
Brain

Spinal cord

Nerves

Sensory receptors


Sensory input – sight, taste, touch, blood pH or blood pressure

Integration – sensory input can cause immediate response, be stored as memory, or be ignored

Homeostasis – internal balance

Mental activity – consciousness, thoughts

Control of muscles & glands


Central Nervous System (CNS)

Consists of the brain and spinal cord

Peripheral Nervous System (PNS)

External to CNS

Consists of sensory receptors, nerves, ganglia, and plexuses

12 pairs of cranial nerves (from brain)

31 pairs of spinal nerves (from spinal cord)


Afferent divison – Sensory

Transmits action potentials (APs) from sensory receptors to CNS

Efferent division – Motor

Transmits APs from CNS to the effector organs – muscles and glands

Subdivided into

Somatic Nervous System

Autonomic Nervous System (ANS)


Somatic transmits APs from the CNS to skeletal muscles

These muscles are voluntarily controlled through the somatic nervous sys.


Involuntarily controlled

2 subdivisions


Sympathetic division

Most active during physical activity

Parasympathetic division

Regulates resting or vegetative functions

Digesting food or emptying bladder

Enteric nervous system – consists of plexuses in wall of digestive tract – acts independently of CNS


Neurons – receive stimuli and conduct action potentials

Nonneural cells

Neuroglia / Glial cells: support and protect neurons and perform many other functions

Account for over ½ the brain’s weight

Can be 10-50x more neuroglial cells than neurons in certain parts of brain


Astrocytes – star-shaped with cytoplasmic processes that extend from cell body

Form a supporting framework for blood vessels and neurons

Assist in formation of blood-brain barrier

Figure 11.6, page 379


Ependymal – line the ventricles of brain and central canal of spinal cord

Choroid plexuses secrete cerebrospinal fluid

Move fluid through cavities of brain

Figure 11.7, page 379


Microglia – specialized macrophages in the CNS

Become mobile and phagocytic in response to inflammation

Phagocytize necrotic (dead/dying) tissue, microorganisms, and foreign substances that invade CNS

Figure 11.8, page 379


Oligodendrocytes – have cytoplasmic extensions that can surround axons

If extensions wrap many times, they form the myelin sheaths.

Single cell can form myelin sheaths around portions of several axons

Figure 11.9, p. 380


Schwann cells - neurolemmocytes

Neuroglial cells in the PNS that wrap around axons, many times around will form a myelin sheath

Can only form around a portion of one axon

Satellite cells – surround neuron cell bodies in ganglia

Provide support, and can provide nutrients to the neuron cell bodies

Figure 11.10 – 11.11, page 380


Myelinated Axons - Fig 11.12a

Extensions from oligodendrocytes or
Schwann cells wrap around segments of an axon to form a phospholipid-rich membranes, these areas are called
“internodes”

Nodes of Ranvier – interruptions in the myelin sheath

White Matter


Unmyelinated Axons – Fig 11.12b

These axons rest in invaginations of the oligodendrocytes & Schwann cells

The cell membranes surround each axon, but do not wrap around it many times like a myelin sheathed axon

Each axon can be surrounded by a series of cells

Each cell can surround more than one unmyelinated axon

Gray Matter


Spinal cord - the major comm. link between the brain and all parts of the
PNS inferior to the head

Integrates incoming info and produces responses through reflex mechanisms

Extends from the foramen magnum to the level of the 2 nd lumbar vertebrae

Has cervical, thoracic, lumbar, and sacral segments

Segments named for where nerves enter & exit


31 pairs that exit vertebral column through intervertebral and sacral foramina – Fig 12.1, p. 412

Nerves in lower segments have to descend further down vertebral canal b/c cord is shorter than vert. Column

Spinal cord is not uniform in diameter

Larger at superior end & gradually ↓
 Cervical enlargement
 Lumbosacral enlargement


Meninges: connective tissue membranes that surround the brain & spinal cord (Figure 12.2, p. 413)

Consist of three layers

Dura Mater – most superficial, thickest layer

Forms the thecal sac that surrounds spinal cord

Arachnoid Mater – thin, wispy layer that looks like cobwebs

Pia Mater – deepest layer, bound very tightly to spinal cord


Reflex Arc: the basic functional unit of the nervous system


The smallest, simplest portion capable of receiving a stimulus and producing a response
5 basic components (Fig 12.5, p. 416)





A sensory receptor
A sensory neuron
An interneuron
A motor neuron
An effector organ

Reflex: an automatic response to a stimulus produced by a reflex arc.


Stretch Reflex: simplest in which muscles contract in response to a stretching force applied to them

Example: Patellar (knee-jerk) reflex

Golgi Tendon Reflex: prevents contracting muscles from applying excessive tension to tendons

Withdrawal (Flexor) Reflex: removes a limb or other body part away from a painful stimulus


Reciprocal Innervation – flexor - extensor
Crossed Extensor Reflex – retract - extend


Consist of axons, Schwann cells, and connective tissue – Fig 12.12, p. 421

Each nerve fiber and its Schwann cell sheath is surrounded by delicate layer known as endoneurium

The perineurium surrounds groups of axons to form to form nerve fasicles

3 rd layer is the epineurium which binds the nerve fascilces together to form a nerve – the conn. tissue is continuous with dura mater surrounding the CNS.


Cervical, Thoracic, Lumbar, and Sacral nerves have specific locations & functions – Fig 12.13a, 12.13b – p. 422

Named by a letter (associated with which region it is in) and a # which tells us the location of the nerve within each region.

C 1- C8

T 1- T12

L 1- L5

S1 – S5

Co 1

Figure 12-14, Dermatomal Map, p. 423


Brain – consists of the brainstem, cerebellum, diencephalon, and the cerebrum (table 13.1, p. 444)

Brainstem – consists of the medulla oblongata, pons, midbrain, and reticular formation

12 pairs of cranial nerves that belong to the PNS








Organized
Like math & reading
Logical
Don’t enjoy clowning around
Skilled at sequencing ideas
Like verbal lectures over textbooks
Needs quiet to study
LEFT

Good at art

Creative

Prefers working in groups

Dreamers

Can memorize music

Good at geometry

Prefers to summarize vs outline
RIGHT

I.
II.
III.
IV.
V.
VI.
Olfactory
Optic
Oculomotor
Trochlear
Trigeminal
Abducent
VII.
Facial
VIII.
Vestibulocochlear
IX.
X.
XI.
XII.
Glossopharyngeal
Vagus
Accessory
Hypoglossal


The following reflexes in the brainstem involve the cranial nerves:

Turning your eyes to a flash of light, sudden noise, or touch on the skin

Moving your eyes to track a moving object

Keep your teeth from biting too hard on hard objects

Move tongue out of way to keep from biting it while chewing food