Physiology Flashcards
Structure of muscle spindle
Fluid filled capsule
Lie in parallel with extrafusal fibres
Fx of outer pigmented layer of retina
Absorb light
Prevent scatter
Support neural retina
Recycles photopigment
What do muscle fibres measure
Length and rate of change of muscle
Types of muscle spindles
Nuclear bag and chain
Afferent fibres of muscle length detecting muscle spindles
1a and ll
Afferent fibres of muscle rate of change detecting muscle spindles
1a
Efferent supply to muscle spindles
Gamma 1 = dynamic
Gamma 2 = static and nuclear chain
Structure of Golgi tendon
Lies in series with muscle fibres
Within tendon
Collagen interwoven with axons of 1b afferents
Inter neuron 1b is inhibitory and synapses with…
Alpha motor neuron of same muscle = soft landing
What are central pattern generators
Generate rhythmic pattern of motor activity with phasic sensory input
What do bursting cells do
Drive motor neurons episodic behavior (central pattern generator)
Do this by producing plateau potential
Mechanism used when walking by central pattern generators
Reciprocal inhibition of flexors/extensors
Motor neurons in cochlear come from
Superior olivary nucleus
Frequency at which cochlear Afferent fibre most sensitive
Characteristic frequency
Sound pathway
Cochlear nerve > cochlear nucleus > trapezoid body > superior olive > lateral lemniscus > inferior colliculus (sound localization) > medial gen inculcate nucleus > primary auditory nucleus
Receptors for dorsal columns
Pacinian corpuscles
Golgi tendons
Functional modules of V1
Ocular dominance columns
Orientation columns
Blobs
Neurons from substantia nigra to basal ganglia
Nigrostriatal neurons
DOPA formed from
Tyrosine
Tract from midbrain to hypo campus
Mesolimbic
Midbrain to frontal cortex
Mesocortical
Vermis output
-> fastigial nucleus -> vestibular and reticular nuclei -> descending tracts
BALNCE
Intermediate hemisphere output
Interposed nuclei (emboli form and globose) -> red nucleus and thalamus
DISTAL MUSCLES OF LIMBS AND DIGITS
Cerebrocerebellar output
Dentate nucleus -> ventrolateral thalamus -> cerebral cortex -> corticospinal
PLANNING/REHEARSAL OF MOVEMENT.
ASSESSMENT OF MOVEMENT ERRORS.
Define tonotopic mapping
Various regions of cochlear respond to different frequencies. CNVlll projects to slightly different places in CNS
How are glutamate connections strengthened
Ca/calmodulin kinase activity
Retrograde messengers
(NB need protein synthesis for long term memory)
What do NMDA receptors need to fire
Glycine, glutamate, depolarization of post synaptic neuron to release Mg
(NB no zinc)
Name and brief description of metabotrophic glutamate receptor
Diacylglycerol-inositol triphosphate
G-protein -> GTP(PLC) -> PIP2 -> DAG and IP3 = Increase Ca
Types of long term memory
- implicit (unconscious, habits)
- explicit (conscious)
Role of the hippocampus in memory
- necessary for formation of new explicit memories
- temporary storage place for memories
Stages of explicit memory storage
- encoding
- consolidation
- storage
- retrieval
Where is implicit memory stored?
In the perceptual, motor and emotional circuits
Associative learning
Pairing one stimulus with another (salivation)
Priming
Exposure to a stimulus influences a response to a later stimulus
Habituation
Decreased response to a stimulus after repeated presentations
Sensitization
Enhancement of a the response to a test stimulus
What happens at an axo-axonic synapse?
- no direct effect on the trigger zone
- control the amount of transmitter released from the presynaptic terminal
What occurs in axo somatic synapses?
Inhibitory shunting
3 types of 2nd messenger systems
- cAMP
- phosphoinositol
- GIRK (muscarinic ACh receptors) inhibitory
4 steps of chemical synaptic transmission
- synthesis and storage of NTs
- release
- interaction with receptors
- removal from synaptic cleft
NT definition
A substance released from a Neuron that affects a specific target in a specific manner
Criteria for substance to be a NT
- must be synthesised in presynaptic neuron
- present in presynaptic terminal
- if applied exogenously, has same effect
- mechanism is needs to remove it from synaptic cleft
Types of neurotransmitters
- bio amines
- purines
- amino acids
Types of neuro active peptides
- opioids
- tachykinins
- secretins
- insulins
- somatostatins
- gastrins
From where is acetylcholine released?
- somatic motor neurons
- preganglionic autonomic neurons
- postganglionic parasympathetic neurons
- a few neurons
Clinical application of atropine
Acetylcholine antagonist
- inhibits parasympathetic
- allows sympathetic
Functions of acetylcholine in basal ganglia neurons
- arousal and wakefulness
- aspects of consciousness
Management of Alzheimer’s
Acetylcholinesterase inhibitors
Pathways involving dopamine
- nigrostriatal
- mesolimbic
- mesocortical
- tuberinfundibular
Where is norepinephrine released?
- lateral tegmental area
- locus ceruleus
Diseases associated with norepinephrine
- depression
- ADHD
Where is serotonin released?
Raphe nuclei
Functions of serotonin
- mood
- control of food intake
- pain
- complex cognitive pathways
- thermoregulation
Drugs that interact with serotonin
- antidepressants
- psychedelics
- antiemetics
- anti migraine
Mechanisms of NT removal from cleft
- diffusion
- enzymatic degradation
- re uptake
How does Botox work
Destroys members of the SNARE complex needed for exocytosis of synaptic vesicles
- prevents neuro transmission
Describe the pathology in myasthenia gravis
Circulating antibodies block ACh receptors at the post synaptic NMJ
2 types of metabotropic receptors
- GPCR
- receptor tyrosine kinase
What type of receptor is NMDA
Ionotropic glutamate receptor
How does NMDA work?
Needs - glycine cofactor - ca2 - inhibited by PCP and Mg2 -
Role of NMDA R
Translate electrical signals into biochemical signals
Types of GABA receptors
A - ionotropic
B - metabotropic
Net effect of neuronl integration depends on
- location of synapse
- size of synapse
- shape of synapse
- proximity and strength of other inputs
- resting potential of the cell
Definition of reflex
Involuntary coordinated patterns of muscle contraction and relaxation elicited by peripheral stimuli
Difference between type 1a and 2 sensory fibers
1a respond to muscle change
2 fire when muscle is static
Functions of premotor cortex
- coordinates more complex movements
- planning via sensory feedback
- controls learnt motor skills
Definition of motor unit
Single LMN and the muscle fibers it innervates
Definition of motor neuron pool
Collection of LMNs that innervates a single muscle
Protanopic
No red pigment
Deuteranopic
No green pigment
Tritanopic
No blue pigment
Layers of the eye
Fibrous (cornea and sclera)
Vascular (uvea)
Internal (retina)
Action of sensory receptors
Transduction
- convert one form of energy to electrical energy
Normal CSF pressure
Less than 200 mmH2O
Addiction pathway
- drinking causes dopamine release in the reward pathway
- irreversible changes in the neural networks that control motivation and reward-related behavior
- dopamine release from terminals of mesolimbic dopamine neurons in nucleus accumbens
Where does one emotionally perceive unpleasantness?
Insula cortex and cingulate cortex
Where is Broca’s area?
Frontal lobe, anterior to primary motor cortex controlling muscles for speech
Hormonal processes at onset of parturition
- placenta signals fetal hypothal to secrete CRF
- stimulates release of ACTH from fetal pituitary gland
- stimulates release of cortisol from fetal adrenal gland (accelerates maturation of lung and increases production of surfactant)
- stimulates release of androgen DHEA (converted to estrogen by placenta)
- estrogen upregs production of gap junctions in myometrium and expression of oxytocin receptors
- increases excitability of myometrium and increases contractions
- estrogen increases prostaglandin production which induces cervical ripening
Features of Alzheimer’s plaques
- beta-amyloid deposits
- degenerating neurons with neurofibrillary tangles
- reactive astrocytes and micro glia
