1. Nervous System Anatomy
Chapter 11

2. Meninges
Meninges are membranes that cover and protect the brain and spinal cord
There are three types of meninges:
dura mater
arachnoid mater
pia mater
 Cerebrospinal fluid occupies the space between the arachnoid and pia maters. This space is known as the subarachnoid space.

3. Spinal Cord
The spinal cord is a nerve column that extends from the brain into the vertebral canal. It terminates at the level between the first and second lumbar vertebrae.
The spinal cord is composed of 31 segments, each that have a pair of spinal nerves branching off from it.
A CERVICAL enlargement occurs at the top of the spinal cord and a LUMBAR enlargement occurs at the bottom of the spinal cord.

4. Spinal Cord, cont.
Two deep grooves divide the spinal cord into right and left halves. These grooves are known as: posterior median sulcus and anterior median fissure.
The spinal cord has a central core made of GRAY matter, which is in turn, surrounded by WHITE matter.
The function of the spinal cord is to provide a two-way communication system between the brain and structures outside the nervous system.
This is achieved by ascending and descending tracts. An ascending tract carries SENSORY impulses to the brain; while descending tracts carry MOTOR impulses to muscles and glands.

5. Reflex Arcs
A reflex arc is the behavioral unit of the nervous system and usually contains a sensory neuron, a reflex center composed of interneurons, and a motor neuron.
REFLEXES are automatic, subconscious responses to change and they help maintain homeostasis.
 Withdrawal reflexes are protective actions that usually occur when a person unexpectedly touches something painful.

6. Brain
The brain is the largest and most complex part of the nervous system
It contains nerve centers that are associated with sensations
It issues motor commands and carries on higher mental functions

7. Brain Development
The brain develops from a neural tube with three cavities—the FOREBRAIN, the MIDBRAIN, and the HINDBRAIN
The cavities are known as ventricles and the walls give rise to structural and functional regions
Ventricles are filled with cerebrospinal fluid
CHOROID PLEXUSES in the walls of the ventricles secrete cerebrospinal fluid. The fluid’s composition is regulated by ependymal neuroglial cells
Cerebrospinal fluid circulates through the ventricles and is REABSORBED into the blood of the dural sinuses

8. Parts of the Brain 1. Cerebrum:
The cerebrum consists of two cerebral hemispheres connected by the CORPUS CALLOSUM
SULCI divide each hemisphere into LOBES
The cerebral cortex is a thin layer of gray matter (2-5mm) that makes up the outermost portion of the cerebrum. Nearly 75% of all neural cell bodies are found in the cerebral cortex
The lobes that make up the cerebrum are:
a. FRONTAL LOBE
b. PARIETAL LOBE
c. TEMPORAL LOBE
d. OCCIPITAL LOBE
e. INSULA

9. Functions of Cerebrum
The cerebrum is concerned with higher brain functions, such as thought, reasoning, interpretation of sensory impulses, control of voluntary muscles, and memory storage
The cerebral cortex has sensory, motor, and association areas.
Primary motor regions lie in the frontal lobes
Primary sensory regions lie in the parietal lobes, though some specialized sensory are found in the temporal and occipital lobes, as well
Association areas analyze and interpret sensory impulses and provide memory, reasoning, verbalizing, judgment, and emotions
One cerebral hemisphere usually dominates for certain intellectual functions.
Short-term memory is thought to be electrical.
Long-term memory is thought to be encoded in patterns of synaptic connection.

10. Functions of the Cerebral Lobes
Frontal Lobe:
controls voluntary movement
Higher intellectual processes like problem solving and judging behavior
Parietal Lobe:
Sensation center for touch, pain, pressure, and temperature
Understanding speech and using words to express thought and feeling
Temporal Lobe:
Sensation center for hearing
Interpret senses and remember visual scenes, music, and patterns
Occipital Lobe:
Sensation center for vision
Combine visual images with sensory experience
Insula:
Integrate autonomic information

11. Parts of the Brain, cont. 2. Diencephalon
The diencephalon contains the THALAMUS and the HYPOTHALAMUS
The thalamus selects incoming sensory impulses and relays them to the cerebral cortex
The hypothalamus is important in maintaining homeostasis
The limbic system produces emotional feelings and modifies behavior

12. Limbic System
The limbic system is the center of emotions, of pain and pleasure
The limbic system is a loose term for a collection of parts found in the diencephalon:
Hypothalamus: already defined
Hippocampus: associated with MEMORY
Working memory: short term memory (like RAM in a computer)
Declarative memory: long term memory (like hard drive on a computer)
Procedural memory: habits, actions, and skills learned by repetition
Amygdala: associated with FEAR and ANGER
Flight or fight reflex
Arousal
Hormonal secretions

13. PARTS OF THE Brain, cont. 3. Brain Stem
The brain stem extends from the base of the brain to the spinal cord and consists of the MIDBRAIN, PONS, and MEDULLA OBLONGATA
The MIDBRAIN contains reflex centers associated with eye and head movements
The PONS transmits impulses between the cerebrum and other parts of the nervous system and contains centers that help regulate rate and depth of breathing
The MEDULLA OBLONGATA transmits all ascending and descending impulses and contains several vital and non-vital reflex centers.

14. Parts of the Brain, cont. 4. Cerebellum
The cerebellum consists of two hemispheres connected by the VERMIS
A thin cortex of gray matter surrounds the white matter of the cerebellum
The cerebellum functions primarily as a reflex center, coordinating skeletal muscle movements and maintaining equilibrium.

15. Parts of the Brain, cont. 5. Basal Ganglia
Basal ganglia are masses of gray matter located deep within the cerebral hemispheres.
They relay motor impulses originating in the cerebral cortex, and aid in controlling motor activities.

16. Peripheral Nervous System
The peripheral nervous system consists of cranial and spinal nerves that branch out from the brain and spinal cord to ALL BODY PARTS
It can be subdivided into SOMATIC and AUTONOMIC portions

17. Nerve Fiber Classification
Nerves can be classified as:
SENSORY NERVES—conduct impulses into the brain or spinal cord
MOTOR NERVES—carry impulses to muscles or glands
MIXED NERVES—include both sensory and motor fibers

18. Somatic--Cranial Nerves
TWELVE PAIRS of cranial nerves connect the brain to parts in the head, neck, and trunk
Most cranial nerves are mixed, but some are pure sensory or motor nerves
The names of the cranial nerves indicate their primary functions or the general distributions of their fibers
EX: Olfactory nerves deal with the sense of smell and contain only sensory neurons.
Optic nerves deal with vision.

19. Somatic--Spinal Nerves
THIRTY-ONE pairs of spinal nerves originate from the spinal cord
These mixed nerves provide a two-way communication system between the spinal cord and the upper limbs, lower limbs, neck, and trunk
 Spinal nerves are grouped according the levels from which they arise, and they are numbered sequentially:
CERVICAL NERVES (C1-C8)
THORACIC NERVES (T1-T12)
LUMBAR NERVES (L1-L5)
SACRAL NERVES (S1-S5)
COCCYGEAL NERVES (Co)

20. Autonomic PNS
The autonomic nervous system functions without conscious effort
 It is concerned primarily with regulating visceral activities that maintain homeostasis

21. General Characteristics
Autonomic functions are reflexes controlled from centers in the hypothalamus, brain stem, and spinal cord
Autonomic nerve fibers are associated with ganglia where impulses are integrated before distributions to effectors
The integrative function of the ganglia provides a degree of independence from the CNS
The autonomic nervous system is subdivided into two divisions—sympathetic and parasympathetic
The sympathetic division prepares the body for stressful and emergency conditions
 The parasympathetic division is most active under ordinary conditions and counterbalances the effects of the sympathetic division after a stressful state.

22. Sympathetic Nervous System Parasympathetic Nervous System