1. Anatomy and Physiology The Central Nervous System
Marieb’s Human
Anatomy and Physiology
Ninth Edition
Marieb w Hoehn
Chapter 12
The Central Nervous System
Lecture 19
94 min, 51 slides

2. Lecture Overview The brain The spinal cord Overview Protection
Meninges
Ventricles and the CSF
The structure of the major parts of the brain
Functional areas of the brain
The spinal cord
Spinal meninges, and spinal reflexes
Ascending and descending spinal tracts

3. Divisions of the Nervous System
You are here
CNS
PNS

4. Brain – Embryology & Overview
Table & Figure From: Marieb & Hoehn, Human Anatomy & Physiology, 9th ed., Pearson, 2013

5. Overview of the Brain Functions Major Parts
regulates visceral activities
coordinates muscular movements
interprets sensations
determines perception
stores memory
carries out reasoning
makes decisions
determines personality
Major Parts
cerebrum (two hemispheres)
diencephalon
thalamus
hypothalamus
brain stem
midbrain (mesencephalon)
pons
medulla oblongata
cerebellum

6. Protection of the Brain
The brain is protected
Mechanically by
The skull bones
The meninges
The cerebrospinal (CSF) fluid
Biochemically by the blood-brain barrier
Capillaries interconnected by tight junctions
Astrocytes/ependymal cells control permeability of general capillaries/choroid capillaries
May be obstacle to delivery of drugs
May become more permeable during stress
Two points of entry to brain: general capillaries and capillaries of the choroid plexuses.

7. Meninges of the Brain *Singular of meninges is meninx
Dura mater – thick, collagenous membrane (about thickness of rubber kitchen glove)
Arachnoid mater – simple squamous epithelium; loose meshwork of collagenous and elastic fibers spanning the gap (subarachnoid space)
Pia mater – delicate membrane, close follows contours of nervous tissue that it covers.
- dura mater – outer, tough (anchoring dural folds)
- arachnoid mater – web-like
- pia mater – inner, delicate
*Singular of meninges is meninx
- Subdural space – like interstitial fluid
- Subarachnoid space – CSF
Figure From: Marieb & Hoehn, Human Anatomy & Physiology, 9th ed., Pearson, 2013

8. Dural Folds
Figure From: Marieb & Hoehn, Human Anatomy & Physiology, 9th ed., Pearson, 2013
Falx Cerebri – within longitudinal fissure; separates cerebral hemispheres
Tentorium Cerebelli – above cerebellum; separates occipital lobe from cerebellum

9. Ventricles of the Brain
interconnected cavities
within cerebral hemispheres and brain stem
continuous with central canal of spinal cord
filled with cerebrospinal fluid (CSF)
lateral ventricles (1, 2)
third ventricle (3)
fourth ventricle (4)
cerebral aqueduct

10. Cerebrospinal Fluid
secreted by choroid plexus of ventricles (~500 ml/day)
circulates in ventricles, central canal of spinal cord, and subarachnoid space
completely surrounds brain and spinal cord
clear liquid (more Na+ and Cl-, but less K+, Ca2+, glucose, and protein than plasma)
nutritive and protective
helps maintain stable ion concentrations in CNS
About 500 ml of CSF produced per day; about ml present at any time.

11. Flow of CSF Know (Luscka) (Magendie) (Monro)
Figure From: Marieb & Hoehn, Human Anatomy & Physiology, 9th ed., Pearson, 2013

12. Overview of the Cerebrum of the Brain
Figure From: Marieb & Hoehn, Human Anatomy & Physiology, 9th ed., Pearson, 2013
Over 85% of brain mass, with about 14 billion multipolar neurons in cortex
Lobes named for overlying bones. (See sulci above for divisions)

13. Functions of Cerebrum interpretation initiating voluntary movements
storing memory
retrieving memory
reasoning
center for intelligence and personality
The cerebrum can be divided into several functional areas:
- Motor (frontal cortex) - Sensory (parietal, occipital, and temporal cortex) - Association (all lobes)
Points to keep in mind: - Each cerebral hemisphere receives information from, and sends information to, the opposite side of the body - Although symmetrical, the cerebral hemispheres are not entirely equal in function

14. Brain – Sensory and Motor Areas* 4 6 1 5 8 7 2 3 9 40
(Gnostic) 44 39 22 10 42 18 43 41 19 17
Figure From: Marieb & Hoehn, Human Anatomy & Physiology, 9th ed., Pearson, 2013
*Somatosensory = Somesthetic

15. Cerebral Cortex Motor/Sensory Homunculi
Notice the relative amount of cortical tissue devoted to each sensory function.

16. Hemispheric (Cerebral) Lateralization
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001
Categorical hemisphere
Representational hemisphere

17. Basal Nuclei (formerly basal ganglia)
nuclei are masses of gray matter in CNS
deep within cerebral hemispheres
three nuclei: caudate nucleus and putamen, (together called the striatum), and the globus pallidus
subconscious control certain muscular activities, e.g., learned movement patterns
Receive input from cerebral cortex, other subcortical nuclei, and each other. Output is through thalamus and (along with output from substantia nigra of midbrain) goes to the premotor and prefrontal cortex to influence muscle movement directed by primary motor cortex. Also seem to filter out incorrect or inappropriate responses of cognition and emotion.
Receive input from entire cerebral cortex.
Relay motor impulses originating in the substantia nigra (where is this?), along with their own output, through the thalamus to the motor cortex to influence muscle movement.

18. Brain – Cerebral White Matter
Three types of myelinated tracts form cerebral white matter:
1. Association – same hemisphere
2. Commisural – between corresponding gyri in opposite hemispheres
3. Projection – Ascending and descending tracts
Figure From: Marieb & Hoehn, Human Anatomy & Physiology, 9th ed., Pearson, 2013

19. Basal Nuclei nuclei are masses of gray matter in CNS
deep within cerebral hemispheres
caudate nucleus, putamen, globus pallidus (together called the corpus striatum)
subconscious control certain muscular activities, e.g., learned movement patterns
Relay motor impulses originating in the cerebral cortex and substantia nigra of the midbrain.

20. Limbic System The motivational system Consists of
portions of frontal lobe
portions of temporal lobe
hypothalamus
thalamus
basal nuclei
other deep nuclei
associated with sense of smell (less significant)
Functions
controls emotions
produces feelings
interprets sensory impulses
facilitates memory storage and retrieval (learning!)
Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007
The motivational system

21. Memory
A “Memory” is the persistence of knowledge that can be accessed (we hope!) at a later time.
Memories are not stored in individual “memory cells” or neurons; they are stored as pathways called engrams, or memory traces that use strengthened or altered synapses.
Immediate memory lasts a few seconds, e.g., remembering the earliest part of a sentence to make sense of it.
Short-term memory (STM) lasts a few seconds to a few hours
Working memory is a form of this (repeating a phone number over to yourself just long enough to dial it – and then forget it!)
Limited to a few ‘bits’ of information (about 7-9). So, ‘chunk up’!
Long-term memory (LTM) can last a lifetime
Can hold much more information that STM
Declarative (events and facts)
Procedural (motor skills)

22. Diencephalon between cerebral hemispheres and brainstem
surrounds third ventricle
thalamus
hypothalamus
epithalamus
optic tracts
optic chiasm
infundibulum
posterior pituitary
mammillary bodies
pineal gland
(Tectum)

23. Diencephalon - Thalamus
Ventral nuclei
- Posterior; relay for taste
- Anterior and Lateral; voluntary motor
Forms wall of third ventricle
Crude interpretation center for pain, touch, pressure, temperature
Figure From: Marieb & Hoehn, Human Anatomy & Physiology, 9th ed., Pearson, 2013
Relay for hearing
Relay for vision
The ‘gateway’ to the cerebral cortex. Major relay for sensory information coming into the cerebral cortex, roles in cortical arousal, learning, and memory

24. Diencephalon - Hypothalamus
Hypothalamus - maintains homeostasis by regulating visceral activities (see list below for examples…)
Heart rate and blood pressure - Body temperature
Stimulation of the pituitary (links nervous and endocrine) - Water balance (ADH)
SM contraction (OT) - Feeding/satiety centers - Movement/secretions of glands and intestines - Sleep and wakefulness
Rage/aggression
Psychosomatic illness
Figure From: Marieb & Hoehn, Human Anatomy & Physiology, 9th ed., Pearson, 2013

25. Brain Stem
Three Parts
Midbrain
Pons
Medulla Oblongata
(Tectum)

26. Brain Stem
Three Parts
Midbrain
Pons
Medulla Oblongata
(Tectum)

27. Midbrain
between diencephalon and pons
contains bundles of fibers that join lower parts of brainstem and spinal cord with higher part of brain
cerebral aqueduct
cerebral peduncles – bundles of nerve fibers
contains red nucleus (rubro-) and substantia nigra
corpora quadrigemina – centers for visual and auditory reflexes
Major connecting center between spinal cord and brain and parts of brainstem
(Tectum)
Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007
Origins of: CN III, IV

28. Pons Origins of CN V, VI, VII, VIII
rounded bulge on underside of brainstem
between medulla oblongata and midbrain
helps regulate rate and depth of breathing
relays nerve impulses to and from
medulla oblongata and brainstem via longitudinal tracts
cerebellum via transverse tracts
Origins of CN V, VI, VII, VIII

29. Medulla Oblongata
enlarged continuation of spinal cord running through foramen magnum of skull
conducts all ascending (olive) and descending (pyramids - decussation) impulses between brain and spinal cord
contains cardiac, vasomotor, and respiratory control centers
nucleus gracilis and nucleus cunneatus on dorsal side; sensory info, cross over, then send to thalamus
Origins (nuclei) of: CN IX, X, XI, and XII

30. Reticular Formation
complex network of nerve fibers scattered throughout the brain stem
extends into the diencephalon
connects to centers of hypothalamus, basal nuclei, cerebellum, and cerebrum
filters incoming sensory information; habituation
modulates pain
arouses cerebral cortex into state of wakefulness
Ascending portion is called the ‘reticular activating system’ (prefix = reticulo-)

31. Cerebellum
integrates sensory information concerning position of body parts
coordinates skeletal muscle activity
helps to maintain posture
May also be involved in several sensory, linguistic, emotional and non-motor functions
virtually all fibers entering and leaving are ispsilateral
Cerebellum controls ipsilateral muscles (on the
Cerebellum is connected to the brainstem by three pairs of peduncles:
Superior peduncles connect to midbrain (output to midbrain and thalamus)
Middle peduncles connect to pons (input from cerebrum about muscle movements and hearing/equilibrium from inner ear)
Inferior peduncles connect to medulla (input from spinocerebellar tracts with proprioceptive information)
Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007

32. Functions of Parts of Brain
Part of Brain
Major Function
Motor areas
Primary motor cortex (Precentral gyrus)
Voluntary control of skeletal muscles
Broca’s area (motor speech area)
Controls muscles needed for speech
Frontal eye field
Controls muscles needed for eye movement
Sensory areas
Cutaneous Sensory Area (postcentral gyrus)
Receives somatic sensations
Visual area (occipital lobe)
Receives visual sensations
Auditory area (temporal lobe)
Receives auditory sensations
Association areas (all lobes)
Analyze and interpret sensory experiences; coordinate motor responses
memory, reasoning, verbalization, judgment, emotions
Basal nuclei
Subconscious control certain muscular activities, e.g., learned movement patterns (a nucleus is a collection of neuron cell bodies in the CNS); putamen, globus pallidus, caudate
Limbic system
controls emotions , produces feelings, interprets sensory impulses, facilitates memory storage and retrieval (learning!)
Diencephalon
Thalamus
gateway for sensory impulses heading to cerebral cortex, receives all sensory impulses (except smell)
Hypothalamus
Vital functions associated with homeostasis
Brainstem
Midbrain
Major connecting center between spinal cord and brain and parts of brainstem; contains corpora quadrigemina (visual and auditory reflexes)
Pons
Helps regulate rate and depth of breathing, relays nerve impulses to and from medulla oblongata and cerebellum
Medulla Oblongata
Contains cardiac, vasomotor, and respiratory control centers, contains various nonvital reflex control centers (coughing, sneezing, vomiting)
Reticular formation (system)
Filters incoming sensory information; habituation , modulates pain, arouses cerebral cortex into state of wakefulness (reticular activating system)
Cerebellum
Subconscious coordination of skeletal muscle activity, maintains posture

33. Review of Major Brain Areas12 1 2 3 11 4 5 6
10 (White part) 7 8 9

34. Summary from Last Lecture
Part of Brain
Major Function
Brainstem
Medulla Oblongata
(Embryology?)
(Ventricles nearby?)
Contains cardiac, vasomotor, and respiratory control centers
Nucleus gracilis/cunneatus
Origin of CN 9, 10, 11, 12
Pons
Bridge between medulla and midbrain via transverse tracts (to cerebellum) and longitudinal tracts(to medulla/midbrain)
Helps regulate rate and depth of breathing
Origin of CN 5, 6, 7, 8
Midbrain
Major connecting center between spinal cord and brain and parts of brainstem
Contains corpora quadrigemina (visual and auditory reflexes)
Origin of CN 3 and 4
Location of red nucleus (rubrospinal tract)
Origin of substantia nigra
Cerebellum
Subconscious coordination of skeletal muscle activity, maintains posture
Hemispheres separated by falx cerebelli and vermis
Cerebellar peduncles (sup, middle, inf) attach to rest of brainstem
Diencephalon (Embryology?)
Thalamus
Gateway (relay) for sensory impulses heading to cerebral cortex; hearing, vision, taste
Crude interpretation for pain, touch, pressure, and temperature
relay for motor information (voluntary)
Forms walls of third ventricle
Hypothalamus
Vital functions associated with homeostasis, ANS, psychosomatic illness, feeding/satiety
Connected to pituitary by infundibulum (pituitary stalk)

35. Spinal Cord Structure
extends from the foramen magnum to 2nd lumbar vertebra
cervical and lumbar enlargements
cauda equina (horse’s tail) – thin nerve fibers that exit at different level than they arise (note that spinal cord does not extend into this area of the lumbar spine). Begins around L2 and extends to S5. Good area for lumbar puncture and collection of CSF.
Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007
Spinal cord extends entire length of vertebral column early in fetal development, to L3 at birth, and to L1 in an adult. Thus, it occupies only the upper two thirds of the vertebral column in an adult. The lower third of the vertebral column is occupied by the cauda equina.

36. Meninges of the Spinal Cord
Figures from: Saladin, Anatomy & Physiology, McGraw Hill, 2007
Space between the dura mater and the vertebral body is called the epidural space

37. Cross Section of Spinal Cord
The spinal cord…
is a center for spinal reflexes
aids in locomotion
is a conduit for nerve impulses to and from the brain

38. Organization of Spinal Gray Matter
You should know the major areas of gray matter of within the spinal cord:
Posterior = sensory
Lateral = visceral motor
Anterior = somatic motor
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

39. Organization of Spinal White Matter
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

40. Tracts of the Spinal Cord
Ascending tracts conduct sensory impulses to the brain
Descending tracts conduct motor impulses from the brain to motor neurons reaching muscles and glands
All the axons in a tract share a common origin and destination
Tracts are usually named for their place of origin (1st) and termination (2nd)
Most axons cross over during their travel. What will this mean clinically?

41. Ascending Tracts
fasciculus cuneatus/gracilis - fine touch, pressure, body movement - cross (decussate) in medulla
spinothalamic - crude pain, temperature, pressure, and touch - cross in spinal cord
spinocerebellar - subconscious coordination of muscle movements (1st and 2nd order neurons) - ipsilateral 3 2 1
Decussation
(crossing over)

42. 1st, 2nd, and 3rd Order Sensory Neurons
1st order neuron – from receptor to the spinal cord (cell bodies are located in the dorsal root ganglion)
2nd order neuron – from spinal cord to thalamus
3rd order neuron – from thalamus to sensory cerebral cortex - terminate in the cerebral cortex 3 2 1
Decussation

43. Descending Tracts
corticospinal (direct, pyramidal) - voluntary movement of skeletal muscles - lateral cross in medulla - contralateral
reticulospinal (indirect, extrapyramidal) subconscious muscle tone, sweat glands some lateral cross, anterior do not cross
rubrospinal (indirect, extrapyramidal) subconscious regulation of upper limb tone/movement cross in brain (less important in humans)
Upper motor – begin in precentral gyrus of cortex
Decussation
Lower
Upper MN – Cerebral cortex to spinal cord
Lower MN – Spinal cord to effector

44. Review The brain is protected by the
Skull bones
Meninges
CSF
Blood-brain barrier
The meninges of the brain and spinal cord consist of the
Dura mater
Arachnoid (membrane)
Pia mater

45. Review Important motor areas of cerebral cortex
Precentral gyrus (Primary motor area)
Broca’s area
Frontal eye field
Important sensory areas of cerebral cortex
Postcentral gyrus (Primary cutaneous sensory)
Visual area (occipital lobe)
Auditory area (temporal lobe)
The spinal cord is a
Center for spinal reflexes
Conduit for nerve impulses to and from the brain

46. Review

47. Review Spinal cord contains nerve tracts Ascending = sensory
Descending = motor
95 min, 47 slides