Anatomical Terminology & Nervous System

• Chapter covers Neuroanatomy
• This section contains basic anatomy and neuroanatomy, so memorization of pictures is important
• Memorization of different brain and body parts can be aided with mnemonic devices
• Learning is reinforced from multiple exposures to information

Learning objectives

• Define terms used to describe brain anatomy or neuroanatomy
• Describe the principal functions of certain brain areas
• List the four lobes of the cerebral cortex and their principal functions
• Discuss past methods for assessing the relationship between brain and behavior

Anatomical terms

• Apply anatomical terms to the nervous system

Anatomical Directions for the body

• Rostral: Towards the nose or front of the body
• Caudal: Towards the tail
• Dorsal: Refers to the back or the top of the head
• Ventral: Refers to the front or towards the belly
• Ipsilateral: Refers to structures on the same side of the body
• Contralateral: Refers to structures on the opposite side of the body
• If the left cerebral cortex controls the contralateral hand it controls the right hand

Anatomical terms

• Dorsal is toward the back, away from the ventral or stomach side and the top of the brain
• Ventral is toward the stomach, away from the dorsal or back side
• Anterior is toward the front end
• Posterior is toward the rear end
• Superior is above another part
• Inferior is below another part
• Lateral is toward the side, away from the midline
• Medial is toward the midline, away from the side
• Proximal is located close or approximate to the point of origin or attachment
• Distal is located more distant from the point of origin or attachment
• Ipsilateral is on the same side of the body
• Contralateral is on the opposite side of the body
• Coronal plane is a plane that shows brain structures as seen from the front
• Sagittal plane is a plane that shows brain structures as seen from the side
• Horizontal or transverse plane is a plane that shows brain structures as seen from above

The nervous system

• Central nervous system (CNS) consists of the brain and the spinal cord
• Peripheral nervous system (PNS) connects the brain and spinal cord to the rest of the body
• Somatic nervous system is part of the peripheral nervous system and is associated with voluntary control of body movements via skeletal muscles
• Autonomic nervous system controls the heart, intestines, and other organs

Autonomic nervous system

• Sends and receives messages to regulate the automatic behaviors of the body including heart rate, blood pressure, respiration, and digestion
• The autonomic nervous system is divided into two subsystems: the sympathetic and parasympathetic nervous systems

Sympathetic Nervous System

• Is a network of nerves that prepares the organs for rigorous activity increases heart rate, blood pressure, respiration which creates the "fight or flight" response
• It is composed of ganglia on the left and right of the spinal cord

Parasympathetic Nervous System

• Facilitates vegetative and nonemergency responses
• Decreases functions increased by the sympathetic nervous system
• It is composed of long preganglion axons extending from the spinal cord and short postganglionic fibers that attach to the organs themselves
• Dominates during relaxed states because the neurotransmitters for the parasympathetic nervous system are released

Neurotransmitters in the ANS

• Postganglionic axons of the parasympathetic nervous system mainly release acetylcholine
• The sympathetic nervous system mainly uses norepinephrine or noradrenaline for fight or flight responses

Meninges

• Protective sheath or membrane around the brain and spinal cord
• The three layers of the meninges include: dura mater, arachnoid, and pia mater
• The outer layer, durable, thick, and tough is the Dura Mater
• The middle layer is soft and spongy, the arachnoid
• The layer that is closely attached to the brain and spinal cord and where the smaller blood vessels of the brain and spinal cord are, is the Pia Mater
• The meninges contain pain receptors
• Meningitis is inflammation of the meninges that is painful and can potentially be fatal
• Swollen blood vessels in the meninges are one of the causes of migraine headaches
• Migraines are believed to be caused by abnormal brain activity in the trigeminal cranial nerve which releases neuropeptides leading to inflamed meninges

Meningitis

• Vaccines help to prevent meningitis
• Bacterial Meningitis is treated with combinations of steroids and various antibiotics
• People who get mild Viral Meningitis usually recover completely in 7 to 10 days with treatment
• Antiviral medicine may help people with meningitis caused by viruses such as herpesvirus and influenza

Ventricles

• Are four fluid-filled cavities within the brain and central canal that contain cerebrospinal fluid
• Cerebrospinal fluid (CSF) is a clear fluid found in the brain and spinal cord providing "cushioning" for the brain and reservoir of hormones and nutrition for the brain and spinal cord
• CSF is made in the choroid plexus in the ventricles of the brain

Hydrocephalus

• Condition characterized by a blocked CSF flow due to a brain tumor, or maladaptive cerebral aqueduct, which results in enlarged ventricles due to increased pressure
• Walls of ventricles expand to produce a condition known as obstructive hydrocephalus
• Permanent or fatal brain damage result if the condition is not reversed

Early brain development

• The three major divisions of the vertebrate brain consist of the forebrain, the midbrain and the hindbrain

Hindbrain

• Consists of the: medulla oblongata, pons, and cerebellum
• Is located at the posterior portion of the brain

Medulla oblongata

• This is located just above the spinal cord acting as an enlarged extension of the spinal cord
• It is responsible for vital reflexes such as breathing, heart rate, vomiting, salivation, coughing and sneezing
• Cranial nerves emerge from the Medulla to control sensations from the head, muscle movements in the head, and many parasympathetic outputs

Opioids and Cocaine

• Opiates and cocaine can have profound effects on the medulla nuclei if a person has an overdose on these substances
• Damage to the medulla can be fatal because of its prominent role in breathing and heart rate

Cranial Nerves

• There are twelve pairs of cranial nerves that emerge directly from the brain, and relay information between the brain and parts of the body primarily to and from the head and neck
• Each cranial nerve is paired and present on both sides of the brain
• The numbering of the cranial nerves is based on the order in which they emerge from the brain front to back (brainstem)

Mnemonic device helps recall the 12 cranial nerves

• Three 'O's: Olfactory, Optic, Oculomotor
• Two 'T's: Trochlear, Trigeminal
• One 'A': Abducens
• One 'F': Facial
• One 'A': Auditory
• Vestibulocochlear
• 'G': Gut- Glossopharyngeal
• 'V': Vagus
• 'S': So - Spinal Accessory
• 'H': High- Hypoglossal

Functions of each Cranial Nerve

• I. Olfactory relates to smell
• II. Optic relates to Vision
• III. Oculomotor relates to Control of eye movements and pupil constriction
• IV. Trochlear relates to Control of eye movements
• V. Trigeminal is skin sensations from most of the face and controls jaw muscles for chewing and swallowing
• VI. Abducens relates to Control of eye movements
• VII. Facial relates to Taste from the anterior two thirds of the tongue and controls facial expressions, crying, salivation, and dilation of the head's blood vessels
• VIII. Auditory or Statoacoustic relates to Hearing and equilibrium
• IX. Glossopharyngeal relates to Taste and other sensations from the throat and posterior third of the tongue and controls swallowing, salivation, and throat movements during speech
• X. Vagus relates to Sensations from neck and thorax and Control of the throat, esophagus, and larynx parasympathetic nerves to the stomach, intestines, and other organs
• XI. Accessory relates to Control of neck and shoulder movements
• XII. Hypoglossal relates to Control of muscles of the tongue

Pons

• Lies on each side of the medulla (ventral and anterior)
• "Pons" is Latin for "bridge"
• Important for breathing, communication between different parts of the brain, sleep, and arousal
• The brainstem controls autonomic survival behaviors, breathing, hear rate, swallowing, reflexes to sight/ sound, sweating, blood pressure, and balance
• Remember, that the brainstem consists of the midbrain, pons, and medulla

Cerebellum

• Structure located in the hindbrain with many deep folds
• Helps regulate motor movement, posture, balance, and coordination
• Also important for shifting attention between auditory and visual stimuli

Midbrain

• Mesencephalon (midbrain) consists of the tectum and the tegmentum
• Tectum is the "roof"
• It is the dorsal portion of the midbrain
• The Superior colliculus is related to processing of visual information and some eye movement
• The Inferior colliculus (main auditory sound center in the body) is important for signal integration and pitch discriminations et
• Tegmentum is the "covering" and it is located on the portion below the tectum consisting of the following nuclei
  • Substantia nigra (black substance)
• Ventral tegmental area
• Collectively areas that comprise the tegmentum are involved in different aspects of motor function.
• Loss of DA neurons in Substantia nigra is linked to Parkinson's disease

Forebrain

• The most anterior and prominent part of the mammalian brain, with two cerebral hemispheres
• Forebrain consists of the outer cerebral cortex and other subcortical regions (e.g., thalamus, limbic system)
• Cortex means "bark"
• Consists of the cellular layers on the outer surface of the cerebral hemispheres divided into two halves
• These halves are joined by two bundles of axons known as the corpus callosum and anterior commissure
• Each side receives sensory information and controls motor movement from the opposite (contralateral) side of the body
• White matter (e.g., anterior commissure) is composed of myelinated axons
• Gray matter (e.g., cerebral cortex) is composed of the cell bodies, neurons and glia that give it the gray appearance
• Folding of the cerebral cortex creates gyri and sulci which separate brain regions and increase the brain's surface area leading to increased cognitive ability
• Gyri or gyrus are folds or bumps in the brain
• Sulci or sulcus are indentations or grooves in the brain; fissures are the larger grooves

Cerebral Cortex

• Some functions are lateralized they are located primarily on one side of the brain
• The left hemisphere controls sensory stimulus from the right side of the body, motor control of the right side of body, speech, language and comprehension, analysis and calculations, time and sequencing, and recognition of words, letters and numbers
• The right hemisphere control sensory stimulus from the left side of body, motor control of left side of the body, creativity, spatial ability, context or perception, and recognition of faces , places and objects

Corpus Callosum

• Although the two cerebral hemispheres perform different functions, perceptions and memories are unified via the corpus callosum the largest white matter tract
• Emerging evidence suggests that weakened integrity of the callosum contributes to a decline in cognitive function in aging adults
• On the flip side, increased callosal thickness correlates with intelligence, processing speed, and problem-solving abilities

Facts about the Brain

• Male brains are larger in volume relative to female brains probably due to increased androgen and female volume size
• There are sex differences in lateralization of the brain
• On average, the female brain matures and develops faster than the male brain
• Despite early maturation of female brain, in otherwise, healthy females, the female brain ages slower than healthy male brain
• All of our brains shrink with age

Test your knowledge of anatomical terminology related to the nervous system. Questions cover directional terms, planes of section, autonomic nervous system functions, and cerebrospinal fluid. Understand the roles of sympathetic and parasympathetic branches.