Functional Antaomy of the Brain and Neural System

Question 1

What are the major components of the Nervous System, and what are they comprised of?

Answer 1

The Nervous System
-Central Nervous System (CNS)
-Brain
-Spinal cord
Peripheral Nervous System (PNS)
-Cranial Nerves
-Spinal Nerves
-Autonomic Nervous system,

Question 2

What are the directioal terms used in Anatomy ?

Answer 2

Directional Terms in Anatomy:
- Dorsal < > Ventral
Dorsal (front)
-Rostral < > Caudal
rostral (front)
-Anterior< > Posterior
refer to long axis of body (do not change)
-Medial < > Lateral
3 planes: Axial (cut off by bridge) , Saggital (slice through nose) and Coronal (MRI; cut through ears)

Question 3

What are the 4 principle regions of the brain?

Answer 3

Principle regions of the brain:
-Cerebrum
-cerebellum
-Diencephalon
-Brainstem

spinal cord

Question 4

What are the unique features of the cerebrum, including its functions?

Answer 4

Cerebrum
-LARGEST, most developed part of the human brain
-makes up 83% of brain mass
-Has 2 hemispheres (left, right) that are separated by Longitudinal fissure
-Responsible for complex actions of consciousness
-Memory
-Personality
-Intelligence
(motor movement, perception)

Question 5

Describe the components of the Cerebral cortex (that’s a part of cerebrum) and also the type of folds it has,

Answer 5

Cerebral cortex (part of Cerebrum) 2.4 m thick
-Grey Matter (neuronal cell bodies); nuclei gives it the dark color
-White Matter (myelinated axons)-
contains Myelin, a specialized lipid-rich layer that covers neuronal axons (myelin give matter its white color)
Folds and cerebral cortex
-Gyri (s. gyrus) (ridges of fold)
-Sulci (s. Sulcus) ) (indentations)
-fissures used to designate area of hemispheres

Question 6

What are the cerebral hemispheres that are located in cerebral cortex? What are the Areas that these hemispheres correspond to?

Answer 6

Cerebral Hemispheres :
-Frontal
-Parietal
-Occipital
-Temporal

Areas:
SENSORY areas that deal with the perception of sensory information (occipital)
- MOTOR areas that control voluntary movement execution (frontal)
-Association areas that integrate complex functions (frontal, temporal cortex)

Question 7

What are the subcortical structures of the cerebrum and what are their roles ?

Answer 7

Cerebrum: subcortical structures
-Thalamus: “gatekeeper” of the cortex
-Basal Ganglia: intention motor movement
-Amygdala: emotional balance (moods)
-Hippocampus- memory (memory formation, recall)
-Hypothalamus- neuroendocrine function (like stress response)

Question 8

What occurs in the Ventral Pathway?

Answer 8

Ventral pathway:
System of brain cavities containing cerebral spinal fluid CSF)
-CSF- the supporting medium (milieu) of electrolytes sugars, that keep brain alive and keep it structurally together
-CSF- flushing waste products out the brain (known as lymphatic system)

Question 9

Describe the flow of CSF in the brain

Answer 9

Flow of CSF (cerebral spinal fluid) :
1. CSF is extracted from blood and generated in choroid plexus
2. This CSf flows through intraventricular foramen, through the Third ventricle.
3. CSF then moves from third ventricle, through the cerebral acqueduct, to fourth ventricle
4. CSF then moves to the central canal of spinal cord, up and around to subarachnoid space and released back into blood stream.

Question 10

Discuss the features of the cerebellum and its functions

Answer 10

Cerebellum:
aka “Little Brain”
-second largest part of the brain
-11% of brain mass
-Folds increase surface area and allow for greater number of neurons

Functions:
coordinates skeletal muscle contractions
-Regulates balacne and posture (hence first region to be affected by alcohol )
-May have a role in language processing and recognition

inferior and poster to cranial cavity

Question 11

What are the three components of the Brainstem?

Answer 11

Principle Region of Brain: Brainstem
Composed of 3 parts;
- Midbrain
-Pons
-Medulla Oblongata

Question 12

Discuss the features of the spinal cord and the different regions involved. What is the conus megularis? Filum terminale?

Answer 12

Spinal Cord
-45 cm in length
-Passes through the foramen magnum
-Extends from the brain to L1(first. lumbar)
Consists of:
Cervical region (C1-C8)
Thoracic region (T1-T12)
Lumbar region (L1-L5)
-region between L1 and L2 is the Conus megualris
Sacral region (S1- S5)
Coccygeal region (Co 1)
Filum terminale fiber t hat- anchors spinal cord and dural sac to coccyx (holds spinal cord to gether)

caudal equina (aka horse tail) - contain the rest of fibers from spinal cord called (from cona medularis to coccyx); contain lumbar and sacral nerve roots

Question 13

Is the spinal cord shorter or longer than the vertebrate? why?

Answer 13

Spinal cord is much shorter than vertebrate, because when you are born they are same length. However as you grow, only nerves from lumbar and sacral region, and coccyx region extend to support growth. The spinal cord does NOT grow or get longer, as you are growing

Question 14

What are meninges and what is the role of each component ?

Answer 14

The Meninges: Three membranes that surround all of the CNS
1) Dura Mater- “tough mother”, strong (outer layer of meninges)
2) Arachanoid Meninx- spidery looking, carries blood vessels, etc
- has subarachnoid space-
3) Pia mater- “delicate Mother”, adheres tightly to surface of brain and spinal cord.
these meninges create a barrier and protect the system of the body

Question 15

Explain what occurs in the embryonic development of Neural Tube. what are the two sections that divide the Neural Tube?

Answer 15

Embryonic Development if Neural Tube:
Nervous System is generated from neural tube
-Neural Tube divided into two sections of transverse section, midsaggital section; and dorsal view (exterior)
Notocord drives formation of neural plate; that will then go through cell proliferation, which drives formation of neural groove and a neural fold which extends from top to bottom. This fold fuses into neural tube creating completion of Neuralation

Question 16

What are the detailed steps of Neural tube formation?

Answer 16

Steps of Neural Tube formation:
1a SHAPING of the neural plate
1b. FOLDING of the neural plate by Notochord
2. ELEVATION: Notochord will enhance cell proliferation and form a neural groove and later form neural crest
3. CONVERGENCE- As cell proliferation continues, neural crest will fuse together with neural plat and complete Neural tube formation
4. Closure- Neural tube complete fold, all parts of neural plate close up on each other.

Question 17

What are two medical conditions that result from Neuropore closure failure ?

Answer 17

Neuroppore closure failure:
1. Anencephaly- failure of the neural tube to close at ANTERIOR end
-birth defect, where part of skull is missing, fatal condition (babies die before birth or few days, weeks after)
2. Spina- Bifida- failure of the neural tube to close at POSTERIOR end
-spinal cord does not form properly; treatable

Question 18

Describe what occurs during Brain development, by comparing what occurs 5 weeks after conception vs 7 weeks. Include the new structures that are made

Answer 18

Brain development:
-Once neuropore forms, Expansion and Differentiation occurs.
-5 weeks after conception: 3 primary vesicles
1. Prosencephalon (forebrain)
2. Mesencephalon (midbrain)
3. Rhombencephalon (hindbrain)
also have spinal cord
-7 weeks after conception: cell proliferation and differentiation and have 5 secondary vesicles
1.Lateral ventricles form from prosencephalon
and they are part of telencephalon; optic vesicle
2. Third ventricle forms
3. Fourth ventricle form
4. Medulla forms from Rhombencephalon
5. Diencephalon
also formation of cerebral aqueduct and pons

-myencephalon- medulla
-metencephalon- pons

Question 19

What kind of model does neural tube formation resemble?

Answer 19

Brain development;
When Neural tube forms and grows, it resembles the Ram horns model
-as the neural tube grows, it will fold in upon itself and continue to curl around and around, (until forming isocorteox, which invaginates and we see the cerebrum)

Question 20

What are the segments and nerves that are in spinal cord?
Which spinal nerves exit below their corresponding vertebrae?

Answer 20

Spinal Cord
-31 segments/pairs of spinal nerves
-8 cervical
-12 thoracic
-5 lumbar
-5 sacral
-1 coccygeal
-ALL spinal nerves Except First, exit below their corresponding vertebrae
(ex: T1 spinal nerve exits below T1 vertebrae)

as body grows, spinal cord must accommodate by elongating spinal nerves from T12-lumbar-saccral

Question 21

What are Spinal Segment Dermatomes and where are they located in the body?

Answer 21

Spinal Segment Dermatomes: patches of skin (each supplied by spinal nerve)
cervical regions- arms, hands
thoracic- abdomen, chest area
lumbar- legs
saccral- posterior side of legs

Question 22

What is the benefit of Dermatomes in the Quadruped Position?

Answer 22

Dermatomes in Quadruped Position:
- you can see more clearly how spinal segments are related to dermatomes
-cervical- dermatomes in nose all the way to hand
-Thoracic- dermatomes from hands to belly button
Lumbar- legs
sacral- backside and legs

Question 23

What are spinal segments and what do they all comprise of?

Answer 23

Spinal Segments; repeating architecture/organization; section of spinal cord)
Spinal segments contain;
1. Central canal
-CSF (cerebrospinal fluid) from 4th ventricle
2. Gray matter
-H shaped (butterfly)
-SENSORY and MOTOR nuclei (soma), unmyelinated processes and neuroglia
3. White matter
-OUTSIDE of gray matter
-Myelinated and unmyelinated fibers

-

Question 24

What is the orientation of gray and white matter in the spinal cord vs brain?

Answer 24

Spinal cord:
gray matter: interior
-white matter- Exterior

Brain (opposite way)
-gray matter: Exterior
White matter: interior

Question 25

What are the two branches of spinal nerves?

Answer 25

2 branches of spinal nerves:
1. Ventral root: (Outputs)
-contains axons of MOTOR neurons
2. Dorsal root: (Inputs)
-contain axons of SENSORY neurons (ex; touch, pain)
Dosal Root ganglia:
-contain cell bodies of sensory neurons
-called Psuedounipolar neurons

-these cell bodies in ganglion extends fibers to spinal segments or medulla

Question 26

What are the two enlargements that occur in the spinal cord? Why does this happen?

Answer 26

Two enlargements:
-Cervical enlargement
-C3 to T1
(cervical 3 is enlarged compared to T1)
-Lumbar enlargement
L1 to S2
Gray matter is expanded (during enlargement) to incorporate more sensory input from limbs, and more cell bodies for motor control of limbs

Question 27

Desceibe the neuronal organization that can be seen in the spinal cord, including what the role Laminal region, II, III, IV, VII, VIII, and IX in the gray matter of spinal cord? What neurons do they have?

Answer 27

Neuronal Organization: made up of 10 zones of cells in the gray matter called renga Lamina
10 Laminas
Lamina I, and II: have cell bodies that process pain inputs coming from dorsal root ganglia
Lamina III, IV- process info related to Touch: temperature, crude touch and pain
Lamina VII, VIII, IX : process info related to motor outputs
Lamina VII: have Renchal cells which are inhibitory neurons in the cell
Lamina VIII ; motor neurons that innervate distal musculature (legs)
Lamina IX: have alpha motor neurons innervate core musculature, intercostal, ribcage and diaphragm

Question 28

What are Reflexes?

Answer 28

Reflexes: fast, stereotypical, inborn, protective actions
-occur at spinal cord or brainstem levels
-May be either monosynaptic or polysynaptic

Question 29

What do all reflexes require ?

Answer 29

Reflexes all require:
1. Stimulus at receptor
2. sensory information relay
3. processing at CNS level
4. activation of motor response
5. response of peripheral effector

Question 30

Describe the mechanism of patellar stretch and how synapses occur to activate muscle groups and neurons

Answer 30

Patellar stretch by hitting of hammer, causes stretch of quadriceps muscle
The activation of muscle spindle fibers will cause a synapse on monosynaptic synapse that innervates and activates that muscle group
The stretch activates the muscle spindle and 1A fiber which synapses into lamina 7 (contain renchal neurons which are inhibitory interneurons)
when these inhibitory neurons are activated, they inhibit the motor neurons that are heteronomous innervating opposing muscle group (try to inhibit opposing muscle group
(hence heel kicks up as reflex when hit knee with hammer)

Question 31

What are the 2 principle Somatic Sensory Pathways?

Answer 31

Principle Sensory Pathways (dependent on sensory modality)
1. Fine Touch Pathway (ex: run fingers through paper)
Sensory information comes in through dorsal root, does not synapse. Those fibers enter fasciculus gracilla and Fasciculus cuneatus and ascends into the medulla.
-neruons in the Fine Touch pathway do NOT synapse until they reach medulla.
As you ascend the spinal column, as more fibers come in through dorsal root, they continue pack in, pushing all fibers medially (hence why leg to neck across fasiculus)
-Fasiculus gravilla and Cuneatus- have fibers inne

Side Note: Normally, fibers innervating leg- medial
upper trunk, arm and neck- lateral

2. Pain pathways
   -Sensory info comes from C fiber and A delta fiber through the dorsal root
   -However they will synapse on Laminas I- IV (unlike in fine touch pathway)
   The second neuron in pathway sends fiber that desiccate, or CROSS to other side at that spinal segment. Once crossed, the fibers ascend through neuralspinal thalamotract or anterior lateral system of tracts. Either neurospinal tract or paleo tract will make tertiary synapse cerebral cortex

Question 32

Differentiate between Paleospinal Thalamotract and Neurospinal Thalamotract in terms of where they synapse and what. kind of pain signals there transmit

Answer 32

Paleospinal thalamotract- synapses at Brainstem reticular formation

Neuralspinal thalamotract- ascend directly into thalamus
Both paleo and neuralspinal thalamotract make tertiary synapse to cerebral cortex
.
Neurospinal thalamotract: fast pain signals elicited by mechanical or normal stimuli (ex; if you cut yourself)

Paleospinal thalamus- slow, chronic pain signals being transmitted by slow, C- fibers. (ex: throbbing, dull pain)
-older version

Question 33

Discuss the clinical presentation of lesions and how the synaptic mechanism is affected by the lesion

Answer 33

Clinical presentation of lesions (patient)
-T11 injury
-Dorsal column lesion
-Loss of all proprioception and vibration sensation below lesion (belly button)
-pain sensation and motor remain intact

Process:
Level of T11 corresponds to belly button; the Fine touch comes into dorsal roots, which immediately ascends through dorsal columns;, at that level of lesion and below brain, there is no proprioreception
hence that’s why the information will not ascend into brain, hence proprioreceptor, vibration below lesion does not exist, so you have lost that sensation.
Pain synapses in Lamina I-IV, desiccates and then ascends toward more ventral area; where pain is ascending is spared (hence individual can feel pain and temp below region site, not fine touch)
motor regions will descend in ventral region (which are spared)

Question 34

Is the patellar region intact with the T11 lesion?

Answer 34

YES patellar region is intact (with T11 lesion) because patellar reflex occurs at spinal segment which is intact. so with this lesion, you won’t have fine touch, but reflex are still intact.

Question 35

Discuss the case with the L1 Hemicord lesion and how it affects the function of patient’s body. what is this lesion an example of ?

Answer 35

L2 Hemicord lesion
-17-year old was stabbed at level T12/L1 in the back
-Significant muscle weakness affecting the whole right Lower extremity
-Impaired vibration and proprioreception sense of the right leg
-Loss of pain and temperature sense of the left leg
The motor tracks running down right hand side exit through ventral root (hence lesion through right side of spinal segment, have deficits in motor movement
-somatosensation from right hand side is lost from lesion side (due to leafing dorsal columns)
pain and temperature is lost on contralateral side b/c pain and temp info below region sit, come in synapse and desiccate
-paralysis , lose proprioeeception and vibration on ispilateral side
This L2 lesions is a reminder of Brown Sequard syndrome- lesionof spinal cord that results in the weakness or paralysis by one side of the body and loss of sensation on other side of body

Question 36

How many Cranial Nerves are there? What categories do these nerves fall into?

Answer 36

There are 12 cranial nerves (all synapse on nuclei in brain)
-some of these cranial nerves are sensory, motor, or mixed (sensory and motor)

Question 37

Name each cranial nerve, its function and type

Answer 37

Cranial nerve Nerve Type Functions
1. Olfactory Sensory Smell
2. Optic Sensory Vision
3. Oculomotor Motor Eye Movement (cross eye)
4. Trochlear Motor Eye Movement
5. Trigeminal- Fine touch, temperature, pain, chewing
Ophthalmic Branch Sensory
Maxillary Branch. Sensory
Mandibular Branch Mixed
6. Abducens Motor Eye Movement
7. Facial Mixed. Sense of Taste, Saliva and Tear Secretion, Movement of facial muscles
8. Vestibulocochlear -
Cochlear Sensory Hearing (Auditory Nerve)
Vestibular Sensory. Maintaining Equilibrium of the Body
9. Glossopharyngeal Mixed Swallowing and Secretion of Saliva, Taste
10. Vagus Mixed. Parasympathetic Sensation, Control of Smooth Muscles of Lungs, Viscera. Monitors Blood pressure, Levels of O2 and CO2
11. Accessory Motor Swallowing, Movement of Head and Shoulders
12 Hypoglossal Motor Tongue Movement, Speech and swallowing

Question 38

Discuss the trigeminal nerve and the three branches it has

Answer 38

Trigeminal nerve has 3 branches:
1. Mandibular Division: as it enters and exits trigeminal nerve, it forms mandibular nerve and innervates the mandible
2. Maxillary nerve- underneath the eye
3. Opthalamic nerve- above Maxillary nerve
all three nerves through trigeminal ganglion, will synapse on trigeminal nerve nuclei

Question 39

Describe the pyramidal decussation that occurs in the medulla. Distinguish what occurs in Closed vs Open portion of medulla

Answer 39

Medulla- extension of the spinal cord
-Closed part of Medulla: dorsal columns begin to synapse on Nucleus gracillis and Nucleus cuneata; also decussation of descending motor fibers or DECUSSATION OF PYRAMIDS (motor fibers from the medullary pyramids cross the midline)

-axons coming in through dorsal column will synapse first in Nucleus cuneata and gracillus. Those neurons send fibers that will cross at this level, ascend though medial lemniscus into thalamus (seen better in open portion of medulla)

-Open part of Medulla- cerebral canal opens up into fourth ventricle at this point
At open part, you see other structures:
inferior Olivary nucleus (involved in motor coordination, source of climbing fibers to cerebellum, and involved in voluntary movement)
*Trigeminal Nerve Nucleus and Spinal tract
-cranial nerve V- Spinal nucleus
-cranial nerve V- Spinal tract
-also see vagal, hypoglossal, vestibular and trigemninal nuclei (lots of cranial nerves snyapse in medulla)

Question 40

Where do most of the cranial nerves have their first synapse?

Answer 40

Most cranial nerves have first synapse in the MEDULLA (open part)

Question 41

What occurs in the pons and how is it related to cerebellum and medulla?
What structures are found in pons?

Answer 41

Pons is connected to middle part of cerebellum called middle peduncle (tract of fibers from Pons into cerebellum)
many of same pathways present in medulla are present in pons such as medial lemniscus tract, Medial longitudinal fasciciulus ( contain oculomotor nerve, trochlear nerve and abducens nerve), and 5th cranial nerve nuclei, motor nucleus, sensory nuclei, spinal portions of nuclei)
-Locus ceruleus- next to cranial nerve 5
this anatomy used to help find different things in the dark (that are a mile away)
- reticular activating system nuclei

Question 42

What is the Reticular activation system composed of?

Answer 42

Reticular activating system- (in Pons) contains serotonergic Nuclei of Raphe, and Cholinergic reticuluar formation (gigantocellular neurons of reticular formation, ACh), and Locus ceruleus (NE)

Question 43

What structures are the midbrain and what are their roles?

Answer 43

Midbrain: Substantial Niagra (Dopaminergic neurons)
-slice midbrain, you can see different regions: inferior caliculus(auditory processing)
*Superior caliculus (Visual area involved in psychotic movements; fast jumps of your eye, regulate smooth movement, fixation eye movements, Vergence (Move both eyes simultaneously; cross-eyed)
most Dorsal part of Midbrain: **Tectum
Most Ventral part of Midbrain: **Tegmentum
** Peri acqueductal gray (PAG) - pain process
**Cirus cerebri (aka cerebral periduncle) - major pathway of motor neurons to get out of cortex

Question 44

What are the major lobes found in forebrain of cerebral cortex and what are their functions?

Answer 44

Forebrain:
1) Frontal Lobe:
-MOTOR CORTEX- plans and executes voluntary movements
-BASAL GANGLIA- smoothes movements
-Broca’s area- controls speech
-Prefrontal cortex- planning, impulse control

2) Parietal Lobe:
- *Somatosensory Cortex- protection area for body senses
Association cortex- location of body and objects in space

3) Temporal Lobes:
-AUDITORY CORTEX- Auditory information
-Wernicke’s area- Language area- meaning
-Inferior temporal cortex- visual identification of objects

4) Occipital Lobes
-PRIMARY Visual Cortex : Projection area for visual information
Visual association cortex: Processes components of visual information

Question 45

What are the characteristics and differences of the two brain hemispheres right and left )

Answer 45

Brain hemispheres have different functions
-Left and right hemispheres control the OPPOSITE parts of the body (right, and left, respectively)
right brain hemisphere controls left side of body
-Speech processing centers (Broca’s area and Wernicke’s) are located on the left hemispheres

Question 46

How are high cognitive functions controlled in the brain?

Answer 46

High Cognitive functions are controlled ASYMMETRICALLY
Left Brain- logic, Analysis, mathematics, language, facts, think in words.
right brain - (Affective related in prefrontal cortex , rhythm processing in music, creativity, imagination, intuition, feelings, visualizations, arts
there is a bias for different functions in both brain regions

Question 47

Where is the frontal lobe located in the brain? What are its characteristics ?

Answer 47

Frontal Lobe located in front of central sulcus and above the Sylvian (lateral) sulcus
Frontal lobe- planning, organization, problem solving, memory, attention, decision making, abstract thinking, complex behavior and emotions; fine control of the movement (primary motor cortex- pre central gyrus)
inferior frontal gyrus- Supplemental motor area, initiation and sequence of movements
-Prefrontal cortex- intellectual and emotional events

Question 48

What is Broca’s Aphasia?

Answer 48

Broca’s Aphasia- when you have difficulty with speech production ( you know what you want to say, but hard time verbalizing it) ex: you. notice a red thing on a tree (hard time saying apple)
broca’s - production of language

Question 49

What is the Insula and what are its functions?

Answer 49

Insula (island of rhile) : has broad role of interception; sense of physical condition body (ex; how am I doing, how am I feeling)
-also involved in Pain and taste sensation
-sensorimotor pain, social and emotional processing and decision making
Insula located in coronal section of brain

Question 50

What is the role of the Amygdala?

Answer 50

Amygdala: involved in emotional processing (both fear, and positive emotions

Question 51

What are the major roles of the Parietal Lobe, Temporal and Occipital Lobes?

Answer 51

Parietal Lobe: Integrate sensory inputs from various parts of the body tactile, pain), including orientation in space (together with cerebellum). Primary somatosensory cortex- postcentral gyrus
Temporal Lobe- recognizing and processing sounds, Understanding and producing speech
Occipital Lobe- receiving and processing visual information (visual cortex)

Question 52

differentiate between the Broca’s area and Wernicke’s area

Answer 52

Broca’s motor speech area: production of speech
Wernicke’s area- recognition of speech
(association of sound and rhymes)

Question 53

What kind of structures can you see on sagittal section of brain and what are their functions?

Answer 53

Sagittal Section:
Corpus Callosum- connects cerebral hemispheres
Cingulate gyrus- emotions, learning, instincts,
Septum pellucidum- separates lateral ventricles

Question 54

Discuss the feedback circuit that occurs between cerebral cortex and basal ganglia and other structures in the brain

Answer 54

Feedback circuit:
feedback loop for information to be computed, trying to generate movement, you will go to motor cortex which will send information to basal ganglia about movement (tell body, I want to move). Basal ganglia will send this information to thalamus to talk to primary Motor cortex. if there is any update, sensory info will come back to basal ganglia so it can update it. Basal ganglia interconnected with many other brain regions
interconnections throughout brain (not just one single circuit)

Question 55

What is the role of the primary motor cortex, prefrontal cortex, and primary associative cortex? what is the basal ganglia?

Answer 55

Primary motor cortex: constantly send excitatory signals to the lower motor neurons, If not dampened by voluntary control, these signals can cause an uncontrolled movement of the muscles (dyskinesia) that may be observed in the course of Parkinson’s disease
Prefrontal cortex (PfC) and primary associative cortex (PAC) control the primary Motor cortex though the BASAL GANGLIA, a complex that involves a number of nuclei

Question 56

What is the major brain region involved that affects Parkinson’s disease? What is Dyskinesia?

Answer 56

The Primary motor cortex affects Parkinson’s Disease
-Dyskinesia- is the uncontrolled movement of muscles, that can be observed in Parkinson’s disease (if primary motor cortex not controlled properly)

Question 57

Which brain regions are involved in the planning and execution of body movements?

Answer 57

PAC, FC, PfC, are involved in the PLANNING process (using a compilation of memory, experience, visual and auditory signals) in a decision to make a move.
The Primary motor cortex is involved in the EXECUTION of movement (of spinal cord)

Question 58

Explain why Primary motor cortex is a cortical area and how it affects the brain? What is Cortical homunculus?

Answer 58

Primary motor cortex - is a cortical area, called cortical motor homunculus
The homunculus: Size of body part relates to how many neurons control muscle group or particular area in the body
This was later discovered since primary Motor cortex underwent electrical stimulation in trans, (during open surgery), and the patient will move muscles regardless of his or her will

hence, there is Somatopoic organization in brain regions (thalamus, spinal cord, precentral gyrus, Nucleus gracillis and cuneata)

Question 59

What are the major functions of Cerebral cortices?

Answer 59

Cerebral cortices
1) Fine perception of complex, visual, auditory and tactile signals and their compilation (ex: primary somatosensory cortex, visual cortex)
2. Fine control of the movement (primary motor cortex)
3. Associative and abstract memory, conscious control, intellect and high cognitive functions (frontal and prefrontal cortices)
4. Verbal, speech and language recognition (Wernicke’s and Broca’s areas)

Question 60

What is the role of the cerebellum?

Answer 60

Cerebellum;
1) Balance and coordination of complex movemnts
(also coordination of cognitive thought)

Question 61

what are the main roles of Brain stem?

Answer 61

Brain stem:
1) Primordial instincts and emotions (limbic system)
2. Motivation and addiction (basal ganglia; dopamine, VTA)
3. Control of the motor output (basal ganglia)
4. Autonomous control of respiratory, cardiovascular and digestive functions (NE, E)
5. Sorting and transmission of the information to the spinal cord

Question 62

Discuss the components of sensory system and how they are interconnected

Answer 62

You have an environment (that you need to take information from) will become a sensation, and we will perceive it in different ways. We then you that information to make a decision, which generates an action
The action will then impact the environment around you.
The brain has the interconnected system to keep you alive.

Question 63

Define the terms sensory receptors, sensation and perception

Answer 63

Sensory receptors: specialized cells (like auditory cell) or multicellular structures that collect information from the environment
-these receptors send impulses to the brain
Sensation: a feeling that occurs when brain becomes aware of sensory impulse
-you then take the sensation and have perception of it (ex: how I hear violin)
Perception: a person’s view of the stimulus; the way the brain interprets the information

Question 64

What is the Sensory pathway for integrating and perceiving information?

Answer 64

Sensory Pathway:
Stimulus –> Sensory receptor (= transducer) —> Afferent sensory neurons—> CNS—> Integration and perception

Question 65

What are the different receptor types and what are their functions?

Answer 65

Receptor Types:
1) Chemoreceptors- respond to changes in chemical concentrations (ex; taste)
2) Pain receptors (nociceptors) - respond to tissue damage
3) Thermoreceptors- repsond to changes in temperature
4) mechanoreceptors - respond to changes in mechanical forces (ex; stretch receptors)
5) Photoreceptors (respond to light)
6) Osmoreceptors (respond to changes in solute concentration) (ex: pH, O2 and CO2 levels)

Question 66

What is somatosensation and what are the 3 main groups ?

Answer 66

General Somatosensation: describes senses that are associated with skin, muscles, joints and viscera
Three groups;
-Exteroceptive tissues (exteroceptors): senses associated with body surface such as touch, pressure, temperature and brain
-Visceroceptive senses (interoceptors) : senses associated with changes in the viscera such as blood pressure stretching blood vessels and ingestion of the meal
Proprioreceptive senses; senses associated with changes in muscles and tendons such as at joints (ex: how you’re standing, arm is up)

Question 67

Describe the 4 stimulus properties that the CNS (central nervous system) distinguishes

Answer 67

CNS Distinguishes 4 Stimulus Properties:
1) Modality (nature) of stimulus
-type of receptor (ex: taste, auditory)
2) Intensity (how loud?)
3) Duration (how long?)
4) Location
-Lateral inhibition and Population coding mechanisms is what the brain uses to help determine location and other properties of sensory stimuli

Question 68

Discuss the somatosensory receptor and their components

Answer 68

Somatosensory Receptors:
1) Mechanoreceptors
-hair follicle (virbrissa) receptors
-FINE TOUCH
Meissner’s Corpuscles
Merkel’s disks
-Deep Transient Pressure and High Frequency Vibration
Pacininan corpuscles
-Skin Stretch and Deformation within joints
Ruffini’s endings
-Muscle Stretch
Intrafusal fiber:
Annulospiral endings, flower-spray endings, Golgi-tendon 1b fiber (patellar fiber)
2) Temperature
-Krause and Bulbs (cold)
3) Nociceptors
-Free nerve endings
-

Question 69

Describe the types of stimuli involved in Nociception, along with its functions, and different pathways that are activated.

Answer 69

Nociception:
-Free dendritic endings
-Activation strong Noxious stimuli-
3 categories of the stimuli:
-Mechanical
-Thermal (menthol and cold/capsaicin and hot)
-Chemical (includes chemicals from injured tissues)
-Inflammatory pain
May activate 2 different pathways:
-Reflexive protective- integrated in spinal cord
-Ascending to cortex (pain or pruritis -> itch)

Question 70

Discuss the different receptors involved in receptor transaction and their features. How does a specialize receptor cell function?

Answer 70

Receptor Transduction: composes of stimulus that will bind to different kinds of receptos:
-Simple neural receptor; containing free nerve endings, unmyelinated axon and cell body
-Complex Neural receptor- contains layers of connective tissue, myelinated axon, cell body
-Special Senses receptor: containing synapse, sensory neuron and cell body

Receptor is part of neuron–> Action potential triggered if potential is above threshold
Specialized receptor cell–> the amount of Neurotransmitters released determines stimulus strength

Question 71

What is the mechanism of mechanotranduction? Where does this process occur?

Answer 71

Mechanism of Mechanotranduction: Pacian Corpuscle
Detects vibration
There is an A beta fiber that contains concentric layers of myelin and protection that wrap around and around the fiber
1) When there is Deformation, at frequency vibrating back and forth, an action potential is generated through sodium potassium changes
2) EPSP generates AP at first node of Ranvier (initial segment
3) AP propagates down axon to dorsal root up into spinal cord
molecules mediating mechanotransduction in pacian corpuscle are really unknown.

Question 72

Discuss the process of sensory transduction in a muscle and what receptor is involved.

Answer 72

Sensory transduction (mechanoreceptor in a muscle)
-if you have a fiber, the way it communicates its intensity, is though its number of action potentials
Ex: a mechanoreceptor in muscle:
If you stretch muscle a little it, generates a few spikes
-stretch muscle a lot- generate a lot more action potentials
Action potentials: all or none phenomenon (either they are firing or not firing)
you can encode Duration of Action potential: by how long the thing is spiking or generating action potentials
Pattern is important with AP’s : at beginning of stimulus, AP fires rapidly , whereas towards the end, the AP fires more slowlly (since it encodes its duration of stretch)

Question 73

eExplain what can be done to get more axons to fire action potential and the concept of Recruitment of receptors.

Answer 73

if we activate more and more receptors (as we touch skin, or hear louder and louder tone), we can get more and more axons to fire Action potentials
Recruitment of receptors, ; when you keep adding more neighbors or a combination of receptors together to create a message
-more pressure- recruit receptors

Question 74

Discuss the differences between a single sensory unit stimulated vs multiple sensory units stimulated and how it relates to recruitment of receptors

Answer 74

Single Sensory Unit:
a weak stimulus will have a few receptors to fire a little bit of Action potentials (slower rate)
However a strong stimulus will have neurons send more receptors to be activated and allow for a FASTER FIRING of AP’s
Multiple sensory units:
a weak stimulus, will have few receptors as well leading to some firing of AP’s
-A strong stimulus and multiple sensory units will activate many neurons at at the same time to fire lots and lots of AP’s
- the three neurons will generate AP’s at the same time and another secondary neuron will collect that information and give a read out as to how population of primary neurons respond
-amplification by single neuron or by multiple neurons is called amplification and corresponds to recruitment

Question 75

What kind of receptors are involved in Touch? Describe the different fields involved in touch.

Answer 75

Touch;
MECHANORECPTORS
-small and large receptive fields
Meissner’s corpuscle;
small receptive field where you are innervation a number go regions in a small area of skin (on fingers, or palm)
Pacinian corpuscle : large receptive field ; higher number of receptors neurons innervate a large area of hand

Question 76

Which parts of the brain contain small receptive fields for for touch and how do they differ ? What kind of touch is this and where are these receptors located in the body?

Answer 76

FINE Touch:
-Small Receptive Fields:
**Meissner’s corpuscles (RAPIDLY adapting)
-distinguish between two points on the skin
-receptor can tell you about edges
**Merkel’s discs (Slowly adapting)
-Localize touch and determine texture
(tell you about how big edge)
-These receptors are numerous in the DISTAL than the Proximal parts of the body (more abundant in hairless portions of the body- skin and lips)
-( fire continuously )

Question 77

Describe the parts of the brain that contain Large receptive fields for touch and how they differ? What kind of touch for large receptive fields?

Answer 77

CRUDE Touch
-Large receptive Fields (one neuron innervates large patch of skin)
**Pacininan corpuscles (RAPIDLY adapting)
subcutaneous, tendons, and ligaments
-heavy pressure and vibrations ‘
(fire at onset and offset of stimuli)
**Ruffini’s endings (slowly adapting)
seen in joint capsules
( fire throughout due to magnitude of change)

Question 78

Why is receptor size important?

Answer 78

receptive field size- tell us where AP happened and get richer sense of environment due to fine and crude touch that encode different properties of somatosensation

Question 79

What encodes the intensity and duration of stimulus?
What does sustained stimulation lead to?

Answer 79

Intensity and Duration of stimulus;
Intensity- coded by NUMBER Of receptors activated and frequency of AP coming from receptor
Duration; coded by duration of AP’s in sensory neurons
sustained stimulation leads to ADAPTATION (neuron gets used to stimulus)
-Tonic receptors - (encoding how much)
-Phasic receptors- (edges and dynamic changes)

Question 80

What are the two major Sensory pathways and their components. How are these transmitters?

Answer 80

Fine touch Pathway
-transmitted by Dorsal Column- Medial Leminiscus System (brain stem)
components;
fine touch
Vibration
Position
Pressure

Crude Touch Pathway
-transmitted by Anterolateral system
components:
Crude touch
pain
temperature
tickle and itch

Question 81

Discuss the classification of Nerve fibers for A, B and C fibers and their features.

Answer 81

Nerve Fiber Classification
A fibers; Myelinated
Subtypes; alpha, beta, gamma,delta (some overlap in ranges)
side note; alpha (proprioreceptor of skeletal muscles, beta (mechanoreceptor of skin; 6-12 um) Delta (pain and temperature)
-Fastest conducting and largest diameter (20 um)
B fibers: Slower myelinated
C fibers: UN Myelinated
-Slower conducting than A fibers and smallest diameter (0.5-2 m/sec, 0.5 um)
These fibers are so slow due to having no myelin (can’t jump node to node)

Question 82

Discuss how Sensory Axons enter the CNS, including the roles of each nerve fiber. What are the division of spinal gray matter? What are the two systems that run through CNS?

Answer 82

Sensory Axons Enter CNS:
Spinal cord
-Divisions of spinal gray matter:
-Dorsal horn
-Intermediate zone
-Ventral horn
1) Myelinated ABeta axons (touch-sensitive)
-Enter as Dorsal root (immediately)
-Ascend to brain through dorsal columns
Abeta and Adult fibers mediate pain
-Fast (Adelta fibers) pain is sharp
C fibers mediate pruritus (itch)
-Slow pain (C) is throbbing

two main systems are the Alpha Beta axons that go straight to Dorsal root, dorsal columns
and other fibers synapse at laminal I-IV (Alpha delta fibers and C fibers)

Question 83

***Discuss the pathway of nerve fibers for Fine touch

Answer 83

Fine touch:
A beta fibers from fine touch corpuscles come in, immediately ascend through dorsal column, cuneatus, and gracile tracts. That information makes its first synapse in MEDULLA in the Nucleus gracilis and Nucleus Cuneate
Once made synapse in medulla, the secondary neuron sends axon that desiccates (crosses) the midline ( near Medial Leminiscus) and ascends through tract into Thalamus
Once synapse in thalamus it goes to central cerebral cortex and ends up in somatosensory cortex.
1st synapse: medulla
second synapse: thalamus

Question 84

**Where does the decussation (crossing midline) from Fine touch occur? What happens after that?

Answer 84

Nucleus Cuneate and Nucleus gracilis (where it makes its first synapse in medulla)
then desiccates and ascends through medial leminsicus on contralateral side
-motor neurons activating muscles also decussate this region
(sensory and motor info decussate (cross) in region of medulla; med lem)

Question 85

How does Pain Pathway compare to Fine Touch Pathway.

Answer 85

Pain pathways- pain sensation fibers transmitted : A Delta fibers and C fibers will synapse on Lamina I-IV in dorsal horn. These sensory neurons will send axons that desiccate (cross) at level of spinal segment and ascend through anterolateral system of ascending tracts on contralateral side through either Paleospinalthoalmic tract (Slow pain) or into Neospinothalamic tract (fast pain; Alpha Delta) and into thalamus, then cortex.

Fine touch pathway: Alpha fibers go straight through dorsal–> gracilis/cuneate into medulla (first synapse)—> Nucleus gracilis,/cuneate—> decussation at midline for medial lemniscus and synapse at thalamus–> cerebral cortex

Question 86

What is refereed pain and how does it occur?

Answer 86

Referred pain: when pain in organs is poorly localized
ex; someone has heart attack, but complains arm hurts
Referred pain occurs if:
Multiple primary sensory neurons converge on single ascending tract

pain organs: afferents poorly organized. neurons stay in lamina I-IV
ex: painful stimulus of skin that synapse on neuron
Pain in viscera is uncommon; pain sensors and axons will synapse on same neuron that a patch of skin would synapse (hijacks it) brain cannot tell which of two fibers are activated with pain.

Question 87

What is the role of somatic senses in fine touch vs Fast pain (alpha delta) ?

Answer 87

Somatic Senses:
Fine Touch
-Primary sensory neurons from receptor to MEDULLA
-secondary sensory neurons always cross over from medulla–> thalamus
Tertiary sensory neurons –> Somatosensory cortex (post central gyrus)

Fast Pain (alpha Delta fibers)
-Primary sensory neurons from receptor to SPINAL CORD (laminae II and V of the Dorsal Horn)
secondary sensory neuron: always cross over in Spinal Cord to THALAMUS
Tertiary sensory neuron —>somatosensory cortex (post central gyrus)

process; fine touch (ascend dorsal column–>medulla–>thalamus–>cortex
-Fast Pain (Adelta) : desiccate–> ascend contralateral side of thalamus–> cortex

Question 88

what happens with the trigemninal nerve?

Answer 88

Trigeminal nerve- info comes in through the spinal tract into main sensory nucleus to first synapse there, Then it decussates and ascends into thalamus (through
trigeminal lemniscius and trigmenial thalamic tract)

Question 89

Where is somatopic organization occurring in the brain and for which pathways? where in the brain is the homunculus organized?

Answer 89

Homunculus and somatotopic organization for fine touch are organized in thalamus, nucleus cuneatus/gracillius and organized across spinal cords in those tracts (same for fine touch, anterolateral and Motor pathway)
***The Somatic organization (homunculus also occurs) also applies for fine touch, anterolateral pathway (pain) and Motor activity and their pathways.
homunculus for cortex: used for both sensory and motor information .

Question 90

Describe the role of the Cortical Somatotopy (Homunculus) in the Somatosensory Cortex?

Answer 90

Somatosensory Cortex
-Cortical Somatotopy (homunculus) : represents the landscape or number of neurons dedicated to encoding Fine touch in hands, lips and touch

in these areas, more neurons encode somatosensory information to do better 2 point discrimination (determine where an object is better localized on skin)
finest 2 point discrimination on finger types to protect and perceive different textures of objects.

Question 91

Distinguish between the different areas in somatorsenroy cortex and discuss each role . What is role for Area 1 vs Area 2?

Answer 91

Somatosensory Cortex
-Primary somatosensory cortex (S1) = Brodmann’s Area 3b
Adjacent areas:
-Postcentral gyrus:
3a, 1, 2
-posterior parietal cortex:
5, 7
area 1: sense texture of object
area 2: perceive shape and size of object; more involved with proprioreceptoin

although you get same info into 3b, that is processed to other ares with different neural network structures to extract different features from initial sensory info
Once 3b 1 and 2 are done with extraction and processing, they are then transmitted through cortical areas 5 7
(change from knowing if it is an edge on object, to what actual object is)

areas 1, 2, 5, 7: building of small pieces of sensory phenomenon into something you can understand as an object.

Question 92

Describe the Cortex Architecture. How many layers does neocortex have? What are its characteristics?

Answer 92

Cortex Architecture
-different stains (*Golgi stain (big pyramid neurons) *Nissle stain (big neurons, and small neurons); *Weigert stain (stain fibers; afferent come up from thalamus into regions, horizontal fibers)
*The neocortex has SIX layers
(each layer has the role of extracting APs into something that one can sense and perceive.
-Extremely complex
-repeated motifs
-Well organized

Question 93

Discuss the columnar organization of neocortex? Who discovered this concept?

Answer 93

Vernon Mountcastle talked about cortical columns in a newspaper review
in cortex, there are are processing units: you can
count 30 cells in a column
the column extracts one thing from sensory world and columns are linked together
each fibrisae- has hair cell receptors; somatopy of virbraise pad represented thought CNS
-barrel shaped objects called barrels (in rat cortex) that relate to whisker
in barrel column: that processes information from one particular whisker (delineation work across cortex)
use visual cortex of cortical columns; individual columns might process and favor movement in different directions (ex: left, northeast, west, etc)
cortex: we directional receptive fields and colors seen .
cortical columns: basic building blocks of the way brain works

Question 94

What are cortical connections and why are they important?

Answer 94

Cortical connections: the process of somatosensory information traveling up VPL thalamus and arriving at Layer 4 (third synapse of layer 4 neurons) those neurons make a synapse on layer 2. Cell bodies are on layer 3. These neurons send projections back down yo to thalamus. Layer 4 neurons will also synapse on Layer 5 neurons which send information to other brain regions

-Hence information flows through circuit into layer 4, up to 2, 3 down to 5 and 6

Question 95

What is the role of the lateral fibers in cortex? what occurs during Neural coding?

Answer 95

Lateral fibers running throughout cortex at each layer At, each layer, there is a dense interconnect between cortical columns. These interconnects are important for receptive fields.
Neural coding:
you touch receptive field and neuron fires, which activate preferential pathway and activate specific cortical column.
As stimulus gets greater, higher probably of activating neighboring cortical columns (as stimulus gets stronger and stronger)
This amplification and recruitment are decoded as how strong that information was.

Question 96

How do interconnects try to shut off their neighboring column? Why does this occur?

Answer 96

interconnects between cortical column, allows one column to shut off its neighboring column.
information is coming up from pathway 1, these columns will be preferentially activated, but will send information to other columns to shut everything else off (by making Peak in graph as sharp as possible)
neighboring neuron doing the same thing will clarify and differentiate two peaks in graphs (if preferential column tries to shut off other column)
This provides clear separation of peaks (to determine 2 point discrimation or determine where an edge is)
allow the ability shape receptive fields and differentiate two places in space

Question 97

What are the two different ascending sensory pathways and how do they differ?

Answer 97

Classical systems;
-the Number of nuclei is DIFFERENT in different sensory systems
-Use VENTRAL thalamic nuclei that project to Primary sensory cortices
-neurons processes only input from ONE sensory modality

Non-classical systems
-Use DORSAL and MEDIAL thalamic nuclei that project to SECONDARY cortices and other parts of the CNS
-Receive input from MORE than one sense
ex; receive information from 2 different sensory receptors (2 different corpuscles )

Question 98

Describe examples of both classical pathways and Non-classical pathways

Answer 98

Non-classical pathway (ex: pain pathways); Usually sensory input is suppose to go to dorsal thalamus (like in classical) , but also sends fibers to reticular formation (like locus cerrelus to create AROUSAL signal, wake animal up) and from thalamus it normally goes straight to SI cortex, BUT it can also go to Limbic system, Association cortex and secondary somatosensory system (SII). This variations of classical pathways seen in this pathway allows us much more Complex associations and perceptions of our environment.
“Rat somatosensory pathway: info comes up Dorsal column–>reticular formation–> medial lemniscus to thalamus and goes to primary somatosensory cortex. This pathway encodes, “WHERE” something happened in space, and how much it did.

Classical pathways;
Sensory info from skin receptors moved though dorsal column, decussate (cross midline) and go through VPL to primary somatosensory cortex (SI)

Question 99

Differentiate between the Non-classical pathway that goes to Limbic system, association cortex , SII and the rat somatosensory pathway (SI)

Answer 99

*Rat somatosensory pathway: info comes up Dorsal column–>reticular formation–> medial lemniscus to thalamus and goes to primary somatosensory cortex (SI) . This pathway encodes, “WHERE” something happened in space, and how much it did.
*Non classical pathways; encodes more information about “WHAT” happened; like textures and more rich information

These pathways show how different they are and how they can be used together

Question 100

Describe the connections seen in the Visual cortex

Answer 100

Connections of the Visual Cortex:
connections
-Primary Visual Cortex (V1)
-Input from LGN
-Output to all other levels
Secondary Visual Cortex (V2)
-Output to all other Levels
-After V2:
-output to the parietal lobe- Dorsal stream
-output to the inferior temporal lobe- Ventral Stream
-Output to superior temporal sulcus (STS) - STS stream
***Visual information will comine in and initially end up in V1 (primary visual cortex). This information will then be processed in occipital lobe and go through secondary visual cortices V2, V3 and V4. Once information reaches these cortices, it will be processed into 1 of 2 pathways: either into dorsal stream to parietal lobe (for visual guidance of movements; “WHERE” or Ventral stream (in temporal lobe, for object perception for knowing “WHAT” object is present) It can also go to STS (superior temporal stream) which in involved in visuospatial functions like biological movement.

Question 101

what are the roles of Doral stream, Ventral stream and STS (Superior temporal stream) of Visual cortex?

Answer 101

Dorsal stream: Visual guidance of movements
Ventral stream: Object perception
STS (superior temporal stream ): visuospatial functions (bio movement)

Question 102

Where does cortical processes end up after primary sensory cortices?
Where do information from different sensory systems being combined occur?

Answer 102

after goes sensory information goes through secondary processes (V1-V4), it ends up in association areas l like PREFRONTAL CORTEX to allow you to build behaviors off of what you perceive in world around you .
starts with sensory info coming in–> sensation–> perception to secondary cortices–> become information to generate behavior in high cortices (like cortex)

integration of input from different sensory systems occurs in ASSOCATION CORTICES

Question 103

what are disorders of the sensory systems?

Answer 103

Disorders of Sensory systems:
-impaired conduction of physical stimulus to receptors
-Impaired functions of receptors
-Impaired function of sensory nerves (ex: hearing loss)
-Impaired or changed function of central nervous system