.
A somatic sensory pathway to the cerebral cortex consists of thousands of sets of three neurons
- First order neuron
- Second order neuron
- Third order neuron
50
Explain what first order (primary) neurons are.
They are sensory neurons that conduct impulses from somatic sensory receptors into the brainstem or spinal cords. From the face, nasal cavity, oral cavity, teeth, and eyes, somatic sensory impulses propagate along the cranial nerves into the brainstem.
From the neck, trunk, limbs, and posterior aspect of the head somatic sensory impulses propagates along spinal nerves into the spinal cords.
51
Explain what second order (secondary) neurons are.
They conduct impulses from the brainstem or spinal cord to the thalamus. Axons of the second - order neurons decussate as they course through the brainstem or spinal cord before ascending to the thalamus.
52
Explain what decussate mean.
To cross over to the opposite sides.
53
Explain what third order (tertiary) neurons are.
They conduct impulses from the thalamus to the primary somatosensory area on the same side. As the impulses reach the primarily somatosensory area, perception of the sensation occurs. Because the axons of second order neurons decussate as they pass through the brainstem or spinal cord, somatic sensory information on one side of the body is perceived by the primary somatosensory area on the opposite side of the brain.
54
Explain what relay stations are in the CNS.
Regions within the CNS where neurons synapse with other neurons that are a part of a particular sensory or motor pathway are known as relay stations because neural signals are being relayed from one region of the CNS to another.
55
What are the three general pathways of the somatic sensory impulses?
- The posterior column - medial leminiscuss pathway
- The anterolateral (spinothalamic) pathway
- The trigeminothalamic pathway
56
How does the somatic sensory impulse reach the cerebellum?
Somatic sensory impulses reach the cerebellum via the spinocerebellar tracts.
57
Explain what the posterior column - medial lemniscus is.
Nerve impulses for touch, pressure, vibration, and proprioceptors from the limbs, trunk, neck, and posterior head ascend to the cerebral cortex along the posterior column - medial lemniscus pathway.
58
What forms the upper and lower limb proprioceptors.
Nerve impulses for touch, pressure, vibration, and conscious proprioception from the upper limbs, upper trunk, neck, and posterior head propagate along axons in the cuneate fasiculus and arrive at the cuneate nucleus.
Nerve impulses for touch, pressure, vibration, and conscious proprioception from the lower limbs, and lower trunk propagate along axons in the gracile fasiculus and arrive at the gracile nucleus.
59
Explain what the medial lemniscus is.
The axons of the second order neurons cross to the opposite side of the medulla and other medial lemniscus, a thin ribbon like projection tract that extends from the medulla to the ventral posterior nucleus of the thalamus.
60
Explain what the anterolateral (spinothalamic) pathway is.
Nerve impulses for pain, temperature, itch, and tickle from the limbs, trunk, neck, and posterior head ascend to the cerebral cortex along the anterolateral (spinothalamic) pathway.
61
Explain what the trigeminothalamic pathways are.
Nerve impulses for most somatic sensations from the face, nasal cavity, oral cavity, and teeth ascend to the cerebral cortex along the trigeminothalamic pathway.
62
Explain what the trigeminothalamic tract is.
The axons of the second neurons cross to the opposite side of the pons and medulla and then ascend as the trigeminothalamic tract to the ventral posterior nucleus of the thalamus.
In the thalamus, the axon terminals of the second order neurons synapse with third order neurons, which projects their axons to the primary somatosensory area on the same side of the cerebral cortex as the thalamus.
63
Explain what the somatic sensory map and the somatic motor map is.
Specific areas of the cerebral cortex receive somatic sensory input from particular parts of the body. Other areas of the cerebral cortex provide output in the form of instructions for movements of particular parts of the body.
The somatic sensory map and the somatic sensory map and the somatic motor map relate body parts of these cortical areas.
64
Explain what the primary somatosensory area is.
Precise localization of somatic sensations occur when nerve impulses arrive at the primary somatosensory area; which occupies the post central gyri of the parietal lobes of the cerebral cortex. Each region in this area receives sneosry input from a different part of the body.
65
Explain what the sensory homunculus is.
Some part of the body provide input to large regions in the somatosensory area. Other parts of the body, such as the trunk and lower limbs, project to much smaller cortical regions. The relative size of these regions in the somatosensory area proportional to the number of specialized sensory receptors within the corresponding part of the body. This distorted somatic sensory map of the body is known as the sensory homunculus.
66
Differentiate between anterior spinocerebellar tract and the posterior spinocerebellar tract.
They are the two tracts in the spinal cord. And are the major routes propriocetive impulses take to reach the cerebellum.
Although they are not consciously perceived, sensory impulses conveyed to the cerebellum along these pathways are critical for posture, balance, and coordination of skilled movement.
67
Explain what the anterolateral pathways.
Conveys nerve impulses for pain, cold, warmth, itch, and tickle from limbs, trunk, neck, and posterior head. Axons of first order neurons from one side of the body synapse with dendrites and cell bodies of second order neurons in posterior grey horn on same side of body.
Axons of second order neurons decussate, enter spinothalamic tract on opposite side, and extend to thalamus. Third order neurons transmit nerve impulses from thalamus to primary somatosensory area on side opposite the site of stimulation.
68
Explain what the posterior column-medial lemniscus pathway.
It conveys nerve impulses for touch, pressure, vibration, and conscious proprioception from upper limbs, upper trunk, neck, and posterior head, and gracile fasciculus conveys nerve impulses touch, pressure, vibration, and conscious proprioception from lower limbs and lower trunk. Axonsof first order neurons from one side of body forms posterior column on same side and end in medulla, where they synapse with dendrites and cell bodies of second order neurons.
Axons of second order neurons decussate, enter medial meniscus on opposite side, and extend to thalamus.
Third order neurons transmit nerve impulses from thalamus to primary somatosensory area on side opposite the site of stimulation.
69
Explain what the trigeminothalamic pathway.
Conveys nerve impulses for touch, pressure, vibration, pain, cold, warmth, itch, and tickle from face, nasal cavity, oral cavity, and teeth.
Axons of first order neurons from one side of head synapse with dendrites and cell bodies of second order neurons in pons and medulla on same side, and extend to thalamus. Third order neurons transmit nerve impulses from thalamus to primary somatosensory area on side opposite the site of stimulation.
70
Explain what the anteiror and posterior spinocerebellar pathways is.
Convey nerve impulses from proprioceptors in trunk and lower limb of one side of body to same side of cerebellum. Proprioceptive input informs cerebellum of actual movements, allowing it to coordinate, smooth, and refine skilled movements and maintain posture and balance.
71
Explain what loser motor neurons (LMNs) are.
Neural circuits in the brain and spinal cord orchestrate all voluntary movements. All excitatory and inhibitory signals that control movements converge on the motor neurons that extend out of the brainstem and spinal cord to innervate skeletal muscles in the body. These neurons are known as lower motor neurons because they have their cell bodies in the lower parts of the CNS.
72
Explain what the local circuit neurons are.
Input arrives at lower motor neurons from nearby interneurons called local circuit neurons. These neurons are located close to the lower motor neuron cell bodies in the brainstem and spinal cord.
They help coordinate rhythmic activity in specific muscle groups.
73
Explain what upper motor neurons are.
Both local circuit neurons and lower motor neurson receive input from upper motor neurons, neurons that have cell bodies in motor processing centres in the upper parts of the CNS. Most upper motor neurons synapse with local circuit neurons, which in turn synapse with lower motor neurons.
Upper motor neurons from the cerebral cortex are essential for the planning and execution of voluntary movements of the body.
Upper motor neurons from the brainstem help regulate posture, balance, muscle, and reflexive movements of the head and trunk.
74
Explain what the basal nuclei nuerons are.
They assists movement by providing input to upper motor neurons. Neural circuits interconnect the basal nuclei with motor areas of the cerebral cortex and the brainstem. These circuit help initiate and terminate movements, suppress unwanted movements and establish a normal level of muscle tone.
75
Explain what the cerebellar neurons.
They also aid movement by controlling the activity of upper motor neurons. Neural circuits interconnect the cerebellum with motor areas of the cerebral cortex and the brainstem.
A prime function of the cerebellum is to monitor differences between intended movements and movements actually performed. Then, it issues commands to upper motor neurons to reduce errors in movements. The cerebellum thus coordinates body movements and helps maintain normal posture and balance.
76
What are the roles of the premotor areas?
The role of the premotor area in body movements is as follows:
- The idea or desire to move a part of the body is
generated in one or more cortical association areas, such
as the prefrontal cortex, somatosensory association
areas, auditory association area, or visual association.
- This information is sent to the basal nuclei, which
process the information and send it to the thalamus and
then to the premotor area, where a motor plan is
developed. This plan identifies which muscles should
contract, how much they need to contract, and in what
order.
- The premotor area also stores information about learned motor activities. By activating the appropriate neurons of the primary motor area, the premotor area causes specific groups of muscles to contract i na specific sequence.
77
Explain what the primary motor area is.
The primary motor area is the major control region for the execution of voluntary major control region for the execution of any point in the primary motor areas causes contraction of specific muscles on the opposite side of the body.
The primary motor area controls muscles by forming descending pathway motor area controls muscles by forming descending pathway that extend to the spinal cord and brainstem.
78
Explain what the motor homunculus is.
More cortical area is devoted to those muscles involved in skilled, complex, or delicate movements. Muscles in the thumb, finger, lips, tongue, and vocal cords have large representations; the trunk has a much smaller representation. This distorted muscle map of the body is called the motor homunculus.
79
Explain what the direct motor pathways are.
They provide input to lower motor neurons via axons that extend directly from the cerebral cortex.
80
Explain what the indirect motor pathways are.
They provide input to lower motor neurons from motor centres in the brainstem. Direct and indirect pathways both govern generation of action potentials in the lower motor neurons, the neurons that stimulate contraction of skeletal muscle.
81
Explain what the pyramidal pathways is.
Action potentials for voluntary movements propagate from the cerebral cortex to lower motor neurons via the direct motor pathways. Also known as the pyramidal pathways.
82
Explain what the pyramidal cells are.
The direct motor pathways consists of axons that descend from pyramidal cells of the primary motor area and premotor area, pyramidal cells are upper motor neurons that have pyramidal shaped cells bodies. They are the main output cells of the cerebral cortex.
83
What consists of direct motor pathways?
The direct motor pathways consists of corticospinal pathways and the corticobulbar pathway.
84
Explain what the corticospinal pathways are.
They conducts impulses for the control of muscles of the limbs and trunk.
85
Explain what the corticospinal tracts are.
Axons of upper motor neurons in the cerebral cortex form the corticospinal tracts, which. descend through the internal capsule of the cerebrum and the cerebral peduncle of the midbrain.
86
What forms the pyramids in the medulla oblongata?
In the medulla oblongata, the axon bundles of the corticospinal tracts form the ventral bulges known as the pyramids.
87
What are the two types of corticospinal tracts?
- Lateral corticospinal tracts
- Anterior corticospinal tracts
88
Explain what the lateral corticospinal tracts are.
Corticospinal axons that decussate in the medulla form the lateral corticospinal tract in the lateral white column of the spinal cord.
Axons of these lower motor neurons exit the cord in the anterior roots of spinal nerves and terminate in skeletal muscles that control movements of the distal parts of the limbs.
The distal muscles are responsible for precise, agile, and highly skilled movements of the hands and feet.
89
Explain what the anterior corticospinal tracts are.
Corticospinal axons that do not decussate in the middle form the anterior corticospinal tract in the anterior while column of the spinal cord.
Axons of these lower motor neurons exit the cord in the anterior roots of the spinal nerves. They terminate in skeletal muscles that control movements of the trunk, and proximal parts of the limbs.
90
Whats the purpose of the corticobulbar pathways?
They conduct impulses for the control of skeletal muscles in the head.
91
Explain what the corticobulbar tracts.
Axons of the upper motor neurosn form the cerebral cortex form the corticobulbar tracts, which descends along with the corticospinal tracts through the internal capsule of the cerebrum and cerebral peduncle of the midbrain.
92
What are the nine pairs of cranial nerves that the axons terminate in the motor nuclei?
- The occulomotor (3)
- Troclear (4)
- Trigeminal (5)
- Abducens (6)
- Facial (7)
- Glossopharyngeal (9)
- Vagus (10)
- Accessory (11)
- Hypoglossal (12)
93
What does the lower motor neurons of the cranial nerves convey?
The lower motor neurons of the cranial nerves convey impulses that control precise, voluntary movements of the eye, tongue, and neck, plus chewing, facial expression, speech, and swallowing.
94
What are the major four major motor centres that help regulate body movement in the brainstem?
- The vestibular nuclei in the medulla and pons
- The reticular formation located throughout the
brainstem
- The superior colliculus in the midbrain
- The red nucleus, also present in the midbrain
95
Explain what the indirect motor pathway is.
The brainstem motor centres give rise to the indirect motor pathways, also known as extrapyramidal pathways, which include all the somatic motor tracts other than the corticospinal and corticobulbar tracts.
96
What are the five tracts the axons of the upper motor neurons descend from the brainstem?
- Rubrospinal
- Tectospinal
- Vestibulospinal
- Lateral reticulospinal
- Medial verticulospinal tracts
97
Whats the purpose of the indirect motor pathway?
They convey action potentials from the brainstem to cause involuntary movements that regulate, posture, balance, muscle tone, and reflexive movements of the head and trunk.
Except the rubrospinal tract, which plays an ancillary role to the lateral corticospinal tract in the regulation of voluntary movements of the upper limbs.
98
What does the postural reflexes do?
They keep the body in an upright and balanced position.
99
What are the three input for postural reflexes come from?
- They eyes, which provides visual information about the
position of the body in space.
- The vestibular apparatus of the inner ear, which provides
information about the position of the head.
- Proprioceptors in muscles and joints, which provide
information about the position of the limbs.
100
Why is the vestibular nuclei important for posture?
The vestibular nuclei play an important role in the regulation of posture. They receive neural input from the vestibulocochlear nerve regarding the state of equilibirum of the body and neural input from the cerebellum.
In response to this input, the vestibular nuclei generate action potentials along the axons of the vestibulospinal tract, which conveys signals to skeletal muscles of the trunk and proximal parts of the limbs.
The vestibulospinal tract causes contraction of these muscles in order to maintain posture in response to changes in equilibrium.
101
Explain what the reticular formation is.
The reticular formation also helps control posture. In addition, it can alter muscle tone. The reticular formation receives input from several sources, including the eye, ear, cerebellum, and basal nuclei.
In response to this input, discrete nuclei in the reticular formation generate action potentials along the medial reticulospinal tracts and lateral reticulospinal tracts, both of which conveys signals to skeletal muscles of the trunk and proximal limbs.
102
Differentiate between the medial reticulospinal tract and the lateral reticulospinal tract.
The medial reticulospinal tracts excites the skeletal muscles of the trunk and extensor muscles of the proximal limbs, where as the lateral reticulospinal tract inhibits the skeletal muscles of the trunk and extensor of the proximal limbs.
The medial and lateral reticulospinal tracts work together to maintain posture and regulate muscle tone during ongoing movements.
103
Explain what the superior colliculus is.
They receive visual input from the eyes and auditory input from the ears, when this input occurs in a sudden, unexpected manner, the superior colliculus produces action potentials along the tectospinal tract, which conveys neural signals the activate skeletal muscles in the head and trunk.
104
Explain what the saccades is.
The superior colliculus is also an integrating centre of saccades, a small, rapid, jerking movements of the eyes that occur as a person looks at different points in their visual fields.
105
Explain what the red nucleus is.
It receives input from the cerebral cortex and the cerebellum. In response to this input, the red nucleus generates action potentials along the axons of the rubrospinal tract, which conveys neural signals that activate skeletal muscles that cause fine, precise, voluntary movements of the distal parts of the upper limbs.
106
What happens when the corticospinal tract is damaged?
The rubrospinal tract tract plays only a minor role in the contracting muscles of the distal parts of the upper limbs. however, the rubrospinal tract becomes functionally significant if the lateral corticospinal tract is damaged.
107
What are the purpose of the cerebellum?
In addition to maintaining proper posture and balance, and cerebellum is active in both learning and performing rapid, coordinated, highly skilled movements cerebellar.
108
What are the four cerebellar function involves four activities?
- Monitoring intentions for movements: the cerebellum
receives input impulses from the motor cortex and basal
nuclei via the pontine nuclei in the pons regarding what
movements are planned.
- Monitoring actual movements: The cerebellum receives
input from proprioceptors in joints and muscles that
reveal what actually is happening.
- Comparing command signals with sensory information:
The cerebellum compares intentions for movement with
the actual movement performed.
- Sending out corrective feedback: If there is a discrepancy
between intended and actual movement, the cerebellum
sends feedback to upper motor neurons. As movement
occurs, the cerebellum continuously provides error
corrections to upper motor neurons, which decreases
errors and smoothes the motion. Over longer periods it
also contributes to the learning of new motor skills.
109
Define what integration is.
The processing of sensory information by analyzing and storing it and making decisions for various responses.
110
Explain what the integrative functions is.
They include the cerebral activities such as sleep, and wakefulness, and learning and memory, and language.
111
What establishes the circadian rhythm?
Humans sleep and awaken in a 24hr cycle called a circadian rhythm, that is established by the suprachiasmatic nucleus of the hypothalamus.
112
Explain what role of the reticular activating system in awakening.
A portion of the reticular formation is known as the reticular activating system. When this area is active, many nerve impulses are transmitted to widespread areas of the cerebral cortex. The effect is a generalized increase in cortical activity.
113
Explain what arousal means.
Also called awakening from sleep, also involves increased activity in the reticular activating system. For arousal to occur, the RAS must be stimulated. Once the RAS is activated, the cerebral cortex is also activated, and arousal occurs. The result is a state of wakefulness called consciousness.
114
Explain what sleep means.
It is a state of altered consciousness or partial unconsciousness from which an individual can be aroused. Sleep deprivation impairs attention, learning, and performance. Normal sleep consists of two components. Non rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep.
115
What are the four stages of non rapid eye movement?
- Stage 1: A transition stage between wakefulness and
sleep. The person is relaxed with eyes closed and has
fleeting thoughts.
- Stage 2: Or light sleep. The first stage of true sleep. In it, a
person is easy to awaken. Fragments of dreams may be
experienced, and the eyes may slowly roll from side to
side.
- Stage 3: A period of moderately deep sleep. It is more
difficult to awaken the person.
- Stage 4: The deepest level of sleep. Brain metabolism
decreases significantly by most reflexes are intact and
muscle tone is decreased only slightly. At this stage, it is
very difficult to awaken a person.
116
What physically happens to the body during non rapid eye movements?
There are decreases in heart rate, respiratory rate, and blood pressure. Muscle tone also decreases but only slightly.
117
What happens during the rapid eye movement?
The eyes move rapidly back and forth under closed eyelids. REM sleep is also known as paradoxical sleep because EEG readings taken at this time is similar to those who are awake.
It is even more difficult to awaken a person during REM sleep than during any stages of NREM.
118
What physically happens to the body during rapid eye movement?
Heart rate, respiratory rate, and blood pressure increases during REM sleep. Most somatic motor neurons are inhibited during REM sleep, which causes a significant decrease in muscle ton and even paralyzes the skeletal muscles.
REM sleep is also the period when most dreaming occurs.
119
What induces non rapid eye movement and rapid movement?
NREM sleep is induced by NREM sleep centres in the hypothalamus and basal forebrain; whereas REM sleep is promoted by a REM sleep centre in the pons and midbrain.
120
Explain what a coma is.
It is a state of unconsciousness in which an individual has little or not response to stimuli. Causes of coma include head injuries, damages to the reticular activation system, brain infection, alcohol infections, alcohol intoxication, and drug overdose.
If brain damage is severe and irreversible, recovery is unlikely.
121
Explain what a persistent vegetative state is.
After a few weeks of being in a coma, some patients enter into a persistent vegetative state in which the patient has normal sleep wake cycles but does not have an awareness of the surrounding.
People who are in a coma or a persistent vegetative state are not brain dead.
122
Explain what leaning means.
The ability to acquire new information or skills though instructions or experience. There are two main categories of learning, associative learning and non associative learning.
123
Differentiate between associative learning and non associative learning.
Associative learning occurs when a connection is made between two stimuli. Non associative learning occurs when repeated exposure to a single stimulus causes a change in behaviour.
124
What are the two types of non associative learning?
- Habituation
- Sensitization
125
Explain what habituation in non associative learning is.
Repeated exposure to an irrelevant stimulus causes a decreased behavioural response.
Habituation demonstrates that an animal has learned to ignore an unimportant stimulus.
126
Explain what sensitization is in non associative learning.
Repeated exposure to a noxious stimulus causes an increase in behavioural response. Sensitization demonstrates that an animal has learned to respond more quickly to a harmful stimuli.
127
Explain what memory means.
Is the process by which information acquired through learning is stored and retrieved.
Memory occurs in stages over a period of time
128
What are the two types of memory?
- Declarative memory
- Procedural memory
129
Explain what declarative (explicit) memory is.
The memory of experiences that can be verbalized such as facts, events, objects, names, and places. This type of memory requires conscious recall and is stored in the association areas of the cerebral cortex.
130
Explain what procedural (implicit) memory is.
The memory of motor skills, procedures, and rules. This type of memory does not require conscious recall, and it is stored in the basal nuclei, cerebellum, and premotor area.
131
Explain what short term memory is.
The temporary ability to recall a few pieces of information for seconds or minutes.
132
Explain what long term memory is.
Information in short term memory may later be transformed into a more permanent type of memory, called long term memory.
133
Explain what memory consolidation is.
The process by which a short term memory is transformed into a long term memory is called memory consolidation. A key factor that contributes to memory consolidation is repetition.
134
Explain what plasticity in memory is.
For an experience to become part of long term memory, it must produce persistent structural and functional changes that represent the experience in the brain. This capability for change associated with learning is termed plasticity.
It involves changes in individuals neurons as well as change in the strength of synaptic connections among neurons.
135
Explain what long term potentiation (LTP) is.
A phenomenon called long term potentiation is believed to underlie some aspects of memory; transmission at some synapses within the hippocampus is enhanced for ours or weeks after a brief period of high frequency stimulation.
136
Explain what language means.
A system of vocal sounds and symbols that conveys information. Most commonly it is spoken and/or written.
137
What are the two language areas of the cerebral cortex?
- Wernicke's area
- Brocas area
138
Explain what the Wernicke's area is.
An associated area in the temporal lobe, interprets the meanings of written or spoken words. It essentially translates words in thoughts.
139
Explain what the Broca's area is.
A motor area located in the frontal lobe, is activated as you translate thoughts into speech.
