BPK 207 Final questions with verified
answers graded A+ updated
Brain/CNS Organization - correct answer ✔✔-Spinal cord
-Brainstem = hindbrain (cerebellum, pons, medulla, reticular formation) and midbrain (tectum --
> superior and inferior colliculi, tegmentum --> red nucleus, substantia nigra
-Diencephalon = thalamus and hypothalamus
-Forebrain = basal ganglia, limbic system (amygdala, hippocampus, cingulate cortex), and
cerebral cortex
Organization of movement - correct answer ✔✔-Movement is a collaborative effort among
regions in CNS
-Cortical, subcortical, brainstem and spinal regions all send reciprocal connections to one
another
-Each region contributes in its own way
Spinal Cord Organization (Macro) - correct answer ✔✔-31 spinal nerves protected by vertebral
column
-Divided into sacral, thoracic, lumbar and cervical spinal nerves
-Cervical nerves control upper limb muscles
-Thoracic nerves control muscles of trunk/chest (including abdominal)
-Lumbar nerves control lower limb and back muscles
-Sacral nerves control bowel and bladder muscles
Spinal Cord Organization - Cross Section - correct answer ✔✔-Grey matter (cell bodies of
neurons) = centre
,-White matter (myelinated/unmyelinated axons making up ascending/descending tracts) =
outside
Spinal Cord Function - correct answer ✔✔-4 types of neurons in spinal cord allow for
coordinated movements
-*Local interneurons* = axons are confined to same or adjacent spinal segment
-*Propriospinal neurons* = axons reach distant spinal segments
-*Projection neurons* = axons ascend to higher brain centres
-*Motor neurons* = axons exit the nervous system to innervate muscles
Spinal Motor Neuron Organization - correct answer ✔✔-Cell bodies of motor neurons are
clustered together in motor neuron pools (or motor nuclei)
--> form longitudinal columns extending over 1-4 spinal segments
-Motor nuclei innervating proximal muscles lie more medially; innervating distal muscles = more
laterally within spinal cord
Motor neurons and muscles - correct answer ✔✔-Typical muscle controlled by ~100 large
motor neurons
-Each muscle fibre innervated by a single motor neuron, usually near midpoint
-Motor neuron plus all the muscle fibres it innervates = motor unit
-Single neuron innervates multiple muscle fibres, but a given muscle fibre is innervated by only
one motor neuron
-Commands signal muscles to contract and produce movement
Motor units - correct answer ✔✔-Can be fast or slow twitch
-Slow-twitch fibres tend to be recruited before fast-twitch --> first fibres recruited are more
resistant to fatigue
-Size of motor units is related to need for refined movement --> more refined movement =
fewer fibres per motor unit
,-Number of motor units recruited is proportional to power needed to generate movement
Motor unit size and contractile force - correct answer ✔✔-Larger motor units contain more
muscle fibres --> generate more force/tension when activated
-Tension can also be increased by recruiting multiple motor units
-Muscles involved in fine movement have small motor units
-Large muscles have many motor units --> some are quite large
Size Principle of Motor Unit Recruitment - correct answer ✔✔-Smaller motor units have smaller
motor neurons
--> lower activation threshold --> activated at lower frequency of stimulation from CNS
-As frequency of stimulation from CNS increases, AP frequency and tension in activated motor
units increases; larger motor units reach threshold and contribute to total muscle tension
-Total muscle tension reflects sum of motor unit activation in a motor neuron pool
Increasing muscle force - correct answer ✔✔-Muscle force can be increased by activating more
motor neurons (recruits more fibres) or by increasing frequency of action potentials in the
muscle fibre (eventually produces tetanus)
Nerve-Muscle Synapse - correct answer ✔✔-Axon of motor neuron innervates muscle at
specialized region of muscle membrane - motor end plate
-Axon loses myelin sheath and divides into branches to form multiple extensions - synaptic
boutons --> Neurotransmitter (ACh) is released from these regions
-Boutons are positioned over junctional folds (deep depressions in the surface of post-synaptic
muscle membrane that contains ACh receptors)
Motor Neuron Signal Transfer - correct answer ✔✔-Depolarization of axon causes Ca2+ to enter
synaptic boutons --> causes ACh release
, -Membrane at end-plate depolarizes due to ACh binding to receptors --> generates end-plate
potential
-Change activates voltage-gated Na+ channels in junctional folds --> converts potential to an
action potential that propagates along muscle fibre --> causes contraction
Importance of muscle - correct answer ✔✔-Almost half of body mass = muscle --> can be
largest consumer of energy; generates heat (can influence body temperature regulation)
-Has mechanical function --> necessary for movement
-Receptors in muscles sense proprioception and regulate muscle forces through reflex arcs
-Can fatigue --> disrupts movement
Spinal Reflexes - correct answer ✔✔-Triggered by activation of sensory receptors
-Many reflexes are highly adaptable and control movements in a purposeful manner
-Produce coordinated patterns of muscle contraction
-Neuronal networks in spinal cord integrate responses
Neuronal Signalling in the Spinal Cord - correct answer ✔✔-Neurons form specific signalling
networks that mediate specific behaviours (e.g. stretch reflex)
-Accomplished through two types of connections --> divergence (e.g. sensory receptor neurons)
and convergence (e.g. motor neurons)
Stretch Reflex - correct answer ✔✔-Activated in response to sudden unexpected muscle stretch
--> serves to keep limb in a specific position
-Spindle --> Ia afferent fibre --> Ia inhibitory interneuron/alpha motor neurons --> inhibitory
neuron inhibits antagonist, motor neurons stimulate homonymous muscle and synergist
Withdrawal (flexion) Reflex and Crossed-extension Reflex - correct answer ✔✔-Painful stimulus
activates nociceptor
-Primary sensory neuron enters spinal cord and diverges
answers graded A+ updated
Brain/CNS Organization - correct answer ✔✔-Spinal cord
-Brainstem = hindbrain (cerebellum, pons, medulla, reticular formation) and midbrain (tectum --
> superior and inferior colliculi, tegmentum --> red nucleus, substantia nigra
-Diencephalon = thalamus and hypothalamus
-Forebrain = basal ganglia, limbic system (amygdala, hippocampus, cingulate cortex), and
cerebral cortex
Organization of movement - correct answer ✔✔-Movement is a collaborative effort among
regions in CNS
-Cortical, subcortical, brainstem and spinal regions all send reciprocal connections to one
another
-Each region contributes in its own way
Spinal Cord Organization (Macro) - correct answer ✔✔-31 spinal nerves protected by vertebral
column
-Divided into sacral, thoracic, lumbar and cervical spinal nerves
-Cervical nerves control upper limb muscles
-Thoracic nerves control muscles of trunk/chest (including abdominal)
-Lumbar nerves control lower limb and back muscles
-Sacral nerves control bowel and bladder muscles
Spinal Cord Organization - Cross Section - correct answer ✔✔-Grey matter (cell bodies of
neurons) = centre
,-White matter (myelinated/unmyelinated axons making up ascending/descending tracts) =
outside
Spinal Cord Function - correct answer ✔✔-4 types of neurons in spinal cord allow for
coordinated movements
-*Local interneurons* = axons are confined to same or adjacent spinal segment
-*Propriospinal neurons* = axons reach distant spinal segments
-*Projection neurons* = axons ascend to higher brain centres
-*Motor neurons* = axons exit the nervous system to innervate muscles
Spinal Motor Neuron Organization - correct answer ✔✔-Cell bodies of motor neurons are
clustered together in motor neuron pools (or motor nuclei)
--> form longitudinal columns extending over 1-4 spinal segments
-Motor nuclei innervating proximal muscles lie more medially; innervating distal muscles = more
laterally within spinal cord
Motor neurons and muscles - correct answer ✔✔-Typical muscle controlled by ~100 large
motor neurons
-Each muscle fibre innervated by a single motor neuron, usually near midpoint
-Motor neuron plus all the muscle fibres it innervates = motor unit
-Single neuron innervates multiple muscle fibres, but a given muscle fibre is innervated by only
one motor neuron
-Commands signal muscles to contract and produce movement
Motor units - correct answer ✔✔-Can be fast or slow twitch
-Slow-twitch fibres tend to be recruited before fast-twitch --> first fibres recruited are more
resistant to fatigue
-Size of motor units is related to need for refined movement --> more refined movement =
fewer fibres per motor unit
,-Number of motor units recruited is proportional to power needed to generate movement
Motor unit size and contractile force - correct answer ✔✔-Larger motor units contain more
muscle fibres --> generate more force/tension when activated
-Tension can also be increased by recruiting multiple motor units
-Muscles involved in fine movement have small motor units
-Large muscles have many motor units --> some are quite large
Size Principle of Motor Unit Recruitment - correct answer ✔✔-Smaller motor units have smaller
motor neurons
--> lower activation threshold --> activated at lower frequency of stimulation from CNS
-As frequency of stimulation from CNS increases, AP frequency and tension in activated motor
units increases; larger motor units reach threshold and contribute to total muscle tension
-Total muscle tension reflects sum of motor unit activation in a motor neuron pool
Increasing muscle force - correct answer ✔✔-Muscle force can be increased by activating more
motor neurons (recruits more fibres) or by increasing frequency of action potentials in the
muscle fibre (eventually produces tetanus)
Nerve-Muscle Synapse - correct answer ✔✔-Axon of motor neuron innervates muscle at
specialized region of muscle membrane - motor end plate
-Axon loses myelin sheath and divides into branches to form multiple extensions - synaptic
boutons --> Neurotransmitter (ACh) is released from these regions
-Boutons are positioned over junctional folds (deep depressions in the surface of post-synaptic
muscle membrane that contains ACh receptors)
Motor Neuron Signal Transfer - correct answer ✔✔-Depolarization of axon causes Ca2+ to enter
synaptic boutons --> causes ACh release
, -Membrane at end-plate depolarizes due to ACh binding to receptors --> generates end-plate
potential
-Change activates voltage-gated Na+ channels in junctional folds --> converts potential to an
action potential that propagates along muscle fibre --> causes contraction
Importance of muscle - correct answer ✔✔-Almost half of body mass = muscle --> can be
largest consumer of energy; generates heat (can influence body temperature regulation)
-Has mechanical function --> necessary for movement
-Receptors in muscles sense proprioception and regulate muscle forces through reflex arcs
-Can fatigue --> disrupts movement
Spinal Reflexes - correct answer ✔✔-Triggered by activation of sensory receptors
-Many reflexes are highly adaptable and control movements in a purposeful manner
-Produce coordinated patterns of muscle contraction
-Neuronal networks in spinal cord integrate responses
Neuronal Signalling in the Spinal Cord - correct answer ✔✔-Neurons form specific signalling
networks that mediate specific behaviours (e.g. stretch reflex)
-Accomplished through two types of connections --> divergence (e.g. sensory receptor neurons)
and convergence (e.g. motor neurons)
Stretch Reflex - correct answer ✔✔-Activated in response to sudden unexpected muscle stretch
--> serves to keep limb in a specific position
-Spindle --> Ia afferent fibre --> Ia inhibitory interneuron/alpha motor neurons --> inhibitory
neuron inhibits antagonist, motor neurons stimulate homonymous muscle and synergist
Withdrawal (flexion) Reflex and Crossed-extension Reflex - correct answer ✔✔-Painful stimulus
activates nociceptor
-Primary sensory neuron enters spinal cord and diverges
