Neurophysiology Flashcards
What is the nervous system
A collection or network circuit of neurons and glial cells. It is highly conserved, seen in all classes of life
What is the most simple nervous system
Forms a net
Nervous system of planaria
Has a little brain (concentration of neurons) and has two nerve cords down either side of its body which forms communication from tip to tail, and left to right
What is the nervous system of a leech
Central nerve, one coming either side
What is the nervous system of an insect
Brain, and in each segment, there is a cluster of nerves on each segment (ganglions)
What is the nervous system of a vertebrate
Brain, central spinal cord, each vertebrae has dorsal and ventral nerve roots which allow information to get from sensory, into spinal cord, and to the brain (and the other way around)
Grey matter
Neurons
White matter
Axons, covered in myelin
What is myelin
White lipid fat that coats axons to allow for fast transmission of the signals.
Function of the nervous system
- Information processing - each vertebra has information coming in through the dorsal and out through the ventral motor nerve route
- Senses the environment (light, vision, sound, temperature, vibration, smell, taste)
- Allow organisms to respond to the environment
- Coordinates bodily functions
- Voluntary movement
- Reflexes
- Memory, learning, emotion
CNS
Brain and spinal cord
PNS
Everything but brain and spinal cord
How does the nervous system work
Sensory information comes in (afferent neurons) it gets processed in the central nervous system, and then the information goes out (efferent neurons) to have a reaction.
Sympathetic nervous system
Fight or flight
Parasympathetic nervous system
Rest and digest
Enteric division
Digestive tract, moves food through the gut
Function of forebrain
sense of smell, regulates sleep, complex learning
What does the forebrain contain
olfactory bulb and cerebrum
Function of midbrain
routes information (sorts information to parts of the cortex where it needs to go)
Function of hindbrain
Motor control (movement) and involuntary activity (heartbeat, breathing)
Why do we have a highly folded cerebellum
Allows a higher surface area, more neurons can fit in that space, more grey matter and higher ability for processing (allows us to speak and communicate and have a higher level of intelligence)
Brainstem function
important for controlling involuntary parts of life (respiration rate, heart rate)
3 regions of the Frontal lobe
Motor cortex, prefrontal cortex, Brocas area
Motor cortex function
Initiate voluntary movement
Prefrontal cortex function
decision making, planning
Brocas area function
Speech formation
Somatosensory cortex function
area where all sensory information from periphery goes to be processed
Parietal lobe
Contains somatosensory cortex
Temporal lobe contains (2 things)
Auditory cortex, Wernickes area
Auditory cortex function
Hearing
Wernickes area function
Language comprehension
What does the occipital lobe contain
Visual cortex
Function of visual cortex
Process visual stimuli and pattern recognition
Cerebellum location
Above brain stem
Cerebellum function
Help movement, modulate the information going to and from the motor cortex, know where parts of the body exist in time and space
Neurons
Excitable cells specific to the nervous system
Glia
Group of other cells that support neurons, most abundant in the brain
Why and how are your bodies immune system and brain separated
Blood-brain barrier - stop immune system from entering the brain to prevent infection in the brain
Pericytes
Involved in blood-brain barrier to stop certain cells going through blood vessels easily
Why can the brain not get infected
Heat, swelling, pain comes with infection, skull is in a fixed position and therefore brain cannot swell
Astrocytes (glial cell) function
- Communicate with cells around the blood vessels
- Modulate the blood-brain barrier
- Metabolic support of neurons
- Do not generate action potentials
Microglia function
- Star shaped
- Survey environment
- Like resident immune cells in brain
- Scavenge, consume dead and dying cells
Allow for normal brain function
Oligodendrocytes function
- Lay down myelin on the axons of the neuron
- Have fatty lipid sheets that they wrap around the axons
Schwan cells
cells outside the CNS that lay down myelin
Why is coating cells in myelin important
fast conduction of action potentials over long distances, allows the action potential to jump
Function of the axon
transmits the action potential
Function of dendrites
receive information from other areas and direct it towards the cell body
Axon hillock
where the axon potential is generated
Synapse
A widened area in close proximity to the next neuron (but not touching) - the synapse is the area that makes the next neuron more excited/inhibited
How does neuron size correlate with signal conduction
Bigger the neuron, the more myelin it contains, the faster it conducts signals
Sensory (afferent neurons)
Send signal to the CNS (pain, touch, light, blood pressure). Neurons tend to be small and unmyelinated = slow
Interneuron
Transmit signal within the CNS. communicates between sensory and motor information. Tend to be small, short axons
Motor (efferent) neuron
Send signal from the CNS to muscles and glands (large and fast)
Unipolar
One axon
Bipolar
2 axons
Pseudounipolar
axons off to the side
Multipolar
all the dendrites, big axon, and synapses
Cone snails using all the types of specialist cells
- Sensory neurons sense environment
- When it senses a fish swimming past it gets integrated by interneurons
- Motor neurons send motor output and send probiscis out to paralyse prey
Key role of a neuron
Transmit signals by receiving info, processing it, and generating a response
How are signals transmitted within a neuron
Electrically via ion movement
How are signals transmitted between neurons
Chemically, using neurotransmitters
Why is a resting neuron excitable
due to its resting membrane potential (negative - charge of inside of neuron vs outside of neuron (ions)
How do Voltage gated ion channels work
- When a certain threshold (voltage) is reached, they will open/close
- Ion channels and ion pumps in the cell membrane allow ions to cross the cell membrane
- These channels/pumps are specific for a particular ion(s)
What is the RMP
The difference in voltage (charge) across a membrane at rest
Normal conc of Na and K
Normally, sodium is present in high conc outside cell, and potassium is present in high conc inside the cell.
Sodium potassium pump ratios
3 sodium for 2 potassium
Purpose of sodium potassium pump
Change membrane potential via pumping of more sodium than potassium
Voltage of gradient of RMP
-65 million volts
What is Nernst potential
Is the membrane potential at which there is no net (overall) flow of that particular ion from one side of the membrane to the other.
What is Hyperpolarisation
Making the inside of the cell more negative
Effect of hyperpolarisation
(harder to create action potential, more stimulus required for neuron signalling - may be useful in chronic pain
What is depolarisation
Making the cell more positive
Why are action potentials “all or nothing”
If the stimulus is strong enough, a point of ‘no return’ is reached, where voltage-gated Na+ channels open
How much energy does a neuron take to fire
-55 million volts
Are action potential one or multi directional
Axon hillock moves down the axon in only one way
Neuron at a resting state
Lots of sodium outside, lots of potassium inside
At rest, both voltage-gated channels are closed
This means Na stays outside, K stays inside
Only sodium-potassium pump maintains RMP.
How does depolarisation work
Stimulus comes in, and opens some sodium channels. This allows Na to flow into the cell. The cell becomes slightly more positive due to influx of positive ions. Reaches a threshold (action potential becomes all or nothing
What happens in the rising phase
All sodium channels open. Sodium comes into the cell making inside very positive
What happens in the falling phase
All sodium channels open Sodium comes into the cell making inside very positive
What happens during the Absolute refractory period
No other stimulus can elicit action potential. Allows transport of action potential to go only in one direction
What is the meaning of undershoot
Membrane potential returns to normal
What is a Graded potential
a hyperpolarization or depolarization that shifts the membrane potential a little but does not cause an action potential and is decremental
Where does myelin come from
Schwann cells (PNS) and oligodendrocytes (CNS)
What are nodes of ranvier
Where voltage-gated Na channels are present.
What is saltatory conduction and why is it good
Myelin allows the action potential to leap along the axon to move faster (jump) and with this, neuron signals can travel faster and over long distances.
Multiple sclerosis
Myelin sheaths around neurons are lost. Axons don’t have myelin, therefore, struggle to get action potentials from a to b. The resulting poor signal transmission leads to fatigue, paralysis and cognitive impairment
Why are MS rates higher in Dunedin than Auckland
Seems to be higher the further from the equator you are (sunlight and vit D is a factor)
What are the 3 min clinical forms of MS
Relapsing-remitting, Secondary progressive, Primary progressive
Relapsing Remitting MS
(85-90% - autoimmune disease where T and B cells infiltrate blood brain barrier, get into CNS, and attack myelin coating). Characterised by immune attacks, resolution, than repeated attacks.
Symptoms of MS
Poor balance, fatigue, spasticity
What is/causes Parkinsons
Decreased dopamine results in disordered movement
Symptoms of parkinsons
Tremors, poor balance, and muscle coordination, cognitive impairment
How to treat parkinsons
Disease can be treated, but not cured. Taking L-dopa (dopamine pre-cursor) can restore dopamine levels,
What are senses
Transformation of external energy into an action potential. Your sensory organs are designed to receive/convert energy, but its your brain that perceives these signals as images or sounds
4 steps in sensory pathways
Sensory reception, Sensory transduction, Transmission,
Perception
Sensory reception
The detection of a stimulus by sensory cells
Sensory cells
either themselves a neuron, or are cells that interactions with a neuron via neurotransmitters.
Sensory transduction
Changing membrane potential
