molecules to nerves Flashcards
central nervous system = brain and spinal cord
peripheral nervous system = autonomic nervous system ((para)/sympathetic) involuntary and somatic (motor and sensory) voluntary
explain the basis of electrical potential generation of cells with the sodium potassium pump and how this helps neurones
- sodium potassium pump in the membrane of cells transports 3Na+ out cell and 2K+ into cell with use of ATP
- this helps to maintain high Na+ conc outside cell and high K+ conc inside cell (useful for neurones)
- preserving these differences in ion concs, helps stabilise cell membrane potential
- this function is critical for neurones to be able to fire action potentials
K+ permeability sets up potential difference across permeable membrane
explain why there is a negative potential within the cell/membrane at resting potential
- At rest most cells are more permeable to K+ due to facilitated diffusion through K+ channels
- k+ ions tend to move out of cell as conc of k+ is lower outside than inside
- large anions cannot follow so negative potential develops on inside of membrane
what is the neurones resting potential
-65mV
explain how a neurone action potential is caused
- neurotransmitter sent across the synapse binds to receptor
- this stimulates the opening of sodium and potassium channels = 2 K+ leaving and entering of Na+ and Ca2+
- the influx of positive ions into the cell (depolarisation) increases the potential from -65 to around-55mV which is the threshold potential to which the rest of the action potential is fired
- as the threshold potential is reached, it also stimulates the opening of sodium channels in the axon and this is what sets off the action potential
at what voltage does the cell begin to repolarise at
+ 20mv
what lengths do the axons of the cell body range from
1mm - 1m
what are the basic structures of a neurone
cel body
dendrites
axon
terminal branches of axon
myelin insulates axons
what are the 3 types of neurotransmitters in the central nervous system
- excitatory
- inhibitory
- neuromodulators
give some examples of excitatory, inhibitory and neuromodulator neurotransmitters
excitatory(Na+/Ca2+) = acetylcholine, adrenaline, dopamine, histamine
inhibitory (Cl- / K+) = glycine, gamma aminobutyric acid
neuromodulators = endorphins, enkephalins
each neurotransmitter can bind to multiple different receptor subtypes
what are receptor gating mechanisms
conformational changes in the receptor that occur upon ligand binding or unbinding to open or close the ion channel and affect the functional state of the receptor
- a mechanism capable of controlling the flow of information from one set of neurons to another
synaptic transmission is always UNIDIRECTIONAL
what is myasthenia and the cause of it. What is the neurotransmitter affected as a result of this.
- Myasthenia gravis affects the voluntary muscles of the body, especially those that control the eyes, mouth, throat and limbs.
- a chronic autoimmune disorder in which antibodies destroy the communication between nerves and muscle, resulting in weakness of the skeletal muscles.
- acetylcholine
what is Parkinson’s disease and the cause of it. What neurotransmitter is affected as a result of this
- a loss of nerve cells in part of the brain called the substantia nigra.
- This leads to a reduction in a chemical called dopamine in the brain.
- Dopamine plays a vital role in regulating the movement of the body.
- tremor, weakness etc
recognise what a peripheral nerve and myeline sheath looks like on microscope
what are the 6 types of function impairment
contralateral
ipsilateral
hemiplegia
hemiparesis
paraplegia
tetrapelgia
what is
contralateral
ipsilateral
hemiplegia
hemiparesis
paraplegia
tetrapelgia function impairments
contralateral = opposite side
ipsilateral = same side
hemiplegia = paralysis of one side
hemiparesis = weakness of one side
paraplegia = paralysis of lower limbs
tetraplegia = paralysis of all 4 limbs
basic motor pathway?
cortex —-> spinal cord /upper motor neurone —> lower Motor neurone —-> muscles
where 4 places would you usually find an upper motor neurone lesion
- cortex
- internal capsule
- medulla
- spinal cord
what 4 places would you usually find a lower motor neurone lesion
- anterior horn (grey matter of spinal cord)
- spinal roots
- neural plexus
- peripheral nerve
what is the difference between the paralysis experiences for an upper and lower motor neurone lesion
upper = spastic paralysis (tight and hard muscles. It can cause your muscles to twitch uncontrollably, or spasm.)
lower = flaccid paralysis (muscles to shrink and become flabby. It results in muscle weakness.)
difference between the muscle characteristics seen in upper and lower motor neurone lesion
upper = no significant muscle atrophy, not spasms/twitches
lower = significant muscle atrophy, spasms and twitches
what is hyper and hypo reflexia
Hyperreflexia happens when your muscles have an increased or overactive reflex response (twitching)
Hyporeflexia is a symptom in which your skeletal muscles have a decreased or absent reflex respons
which between upper/lower motor neurone lesions cause hyper and hypo reflexia
upper = hyper reflexia
lower = hypo reflexia
what is the babinski sign
Babinski sign occurs when stimulation of the lateral plantar aspect of the foot leads to extension (dorsiflexion or upward movement) of the big toe (hallux).
babinski sign may be present in upper but not lower motor neurone lesion
basic sensory pathway?
cortex —> thalamus —> spinal cord —> peripheral sensory fibres
what are the different regions of the spinal cord does the sensory and motor neurons pass thru?
lower motor neurones = anterior horn of grey matter
sensory neurones = lateral corticospinal tract (white matter)
what are the 3 types of axonal degeneration
- wallerian degeneration
- segmental demyelination
- axonal degeneration
what is wallerian degeneration
active process of anterograde degeneration of the DISTAL end of an axon that is a result of a nerve lesion.
what is segmental demyelination
patchy breakdown of myelin sheaths limited to individual segments with relative sparing of axis cylinders.
MS, diabetes
what is axonal degeneration
The degeneration of axons separates the neurons from their targets, therefore inducing the loss of neuronal function. For example, axonal swelling, an early sign of axon degeneration
e.g development neurodegeneration such as alzheimers
