Chapter 11: The nervous system
There are _____ pairs of cranial nerves
12
Ceruminous glands
glands that produce earwax
Cerebral hemispheres
the right and left halves of the cerebrum.
The brain is divided into four main parts:
1. The brainstem controls breathing, heartbeat rates and reactions to visual and auditory stimuli. 2. The diencephalon includes the thalamus and the hypothalamus, which controls many functions, including those related to homeostasis. 3. The cerebrum controls intellectual processes and emotions, while the cerebellum maintains body posture and balance. 4. The autonomic nervous system controls all the involuntary functions of the body such as regulating our internal organs and controlling glands. The special senses are part of the nervous system and include sight, hearing and balance, smell and taste.
Infundibulum
1. part of the hypothalamus that connects to the pituitary gland; 2. open end of fallopian tube.
Cranial Nerves (IX - XII)
1.The glossopharyngeal nerve (IX) is a mixed nerve. It controls swallowing and senses taste. Its parasympathetic function controls salivary glands. 2.The vagus nerve (X) is a mixed nerve. It controls skeletal muscle movements in the pharynx, larynx and palate. It conveys impulses for sensations in the larynx, viscera and ear. Its parasympathetic function controls viscera in the thorax and abdomen. 3.The accessory nerve (XI) is a motor nerve. It originates from the brainstem and the spinal cord. It helps control swallowing and movements of the head. 4.Finally, the hypoglossal nerve (XII) is a motor nerve. It controls the muscles involved in speech and swallowing and its sensory fibers conduct impulses for muscle sense.
Cranial Nerves (I-IV)
1.The olfactory nerve (I) is entirely sensory and conveys impulses related to smell. 2.The optic nerve (II) is also entirely sensory and conveys impulses related to sight. 3.The oculomotor nerve (III) is a motor nerve. It controls movements of the eyeball and upper eyelid and conveys impulses related to muscle sense or position called proprioception. Its parasympathetic function causes constriction of the pupil of the eye. 4.The trochlear nerve (IV) is a motor nerve. It controls movement of the eyeball and conveys impulses related to muscle sense. It is the smallest of the cranial nerves.
Cranial Nerves (V - VIII)
1.The trigeminal nerve (V) is a mixed nerve and it is the largest of the cranial nerves. It has three branches: the maxillary, the mandibular and the ophthalmic. It controls chewing movements and delivers impulses related to touch, pain and temperature in the teeth and facial area. 2.The abducens nerve (VI) is a motor nerve that controls movement of the eyeball. 3.The facial nerve (VII) is a mixed nerve. It controls the muscles of facial expression and conveys sensations related to taste. Its parasympathetic function controls the tear and salivary glands. 4.The vestibulocochlear nerve (VIII) is entirely sensory. It transmits impulses related to equilibrium and hearing.
The brain weighs about _____.
3 pounds
What does the Hypothalamus control?
It is the center for mind-over-body phenomena. When we hear of unexplainable cures in people diagnosed with terminal illness but who refused to accept the diagnosis and recovered, the hypothalamus may have been involved in this mind controlling the body phenomenon. It is the hypothalamus that controls our feelings of rage and aggression. It controls our normal body temperature. It contains our thirst center, informing us of when and how much water we need to sustain our bodies. It maintains our waking state and sleep patterns, allowing us to adjust to different work shifts or jetlag travel problems within a day or so. It also regulates our food intake.
Sulci (Sulcus)
a furrow or groove.
Pons varolii
bridge that connects the spinal cord with the brain and parts of the brain with each other.
The surface of the cerebrum made up of gray matter is known as the _____ _____.
cerebral cortex
Facial nerve VII
controls the muscles of facial expression and conveys sensations related to taste
Ventral cerebral peduncles
convey impulses from the cerebral cortex to the pons and spinal cord.
The three cranial meninges are the outer _____ mater, the middle _____ mater and the inner _____ mater
dura, arachnoid, pia
External auditory meatus
ear canal
Cerebrum
the bulk of the brain consisting of two cerebral hemispheres. Its surface is composed of gray matter and is referred to as the cerebral cortex. Beneath the cortex lies the cerebral white matter. A prominent fissure, the longitudinal fissure, separates the cerebrum into right and left halves or cerebral hemispheres. On the surface of each hemisphere are numerous folds called gyri with intervening grooves called sulci. The folds increase the surface area of the cortex, which has motor areas for controlling muscular movements, sensory areas for interpreting sensory impulses and association areas concerned with emotional and intellectual processes. A deep bridge of nerve fiber known as the corpus callosum connects the two cerebral hemispheres.
Auditory or eustachian tube
the ear canals located in the middle ear that equalize air pressure preventing hearing distortion; eustachian tubes
Exceptions
Most organs that receive autonomic motor neurons are innervated by both the parasympathetic and sympathetic divisions. However, there are some exceptions: blood vessels and sweat glands are innervated by sympathetic neurons, and smooth muscles associated with the lens of the eye are controlled by parasympathetic neurons.
The _____ lobe is behind the frontal lobe
Parietal
The superior part of the diencephalon that plays a role in conscious recognition of pain is the _____.
Thalamus
Introducing the Ventricles
The brain has four ventricles. There are two lateral ventricles in each side or hemisphere of the cerebrum under the corpus callosum (KOR-pus kah-LOH-sum). The third ventricle is a slit between and inferior to the right and left halves of the thalamus, and situated between the lateral ventricles. Each lateral ventricle connects with the third ventricle by a narrow oval opening called the interventricular foramen or foramen of Monroe
Introducing the Principal Parts of the Brain
The brain is one of the largest organs of the body. It weighs about 3 pounds in an average adult. It is divided into four major parts: 1. the brainstem, which consists of three smaller areas, the medulla oblongata, the pons varolii and the midbrain; 2. the diencephalon, consisting of the thalamus and the hypothalamus 3. the cerebrum; and the cerebellum.
Protecting the Brain: Meninges
The brain is protected by the cranial bones and the meninges. The cranial meninges is the name given to the meninges that protect the brain, and they have the same structure as the spinal meninges: the outer dura mater, the middle arachnoid mater and the inner pia mater.
Temporal Lobe
The temporal lobe is beneath the frontal and parietal lobes and is separated from them by the lateral fissure. It evaluates hearing input and smell as well as being involved with memory processes. It also functions as an important center for abstract thoughts and judgment decisions.
Sylvia is babysitting her little brother, who always seems to have his head in a book. Finally, after the third time asking a question and getting no reply, she says "Do you have a hole in your head or what?" "Actually," he replies, "I have four. They're called ventricles." What are these ventricles and where would you find them?
Ventricles are cavities within the brain. They connect with each other and with the subarachnoid space and central canal. Cerebrospinal fluid is created in and flows through the ventricles. Two lateral ventricles are under the corpus callosum on either side. The third ventricle is a narrow opening between the halves of the thalamus. The fourth ventricle is between the cerebellum and lower brainstem.
Epithalamus
a small area superior and posterior to the thalamus. It contains some small nuclei that are concerned with emotional and visceral responses to odor. It contains the pineal gland.
Midbrain
also called the mesencephalon contains the ventral cerebral peduncles that convey impulses from the cerebral cortex to the pons and spinal cord. It also contains the dorsal tectum, which is a reflex center that controls the movement of the eyeballs and head in response to visual stimuli; it also controls the movement of the head and trunk in response to auditory stimuli, such as loud noises.
Pineal gland
an endocrine gland located in the epithalamus of the diencephalon that produces the hormone melatonin.
Interventricular foramen/foramen of Monroe
another name for the foramen of Monroe; connects each lateral ventricle with the third ventricle of the brain
Ventricles
cavities within the brain that connect with each other
The third and fourth ventricles are connected by the _____ _____.
cerebral aqueduct
Optic nerve II
conveys impulses related to sight
Olfactory nerve I
conveys impulses related to smell
The brain is protected by the _____ _____ and the _____.
cranial bones, meninges
Decussation of pyramids
crossing of the tracts in the brain stem.
Corpus callosum
deep bridge of nerve fibers that connects the cerebral hemispheres.
Auricle
external appendage of an atrium
Longitudinal fissure
fissure separating the cerebrum into right and left halves.
Aqueous humor
fluid in the anterior compartment of the eye located in front of the lens
Gyri
folds on the surface of each hemisphere of the cerebrum.
Frontal lobe
forms the anterior portion of each cerebral hemisphere.
The elevations or folds on the surface of the cerebrum are called____.
gyri
Accessory nerve XI
helps control swallowing and movements of the head
Pituitary gland
hypophysis; a major gland of the endocrine system.
Diencephalon
one of the four major parts of the brain consisting of the thalamus and the hypothalamus. superior to the midbrain and between the two cerebral hemispheres. It also surrounds the third ventricle. It is divided into two main areas: the thalamus and the hypothalamus. It also contains the optic tracts and optic chiasma where optic nerves cross each other; the infundibulum, which attaches to the pituitary gland; the mamillary bodies, which are involved in memory and emotional responses to odor; and the pineal gland, which is part of the epithalamus. The pineal gland is a pinecone-shaped endocrine gland that secretes melatonin, which affects our moods and behavior.
Brainstem
one of the four major parts of the brain; it connects the brain to the spinal cord. The brainstem consists of the medulla oblongata, the pons varolii and the midbrain. It connects the brain to the spinal cord. It is a very delicate area of the brain because damage to even small areas could result in death. The figure to the right shows the parts of the brain and areas of brain function.
Dorsal tectum
reflex center that controls the movement of the eyeballs and head in response to visual stimuli.
The area contained within the medulla having dispersed gray matter is the _____ _____.
reticular formation.
Cerebellum
second largest portion of the brain concerned with coordinating skeletal muscle movements and balance.
Cerebral cortex
surface of the cerebrum.
The autonomic nervous system, a subdivision of the peripheral nervous system, has two parts; they are the _____, which operates under stressful situations, and the _____, which operates under normal non-stressful situations.
sympathetic, parasympathetic
The diencephalon is divided into a superior part, the _____, and an inferior part, the _____.
thalamus, hypothalamus
The optic tracts and optic chiasma are within the _____.
Diencephalon
Trigeminal nerve V
largest of the cranial nerves; controls chewing movements
Tympanic membrane
Eardrum
Cerumen
Earwax
The _____ division of the nervous system prepares the body for stressful situations that require energy expenditure, such as increasing heartbeat and breathing rates.
Sympathetic
Protecting the Brain: Cerebrospinal Fluid
The brain, like the spinal cord, is further protected by the cerebrospinal fluid that circulates through the subarachnoid space around the brain and spinal cord and through the ventricles of the brain. The ventricles are cavities within the brain that connect with each other, with the subarachnoid space of the meninges and with the central canal of the spinal cord. The cerebrospinal fluid serves as a shock absorber for the central nervous system and circulates nutrients
More about the Cerebellum
The cerebellum is made up primarily of white matter with a thin layer of gray matter on its surface called the cerebellar cortex. It functions as a reflex center in coordinating complex skeletal muscular movements, maintaining proper body posture and keeping the body balanced. If damaged, there can be a decrease in muscle tone, tremors, a loss of equilibrium and difficulty in skeletal muscle movements
The Cerebellum: Structure and Function
The cerebellum is the second largest portion of the brain. It is shaped somewhat like a butterfly. It is located beneath the occipital lobes of the cerebrum and behind the pons and the medulla oblongata of the brainstem. It consists of two partially separated hemispheres connected by a centrally constricted structure called the vermis.
And the Fourth Ventricle
The fourth ventricle lies between the cerebellum and the lower brainstem. It connects with the third ventricle via the cerebral aqueduct also known as the aqueduct of Sylvius. The roof of this fourth ventricle has three openings through which it connects with the subarachnoid space of the brain and spinal meninges, thus allowing a flow of cerebrospinal fluid through the spinal cord, the brain and the ventricles of the brain
Frontal Lobe
The frontal lobe forms the anterior portion of each hemisphere. It controls voluntary muscular functions, moods, aggression, smell reception and motivation.
Pons Varolii
The pons varolii is a bridge (pons is Latin for "bridge") that connects the spinal cord with the brain and parts of the brain with each other. Longitudinal fibers connect with the spinal cord or medulla with the upper parts of the brain, and transverse fibers connect with the cerebellum. Its pneumotaxic and apneustic area help control breathing.
Lobes of the Cerebral Hemispheres
The lobes of the cerebral hemispheres are named after the bones of the skull that lie on top of them: 1.Frontal lobe 2.Parietal lobe 3.Temporal lobe 4.Occipital Lobe 5.Insula
Reticular Formation
The medulla also contains an area of dispersed gray matter containing some white fibers. This area is called the reticular formation, which functions in maintaining consciousness and arousal. Within the medulla are three vital reflex centers of this reticular system: the vasomotor center, which regulates the diameter of blood vessels; the cardiac center, which regulates the force of contraction and heartbeat; and the medullary rhythmicity area, which adjusts your basic rhythm of breathing.
Occipital Lobe
The occipital lobe forms the back portion of each hemisphere; its boundaries are not distinct from the other lobes. It functions in receiving and interpreting visual input.
Parietal Lobe
The parietal lobe is behind the frontal lobe and is separated from it by the central sulcus. It is the control center for evaluating sensory information of touch, pain, balance, taste and temperature.
What are the Cranial Nerves?
There are 12 pairs of cranial nerves. Ten pairs originate from the brainstem. All 12 pairs leave the skull through various foramina of the skull. They are designated in two ways: by Roman numerals indicating the order in which the nerves arise from the brain (from the front of the brain to the back) and by names that indicate their function or distribution. Some cranial nerves are only sensory or afferent; others are only motor or efferent. Cranial nerves with both sensory and motor functions are called mixed nerves.
Parts of the Autonomic Nervous System
There are two parts to the autonomic nervous system: 1.Sympathetic division 2.Parasympathetic division
Autonomic nervous system
conducts impulses from the brain and spinal cord to smooth muscle tissue, cardiac muscle tissue and glands. a subdivision of the efferent peripheral nervous system. It functions automatically without conscious effort. It regulates the functions of internal organs by controlling glands, smooth muscles and cardiac muscle. It assists in maintaining homeostasis by regulating heartbeat and blood pressure, breathing and body temperature. This system helps us to deal with emergency situations, emotions and physical act. Receptors within organs send sensory impulses to the brain and spinal cord. Motor impulses travel along peripheral nerve fibers that lead to ganglia outside the central nervous system within cranial and spinal nerves. These ganglia are part of the autonomic nervous system.
Cerebral aqueduct/aqueduct of Sylvius
connects the third and fourth ventricles of the brain; also called aqueduct of Sylvius
Ciliary body
consists of smooth muscles that hold the lens in place
Parietal lobe
control center in the brain for evaluating sensory information of touch, pain, balance, taste and temperature.
Abducens nerve VI
controls movement of the eyeball
Trochlear nerve IV
controls movement of the eyeball and conveys impulses related to muscle sense
Oculomotor nerve III
controls movements of the eyeball and upper eyelid and conveys impulses related to muscle sense
Vagus nerve X
controls skeletal muscle movements in the pharynx, larynx and palate
Glossopharyngeal nerve IX
controls swallowing and carries taste impulses
The insula is located deep within the _____ _____.
lateral sulcus
Insula
lobe in the brain that separates the cerebrum into frontal, parietal and temporal lobes. A fifth lobe, the insula, is embedded deep in the lateral sulcus. The central sulcus separates the frontal and parietal lobes. The lateral sulcus separates the cerebrum into frontal, parietal and temporal lobes.
A prominent fissure that separates the cerebrum into right and left halves or hemispheres is known as the ____.
longitudinal fissure
The mamillary bodies are involved in _____ and _____ _____.
memory, emotional response
Midbrain/mesencephalon
mesencephalon; contains the ventral cerebral peduncles.
Parasympathetic division
part of the autonomic nervous system that operates under normal nonstressful conditions. operates under normal non-stressful conditions. It also functions in restoring the body to a restful state after a stressful experience, thus counterbalancing the effects of the sympathetic division. The preganglionic fibers of the parasympathetic division arise from the brainstem and the sacral region of the spinal cord. They lead outward in the cranial and sacral nerves to ganglia located close to the viscera. The postganglionic fibers are short and go to the muscles or glands within the viscera to bring about their effects. The preganglionic and the postganglionic fibers of the parasympathetic division use acetylcholine as the neurotransmitter into the synapses. parasympathetic division stimulates digestion, urination and defecation. It also counteracts the effects of the sympathetic division by slowing down heartbeat rate, lowering blood pressure and slowing the breathing rate. It is also responsible for the constriction of the pupil of the eye. This division is occasionally called the rest and repose system.
Sympathetic division
part of the autonomic nervous system that prepares the body for stressful situations that require energy expenditure. prepares the body for stressful situations that require energy expenditure, such as increasing heartbeat and breathing rates to flee from a threatening situation. The fibers of the system arise from the thoracic and lumbar regions of the spinal cord. Their axons leave the cord through the ventral roots of the spinal nerves but then leave the spinal nerve and enter members of a chain of paravertebral ganglia extending longitudinally along the side of the vertebral column. Leaving the paravertebral ganglion, another neuron, the postganglionic fiber, goes to the effector organ. The sympathetic division uses acetylcholine in the preganglionic synapses as a neurotransmitter but uses norepinephrine (or noradrenalin) at the synapses of the postganglionic fibers. This system is occasionally called the fight or flight system because it prepares us to face a threat or flee quickly from it. prepares us for physical activity by increasing blood pressure and heartbeat rate, it dilates respiratory passageways for increased breathing rates and it stimulates sweating. It also causes the release of glucose from the liver as a quick source of energy while inhibiting digestive activities. This system is occasionally called the fight or flight system because it prepares us to face a threat or flee quickly from it.
Medulla oblongata
part of the brain stem that contains all the ascending and descending tracts that connect between the spinal cord and various parts of the brain. contains all the ascending and descending tracts that connect between the spinal cord and various parts of the brain. These tracts make up the white matter of the medulla. Some motor tracts cross as they pass through the medulla. The crossing of the tracts is called decussation of pyramids and explains why motor areas on one side of the cortex of the cerebrum control skeletal muscle movements on the opposite side of the body.
Hypothalamus
part of the brain that controls secretions from the pituitary gland. the inferior part of the diencephalon and, despite its small size, controls many bodily functions related to homeostasis. It controls and integrates the autonomic nervous system. It receives sensory impulses from the internal organs. It is the intermediary between the nervous system and the endocrine system because it sends signals and controls the pituitary gland.
Temporal lobe
part of the cerebral hemisphere that evaluates hearing input and smell.
Occipital lobe
part of the cerebrum that functions in receiving and interpreting visual input.
Mamillary bodies
part of the diencephalon involved in memory and emotional responses to odor
Optic tracts
part of the diencephalon involved with the sense of sight.
Optic chiasma
part of the diencephalon where optic nerves cross each other.
Choroid
the second layer of the wall of the eye containing blood vessels and pigment cells
Thalamus
the second part of the diencephalons. the superior part of the diencephalon and the principal relay station for sensory impulses that reach the cerebral cortex coming from the spinal cord, brainstem and parts of the cerebrum. It also plays an important role as an interpretation center for conscious recognition of pain and temperature and for some awareness of crude pressure and touch.
Vestibulocochlear nerve VIII
transmits impulses related to equilibrium and hearing
Cornea
transparent part of the outermost layer of the eye that permits light to enter the eye
The midbrain contains the _____ _____ _____.
ventral cerebral peduncles.
Cavities within the brain that connect with each other, with the subarachnoid space of the meninges, and with the central canal of the spinal cord are known as _____.
ventricles
