AP2 2.1: The Brain Flashcards
two main divisions of the central nervous
The two main divisions of the central nervous system are the brain and spinal cord.
brain
The human brain consists of the following divisions: the cerebrum, brainstem, diencephalon, and the cerebellum. The protective structures of the brain are important because neurons are not replaceable. Nervous tissue is damaged by even the slightest pressure. The brain is protected by the skull of the skeletal system, meninges, a cushion of cerebrospinal fluid, and the blood-brain barrier. There are four ventricles inside of the brain.
Ventricles
Ventricles are cavities within the brain that are filled with cerebrospinal fluid (CSF). The ventricles include the two lateral ventricles, third ventricle, and fourth ventricle. The fourth ventricle drains into the central canal of the spinal cord, which also contains CSF.
meninges
The meninges are three layers of connective tissue membranes that cover and protect central nervous system organs and enclose cerebrospinal fluid.
choroid plexus
The choroid plexus is formed from a network of blood vessels within the ventricles. CSF circulates through the ventricles and into the meninges. It cushions the brain and spinal cord by providing buoyancy, allowing the brain to float. Once formed, the CSF circulates through the ventricles and into the subarachnoid space, bathing the brain in fluid.
blood-brain barrier
The blood-brain barrier is a diffusion barrier that prevents most particles from entering the central nervous system tissue, keeping the brain and spinal cord separate from general blood circulation. The blood-brain barrier is formed by the relatively impermeable brain capillaries, due to the glial cells astrocytes.
Cerebrospinal fluid (CSF)
Cerebrospinal fluid (CSF) is a special fluid formed in the walls of the ventricles from blood plasma by permeating through the choroid plexus.
dura mater
meninges three layers of connective tissue membranes
The leathery dura mater is the double-layered outer meninx.
arachnoid meninx
meninges three layers of connective tissue membranes
The middle arachnoid meninx is a loose layer separated from the dura mater by the subdural space. Beneath the arachnoid meninx is the subarachnoid space, which contains blood vessels and is filled with cerebrospinal fluid.
pia mater
meninges three layers of connective tissue membranes
The inner pia mater meninx is a thin connective tissue tightly attached to the brain.
astrocytes
Maintenance of the blood-brain-barrier is important to provide a stable chemical environment for the nervous system. A stable internal environment is important to protect neurons from chemical variations that could cause uncontrollable firing of neurons.
cerebrum
The cerebrum, the foremost part of the brain, is the largest part of the brain in humans comprising about 83% of total brain mass. It consists of two large masses called the left and right cerebral hemispheres.
The left cerebral hemisphere controls the right side of the body, and the right cerebral hemisphere controls the left side of the body.
median longitudinal fissure
The median longitudinal fissure separates the left and right cerebral hemispheres from one another. The brain is highly specialized in its control over body function.
gyri
The cerebral cortex is marked by raised ridges of tissue called gyri separated by shallow grooves called sulci.
fissures
The cerebral cortex is marked by raised ridges of tissue called gyri separated by shallow grooves called sulci. The deeper grooves, called fissures, separate large regions of the brain.
transverse fissure
The transverse fissure separates the cerebrum from the cerebellum
corpus callosum
The cerebral hemispheres are connected by a bridge of white nerve fibers called the corpus callosum
cerebral cortex
The outer portion of the cerebral hemispheres, the cerebral cortex, is highly convoluted and gray in color.
deeper sulci divide each hemisphere
Some of the deeper sulci divide each hemisphere into four surface lobes: frontal, parietal, temporal, and occipital. Different functions are associated with each lobe.
frontal lobe
The frontal lobe controls higher level executive functions, such as reasoning and decision making. The frontal lobe also controls motor functions and permits control over voluntary muscle actions.
occipital lobe
The occipital lobe interprets visual input.
parietal lobe
The parietal lobe receives sensory information from receptors in the mouth for taste and located in the skin, such as those for touch, pressure, and pain
temporal lobe
The temporal lobe has sensory areas for hearing and smelling.
Primary areas
Primary areas in each lobe receive or send information for one type of sensory or motor information.
Association areas
Association areas act mainly to integrate more than one type of sensory information for purposeful action. For example, a portion of the frontal lobe is called the primary motor cortex.
The primary motor cortex
The primary motor cortex (also called the precentral gyrus or the somatomotor cortex) controls voluntary motor movements for all parts of the body
primary sensory cortex
The parietal lobe receives sensory information from the same parts of the body in the primary sensory cortex (also called the postcentral gyrus or the somatosensory cortex).
association area
Each of the four lobes of the cerebral cortex contains an association area (Figure 2.7), which receives information from the other lobes and integrates it into higher, more complex levels of consciousness. Some examples of higher levels of consciousness are intellect, artistic/creative ability, learning, and memory.
Two more examples of specific areas of the brain mapped out in detail
Two more examples of specific areas of the brain mapped out in detail are Broca’s area and Wernicke’s area
Broca’s area
Broca’s area, located in the frontal lobe, is responsible for speech production.
Wernicke’s area
Wernicke’s area, located in the temporal lobe, is responsible for speech comprehension.
consciousness
The cerebrum is responsible for a consciousness, or the state of being awake and aware of a person’s surroundings. The cerebrum is the portion of the brain that governs intelligence, reasoning, and higher-level thinking. The cerebrum controls the activities of “lower parts” of the brain, including the brainstem, diencephalon, limbic system, and the cerebellum. The cerebrum can override the functioning of these lower parts of the brain. One example of this override capability is when a person uses meditation or medical biofeedback to reduce a high heart rate. The cerebrum initiates voluntary motor activities and controls the actions of the cerebellum by acting on sensory input via the thalamus.
brainstem
The medulla oblongata, pons, and midbrain lie in a portion of the brain known as the brainstem
medulla oblongata
The medulla oblongata lies between the spinal cord and pons and is anterior to the cerebellum. It contains several vital centers for regulating heartbeat, breathing, and vasoconstriction.
The medulla oblongata also contains the reflex centers for vomiting, coughing, sneezing, hiccuping, and swallowing. The medulla contains tracts that ascend or descend between the spinal cord and brain’s higher centers.
Vasoconstriction
medulla oblongata
Vasoconstriction is constriction of the blood vessels involved in the regulation of blood pressure.
pons
The pons contains bundles of axons traveling between the cerebellum and the rest of the central nervous system. In addition, the pons functions with the medulla to regulate the breathing rate and has reflex centers concerned with head movements in response to visual and auditory stimuli.
midbrain
The midbrain acts as a relay station for tracts passing between the cerebrum and spinal cord or cerebellum. The midbrain also has reflex centers for higher-level reflexes involving visual, auditory, and tactile responses.
superior and inferior colliculi
midbrain
The superior and inferior colliculi are located on the posterior portion of the midbrain. These regions of the midbrain control reflexes for the head and neck in response to a sudden visual or auditory stimulus.
