Neuroscience: CNS, PNS, Brain Structures, and Neural Physiology

What are the components of the central nervous system (CNS) and peripheral nervous system (PNS)?

CNS: Brain and spinal cord. PNS: All nerves outside the CNS.

What is the main role of the autonomic nervous system (ANS) compared to the somatic nervous system (SNS)?

ANS regulates involuntary bodily functions (e.g., heart rate, digestion), while SNS controls voluntary movements.

Which anatomical structures form the gray and white matter in the brain and spinal cord?

Gray matter consists of neuronal cell bodies, while white matter is made up of myelinated axons.

Where do the spinal nerves connect to the spinal cord?

Spinal nerves connect to the spinal cord at the dorsal and ventral roots.

What are the anatomical subdivisions of the brainstem and their essential functions?

Midbrain (vision, hearing, motor control), Pons (regulates breathing, communication between different parts of the brain), Medulla Oblongata (controls autonomic functions like heart rate and respiration).

Why can damage to the brainstem be detrimental to the entire body's systems?

The brainstem controls vital functions such as breathing and heart rate; damage can disrupt these essential processes.

List the anatomical subdivisions of the brainstem.

Midbrain, Pons, Medulla Oblongata.

Which cranial nerve roots originate in each of the brainstem subdivisions?

Midbrain: CN III (Oculomotor), CN IV (Trochlear); Pons: CN V (Trigeminal), CN VI (Abducens), CN VII (Facial), CN VIII (Vestibulocochlear); Medulla: CN IX (Glossopharyngeal), CN X (Vagus), CN XI (Accessory), CN XII (Hypoglossal).

What are the major anatomical subdivisions of the cerebellum?

Anterior lobe, posterior lobe, and flocculonodular lobe.

Which anatomical structures form the diencephalon?

Thalamus, hypothalamus, epithalamus, and subthalamus.

Name all six cortical lobes and indicate the location of the insular cortex.

Frontal, parietal, temporal, occipital, limbic, and insular cortex (located deep within the lateral sulcus).

What structures form the corpus callosum and internal capsule?

Corpus callosum: Myelinated axons connecting the two cerebral hemispheres. Internal capsule: Myelinated axons connecting the cortex to the brainstem and spinal cord.

What is cerebrospinal fluid (CSF)? Describe its production sites, circulation, and reabsorption.

CSF is a clear fluid that cushions the brain and spinal cord, produced in the choroid plexus, circulates in the ventricles and subarachnoid space, and is reabsorbed into the bloodstream through arachnoid granulations.

Name the main blood vessels that supply the spinal cord.

Anterior spinal artery and paired posterior spinal arteries.

List the components of the anterior and posterior circulations of the brain.

Anterior circulation: Internal carotid arteries; Posterior circulation: Vertebral arteries and basilar artery.

Name the blood vessels that supply the brainstem, cerebellum, and cerebral cortex lobes.

Brainstem: Basilar artery; Cerebellum: Superior, anterior inferior, and posterior inferior cerebellar arteries; Cerebral cortex: Anterior, middle, and posterior cerebral arteries.

Provide an example of a bipolar or multipolar neuron and describe their morphological features.

Bipolar neuron: Has two processes (one axon, one dendrite); Multipolar neuron: Has multiple dendrites and one axon. Pseudounipolar neuron has a single process that splits into two branches.

What are the major chemicals involved in changing the polarity of the cell membrane and generating action potential?

Sodium (Na+) and potassium (K+) ions are crucial for depolarization and repolarization, respectively.

Define depolarization, repolarization, hyperpolarization, and refractory period.

Depolarization: Decrease in membrane potential; Repolarization: Return to resting potential; Hyperpolarization: Increase in membrane potential; Refractory period: Time during which a neuron cannot fire another action potential.

What are the four types of membrane channels and their mechanisms?

1. Voltage-gated channels: Open/close in response to membrane potential changes. 2. Ligand-gated channels: Open/close in response to binding of a chemical messenger. 3. Mechanically-gated channels: Open/close in response to mechanical forces. 4. Leak channels: Always open, allowing ions to pass through.

How is the resting membrane potential maintained?

Maintained by the sodium-potassium pump (Na+/K+ ATPase) and the selective permeability of the membrane.

What is the difference between local and action potential?

Local potential is a small, graded change in membrane potential; action potential is a large, all-or-nothing change that propagates along the axon.

What does the term 'graded' mean in relation to local receptor or synaptic potentials?

Graded means the potential varies in magnitude depending on the strength of the stimulus.

Describe two types of graded potential summation that can result in depolarization.

Temporal summation: Rapid succession of stimuli at the same synapse; Spatial summation: Simultaneous stimuli from multiple synapses.

Define the threshold of action potential and the normal threshold value.

Threshold of action potential is the membrane potential that must be reached to trigger an action potential, typically around -55 mV.

What neuronal properties promote faster conduction velocity of an action potential?

Myelination and larger axon diameter.

What signal transmission event prevents action potential from flowing backward?

The refractory period prevents backward flow of action potentials.

List the cells that form macroglia and microglia. Which macroglial cells are most abundant in the CNS?

Macroglia: Astrocytes, oligodendrocytes, and ependymal cells; Microglia: Immune cells of the CNS. Astrocytes are the most abundant macroglial cells.

Describe the main functions of astrocytes in the nervous system.

Astrocytes support neurons, maintain the blood-brain barrier, and regulate nutrient and ion balance.

Describe the main functions of microglial cells in the nervous system.

Microglial cells act as immune defenders, removing debris and dead cells.

What is the role of radial cells in the development of the CNS?

Radial cells guide the migration of neurons during brain development.

How can glial cells inhibit regeneration after nervous system damage?

Certain glial cells, like astrocytes, form scar tissue and release inhibitory factors that impede regeneration.