The Nervous System

I. General organization of nervous systemA. CNS 1. brain 2. spinal cordB. PNS 1. sensory 2. motor a. Somatic b. ANS -sympathetic -parasympathetic

II. Nervous Supporting Cells - neuroglia

A. Astrocytes1. Connect to

capillaries2. Mopping up

chemical environment of brain as far as potassium ions and neurotransmitters

B. Microglia

• 1. spider-like phagocytes

• 2. debris, dead brain cells, bacteria

C. Ependymal cells

• 1. lines cavities in CNS• 2. beating of cilia moves

cerebrospinal fluid• 3. fluid nourishes and cushions

CNS

D. Oligodendrocytes

• 1. wrap axons of nerve cells with fatty layer

• 2. produces myelin sheath• 3. speeds conduction

E. Glia cells in general• 1. resemble neurons• 2. not excitable• 3. supportive cells• 4. capable of repeated mitosis• 5. gliomas-glial tumors

III. NeuronsA. Structure

• 1. cell body• 2. nissl bodies-rer• 3. dendrites• 4. axon• 5. axon hillock• 6. axon collateral• 7. axon terminals• 8. neurotransmitters• 9. synaptic cleft

B. Myelin sheath

• 1. functions• 2. PNS-Schwann cell• 3. Node of Ranvier• 4. Can form a pathway for

regrowth of damaged axon

• 5. multiple sclerosis

C. Neurons classified by function

• 1. afferent• 2. interneuron• 3. efferent• 4. ganglia• 5. nuclei

D. Neurons classified by structure

• 1. multipolar• 2. bipolar• 3. unipolar

IV. Neuron physiology• A. Resting membrane

potential• B. Action potential-nerve

impulse

C. Propagation of action potential

• 1. diagram on board• 2. a lot like dominoes• 3. http://www.youtube.com/watch?v=7tBWl4GE8rk&NR=1

D. Anatomy of a synapse• 1. presynaptic membrane• 2. synaptic cleft• 3. postsynaptic membrane• 4. synaptic vesicles• 5. receptor sites for transmitter

substance

E. Physiology of synapse• 1. action potential arrives• 2. Calcium ion channels

open• 3. synaptic vesicles fuse

with membrane• 4. transmitter substance

released• 5. diffusion of transmitter

substance• 6. binding to receptors• 7. creates a graded

potential• 8. may bring postsynaptic

membrane to threshold• 9. nerve gas-blocks

cholinesterase

F. You tube of synaptic events

• http://www.youtube.com/watch?v=z3F5dfmQ3hk

V. Functional Anatomy of the Brain A. Introduction

• 1. difficult to talk about• 2. two fistfuls of pinkish/gray• 3. wrinkled• 4. consistency of cold oatmeal• 5. three pounds• 6. hugely complex• 7. four basic regions

– a. Cerebral hemispheres– b. Diencephalon– c. Brain stem– d. cerebellum

B. Cerebral hemispheres

• 1. most important part• 2. overshadows

diencephalon and brain stem

• 3. mushroom cap covers top of stalk

• 4. gyri• 5. sulci• 6. fissures-ie longitudinal

cerebral fissure

7. Lobes of cerebrum

• a. Frontal lobe controls mainly motor function

• b. Primary motor area is on the precentral gyrus -governs conscious motor control which can be mapped

Motor homunculus

c. Motor homunculus

• -specific regions of the precentral gyrus control specific body parts

• -finer the movements, the more brain area needed to control those movements

d. Premotor area • -learned

repetitive tasks

• Typing, playing piano

• Athletes learn tasks by visualizing motions

• Ingrained in this area

e. Broca’s area• speech center• Usually located left cerebral hemisphere• Damage here causes inability to speak

8. Other important areas of cerebral hemispheres

• a. Primary somatic sensory area• b. Visual area in occipital lobe• c. Complex memory in the temporal lobe• d. Note close proximity to olfactory area• e. Anterior association area-higher intellectual reasoning and

socially acceptable behavior

9. Sensory homunculus

C. Diencephalon1. Thalamus a. Encloses third vent. b. Screens incoming sensory messages2. Hypothalamus a. ANS center for body temperature and water balance b. Regulates pituitary3. Epithalamus a. Pineal gland b. Choroid plexus

D. Brain stem• 1. size of thumb• 2. midbrain• 3. pons • 4. medulla• 5. interchange

for sensory and motor paths

• 6. nuclei for respiratory, blood pressure, heart rate, RAS

E. Cerebellum

1. Cauliflower shape

2. Controls balance and equilibrium

3. Produces smooth and coordinated muscular contractions

VI. Protection of the brain

• A. Meninges• 1. dura mater• 2. arachnoid • 3. pia mater• B. CSF• 1. produced

choroid plexi• 2. flow• 3. functions• 4. hydrocephalus