Chapter 2 - Neuroanatomy

Question 1

ROSTRAL, CAUDAL, DORSAL and VENTRAL

Answer 1

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Question 2

IPSILATERAL and CONTRALATERAL

Answer 2

IPSILATERAL structures are on the same side of the MIDLINE, CONTRALATERAL are on opposite sides.

Question 3

MEDIAL and LATERAL, PROXIMAL and DISTAL

Answer 3

MEDIAL structures are close to the MIDLINE, whereas LATERAL ones are far. PROXIMAL and DISTAL work in the same way.

Question 4

CORONAL, SAGITTAL and HORIZONTAL sections

Answer 4

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CORONAL SECTIONS are also called FRONTAL

Question 5

MENINGES

Answer 5

Three layers of membranes, called MENINGES, provide protection to the brain.
The outermost one is the DURA MATER, the one in the middle is the ARACHNOID LAYER and the innermost layer is the PIA MATER.
Between the arachnoid and pia mater layers is the SUBARACHNOID SPACE, filled by the CSF.

Question 6

CEREBROSPINAL FLUID

Answer 6

CSF is secreted in the VENTRICULAR SYSTEM by the CHOROID PLEXUS, which converts material from the nearby blood supply into CFS. It circulates through the CENTRAL CANAL of the spinal cord, the four ventricles, and in the SUBARACHNOID SPACE.
Essentially, CSF allows the brain to float in the skull. CSF:
1) Provides protection against trauma, acting like a cushion;
2) Avoids neurons responding to external pressure but only to significant input;
3) Allows the circulation of NUTRIENTS and removes waste;
4) Allows neurochemicals to diffuse and travel a long way.

Question 7

The VENTRICULAR SYSTEM

Answer 7

The brain hosts four hollow spaces, called VENTRICLES. There are TWO LATERAL VENTRICLES, one in each hemisphere, and the THIRD and the FOURTH VENTRICLES, located in the brainstem.
The CEREBRAL AQUEDUCT con­nects the third and fourth ventricles. The fourth ventricle is continuous with the central canal of the spinal cord - below the fourth ventricle, there is a small opening that allows the CSF to flow into the subarachnoid space that surrounds both the brain and spinal cord.

Question 8

HYDROCEPHALUS

Answer 8

HYDROCEPHALUS is a condition caused by a blockage in the circulation of CSF. It used to be a major cause of intellectual disability in newborns, but it can now be treated by the installation of a shunt to drain off excess fluid.

Question 9

The BRAIN’S BLOOD SUPPLY

Answer 9

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Having a rich blood supply is essential, because neurons are more vulnerable to oxygen deprivation than other types of cells in the body - even brief interruptions to the brain’s blood supply can cause permanent cell death or damage.

Question 10

The CENTRAL NERVOUS SYSTEM

Answer 10

The CNS is one of two components of the nervous system - it includes the BRAIN and SPINAL CORD.

Question 11

The SPINAL CORD

Answer 11

The SPINAL CORD is a long cylinder of nerve tissue that is located in the upper 2/3 of the VERTEBRAL COLUMN. Running down the center of the spinal cord is the CENTRAL CANAL , through which CSF circulates. The SPINAL NERVES exit between the bones of the vertebral column forming 31 segments. When viewed in a horizontal section, much of the chord appears white, with a H-letter-shaped gray area in the middle - WHITE MATTER is made up of axons, whereas GRAY MATTER consists primarily of cell bodies.
The neurons found in the DORSAL HORNS of the H receive SENSORY INPUT, whereas neurons in the VENTRAL HORN of the H pass MOTOR INFORMATION on to the muscles.
Without any input from the brain, the spinal cord neurons are capable of some important reflexes, such as the KNEE JERK.

Damage to the spinal cord results in loss of sensation and loss of voluntary movement in parts of the body served by nerves located below the damaged area - it is considered to be permanent. A person with cervical damage is a QUADRIPLEGIC, whereas a person with lumbar damage is a PARAPLEGIC.

Question 12

DIVISIONS of the BRAIN

Answer 12

FOREBRAIN = PROSENCEPHALON = TELENCEPHALON + DIENCEPHALON
TELENCEPHALON = CEREBRAL CORTEX, LYMBIC SYSTEM , BASAL GANGLIA
DIENCEPHALON = THALAMUS, HYPOTHALAMUS

MIDBRAIN = MESENCEPHALON = TECTUM, TEGMENTUM

HINDBRAIN = RHOMBENCEPHALON = METENCEPHALON + MYELENCEPHALON
METENCEPHALON = CEREBELLUM, PONS
MYELENCEPHALON = MEDULLA

Question 13

The MEDULLA

Answer 13

The MEDULLA, or MYELENCEPHALON, is the most caudal portion of the brain. It contains mostly white matter, for all information travelling to and from higher structures must pass through the medulla. It contains several NUCLEI - some of these nuclei’s axons form several of the CRANIAL NERVES, while others manage essential functions such as breathing, blood pressure and heart rate.
The medulla also hosts the caudal portion of the RETICULAR FORMATION.

Question 14

The RETICULAR FORMATION

Answer 14

The RETICULAR FORMATION is a complex collection of nuclei that runs along the midline of the brainstem from the medulla, through the pons and up into the midbrain.

Question 15

The PONS

Answer 15

The PONS forms the METENCEPHALON with the CEREBELLUM. It lies on top of the medulla and one of its main functions is that of forming connections between the medulla and higher structures -pons mean bridge in latin.
The pons contains:
1) The COCHLEAR NUCLEUS and the VESTIBULAR NUCLEUS, which are both cranial nerve nuclei;
2) The RAPHE NUCLEI and the LOCUS COERLUS, which project widely to the rest of the brain and influence mood, states of arousal, aggression, appetite, and sleep.
3) Some nuclei that produce REM sleep.

Question 16

The CEREBELLUM

Answer 16

The CEREBELLUM forms the METENCEPHALON with the PONS and contains more neurons than the rest of the brain combined. A traditional view of the cerebellum emphasized its role in coordinating voluntary movements, and regulating balance, but more contemporary views see the cerebellum as responsible for some of our most sophisticated processing of informa­tion, including executive functions and emotional processing.

Question 17

The MIDBRAIN

Answer 17

The MIDBRAIN, or MESENCEPHALON, is formed by a dorsal half, the TECTUM, and a ventral half, the TEGMENTUM. The CEREBRAL AQUEDUCT, which links the third and fourth ventricle, separates the two halves.

Surrounding the cerebral aqueduct are cell bodies known as PERIAQUEDUCTAL GRAY (PAG), which:

1) inte­grate autonomic, motor, and pain responses to envi­ronmental stimuli;
2) play an important role in our perception of pain - there are large numbers of receptors in the PAG that respond to opiates such as morphine and heroin;
3) participates in MATERNAL BEHAVIOUR;
4) participates in the regulation of sleep and coordinates complex motor patterns, including vocalizations, temperature regulation, cardiovascular and respiratory responses, sexual behav­ior, and urination.

The RED NUCLEUS, which is located within the RETICULAR FORMATION, communicates motor information between the spinal cord and the cerebellum.

The SUBSTANTIA NIGRA is closely connected with the BASAL GANGLIA - degeneration of the substantia nigra occurs in Parkinson’s disease.

On the dorsal surface of the TECTUM are four bumps:

1) the upper pair, the SUPERIOR COLLICULI, receive input from the optic nerve and use this information to produce visually guided eye movements;
2) the lower pair, the INFERIOR COLLICULI, are involved with auditory reflexes such as turning the head in the direction of a loud noise and participate in the localisation of sounds. They are one stop of the auditory pathway.

Question 18

The THALAMUS

Answer 18

The THALAMUS, which forms the DIENCEPHALON with the HYPOTHALAMUS, consists of two thalamic nuclei, one on either side of the midline. It is considered to be the “gateway to the cortex”. All our sensory systems - with the exception of olfaction - initially converge to the thalamus, which then forwards only the relevant information to the cerebral cortex for further processing.
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Question 19

The HYPOTHALAMUS

Answer 19

The HYPOTHALAMUS forms the DIENCEPHALON with the THALAMUS and lies below it. It is a collection of nuclei which regulate behaviours such as eating, drinking, sex, biorhythms, and temperature control. For example:

1) The VENTROMEDIAL NUCLEUS participates in the regulation of feeding behaviour;
2) The SUPRACHIASMATIC NUCLEUS receives input from the optic nerve and helps set daily rhythms according to the presence of light.

Furthermore, the hypothalamus;

1) is directly connected to the PITUITARY GLAND;
2) controls the AUTONOMIC NERVOUS SYSTEM.

Question 20

The BASAL GANGLIA

Answer 20

The BASAL GANGLIA is a collection of nuclei which participates in MOTOR CONTROL. These nuclei include:

1) The CAUDATE NUCLEUS;
2) The PUTAMEN;
3) The GLOBUS PALLIDUS;
4) The SUBTHALAMIC NUCLEUS;
5) The NUCLEUS ACCUMBENS.

The basal ganglia could be seen as selecting and enabling the execution of motor programs stored by the cortex. Voluntary movement is initiated by the cor­tex, but without healthy functioning in the basal ganglia, cortical commands do not reach the parts of the motor system that actu­ally implement these commands. Degeneration of the basal ganglia, which occurs in Parkinson’s disease and in Huntington’s disease, produces characteristic disorders of movement

Question 21

The LIMBIC SYSTEM

Answer 21

The The LIMBIC SYSTEM participates in learning and emotion. It includes:

1) The HIPPOCAMPUS;
3) The AMYGDALA;
4) The CINGULATE CORTEX;
5) The SEPTAL AREA.

Question 22

The HIPPOCAMPUS

Answer 22

The HIPPOCAMPUS is part of the LiMBIC SYSTEM. It participates in LEARNING and MEMORY, and it is vulnerable to damage as a result of stress - damage to the hippocampus in both hemispheres produces anterograde amnesia.
Structures near and connected to the hippocampus are also included in the limbic system - they participate in the processing of memory.
1) The PARAHIPPOCAMPAL GYRUS;
2) The MAMILLARY BODIES;
3) The FORNIX, which connects the hippocampus to the mammillary bodies.

Question 23

The AMYGDALA

Answer 23

The AMYGDALA, which is part of the LIMBIC SYSTEM, plays an important role in connecting stimuli to their emotional meanings. Electrical stimulation of the amygdala usually produces intense fear and aggressiveness - on the other hand, damage to the amygdala leads to an abnormal emotional calmness

Question 24

The CINGULATE CORTEX

Answer 24

The CINGULATE CORTEX, which is part of the LIMBIC SYSTEM, is found on the inner surface of the cerebral cortex. It is divided in:

1) ANTERIOR CINGULATE CORTEX, which is able to exert cognitive influence over emotion - reduced activity in the ACC is associated with poor emotional control;
2) POSTERIOR CINGULATE CORTEX, which plays a role in eye movements, spatial orientations and memory.

Question 25

The SEPTAL AREA

Answer 25

The SEPTAL AREA, which is part of the LIMBIC SYSTEM, is located anterior to the thalamus and hypothalamus and participates in REWARD.

Question 26

The CORTEX

Answer 26

Unlike the spinal cord, the cerebral hemispheres are organized with gray matter on the outside and white matter on the inside. The cortical surface is wrinkled, with sulci and gyri, for it provides more sur­face area for cortical cells.
The cells of the cerebral cortex are organized in 6 layers, numbered from the outermost to the innermost:
1) Layer 1 has no cell bodies at all - it is made up of the nerve fibers of cells forming connections with other layers;
2) Layers 2 and 4 contain large numbers of small cells known as GRANULE CELLS.
3) Layers 3 and 5 are characterized by large numbers of the triangular-shaped pyramidal cells.
4) Layer 6 has many types of neurons, which merge into the white mat­ ter that lies below the cortical layers.

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Question 27

The PERIPHERAL NERVOUS SYSTEM

Answer 27

The PNS, which is one of two components of the nervous system, includes:

1) the SOMATIC NERVOUS SYSTEM
2) The AUTONOMIC NERVOUS SYSTEM.

Question 28

The SOMATIC NERVOUS SYSTEM

Answer 28

The SOMATIC NERVOUS SYSTEM, which is one of carries sensory information to the CNS and transmit motor signals from the CNS to the body. It consists of:

A) 12 CRANIAL NERVES:

1) OLFACTORY - sensory;
2) OPTIC - sensory;
3) OCULOMOTOR - motor, eye movements;
4) TROCHLEAR - motor, eye movements,
5) TRIGEMINAL, sensory and motor, facial expression feedback and chewing;
6) ABDUCENS - motor, eye movements;
7) FACIAL, sensory and motor, taste and facial expression;
8) AUDITORY, sensory;
9) GLOSSOPHARYNGEAL, sensory and motor, throat;
10) VAGUS, sensory and motor, internal organs.
11) SPINAL ACCESSORY, motor, neck;
12) HYPOGLOSSAL, motor, tongue.

B) 31 pairs of SPINAL NERVES:
Each spinal nerve is also known as a MIXED NERVE because it contains:
1) a sensory, or AFFERENT, nerve, which arise from the dorsal part of the spinal cord;
2) a motor, or EFFERENT nerve, which arise from the ventral part of the spinal cord.

The afferent nerve swells into the DORSAL ROOT GANGLION before joining the efferent nerve and forming the mixed. Afferent nerves contain both myelinated and unmyelinated fibers, whereas efferent nerves are all myelinated in the human adult.

Question 29

The AUTONOMIC NERVOUS SYSTEM

Answer 29

The AUTONOMIC NERVOUS SYSTEM, with the SOMATIC NERVOUS SYSTEM, is part of the PERIPHERAL NERVOUS SYSTEM. It is divided in:

1) The SYMPATHETIC NERVOUS SYSTEM;
2) The PARASYMPATHETIC NERVOUS SYSTEM;
3) The ENTERIC NERVOUS SYSTEM.

The sympa­thetic and parasympathetic systems transmit commands to the glands and organs from the CNS. These two systems usually have opposite effects on the same set of organs, but there are many instances in which both systems operate coopera­tively and simultaneously.

Under the guidance of the HYPOTHALAMUS, the ANS:

1) controls the heart, lungs, digestive system and other organs;
2) participates in regulatory functions such as circulation, secretion, digestion, urination and defecation;
3) produce reflexes such as respiration, sneezing, couching, vomiting and swallowing.

People can learn to consciously control a number of autonomic processes, such as lowering blood pressure, through specialized training in BIOFEEDBACK.

Question 30

The SYMPATHETIC NERVOUS SYSTEM and the PARASYMPATHETIC NERVOUS SYSTEM

Answer 30

The SYMPATHETIC NERVOUS SYSTEM is known as the fight-or-flight system - it manages arousal and copes with emergencies by preparing the body for action. It prepares the body by shutting down low-priority systems and putting blood and oxygen into the most necessary parts of the body - salivation and digestion are put on standby.
Axons from neurons in the THORACIC and LUMBAR segments of the spinal cord communicate with a series of ganglia just outside the cord known as the SYMPATHETIC CHAIN, which then communicates with target organs. Consequently, input from the sympathetic chain arrives at all of the target organs simultaneously, providing aa coordinated response indispensable for survival.

The PARASYMPATHETIC NERVOUS SYSTEM provides rest and energy restore. Neurons in the BRAIN and SACRAL divisions of the spinal cord travel some distance before synapsing with parasympathetic ganglia, which are located near their target organs. Because timing is not as important to parasympathetic activity as it is to sympathetic activity, the coordination provided by a chain is not necessary.

Because the same organs receive input from both the sympathetic and parasympa­thetic systems, it is important for the organs to have a way to identify the source of the input. Both systems use the chemical messenger ACH to communicate with their ganglia. At the target organ, however, the parasympathetic nervous system continues to use ACH whereas the sympathetic nervous system uses NOREPINEPHRINE.

Question 31

The ENDOCRINE SYSTEM

Answer 31

The ENDOCRINE SYSTEM consists of several glands which release hormones into the body - it is controlled by the HYPOTHALAMUS. Some of these glands are:

1) the PINEAL GLAND, which participates in the maintenance of sleep-waking cycles;
2) the PITUITARY GLAND, which has great influence on several other glands of the system - it can stimulate the release of sex hormones by the ovaries and testes.