HNS01 Overview Of The Central Nervous System Flashcards
CNS components
- Cerebral cortex
- Cerebellum
- Brainstem
- Spinal cord (connect to higher centres by brainstem)
Function of cerebral cortex
- Cognition
- Perception
- Voluntary movement
Function of Limbic system
Emotion
Function of Brainstem
Housekeeping
Function of Cerebellum
Motor coordination
2 type of synapses in Brain
- Excitatory / Glutamatergic synapses
- AMPA receptor
- NMDA receptor
- Kainate receptor - Inhibitory synapses (e.g. GABAergic synapse)
- GABA-gated Cl channel (other agonists: Benzodiazepine, Ethanol, Barbituate)
Excitatory synapse and Inhibitory synapse
Excitatory synapse:
Action potential in presynaptic neuron
—> lead to Depolarisation in postsynaptic neuron
Inhibitory synapse:
Action potential in presynaptic neuron
—> lead to Hyperpolarisation in postsynaptic neuron
Sensation and Perception
Sensation (OBJECTIVE sensory physiology):
- Event: interact with sense organs
- Stimulus: adequate stimulus to receptor
- Excitation: central processing
- Integration: central processing in functioning brain centres
Perception (SUBJECTIVE sensory physiology):
5. Impression: conscious subject
6. Perception: subject with experience, reasoning, personality
—> performed in Association Cortex
Important processes in sensory system
- Sensory transduction
- receptor - Receptive field
- receptor
- peripheral and central neuron - Central processing
Somatic senses
- Mechanoception
- Proprioception
- Thermoception
- Nociception
Special senses
- Taste
- Smell
- Hearing
- Balance
- Vision
Mechanoreceptors in skin
Mechanical stimuli delivered to skin activate several mechanoreceptors simultaneously but to different degree
- Pressure (Slowly adapting)
- Merkel’s disk - Pain / Temperature
- Free nerve ending - Touch
- Meissner’s corpuscle - Vibration (Rapid adapting)
- Pacinian corpuscle
- Ruffini’s ending (Skin stretch)
Crossed ascending projection
Information from one side of body crossed at different levels of spinal cord / brainstem
—> opposite side of cerebral cortex
Cross at Dorsal column nuclei
- Discriminative touch
- Vibration
- Position sense
Cross at Spinal cord
- Temperature
2. Pain
Narrow vertical columns of submodalities in somatosensory cortex
- Slow-adapting functional unit
2. Rapid-adapting functional unit
Topographic body map
- Distorted body surface for tactile sensibility
- Magnified areas of high acuity
Taste
- bitter, salt, sour, sweet, umami (MSG) (all chemical stimulation)
- all chemical stimulation
- G-protein: Sweet (甜5), Bitter (苦2), Umami (味精4)
- Ion channels: Salty (ENaC), Sour (OTOP1, PKD2L1), (bitter), Chilli (Nociception)
Common plan of sensory systems
- Sensory transduction (feature extraction)
- Topographic organisation (maps can be found at different levels)
- Bilateral inputs to cortex (e.g. skin: crossed, auditory: **bilateral, taste: **ipsilateral)
Motor system
CNS —> PNS (Motor division) —> Somatic NS (e.g. skeletal muscle)
Example: reflexive control (Stretch reflex, Golgi tendon reflex, Pain reflex)
3 Cardinal neural regions responsible for motor control
- Motor cortex
- Cerebellum
- Basal ganglia
Crossed descending projection
One side of motor cortex to contralateral side of head and body
Seizure
Epilepsy
—> Spread of abnormal synchronised cortical discharge (e.g. cortical area responsible for trunk to area responsible for head)
Association cortex function
- Cognition
- Consciousness
Lateralization of cerebral cortex
Left hemisphere:
- Right hand
- ***Logical thinking
- ***Language ability
- Writing
- ***Science and math work
Right hemisphere:
- Left hand
- Musical and artistic ability
- ***Perception of space
- ***Imagination and fantasising
- ***Body control and awareness
Limbic system
Components:
- Hippocampus
- Amygdala (fear response, negative emotions)
Function:
- Cognition
- **Learning and memory
- Sleep and wakefulness
- **Emotion
Imaging techniques
- Functional MRI
- CT scan
- PET scan (molecular imaging)
Parkinson’s disease
Degeneration of Dopamine neuron within Substantia nigra (area within Basal ganglia)
—> movement disorders
Alzheimer’s disease / Dementia
Shrinkage of Hippocampus (+ Cortex) —> impairment of learning and memory
Causative components:
- Amyloid plaque (extracellular)
- Neurofibrillary tangle: Tau fragment (intracellular)
—> ALL lead to damaged neurons
Psychosis / Schizophrenia
Blockade of NMDA receptor by PCP (phencyclidine piperidine)
—> do not allow Ca, Na to go through channel
—> behaviour mimic schizophrenia
Drug addiction
Dopamine neurons in Nucleus accumbens (part of Basal ganglia)
Heroin:
1. Bind to opioid receptor of GABAergic inhibitory neuron
—> do not allow GABAergic inhibitory neuron to release GABA onto GABA receptor on presynaptic receptor
—> NO inhibition of dopamine release
- Direct agonist to opioid receptor on postsynaptic neuron
—> direct stimulation of postsynaptic neuron
—> cAMP —> activated protein
Cocaine:
1. Block reuptake transporter on presynaptic neuron
—> more dopamine to postsynaptic neuron
—> cAMP —> activated protein
Summary
Limbic system:
- Hippocampus: Alzheimer’s disease
- Amygdala: Fear response, Negative emotions
Basal ganglia:
- Substantia nigra: Parkinson’s disease
- Nucleus accumbens: Drug addiction
