Basal ganglia- Direct pathway of movement

what has to be carefully controlled to control smooth movement?

direct (excitatory)+ indirect (inhibitory) pathway

what does substantia nigra release? where to?

dopamine releases dopamine to the striatum

Are D1 receptors excitatory or inhibitory?

excitatory

action of dopamine on the striatum favours? how does cocaine or ecstasy effect it?

excitatory projections to the motor cortex to reinforce the desired movements cocaine or ecstasy 1. often have enhancements of movements e.g. dance 2. less able to control unwanted movements e.g. grinding teeth

basal ganglia made up of?

group of nuclei -millions of nerve cell bodies

Are D2 receptors excitatory or inhibitory?

inhibitory

What is the basal ganglia?

structure located deep within the brain

STRIATUM also receives signals from which other structure?

substantia nigra

Where is dopamine produced?

substantia nigra

describe how D1 receptors + dopamine work? where are D1 receptors expressed what happens when dopamine released

1. D1 receptors expressed by striatal cells tht project to internal globus pallidus 2. when dopamine released by substantia nigra, binds to D1 3. activates direct pathway that controls muscle want to move

describe how D2 receptors + dopamine work? where are D2 receptors expressed what happens when dopamine released

1. D2 receptors are expressed by striatal cells that prokect into external globus pallidus 2. dopamine binds to D2 receptors; inhibits indirect pathway for tht same muscle

dopamine actions DOPAMINE ACTS WITH 2 DIFFERENT EFFECTS DUE TO?

1. acts on both direct + indirect pathways BUT WITH OPP EFFECTS DUE TO PRESENCE OF 2 DIFFERENT RECEPTORS: D1 receptors (excitatory) D2 receptors (inhibitory)

describe the striatum parts?

1. caudate nucleus 2. putamen

how is the basal ganglia stimulated?

1. cerebral cortex decides on body movement 2. sends info to basal ganglia -help execute smooth movement

Describe the direct pathway?

1. cerebral cortex send excitatory projections to striatum 2. striatum send inhibitory projections to intenal globus pallidus 3. internal globulus sends inhibitory projections to the thalamus (usually in active state) 4. if the striatum inhibits the globus pallidus, then the globus pallidus cannot inhibit the thalamus =THE 2 NEGS CANCEL OUT 5. RESULT- thalamus can send EXCITATORY signals to motor cortex 6. initiates VOLUNTARY MOVE ENTS

what is the inhibitory neurotransmitter?

GABA

what is the excitatory neurotransmitter?

Glutamate

DESCRIBE THE INDIRECT PATHWAY

1. cerebral cortex sends excitatory signals to the striatum 2. striatum sends inhibitory signals to the external globus pallidus 3. external globus pallidus sends inhibitory projections to the SUBTHALAMIC NUCLEUS 4. subthalamic nucleus are always active 5. if striatum inhibits external globus pallidus, external globus pallidus cannot inhibit subthalamic nucleus =2 NEGS CANCEL OUT 6. Subthalamic nucleus sends excitatory projections out to INTERNAL GLOBUS PALLIDUS (directly opp to direct pathway) 7. by exciting internal globus pallidus; INHIBITS THALAMUS 8. THALAMUS SENDS EXCITATORY SIGNALS TO THE MOTOR CORTEX

how does the basal ganglia work? 2 PATHWAYS?

1. entire cerebral cortex projects onto the striatum 2. striatum projects onto the thalamus 3. neurons head back to cerebral cortex via 2 PATHWAYS: DIRECT (EXCITATORY) INDIRECT (INHIBITORY)

Describe the globus pallidus parts

1. internal globus pallidus 2. external globus pallidus

basal ganglia function

1. start, stop + control movements 2. inhibit undesired movements e.g. walk 1. helps one leg step forward + keeps other leg stationary

basal ganglia structure?

3 primary subcortical: 1. caudate nucleus 2. putamen 3. globus pallidus Other: Claustrum Amygdala Secondary structure: 1. Substantia 2. subthalamic nucleus

Where are D1 receptors located?

D1 receptors expressed by striatal cells tht project to internal globus pallidus

Where are D2 receptors found?

D2 receptors are expressed by striatal cells that prokect into external globus pallidus

basal ganglia linked to other structures including?

THALAMUS 1. ventral anterior nuclei 2. ventral lateral nuclei MIDBRAIN 1. substantia nigra

Where is dopamine synthesized?

Ventral tegmentum and SNc (midbrain)