Neuro Flashcards
Brainstem role
- Carries ascending sensory and descending motor tracts
- Breathing, consciousness, HR
Cerebellum role
Balance, coordination, posture
Thalamus role
Sensory relay info
Hypothalamus role
Homeostasis
Position and role of hippocampus and fornix
In temporal lobe
Learning, memory, spatial navigation
What occurs in the lateral ventricles?
Production and recycling of CSF
Role of caudate nucleus
Planning/execution of movement
Memory, cognition, emotion
Role of putamen
Cognition and reward
Amygdala role
Behaviour (including fear and anxiety)
Role of sub-cortical white matter
Connects cortical to sub-cortical regions
Role of cortical grey matter
Memory, thinking, problem-solving
2nd subdivisions of the brain:
Forebrain (prosencephalon): Telencephalon includes…
Diencephalon includes…
Telencephalon - Cerebral cortex, basal ganglia, limbic system
Diencephalon - Thalamus, hypothalamus
2nd subdivisions of the brain:
Midbrain (Mesencephalon)
Mesencephalon - tegmentum, tectum
2nd/3rd subdivisions of the brain:
Hindbrain:
Metencephalon includes…
Myelencephalon includes…
Metencephalon - pons, cerebellum
Myelencephalon - medulla
Cervical nerve region supplies…
Head, neck, diaphragm, arms, hands
Thoracic nerve region supplies…
Chest muscles, breathing, abdominal muscles
Lumbar nerve region supplies…
Legs and feet
Sacral nerve region supplies…
Bowel and bladder control
Sexual functions
Somatic vs autonomic nervous system
Somatic - interacts with environment (afferent- sensory from skin, muscles…, efferent - motor back to skin, muscles…)
Autonomic - regulates internal body (afferent - sensory from internal organs to CNS, efferent - motor from CNS to internal organs)
Prefrontal cortex role
Generating sophisticated behavioural options that are mindful of consequences
Specific role of inferotemporal cortex within the temporal lobe
Recognising faces and objects
How many layers of nerve cells in cerebral cortex?
6
Ventral stream of occipital lobe
Vision for identification- stream travels to temporal lobe (what does this image mean to us?)
Dorsal stream of occipital lobe
Vision for movement- stream travels to motor areas (where is it in relation to us?)
2 parts of substantia nigra (part of tegmentum)
Substantia nigra pars compacta - basal ganglia input
Substantia nigra pars reticulata - basal ganglia output
Medulla role
Contains tracts carrying signals between brain and rest of body
Low level sensorimotor control (e.g-balance)
Vital functions (e.g-sleep)
Pons role
Relay from cortex and midbrain to cerebellum
Cerebellum
Contains as many neurons as all rest of CNS
Adjusts synaptic weight to amend area and alter adjust movement
Tectum role and subdivisions
Visual/spacial and auditory frequency maps
Superior Colliculus - sensitive to sensory change (orientating/defensive movement)
Inferior Colliculus - similar but for auditory events
3 key structures of the tegmentum
The Periaqueductal Gray
Red Nucleus
Substantia Nigra
Periaqueductal Gray role (tegmentum)
Defensive behaviour, pain, repro
Red nucleus role (tegmentum)
Target of cortex and cerebellum (projects to spinal cord)
Pre-cortical motor control (in arms and legs)
Thalamus (in diencephalon) role
Specific nuclei - relay signal to cortex for all sensations (except smell)
Non-specific nuclei - role in regulating sleep/wakefulness
Relays from basal ganglia and cerebellum back to cortex
Hypothalamus (in diencephalon) role
Regulates pituitary gland
2 sub-cortical structures of cerebral cortex
Basal ganglia
Limbic system
6 structures in the limbic system
Amygdala
Hippocampus
Cingulate gyrus
Mammillary body
Septum
Fornix
Hippocampus role
Long-term and spatial memory
Amygdala role
associating sensory stimuli to emotional impact
Fornix role
C-shaped
Carries signals from hippocampus to mammillary bodies and septal nucleus
What part of the parietal lobe receives sensation from rest of body?
Post-central gyrus
General role of limbic system
Emotion, motivation, emotional association with memory
Things affecting loudness and pitch
Louder sound = greater amplitude
Higher pitch = greater frequency
Human range of hearing
20Hz - 20Khz
Presbycusis
Age related hearing loss
Pinna
Cartilagenous structure
Formed from pharyngeal arches 1 and 2
Directs soundwaves towards ear canal
Picks out high pitch sounds better than low pitch
When in utero does the pinna form?
10th-18th week
Ear canal constitution
1/3 cartilage
2/3 bone
Whats makes up middle ear?
Bones: Malleus, incus, stapes
Muscles: Tensor tympani, stapedius
Tubes: Eustachian tube
Role of middle ear
Amplification of airborne sound vibration
Area TM: Stapes = 14:1
Lever action of ossicles- handle of malleus x1.3 longer than long process of incus
Roles of muscles in middle ear
Protect inner ear from acoustic trauma
Stiffens ossicular chain
Role of Eustachian Tube
Ventilating middle air space and drainage of secretions
Vestibulocochlear apparatus includes…
Cochlear, labyrinth, vestibulocochlear nerve
Cochlea
2.5 turns fluid filled bony tube
2 openings: round and oval windows
3 compartments (scala tympani, scala media, scala vestibuli)
2 ionic fluids
Fluid in scala media of the cochlea
Endolymph (High K+)
Fluid in scala vestibuli and scale tympani of cochlea
Perilymph (Na+ rich)
Role of labyrinth in vestibulocochlear apparatus
Responsible for balance
Basilar Membrane
Narrow at base, wide at apex
Stiff at base, floppy at apex
High frequencies detected at base, low frequencies at apex
(ruler on a table)
Hair cells (stereocilia) role in organ of corti
Displacement of basilar membrane is converted to electrical signal
Inner hair cells - mechanical transduction
Outer hair cells - fine tuning
From sound waves to electric signal
Movement of stereocilia
Mechanically gated K+ channels open = depolarization (K+ rich endolymph)
Depolarization results in opening of voltage gated Ca channels
Release of neurotransmitter including glutamate
Repolarization through K+ effluc (into K+ poor perilymph)
From neuron in the ear to brain
Auditory fibre to spiral ganglion
Spiral ganglion to cohlear nerve (VIII)
Central auditory pathway
Role of brainstem in localising sound
Sound may hit R ear before L ear
Resulting in firing of neurons earlier in R ear than L ear so brain knows sound is coming from R side
Defective outer/middle ear =
Conductive hearing loss
Defective Inner ear =
Sensorineural hearing loss
Ependymal cells
Epithelial-like, line ventricles and central canal of spinal cord
Functions - CSF production, flow and absorption
Ciliated to assist flow
Allow solute exchange between nervous tissue and CSF
Choroid plexus
Projections in ventricles formed from modified ependymal cells
Highly vascularised with large SA
Main site of CSF production by plasma filtration
Primitive Reflexes
Brain stem function only which occurs in babies but is concerning when you’re older
e.g- grasping reflex of palm when something touches it
4 key elements of blood brain barrier
Endothelial cell tight junctions
Lack of BM fenestrations
Astrocytic end feet
Pericytes
Main blood supply to brain
Vertebral arteries and common carotid arteries
What connects to the superior and inferior edges of the falx cerebri?
Superior sagittal sinus
Inferior sagittal sinus
What cells line the brain ventricles?
Ependymal Cells
Feature of ependymal cells
Contain cilia to beat moving CSF along
Interstitial fluid drains into CSF via…
Perivascular channels
Lots of white matter on top of pons because…
Lots of nerve fibres travelling through
Cerebral peduncles
2 stalks that attach the cerebrum to the brainstem arising from the ventral pons
3 divisions of cerebellum
Archicerebellum
Paleocerebellum
Neo cerebellum
4 roles of limbic system and the Papez circuit
Memory
Motivation
Emotion
Fight or flight
Loss of hippocampus results in…
Inability to form new memories (don’t lose old memories)
3 main groups of nuclei in thalamus
Sensory relays
Cerebella and basal ganglia relay to motor frontal lobe
Connected to associative limbic areas of cerebral cortex
Damage to thalamus =
Sensation loss, pain, movement disorders
Amygdala initiated during…
Fight or flight
Coverings of spinal cord
Dura mater
Deep to that is arachnoid mater
Deep to that is pia mater
Variation in spinal cord travelling inferiorly
Amount of white matter decreases as there are less neurons travelling through as you go down
3 cranial nerves that move the eye
III - Oculomotor
IV - Trochlear
VI - Abducens
(moving the eye is their only role)
Diplopia
Double vision
Muscle that lifts upper eyelid
Levator Palpabrae Superiosis (LPS)
4 recti muscles in the eye
Medial Rectus
Lateral Rectus
Superior Rectus
Inferior Rectus
2 oblique muscles in the eye
Superior Oblique
Inferior Oblique
Origin and insertion of extraocular muscles
Origin - orbital bones
Insertion - The sclera (except LPS which inserts into upper eyelid)
What innervates levator palpabrae superiosis?
Oculomotor nerve and sympathetic fibres
3rd CN nerve injury results in…
Ptosis (drooping eyelid as LPS isn’t working)
What EOMs does the oculomotor nerve innervate?
LPS
Medial Rectus
Superior Rectus
Inferior Rectus
Inferior Oblique
What EOMs does the abducens nerve innervate?
Lateral Rectus
What EOMs does the trochlear nerve innervate?
Superior Oblique
Abducens nerve lesion=
Eye deviates medially
Patient experiences diplopia
Action of medial and lateral rectus
Medial and lateral movement of eye
Primary and secondary actions of superior rectus
1) elevates the eye
2) adducts and medially rotates
Primary and secondary actions of inferior rectus
1) depresses the eye
2) adducts and laterally rotates
Primary and secondary actions of superior oblique
1) medially rotates eye
2) depresses and abducts
Primary and secondary actions of inferior oblique
1) laterally rotates eye
2) elevates and abducts
Content of vestibular structure of inner ear
Utricle and saccule
3 semicircular canals
(balance)
Testing IV nerve function
Look medially then down (tests function of SO and therefore the trochlear nerve)
Fluid contained in semicircular ducts
Endolymph
Function of semicircular ducts
Movement of endolymph causes cupula and hair cells in the ampulla to bend in the opposite direction sending info to brainstem via VIII (vestibulocochlear) nerve
This info reaches medulla and controls posture, balance and conscious awareness of position
Oculocephalic Reflex (and testing it)
Maintaining fixed gaze when head is moving as when head rotates, eyes move in opposite direction
Therefore, this reflex can be tested to assess vestibular apparatus and brainstem (absence of reflex could indicate brainstem lesion)
Orbitofrontal cortex role
Appraisal
Medially - Activates reward
Laterally - Activates punishment
Amygdala role
Appraisal
Older brain
Role in appraisal but overshadowed by OFC
Responds to harmful stimuli but slower than OFC
Anterior Cingulate cortex role
Supracallosal - processes punishment data from lateral OFC
Pregenual - processes reward data from medial OFC
Posterior Cingulate cortex role
Input from parietal lobes
Output to hippocampus
Mid Cingulate cortex role
Output to premotor areas (e.g - SMA)
Sensation
Mental process resulting from immediate external stimulation of a sense organ
Perception
Ability to become aware of something following sensory stimulation
Factors that determine how you perceive your environment (perceptual set)
Context
Culture
Expectations
Mood and Motivation
Bottom-up vs top-down processing
Bottom-up - Sensation and perception essentially the same
Top-down - Processing sensation and perception are separate (reflex to being jump scared)
Illusion
Misinterpreted perception of a stimulus
Hallucination
Experiences involving apparent perception of something not present
Sylvian Fissure
Same as lateral sulcus
2 main sulci of parietal lobe
Postcentral sulcus
Intraparietal sulcus
What does DTI (diffusion tensor imaging) (form of MRI) show?
Images of white matter tracts within CNS
3 layers of eye
Outer layer - sclera and cornea
Middle layer - uvea
Inner layer - retina
Sclera structure
Tough fibrous outer coat made of collagen
What is the cornea made from?
Collagen
Neuro-fibre compartment of the eye
Retina - extension from the brain
2 roles of outer eye layer
Transparent for light transmission
Tough - barrier to infection
Components of middle eye layer
Choroid, Iris, Ciliary body
5 layers of outer eye
Epithelium
Bowman’s layer
Stroma
Descemet’s layer
Endothelium
Ciliary body of eye
Glandular epithelium produces aqueous humour ciliary (smooth) muscle controls accommodation
Choroid of eye
Blood supply to outer 1/3 of retina
Components of inner eye layer
Retina - Specialised organ for phototransduction (many layer)
Structures within retina
Macula lutea
Fovea centralis
Cones
Rods
Hypermetropia
Underpowered to focus near objects on retina
Due to: corneal curvature too shallow, lens not flexible enough, axial length of eyeball too short
Myopia
Overpowered so can’t focus far objects on retina
Due to: corneal curvature too deep, axial length of eyeball too long
Outer eye responsible for ____ refractive power of eye
2/3
Lens responsible for ___ refractive power of eye
1/3
4 neuron cell types
Multipolar neuron (1 axon, lots of dendrites)
Bipolar neuron (1 axon, 1 dendrite)
Pseudo-unipolar neuron (1 branched axon)
Unipolar neuron (1 neutrite extending from cell body)
Permeability of neuron cell membrane
Semi-permeable
K+, Cl- cross readily
Na+ crosses with some difficulty
Large protein anions can’t cross
2 forces determining ion distribution in neurons
Diffusion
Electrostatic pressure
Sodium-Potassium pump
Pumps 2 K+ in for every 3 Na+ out which maintains the -70mV resting potential
Excitatory neurotransmitters
They depolarise membrane increasing chance of an AP being generated (= excitatory post synaptic potential (EPSP))
Inhibitory neurotransmitters
Hyperpolarise the membrane decreasing chance of AP being generated (= inhibitory post synaptic potential (IPSP))
Synaptic transmission
Neurotransmitters activate receptors on dendrites
Receptors open ion channels
Ions cross membrane changing membrane potential
Potential changes spread through cell
If potential changes felt at axon hillock are large enough, AP generated
Threshold value for generation of action potential
~-60mV
How neurotransmitter enters synapse
Ca2+ channels open when AP reach pre-synaptic cleft
Ca2+ cause vesicles to move to release sites, fuse with cell membrane and release their contents
Inner 2/3 of retina supplied by…
Central retinal artery
Outer 1/3 of retina supplied by…
Choroid (post ciliary arteries)
IASP definition of pain
Pain is an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage
Acute pain
Pain <12 weeks duration
Chronic pain
Continuous pain lasting >12 weeks
Pain that persists beyond tissue healing time
Classified as chronic non-cancer and chronic cancer pain
Nociceptive pain
Pain arising from actual/threatened damage to non-neural tissue and is due to the activation of nociceptors.
Neuropathic pain
Pain caused by legion/disease of somatosensory nervous system
Nociplastic pain
Pain arising from altered nociception despite no clear evidence of actual or threatened tissue damage causing the activation of peripheral nociceptors, or evidence for disease or lesion of the somatosensory system causing the pain
Allodynia
Pain due to a stimulus that doesn’t normally provoke pain
Dysesthesia
Unpleasant abnormal sensation, whether spontaneous/evoked
Hyperalgesia
Increased pain from stimulus that normally provokes pain
Hypoalgesia
Diminished pain in response to a normally painful stimulus
Nociceptors
Peripheral receptors of pain system turning physical stimulus -> AP
Nociceptors are the free nerve endings of primary afferent neurons which are?
A-delta fibres
C fibres
Found in any area of body that can sense pain externally or internally
Cell bodies of these neurons found in dorsal root ganglion and trigeminal ganglion
Dorsal root ganglion
Present in dorsal root
Composed of cell bodies of nerve fibres that are sensory (afferent)
First order neurons
Pseudo-unipolar neurons
Nerve fibre type: A-alpha
Carry proprioception info
Myelinated
Nerve fibre type: A-beta
Carry touch info
Myelinated
Nerve fibre type: A-delta
Pain (mechanical and thermal)
Myelinated
Nerve fibre type: C
Pain (mechanical, thermal, chemical)
Non-myelinated
Purpose of pain
Immediately: warning to withdraw from source of tissue damage
Later: encourages us to immobilise injured area giving damaged tissue best chance to heal
What is depression?
Low mood, anhedonia, low energy
Biological symptoms - poor sleep, poor appetite, reduced libido, poor concentration
Cognitive symptoms - worthlessness, guilt, hopelessness, suicidal thoughts
Depression effect on hippocampus
Hippocampus function in memory
Reduces size (up to 20%)
More depressive episodes = greater hippocampus size loss
Much of this loss is irreversible
Stress effect on neurogenesis
Reduces neurogenesis
Stress reduces brain derived neurotrophic factor (BDNF) (reversed with antidepressants)
Lowest levels in post-mortems of successful suicide victims
Motor unit
An alpha motor neuron and ALL the muscle fibres it innervates
Less muscle fibres innervated by a motor neuron =
Greater variation in movement (fingertips)
Alpha motor neurons located laterally control…
More distal muscles
Alpha motor neurons located medially control…
More proximal muscles
Muscle tone is…
Degree of contraction of a muscle or the proportion of motor units that are activated at one time
UMNs are…
Neuron whose cell body originates in cerebral cortex / brainstem and terminates within brainstem / spinal cord
LMNs are…
Multipolar neuron connecting UMN and skeletal muscle it innervates
Cell body in ventral horn of spinal cord or in brainstem motor nuclei
2 types of LMN
Alpha-motor neurons: cause contraction of muscle fibres
Gamma-motor neurons: regulation of muscle tone and maintaining non-conscious proprioception
Neuromuscular junction
AP in motor neuron arrives at axon terminal and depolarises plasma membrane
Voltage-gated Ca2+ channels open and Ca2+ diffuse into axon terminal
Ca binds to proteins allowing ACh vesicles to fuse with presynaptic membrane
ACh diffuses to motor end plate binding to cholinergic nicotinic receptors
Opens ion channel in receptor protein resulting in more Na+ moving in than K+ moving out = end-plate potential generated
What happens to ACh in the synaptic junction after it has stimulated the motor plate?
It’s broken down by acetylcholinesterase and recycled in axon terminals
A skeletal muscle comprises several…
A …… is constituted of several …….
…. contain protein filament: …. and …..
Muscle fasciculi
Muscle fasciculus
Myofibrils
Myofibrils
Actin and Myosin
The Motor Pool
All the LMNs that innervate a single muscle (containing alpha and gamma motor neurons)
Motor pools often rod-like shape within ventral horn of spinal column
Reflex
Operate without engaging brain
Critical for avoidance of injury and effective motor control
Homunculus representing the motor cortex
Oversimplifies - damage to single finger area doesn’t mean loss of voluntary control of that finger (representations should overlap)
This is because few motor commands require isolated activation of a single motor unit
Somatic vs Autonomic Nervous System
S: Conscious/voluntary regulation
Fibres don’t synapse after they leave the CNS (single neuron from CNS to effector organ)
Innervates skeletal muscle fibres, always stimulatory
A: Involuntary
Fibres synapse once at a ganglion after they leave CNS
Innervates smooth muscle, cardiac muscle, glands (either stimulates or inhibits)
What are the 2 main output within the parasympathetic nervous system?
Vagus nerve to thorax and abdomen
Sacral outflow to Pelvic organs
Neurotransmitters at autonomic motor neurons
ACh at ganglion
ACh or NE at effector
Neurotransmitters at somatic motor neuron
ACh at effector
3 components of ANS
-Parasympathetic
-Sympathetic
-Enteric NS
Adrenal Medulla (Fight or Flight)
Adrenal gland secretes adrenaline and noradrenaline (secretion stimulated by sympathetic trunk) triggering fight or flight (vasoconstriction etc.)
Enteric Nervous System
Works independently from ANS
Consists of a mesh-like system of neurons that governs the function of the gastrointestinal tract
There are sympathetic receptor subtypes (alpha1, alpha 2, beta 1…. etc) which is important because…
Different receptors can be targeted to target specific organs (beta 2 receptors found in lungs)
Carotid body found…
Bifurcation point between Internal and External Carotid Artery
ANS Parasympathetic Outflows
CN 3,7,9,10
S1, S2
ANS Sympathetic Outflows
-CNs to eye
-Sympathetic Chain
-Other Ganglia
-Adrenal amplification (fibres in white and grey rami communicantes, splanchnic nerves to large thoraco-abdominal plexi)
Non Cardiovascular ANS Measurement (5)
Pupillometry
Sweat measurement
Skin blood flow (thermoregulation)
Gastric acid secretion
Sexual function
Easiest way to measure ANS
HR and BP
Associated nuclei of basal ganglia
Caudate Nucleus
Putamen
Globus pallidus
Subthalamic nucleus
Substantia nigra
Pedunculopontine nucleus
What is within the lenticular nucleus in the basal ganglia?
Putamen and globus pallidus
What is within the Striatum (Neostriatum) in the basal ganglia?
Caudate nucleus and putamen
What is within the Corpus striatum in the basal ganglia?
Caudate nucleus
Putamen
Globus Pallidus
Axons from the primary motor cortex project through what to through the spinal cord?
Anterior horn of spinal cord (here it synapses to the LMN which carries the impulse to the muscle)
Connection between nerve and muscle is called…
The neuromuscular junction
In reflexes, what connects sensory and motor neurons in the spinal cord?
The interneuron
Path of motor neurons from spinal cord
Axons project from anterior grey matter of spinal cord -> plexus -> muscle
Major events in neuromuscular transmission
-Motor neuron depolarises so AP travels down to NMJ
-Depolarisation of axon terminal = Ca2+ channels open = Ca2+ influx = fusion of vesicles and ACh release
-ACh binds to post-synaptic receptor located on muscle fibre at motor-end plate
-Results in cation entry locally depolarising the sarcolemma
-Sarcolemmal depolarisation = opening Na+ channels = Na+ influx = depolarisation of sarcolemma travelling to t-tubules
-Results in release of Ca2+ from sarcoplasmic reticulum (contraction)
What inactivates ACh in the synaptic cleft after contraction of muscle?
Acetylcholinesterase (AChE)
Skeletal muscle make up
Muscle cell = muscle fibre
Muscle fibres made of myofibrils
Myofibrils made of sarcomeres
Basal Ganglia impact on muscle movement
-Motor cortex supplies input to both basal ganglia and reticular formation
-Fibres travel from reticular formation to spinal cord for muscle contraction
-Basal ganglia has a damping effect on reticular formation making sure muscle contraction is controlled (this damping effect is absent in patients with Parkinson’s)
2 subgroups of the basal ganglia are…
The rostral (upper) part
The caudal (lower) part
What is contained within the rostral part of the basal ganglia?
Striatum - putamen and caudate
Globus pallidus - internal and external segment
What is contained within the caudal part of the basal ganglia?
Subthalamic nucleus
Substantia nigra
3 different circuits in the basal ganglia
Motor circuit
Limbic circuit
Oculomotor circuit
Simplified Parkinsons
Increased muscle tone and reduced movements (not enough dopamine)
Simplified Huntington’s
Decreased muscle tone and overshooting movements (too much dopamine)
Synthesis of dopamine
L-Tyrosine -> L-DOPA -> Dopamine (2 enzymatic steps)
Where is dopamine stored?
Presynaptic cleft
Dopamine receptors on postsynaptic membranes
D1, D2, D3, D4, D5
Where is dopamine produced?
Where does it go from there?
Substantia nigra and then it goes up to the striatum
Parkinson’s is due to pathology in…
Huntington’s is due to pathology in…
Substantia nigra (mainly)
Striatum
Cortex vs Basal Ganglia role in movement
Cortex - Desire to move is generated along with motor execution
Basal Ganglia - Facilitation and integration of fine tuning movements
Motor loop simplified
Cortex -> Basal Ganglia -> Cortex -> Movement
Agonist and antagonist neurotransmitters of the motor loop
Dopamine from the substantia nigra stimulates the motor loop
GABA from the striatum inhibits the motor loop
Somatic vs Psychological Stress
Somatic - Associated with damage to body tissue (pain/inflammation)
Psychological - Emotional strain/tension often involving anticipation
Eustress vs Distress
Eustress - beneficial and motivating (striving for a goal within reach)
Distress - negative stress (when a challenge isn’t resolved by coping/adaption)
Sympathomedullary pathway response to stress
Hypothalamus activates adrenal medulla
Adrenal medulla (controlled by ANS) releases adrenaline and noradrenaline into bloodstream
Which both reinforce sympathetic activation (increased HR and BP) which produces more energy
Pituitary-adrenal system response to stress
Higher brain centres activate hypothalamus which release corticotrophin (CRF)
Triggers pituitary to release adrenacorticotrophic hormone (ATCH)
Triggers adrenal cortex to release corticosteroids
Corticosteroids trigger liver energy release and immune system suppression
When is ACh used in parasympathetics?
Pre and post ganglionic neurones
When is ACh used in sympathetics?
Only pre ganglionic neurones
Retinal blood supply
Choroid (posterior ciliary arteries) supply outer 1/3 of retina
Central retinal artery supplies inner 2/3
Rods (low light) and cones (bright light) of the retina
Outer segment contains discs containing light sensitive photopigment
Inner segment made up of cell body, axon, synaptic terminals
Phototransduction - absorb light and send electrical signal
Photopigment in cones
Opsin - transmembrane proteins containing light sensitive molecule retinal
Different opsin structures mean retinal absorbs different wavelengths of light (different colours)
Photopigment in rods
Rhodopsin
Photon effect on rhodopsin
Triggers change in rhodopsin structure triggering a cascade in the cell
Which fibres of optic nerve cross at optic chiasm?
Nasal retina fibres cross
Temporal retina fibres do not
3 subdivision of ANS
Sympathetic
Enteric (GI)
Parasympathetic
Difference in neuron number between somatic and autonomic
2 in autonomic
1 in somatic
Parasympathetic bronchoconstriction
Vagus nerve neurons terminate in parasympathetic ganglia in airway cell
Short post-synaptic nerve fibres reach muscle releasing ACh which acts on muscarinic
Saltatory Conduction
Decremental conduction between nodes but very fast along axon
Most CNS neurons are myelinated
When AP reaches terminal button…
Ca2+ channels open and Ca floods into terminal button causing exocytosis of neurotransmitter containing vesicles into the synaptic space
What breaks down ACh in the synaptic space?
Acetylcholineesterase (AChE)
A collection of several muscle fibres (muscle cells) is called a…
Muscle fasciculus
A muscle fibre is constituted of several …. which contains…
Myofibrils which contain protein filaments: actin and myosin myofilaments
Action of ACh in actin-myosin contraction
ACh triggers release of Ca from inside the muscle cell causing myosin head to change shape so it can bind to actin (ATP is then required to break the bond between myosin head and actin)
What causes greater movement resolution in a motor unit?
An alpha motor neuron innervating a smaller number of muscle fibres (like those innervating finger tips)
What comprises a motor unit?
A single alpha motor neuron (LMN) and all the muscle fibres it innervates
How is increased power in contraction of muscle achieved?
Increasing the number of alpha motor neurons firing as each 1 innervates a clump of muscle fibres
3 muscle fibre types
Fast fatigable
Fast fatigue-resistant
Slow
Effect on exercise on muscle fibres
Increases thickness of muscle fibres
Change in muscle fibre types
The Motor Pool
All the motor neurons that innervate a particular muscle
Arrangement of alpha motor neurons in the spinal cord
Cell bodies of neurons innervating more proximal muscles lie more centrally
Cell bodies of neurons innervating more distal muscles lie more laterally
What senses tension in muscles?
Golgi tendon organs in the tendons (sends ascending sensory info to brain)
What detects stretch in muscles?
Muscle spindles
Extrafusal vs Intrafusal muscle fibres
Extrafusal - Provide force (being a muscle)
Intrafusal - Bound to muscle spindle (sensory device to detect stretch/length of muscle)
System to detect stretch regardless of the current muscle length
If intrafusal fibres are controlled by same motor neurons as extrafusal, when muscle is slack, system won’t be sensitive to slight changes
So, intrafusal are innervated separately by gamma motor neurons which keep intrafusal at a set length that optimise muscle stretch detection
2 main motor tracts
Dorsolateral tracts (corticospinal and corticorubrospinal)
Ventromedial tracts (corticospinal and cortico-brainstem-spinal)
Dorsolateral tracts routes and innervation
Has a direct corticospinal route and an indirect route via red nucleus
Innervates contralateral side of 1 segment of spinal cord
Projects to distal muscles (fingers)
Ventromedial tracts routes and innervation
Has a direct corticospinal route and an indirect route via tectum, vestibular nuclei, reticular formation and CN nuclei
Diffuse innervation projecting to both sides and multiple segments of spinal cord
Projects to proximal muscles (trunk)
Cerebellum input to motor cortex
Adjusts the amount of excitatory input to motor cortex
Adjusts motor command by accounting for your actual body position and movement
Basal ganglia input to motor cortex
Adjusts the amount of inhibitory input to motor cortex
Receives excitatory input from motor cortex (motor plans) then stimulates inhibition via the thalamus
Inputs and Outputs of Cerebellum
Inputs: Spinal Cord, Cerebral Cortex (via Pons), Vestibular System
Outputs: Motor Cortex (via Thalamus)
The HPA axis
Hypothalamus secretes Corticotropin Releasing Hormone (CRH)
CRH stimulates Anterior Pituitary to releas Adrenocorticotropic Hormone (ACTH)
ACTH travels in blood to stimulate the Adrenal Cortex to release cortisol (stress hormone for fight or flight)
Cortisol also then provides -ve feedback to Hypothalamus and Anterior Pituitary (binds to receptors)
Oxytocin and Vasopressin are synthesised in the… and secreted from the…
Hypothalamus
Posterior Pituitary Gland
Which nuclei contain neurones that synthesise Oxytocin and ADH?
Paraventricular nucleus (primarily oxytocin)
Supraoptic nucleus (primarily ADH)
Development of anterior and posterior pituitary
Anterior - originates from tissue in roof of mouth - ectoderm
Posterior - formed from floor of IIIrd ventricle (neuro tissue)
What regulates ADH release?
Osmoreceptors in hypothalamus
Baroreceptors
Process of light converging onto optic nerve
Photoreceptors stimulated and signal to retina moves through a ganglion cell layer where millions of fibres then converge to become the optic nerve
Blood supply and drainage of inner retina
Inner 2/3 retina supplied by central retinal artery which branches into superior/inferior/temporal/nasal branches
Drained by branch retinal veins -> central retinal vein -> opthalmic vein -> cavernous sinus –> IJV
Phototransduction
11-cis-retinal -> all-trans-retinal when hit by photons of light
It is then regenerated
Anterior segment of eye contains…
Aqueous humour - nutrition to lens and cornea, maintaining intraocular pressure
Posterior segment of eye contains…
Vitreous humour - Viscoelastic gel (thicker than aq humour)
Adnexae of the eye
Lids
Conjunctiva (palpebral and bulbar)
Tear film (3 layers - lipid, aq and mucin)
Arterial supply of eye
Internal carotid artery -> opthalmic artery (branches to supply different regions of the eye)
External carotid artery -> facial artery -> angular artery
Blood supply and drainage of outer 1/3 of eye
Supplied by choroid (posterior ciliary artery -> choroidal artery -> choriocapillaris)
Vortex veins drain the choroid
Superior drain into superior opthalmic vein (SOV), inferior drain into inferior opthalmic vein (IOV)
Superior opthalmic veins drain directly into…
Cavernous sinus
Inferior opthalmic veins drain into…
Pterygoid venous plexus
Names of the 3 cerebellum divisions
Archicerebellum
Paleocerebellum
Neo cerebellum
What is Archicerebellum role?
The flocoulonodular lobe:
Balance
What is Paleocerebellum role?
Muscle tone and posture
What is Neo cerebellum role?
More fancy movements, coordination, muscle tone
What connects corpus callosum and fornix?
Septum pellucidum
What do the interventricular foramen connect?
2 holes connecting the L and R lateral ventricles to the anterior portion of the IIIrd ventricle
3 inputs to hypothalamus
Amygdala
Hippocampus
Circulating Blood
5 hypothalamus outputs
Limbic System
Pituitary
ANS
Reticular Formation
Thalamus
