The adult brain is separated into four major regions: the cerebrum, the diencephalon, the brain stem, and the cerebellum. The cerebrum is the largest portion and contains the cerebral cortex and subcortical nuclei. It is divided into two halves by the longitudinal fissure.
The cortex is separated into the frontal, parietal, temporal, and occipital lobes. The frontal lobe is responsible for motor functions, from planning movements through executing commands to be sent to the spinal cord and periphery. The most anterior portion of the frontal lobe is the prefrontal cortex, which is associated with aspects of personality through its influence on motor responses in decision-making.
The other lobes are responsible for sensory functions. The parietal lobe is where somatosensation is processed. The occipital lobe is where visual processing begins, although the other parts of the brain can contribute to visual function. The temporal lobe contains the cortical area for auditory processing, but also has regions crucial for memory formation.
Nuclei beneath the cerebral cortex, known as the subcortical nuclei, are responsible for augmenting cortical functions. The basal nuclei receive input from cortical areas and compare it with the general state of the individual through the activity of a dopamine-releasing nucleus. The output influences the activity of part of the thalamus that can then increase or decrease cortical activity that often results in changes to motor commands. The basal forebrain is responsible for modulating cortical activity in attention and memory. The limbic system includes deep cerebral nuclei that are responsible for emotion and memory.
The diencephalon includes the thalamus and the hypothalamus, along with some other structures. The thalamus is a relay between the cerebrum and the rest of the nervous system. The hypothalamus coordinates homeostatic functions through the autonomic and endocrine systems.
The brain stem is composed of the midbrain, pons, and medulla. It controls the head and neck region of the body through the cranial nerves. There are control centers in the brain stem that regulate the cardiovascular and respiratory systems.
The cerebellum is connected to the brain stem, primarily at the pons, where it receives a copy of the descending input from the cerebrum to the spinal cord. It can compare this with sensory feedback input through the medulla and send output through the midbrain that can correct motor commands for coordination.
alar plate
developmental region of the spinal cord that gives rise to the posterior horn of the gray matter
amygdala
nucleus deep in the temporal lobe of the cerebrum that is related to memory and emotional behavior
anterior column
white matter between the anterior horns of the spinal cord composed of many different groups of axons of both ascending and descending tracts
anterior horn
gray matter of the spinal cord containing multipolar motor neurons, sometimes referred to as the ventral horn
anterior median fissure
deep midline feature of the anterior spinal cord, marking the separation between the right and left sides of the cord
ascending tract
central nervous system fibers carrying sensory information from the spinal cord or periphery to the brain
basal forebrain
nuclei of the cerebrum related to modulation of sensory stimuli and attention through broad projections to the cerebral cortex, loss of which is related to Alzheimer’s disease
basal nuclei
nuclei of the cerebrum (with a few components in the upper brain stem and diencephalon) that are responsible for assessing cortical movement commands and comparing them with the general state of the individual through broad modulatory activity of dopamine neurons; largely related to motor functions, as evidenced through the symptoms of Parkinson’s and Huntington’s diseases
basal plate
developmental region of the spinal cord that gives rise to the lateral and anterior horns of gray matter
Broca’s area
region of the frontal lobe associated with the motor commands necessary for speech production and located only in the cerebral hemisphere responsible for language production, which is the left side in approximately 95 percent of the population
Brodmann’s areas
mapping of regions of the cerebral cortex based on microscopic anatomy that relates specific areas to functional differences, as described by Brodmann in the early 1900s
cauda equina
bundle of spinal nerve roots that descend from the lower spinal cord below the first lumbar vertebra and lie within the vertebral cavity; has the appearance of a horse’s tail
caudate
nucleus deep in the cerebrum that is part of the basal nuclei; along with the putamen, it is part of the striatum
central sulcus
surface landmark of the cerebral cortex that marks the boundary between the frontal and parietal lobes
cerebral cortex
outer gray matter covering the forebrain, marked by wrinkles and folds known as gyri and sulci
cerebrum
region of the adult brain that develops from the telencephalon and is responsible for higher neurological functions such as memory, emotion, and consciousness
cerebellum
region of the adult brain connected primarily to the pons that developed from the metencephalon (along with the pons) and is largely responsible for comparing information from the cerebrum with sensory feedback from the periphery through the spinal cord
cerebral hemisphere
one half of the bilaterally symmetrical cerebrum
corpus callosum
large white matter structure that connects the right and left cerebral hemispheres
descending tract
central nervous system fibers carrying motor commands from the brain to the spinal cord or periphery
direct pathway
connections within the basal nuclei from the striatum to the globus pallidus internal segment and substantia nigra pars reticulata that disinhibit the thalamus to increase cortical control of movement
disinhibition
disynaptic connection in which the first synapse inhibits the second cell, which then stops inhibiting the final target
dorsal (posterior) nerve root
axons entering the posterior horn of the spinal cord
epithalamus
region of the diecephalon containing the pineal gland
frontal eye field
region of the frontal lobe associated with motor commands to orient the eyes toward an object of visual attention
frontal lobe
region of the cerebral cortex directly beneath the frontal bone of the cranium
globus pallidus
nuclei deep in the cerebrum that are part of the basal nuclei and can be divided into the internal and external segments
gyrus
ridge formed by convolutions on the surface of the cerebrum or cerebellum
hippocampus
gray matter deep in the temporal lobe that is very important for long-term memory formation
hypothalamus
major region of the diencephalon that is responsible for coordinating autonomic and endocrine control of homeostasis
indirect pathway
connections within the basal nuclei from the striatum through the globus pallidus external segment and subthalamic nucleus to the globus pallidus internal segment/substantia nigra pars compacta that result in inhibition of the thalamus to decrease cortical control of movement
inferior colliculus
half of the midbrain tectum that is part of the brain stem auditory pathway
inferior olive
nucleus in the medulla that is involved in processing information related to motor control
kinesthesia
general sensory perception of movement of the body
lateral column
white matter of the spinal cord between the posterior horn on one side and the axons from the anterior horn on the same side; composed of many different groups of axons, of both ascending and descending tracts, carrying motor commands to and from the brain
lateral horn
region of the spinal cord gray matter in the thoracic, upper lumbar, and sacral regions that is the central component of the sympathetic division of the autonomic nervous system
lateral sulcus
surface landmark of the cerebral cortex that marks the boundary between the temporal lobe and the frontal and parietal lobes
limbic cortex
collection of structures of the cerebral cortex that are involved in emotion, memory, and behavior and are part of the larger limbic system
limbic system
structures at the edge (limit) of the boundary between the forebrain and hindbrain that are most associated with emotional behavior and memory formation
longitudinal fissure
large separation along the midline between the two cerebral hemispheres
occipital lobe
region of the cerebral cortex directly beneath the occipital bone of the cranium
olfaction
special sense responsible for smell, which has a unique, direct connection to the cerebrum
parietal lobe
region of the cerebral cortex directly beneath the parietal bone of the cranium
parieto-occipital sulcus
groove in the cerebral cortex representing the border between the parietal and occipital cortices
postcentral gyrus
ridge just posterior to the central sulcus, in the parietal lobe, where somatosensory processing initially takes place in the cerebrum
posterior columns
white matter of the spinal cord that lies between the posterior horns of the gray matter, sometimes referred to as the dorsal column; composed of axons of ascending tracts that carry sensory information up to the brain
posterior horn
gray matter region of the spinal cord in which sensory input arrives, sometimes referred to as the dorsal horn
posterior median sulcus
midline feature of the posterior spinal cord, marking the separation between right and left sides of the cord
posterolateral sulcus
feature of the posterior spinal cord marking the entry of posterior nerve roots and the separation between the posterior and lateral columns of the white matter
precentral gyrus
primary motor cortex located in the frontal lobe of the cerebral cortex
prefrontal lobe
specific region of the frontal lobe anterior to the more specific motor function areas, which can be related to the early planning of movements and intentions to the point of being personality-type functions
premotor area
region of the frontal lobe responsible for planning movements that will be executed through the primary motor cortex
proprioception
general sensory perceptions providing information about location and movement of body parts; the “sense of the self”
putamen
nucleus deep in the cerebrum that is part of the basal nuclei; along with the caudate, it is part of the striatum
reticular formation
diffuse region of gray matter throughout the brain stem that regulates sleep, wakefulness, and states of consciousness
somatosensation
general senses related to the body, usually thought of as the senses of touch, which would include pain, temperature, and proprioception
striatum
the caudate and putamen collectively, as part of the basal nuclei, which receive input from the cerebral cortex
subcortical nucleus
all the nuclei beneath the cerebral cortex, including the basal nuclei and the basal forebrain
substantia nigra pars compacta
nuclei within the basal nuclei that release dopamine to modulate the function of the striatum; part of the motor pathway
substantia nigra pars reticulata
nuclei within the basal nuclei that serve as an output center of the nuclei; part of the motor pathway
subthalamus
nucleus within the basal nuclei that is part of the indirect pathway
sulcus
groove formed by convolutions in the surface of the cerebral cortex
superior colliculus
half of the midbrain tectum that is responsible for aligning visual, auditory, and somatosensory spatial perceptions
tectum
region of the midbrain, thought of as the roof of the cerebral aqueduct, which is subdivided into the inferior and superior colliculi
tegmentum
region of the midbrain, thought of as the floor of the cerebral aqueduct, which continues into the pons and medulla as the floor of the fourth ventricle
temporal lobe
region of the cerebral cortex directly beneath the temporal bone of the cranium
thalamus
major region of the diencephalon that is responsible for relaying information between the cerebrum and the hindbrain, spinal cord, and periphery
ventral (anterior) nerve root
axons emerging from the anterior or lateral horns of the spinal cord
Watch this video to learn about the basal nuclei (also known as the basal ganglia), which have two pathways that process information within the cerebrum. As shown in this video, the direct pathway is the shorter pathway through the system that results in increased activity in the cerebral cortex and increased motor activity. The direct pathway is described as resulting in “disinhibition” of the thalamus. What does disinhibition mean? What are the two neurons doing individually to cause this?
Both cells are inhibitory. The first cell inhibits the second one. Therefore, the second cell can no longer inhibit its target. This is disinhibition of that target across two synapses.
Watch this video to learn about the basal nuclei (also known as the basal ganglia), which have two pathways that process information within the cerebrum. As shown in this video, the indirect pathway is the longer pathway through the system that results in decreased activity in the cerebral cortex, and therefore less motor activity. The indirect pathway has an extra couple of connections in it, including disinhibition of the subthalamic nucleus. What is the end result on the thalamus, and therefore on movement initiated by the cerebral cortex?
By disinhibiting the subthalamic nucleus, the indirect pathway increases excitation of the globus pallidus internal segment. That, in turn, inhibits the thalamus, which is the opposite effect of the direct pathway that disinhibits the thalamus.
Watch this video to learn about the gray matter of the spinal cord that receives input from fibers of the dorsal (posterior) root and sends information out through the fibers of the ventral (anterior) root. As discussed in this video, these connections represent the interactions of the CNS with peripheral structures for both sensory and motor functions. The cervical and lumbar spinal cords have enlargements as a result of larger populations of neurons. What are these enlargements responsible for?
There are more motor neurons in the anterior horns that are responsible for movement in the limbs. The cervical enlargement is for the arms, and the lumbar enlargement is for the legs.
Compared with the nearest evolutionary relative, the chimpanzee, the human has a brain that is huge. At a point in the past, a common ancestor gave rise to the two species of humans and chimpanzees. That evolutionary history is long and is still an area of intense study. But something happened to increase the size of the human brain relative to the chimpanzee. Read this article in which the author explores the current understanding of why this happened.
According to one hypothesis about the expansion of brain size, what tissue might have been sacrificed so energy was available to grow our larger brain? Based on what you know about that tissue and nervous tissue, why would there be a trade-off between them in terms of energy use?
Energy is needed for the brain to develop and perform higher cognitive functions. That energy is not available for the muscle tissues to develop and function. The hypothesis suggests that humans have larger brains and less muscle mass, and chimpanzees have the smaller brains but more muscle mass.
1. Which lobe of the cerebral cortex is responsible for generating motor commands?
A) temporal
B) parietal
C) occipital
D) frontal
D
2. What region of the diencephalon coordinates homeostasis?
A) thalamus
B) epithalamus
C) hypothalamus
D) subthalamus
C
3. What level of the brain stem is the major input to the cerebellum?
A) midbrain
B) pons
C) medulla
D) spinal cord
B
4. What region of the spinal cord contains motor neurons that direct the movement of skeletal muscles?
A) anterior horn
B) posterior horn
C) lateral horn
D) alar plate
A
5. Brodmann’s areas map different regions of the ________ to particular functions.
A) cerebellum
B) cerebral cortex
C) basal forebrain
D) corpus callosum
B
1. Damage to specific regions of the cerebral cortex, such as through a stroke, can result in specific losses of function. What functions would likely be lost by a stroke in the temporal lobe?
The temporal lobe has sensory functions associated with hearing and vision, as well as being important for memory. A stroke in the temporal lobe can result in specific sensory deficits in these systems (known as agnosias) or losses in memory.
2. Why do the anatomical inputs to the cerebellum suggest that it can compare motor commands and sensory feedback?
A copy of descending input from the cerebrum to the spinal cord, through the pons, and sensory feedback from the spinal cord and special senses like balance, through the medulla, both go to the cerebellum. It can therefore send output through the midbrain that will correct spinal cord control of skeletal muscle movements.