Physiology - Comp Exam

Question 1

Answer 1

A. Sodium

Question 2

Answer 2

D. Axon

Question 3

Answer 3

A. A band

Question 4

Answer 4

C. Cells are mononucleated.

Question 5

Answer 5

D. 120°

Question 6

Answer 6

D. AV block

Question 7

Answer 7

A. Tachycardia

Question 8

Answer 8

C. Veins

Question 9

Answer 9

D. 0 liters per minute

Question 10

Answer 10

B. 60%

Question 11

Answer 11

A. 25% or 22%

Question 12

Answer 12

B. Primary active transport

Question 13

Answer 13

C. Large diameter, myelinated

Question 14

Answer 14

C. T tubules

Question 15

Answer 15

C. An end-plate potential is created on the muscle fiber.

Question 16

Answer 16

D. P

Question 17

GFR is determined by the net filtration pressure and the glomerular capillary filtration coefficient. Which of the following factors has the greatest effect on increasing GFR?

A. Glomerular capillary colloid osmotic pressure

B. Bowman’s capsule hydrostatic pressure

C. Bowman’s capsule colloid osmotic pressure

D. Glomerular hydrostatic pressure

Answer 17

D. Glomerular hydrostatic pressure

Question 18

Which of the following, in liters/day, represents the GFR in the average adult human?

A. 3

B. 125

C. 180

D. 360

Answer 18

C. 180

Question 19

Aldosterone is an important regulator of sodium reabsorption and potassium secretion; one of its main targets is…?

A. Podocytes

B. Principal cells

C. Intercalated cells

D. Cells of macula densa

Answer 19

B. Principal cells

Question 20

Which of the following cells play a major role in the secretion of potassium?

A. Intercalated cells

B. Principal cells

C. Chief cells

D. Podocytes

Answer 20

B. Principal cells

Question 21

Which of the following plays a major role in stimulating potassium excretion by the kidney tubules?

A. Aldosterone

B. Angiotensin II

C. Sodium ion

D. PTH

Answer 21

A. Aldosterone

Question 22

Which of the following buffer systems is most important in buffering renal tubular fluid?

A. Phosphate buffer system

B. Carbonate buffer system

C. Bicarbonate buffer system

D. Hemoglobin buffer system

Answer 22

A. Phosphate buffer system

Question 23

Respiratory alkalosis due to a decrease in carbon dioxide concentration caused by hyperventilation is compensated for by which of the following mechanisms?

A. Increased ventilation rate.

B. Decreased ventilation rate.

C. Renal excretion of bicarbonate ion.

D. Renal addition of new bicarbonate ion to extracellular fluid.

Answer 23

C. Renal excretion of bicarbonate ion.

Question 24

Answer 24

B. It decreases the partial pressure of each of the other gases.

Question 25

Answer 25

B. Secondary active transport via a sodium/glucose cotransporter

Question 26

Answer 26

B. Pneumotaxic center

Question 27

Answer 27

A. Dorsal respiratory group

Question 28

Answer 28

A. Proximal convoluted tubule

Question 29

Answer 29

B. Secondary (second order) neurons

Question 30

Answer 30

D. Y type ganglion cells

Question 31

Answer 31

Question 32

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Question 33

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Question 34

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B. Diencephalon

Question 35

Answer 35

B. Central sulcus

Question 36

Answer 36

B. 50 percent

Question 37

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Question 67

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Question 68

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Question 69

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Question 70

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Question 71

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Question 72

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Question 73

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Question 74

How is gain calculated?

Answer 74

Gain = correction / error

Example: Blood is added to an uncontrolled system and to a controlled system:

• Uncontrolled: pressure rises from 100 to 175.
• Controlled: pressure rises from 100 to 125.

Controls changed pressure by -50 (correction), but the pressure still went up by 25 (error).

Gain = -50/25 = -2

Question 75

What is pre-load and how does it effect stroke volume?

Answer 75

Preload

• Pre-load is end-diastolic volume and is related to right atrial pressure.
• Increased pre-load:
  
  • Increased stroke volume
  • Increased width of pressure-volume loop

Question 76

Identify:

Answer 76

Question 77

Identify:

Answer 77

Question 78

What are the individual events associated with the sliding filament mechanism?

Answer 78

1. Arrival of action potential at terminal end of nerve fiber.
2. Opening of voltage-gated Ca²⁺ channels on nerve fiber ending.
3. Release of neurotransmitter (Ach) from synaptic vesicle into synaptic cleft.
4. Opening of ligand-gated sodium channels of sarcolemma.
5. Generation of action potential on sarcolemma.
6. Voltage-gated channels on T tubules (DHP - dihydropyridine - channels) interact with ryanodine receptors on SR membrane.
7. Opening of ryanodine-sensitive Ca²⁺ release channels.
8. Increase in Ca²⁺ concentration in cytosol.
9. Activation of sliding filament mechanism.
10. Released Ca²⁺ ions bind to troponin.
11. Tropomyosin uncovers myosin binding sites on actin.
12. ATPase heads of myosin molecules split ATP and bind to actin.
13. Stored energy in myosin head causes deformation such that thick and thin filaments slide past one another.
14. A second ATP binds to myosin and causes it to release actin.
15. Process is repeated over and over.
16. Contraction stops when ATP-dependent Ca²⁺ pump sequesters Ca²⁺ back into SR.

Question 79

What are dihydropyridine (DHP) receptors?

Answer 79

Dihydropyridine (DHP) receptors are voltage-sensitive L-type Ca²⁺ channels arranged in quadruplets that are located on the sarcolemma T-tubules. They cause a conformational change in the ryanodine receptors and release a very small amount of Ca²⁺ into the cytosol.

Question 80

Describe the fuction of the sarcolemma in the motor end plate.

Answer 80

Sarcolemma:

• Has Ach-gated ion channels:
  
  • 2 alpha, 1 beta, 1 gamma, 1 sigma protein
  • Tubular channel remains closed until 2 Ach molecules attach to its alpha subunits.
• Acetylcholinesterase - found on sarcolemma.

Question 81

How is an action potential transmitted at the motor end plate?

Answer 81

Transmission of an Action Potential

When action potential arrives at the terminus of the axon:

• Voltage-gated Ca²⁺ channels open.
  
  • Ca²⁺ ions are thought to draw synaptic vesicles closer to neurolemma next to the voltage gated Ca²⁺ channels.
• About 125 vesicles fuse to the neuronal membrane and empty contents into the synaptic cleft.
• 2 Ach molecules bind to each ligand-gated channel on the sarcolemma.
• Na⁺ and K⁺ pass through the channels (Na+ is more permeable).
• Principal effect is for large #’s of Na+ to pass through the muscle fiber, creating end-plate potential (50-75 mV), which initiates an action potential on the sarcolemma.

Question 82

How is the action potential on the sarcolemma transmitted to the muscle to cause a contraction?

Answer 82

Transmission of Action Potential

• Action potential on the sarcolemma continues down the T-tubules and activates voltage-gated dihydropyridine (DHP) channels.
• DHP channels activate ryanodine receptors (ryanodine-sensitive Ca²⁺ release channels) on the sarcoplasmic reticulum membranes, allowing Ca²⁺ to move quickly through the ryanodine receptors into the cytosol at the A-I boundaries.
  
  • Ryanodine receptor is also activated by the Ca²⁺ released into the cytosol, thus allowing more Ca²⁺ to be released.
• Ca²⁺ binds to troponin in the sarcomeres, resulting in the “sliding filament” mechanism.
  
  • High cystolic Ca²⁺ concentrations (after Ca²⁺ release from the sarcoplasmis reticulum) promotes ryanodine channel closure.

Question 83

Describe the ganglion cells of the retina.

Answer 83

Retina - Ganglion Cells

• Transmit signals from retina to brain.
• Axons make up optic nerves.
  
  • Only retina cells that transmit action potentials (others use electrotonic conduction which allows graded conduction of signal strength).
• An average of 60 rods and 2 cones converge on each ganglion cell and the optic nerve fiber from the ganglion cell.
• Approaching the fovea, fewer rods and cones converge on each optic fiber and rods and cones become more slender:
  
  • Increases visual acuity in central retina.
  • In central fovea there are only slender cones (~35,000) and no rods.
• The peripheral retina is more sensitive to weak light:
  
  • As many as 200 rods converge on a single optic fiber in the more peripheral regions of the retina.
• 3 types:
  
  • W
  • X
  • Y

Question 84

Describe the phases of cardiac muscle action potential.

Answer 84

Cardiac Muscle Action Potential - Phases

Question 86

What is automaticity and what cells exhibit automaticity?

Answer 86

Automaticity

• Gradual depolarization during phase 4, eventually reaching threshold.
  
  • Include SA and AV nodes and the Purkinje fibers.
  • SA node usually deploarizes more rapidly than the other tissues, reaching threshold first and, by default, becomes the normal “pacemaker” of the heart.
• Rate of depolarization determines the rhythmicity of the cell.
• Gradual depolarization during phase 4 is due to special Na⁺ channels which open in phase 3.

Question 87

What is vascular compliance?

Answer 87

Vascular Compliance

• Vascular compliance (capacitance) = increase in volume/increase in pressure.
• Tells us the total quantity of blood (ml) that can be stored in a given portion of the circulation for each mm Hg rise in pressure.
• Inversely proportional to elastance.
• Calculating compliance:
  
  • Compliance is equal to distensibility x volume.
  • VD = V_inc/(P_inc x V_orig)
  • VD x V_orig = V_inc/P_inc = Compliance

Question 89

Describe vascular compliance.

Answer 89

Vascular Compliance

• Compliance is a measure of the ease with which a hollow viscus may be distended; i.e., the volume change resulting from the application of a unit pressure differential between the inside and outside of the viscus; the reciprocal of elastance.
• Capacitance is directly proportional to volume and inversely proportional to pressure.
• Capacitance describes how volume changes in response to a change in pressure.
• Capacitance is much greater for veins than arteries.
• Capacitance of arteries decreases with age.
• Vascular compliance = total quantity of blood that can be stored in a given portion of the circulatory system.
• The greater the amount of elastic tissue in a blood vessel:
  
  • The higher the elastance.
  • The lower the compliance.

Question 90

Compare veinous compliance vs. arterial compliance.

Answer 90

Veinous vs. Arterial Compliance

• A systemic vein is about 8x as distensible as its corresponding artery and has a volume about 3x as great. How would its compliance compare to that of a corresponding artery?
  
  • When the arterial system contains 700ml of blood, the mean arterial pressure is 100 mm Hg. But when the arterial system contains 400ml of blood, the mean arterial pressure is 0 mm Hg.
  • The venous system contains a volume of blood ranging from 2000-3500ml. Removing several hundred ml from the normal venous volume only changes venous pressure 3-5mm Hg.

Question 91

What factors affect venous return to the heart from systemic circulation?

Answer 91

Factors that Affect Venous Return

• Pressure gradient for venous return = difference between the mean systemic filling pressure (MSFP) and the RA pressure.
• Venous return = (MSFP - RA pressure) / resistance to venous return
• RA pressure - impedes flow of blood from veins into RA:
  
  • Venous return -> 0 when RA pressure -> +7 mmHg = mean systemic filling pressure.
  • If RA pressure -> -2 mmHg, venous return reaches plateau, caused by collapse of veins entering chest.
• Degree of filling of systemic circulation:
  
  • When heart pumping stops, blood flow ceases.
  • Pressures everywhere in the body become equal:
    
    • = mean circulatory filling pressure.
      
      • =0 when blood volume = 4L
      • =7 when blood volume = 5L
    • Almost equal to mean systemic filling pressure.
• Mean systemic filling pressure (Psf) - forces systemic blood toward heart (pressure when a & v pressures come to equilibrium and circulation comes to a stop (=7mmHg).
• Resistance to blood flow:
  
  • 2/3 determined by venous resistance.
  • 1/3 determined by arteriolar and small artery resistance (mostly overcome by accumulation of blood).

Question 92

Describe the relationship between right atrial pressure and cardiac output.

Answer 92

CO vs. Right Atrial Pressure

• CO curve:
  
  • Depicts Frank-Starling relationship for the ventricle.
  • Shows that CO is a function of end-diastolic volume (note that as RA pressure increases, venous return decreases).
• Vascular function (venous return) curve:
  
  • Depicts the relationship between blood flow through the vascular system (or venous return) and the right atrial pressure.
  • Mean systemic filling pressure equals right atrial pressure when there is no flow and is measured when the heart is stopped experimentally.
• Point “A” - the equilibrium (steady state) point.

Question 93

What factors increase mean systemic filling pressure?

Answer 93

Mean Systemic Filling Pressure - Increase

• Increase in blood volume.
• Decrease in venous compliance.
• Results in:
  
  • Shift in vascular curve to the right.
  • Enhances filling of ventricles.

Question 94

Describe vascular elastance.

Answer 94

Vascular Elastance

• Elastance is a measure of the tendency of a hollow viscus to recoil toward its original dimensions upon removal of a distending or collapsing force.
• The greater the amount of elastic tissue in a blood vessel:
  
  • The higher the elastance.
  • The lower the compliance.

Question 95

What are the respiratory centers?

Answer 95

Respiratory Centers

• Dorsal respiratory group: DRG
• Ventral respiratory group: VRG
• Pontine respiratory group: PRG
• Botzinger complex: BotC
• Pre-Botzinger complex

Question 96

Describe the generation of the normal breathing rhythm.

Answer 96

Normal Breathing Rhythm - Generation

• Medullary respiratory centers:
  
  • These centers that initiate breathing are located in the reticular formation of the medulla. These centers include:
    
    • The dorsal respiratory group (DRG)
      
      • Located in the nucleus of the tractus solitarius.
    • The ventral respiratory group (VRG)
• Pontine respiratory centers:
  
  • The pontine respiratory centers include two areas located in the pons:
    
    • The apneustic center
    • The pneumotaxic center (=pontine respiratory group (PRG))

Question 98

Describe the ramp signal.

Answer 98

Ramp Signal

• The nervous signals transmitted to the inspiratory muscles (mainly diaphragm) during normal respiration:
  
  • Begin weakly.
  • Increase steadily for about 2 seconds.
  • Cease abruptly for about 3 seconds:
    
    • Allows for elastic recoil of lungs and chest wall to cause expiration.
• During heavy respiration:
  
  • Rate of increase of ramp signal increases rapidly.
• Usual method for controlling rate of respiration:
  
  • Controlling limiting point at which ramp suddenly ceases.
  • The earlier the ramp ceases, the shorter the duration of inspiration and expiration.
  • Thus, the primary function of the PRG (pneumotaxic center) is to control the “switch-off” point of the inspiratory ramp.
  • A strong PRG signal results in 30-40 breaths per minute.
  • A weak PRG signal results in 3-5 breaths per minute.

Question 99

Describe the pontine respiratory group (PRG).

Answer 99

Pontine Respiratory Group (PRG)

• Pneumotaxic center:
  
  • Located in the superior pons.
  • In the 1920’s, lesions of the PRG were found to also influence respiratory timing.
  • Specifically, lesions of the PRG result in the loss of the ability to turn off inspiration.
    
    • Without additional input from vagus nerves.
  • Mainly controls rate and depth of breathing.
  • Transmits signals to the inspiratory center (DRG).
• Apneustic center:
  
  • Located in the inferior pons.
  • Loss of function causes prolonged inspiratory gasping (apneuses).
  • Normal function may be to limit lung expansion.

Question 100

Describe the dorsal respiratory group (DRG).

Answer 100

Dorsal Respiratory Group (DRG)

• Located in the dorsal portion of the medulla.
• Sets basic rhythm of respiration.
• Most of the neurons are in the nucleus of the tract solitarius (NTS) and medulla reticular substance.
  
  • NTS is the sensory termination of both the vagal and glossopharyngeal nerves.
  • Receives information from:
    
    • Peripheral chemoreceptors
    • Baroreceptors
    • Several types of receptors in the lungs.
• Principal initiators of phrenic nerve activity.
• Receive many fibers from the ventral respiratory group (VRG).
• Receives lots of sensory information via the nucleus tractus solitarius.
• Mainly associated with inspiration (establishes ramp signal).

Question 101

Describe the functions of the premotor and supplementary motor cortex.

Answer 101

Premotor and Supplementary Motor Cortex - Functions

• Premotor and supplementary motor cortices generate a plan for movement.
  
  • Transfer plan to primary motor cortex.
• Signals generated here cause more complex patterns of movement than the more discrete pattern generated by the primary cortex.
• Anterior part of the premotor cortex develops a “motor image” of the total muscle movement that is to be performed.
• Supplementary motor cortex programs complex motor sequences and is responsible for mental rehearsal for a movement.
• Image in posterior motor cortex excites each successive pattern of muscle activity required to achieve the image.
• Posterior motor cortex sends signals to:
  
  • → Primary motor cortex
  • → Basal nuclei and thalamus → Primary motor cortex

Question 102

Describe the macula.

Answer 102

Macula

• The utricle and saccule each contain a macula.
• Each macula is covered by a gelatinous layer:
  
  • Contains large number of embedded small calcium carbonate crystals (statoconia).
  • Contains thousands of hair cells which project cilia into the gelatinous layer.
  • The weight of the statoconia bends cilia in the direction of gravitational pull.
• Hair cell:
  
  • Has 50-70 small cilia (stereocilia).
  • Has 1 large cilium (kinocilium) off set to one side.
  • Tips of stereocilia are connected together and to kinocilium.
  • Function:
    
    • Bending of stereocilia towards kinocilium opens hundreds of cation channels causing receptor membrane depolarization and excitation.
    • Bending of cilia in opposite direction closes channels and hyperpolarizes receptor membrane.
    • Hair cells are oriented such that bending the head in different directions causes different groups of hair cells to depolarize.

Question 103

Describe the response of a hair cell when a semicircular canal is stimulated by onset and then stopping of rotation.

Answer 103

Question 105

Describe the anatomical organization of the cerebellum.

Answer 105

Cerebellum - Anatomical Organization

• Two hemispheres separated by vermis:
  
  • Each hemisphere is divided into an intermediate zone and a lateral zone.
• Anatomically divided into three lobes (Anterior →Posterior):
  
  • Anterior lobe
  • Posterior lobe
  • Flocculonodular lobe
    
    • Associated with vestibular system.

Question 106

Describe the somatosensory projection areas of the cerebellar cortex.

Answer 106

Cerebellar Cortex - Somatosensory Projection Areas

• Vermis:
  
  • Location for control functions for muscle movements of the axial body, neck, shoulders, and hips.
• Intermediate zone:
  
  • Concerned with controlling muscle contractions in the distal portions of the upper and lower limbs, esp. hands, feet, fingers, and toes.
• Lateral zone:
  
  • Associated with cerebral cortex with planning of sequential motor movements.

Question 108

Describe the cerebellum.

Answer 108

Cerebellum

• Electrical excitation of the cerebellum does not cause any conscious sensation and rarely causes any motor movement.
• Removal of the cerebellum causes body movements to become highly abnormal.
• Functions:
  
  • The cerebellum plays major roles in the timing of motor activities and in rapid, smooth progression from one muscle movement to the next.
  • Not essential for locomotion.
  • Helps sequence motor activities.
  • Monitors and makes corrective adjustments to motor activities while they are being executed.
  • Compares actual movements with intended movements.
  • Aids cortex in planning next sequential movement.
  • Learns by its mistakes.
  • Functions with spinal cord to enhance the stretch reflex.
  • Functions with brain stem to make postural movements.
  • Functions with cerebral cortex to provide accessory motor functions.
  • Turns on antagonist at appropriate time.
  • Helps program muscle contraction in advance.
  • Functions mainly when muscle movements have to be rapid.

Question 110

What are the afferent tracts to the cerebellum?

Answer 110

Cerebellum - Afferent Tracts

• Corticopontocerebellar:
  
  • Motor and premotor cortices/somatosensory cortex → pontine nuclei → lateral divisions of cerebellum.
  • Main link between cortex and cerebellum.
  • Lesions result in muscle weakness.
• Vestibulocerebellar:
  
  • Terminates in flocculonodular lobes.
• Reticulocerebellar:
  
  • Terminates primarily in vermis.
• Spinocerebellar:
  
  • Dorsal and ventral.
  • Transmit signals at 120 m/sec.
• All the above tracts form the mossy fibers that terminate on the granule cells in the cerebellar cortex (+).

Question 111

What are the efferent tracts from the cerebellum?

Answer 111

Cerebellum - Efferent Tracts

• Cerebelloreticular:
  
  • Fastigial nuclei → reticular nuclei in pons and medulla.
• Cerebellothalamocortical:
  
  • Dentate, emboliform, globose nuclei → thalamus → motor cortex.
• Cerebellorubral:
  
  • Dentate, emboliform, globose nuclei → red nucleus.
• Cerebellovestibular:
  
  • Cerebellum → vestibular nuclei.

Question 112

Describe gastrointestinal reflexes.

Answer 112

Gastrointestinal Reflexes

• Types of gastrointestinal reflexes:
  
  • Reflexes that are integrated entirely within the gut wall enteric nervous system.
  • Reflexes from the gut to the prevertebral sympathetic ganglia and then back to the GI tract.
  • Reflexes from the gut to the spinal cord or brain stem and then back to the GI tract.
• Reflexes that are integrated entirely within the gut wall enteric nervous system control:
  
  • Much of the GI secretion.
  • Peristalsis.
  • Mixing contractions.
  • Local inhibitory effects.
• Reflexes from the gut to the prevertebral sympathetic ganglia and then back to the GI tract:
  
  • Transmit signals long distance to other areas of the gut tract.
  • Cause evacuation of the colon (gastrocolic reflex).
  • Inhibit stomach motility and secretion (enterogastric reflex).
  • Empty ileal contents into the colon (colonoileal reflex).

Question 113

Describe the gastroileal reflex.

Answer 113

Stomach - Gastroileal Reflex

• Presence of food in stomach triggers
  peristalsis in ileum.

Question 114

Describe the gastrocolic reflex of the stomach.

Answer 114

Stomach - Gastrocolic Reflex

• Food in stomach increases frequency of mass movements.
• When stomach is stretched with food, there is a rapid parasympathetic component.
• A slower CCK and gastrin component is also involved.

Question 116

Describe the vestibulocerebellum.

Answer 116

Cerebellum - Vestibulocerebellum

• Consists of flocculonodular lobes and vermis.
• Functions in control of balance and eye movements.
• Evolved at about the same time as vestibular system.
• Receives fibers from:
  
  • Vestibular system
  • Oculomotor system (pontocerebellar fibers)
• Sends output primarily to vestibular system.
• Loss of flocculonodular lobes → extreme disturbance of equilibrium and postural movements.
• Relationship of vestibulocerebellum to pendular movements:
  
  • Most body movements are pendular (swing back and forth).
  • All pendular movements have tendency to overshoot (WHY?).
  • Appropriate learned subconscious signals from intact cerebellum can stop movement precisely at intended point (= damping system).
  • Changes that occur when cerebellum is removed:
    
    • Movements are slow to develop.
    • Force developed is weak.
    • Movements are slow to turn off.
• Vestibulocerebellar Syndrome:
  
  • Starts with abnormal eye movement including nystagmus.
  • Progressive genetic disease of the flocculonodular lobe.
  • Vertigo, tinnitus.
  • Ataxia.
  • Eventually fine motor skills are lost.

Question 117

Describe the spinocerebellum.

Answer 117

Cerebellum - Spinocerebellum

• Consists mostly of vermis and intermediate zone
• Functions in synergy: control of rate, force, range and direction of movement.
• Receives:
  
  • Information from motor cortex and red nucleus telling cerebellum intended sequential plan of movement for the next few fractions of a second.
  • Feedback information from periphery telling cerebellum what actual movements result.
• Compares two sources of information and sends corrections to:
  
  • Motor cortex via thalamus.
  • Magnocellular portion of red nucleus.

Question 118

Describe the cerebrocerebellum.

Answer 118

Cerebellum - Cerebrocerebellum

• Consists of lateral parts of hemispheres.
• Mostly associated with the premotor and the primary association somatosensory areas of the cerebral cortex.
• Receives corticopontocerebellar projections
• Involved in coordination of skilled movement and speech.
• Plans as much as tenths of a second in advance of actual movements:
  
  • Referred to as “motor imagery”.