Transcript Neuron Structure

Neuron Structure
Synapse
The Synapse
1. Synthesis of
neurotransmitter (NT)
2. Storage and transport
of NT within vesicles
3. NT Release
4. Activation of
postsynaptic receptors
5. Termination of
transmitter effect (e.g.
reuptake)
Resting Potential
Sodium ions are concentrated on the outside of
the axon membrane.
Potassium ions are concentrated on the inside
of the axon membrane.
Ion channels are closed.
The inside of the axon membrane is more
negative that is the outside.
Action Potential
• Action potential occurs when the membrane
potential rapidly shifts from -70 to +40 mV
– Ion channels open in the membrane, allowing sodium
ions to enter the axon
– Sodium entry shifts the membrane potential toward a
positive value
– Potential is restored when other channels open,
allowing potassium ions to exit the axon
Myelin
• Myelin is a fatty, waxy substance coating
the axon of some neurons.
• Functions:
– Speeds neurotransmission
– Insulates neurons from each other
– Makes neurotransmission more efficient
Neurotransmitters
•
•
•
•
•
•
•
Serotonin
Acetylcholine
Dopamine
Norepinephrine
Epinephrine
GABA
Endorphins
Midline Brain View
Brainstem
• Brainstem is a primitive portion of brain
– Pons: involved in respiration, sleep
regulation, dreaming
– Medulla: involved in life support functions
such as respiration and heart rate
– Reticular activating system is an arousal
system within the brainstem
Subcortical Brain Areas
• Corpus callosum: band of axons that
interconnects the hemispheres
• Thalamus: sensory relay area
• Limbic system: involved in emotionality
• Hypothalamus: feeding, fleeing, mating,
fighting, homeostasis
• Cerebellum: involved in motor control
Limbic System: Seat of Motivation, Emotions
Cerebral Cortex
• Cortex refers to the outer covering of the brain
– Consists of left and right hemispheres
– Cortex is divided into lobes
• Frontal: Self-awareness, planning, voluntary movement,
emotional control, speech, working memory
• Parietal: Body sensations
• Occipital: Vision
• Temporal: Hearing, language comprehension
– Localization of function: do discrete circuits carry
out different functions?
Cortical Lobes
Cerebral Cortex
Motor and Somatosensory Cortex
Language areas: Broca & Wernicke
Primary Visual Pathways
Dorsal and Ventral Visual Pathways
Split brain: Hemispherical Specialization
Brain imaging technologies
• Positron Emission Tomography (PET)
• Makes use of radioactive tracer to measure
cerebral blood flow.
Brain imaging technologies
• Functional Magnetic Resonance Imaging
(fMRI)
• Uses electromagnets to measure oxygen
levels in brain.
Brain imaging technologies
Electroencephalogram (EEG): event-related potentials (momentary
shifts in electrical activity of brain associated with external signals)
Transcranial magnetic stimulation
(TMS): Produces ‘virtual’ lesions