Week Two

Question 1

Longitudinal Fisher

Answer 1

Brain hemispheres are separated by the longitudinal fisher.

Question 2

Contralateral Arrangement

Answer 2

• The left hemisphere is strongly connected with the right side of our body an vice versa.
• Left hemisphere controls the movement of the right side of the body.
• Sensations are also processed on the opposite side.
• Visual information from the left visual field is processed by the right hemisphere of the brain and vice versa.
• The visual information in the left travels through the optic chiasm to the primary visual cortex in the occipital lobe, but to the right hemisphere.
• Left visual field in processed by both eyes but ends up in the right hemisphere.

Question 3

Split Brain Patients

Answer 3

• Contralateral arrangements usually don’t matter as the corpus callosum is in tact.
  
  • Split brain patients were those who had severe epilepsy.
  • Anything that was presented in the right visual field was what the brain identified as seeing, this is due to the left side being for language.
  • If something was seen in the left visual field, the left hand would reach out and grab it.
  • The right hemisphere of the brain did see something but could not verbalise it.
  • This experiment discovered that the hemispheres had different features.

Question 4

Split Brain and Visual Relatedness

Answer 4

Asked to select with each hand an image that related to the scene that they saw.
Left visual field saw snow, processed by the right and controls the left hand.
Right visual field saw chicken foot, processed by left hemisphere and controls right hand.
Patients could not verbalise what they saw on the right side as it was processed by the hemisphere. Instead, the brain made something up to reveal why they chose the picture on the left.

Question 5

Neurons

Answer 5

Neurons are the basic functional unit of the nervous system that allows communication.
Neurons are not physically touching, there is a gap between the terminal button of one neuron and the dendrite of another.
Communication between neurons occurs by a chemical process.

Question 6

Glial Cells

Answer 6

Glial cells nourish, protect and support neurons and are thought to be critical in brain development.

Question 7

Oligodendrocyte glial

Answer 7

The oligodendrocyte glial cells covers the axons of neurons with myelin which is critical to effective brain functioning.

Question 8

Dendrites

Answer 8

Dendrites function principally to receive messages from other neurons. They transmit the information they receive to the soma.

Question 9

Soma

Answer 9

The soma (cell body) contains mechanisms that control the metabolism and maintenance of the cell. It also collates ‘messages’ from other neurons.

Question 10

Axon

Answer 10

The axon carries ‘messages’ away from the soma towards the cells with which the neuron communicates; these messages are called action potentials

Question 11

Terminal Buttons

Answer 11

Terminal buttons are located at the end of the ‘twigs’ that branch off the ends of axons; they secrete neurotransmitters which affect the activity of other cells with which the neuron communicates

Question 12

Myelin

Answer 12

Myelin insulates some axons to promote efficient transmission of the action potential. It serves to increase the speed of propagation of the action potential along the axon.

Question 13

Cell Membrane

Answer 13

Cell membrane is made up of a lipid bilayer (two layers of fatty molecules). Embedded protein molecules; proteins form pores or channels that control movement of material into and out of cell.

Question 14

Resting Membrane Potential

Answer 14

• RMP derives from the difference in chemical composition inside and outside the cell at rest.
• It is the result of relative concentrations of potassium ions, chloride ions, negatively charged protein ions and sodium ions.
• Action potential is a brief reversal in the resting charge of the neuron.
• Action potential is created when the neuron membrane is sufficiently depolarized (resting potential moves towards 0 mV).
• Neuron fires at -55mV.
  A neuron either does not reach action potential or the full action potential is fired. Referred to as the all-or-nothing principle.
• Neurons rest with an overall negative charge.
• Resting potential of a neuron is -70 mV.

Question 15

Movement of Ions in the Action Potential

Answer 15

1. Sodium channels open, allowing Na+ ions (orange arrows) to enter. The membrane potential is reversed at this point; this causes nearby channels to open, perpetuating the reversal along the axon
2. The Na+ channels close and potassium channels open, allowing K+ ions (green arrows) out of the axon; this restores the electrical charge
3. Ion transporters pump Na+ ions out of the axon and K+ ions back in to restore the normal balance.

Question 16

Myelin Sheath

Answer 16

• The sheath is an electric insulator that prevents current flow across membrane.
  
  • Current can only flow across the membrane where there are breaks in the myelin (nodes of Ranvier).
    ○ Sodium channels are concentrated in the Nodes.
    ○ Action potential can only be generated in the Nodes.
  • Jumping of the action potential from break to break massively increases the speed.
  • Non-myelinated axons are much slower.

Question 17

synaptic transmission

Answer 17

• Neurons don’t touch one another, they are separated by the synapse.
  
  • When the action potential reaches the terminal buttons it causes a release of specialized chemicals (neurotransmitters) that travel across the synapse and are received by dendrites of another neuron.
  • The cell that’s sends the signal is called presynaptic and the one that receives the signal is called postsynaptic.
  1. Before the action potential, neurotransmitters are stored in the terminal button.
  2. The action potential triggers the release of the neurotransmitter into the synaptic cleft.
  3. Neurotransmitters diffuse across the synapse. Some of them attach to receptor molecules in the postsynaptic membrane and activate them, thus either inhibiting or enabling the postsynaptic neuron to generate an action potential.

Question 18

Neurotransmitters

Answer 18

• Neurotransmitter refers to chemical substances that carry signals across the synapse.
  
  • Neurotransmitters bind to receptors on the postsynaptic neuron.
  • Receptors are specialized protein molecules. The bind of neurotransmitters to receptors cause ion channels to open, which changes the membrane potential, thus affecting the probability that the neuron will fire an action potential.
  • If a neurotransmitter binds with a receptor and depolarizes the membrane, it is excitatory and increases the likelihood that the neuron will fire an action potential. The opposite is also true.