Section 1: Nervous System Flashcards
Brain: Frontal association cortex - functions
Intelligence Personality Behaviour Mood Cognitive function
Brain: Parietal association cortex - functions
Spatial skills
3D recognition, e.g. shapes, faces, concepts, abstract perception
Brain: Temporal association cortex - functions
Memory
Mood
Aggression
Intelligence
Brain: Non-dominant hemisphere (right) - functions and effects of injury
Non-verbal language (e.g. body language) Emotional expression (tone of language) Spatial skills (3D) Conceptual understanding Artistic/musical skills (can sing when they can't speak)
Loss of non-verbal language Speech - lacks emotion Spatial disorientation Inability to recognise familiar objects Loss of musical appreciation
Tracts vs nerves
Tracts: bundles of axons in the CNS
Nerves: bundles of axons in the PNS
Brain: Auditory cortex - function
Primary:
Puts time and tone together
Simply take the sounds in its individual tones - in a tonotopic fashion
Secondary:
Interprets and understands these tones
Brain: Visual cortex - functions
Primary visual cortex:
Conscious processing of visual stimuli
Dives right into the brain medially
Secondary visual cortex:
Interpretation
Illusions affect secondary, not primary
Brain: Wernicke’s area
Analyses/understands the spoken word via time/tone relationship
2° language area
Sensory/Wernicke’s/Fluent aphasia - problem with ability to interpret language/instructions
Brain: Broca’s area
Controls the motor act of speech
Smooth vocalisation
Motor/Broca’s/Non-fluent aphasia - can still read and write properly, but struggles to get words out
Brain: Arcuate fasciulus
Responsible for taking information from Wernicke’s area to Broca’s area
White matter tract
Connectional aphasia - can understand and read, but difficulty linking tgt
Brain: Gray matter
Where cell bodies live
Brain: White matter
Made up of bundles of axons, many of which are myelinated
Brain: Hypothalamus - function
Deals with endocrine functions
Mid-brain
Gateway to (higher order) cerebrum Can cause Parkinson's disease
Frontal and temporal lobes - tissue
Have 3 strips of tissue; superior, middle and inferior
Brain: Occipital lobe
Gyri and sulci are more densely packed
To do with processing of vision
Brain: Cerebellum
Extra wrinkly
Sense of balance
Processing and planning of movement
Assists motor cortex and basal ganglia by making body movements smooth and co-ordinated
Helps maintain normal posture and balance
Brain: Parts of the brainstem
Midbrain
Pons
Medulla
All contain sensory (ascending) and motor (descending) neurons
Brain: Parts of the hindbrain
Cerebellum
Pons
Medulla
Brain: Primary motor cortex
Decides what action to take
Intricate planning
Relates to what is in the homunculus
Brain: Exener’s area
Controls hand movements
What is a homonculus
Representation of entire body (body map)
Areas with higher sensitivity have greater area / larger no of neurons
Houses large cells that will product down from the motor cortex to the spinal cord
Brain: Left hemisphere is dominant for ____
Language
Brain: Medulla - function
Regulates heartbeat (CV system)
Brain: Primary cortices
1° motor cortex: pre-central gyrus
1° sensory cortex: post-central gyrus
1° auditory cortex: superior temporal gyrus
1° visual cortex: occipital lobe
Brain: SMAGLA
Supramarginal and angular gyri
Language areas
Interpretation of what is being read/written
Control eye movements responsible for reading
Spinal cord: Sensory input
Afferent pathway; to bring / carry towards
Spinal cord: Motor output
Efferent pathway; carry away
Spinal cord: Enlargements on vertabrae
Need more SA to accommodate nerves in arms and legs
Cervical enlargement - superior enlargement (upper limbs)
Lumbar enlargement - inferior enlargement (lower limbs)
Spinal cord: Types of nerves
Cervical nerves (1-8) Thoracic nerves (1-12) - come out directly under each rib Lumbar nerves (1-5) - spinal cord ends around lungs Sacral nerves (1-5) - fused vertebrae Coccygeal nerve
Spinal cord: Meninges
Protection for spinal cord
From superficial to deep:
Dura mater - durable; protects outside of spinal cord, composed of dense irregular CT
Arachnoid mater - thin and avascular, contains collagen and elastic fibres
Pia mater - tightly adhered, thin and transparent, many blood vessels
Spinal cord: Cauda equina
Fibres that exit at the lumbar levels to supply nerves to and from legs
Spinal cord: Filum terminale externum
Anchors spinal cord onto bottom of coccyx
Spinal cord: What to do if meninges are inflammed
Take CSF fluid and determine if there are pathogens there
CSF is nutrient-rich
Spinal cord: Somatic nervous system - types of periphery sensory
Discriminative sensory: touch and pressure
Non-discriminative sensory: pain and temperature
Spinal cord: Somatic nervous system - encapsulated receptors
Meisner’s corpuscle: touch
Pacinian corpuscle: pressure
Spinal cord: Somatic nervous system - types of nerves
Pseudo uni-polar neuron:
Has myelin sheath - more effective conduction of info and energy
~50ms^-1
Can go to either 1. up to brain stem or 2. into gray matter
Has an encapsulated receptor
Free nerve-ending:
Unmyelinated as doesn’t need to fire very often
Only responds to the extreme, i.e. pain and temp
~1ms^-1
Goes only to gray matter
Spinal cord: Ganglion
A gang of cell bodies
Spinal cord: Dorsal root
Where cell bodies live
Where does the spinal cord begin
Medulla oblongta
Spinal cord: Ventral and dorsal
Ventral: motor functions
Dorsal: sensory functions
Autonomic functions: housed in between
Brain: Lateral fissure
Primarily separates the frontal lobe from the temporal lobe
Partially separates parietal lobe from temporal lobe
Dermatomes and myotomes
Dermatomes: Cluster of nerve fibres in the skin that will go towards a particular area in the spinal cord
Myotomes: Cluster of nerve fibres in the muscle that will go towards a particular area in the spinal cord
Brain vs spinal cord: Grey and white matter
Brain: Gray matter goes around outside and white matter inside
Spinal cord: Central gray matter at its core and insulating white matter on the outside
Motor vs sensory input - how is carried
Motor info tends to be carried forward
Sensory info carried back in the brain
Funiculi
Big grouping of fasciulus
Columns
White matter
Gracile vs Cuneate fasciculus
Gracile: lower limb info
Cuneate: upper limb info
Mid-upper region of spine = both
Lower region = gracile only
Spinal cord: Thalamus
Decides which sensation is important
Deals with motor sensory info input
Spinal cord: Cuneate nucleus
A ganglion
Spinal cord: Discriminative pathway - Where do nerves cross over
Medulla
Spinothalamic tract
Pain and temperature pathway
Dorsal Column - Medial Leminiscal System
Pathway of discriminative sensation
Spinothalamic tract: Medial lemniscus
Where all pain, temp, and discriminative info comes together
Associative vs dissociative sensory loss
Associative: If nerves (sensory and free nerve endings) on right side are affected, the left side loses pain, temp and discriminative info
Dissociative:
If free nerve ending on right side is affected, left side loses pain and temp (but right side loses discriminative info?)
Spinal cord: Pain and temp pathway - where do nerves cross over (decussate)
Anterior white commissure
Brain: Motor region of cerebral cortex
Initiates and controls precise, discrete muscular movements
Brain: Basal ganglia - functions
Receives input from cerebral cortex and provides output to motor parts of cortex via the medial and ventral group nuclei of thalamus
Establishes muscle tone
Integrate semi-voluntary, automatic movements
Picks up practice and learned movements
Smooth and precise movement control
Regulates initiation and termination of movements - may be linked to Parkinson’s disease
Parkinson’s disease - symptoms
Mood (emotionally flat)
Wooden face and rigidity
Bradykinesia (hypokinesia - difficulty initiating movement)
Tremor at rest
Homunculus: Neurons at hand
~160 microns wide
Very wide
Pyramidal tract AKA…
Corticospinal tract
i.e. from cortex to spine
Brain: Internal capsule
Thick band of white matter
Contains ascending and descending axons
Has a homuncular representation
Corticospinal tract: Where do pyramidal fibres cross over
85% cross over at pyramidal decussation (deals with precise movement)
15% crosses over at anterior corticospinal tract (spinal segmental level - deals with coarse movement)
Corticospinal tract: What happens if there’s a lesion at the lower motor neuron
Since LMN activates muscles for contraction, it results in flaccid paralysis (floppy)
Brain: Basal ganglia/nuclei - structure
Group of grey matter in forebrain
- Caudate nucleus
- Putamen
- Globus pallidus (much paler, has internal and external)
- Subthalamic nucleus
- Substantia nigra
1+2 = striatum
2+3 = lentiform nucleus
1 + lentiform = corpus striatum
Hypoactivity and hypoexcitability
Output from hypoexcitability in brain is hypoactivity in the body
Define hypoexcitability
Uncontrolled firing of inhibitory neurons
When does Parkinson’s disease occur
When 60-80% of nigrostriatal pathways die (cup half full)
Results in lots of glutamate firing –> toxic (spasticity)
Dopamine
Itself is not excitatory or inhibitory, depends on what type of receptor it binds to
Holds neurons ready (cup full)
How is Parkinson’s disease treated
With levodopa (precursor of dopamine, as dopamine itself is not digested well in stomach), which is then converted to dopamine (increases dopamine, decreases ACh) Levodopa crosses gut --> crosses blood-brain barrier --> converted to dopamine by cells in substantia nigra Causes fluctuation of dopamine levels, thus symptoms range from hallucinations/depression (too much dopamine) to rigidity (not enough dopamine) Taken 6 times a day
Schizophenia
Treated with anti-dopamine
Patients start off with hallucinations and depression, and take anti-dopamine which makes them rigid (i.e. polar opposite of Parkinson’s)
Basal ganglia vs cerebellum
Basal ganglia = initiation of movement
Cerebellum = termination of movement
Lesion in corticospinal tract: Damage to UMNs and LMNs
Upper motor neurons: lose all control over LMNs –> spastic paralysis, but can still activate themselves
Lower motor neurons: totally no input to muscles –> flaccid paralysis (muscles limp and floppy)
When do lower motor neurons (LMNs) act independently
Reflexes
Brain: Cerebrum
Consists of an outer cerebral cortex, internal region of cerebral white matter, and gray matter nuclei deep within the white matter
Brain: Cerebral cortex - structure
Region of grey matter that forms the outer rim of the cerebrum
Contains billions of neurons arranged in layers
Brain: During embryonic development, does grey or white matter develop faster
Gray matter of cortex enlarges much faster than the deeper white matter
Causes cortical region to roll and fold on itself
Brain: Gyri, fissures and sulci
Gyri - folds
Fissures - deepest grooves between folds
Sulci - shallower grooves between folds
Brain: Longitudinal fissure
Separates cerebrum into right and left halves, called hemispheres
Brain: Corpus callosum
Broad band of white matter
Contains axons that extend between cerebral hemispheres to connect them
Brain: Central sulcus
Separates frontal lobe from parietal lobe
Brain: Cerebral white matter - tracts
Association tracts - conduct nerves impulses between gyri in same hemisphere
Commissural tracts - conduct nerve impulses from gyri in one cerebral hemisphere to corresponding gyri in other hemisphere
Projection tracts - conduct nerves impulses from cerebrum to lower parts of CNS (thalamus, brain stem, spinal cord) or vice versa
Brain: Basal ganglia/nuclei - Axons from the substantia nigra terminate in the…
Caudate nucleus and putamen
Brain: Sensory, motor, and association areas
Sensory areas: receive sensory info and involved in perception (conscious awareness of a sensation)
Motor areas: control execution of voluntary movements
Association areas: deal with more complex integrative functions, e.g. memory and emotions
Brain: Where do sensory impulses mainly arrive
In the posterior half of both cerebral hemispheres, in regions behind the central sulci
Brain: Primary sensory areas
Receive sensory info that has been relayed from peripheral sensory receptors through lower regions of the brain
Brain: Sensory association areas
Often adjacent to primary areas
Integrate sensory experiences to generate meaningful patterns of recognition and awareness
Brain: Somatosensory association area
Receives input from primary somatosensory area, thalamus and other parts of brain
Allows you to determine the exact shape and texture of an object by feeling it, determine orientation of object, sense relationship of one body part to another
Storage of memories of past somatic experiences - can compare
Brain: Visual association area
Receives sensory impulses from primary visual area and thalamus
Essential for recognising and evaluating what is seen
Brain: Facial recognition area
Receives nerve impulses from visual association area
Stores info about faces –> allows recognition of them
Often more dominant in the right hemisphere
Brain: Auditory association area
Recognises a particular sound as speech, music or noise
Brain: Common integrative area
Bordered by somatosensory, visual and auditory association areas
Integrates sensory interpretations –> allows formation of thoughts based on a variety of sensory inputs
Brain: Pre-motor area
Motor association area
Deals with learned motor activities of a complex and sequential nature
Generates nerve impulses that cause specific groups of muscles to contract in a specific sequence
Brain: Hemisphere lateralisation
Functional asymmetry of left and right hemispheres of brain
CNS: Layers of protection
1st layer: Hard bony skull and vertebral column
2nd layer: Meninges
3rd layer: Space between two of the minengeal membranes containing CSF
Cerebrospinal fluid (CSF)
A buoyant liquid that suspects the central nervous tissue in a weightless environment while surrounding it with a shock-absorbing, hydrauilc cushion
Spinal cord: Epidural space
Space between the dura mater and wall of vertebral canal
Where does spinal cord extend to and from
Adults: From medulla to border of second lumbar vertebra
Newborn: From medulla to third or fourth lumbar vertebra
Spinal cord: Anterior median fissure and posterior median sulcus
Anterior: wide groove on anterior (ventral) side
Posterior: narrow furrow on posterior (dorsal) side
Spinal cord: Gray commissure
Forms crossbar of ‘H’
Contains central canal, which extends the entire length of the spinal cord and is filled with CSF
Spinal cord: Posterior, anterior and lateral grey horns
Posterior: contains cell bodies and axons of interneurons and axons of incoming sensory neurons
Anterior: contain somatic motor nuclei (clusters of cell bodies of somatic motor neurons)
Lateral: contain autonomic motor nuclei (clusters of cell bodies of autonomic motor neurons)
Spinal cord: White matter in cervical to sacral segments
Since more sensory and motor tracts are present in upper segments of spinal cord than lower segments, amount of white matter decreases from cervical to sacral segments
Define sensation
The conscious or subconscious awareness of changes in the external or internal environment
Define perception
The conscious interpretation of sensations
Primarily a function of the cerebral cortex
General vs special senses
General: refers to both somatic and visceral senses
Special senses: include sensory modalities of smell, taste, vision, hearing and equilibrium/balance
Somatic senses
Arise from skin
Tactile sensations, thermal sensations, pain sensations, proprioceptive sensations
Proprioceptive sensations
Allow perception of static position of limbs and body parts and movements of limbs and head
Allow us to recognise that parts of our body belong to us (self)
Weight discrimination - ability to assess weight of an object
Visceral senses
Provide info about conditions within internal organs, e.g. pressure, stretch, hunger, temp
Sensory receptors - selectivity
Only responds vigorously to one particular kind of stimulus - responds only weakly or not at all to other stimuli
For a sensation to arise, these four events typically occur…
- Stimulation of sensory receptor
- Transduction of stimulus
- Generation of nerve impulses
- Integration of sensory input
Exteroceptors, interoceptors and proprioceptors
Exteroceptors: located at or near the external surface of body (external environment)
Interoceptors: located in blood vessels, visceral organs, muscles and nervous systems (internal environment)
Proprioceptors: located in muscles, tendons, joints and inner ear (body position, muscle length and tension, joint position and movement)
Tactile sensations
Touch, pressure, vibration, itch, tickle
Thermoreceptors
Free nerve endings that have receptive fields on skin surface
Nociceptors
Receptors for pain
Free nerve endings found in every tissue except brain
Can be activated by intense thermal, mechanical or chemical stimuli
Fast pain
Nerve impulses propagate along medium-diameter, myelinated fibres
Not felt in deeper tissues of body
Slow pain
Begins a second or more after a stimulus is applied
Gradually increases in intensity over a period of several seconds/mins
Conduct along small-diameter, unmyelinated fibres
Can occur in both skin and deeper tissues
Superficial somatic pain, deep somatic pain and visceral pain
Superficial: arises from stimulation of receptors in skin
Deep: arises from stimulation of receptors in skeletal muscles, joints, tendons, fascia
Visceral: arises from stimulation of nociceptors in visceral organs
Localisation of pain
Fast pain: very precisely localised to stimulated area
Slow pain: well localised, but more diffuse (involves large areas)
Kinesthesia
Perception of body movements
Direct vs indirect motor pathways
Direct: provide input to LMNs via axons that extend directly from cerebral cortex
Indirect: provide input to LMNs from motor centres in basal nuclei, cerebellum and cerebral cortex
Lateral vs anterior corticospinal tract
Lateral:
Corticospinal axons that decussate in medulla
Synapse with local circuit neurons or LMNs in anterior grey horn
Anterior:
Corticospinal axons that don’t decussate in medulla
Anterior white column of spinal cord
Somatic sensory pathways: Types of neurons
First-order neuron
Second-order neuron
Third-order neuron
First-order neurons
Conduct impulses from somatic receptors into brain stem or spinal cord
From the face, somatic sensory impulses propagate along cranial nerves into brain stem
From the neck, trunk, limbs and posterior of head, somatic sensory impulses propagate along spinal nerves into spinal cord
Somatic sensory pathways: Second-order neurons
Conduct impulses from brain stem and spinal cord to thalamus
Decussate in brain stem or spinal cord before ascending to ventral posterior nucleus of thalamus
i.e. all somatic sensory info from one side of body reaches thalamus on other side
Somatic sensory pathways: Third-order neurons
Conduct impulses from thalamus to primary somatosensory area of cortex on the same side
Somatic sensory pathways: Relay stations
Regions within CNS where neurons synapse with other neurons that are part of a particular sensory or motor pathway
e.g. thalamus, spinal cord, brain stem
Somatic sensory impulses ascend to the cerebral cortex via which general pathways?
- The dorsal column-medial lemniscus pathway
2. The anterolateral (spinothalamic) pathway
Where do LMNs have their cell bodies
In brain stem and spinal cord
From brain stem, axons of LMNs extend through cranial nerves to innervate skeletal muscles of face and head
From spinal cord, axons of LMNs extend through spinal nerves to innervate skeletal muscles of limbs and trunk
Why are LMNs also called the ‘final common pathway’
Only LMNs provide output from CNS to skeletal muscle fibres
Somatic motor pathways: Types of neurons
Local circuit neurons
Upper motor neurons (UMNs)
Basal nuclei neurons
Cerebellar neurons
Somatic motor pathways: Upper motor neurons
Both local circuit neurons and LMNs receive input from UMNs
Most synapse with local circuit neurons, which in turn synapse with LMNs
UMNs from cerebral cortex essential for execution of voluntary movements
Other UMNs originate in motor centres of brain stem - regulate muscle tone, postural muscles, balance
Basal nuclei and cerebellum exert influence on UMNs
Pyramidal cells
UMNs with pyramid-shaped cell bodies located in primary motor area and premotor area of cerebral cortex
UMNs: Example of a direct motor pathway
Corticospinal pathway
UMNs: Corticospinal tracts - types
Lateral corticospinal tract
Anterior corticospinal tract
Third-order sensory neurons in the posterior column-medial lemniscus pathway extend from the…
Thalamus to the somatosensory area of the cerebral cortex
Which structure involved in the production of CBF or its flow through the brain, is closest to the midbrain
Cerebral aqueduct
Where are cell bodies of motor neurons to skeletal muscles are located
Anterior grey horns
Where are cell bodies of first-order neurons in the posterior column-medial lemniscus pathway to the cortex located
Dorsal root ganglia of spinal nerves
Lesion in cerebellum
Unlike the rest of the brain, a lesion in the cerebellum affects the same side of the body
Brain: Hemisphere lateralisation - dominant hemisphere
Exner’s, Broca’s, Wernicke’s area and the SMAGLA regions only occur in the dominant hemisphere (usually left)
Spinal cord transection at level of the neck would result in…
Loss of sympathetic control over SV
Parasympathetic nerves don’t travel through brainstem
Where does the medial lemniscus convey info to and from
From gracile and cuneate nucleus (medulla) to thalamus, therefore is located in brainstem
Lesion in brainstem
Brainstem = UMN = spastic
Already decussated = other side of body
Pulmonary valve is ____ to the aortic valve
Ventral
Where are the heart sounds best heard
1st: best heard near apex of heart
2nd: best heard near base of heart
Where is the basal ganglia located
In cerebrum
The basal ganglia is rich in..
Dopamine
What is the main relay system for conducting info between the spinal cord and cerebrum
Thalamus
Where does precise location and identification of sensation occur
Cerebral cortex
Contains somatosensory cortex, where sensory info goes
Where do first order sensory neurons conduct impulses to and from
From a (encapsulated) receptor to CNS
Where do UMNs terminate and synapse with LMNs
In ventral horn of spinal cord
Corticospinal/pyramidal tract - types of neurons
Only involves UMNs - only spasticity can occur
Where are cell bodies of UMNs located
In motor cortex
