1. Meninges Bones, membranes, and fluids surround the organs of the CNS
The brain lies within the cranial cavity of the skull
The spinal cord occupies the vertebral canal within the vertebral column
Layered between the bony coverings and soft tissues of the CNS lie membranes called the meninges:
Dura mater
Arachnoid mater
Pia mater
Epidural space lies between the dural sheath and the bony walls of the cranium

2. Meninges – Dura Mater Outermost layer of the meninges
Composed primarily of tough, white, fibrous connective tissue
Contains many blood vessels and nerves
Attaches to the inside of the cranial cavity
Forms the internal periosteum of the surrounding skull bones
In some regions, extends inward between lobes of the brain and forms partitions that support and protect these parts.
Continues into the vertebral canal as a strong, tubular sheath that surrounds the spinal cord

3. Meninges – Arachnoid Mater
Thin weblike membrane
No blood vessels
Lies between the dura mater and the pia mater
Between the arachnoid mater and pia mater is a subarachnoid space
Contains a clear, watery fluid
Contains cerebrospinal fluid (CSF)
Flows continuously between the brain and spinal cord
Contains glucose and electrolytes

4. Meninges – Pia Mater
Very thin layer closest to the brain and spinal cord
Hugs the surfaces of the brain and spinal cord
Passes over higher areas
Dips into depressions
Contains many nerves and blood vessels that nourish underlying cells of the brain and spinal cord

5. Subdural Hematoma
Can be caused by a blow to the head or some other head trauma
Blood vessels associated with the brain are broken
The blood can collect beneath the dura mater
Increases the pressure between the rigid bones of the skull and the soft tissues of the brain
Unless the accumulating blood is evacuated, compression of the brain can lead to loss of function or even death.

6. Spinal Cord
Slender nerve column that passes downward from the brain into the vertebral canal
Continuous with brain
Begins where nervous tissue leaves the cranial cavity at the foramen magnum
Tapers to a point
Usually terminates between the first and second lumbar vertebrae.
Fibers past the end of the spinal cord serve the lower limbs and are called the cauda equina (horse’s tail)

7. Structure of the Spinal Cord
Consists of 31 segments
Each segment gives rise to a pair of spinal nerves which branch to various body parts and connect them to the CNS
The majority of neurons in the gray matter of the spinal cord are interneurons
Neck Region
Thickening of the spinal cord
Called the cervical enlargement
Supplies nerves to the upper limbs
Lower Back Region
Called the lumbar enlargement
Gives off nerves to the lower limbs

8. Structure of the Spinal Cord

9. Structure of the Spinal Cord
Two grooves extend the length of the spinal cord, dividing it into right and left halves:
Deep anterior median fissure
Shallow posterior median sulcus
A cross section of the cord reveals a core of gray matter within white matter
The gray matter roughly resembles a butterfly with its wings spread
The upper wings of gray matter are called the posterior horns
The lower wings of gray matter are called the anterior horns
In the thoracic and upper lumbar segments, the lateral horn is found between the posterior and lateral horns

10. Structure of the Spinal Cord
Gray matter divides the white matter of the spinal cord into 3 regions on each side:
Anterior funiculus
Lateral funiculus
Posterior funiculus
Each funiculus (plural: funiculi) consists of longitudinal bundles that comprise major nerve pathways called nerve tracts
A horizontal bar of gray matter in the middle of the spinal cord is the gray commisure
Connects the wings of gray matter on the right and left sides
Surrounds the central canal, which contains CSF

12. Functions of the Spinal Cord
Two major functions:
Conducting nerve impulses
Serving as a center for spinal reflexes
The tracts that carry sensory information to the brain are called ascending tracts
The tracts that carry motor impulses from the brain to effectors are called descending tracts

13. Functions of the Spinal Cord
In addition to providing a pathway for nerve tracts
The spinal cord functions in many reflexes
Stretch reflexes (Ex: patellar reflex)
Withdrawal reflexes
These are called spinal reflexes because their reflex arcs pass through the spinal cord

14. Brain Composed of about 100 billion multipolar neurons that:
Communicate with each other
Communicate with neurons in other parts of the nervous system
Four major portions:
The cerebrum
The diencephalon
The brainstem
The cerebellum

15. Brain - Cerebrum Largest part of brain
Includes nerve centers associated with sensory and motor functions
Provides higher mental functions including:
Memory
Reasoning
Consists of two large masses called the left and right cerebral hemispheres
Essentially mirror images of each other
The corpus callosum is a deep bridge of nerve fibers that connects the cerebral hemispheres
A layer of dura mater separates them

16. Brain – Cerebrum (cont.)
The surface of the cerebrum
Has many ridges called convolutions or gyri (singular: gyrus)
Ridges are separated by grooves
Shallow grooves are called sulci (singular sulcus)
Deeper grooves are called fissures
Form distinct patterns
Longitudinal fissure separates the right and left cerebral hemispheres
Transverse fissure separates the cerebrum from the cerebellum
Several sulci separate each hemisphere into lobes

17. Lobes of the Cerebrum Frontal Lobe
Forms the anterior portion of each hemisphere
Bordered posteriorly by a central sulcus which extends from the longitudinal fissure at a right angle
Bordered inferiorly by a lateral sulcus which extends from the undersurface of the brain a long its sides

18. Lobes of the Cerebrum Parietal Lobe Posterior to the frontal lobe
Separated from the frontal lobe by the central sulcus
Temporal Lobe
Lies below the frontal and parietal lobes
Separated from frontal and parietal lobes by the lateral sulcus

19. Lobes of the Cerebrum Occipital Lobe
Forms the posterior portion of each cerebral hemisphere
Separated from the cerebellum by a shelf-like extension of the dura mater called the tentorium cerebelli
The boundary between the parietal and temporal lobes is not distinct

20. Lobes of the Cerebrum Insula Located deep within the lateral sulcus
Covered by parts of the frontal, parietal, and temporal lobes
A circular sulcus separates the insula from the other lobes

21. Cerebral Cortex Thin layer of gray matter
Outermost portion of the cerebrum
Covers the gyri and dips into the sulci and fissures
Contains nearly 75% of all the neuron cell bodies in the nervous system
Beneath the cortex is a mass of white matter that makes up the bulk of the cerebrum

22. Functions of the Cerebrum
Provides higher brain functions
Contains centers for interpreting sensory impulses arriving from sense organs
Contains centers for initiating voluntary muscular movements
Stores the information that comprises memory
Utilizes stored memory for reasoning
Intelligence and personality stem from cerebral activity

23. Functional Areas of the Cerebral Cortex
Although the regions of the cerebral cortex can overlap, it can be divided into three areas:
Motor areas
The primary motor cortex lies in the frontal lobes just in front of the central sulcus
The motor area of the right cerebral hemisphere controls the skeletal muscles on the left side
The motor area of the left cerebral hemisphere controls the skeletal muscles on the right side
The frontal eye field is anterior and lateral to the primary motor cortex
Controls voluntary movements of the eyes and eyelids
Another region anterior to the primary motor cortex controls the muscular movements of the hands and fingers that make skills such as writing possible

24. Functional Areas of the Cerebral Cortex

25. Functional Areas of the Cerebral Cortex
Sensory areas
Located in several lobes of the cerebrum
Interpret impulses that arrive from sensory receptors
Produce feelings or sensations
Anterior parietal lobes near the central sulcus
Sensations from all parts of the skin
Posterior occipital lobes (visual area)
Effect vision
Temporal lobes (auditory area)
Contain centers for hearing
Near the base of the central sulci near the lateral sulci
Contain centers for taste
Deep within cerebrum
Contain centers for smell

26. Functional Areas of the Cerebral Cortex
Sensory areas (cont.)
Cross over like motor fibers, either in the spinal cord or the brain stem
Centers in the right cerebral hemisphere interpret impulses originating from the left side
Centers in the left cerebral hemisphere interpret impulses originating from the right side
Association areas
Neither primarily sensory or motor functions
Connect with one another and with other brain structures
Analyze and interpret sensory experiences
Oversee memory, reasoning, verbalizing, judgment, and emotion

27. Functional Areas of the Cerebral Cortex

28. Functional Areas of the Cerebral Cortex
Association areas (cont.)
Occupy:
Anterior portions of the frontal lobes
Control higher intellectual processes
Concentrating, planning complex problem solving, and judging the possible consequences of behavior
Widespread in lateral portions of the parietal, temporal, and occipital lobes
Weirnicke’s area (sensory speech area)
Found in the parietal lobe near the temporal lobe
Usually in left hemisphere
Necessary for understanding written and spoken language

29. Functional Areas of the Cerebral Cortex
Association areas (cont.)
Broca’s area (motor speech area)
Found in the frontal lobe superior to the lateral sulcus
Usually in the left hemisphere
Generates the movements of muscles necessary for speech
Association areas also provide memory of visual scenes, music, and other complex sensory patterns
Association areas near the occipital lobe adjacent to the visual centers are important in
Analyzing visual patterns
Combining visual images with other sensory experiences (recognizing an object or other person)

30. Functional Areas of the Cerebral Cortex

31. Hemisphere Dominance
Both cerebral hemispheres participate in basic functions such as
Receiving and analyzing sensory impulses
Controlling skeletal muscles
Storing memory

32. Hemisphere Dominance Most people have a dominant cerebral hemisphere
Controls the ability to use and understand language
Controls language-related activities of speech, writing, and reading
Broca’s area controls the muscles that function in speaking
Most people are left hemisphere dominant

33. Hemisphere Dominance The non-dominant cerebral hemisphere
Carries on basic functions
Specializes in nonverbal functions
Motor tasks that require orientation of the body in space
Understanding and interpreting musical patterns
Nonverbal visual experiences
Control of emotions and intuitive thinking

34. Hemisphere Dominance
Nerve fibers of the corpus callosum connect the cerebral hemispheres
Allow the dominant hemisphere to control the motor cortex of the nondominant hemisphere
Transfer sensory information reaching the nondominant hemisphere to the dominant one
Information used in decision-making

35. Ventricles and CSF Ventricles
Interconnected cavities within cerebral hemispheres and brainstem
Continuous with central canal of spinal cord
Contain cerebrospinal fluid (CSF)
Four separate ventricles found in the brain
Left lateral ventricle
Right lateral ventricle
Third ventricle
Fourth ventricle

36. Choroid Plexuses and CSF
Project into the ventricles
Tiny, reddish, cauliflower-like masses of specialized capillaries from the pia mater
Secrete cerebrospinal fluid (CSF)
CSF
Found in all ventricles of brain
Enters subarachnoid space
Completely surrounds the brain and spinal cord which float in CSF
Supports and protects
Maintains stable ionic concentration
Provides a pathway to the blood for wastes

37. Diencephalon
Located between the cerebral hemispheres and above the midbrain
Composed largely of gray matter
2 main parts:
Thalamus
Dense mass that bulges into the third ventricle from each side
Hypothalamus
Masses of gray matter
Found inferior to the thalamus

38. Diencephalon Other parts include: Optic tracts and optic chiasma
Formed by optic fibers crossing over
Infundibulum
Conical process behind the optic chiasma
Posterior pituitary gland
Hands from the floor of the hypothalamus
Mammillary bodies
2 rounded structures behind the infundibulum
Pineal gland
Cone-shaped structure attached to upper diencephalon

39. Functions of Thalamus
Central relay station for sensory impulses ascending from other parts of the nervous system to the cerebral cortex
All regions of the cerebral cortex can communicate with the thalamus by means of descending fibers
Produces a general awareness of certain sensations such as
Pain
Touch
Temperature

40. Functions of Hypothalamus
Maintains homeostasis by regulating a variety of visceral activities
Links the nervous and endocrine systems
Regulates:
Heart rate and blood pressure
Body temperature
Water and electrolyte balance
Control of hunger and weight
Control of movement and secretions in digestive system
Stimulates the pituitary gland to secrete hormones
Sleep and wakefulness

41. Limbic System
Composed of portions of the cerebral cortex in frontal and temporal lobes connected to a number of deep masses of gray matter
Includes the hypothalamus, thalamus, and basal nuclei
Controls emotional experience and expression
Modifies the way a person acts by producing feeling of fear, anger, pleasure, and sorrow
Recognizes upsets that might threaten life by causing pleasant or unpleasant feelings about experiences.

42. Brainstem
Bundle of nervous tissue that connects the cerebrum to the spinal cord
Consists of numerous tracts of nerve fibers and several nuclei
Parts include:
Midbrain
Pons
Medulla oblongata

43. Midbrain
Short section of the brainstem between the diencephalo and the pons
Contains bundles of myelinated axons that join lower parts of the brainstem and spinal cord with higher parts of the brain
Two prominent bundles of axons on the underside are the corticospinal tracts
Main motor pathways between the cerebrum and lower parts of the nervous system
Serves as a center for visual and auditory reflexes

44. Pons Rounded bulge on underside of the brainstem
Separates the midbrain from the medulla oblongata
Relay impulses to and from the medulla oblongata and the cerebrum
Transmits impulses from cerebrum to centers in the cerebellum
Relay sensory impulses from peripheral nerves to higher brain centers
Functions with the medulla oblongata to maintain the basic rhythm of breathing

45. Medulla Oblongata
Extends from the pons to the foramen magnum of the skull
All ascending and descending nerve fibers pass through because of its location
The white matter surrounds a central mass of gray matter as in the spinal cord
Nuclei within control vital visceral activities:
Cardiac center
impulses originating here are transmitted to the heart on peripheral nerves
Alters heart rate

46. Medulla Oblongata (cont.)
Vasomotor center
Initiate impulses that travel to smooth muscles in walls of blood vessels and stimulate them to contract or relax
Vasoconstriction elevates blood pressure
Vasodilation depresses blood pressure
Respiratory center
Adjusts the rate and depth of breathing
Acts with the pons to maintain the basic rhythm of breathing

47. Reticular Formation Complex network of nerve fibers
Associated with tiny islands of gray matter
Scattered throughout the medulla oblongata, pons, and midbrain
Extends from the upper portion of the spinal cord into the diencephalon
Join with other parts of the brain in all major ascending and descending tracts
Activates the cerebral cortex into a state of wakefulness
Decreased activity results in sleep
If injured, results in coma

48. Cerebellum Large mass of tissue
Located below the occipital lobes of the cerebrum
Posterior to the medulla oblongata and pons
Consists of 2 lateral hemispheres
Partially separated by dura mater
Connected in the midline by the vermis
Composed primarily of white matter with a thin layer of gray matter called the cerebellar cortex
When cut medially, shows the arbor vitae (tree of life)

49. Cerebellum (cont.)
Communicates with other parts of the CNS by means of 3 pairs of nerve tracts called the cerebellar peduncles
Inferior peduncles bring sensory information about the position of the limbs, joints, and other body parts
Middle peduncles transmit signals from the cerebral cortex concerning the desired positions of the limbs, joints, and other body parts
Superior peduncles send correcting impulses to the midbrain
Incorporated into motor impulses that travel down the brain stem and spinal cord so that the body moves in the desired way

50. Cerebellum (cont.)
Acts as a reflex center for integrating sensory information concerning the position of body parts
Coordinates complex skeletal muscle movements
Helps maintain posture
Damage is likely to result in
Tremors,
Inaccurate movements of voluntary muscles
Loss of muscle tone
A reeling walk
Loss of equilibrium

51. Peripheral Nervous System
See page 243, Table 9.5
Consists of nerves that branch out from the CNS and connect it to other body parts
2 main divisions
Somatic Nervous system
Oversees conscious activities
Includes cranial and spinal nerve fibers that connect the CNS to the skin and skeletal muscles
Autonomic nervous system
Controls unconscious activities
Includes fibers that connect the CNS to viscera such as the heart, stomach, intestines, and glands

52. Cranial Nerves 12 pairs Arise from the underside of the brain
All originate from the brainstem except the first pair which comes from the cerebrum
Most are mixed nerves
Some associated with special senses have only sensory fibers
Some that affect muscles and glands have mainly motor fibers
Numbers or names designate cranial nerves
Indicate the order in which the nerves arise from the front to the back of the brain

53. Cranial Nerves See page 246, Table 9.6 Olfactory Nerves (I) Sensory
Sense of smell
Optic Nerves (II) Sensory
Sense of Vision
Oculomotor Nerves (III) Motor
Raise eyelids
Move the eyes
Adjust light entering eyes
Trochlear Nerves (IV) Motor
Move the eye

54. Cranial Nerves Trigeminal Nerves (V) Mixed Largest cranial nerves
3 divisions:
Opthalmic division Sensory
Eyes and upper face
Maxillary division Sensory
Upper teeth, gums, lip
Mandibular division Mixed
Lower teeth, gums, lip
Abducens Nerves (VI) Motor
Move the eye
Facial Nerves (VII) Mixed
Taste receptors of tongue
Muscles of facial expressions
Tear and salivary glands

55. Cranial Nerves Vestibulocochlear Nerves (VIII) Sensory 2 branches
Vestibular branch
Inner ear and balance
Cochlear branch
Hearing receptors
Glossopharyngeal Nerves (IX) Mixed
Tongue & pharynx (swallowing)
Vagus Nerves (X) Mixed
Muscles of larynx associated with speech and swallowing
Heart, smooth muscles and glands of chest and abdomen

56. Cranial Nerves Accessory Nerves (XI) Motor 2 branches Cranial branch
Muscles of soft palate, pharynx, and larynx
Spinal branch
Muscles of trapezius and sternocleidomastoid
Hypoglossal Nerves (XII) Motor
Move the tongue in speaking, chewing, and swallowing

57. Spinal Nerves 31 pairs Mixed nerves
Not named individually, but grouped
8 pairs cervical nerves (C1-C8)
12 pairs thoracic nerves (T1-T12)
5 pairs lumbar nerves (L1-L5)
5 pairs sacral nerves (S1-S5)
1 pair coccygeal nerves (Co)
Adult spinal cord ends between L1 and L2
Lumbar, sacral, and coccygeal nerve fibers extend beyond the end of the spinal cord
Fibers form the cauda equina (horse’s tail)

58. Spinal Nerves

59. Spinal Nerves
Each spinal nerve emerges from the cord by two short branches or roots which lie in the vertebral column
Dorsal root
Posterior or sensory root
Dorsal root ganglion (cell bodies)
Axons conduct impulses inward from peripheral body parts
Ventral root
Anterior or motor root
Axons from motor neurons
Cell bodies are within gray matter of the spinal cord

60. Spinal Nerves

61. Spinal Nerves Ventral and dorsal roots combine to form a spinal nerve
Extends outward from vertebral canal through an intervertebral foramen
Beyond the foramen, the spinal nerve divides into several parts
Except in thoracic region
Main portions of spinal nerves combine to form complex networks called plexuses
In a plexus, spinal nerves are sorted and recombined so that fibers that innervate a specific body part reach it in the same nerve

62. Spinal Plexuses Cervical plexus Supply muscles and skin of neck
Conduct motor impulses to muscles of diaphragm
Brachial plexus
Supply the muscles and skin of arm, forearm, and hand
Lumbosacral plexus
Supply the muscles and skin of the lower abdominal wall, external genitalia, buttocks, thighs, legs, and feet
Thoracic spinal nerves do not enter a plexus
Supply motor impulses to the intercostal muscles and upper abdominal wall muscles
Receive sensory impulses from the skin of the thorax and abdomen

63. Spinal Plexuses

64. Autonomic Nervous System
Portion of the PNS that functions independently and continually without conscious effort
Controls visceral functions by regulating the actions of
Smooth muscles
Cardiac muscles
Glands
Regulates
Heart rate
Blood pressure
Breathing rate
Body temperature
Other visceral activities

65. Autonomic Nervous System
2 divisions of ANS
Sympathetic
Prepares body for energy-expending, stressful, or emergency situations
“Fight or flight” response
During an emergency, increases the heart and breathing rates
Parasympathetic
Most active under ordinary, restful conditions
Counterbalances the effects of the sympathetic division
Restores the body to a resting state following a stressful experience
Following an emergency, decreases the activities of the heart and lungs

66. Sympathetic vs. Parasympathetic