5a - Motor System & Action Flashcards
what are the 5 main major division of the CNS?
- spinal cord
- cerebellum
- brainstem
- diencephalon
- cerebral cortex
the cerebrum consists of which 2 components?
- cerebral cortex
- subcortical structures
def: a continuous layer of wrinkled grey matter that covers the cerebrum and is responsible for higher functions of the CNS
cerebral coretex
def: the ridge of a wrinkle in the brain
gyrus
def: the groove between the gyrus
sulcus
what are the 3 subcortical structures?
- hippocampus
- amygdala
- parts of the basal ganglia
the hippocampus is in charge of…?
memory and navigation
the amygdala is in charge of…..?
emotions and memory
the diencephalon consists of which 3 structures?
- thalamus
- sub-thalamus
- hypothalamus
def: a collection of nuclei that relay and integrate information between the cerebral cortex and the peripheral senses, spinal cord, and brainstem. all the sensory info passes through here before reaching the cortex, interacts with the basal ganglia to modify movement
thalamus
def: includes the subthalamic nuclei, is part of the basal ganglia
sub-thalamus
the brain stem consists of which 3 components?
- hindbrain
- midbrain
- reticular formation
what are the 2 components of the hindbrain?
- pons
- medulla
what are the 2 components of the midbrain?
- tectum
- tegmentum
def: the main connections to the cerebellum
pons
def: regulates body functions to allow life
medulla
def: has a superior colliculi for eye movement control and an inferior colliculi related to the auditory system
tectum
def: has a red nucleus that forms the descending tract known as the rubrospinal tract and a substania nigra which is part of the basal ganglia
tegmentum
what is the spinal cord orginization?
- cervical
- thoracic
- lumbar
- sacral
- coccygeal
how many nerves are in each section of the spinal cord?
- cervical = 8
- thoracic = 12
- lumbar = 5
- sacral = 5
- coccygeal = 1
what is the role of the cervical nerves?
control upper limb muscles
what is the role of thoracic nerves?
control the muscles of the trunk and chest
what is the role of lumbar nerves?
controls lower limb and lower back muscles
what do cervical and lumbar enlargements do?
these regions contain the neural circuits responsible for controlling the arms and legs
def: made up of cell bodies of neurons
grey matter
def: made up of unmyelinated or myelinated axons of the neurons
white matter
where are the sensory and motor components within the grey matter?
the sensory component is on the dorsal side
the motor component is on the ventral side
what are the 4 types of neurons within the spinal cord
- local interneurons
- propriospinal neurons
- projection neurons
- motor neurons
def: axons are confined to the same or adjacent spinal segment
local interneurons
def: neurons whose axons reach distant spinal segments
propriospinal neurons
def: neurons whose axons ascend to higher brain centers
projection neurons
def: neurons whose axon exits the nervous system to innervate mucles
motor neurons
______ _____ neurons (alpha motor neurons) execute movement and have a specific organization within the spinal cord
spinal motor neurons
cell bodies of the alpha motor neuron are clustered in motor neuron _____ or motor nuclei
pools
where within the spinal cord do the neurons that innervate distant muscles reside?
the distant muscles are connected to neurons on the lateral sides of the spinal cord, the same goes for close muscles
what path does somatosensory information take from the peripheral nervous system to connect to the spinal cord
via the dorsal root
what path does motor output take to go from the CNS to the PNS?
ventral roots
the motor neuron and the muscle fibers it innervates are called?
a motor unit
where are muscle fibers innervated ?
at their mid point
T or F: the fibers of 1 motor units can vary in twitch speed
false, they are all the same speed
def: muscle fibers that can exert strong and fast movements but fatigue quickly due to their mitochondria concentration
fast twitch
def: muscle fibers that can work for longer periods of time without fatigue
slow twitch
if there are fewer muscle fibers within the unit, there is _____ _____ _____ control in that limb
fine detail control
what dictates the power of a movement?
the number of motor units recruited
explain the nerve muscle synapse:
- impulse propagates down axon of alpha motor neuron
- the end of the axon spreads out into multiple synaptic boutons
- synaptic boutons release Ach into junctional fold on the muscle endplate
- the Ach binds to the receptor channel
- channel opens allowing increased inflow of Na+
- positive feedback loop that leads to an action potential
what are 3 ways the CNS can increase muscle force?
- recruit different sized motor units
- recruit more units
- increase frequency of action potentials in alpha motor neuron
more fibers recruited in a larger motor unit = ?
more tension
what kind of relationship is there between motor units and muscle fiber tension?
summative relationship
smaller motor units have _____ threshold for activation
lower
sustained muscle contraction is when : ? (2)
- maximum muscle tension occurs
- action potential frequency is very high
what are the 5 types of neural circuits?
- divergence
- convergence
- serial processing
- parallel processing
- reverbation
def: a mechanism for spreading stimulation to multiple neurone, sensory afferent neutron spreading info to different regions of spinal cord and brain
divergence
def: providing input from multiple sources to 1 neutron, descending tracts converging onto alpha motor neuron
convergence
def: circuit from 1 neutron to 1, stretch reflex
serial processing
def: a mechanism in which neurons or pools process the same information simultaneously
parallel processing
def: positive feedback loop
reverberation
what is the difference between disynaptic and monosynaptic?
- 1 synapse vs 2
- disynaptic = one of the neurons that is connected in the pathways inhibits activation then connects to an alpha motor neuron
def: muscle spindle feels unexpected stretch, the 1a afferent is connected to the alpha motor neurone of the units and it activates leading to the muscles connecting and thus increasing joint stability
monosynaptic stretch relfex
def: causes a limb to pull away from a painful stimuli
withdrawal reflex
what are the steps of the withdrawal reflex?
- nociceptor gets activated and then diverges its signal into 3 paths
