neurophysiology Flashcards
Sketch the basic nervous system pathway from input to output.
neuron picture
What are the roles of the nervous system?
control behaviour and coordinate homeostatic mechanism :
- collect info from internal & external environments.
- analyse and integrate this info.
distribute info to appropriate parts of the body.
-control muscles.
store and retrieve (when required) info.
What are the 2 types of cells in the NS? What are their roles?
- vegetative (glial cells): support/protection, nutritive, developmental role (possibly processing)
- information processing (neurons): conduct info (sometimes large distances). communicate with each other and with other cell types by chemical messenger.
What is the cell body called? What does it contain?
- soma
- nucleus, ER, Ribosomes for protein synthesis.
What is the input to a neuron? How do they conduct?
- dendrites.
- passively conduct - signal lost over distance.
Sketch a neuron
dendrites - cell body - axon - synaptic terminals.
What is passive conduction?
- depolarisation in the membrane spreads across membrane and decreases in strength over distance.
- only effects voltage gated Na/K channels adjacent to the area of depolarisation.
What type of conduction occurs on the axon?
- ‘internal’ active conduction.
Where does the axon terminate?
- secretory endings (synapse).
How many cells does a typical cell “talk to”?
- 50 other cells.
What is the function of a sensory neuron?
- detect stimuli and respond by sending message into NS.
What is the function of an interneuron?
- cells connecting only to other neurons within NS.
What is the function of a motor neuron?
- send message out of NS to effectors (muscle/glands).
What part of the brain is characteristic of learning?
- interneurons.
What makes up the PNS?
- Autonomic nervous system:
- The part of the nervous system that regulates the involuntary activity of the heart, intestines, and glands, including digestion, respiration, perspiration, metabolism, and blood-pressure modulation.
- Somatic nervous system:
- The part of the peripheral nervous system that transmits signals from the central nervous system to skeletal muscle and from receptors of external stimuli to the central nervous system, thereby mediating sight, hearing, and touch.
What makes up the ANS? What do they control?
- sympathetic division.
- parasympathetic division.
- enteric division.
- control of smooth muscles, cardiac muscles, glands.
How is a message communicated within a cell?
- info passed over long distances as electrical impulses (action potentials) in the cell membrane.
How is a message communicated between cells?
- info passed by chemical messengers (neurotransmitters).
What is the word used to describe the ability of a cell to respond to an electrical stimulus?
- membranes of neurons (and muscles) are excitable.
What must a depolarisation meet to cause an action potential?
- Threshold value.
What speed does a nerve impulse travel at?
- 100m/s.
What part of the cell generates an action potential?
generated actively (requires energy) by membrane.
What is the name of a junction between nerve cells?
- synapse.
How do cells in the NS generate electrical potentials and use them to transmit information?
- stimulus causes local depolarisation of membrane allowing Na flow in.
- if stimulus strong enough - enough Na flow in to reach threshold value.
- if reached Na/K voltage gated channels will open allowing flood of Na across membrane generating an action potential.
- moves unidirectionally down neuron membrane via saltatory conduction.
- unidirectional due to refractory period when sodium channels are closed and unable to open while K flows out of the neuron.
How do cell in the NS talk to each other across a gap?
release of neurotransmitters across synapse.
How does an electrical signal get converted to movement by a muscle cell?
- AP moves along sarcolemma of the muscle and down into T-tubule to the interim of the muscle near the ends of the sarcoplasmic reticulum.
- depolarisation along membrane of T-tubule leads to opening of voltage gated Ca ion channels, leading to an influx of Ca into SR.
- Ca ions then diffuse into sarcoplasm to where tropomyosin lay either side of the Actin myofilament thus covering up sites where myosin can bind.
- when the Ca ions bind to the troponin, attached to the tropomyosin, it causes a conformational change in troponin which moves the tropomyosin away from the myosin binding sites on the actin myofilaments allowing cross bridges to form.
- ADP + P on myosin head still present from last contraction allows cross bridge t form which removes P.
- energy in myosin then pulls myosin head thus moving the Actin.
- the ADP is then released and a new ATP binds to the myosin head causing it to release the actin filament.
What is excitability?
What does this enable?
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What are the 2 types of conduction? What are their roles?
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What 2 things enable cells to make voltages?
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What is the typical ratio of Na inside to outside the cell?K?Ca?Cl?
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What gives a cell selective permeability?
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What determines a membranes permeability?
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Take K, for example, what are the 2 forces acting on K at a resting cell?
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What is an equilibrium potential? What 2 things are equal at this potential?
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What equation is used to work out a cell’s membrane potential? Write it out
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What is Ek? Describe and number? Ena? Ecl? Eca?
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What ion is the cell most permeable at resting?
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The membrane potential is very similar to K, why does it diverge at low K concentrations?
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Which of these statements are true: because of the activity of the NA K ATPase:
a. NAi is low compared to Nao
b. Ki is low compared to Ko
c. Nai is high compared to Nao
d. Ki is high compared to Ko
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Ki is high compared to Ko so when the membrane is permeable to K, this causes
a. K+ to leave the cell
b. K+ to enter the cell
c. The cell to be negative inside
d. The cell to be + inside
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