Midterm 1

Compare and contrast Action Potentials, Excitatory PostSynaptic Potentials (EPSPs), and Inhibitory PostSynaptic Potentials (IPSPs).

Action potentials are 'all-or-nothing' potentials. If the cell reaches the minimum excitatory threshold (-50mv) an action potential will fire non-decrementally all the way down the axon. ESPS and IPSPs, on the other hand, are graded potentials. In other words their amplitude is proportional to the strength of the stimulus and they travel through the cell decrementally (meaning they slowly get weaker and weaker as they travel). An action potential can lead to either an IPSP or an EPSP in the postsynaptic neuron by releasing neurotransmitters from the presynaptic membrane into the synaptic cleft, which are either inhibitory or excitatory. Inhibitory NTs lead to IPSP which decrease (inhibit) the likelihood of an AP firing. Excitatory NTs are the opposite and lead to EPSP which increase (excite) the likelihood of an AP firing. IPSP and EPSP take place in dendrites whereas APs take place along the axon.

Compare and Contrast the four main types of Glial Cells

Astrocytes: Restricted to the brain and spinal cord, these glial cells have elaborate local processes that give them their starlike appearance. The major function of astrocytes is to maintain a neuron's working environment. They do this by controlling the levels of a neurotransmitter around synapses, controlling the concentrations of important ions like potassium, and providing metabolic support. Central Nervous System Microglial Cells: 10-15% of all cells found within the brian. These are the brain's immune cells, serving to protect it against injury and disease. Microglia identify when something has gone wrong and initiate a response that removes the toxic agent and/or clears away the dead cell. Central Nervous System. Ependymal Cell: Produces cerebrospinal fluid that cushions the neurons. They line the CSF-filled ventricles in the brain and the central canal of the spinal cord. These are nervous tissue cells with a ciliated simple columnar form much like that of some mucosal epithelial cells. Oligodendrocytes and Schwann Cells: These provide support to axons of neurons in the nervous system, particularly those that travel long distances within the brain. They produce a fatty substance called myelin, which is 80% lipid and 20% protein. The myelin wraps around axons and acts as a layer of insulation. This myelin sheath allows electrical messages to travel faster and gives white matter its name - the white is the myelin wrapped around axons. Oligodendrocytes create myelin sheaths in the central nervous system whereas Schwann cells do it in the peripheral nervous system.

List five observable phenomena that can co-occur with increased local (regional) cortical metabolism.

1) Glucose Metabolism 2) Increased Blood Flow 3) Head Production 4) Electrical Signaling 5) Chemical Signaling

Describe the advantages in single case studies in neuropsychology.

1) Lots of attention can be given to case studies, which allows for the gathering of more information. 2) If there are more people being studied then a full analysis cannot be done as that would take a very long time. However, with only one person there can be lots of time taken to better understanding the case. 3) It is more cost effective since there is only 1 person as well as more time efficient. 4) Often, single case studies are the only option, especially rare cases that do not occur in everyday life. For example Phineas Gage suffered a serious brain injury and yet was able to function despite it. By looking at this case we can learn about something that has never happened before. 5) It allows for an in depth assessment over long periods of time (longitudinal studies)

Describe the disadvantages of single case studies

1) They can be biased since there is only one case to examine; which might lead to observer bias. 2) You cannot draw definite conclusions or cause/effect relationships 3) You cannot generalize across other people. 4) Lack of external validity 5) Nothing to compare findings to if the study is rare, leading to no empirical evidence. 6) Can be invasive and difficult to replicate.

Name the 12 cranial nerves

CN1: Olfactory Sensory: Smell CN2: Optic Sensory: Vision CN3: Oculomotor Motor: Eye movement and pupil reflex CN4: Trochlear Motor: Superior oblique muscle CN5: Trigeminal Both: Face sensation and chewing CN6: Abducens Eye movement CN7: Facial Both: Muscles of the face, taste CN8: Vestibulocochlear Sensory: Hearing and balance CN9: Glossopharyngeal Both: Throat sensation, taste, and swallowing CN10: Vagus Both: Movement, sensation, and abdominal organs. CN11: Accessory Motor: Neck movement CN12: Hypoglossal Motor: Muscles of tongue

Describe each of the following in a sentence: Closed Head Injury, Cerebral Edema, Cerebral Infract, Ischemia, Thrombosis, Stroke, Hydrocephalus, Encephalitis, Anoxia.

Closed Head Injury: Skull and Dura mater stay in tact. Cerebral edema: Inflammation of the brain. Cerebral infarct: Blockage or narrowing in the arteries Ischemia: Restriction of blood supply to tissues. Thrombosis: A blood clot in a blood vessel Stroke: Brain cells deprived of oxygen and glucose die. Hydrocephalus: Cerebral fluid build up in ventricles within the brain. Encephalitis: Inflammation in the brain caused by an infection or an allergic reaction. Anoxia: Absence of oxygen.

Compare and contrast the functions of Dorsal and Ventral Streams of Vision

Dorsal and Ventral Streams of vision are also known as what and where pathways. It describes two information processing streams in the occipital cortex, dorsal (which goes to parietal cortex) and ventral (which goes to the temporal cortex.) The dorsal stream is proposed to be involved in the guidance of actions and recognizing where objects are in space. Part of this belief stems from how damage to the posterior parietal cortex causes a number of spatial disorders. One such disorder is Apraxia, which was observed in the clinical case of A.T. who could observe objects just fine but he could not pick them up correctly. The ventral stream is associated with object recognition and form representation. Agnosias was observed In the clinical case of D.F., who had damage to her ventral cortex. Unlike D.F., she could pick up an object just fine however she could not *name* it. So, in comparison, where D.F. could pick up a square and put it into a square hole, she would not be able to recognize the object as a square. A.T. however *would* know that the object was a square but they would struggle to pick up the object and put it into the square shaped hole.

Compare and Contrast the major differences between excitatory and inhibitory cortical neurons.

Excitatory neurons release neurotransmitters that bind to receptors in the postsynaptic neurons and triggers a positive change in membrane potential in that neuron. Excitatory neurons are almost exclusively pyramidal cells. Inhibitory neurons release neurotransmitters that bind to different types of receptors in the postsynaptic neurons and triggers a negative change in the membrane potential. Inhibitory neurons form a diverse class with multiple subtypes.

List two common inhibitory neurotransmitters.

GABA is the main inhibitory transmitter in the adult vertebrate brain. Widely distributed in the neurons of the cortex, GABA contributes to motor control, vision, and many other cortical functions. It also regulates anxiety. Glycine is the main inhibitory transmitter in the CNS, especially the spinal cord, brainstem, and retina. It participates in the processing of motor and sensory information that permits movement, vision, and audition.

List two common excitatory neurotransmitters

Glutamate is the main excitatory transmitter in the central nervous system. It is by far the most abundant excitatory neurotransmitter in the vertebrate nervous system and under normal conditions, plays an important role in learning and memory. Acetylcholine is another excitatory neurotransmitter at the neuromuscular junction in the skeletal muscle, causing the muscle to contract. That said, it is inhibitory in the heart, where it slows the heart rate.

List five functions of inhibition in nervous system organization. (2 points each; 10 points for all five)

Lateral Inhibition: The capacity of an excited neuron to reduce the activity of its neighbors. Lateral inhibition disables the spreading of action potentials from excited neurons to neighboring neurons in a lateral direction. Feedback (recurrent) Inhibition: Collateral branches of the excitatory efferent fibers excite inhibitory interneurons that inhibit neurons by the feedback mechanism. Feed-Forward Inhibition: Collateral branches of the excitatory afferent fibers excite inhibitory interneurons that inhibit neurons in the forward direction. Postsynaptic Inhibition: Inhibition of activity in a postsynaptic neuron due to hyper-polerization. Presynaptic Inhibition: The amount of an excitatory neurotransmitter released at the end of an axon is decreased by the effects of a second neuron whose axon makes a synapse with the axon of the first neuron.

There is only one kind of action potential but there are many kinds of neurotransmitters. Why?

One of the main reasons additional neurotransmitters are valuable is because their receptors do different things. There are many neurons and each neuron responds to and releases on some kind of neurotransmitter. Therefore, you need a lot of neurotransmitters for them to bind to all of these different neurons. Action potential, on the other hand, works on the all-or-none law. The stimuli has to hit a certain threshold or else it simply will not work. Neurons only release one kind of neurotransmitter when activated by an action potential. This action potential never changes from neuron to neuron, it is simply the method that stimulates the release of neurotransmitters into a synapse. In other words any action potential can affect any neuron. It is the skeleton key that can open any door in a very large house, so to speak.

(Point Form Okay) The following 5 stages are associated with early neural development: Neuron death, Process Growth and Synapse Formation, Aggregation, Proliferation, and Migration. List these stages in the correct temporal order in which they occur, starting with the earliest, and briefly describe what happens in each stage. (5 points for the correct temporal order of the list and 1 point for each description).

Proliferation: It is during this stage that many new neurons are created. Migration: Newly created neurons migrate to the appropriate locations in the neural tube. Aggregation: Developing neurons align themselves to form the specific structures of the brain. Process Growth and Synapse Formation: Axons and dendrites grow and establish synaptic contacts. Neuron Death: Neurons that have not established effective synaptic contacts die.

Briefly describe the differences among sensory neurons, motor neurons, and interneurons.

Sensory Neurons: These neurons carry signals from the outer parts of your body (periphery) into the central nervous system. In other words they gather sensory input from the environment. The inputs that activate sensory neurons can be physical or chemical, corresponding to all five of our senses. Most sensory neurons are pseudounipolar, meaning they have dendrites on both ends, connected by a long axon with a cell body in the middle. Motor Neurons: Motor neurons of the spinal cord are part of the central nervous system (CNS) and connect to muscles, glands, and organs throughout the body. These neurons transmit impulses from the spinal cord to skeletal and smooth muscles, and so directly control all of our muscle movements. There are in fact two kinds of motor neurons: Those that travel from the spinal cord to muscle are called lower motor neurons and those that travel between the brain and spinal cord are called upper motor neurons. Motor neurons have the most common type of 'body plan' for a nerve cell - they are multipolar. This means they have a cell body on one end, a long axon in the middle, and dendrites on the other end. Interneurons: These neurons are the ones in between - they connect the spinal motor and sensory neurons. As well as transferring signals between sensory and motor neurons, interneurons can also communicate with each other, forming circuits of various complexity. Like the motor neuron, they are multipolar.

Briefly explain the following drug properties: Specificity, Affinity, and Efficacy

Specificity: The narrowness of the range of substances with which an antibody or other agent acts or is effective. Affinity: The degree to which a substance tends to combine with another. Efficacy: The ability to produce a desired or intended result.

List and briefly describe the 7 steps of neural coding.

Synthesization: NT molecules are synthesized from precursors under the influence of enzymes. Packaging: NT molecules are stored in vesicles. Shelf-Life (Hours): NT molecules leak from the vesicles as they're destroyed by enzymes. Release: AP causes the vesicles to fuse with the presynaptic membrane, which releases NT into Synaptic cleft. Autoreceptor binding: NT bind to autoreceptors on the presynaptic membrane and act as negative feedback. Receptor binding: NT diffuse across synaptic cleft and bind to postsynaptic receptors. Clean up: Leftover NT go away through reuptake, diffusion, or degradation.

In a single sentence for each item describe how the following items interfere with normal neurotransmission. Tetrodotoxin, Botulinum Toxin, Atropine, Cocaine, and Apomorphine.

Tetrodotoxin: This is an antagonist that is a sodium channel blocker. It inhibits the firing of action potentials in neurons by binding to the voltage-gated sodium channels in nerve cell membranes and blocking the passage of sodium ions (responsible for the rising phase of an action potential) into the neuron. Botulinum: This antagonist interferes with the neural transmission by blocking the release of acetylcholine, which is the principal neurotransmitter at the neuromuscular junction. Atropine: This Antagonist lowers the parasympathetic activity of muscles and glands in the parasympathetic nervous system by blocking the inhibitory effects of the parasympathetic neurotransmitter acetylcholine on heart rate leading to tachycardia. Cocaine: This agonist binds to the dopamine transporter, blocking the reuptake of dopamine from the synapse. Dopamine then accumulates in the synapse to produce an signal to the receiving neurons. Apomorphine: This dopamine agonist stimulates dopamine autoreceptors at low doses, whereas at higher doses it stimulates postsynaptic receptors as well.

Compare and Contrast the Isocortex and the Allocortex in the human brain

The Isocortex, often referred to as the neocortex, is involved in the higher order of brain functions such as cognition, spatial reasoning, and language. It is a major part of the cerebral cortex, taking up 80% of the human brain and consists of six layers. Of those layers, the first is the most superficial while the sixth is regarded as the deepest. The Allocortex, on the other hand, takes up a much smaller portion of the brain. Because this cortex was the first to evolve, it is the more primitive of the two and has only two to four cell layers. In primates it is relatively small and consists mainly of the hippocampus and adjacent cortex.

Discuss what is meant by the 'columnar' organization of the cerebral cortex.

The columnar organization hypothesis is currently the most widely adopted to explain the cortical processing of information. It's important to note that the columnar organization is functional by definition, and reflects the local connectivity of the cerebral cortex. Connections that go up and down within the thickness of the cortex are much denser than those that go side to side. Such columnar organization is particularly evident in the visual system, which can be seen in the form of ocular dominance and orientation columns. The cortical column, also known as a minicolumn, is the basic functional unit of the cerebral cortex and consists of six distinct layers of neurons. Layers 1 and 2 have short axons, neurons tightly clustered which results in a lot of synaptic activity. Layer 4 receives input from outside the cortex, while 5 and 6 are output layers (signals that leave the cortex). These layers make up 80% of the human brain.