BIO 120 Chapter 11 Nervous System

3 major functions of the nervous system

1. sensory input

2. integration

3. motor output

2 main subdivisions of the nervous system

1,central nervous system (brain and spinal cord)

2, peripheral nervous system (all nerves)

What is integration?

thinking

What are the two divisions of the PNS?

sensory (afferent) and motor (efferent)

What are glia?

supporting cells, specialized connective tissue cells that support neurons

Neurons

nerve cells that is amitotic (no ability to divide)

Astrocytes

star-shaped cells that anchor small blood vessels to neurons

Microglia

Act as phagocytes, eating damaged cells and bacteria, act as the brains immune system (CNS)

Ependymal cells

line cavities of the brain and spinal cord, circulate cerebrospinal fluid via cilia (CNS)

Oligodendroglia

glial cell that produces myelin sheath (CNS_

Schwann cells

coil around the axon and are responsible for the formation of myelin, adjacent schwann cells don't touch

Satellite cells

hold neurons close to blood vessels in PNS

Soma

cell body

Dendrites

processes that extend from cell body like branches, receive signals from other neurons and bring them toward the cell body

Axon

process that conducts impulses away from the nerve cell

Axon terminal

The endpoint of a neuron where neurotransmitters are stored

axon hillock

Cone shaped region of an axon where it joins the cell body.

myelin sheath

fatty substance that protects and insulates electrical impulse of the axon, also increases impulse transmission speed

Nodes of Ranvier

a gap in the myelin sheath of a nerve, between adjacent Schwann cells.

5 steps of exciting a neuron

1. Cell membrane at rest= polarized (-70mV)

2. Stimulus= excited neuron, becomes depolarized

3. Depolarization= AP (nerve impulse) (-55mV to 30 mV)

4. Repolarization= back to resting potential

5. Back to resting Potential (-70mV)

reflex arc

receptor, sensory neuron, integration center, motor neuron, effector

patellar reflex

knee jerk

pupillary reflex

both pupils constrict when light is directed at one eye, useful for checking brain stem function and drug use

flexor reflex

moves a limb away from a painful stimulus

plantar reflex

elicited touching the soles of the feet. toes curl downward

Babinski reflex

in response to the sole of the foot being stroked, a big toe moves upward or toward the top surface of the foot and the other toes fan out, useful in checking for motor cortex or corticospinal tract damage

Actions of Neurotransmitters

-excitatory (cause depolarization)

-inhibitory (reduce ability to cause action potential)

-direct (bind to and open ion channels provoking a rapid action potential change)

-indirect (no direct contact with ion channels, long-lasting effects)