Cellular physiology Flashcards
What are the main functions of bipolar neurones?
- Specialised sensory functions
What is the main function of multipolar neurones?
motor neurones
What’s the resting membrane potential of neurones?
-70mV
How is the membrane potential calculated?
Nernst Equation
How is an action potential triggered?
1) Stimulus to resting membrane
2) Gate threshold reached at -55mV
3) All or nothing action potential & depolarisation
4) Opens fast Na channels = +30mV
5) Na+ channels close and K+ channels open leading to repolarisation
6) Slight overshoot due to K+ conductance = hyperpolarization
Which fibres are myelinated & unmyelinated?
M: A & B fibres
UM: C fibres
What is the function of Aa nerve fibres?
Somatic motor
Proprioception
What is the function of Ab nerve fibres?
Touch
Pressure
What is the function of Ay nerve fibres?
Motor to muscle spindles
What is the function of Ad nerve fibres?
Pain
Temp
Touch
What is the function of B nerve fibres?
Preganglionic sympathetic
What is the function of C dorsal root nerve fibres?
Pain
Temp
Touch
Reflex
What is the function of C sympathetic nerve fibres?
Postganglionic fibres
What are the main neurotransmitters and where are they secreted?
- Ach: CNS/PNS/vertebral NMJ
- Norepinephrine: CNS/PNS
- Dopamins: CNS/PNS
- Serotonin: CNS
- GABA: CNS
- Glycine: CNS
- Aspartate: CNS
- Glutamate: CNS
- Neuropeptides: CNS/PNS
What are the main functions of the different neurotransmitters?
- ACh: Excitatory
- NorE: Excitatory/inhibitory
- Dopamine: Excitatory
- Serotonin: Inhibitory
- GABA: Inhibitory
- Glycine: Inhibitory
- Glutamate: Excitatory
- Aspartate: Excitatory
- Neuropeptides: Excitatory
Which receptors are inotropic?
- Nicotinic Ach
- GABA-A
- 5HT
- NMDA
Which receptors are metabotropic?
G-Coupled protein receptors
- Muscarinic Ach
- GABA-B
- Dopamine
- Noradrenaline
- Metabopropic glutamate
Which nerve roots are motor and which are sensory?
Motor: Ventral nerve roots
Sensory: Dorsal nerve roots
What is the function of the ascending & descending spinal cord tracts?
Ascending: Sensory
Descending: Motor
What level of sensation is carried by fasciculus gracilis & cuneatus?
Gracilis: Below T6
Cuneatus: Above T6
How does the sensory pathway travel?
1) Afferent fibres enter SC via dorsal roots/trigeminal/vagus
2) 1st neurone cell body in dorsal root ganglia
3) Ab fibres ascend in dorsal column & synapse in medulla
4) Ad & C fibres branch caudally & rostrally in dorsolateral tract and synapse in in laminae of SC
Where are the 1st, 2nd & 3rd order neurones found in the ST tract?
1st: receptor - SC
2nd: SC - thalamus
3rd: Thalamus - cortex
Where are the 1st, 2nd & 3rd order neurones found in the dorsal column medial lemniscus pathway?
1st: Receptor - medulla
2nd: Medulla - Thalamus
3rd: Thalamus - Cortex
Where does the sympathetic NS originate?
Grey matter of lateral horn of the spinal cord T1-L3
Synapse in ganglia of the sympathetic chain
Where does the parasympathetic NS originate?
Neurones in the brain stem & sacral SC
Ganglia located near or in effector organ
Describe the fibres & neurotransmitters of the sympathetic NS
- Short preganglionic fibres
- Long post ganglionic fibres
- Nicotinic ACh receptors
- Postganglionic release NA/Adrenaline, Ach
Describe the fibres & neurotransmitters of the parasympathetic NS
- Long preganglionic fibres
- Short post ganglionic fibres
- Nicotinic ACh receptors
- ACh acts on muscarinic ACh receptors in postganglion
