I. Nerve Tissue

A. Neurons--nerve cells

1. cell body

a. cytoplasm--mitochondria, lysosomes, golgi apparatus, and a network of meurofibrils

b. cell membrane

c. nucleus--has a nucleolus, but does not undergo mitosis

2. nerve fibers

a. dendrites--short and highly branched; receive the impulse and move it toward the cell body

b. axon--conducts nerve impulses away from the cell body

1. Schwann cells--sheaths found around the axon

2. cell membrane (neurilemma)--can have a lipid-protein substance called myelin (white in color) or without myelin (unmyelinated appear gray)

B. Neuroglial cells

1. location--brain and spinal cord where they are several times more numerous than neurons

2. functions--fill spaces, support neurons, act as phagocytes, and generally hold the brain and spinal cord together

3. reproduction--they can and are sometimes responsible for tumors in the brain or spinal cord

4. types

a. astrocytes--found between nerve tissues and blood vessels where they seem to function in providing structural support and in removing cellular debris

b. oligodendrocytes--cells arranged in rows along nerve fibers; function in the formation of myelin within the brain and spinal cord

c. microglia--scattered throughout the central nervous system; support neurons and carries on phagocytosis

d. ependyma--form an epithelial-like membrane that covers specialized parts within the brain

Name the major parts of a neuron and give their function.

Label the diagram.

How are neurons and neuroglial cells different?

Which one would be capable of causing tumors in the brain? How do you know this?

Name the various types of neuroglial cells.

II. The Nerve Impulse

A. Cell Membrane

1. polarized--a result of an unequal distribution of ions (charged particles)

2. Nerve cell at rest

a. high concentration of sodium ions on the OUTSIDE of the membrane and a high concentration of potassium ions on the INSIDE

b. large numbers of negatively charged ions on the inside of the cell

c. the outside develops a positive charge with respect to the inside

B. Action Potential

1. If the membrane is disturbed, a nerve impulse its triggered

2. stimulus can include temperature, pressure, chemical concentration, electrical

3. involved--the movement of sodium and potassium ions through the membranes

C. All-or-None Response

D. Synapse

1. transmission--from a dendrite to a cell body along the axon to a synapse and then to the dendrite of the next neuron

2. synaptic knob--found at the end of an axon; secretes neurotransimitters

3. neurotransmitter--chemical released from an axon that starts or stops a nerve impulse

a. excitatory--neurotransmitters that trigger a nerve impulse

b. inhibitory--neurotransmitters that inhibit (stop) a nerve impulse

III. Organization of the Nervous System

A. Central Nervous System

1. brain

2. spinal cord

B. Peripheral Nervous System

1. nerves

a. sensory (afferent)--carry nerve impulse from the body to the brain or spinal cord

b. interneurons (association)--lie in the brain or spinal cord

c. motor (efferent)--go from the brain or spinal cord to the muscle or gland

(1) somatic--under conscious control

(2) automonic--cannot be consciously controlled

2. ganglia--group of nerve cells bunched together

3. receptor--area of the body that is stimulated / senses

4. effector--muscle or gland

Name the divisions of the CNS.

Name the three types of nerves.

Give a characteristic of each.

IV. Reflexes

A. Nerve Pathway--route followed by a nerve impulse

1. reflex arc

a. definition--simplest nerve pathway; does not go to the brain

b. examples--heart rate; blood pressure, and digestive activities; swallowing, sneezing, coughing and vomiting

c. knee-jerk reflex--sensory neuron (of the knee) to the spinal cord to the motor neuron and back to the knee

d. withdrawal reflex--touch something hot or sharp; sensory neuron to the spinal cord and back to the finger to withdraw; a second sensory impulse goes to the brain and the person becomes aware of the experience

What are the steps of a reflex? Be sure to use sensory, motor, receptor, effector, synapse, spinal cord.

V. Coverings of the Central Nervous system

A. Meninges--membranes that cover the brain and spinal cord

1. layers

a. dura mater--outer most; composed of tough, white fibrous connective tissue

b. arachnoid mater--middle layer

c. pia mater--inner layer; contains many blood vessels that aid in nourishing the brain and spinal cord

2. cerebrospinal fluid--liquid found between the arachnoid and pia mater

Name the three layers of the meninges.

What is CF and where is it found?

VI. Spinal Cord

A. spinal nerves--31 pair

B. cervical enlargement--bulge in the spinal cord in the neck region; gives off nerves to the arms

C. lumbar enlargement--bulge in the spinal cord in the back that gives off nerves the legs

D. composition--gray matter surrounded by white matter

E. functions

1. conducts nerve impulses to and from the brain

2. serves as a relex center

F. Tracts

1. ascending tracts--conduct impulses from body parts and carry sensory information to the brain

2. descending tracts--conduct motor impulses from the brain to muscles and glands

Give the following info concerning the spinal cord:

• characteristics
• location
• composition
• functions
• nerves
• tracts

VII. The Brain

A. General Information

1. weight--3 lbs in an adult

2. one hundred billion neurons and innumerable nerve fibers; neurons do not increase in number after the 2nd month of life; full size by the 18th year

3. divisions

a. Brain Stem

(1) medulla oblongata

(2) pons

(3) midbrain

b. Cerebellum

c. Diencephalon

d. Cerebrum

B. Cerebrum

1. terminology

a. convolutins or gyrus--ridges

b. sulcus--shallow groove

c. fissure--deep groove

2. landmarks

a. cerebral hemispheres--divide cerebrum into left and right halves

b. longitudinal fissure--separates the right and left cerebral hemispheres

c. transverse fissure--separates the cerebrum and cerebellum

d. corpus callosum--deep bridge of nerve fibers that connect the two hemispheres

3. lobes

a. frontal lobe--anterior portion of each cerebral hemisphere; functions in voluntary movements, personality, intelligence, memory and speech

(1) central sulcus--bounds posteriorly

(2) lateral sulcus--bounds inferiorly

b. parietal lobe--posterior to the frontal lobe; functions in sensations (heat, cold, pain, touch, pressure, body position)

c. temporal lobe--lies below frontal lobe; functions in hearing and smell

d. occipital lobe--forms the posterior portion; functions in vision

(1) parieto-occipital fissure--indistinct separation between the parietal and occipital lobes

4. layers

a. cerebral cortex--thin layer of gray matter that constitutes the outermost portion of the cerebrum; contains countless unmyelinated neuron cell bodies

b. masses of white matter make up the bulk of the cerebrum; contain bundles of myelinated nerve fibers

5. functions

a. motor areas--lie in the frontal lobes just anterior to the central sulcus

b. sensory areas--give rise to feelings or sensations; lie in several lobes

c. association areas--related to memory, reasoning, verbalizing, judgement and emotional feelings; occupy anterior portions of the frontal lobes and are widespread in the other lobes

C. Ventricles and Cerebrospinal Fluid

1. ventricles--cavities in the brain filled with cerebrospinal fluid

a. lateral ventricles--largest of the ventricles (first and second), extends into the cerebral hemispheres and occupies portions of the frontal, temporal, and occipital lobes

(1) septum pellucidum--membrane that separates the two lateral ventricles

b. third ventricle--located in the midline of the brain, beneath the corpus callosum

c. fourth ventricle--located in the brain stem just in front of the cerebellum

D. Diencephalon

1. thalmus--consists of two oval masses of gray matter; serves as a relay station for all sensory impulses (except for the sense of smell)

2. hypothalamus--lies below the thalamus where it forms part of the walls and floor of the third ventricle

a. functions

(1) regulation of heart rate and blood pressure

(2) regulation of body temperature

(3) regulation of water and electrolyte balance

(4) control of hunger and regulation of body weight

(5) control of movements and secretions of stomach and intestine

(6) production of substances that stimulate the pituitary gland to release various hormones

(7) regulation of sleep and wakefulness

b. mammillary bodies--two small round masses that form bulges on the hypothalamus; areas of odor recognition

c. pituitary gland--endocrine galnd that secretes several different hormones; MASTER PITUITARY GLAND

3. epithalamus--the most dorsal portion of the diencephalon; forms a thin roof over the third ventricle

a. pineal body--endocrine gland; may function in normal sexual maturity

b. posterior commissure--cross-running white fibers, joining the two halves of the diencephalon

E. Midbrain

1. cerebral aqueduct--tunnel that connects the third and fourth ventricles

2. cerebral peduncles--two bulges, composed of nerve tracts that travel to and from the cerebral hemispheres

3. corpora quadrigemina--dorsal surface of the midbrain; consists of 4 rounded prominences; function in visual and auditory centers

F. Pons--appears as a rounded bulge between the medulla and the cerebellum; connects the two portions

G. Cerebellum

1. location--large mass located below the occipital lobes of the cerebrum; consists of two hemispheres connected in the middle by a structure called the vermis

2. composition--thin outer portion of gray matter with white matter inside

3. functions--all unconscious

a. coordination of all voluntary muscular movements

b. controls skeletal muscles to maintain equilibrium

c. controls posture

H. Medulla Oblongata

1. locations--forms the floor of the fourth ventricle and is continuous with the spinal cord

2. composition--white matter surrounds a central mass of gray

3. functions -- control center for vital activities

a. cardiac center--causes heart to beat more slowly or more rapidly

b. vasomotor center--causes a rise or drop in blood pressure

c. respiratory center--functions with the pons to regulate rate and depth of breathing

d. others--coughing, sneezing, swallowing, and vomiting

4. reticular formation--scattered throughout the medulla, pons, and midbrain. When stimulated, allows the body to return to a state of wakefulness. Without this arousal, the cortex remains unaware and the person remains unconscious.

Name the six major divisions of the brain.

Why is the cerebrum the most iimportant part to humans?

What is the differece between a sulcus, gyrus, and fissure?

Can you point out additional landmarks on this diagram?

What are the major functions of each lobe?

Give the composition of the cerebrum.

What are ventricles?

How many do you have? Name them.

Where are each located?

What is found inside the ventricles?

What separates the laterial ventricles?

VIII. Cranial Nerves

A. numbers--12 pair

B. location--undersurface of the brain

C. numbered--using Roman Numerals from superior to inferior in the order in which they leave the brain

D. mneumonic phrase helps to memorize the order and names--On Old Olympus Towering Tops, A Finn and German Viewed Amber Hops

E. Summary of the Cranial Nerves and their Functions

IX. Autonomic Nervous System

A. Description--part of the peripherial nervous sytem that controls unconscious activities

B. Function--regulating heart rate, blood pressure, breathing rate, body temperature and other activities that aid in the maintenance of homeostasis

C. Divisions

1. Sympathetic--primarily concerned with preparing the body for energy-expending, stressful, or emergency situations

2. Parasympathetic--most active under ordinary, restful conditions; it also counterbalances the effects of the sympathetic division and restores the body to a resting state following a stressful experience.