Neuro Flashcards
All-or-none law
principle that once an action potential is triggered in an axon, it is propagated, without becoming smaller, to the end of the axon.
Ion transporter
a special protein molecule located in the membrane of a cell; actively transports ions into or out of the cell
Ion channel
special protein molecule located in the membrane of a cell; controls the entry/exit of particular ions
Ion
positively/negatively charged particle; produced when many substances dissolve in water
Resting potential
membrane potential of a neuron when it is not producing an action potential
Action potential
sudden reversal of the electrical charge across the cell membrane: from the soma to its terminal buttons, causes the release of a neurotransmitter
Neurotransmitter
chemical released by terminal buttons that causes the postsynaptic neuron to be excited or inhibited
Myelin sheath
insulating material that encases most axons
prevents depolarisation and speeds up propagation of AP
Terminal button
the rounded spelling at the end of the axon, releases neurotransmitter
Axon
long thin part of a neuron attached to the soma, divided into a few/many branches ending in terminal buttons
Soma
cell body, largest part of neuron
Dendrite
treelike part of neuron on which other neurons form synapses
Glia
cells of the CNS that provide support for neurons and supply them with some essential chemicals
Neurons
neural cell that consists of a cell body with dendrites and an axon whose branches end in terminal buttons that synapse with muscle fibres, gland cells or other neurons
Nerves
bundles of many thousands of individual fibres wrapped with tough membrane, transmit messages
Wrinkled cortex
bulges (gyri) ang grooves (fissures) - more complex brains require a larger cerebral cortex, these increase surface area
Cerebral ventricles
hollow, fluid-filled chambers in the brain, produce CSF
Cerebral cortex
thin layer of tissue (grey matter) which contains billions of neural cells. Where perceptions take place, memories are stored, plans are formulated and executed.
These cells are connected to other parts of the brain through bundles of nerve fibres called white matter
Blood-brain barrier
Capillaries in the brain do not have openings, unlike ones on the rest of the body, to protect the brain from chemical assault
Not perfect, toxic chemicals sometimes still make their way into the brain
Protection of NS
Spinal cord runs through the middle of the spinal column - a stack of hollow bones called the vertebrae
Brain and spinal cord enclosed by a three-layered set of membranes known as the meninges
Brain and spinal cord doesn’t not touch skull/vertebrae: floats in cerebrospinal fluid (CSF)
Cerebrum
More recently evolved
Perception, memories and behaviours
Cerebellum
Attached to back of brain stem
Control and coordinate movements; especially rapid, skilled movements (includes learned ones)
Brain stem
Most primitive region of brain - controls physiological functions and automatic behaviours
Some animals, such as amphibians, only have a brain stem and a simple cerebellum
3 major functions of the brain
- Controlling behaviour
- Processing and retaining the information we receive from the environment
3.Regulating the body’s physiological processes
What does the brain control?
muscles, glands and internal organs
How does info from the rest of the body reaches the spinal cord and the brain?
spinal nerves
How does info from head/neck region reach the brain?
cranial nerves
Sensory neuron
detects changes in the external/internal environment and sends info about this to CNS
Motor neuron
has terminal buttons that form synapses with muscle fibres.
an action potential that travels down its axon will cause the muscle to twitch
Synapse
junction between the terminal button of one neuron and the membrane of a muscle fibre, gland or other neuron.
neurons communicate using chemical transmission
presynaptic neuron
neuron with terminal buttons that form synapses with and excite/inhibit another neuron
postsynaptic neuron
is excited or inhibited by another neuron’s terminal buttons
neurotransmitter receptor
special protein molecule located in the membrane of the postsynaptic neuron that responds to molecules of the neurotransmitter
How do receptors produce excitatory/inhibitory effects
open ion channels
excitatory synapse: permit NA ions to enter post
inhibitory synapse: permit K ions to leave
Synaptic vesicles
bubbles of membrane in terminal buttons
contain molecules of a neurotransmitter
Synaptic cleft
fluid-filled gap between pre and post synaptic membranes
Where do terminal buttons release neurotransmitters?
synaptic cleft
Reuptake
molecules of the neurotransmitter that have been released in cleft are quickly taken up again so that it only has a short time to stimulate the postsynaptic receptors
How do drugs impact synaptic transmission?
stimulate/inhibit release of neurotransmitters
mimic the effects of neurotransmitters
block effects
interfere with reuptake - increases the effect of neurotransmitter
Drugs and postsynaptic receptors
Stimulate: stimulates receptors
Block: bind with receptor but doesn’t stimulate it, inhibits synaptic transmission
Glutamate
important excitatory neurotransmitter in brain and spinal cord
GABA
important inhibitory neurotransmitter in brain
Acetylcholine
neurotransmitter: responsible for muscular contraction, activates cerebral cortex, controls REM sleep, controls hippocampus
barbiturate
drug that causes sedation
benzodiazepine
class of drug having anxiolytic effects (e.g. diazepam - valium)
Neostigmine
drug that enhances effects of ACh by blocking the enzyme that usually destroys it
nicotine
binds andf stimulate ACh receptors, mimicking the effects
monoamine
category of neurotransmitters that includes dopamine, noradrenaline and serotonin
Dopamine
movement, attention, learning and reinforcing the effects of drugs that people tend to abuse,
What drugs inhibit the reuptake of dopamine?
Amphetamine and cocaine
Noradrenaline
cause an increase in vigilance, controls REM sleep
Serotonin
regulation of mood, control of eating/sleep/arousal and regulation of pain, suppresses risky behaviours
Peptides
category of neurotransmitters and neuromodulators that consist of two or more amino acids, linked by peptide bonds
what are some opiates?
Opium, morphine and heroin
what effect do endogenous opioids have when they stimulate certain receptors in the brain
decreased sensitivity to pain and a tendency to persist in ongoing behaviour
Brain lesions
Drill hole into skull and insert wire/metal tube to either use electricity to produce heat and destroy a small portion the brain or insert a chemical that over stimulates neurons and kills them.
CNS
central nervous system - brain and spinal cord
PNS
Peripheral Nervous system - nerves, ANS, ENS
ANS
autonomic NS - controls non-voluntary bodily functions (4Fs etc)
uses acetylcholine and noradrenaline
What are the two branches of the autonomic nervous system?
Sympathetic NS: for action
Parasympathetic NS: for rest and recuperation
ENS
1/2 billion neurons located in the wall of gastrointestinal tract
interacts with brain vis symp and para NS but can function on its own
control digestive activity
Meninges
flexible sheet made of 3 membranes between bone and nervous tissue
1. Dura mater: tough + thick
2. Arachnoid membrane: spongy, filled wth CSF and blood vessels, cushioning
3. Pia mater: thin membrane against brain
Spinal cord
interface between brain and PNS
connected to sensory, motor, autonomic nerves
Controls some movement like spinal reflexes
Cerebellum damage
affect walking, speech
Brain stem damage
coma, death
Thalamus
sensory relay to cortex - smell doesnt go through it
Hypothalamus
hormonal regulation and motivational control
Limbic system
control of emotion and memory
Basal Ganglia
Action and thought, offline action
Corpus Callosum
connects the 2 hemispheres of the brain
Vertebrates
Separation between PNS and CNS
There is an increase in forebrain in animals that exhibit more complex behaviour and neocortex in mammals
Resting potential
when a neuron is not actively transmitting a nerve impulse
inside is more negatively charged than the outside, maintained by sodium potassium pumps.
Refractory period
the time after an action potential is generated, it cannot produce a new AP because all sodium channels are already opened/being opening at maximum speed
Explain why not all stimuli generate an action potential
It might be in the refractory period and not enough gates are opening to reach the threshold level
Opiates
Mimic brain’s opioid NTs
Cocaine/amphetamines/ecstasy
Promot transmission of main monoamines
Caffeine
blocks adenosine receptors
Antidepressant drugs
enhance serotonin and noradrenaline transmission by block reuptake
Most anti-schizophrenic drugs…
block dopamine
Agnostic Drug
Activates certain receptors and opens ion channels
deactivates enzyme in the synapse
blocks reuptake
promotes NT release
Antagonistic Drug
a chemical substance that binds to and blocks the activation of certain receptors, preventing a biological response
Transcranial Magnetic Stimulation (TMS)
magnetic pulse is sent that depolarises neurons
discovers what area is roughly responsible for a certain function
Electrical Stimulation (EBS)
Microinjection into specific region in the brain (drugs - inhibit)
Single-cell recording
electrode implanted in brain that record output from the brain
more specific
Electroencephalography (EEG)
electrodes placed on scalp that record electrical fields from the brain
not precise/weak
CT scan
computerised tomography - uses xray images to represent the brain
Positron Emission Tomography (PET)
Radioactive-labelled oxygen (or glucose) - radiotracers are injected and emits signals that the PET scan detects where this is happening in the brain (3D)
measures changes in oxygen consumption
good spatial resolution, bad temporal resolution
Magnetic Resonance Imaging (MRI)
gets hydrogen atoms in the brain to align by bombarding it with high frequency radio waves - identifies brain tissue and creates 2D image
Functional Magnetic Resonance Imaging (fMRI)
measures changes in O2 consumption in the brain to indicate what regions are active - good spatial resolution (3D)
Magnetoencephalography (MEG)
detects a small amount of magnetic field and creates a 3d reconstruction of electrical activity to form a functional map of the brain - expensive and difficult
The regulation of feeding
Hungry > release ghrelin > tells brain we are hungry > behaviour
Leptin
makes sure you arent hungry while you sleep
What happens to our body when we dont sleep?
There is an increase in ghrelin and we become less responsive to insulin - obesity/diabetes
impacts symp NS - heart health
what keeps us awake?
Noradrenaline neurons in Locus Coeruleus
Serotonin neurons in Raphe nuclei
Acetylcholine neurons in Pons
what sends us to sleep?
superchiasmatic nucleus controls release of melatonin from pineal gland and has its own clock - signals night-time to the body
What happens do adenosine when we sleep?
Since adenosine is a byproduct of ATP it builds up in the brain when we are awake. It increases sleepiness by inhibiting alertness centres and stimulating sleep centres. Adenosine is cleared when we sleep
Preoptic area (anterior hypothalamus)
stimulation can induce sleep
electrical activity when we are awake
high frequency, noisy
electrical activity when we are asleep
slow, rhythmic patterns
REM sleep
brain waves become desynchronised multiple times, rapid eye movement
REM sleep decreases over life span, alcohol reduces it too
What causes REM sleep?
acetylcholine neurons in the Pons stimulate neurons in the thalamus which project to neural cortex. various areas in the brain become active.
suppression of frontal cortex allows us to turn these experiences into a story
we are paralysed
what is the concept of reward?
motivation to engage in a particular behaviour
neural mechanism of reward
dopamine axons in medial forebrain bundle contribute to rewarding effect of electrical stimulation
What is hemispheric dominance?
Several higher functions are lateralised, one side of the brain is more dominant - most people’s left brain control speech and comprehension
Damage to Broca’s area
at lower posterior of left frontal lobe
difficulties speaking but can generally understand speech - problems with writing not drawing
Damage to Wernicke’s area
at posterior region of temporal lobe
causes problems with comprehension speech, cannot read - gibberish speech
Split brain
remove corpus callosum so the seizure (electrical storm) doesn’t spread to the rest of the brain - may have problems with left and right,
Hippocampus
memory structure in the brain
Hippocampal amnesia
anterograde amnesia, deficit to leaning and memory
Anterograde amnesia
Can remember old things but unable to retain or learn anything new
Wernicke-Korsakoff’s Syndrome
Vitamin B1 deficiency in chronic alcoholics causing confusion, unusual movements and eye movements - can lead to Korsakoff’s psychosis (anterograde and retrograde amnesia).
damage to mammillary bodies in hypothal
Alzheimer’s Disease
progressive degeneration of brain tissue
loss of new info > loss of distant memories > loss of facts and finally procedural skills
senile plaques
neuro-fibrillary tangles
What is the difference between anterograde amnesia and retrograde amnesia?
anterograde amnesia refers to the inability to make new memories and remember new information and retrograde amnesia refers to the loss of old memories
Frontal lobe
Planning and executive functions (memory selection as well)
Emotional expression
Problem solving
Memory
Language
Judgement
Sexual behaviours
Parietal lobe
Sensory experiences are interpreted
Proprioception
Where things are in space, representing space for action
Occipital lobe
Colour, Form, Motion
Temporal lobe
Memory
Encoding
Processes auditory info
Taste
Recognise faces
Language
3 parts of frontal lobe
Prefrontal - higher cognitive functions and personality
Motor
Premotor -
Cortical Homunculus
Distorted representation of human body based on neurological map of the areas and proportions of the human brain dedicated to processing function
What evidence supports the localisation of function?
Different areas of the brain use more energy/oxygen when they are presented with a specific stimulus -
Area in the brain where it responds to seeing faces, there would only be activity when people were shown a face as opposed to other images.
What evidence is shown demonstrating that not every brain area is locked to a single function?
With mental imagery and visual imagery, multiple parts of the brain were activated or “shared”.
Brain regions can be responsible for multiple functions
