Neurophysiology Flashcards
State the 4 components of a neuron
- Cell body (Soma)
- Dendrites
- Axons
- Presynaptic terminals
Define multipolar neurons
Neurons with single axons and 1>= dendritic branches that emerge from all parts of the cell body
Define resting membrane potential
The differential distribution of ions across the membrane of nerve cells and muscles as a result of the inside of the membrane being more negative (-75mV) compared to the outside.
State the ions that have a higher concentration in the intracellular and extracellular environment respectively
Intracellular:
- K+ (135mM vs 3mM)
Extracellular:
- Na (145mM vs 18)
- Cl (120mM vs 7)
- Ca (1.2mM vs 100nM)
Intracellular K+ is higher compared to extracellular K+. List 2 forces that forms the electrochemical gradient acting on K+
1) Concentration gradient that favours efflux of K+ from inside to the outside of the membrane
2) Electric gradient that hold/pulls charged K to the inside (since inside is relative -ve compared to outside)
Define equilibrium potential of an ion
The potential at which the outward and inward gradients acting on the ion balance out and there is no net movement of the ion across the membrane
State the formula to calculate the equilibrium potential for K
E = 58log(Kout / Kin)
State the effects if extracellular K is increased from eg. 3mM to -50mM
1) Concentration gradient is less steep
2) Greater accumulation of positive charges on inside of membrane
3) Membrane will depolarise to new value from starting resting potential of -80/-60mV
Which channels control the refractory period?
Inactivation of Na channels and opening of K channels
Define afferent and efferent neurons
Afferent: Signal carried from periphery to CNS
Efferent: Signal from CNS to periphery
List 4 examples of afferent neurons
- Pacinian corpuscle
- Abeta myelinated fibre
- Adelta myelinated fibre
- C fibre
What type of sensory information is carried by Abeta, Adelta and C fibres?
- Abeta: touch (nonpainful experience)
- Adelta & C-fibre: Pain
Describe how an action potential is generated
- Depolarisation
- Depolarisation to threshhold
- Upstroke: Opening of voltage gated Na channels
- Downstroke: Inactivation of voltage gated Na channel, opening of voltage gated K channel
- Repolarisation to RMP
Hypokalemia will lead to the following chnages in excitable membrane:
1) Hyperpolarisation of membrane
2) Depolarisation of membrane
3) Inactivation of voltage gated Na Channels
4) Opening of volatge gated K channel
Ans: 1). In hypokalemia, lower K+ outside relative to inside. This favors mmovement of K+ out of the cell. RMP hyperpolarises to blance out K+.
3) VG Na channels only open when treshhold AP is reached. Hence, hyperpolarisation will not affect this.
4) VG K+ channels only open towards peak of AP, not affected by hyperpolarisation
List 2 structures in the brain belo the limbic system
1) Hippocampus
2) Amygdala
State the roles that the cortex is involved in
Cortex plays a role in all functions
- Sensation & perception (both cortices)
- Voluntary control of movement
- Personality traits (frontal lobes)
- Learning and memory
- Language
Damage to the Broca’s area lead to?
Difficulties in expressing language
Damage in the Wernicke’s area leads to?
Difficulty in comprehending language
Define Aphasia
Difficulty in producing/comprehening speech not caused by hearing or motor distrubances.
State condition(s) that cause aphasia
Damage to Broca’s area and/or Wernicke’s area (affect written & spoken langugage)
T/F: Broca’s area and Wernicke’s area are both found in the right hemisphere.
False. Both are found in the left hemisphere
Which area of the brain is implicated in the development of depression?
Subgenual Anterior Cinguate Cortex (ACC). Increase in Subgenual ACC lead correlated with depression
State the function of the Hippocampus
Involved in Declarative memory, defined as memory that involves recall eg. no. of events, names, numbers
List a few examples of non-declarative memory
Memory that involves non-conscious recall eg. riding bike or swimming
