02 Central Nervous System Flashcards
Inputs into the brain
Afferents (SENSORY)
Eg. Touch, pain & temperature, special senses: see, smell, hear, balance, taste
Perceive through INPUTS via receptors and transmit info to the brain via AP.
Outputs from the brain
Efferents (MOTOR)
Output comes from brain (cranial nerves) and reaches its targets through a peripheral nerve.
CNS consists of?
Brain
Spinal Cord
PNS consists of?
Spinal nerves
Cranial nerves
Ganglia
Rostral
Up
Caudal
Down
Superior
Top
Dorsal
Towards the back
Inferior
Bottom
Ventral
Towards the belly
Anterior
Head end
Posterior
Rear end
3 Planes or Orientation for the Brain?
Horizonal - Slice across
Coronal - Slice down x axis of superior brain
Sagittal - Slice down y axis of superior brain
Gray Matter
Consists of nerve cell bodies (Near outside edges of brain)
White Matter
Axons (Towards the center of the brain)
Mostly white cause myelin = fat = white
Where do fibre tracts travel?
Descending fibres - Cortex to spinal cord
Ascending fibres - Spinal cord to cortex
Crossing the midline - right hemisphere of the brain controls the left side of the body
Brainstem
Consists of: Midbrain, Pons and Cerebellum, Medulla Ascending tracts Descending tracts Cranial nerve nuclei Connections to and from the cerebellum Intrinsic Systems (Reticular Formation)
Forebrain
Hemispheres
Deep Nuclei (Thalamus, Basal Ganglia, Limbic system)
Diencephalon (Thalamus, hypothalamus, subthalamus)
Thalamus
Deep nuclei in forebrain
Controls what information reaches the CORTEX
Consciousness
Basal Ganglia
Movement
Cortical output
Cerebellum
Movement
Prediction and Coordination of cortical output
Limbic System
Processing of Emotionality
Saliency filtering
3 Layers of the Eye?
Sclera
Uveal Tract - Blood supply
Retina
3 Compartments of the Eye?
Anterior Chamber
Vitreous Body
Posterior Chamber
Schlemm’s canal
Where Aqueous Humour is constantly recycled so the fluid over the iris stays clear.
Aqueous Humour
Produced by Ciliary body
Glaucoma
Term describing ocular disorders
Rods
Contain Rhodopsin Peripheral Retina Night/Movement Extremely sensitive to light 120mil Rods in Retina
Cones
Contain Iodopsin Central Retina Color & Focus Visual Acuity 6mil Cones in Retina
Cones Central Color
Where does refraction occur?
Cornea and at the lens.
Refractive power of cornea is greater but lens can change its shape.
Central Fovea
Contains ONLY CONE receptors
Greatest Visual Acuity - interfering cell layers pushed aside and light falls directly on photoreceptors.
Optic Disc
Blind spot
Emerging retinal arteries
No photoreceptors
Dark Current (LIGHT OFF)
Constant release of GLUTAMATE by CONES.
Constant Depolarization
OFF Ganglion fires AP
ON Ganglion does NOT fire AP
“Light Current” (LIGHT ON)
LESS GLUTAMATE release due to hyperpolarized cone receptor by light.
Close channels.
OFF Ganglion does NOT fire AP
ON Ganglion fires AP
What is the visual pathway?
Left field projects to RIGHT cortex
Right field projects to LEFT cortex
Dorsal Stream
Tells SPATIAL vision: Where? How?
Ventral Stream
Tells OBJECT vision: What? (Recognition)
Extereoceptors
OUTER - Interact with world around us
Pain and Temperature
Discriminative Touch/Vibration
Proprioceptors
INNER
Join receptors
Golgi tendon organs - know force generated on a body part
Muscle spindle
Anterolateral System
Comprises of ALL FIBRES carrying {Pain & Temperature} from the spinal cord to the brainstem + thalamus.
Spinothalamic Tract
Comprises of ONLY the fibres projecting from the spinal cord to the thalamus.
01 {Pain & Temperature}
Anterolateral System: Spinothalamic Tract
( 1 ) Cell body in spinal ganglion crosses midline at level of spinal cord
Synapse with 2nd Order Neuron @ spinal cord (Posterior horn)
( 2 ) Fibres ascend the anterolateral system (Spinal cord > brainstem + thalamus) contralaterally
( 3 ) Fibres synapses + terminates at VPL of Thalamus
Neurons in thalamus project to Primary Somatosensory Cortex (Lateral) and ‘Limbic system (Medial system)’
Medial System
Emotional response to pain - OUCH
Lateral System
Discriminative localization of pain - You know where the pain is. (Eg. Left toe)
02 (Discriminative Touch, Vibration, Pressure)
Posterior Column Medial Lemniscus Pathway
( 1 ) Cell body in spinal ganglion
( 2 ) Ascends in Posterior Column + Synapses with 2nd Order Neuron in Caudal Medulla + Crosses midline
( 3 ) Ascends to Thalamus contralaterally through Medial Lemniscus
( 4 ) Synapse in VPL of Thalamus with 3rd Order Neuron and then projects to Primary Somatosensory Cortex
03 (Proprioception)
Conscious proprioception - (Cortex)
Travels with the Posterior Column Medial Lemniscus System to the Thalamus > Cortex
Unconscious proprioception - (Cerebellum)
Travels through Spinocerebellar tract to Cerebellum
Enters spinal cord, ascends ipsilaterally and enters cerebellum on the same side (Some synapses along the way)
Why are synapses important?
Every synapse you can decide if you want to continue with this information or not.
What does the motor system control?
Limb movement
Posture
Core
Balance
Lateral Corticospinal Tract
Innervation of limbs
Skilled movement of extremeties
Anterior Corticospinal Tract
Innervation of proximal muscles
Postural adjustment
Stabilizes core
04 (Corticospinal Tract)
( 1 ) Primary Motor Cortex (Upper Motor Neuron UMN)- Where cell bodies are (SUPER LONG Axons: Brainstem to Caudal Medulla)
( 2 ) Lateral crosses over @ Medulla, Anterior stays on the same side and crosses @ Spinal Cord level
( 3 ) Synapses at Spinal Cord with Lower Motor Neuron (LMN) for Lateral and Anterior
Goes from UMN to LMN - no synapses.
What is the trend seen in somatotopic organization from cortex to spinal cord?
Important areas get more cortical space.
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What does the motor system do?
Does more than just control of voluntary movements.
Compensates for balance (Vestibulospinal tracts)
Compensates for voluntary movement
Muscle tone - Readiness of a muscle. Couch potato vs olympic athlete in 100m dash - Y-neurones
Moves our eyes/head towards what interests us
Motor reflexes
Vestibulospinal Tract
Maintains balance, postural control, muscle tone, gravity
Reticulospinal Tract
Postural control, muscle tone
Tectospinal Tract
Directs eyes and head/neck to object of interest.
What are the 3 Lobes of the Cerebellum?
( 1 ) Flocculonodular Lobe (Vestibulocerebellum) - Trunk control and stability and tells us about gravity - deals with Vestibular information. [WORM]
( 2 ) Anterior Lobe (Spinocerebellum/Vermis) - Synergistic movements of extremeties [NEWT]
( 3 ) Posterior Love (Cerebrocerebellum) - Has most SA of neurons. - Coordination of intricate and complex movements, topographical representation of the extremities, areas for eye movement and speech (tongue mouth face etc).
What are the 3 Cerebellar Loops and their function?
Vestibulocerebellar connections
Spinocerebellar connections
Cerebrocerebellar connections
Allow:
- Coordinated, balanced and smooth movement
- Anticipation of movement
- Predictions that feedback to the cortex (Predicts movement of everything in field of vision)
What does the Cerebellum do?
Stickler for detail - Micro-manager
Coordinator and predictor of movement.
Balance - Linked to vestibular nuclei
Gait - Pattern of movement of the limbs
Receives and interprets proprioceptive information (Muscle tone, where my limbs are etc)
Fine Movements, Hand-Eye Coordination
Predicts sensory consequences of movement.
Information sent to cerebellum can be used for skilled manipulation of muscles and mental concepts.
Vestibular Information of the Cerebellum
Project from PARAVERMIS (next2vermis) to FLOCCULONODULAR lobe.
Provides information about the position of the head and body in space.
Helps orient eyes during locomotion.
Vestibulocerebellar Loop
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