Neuro Lectures Flashcards
What does pupil diameter change in response to?
- Changes in light intensity
- Proximity of object
- State of arousal (sympathetic NS)
Name afferent limbs of eye
Retina (photosensitive ganglion cells), Optic Nerve, Decussation at chiasm (stimulation of one eye therefore causes pupil response in both eyes), Optic Tracts
Name efferent limbs of eye
Edinger-Westphal Nucleus in mid brain, Parasympathetic fibres in 3rd CN, Synapse in ciliary ganglion in orbit, Short ciliary nerves innervate sphincter muscle
Define Tracts
Location of a pathway e.g. spinothalamic tract
Define Commissures
Tract connecting one hemisphere to the other e.g. anterior commissure
Define Lemnisci
Narrow strip of fibres e.g. medial lemniscus
Define Funiculi
‘rope’ or ‘cord’ e.g. lateral funiculus
Define Fasiculi
‘bundle’ e.g. gracile fasiculus
Define Capsule
Sheet of white matter fibre that borders a nucleus of grey matter
Define Column
Longitudinally running fibres that are separated by other structures e.g. dorsal column
Define White Matter
The paler tissue of the brain and spinal cord, consisting mainly of nerve fibres with their myelin sheaths
Define Grey Matter
The darker tissue of the brain and spinal cord, consisting mainly of nerve cell bodies and branching dendrites
Define cortex
Laminated grey matter on outside of brain, e.g. motor cortex
Define Nuclei
Collections of nerve cell bodies within the CNS e.g. arcuate nucleus
Define Ganglia
Collections of nerve cell bodies outside the CNS (e.g. dorsal root ganglia) and some in CNS that have a capsule (e.g. basal ganglia)
Define Afferents
Axons taking information towards the CNS e.g. sensory fibres
Define Efferents
Axons taking information to another site e.g. motor fibres
Define Reticular
‘Netlike’ - where grey and white matter mix e.g. reticular formation of brainstem
Define Coronal Plain (vertical/frontal)
Parallel with coronal suture
Name the horizontal plane
Axial
Define Sagittal (parasagittal)
Parallel with sagittal suture
Define Ipsilateral
Same side [of brain]
Define Contrallateral
Opposite side
Define Medial
Towards midline
Define Median
at midline
Define Lateral
away from midline
Define Rostral
Towards nose/anterior
Define Caudal
Towards tail/posterior
In brain stem and cord, define Dorsal
Posterior
In brain stem and cord, define Ventral
Anterior
In cerebrum, define Dorsal
Superior (as folds in embryology from posterior position)
In cerebrum, define Ventral
Inferior (as folds in embryology from anterior/ventral)
Define Sulci
Grooves
Define Gyri (Gyrus)
Ridges
Functions of ‘Control and Command centre’ in the brain
- Receives sensory information (conscious and subconscious)
- Provides motor output (conscious and subconscious)
- Integration
Parts involved in consciousness
Thought, Emotion, Memory, Planning etc
Where is the motor cortex
Pre-central gyrus
Where is the sensory cortex
Post-central gyrus
Characteristics of the frontal lobe
-Voluntary movement on opposite side of body
-Frontal lobe of dominant hemisphere controls speech and writing
-Intellectual functioning, thought processes, reasoning, memory
(-Also contains Inhibitory centres regarding thought processing/reasoning)
Characteristics of Parietal Lobe
Receives and interprets sensations, including pain, touch, pressure, size, shape and body-part awareness
Characteristics of Temporal Lobe
Understanding spoken words, sounds as well as memory and emotion. (Damage here means can still hear words but not understand them)
Characteristics of Occipital Lobe
Understanding Visual images and the meaning of written words
What directly underlies the cortex
White Matter
Give examples of grey matter structures deep in the white matter surrounding the ventricles
- Thalamus
- Hypothalamus
- Basal Ganglia (Caudate nucleus, Putamen, Globus Pallidus)
Role of Thalamus
Relay centre directing inputs to cortical areas
Role of Hypothalamus
ANS links endocrine system to the brain - homeostasis
Role of basal ganglia
Motor control, cognition and non-motor behaviour
Role of cerebellum
Involved in the co-ordiantion of voluntary motor movement, balance and equilibrium and muscle tone.
(Co-ordinates movement and balance)
Describe location of cerebellum
- Lies over dorsal surface of brain stem and attached by 3 peduncles (Superior, Middle, Inferior)
- IVth ventricle (forms part of its roof) separates dorsal brainstem
What separates the cerebellum from the dorsal brainstem
IVth ventricle (forms part of its roof)
What makes up the cerebellum
Made up of folded cortex, white matter and deep inner nuclei. Cortex is folded into many transverse folia.
Results of cerebellar injury
Movements that are slow and uncoordinated such as:
- Loss of coordination of motor movement (asynergia)
- Movement tremors (intention temor)
- Weak muscles (hypotonia)
- Abnormal eye movements (nystagmus)
Functions of the brainstem
- Special senses
- Sensory and motor [innervation?] for head and neck via cranial nerves
- Autonomic regulation of the body
- Regulates Consciousness
- Pathway between brain and spinal cord
Name parts of the brain stem
- Midbain
- Pons (bridge to the cerebellum)
- Medulla oblongata (continuous with the cord)
Describe the midbrain (parts)
Midbrain surrounds cerebral aqueduct. Made up of Tectum (superior and inferior colliculi) and Cerebral peduncle (tegmenjtum and crus cerebri)
What are 2 types of specialised cell in the CNS
- Nerve cells/neuron(es); many types e.g. pyramidal, stellate, basket, Golgi, Purkinje, chandelier etc.
- Neuroglia; e.g. astrocytes, oligodendrocytes, microglia, (ependyma)
What is sound?
The displacement of air particles following a sinusoidal pattern of compression and rarefacation
In sound what is affected by amplitude and frequency of a wave?
Amplitude (height of wave) refers to volume (how loud)
Frequency refers to pitch
What is average human range of hearing?
20Hz - 20kHz
What are main mediums sound travels through in inner, middle and outer ear?
Inner - fluid
Middle - air
Outer - air
What structures make up the outer ear
Pinna (cartillagenous structure) and ear cannal
In embryology, what forms the outer ear and when in development does this happen?
Formed from the pharyngeal arches 1 and 2 (6x Hillocks of His).
Formed between 10th and 18th week in utero
What is the purpose of ear folds and pinna
direct sound waves towards the ear canal
What is the ratio of cartilage to bone in ear canal?
Cartilage - 1/3
Bone - 2/3
Therefore ratio of 1:2 respectively
The outer ear also comprises the ear drum - what is the proper term for this and how large is it
Tympanic Membrane
8x10mm diameter, 14mg, 84-55mm^2
Which bones make up the middle ear
Malleus, Incus & Stapes (in that order from outer to inner ear and in order of size)
What muscles make up the middle ear
Tensor Tympani & Stapedius
Which tubular structure also comprises the middle ear?
Eustachian Tube
Whats the role of the middle ear?
Acoustic impedance match between air and fluid- filled inner ear.
Amplification of the airbone sound vibration to make sound louder (as energy loss from air to fluid):
Ratio Area Tympanic M : Stapes 14:1
Lever action of ossicles - handle of malleus is 1.3 times longer than long process of incus
Total gain 18.3:1 or 20 - 35 dB
What is the fold increase in pressure from TM to inner ear?
200 fold increase down ossicular chain
What are the role of the muscles in the middle ear?
Protection of the inner ear from acoustic trauma and stiffens the ossicular chain
(Stapedius stimulated acoustically)
In a man what is the average reaction time to a thunderclap (not shotgun)?
25ms
Which muscle of middle ear undergoes voluntary and involuntary control?
Tensor Tympani
What is the role of the Eustachian Tube?
Ventilation of the middle ear space and drainage of secretions.
What is the inner ear and what is another term for it?
Vestibulocochlear apparatus
A set of fluid filled sacs encased in bone.
Describe the cochlear
In inner ear - responsible for hearing. 2.5 turns fluid filled bony tube. 2 openings (round + oval window). 3 compartments. 2 Ionic fluids
Name the 3 compartments of the cochlear
Scala Tympani
Scala Media
Scala Vestibuli
What innervates the inner ear
Vestibulocochlear nerve
What (in the inner ear) is responsible for balance
Labyrinth
What are the 2 cochlear fluids
- Endolymph (High K+)
- Perilymph (like ECF and CSF, is Na+ rich)
In cochlear, what maintains the concentration gradient?
- Na/K-ATPase
- NKCC1 CIC-K chlorine channels
What can result from ion channel abnormalities?
Deafness
Describe the basilar membrane of the cochlear
Narrow at base and Wide at apex
Stiff at base and Floppy at apex
High frequencies detected at base and Low frequencies at apex
In organ of Corti describe the mobility of the membranes
Tectorial membrane - fixed
Basilar membrane - mobile
Displacement of the basilar membrane causes movement of specialized mechanical transducing cells
–Base attached to basilar membrane Stereocillia anchored to tectorial membrane
Describe briefly the hair cells of inner ear
Inner Hair Cells- Mechanical transduction
Outer Hair Cells- fine tuning
Also base attached basilar membrane and stereocilia (shearing forces here) anchored to tectorial membrane.
Describe to process of how sound wave changes to to nerve impulse (from inner ear)
-Movement of the sterocilia
(-Rapid response required)
-Mechanically gated K+ channels opened causing depolarisation (K+ rich endolymph)
-Release of neurotransmitter - Glutamate (and others)
-Repolarization through K+ efflux (into K+ poor perilymph)
How do outer hair cells of inner ear work?
Outer hair cells can alter the stiffness of the basilar membrane to ensure maximal stimulation at one site and dampened response at another. This increases resolution.
How is sound information encoded?
Frequency (pitch) - encoded in nerves by location along the basilar membrane
Intensity (loudness) - encoded in nerves by numbers responding and by firing rate.
-Sound Transduction by Inner Hair Cells (and OHCs), Amplification by outer hair cells.
Briefly describe the path from the auditory fibre to brain
Auditory fibre of spiral ganglion. Spiral Ganglion to Cochlear nerve (VIII). Via Central Auditory Pathway of brain.
Describe the Central Auditory Pathway of brain
Cochlea via VIIIth nerve to cochlear nucleus -> superior olive. (Bilateral central auditory pathway; Binaural stimulation occurs at superior olive and all regions above.)
Goes to lateral leminiscus to Inferior colliculus to medial geniculate body to auditory cortex.
What are MSO neurons
Coincident detectors that respond only when excitatory signals arrive simultaneously. Anatomical differences in connectivity allow each MSO neuron to be sensitive to sound source from particular location - ‘localising sound’
in hearing loss, what is a defective inner ear referred to as?
Sensorineural Hearing Loss
What does ‘conductive hearing loss’ refer to?
Defective outer/middle ear
Define Pain (IASP)
an unpleasant and emotional experience associated with actual or potential tissue damage or described in terms of such damage.
(subjective sensation)
What is the minimum time for pain to be considered chronic?
12 weeks
Define Nociceptive Pain
Pain that arises from actual or threatened damage to non-neural tissue and is due to activation of nociceptors - can sense internal or external pain.
Define Neuropathic Pain
Pain initiated or caused by a primary lesion or dysfunction of NS
Define Pain (NeuPSIG)
Pain arising as a direct consequence of a lesion or disease of the somato-sensory system.
How is disease differentiated by pain?
Disease differentiates pain caused by neuroplastic changes in response to strong nociceptive stimulation
Define Nociceptors
Sensory neurons that are found in any area of the body that can sense pain either externally or internally. Most are poly-modal (thermal/chemical/mechanical)
What is dorsal root ganglion composed of?
Cell bodies of nerve fibres that are sensory (afferent)
Describe Nociceptor transduction
Peripheral terminals of nociceptors have numerous different types of transducers/receptors present. These can be selectively activated by a wide range of noxious mechanical, thermal and chemical stimuli. If stimulus is stimualtes a t/r, generator potential occurs. If gp causes sufficient (threshold) depolarisation of peripheral nerve membrane, an afferent volley of APs are generated which travel up axon to central dorsal horn.
When reaches central terminal of the nociceptor, it results in the release of synaptic transmitters including Glutamate (amino acid) and substance-P/CGRP (peptides)
A beta lacks peptides, C-fibres contain both.
What are neurotransmitters in nociceptive conduction
glutamate and substance-P/CGRP
Do Prostaglandins cause pain?
Prostaglandins by themselves don’t cause pain but lower the threshold of C fiber nociceptors. Therefore lower concentrations of bradykinin and histamine are required to activate the nociceptor.
In what case would peripheral terminals of small diameter neurons be excited
In conditions of tissue inflammation as example where peripheral terminals are excited by a wise range of endogenous chemical mediators.
Case of primary hyperalgesia
How are characteristics of receptors changed inside a cell so that they are more receptive or reactive?
Phosphorylation
Whats the role of the insular cortex
plays a role in perception, motor control, self awareness and interpersonal experience
may play a part in addiction
Where is the cingulate cortex and what is it associated with?
- located in the medial aspect of the cerebral hemispheres
- intricately linked with limbic system associated with emotion formation and processsing, learning and memory.
