nEURO Flashcards
describe alpha motor neurones?
size
where do they come from and to
- most common motor neurones
- large (~70micrometer diameter)
- from spinal cord to skeletal muscle
what does a motor unit consist of?
an alpha motor unit and ALL the muscle fibres it stimulates
what does a motor unit stimulate?
FINE CONTROL: - few fibres
GROSS CONTROL - many fibres
describe gamma motor neurons
what do they synapse with
size
role
synapse with INTRAFUSAL muscle fibres (in the centre of muscle, spindle)
- ~35micrometers diameter
- role in TONE, not contraction
describe Glutamate
- binds to NMDA receptor
- EXCITATORY NT
- allows influx of Na+ and Ca2+
- inc memb pot O more likely to cause a.p
describe GABA
- binds to GABAA receptors
- INHIBITORY NT
- binding allows Cl- to enter
- dec memb pot O less likely to cause a.p, a GREATER STIMULUS is req to reach threshold
what are the stages of movement?
1) identify target
2) place target in 3D
3) calculate trajectory and speed of intercepting limb
4) calculate force needed to exert & reach target
what are the stages of movement?
1) identify target
2) place target in 3D
3) calculate trajectory and speed of intercepting limb
4) calculate force needed to exert & reach target
the frontal lobe contains?
- the primary motor cortex
- motor association area (premotor cortex)
the parietal lobe contains?
- primary somatic sensory area
- sensory association area
where is the somatosensory map found?
primary sensory cortex
where is the somatotopic/motor map found?
motor cortex
what is the function of the PRIMARY MOTOR CORTEX?
- elicits MOVEMENT with the smallest amount of electrical stimulation
- functional somatotopic map
what is the function of the PRE MOTOR AREA?
what is it split into?
what is the role of each?
split into DORSAL and VENTRAL area
VENTRAL: responsible for arm and face
DORSAL: responsible for LEGS AND TRUNK
- regulate POSTURE more than movement
- has a somatotopic map
where is the SUPPLEMENTARY MOTOR CORTEX found?
what is it split into?
what is the role of each?
- medial surface of the hemisphere
- split into SMA PROPER and preSMA
SMA proper: - somatotopic map - connected to other areas (can linkup fine movement) - controls COMPLEX movement preSMA: - not well connected - connected to the PREFRONTAL CORTEX - role in PLANNING COMPLEX MOVEMENT
where are the CINGULATE MOTOR AREAS?
what is it split into?
what is its role?
- BELOW primary motor cortex
- split into the DORSAL, VENTRAL and ROSTRAL
- each has a somatotopic map
- HIGHLY connected to other areas
- preparation and EXECUTION of movement
where is the POSTERIOR PARIETAL found?
what is its role?
- in parietal lobe
- role in VOLUNTARY MOVEMENT
- receives somatosensory and visual inputs
- POSTURE
- TARGET IDENTIFICATION
what do the motor corticies link to?
- somatosensory system
- visual cortex
what is the cerebellum important for?
- motor role
- fine tune signals going to the periphery
- higher brain function - LEARNING
- link to THALAMUS which links to the motor cortex
the cerebellum cont what % of brain volume, and what % of total neurons?
10% of brain volume
50% of total neurons in brain
where is the cerebellum found? how is it connected to the brain stem?
posterior fossa connected to brain stem via 3 peduncles: - superior - middle - inferior
where does the cerebellum receive information from?
- from sensory cortex
- gets direct info from VESTIBULAR system (senses)
damage to the cerebellum causes what?
- defecit to MOTOR CONTROL
- don’t suffer from paralysis
- ## less CONTROL/ fine tuning over movement- ATAXIA (DYSMETRIA AND DYSDIACHOKINESIA)
damage to movement caused by cerebellum damage is what?
types?
ATAXIA: incoordination 1) DYSMETRIA - errors wuth direction and force 2) DYSDIADOCHOKINESIA - inability to do rapid, alternating movements TREMOR
where are the Basal Ganglia and Thalamic Tracts found?
deep in nuclei of cerebrum
what does the Basal Ganglia consist of ?
- Caudate nucleus (striatum)
- Putamen (striatum)
- Globus Pallidus (striatum)
(exterior and interior) - Subthalamic nucleus
- Substansia nigra
how does information travel to and from the Basal Ganglia?
motor cortex–> basal ganglia–> thalamus–> motor cortex
where does the basal link to?
the cerebral cortex
NOT spine or somatosensory
what is the role of basal ganglia?
- movement control by DIRECT and INDIRECT pathways
what is the function of the direct and indirect pathway?
which 2 NT are important in these pathways?
direct- stimulates movement
indirect- inhibits movement
Glu and GABA are importtant
what is the function of the Thalamus?
what is so sig about the Thalamus?
- acts as a RELAY between subcortical areas and cerebral cortex
- INTEGRATES and PROCESSES info
- ALL sensory systems (except olfactory) links to Thalamus
give an example of how the thalamus receives external input?
light–> retina–> thalamus–> visual cortex
describe the direct pathway?
- GABAergic neuron from Corpus striatum to Substantia nigra is stimulated
- GABA released
- Cl- influx into S.n, increased chance of hyperpolarisation ( S.n–> Thalamus =INHIBITED)
- less GABA in the Thalamus
- Thalamus receives sensory input O any sensory info causes stimulation of GLUTAMINERGIC neuron that goes from the Thalamus to Motor cortex
- inc in Glu in motor cortex O inc movement
describe the indirect pathway?
- GABAergic neuron going from Corpus striatum-> Globus Pallidus is stimulated
- GABA released into G.P
- GABA binds to neuron going from G.P-> STN
- this neuron is likely to be INHIBITED and HYPERPOLARISED due to Cl- influx
- O less likely to get release of GABA in STN
- O any info that enters S.N is likely to cause stimulation
- the GLUTaminetgic neuron that goes from STN to SNis likely to be stim
- O realease of Glut into SN
- O Glut binds NMDA receptors on the neuron that connects SN and thalamus
- Na+ and Ca2+ binds thus more likley to ACTIVATE/DEPOLARISE the GABAergicneuron going from SN to Thalamus
- GABA released and binds to GABAA receptors on the thalamus
- O Cl- influx O INHIBITION
- O less Glutamate released into cortex
- O less movement
where do the corticospinal tracts go to?
- go down spinal cord
where do the lateral corticobubular tracts go to?
- only go down to brainstem
as they control facial + neck muscles
where do lateral motor systems terminate?
what kind of movement does it control?
- in the LATERAL part of the spinal cord
- terminate in regions of GREY matter
- causes activation of muscle going to DISTAL muscle,(eg hands/feet) controls FINE MOVEMENT
what makes grey matter grey?
collection of cell bodies
where do medial motor systems terminate?
what kind of movement does it control?
- in MEDIAL VENTRAL HORN
- innvervate proximal muscles (trunk, upper arms and legs)
where do lateral motor pathways orginate?
where do they TERMINATE?
______________
- ## in a WIDE region of the cerebral cortex, from the appt part of somatotopic map
what can lateral motor pathways activate?
- can directly activate motor neurons
- control INTERNEURONES to inhibit motor neurones
- convey fine movement
what is the other part of lateral motor pathways, other than the lateral corticospinal tracts?
- RUBRISPINAL pathway
not much known in humans
where do the medial motor pathways originate? what are the 2 types?
- most in brainstem but 1) ANTERIOR CORTICOSPINAL PATHWAY orginates from cerebral cortex 2) RETICULOSPINAL - Pontine - Medullary
what is the role of the 2 parts of the RETICULOSPINAL medial motor pathways ?
- PONTINE
- supports POstural muscles
- excitatory
- MEDULLARY
- end on INTERNEURONS
- relaxation of PROXIMAL muscles
- inhibitory
what is the brainstem’s role in posture?( what are the 3 postural reflexes)
1) VESTIBULAR
- affects vestibulospinal (senses) and reticulospinal tracts
- eg your eye staying in a fixed position even if your face moves
2) Tonic neck (learning to turn over)
3) Righting (attempt to right your position so you don’t fall over)
what is the brainstem’s role in locomotion? which area is involved?
Control pattern generators (CPG)
- rhythmic characteristic behaviour eg walking/running
- MODIFICATION: sensory input shifts movement pattern
- voluntary modification
emotion and motivation involve which areas of the brain?
- hypothalamus
- limbic system (amyglada, cingulate gyrus and hippocampus)
- cerebral cortex
hwat is the finction of the limbic system?
acts as a link between the primitive part of the brain (brain stem) and higher cognitive brain
- control impulses
describe the emotion pathway
- stimulus
- CEREBRAL CORTEX integrates the info and sends to LIMBIC SYSTEM
- limbic ‘creates’ the emotion
- ## PHYSIOLOGICAL effects: motor responses or autonomic response (eg inc HR)
cortisol can have a negative effect on what?
immune response
how do we become aware of our emotion?
feedback from limbic system to cerebral cortex
what is motivation?
- internal signals that shape voluntary behaviours
- can be related to SURVIVAL or linked to EMOTIONS
what are the common properties of motivational states/drives?
- increased CNS arousal/alertness
- create GOAL oriented behaviour
- capable of co-ordinating DISPARATE behaviours to achieve a goal
how do motivated behaviours affect the autonomic and endocrine responses?
- hunger
- eat food
- inc PLASMA OSMOLARITY
- HYPOTHALAMUS stimulated
- this stimulates the PITUITARY gland
- ADH produced, binds receptors on kidney
- kidney stimulated
- inc WATER RETENTION
what is the key NT in pleasure and reward?
dopamine
where is high dopamine found?
where is dopamine made?
limbic system
VTA- ventral tegmental area
low dopamine can cause what?
depressive behaviours
addictive drugs do what?
inc dopamine activity
what do antidepressants target?
serotonin and noradrenaline
what is the limbic system made up of?
- amygdala
- singulate gyrus
- hippocampus
what is plasticity?
due to what?
the ability of neurons to alter their connections or change their responses
due to experiences
what are the 2 types of learning?
1) associative (eg Pavlov’s dogs)
2) non- associative
- habituation
- sensitisation
what is memory?
the ability to retainand recall information
where is memory stored?
where are different COMPONENTS of memory stored?
throughout cerebral cortex (in memory traces, which link different parts of a memory from SENSORY CORTICES)
what are the 2 types of memory
1) STM (working)
2) LTM (declarative and reflective)
what are the properties of STM?
describe the working memory?
- holds 7-12 pieces of info
- will disappear
WORKING memory:
- processed in pre-frontal lobes
- collect information from STM AND LTM
describe the LTM
- CONSOLIDATION can convert STM to LTM
- can hold a vast amount of info
consolidation is what?
changes to neuronal excitability or synaptic connections
what are the 2 types of LTM?
1) DECLARATIVE
- facts
- events
- spatial
2) REFLEXIVE (implicit)
give an example of declarative LTM being converted to reflexive LTM
reading/writing
what is language
the abilitity of one member of a species to exchange complex info with others
- a hallmark of an advanced NS
where is language controlled?
- mostly left hemisphere of cerebrum
how is written word processed?
- read words (EYE) –>visual cortex–>WERNICKE’S area (understanding)–> BROCA’S area for a response
where is Wernicke’s area?
PARIETAL-TEMPORAL-OPTIC lobe junction
close to motor cortex
what happens if there is damage to Wernicke’s area?
- inability to understand spoken or written word
what happens if there is damage to Broca’s area?
- inability to respond to written or spoken area
what do PET scans show?
the usage of glucose
