M11: Central Nervous System

What does the CNS consist of?

The CNS consists of the brain and spinal cord.

What percentage of CNS cells are neurons?

Only 10% of CNS cells are neurons; the rest are neuroglia.

What supports the CNS?

The CNS is supported by the cerebral spinal fluid (CSF).

What are specific areas of neuronal cell bodies called?

Specific areas of neuronal cell bodies are called nuclei.

What are axons from multiple nuclei running in parallel called?

Axons from multiple nuclei running in parallel are called fibers (or nerve tracts or white matter).

What is the function of the meninges?

The meninges is a protective structure for the CNS.

What are the three layers of the meninges?

The three layers of the meninges are the dura mater, arachnoid mater, and pia mater.

What is a subarachnoid hemorrhage?

Subarachnoid hemorrhage is bleeding between the arachnoid and pia maters.

What is a subdural hematoma?

Subdural hematoma is the tearing of veins between the dura and arachnoid maters.

What is an epidural hematoma?

Epidural hematoma is a collection of blood between the dura mater and surrounding bone.

What are the main functions of CSF?

CSF regulates ions and nutrients, supports and cushions the brain and spinal cord, and provides chemical and immunological buffering.

Where is CSF produced?

CSF is produced by specialized tissue called choroid plexus and ependymal cells within the ventricles.

What is the blood-brain barrier (BBB)?

The BBB is a selective barrier that limits transport due to tight junctions between cells.

What types of transport occur across the BBB?

Transport across the BBB includes lipid-mediated, carrier-mediated, and receptor-mediated transport.

What is the Circle of Willis?

The Circle of Willis is a structure that allows blood supplying anterior and posterior portions of the brain to overlap.

What is a stroke?

A stroke is an interruption of blood flow to the brain that causes neuronal death.

What are the two types of strokes?

The two types of strokes are ischemic (reduced blood flow) and hemorrhagic (bleeding).

What are the risk factors for stroke?

Risk factors include elevated blood pressure, smoking, obesity, elevated blood cholesterol, diabetes, and heart problems.

What types of neurons are primarily found in the CNS?

CNS neurons are largely multipolar or pyramidal.

What percentage of CNS cells are neuroglia?

Neuroglia make up 90% of the cells of the CNS.

What is the role of oligodendrocytes?

Oligodendrocytes create the myelin sheath surrounding neurons.

What functions do astrocytes perform?

Astrocytes perform multiple functions including neurotransmitter secretion/absorption, maintaining the 3D structure of the brain, glycogenesis, fluid regulation, and repair.

What is the function of ependymal cells?

Ependymal cells secrete cerebrospinal fluid (CSF).

What is the role of microglia?

Microglia are resident macrophages that remove damaged neurons, recognize infectious agents, and prevent inflammation.

What are the main functions of the CNS?

The main functions of the CNS include consciousness, perception of external sensory information, integrating information, and sending signals that control the main functions of body tissues.

What is neurogenesis?

The process of forming new neurons in the brain.

When does neurogenesis primarily occur during development?

During fetal development.

What do neural stem cells produce during neurogenesis?

Stem cells and oligodendrocyte precursor cells (OPCs).

What happens to developing cells by week 16 of fetal development?

They either make synaptic connections or undergo apoptosis.

What evidence supports adult neurogenesis?

Experiments using BrdU or above-ground radiation show new neuron formation in adults.

What is a reflex arc?

The smallest, simplest neuronal circuit that does not involve processing in the brain.

What are the basic components of a reflex arc?

Sensory neuron, motor neuron, and target.

What types of reflexes do somatic and autonomic reflexes affect?

Somatic reflexes affect muscles; autonomic reflexes affect organs.

What is the function of the spinal cord?

To carry information to and from the central nervous system (CNS).

What are the three main segments of the spinal cord?

Cervical, thoracic, and lumbar segments.

What is the dorsal root of the spinal nerve responsible for?

Carrying sensory information to the CNS.

What is the function of the ventral root of the spinal nerve?

Carrying motor information away from the CNS.

What is the cervical plexus composed of?

Ventral rami of spinal nerves C1 - C4.

What does the brachial plexus innervate?

Mainly the upper limbs.

What is the major nerve originating from the cervical plexus?

The phrenic nerve.

What is the lumbosacral plexus composed of?

Ventral rami of spinal nerves L1-L4 (lumbar) and L4-S4 (sacral).

What is the function of the cerebellum?

Control of balance, eye movements, posture, and coordination of complex movements.

What is the role of the thalamus in the brain?

It receives input from most sensory neurons in the body.

What is the primary motor cortex also known as?

Precentral gyrus.

What is the primary somatosensory cortex also known as?

Postcentral gyrus.

What is the function of the hippocampus?

Associated with memory, spatial navigation, and learning.

What are some age-related changes in the CNS?

Loss of neurons, decreased sensory input, and slowing of cognitive function.

What can accumulation of protein-rich plaques and tangles lead to?

Memory loss and confusion.

What is the function of the reticular formation?

Controls respiration, cardiovascular function, digestion, alertness, sleep patterns, and modulation of pain.