Brain structure and neurons

What is the outside of the brain referred to?

Lateral

Where is the brain divided into its two hemispheres?

Along the longitudinal fissure

What is the outer layer called? What occurs there?

The cerebral cortex

Where most of the neuronal transmission occurs

What are the folds and furrows called? What are their characteristics?

Sulci

Consistent and provide landmarks

More wrinkly the brain, the greater the surface area - thus the more neurons in the brain

What are the ridges of the brain called?

Gyri

How do the two hemispheres communicate?

The corpus callosum

What is the occipital lobe responsible for?

Vision

Where is the occipital lobe located?

Back of the brain

What is the parietal lobe responsible for?

Goal-orientated behaviour

What is the temporal lobe responsible for?

Walking and balance

Aid the frontal lobe with emotional regulation

Musical ability

How does the brain function?

Makes decision on what behaviour to perform based on events in the external environment

Sends information to enact a response - somatosensory cortex/primary motor cortex

What is the role of the somatosensory cortex?

Maps the different anatomical regions of the body

Responsible for responding to touch

How is the cortex portioned up in relation to the somatosensory cortex?

Amount of cortex dedicated to a body part proportional to the amount of sensory information the body part receives

What are the ventricles? What are they used for?

Fluid-filled sacs that provide nutrients to the brain

Used in navigating the brain

What is the response from the neurons?

Stimulus input from the environment

Receive: sense organs

Interpret: Brain and spinal chord

Respond: Effector organs

Response: Output

What is the role of the dendrites?

Receive input from other neurons

Increases surface area

What is the role of the axon terminals?

Communicate with other neurons

Release of neurotransmitters

What makes up the Soma?

Nucleus (DNA), mitochondria (energy), and endoplasmic reticulum (protein synthesis)

What is the role of the axon?

Carries action potentials

Afferent and efferent axons

What are afferent axons?

Carries information into a region

What are efferent axons?

Carries information away from a region

What are glial cells?

Responsible for the structure of the brain - provides nutrients and holds the brain together

What are the four different types of glial cells?

Astrocytes; Microglia; Oligodendrocytes; Schwann cells

What is the role of astrocytes?

Provide physical support, nutrients, and involved in phagocytosis

What is the role of Micoglia?

phagocytosis and prevention against infection

What is oligodendrocytes?

Supports axons and produces myelin sheath in CNS

What is the role of schwann cells?

Supports axons and produces myelin sheath in PNS

What is neuronal transmission?

How one neuron communicates with another neuron

What is electrical transmission in neurons?

Happens within the neuronW

What is chemical transmission in the neuron?

Happens between the neurons

What are the characteristics of the cell membrane?

Phospholipid bilayer; Protein channels; Membrane is semi-permeable

How do sodium, potassium, chlorine, and calcium enter/leave the membrane?

Through channels that are sometimes closed

What state is the neuron in at rest?

Polarised

Resting potential of -70mV

What is meant by a neuron being ‘polarised’?

More negative inside the neuron than it is outside the neuron

Referred to as an electrical gradient

How does the neuron maintain resting potential?

Using the sodium potassium pump

Sodium potassium pump takes 3 sodium ions out of the cell and draws in 2 potassium ions

Where is most of the energy we consume used?

To maintain resting potential - to ensure that the sodium potassium pump is functioning as it should

Why do the sodium ions want to go back into the cell?

Electrical gradient - want to disperse into where it is more negative

Concentration gradient - wants to go from high to low concentration

Why do a small amount of potassium ions leave?

Concentration gradient and electrical gradient almost balance out

What ions are responsible for the membrane’s polarisation?

Negatively charged ions

At resting potential, what are the positions of the sodium and potassium channels?

Sodium channels are closed

Potassium channels are almost closed

What happens when the neuron becomes polarised?

Sodium channels and potassium channels start to open

Sodium enters the cell but there’s little effect on potassium

What happens if the threshold of excitation is reached?

Sodium channels fully open

Sodium rushes into the cell

Depolarisation

What is depolarisation?

Potassium channels are open so the cell is more positive

Potassium leaves the cell

Sodium channels close

What is hyperpolarisation?

Prevents certain part of the cell from depolarising

Causes action potential to travel down the axon

So the neuron doesn’t ‘fire’ unnecessarily

What is saltatory conduction?

Myelination speeds up propagation of the action potential

Sodium channels cannot cross the myelin sheath

Myelin sheath not across the entire axon so the action potential can jump across the axon

What is the refractory period?

Means that action potentials can only travel in one direction

What is meant by the ‘all or nothing’ law?

Neurons will only fire if the threshold of excitation is reached - as soon as the threshold is met, the entire thing fires

What is the rate law?

Intensity is represented by rate

What is the process of chemical communication between neurons (synapses)?

1. Action potential reaches the terminal button in the pre-synaptic neuron

2. Depolarisation of the terminal button

3. Synaptic vesicles migrate and fuse with the presynaptic membrane

4. Vesicles release chemical neurotransmitters into the synaptic cleft

5. Neurotransmitters attach to the postsynaptic membrane

6. Neurotransmitters are broken down by enzymes

7. Neurotransmitters are taken back up by the pre-synaptic terminal

8. Auto-receptors on the presynaptic membrane cause a decrease in synthesis or release of neurotransmitter

What are the two types of postsynaptic potential?

Depolarising and hyperpolarising

What is a depolarising postsynaptic potential?

Excitatory - pump out less sodium to ‘fire’

What is a hyperpolarising postsynaptic potential?

Inhibitory - pump out more sodium to stop ‘firing’

What determines postsynaptic potential?

Postsynaptic receptors

What determines an excitatory post-synaptic potential?

Sodium channel opens

Partial depolarisation (decrease in the negative state)

Increases likelihood postsynaptic neuron will fire

What determines an inhibitory post-synaptic potential?

Potassium channel opens

Hyperpolarisation (increase in the negative state)

Decreases likelihood that the postsynaptic neuron will fire

What is neural integration?

Interaction of excitatory and inhibitory synapses on a particular neuron

What does the rate at which a neuron fires depend upon?

The relative activity of the excitatory and inhibitory synapses on the postsynaptic dendrites

What is meant by learning?

Experiences which alter our neural networks resulting in changes in our behaviour

What is meant by memory?

The retention of learning

What are receptors?

They have a specific structure only allowing certain things to bind to itW

What role do neurotransmitters play in action potentials?

Bind to the receptor causing ion channels to open and initiate or inhibit a new action potential

What are the two process where neuroplasticity can occur?

Molecular

Structural changes

What is the result of long-term potentiation?

Increase in synaptic strength

What is the result of long-term depression?

Decrease in synaptic strength

What is long-term potentiation?

Involves two key neuro-receptors

NMDA receptor and AMPA receptor

What is the role of the NMDA receptor?

Controls calcium channels

Acts as a coincidence detector - detects glutamate levels in pre-synaptic events

What is the state of the NMDA receptor at rest?

Blocked by magnesium

What is the role of the AMPA receptors?

Controls sodium channels

What does it mean if low glutamate is released in the pre-synaptic event?

No post-synaptic event

What is the result of high glutamate in the pre-synaptic event?

LTP - Long Term Potentiation

What does a calcium influx result in?

Additional AMPA receptors inserted into the membrane

Formation of new synapses

What evidence is there to support Long Term Potentiation (LTP)?

Morris water maze - rats navigate to a hidden escape platform in the water

Hippocampus is important for spatial navigation (lesion)

NMDA receptor antagonist injected into the hippocampus - blocks LTP and impairs performance