ANATOMY AND PHYSIOLOGY

Chapter 8 The Nervous System

The Nervous System is the major controlling and communicating system in the body

The Nervous System

The means of communication is Electrical impulses

Which causes immediate responses

The Nervous System

Monitor changes occurring inside and outside the body

These changes are called stimuli and the gathered info is called

sensory input

3 major Functions of the Nervous System

Process and interpret sensory input and make decisions about what should be done.

This is called integration

3 major Functions of the Nervous System

Effect a response by activating muscles or glands.

The response is called motor output

3 major Functions of the Nervous System

So…… sensory input integration motor output

Works along with the endocrine system

3 major Functions of the Nervous System

2 Classifications:

CNSCentral Nervous System

Made of brain and spinal cord

The Nervous System

2 Classifications:

PNS

The Nervous System

Peripheral Nervous System

Made of nerves (spinal and cranial)

2 kinds:1. Supporting Cells

Nerve Tissue

2 kinds:2. Neurons

Nerve Tissue

NeurogliaSupporting cells in the CNS

Support, insulate, and protect neurons

Not able to transmit impulses

Never lose ability to divide so most brain tumors are gliomas. Tumors are formed by neuroglia

Nerve Tissue

Neuroglia1. Astrocytes

Nerve Tissue

Star shaped

Cling to neurons

Form a barrier btw neurons and capillaries

Protect neurons from harmful substances in the blood

Pick up excess ions and neurotransmitters

Neuroglia2. Microglia

Nerve Tissue

Phagocytes that dispose of dead brain cells and bacteria

Neuroglia3. Oligodendrocytes

Nerve Tissue

Produce insulating covering called myelin sheath

Supporting cells in the PNS

• Schwann cells

Nerve Tissue

Form the myelin sheath around nerve fibers in the PNS

Supporting cells in the PNS

2. Satellite cells

Nerve Tissue

Protective, cushioning cells

Nerve Cells

NEURONS

Transmit nerve impulses (messages)

Made of:

Cell body

Axon

Dendrite

Nerve Cells

NEURONS

Cell body - Center of cell. Contains the nucleus

Process or fibers extend from the cell body

Nerve Cells

NEURONS

Axon - conducts impulse away from the cell body

Only one per neuron

Nerve Cells

NEURONS

Dendrite - conducts impulse toward the cell body

100s per neuron

1.

2.

3.

4.

5.

dendrites

nucleus

Cell body

Myelin sheath

axon

Nerve Cells

NEURONS

Synapse junction between 2 neurons.

The 2 neurons never actually touch

Nerve Cells

NEURONS

Myelin white fatty covering on the axon.

They protect and insulate

Also increase the rate of nerve impulse transmission

Nerve Cells

NEURONS

Myelin

if the myelin sheath is destroyed as in multiple sclerosis, the person loses the ability to control their muscles.

Nerve Cells

NEURONS

Myelin of the CNS

White matter

Gray matter

myelinated fibers

unmyelinated fibers

Classification

NEURONS

Functional classification groups are according to the direction the nerve impulse is traveling

Afferent

or

Efferent

Classification

NEURONS

Sensory. Carries impulse from organs to CNS

Afferent

Efferent Motor. Carries impulse from CNS to muscles, glands.

Irritability

Conductivity

Properties of Nerve Impulses

Ability to respond to a stimuli

Ability to transmit impulses to other neurons, muscles, glands

Electro-chemical event.Na ion enters cell

K ion leaves the cell causing a resting state.

Properties of Nerve Impulses

depolarization

NA K pump

repolarization

Neurons release neurotransmitters to influence other neurons.

This opens a specific ion channel

Neurotransmitter?

Properties of Nerve Impulses

NA K pump

Active transport

acetycholine

A reflex is a rapid predictable response to a stimulus

Autonomic

Somatic

Reflex

Regulates activities of smooth muscles, the heart and glands.

Stimulates skeletal muscles

Autonomic

Somatic

Reflex

Salivary reflex

Pupillary reflex

Patellar reflex

Sucking reflex

Normal reflexes indicate normal nervous system functions

Reflex

Plantar reflex (Babinski) The normal reflex is toe flexion. If the toes extend and separate, this is an abnormal finding called a positive Babinski's sign.

Neural Tube

Ventricles

Central Nervous System CNS

How nervous system 1st appears in embryo

Chambers. We have 4

Neural Tube

Deficiency of Folic acid = neural tube birth defects

Also called B9

Leafy vegetables such as spinach and turnip greens dried beans and peas, fortified cereal products,sunflower seeds and certain other fruits and vegatables are rich sources of folate. Some breakfast cereals are fortified with 25% to 100% of the recommended dietary allowance (RDA) for folic acid.

Folic Acid