chapter 10: CNS

ventricles

Ventricles = hollow spaces inside the brain that contain CSF.

• From the ventricles, cerebrospinal fluid flows into the subarachnoid space between the pia mater and the arachnoid membrane, surrounding the entire brain and spinal cord in fluid

white matter vs gray matter

When viewed on a macroscopic level, the tissues of the CNS are divided into gray matter and white matter

White matter is mostly myelinated axons and contains very few neuronal cell bodies. Its pale color comes from the myelin sheaths that surround the axons.

Gray matter consists of unmyelinated nerve cell bodies, dendrites, and axons.

tract

Bundles of axons that connect different regions of the CNS are known as tracts.

• Tracts in the central nervous system are equivalent to nerves in the peripheral nervous system.

meninges

Three layers of membrane, collectively called the meninges {singular meninx, membrane}, lie between the bones and tissues of the central nervous system.

• These membranes help stabilize the neural tissue and protect it from bruising against the bones of the skeleton.

• Starting from the bones and moving toward the neural tissue, the membranes are (1) the dura mater, (2) the arachnoid membrane, and (3) the pia mater

cerebrospinal fluid (CSF)

Cerebrospinal fluid (CSF) is a salty solution that is continuously secreted by the choroid plexus, a specialized region on the walls of the ventricles

choroid plexus

The choroid plexus cells selectively pump sodium and other solutes from plasma into the ventricles, creating an osmotic gradient that draws water along with the solutes

• produces CSF

spinal nerve

spinal nerve is a mixed nerve containing both: Sensory (afferent) axons & Motor (efferent) axons

• Each spinal region is subdivided into segments, and each segment gives rise to a bilateral pair of spinal nerves. Just before a spinal nerve joins the spinal cord, it divides into two branches called roots

dorsal root vs ventral root

The dorsal root of each spinal nerve is specialized to carry incoming sensory information.

The ventral root carries outgoing information from the CNS to muscles and glands.

dorsal horn vs ventral horn

Sensory fibers from the dorsal roots synapse with interneurons in the posterior horns (dorsal) of the gray matter. The posterior horn cell bodies are organized into two distinct nuclei, one for somatic information and one for visceral information

The anterior horns (ventral) of the gray matter contain cell bodies of motor neurons that carry efferent signals to muscles and glands. The anterior horns are organized into somatic motor and autonomic nuclei. Efferent fibers leave the spinal cord via the ventral root.

ascending tract vs descending tract

Ascending tracts take sensory information to the brain. They occupy the dorsal and external lateral portions of the spinal cord (Fig. 10.6c).

Descending tracts carry mostly efferent (motor) signals from the brain to the cord. They occupy the ventral and interior lateral portions of the white matter.

cranial nerve

Cranial nerves carry sensory and motor information for the head and neck

cerebral cortex

The cerebral cortex {cortex, bark or rind; adjective cortical, plural cortices} is the outer layer of the cerebrum, only a few millimeters thick (FIG. 10.10a).

• Neurons of the cerebral cortex are arranged in anatomically distinct vertical columns and horizontal layers (Fig. 10.10b). It is within these layers that our higher brain functions arise.

sensory/motor/association areas of the cortex

1. sensory areas (also called sensory fields), which receive sensory input and translate it into perception (awareness);

2. motor areas, which direct skeletal muscle movement; and

3. association areas (association cortices), which integrate information from sensory and motor areas and can direct voluntary behaviors

Identify the cerebral hemispheres/cerebral cortex, pons, cerebellum, medulla, thalamus, hypothalamus, and spinal cord on a figure such as Figure 10.8c/d

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List three meninges of the brain, put them in order from superficial to deep, and recognize that the space between the arachnoid and pia is where CSF circulates around the brain

• Starting from the bones and moving toward the neural tissue, the membranes are (1) the dura mater, (2) the arachnoid membrane, and (3) the pia mater

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Describe how CSF protects the brain physically

Explain or identify what the blood-brain barrier is “made of” (structurally, what allows it to be a barrier?) and which types of molecules are and are not able to cross it

Draw or label the relationships among the dorsal and ventral roots, dorsal root ganglia and dorsal and ventral horns and explain what parts of neurons each consists of, and what information each part carries

Provide or identify the major function(s) of: medulla, pons, thalamus,
hypothalamus, corpus callosum, basal ganglia/nuclei, primary motor cortex, and limbic system

Recognize that each of the senses (e.g. hearing, taste, etc.) has a dedicated region of the cerebral cortex (e.g. auditory cortex) to process its signals

Recognize that most physiological variables have a circadian rhythm