Semes2_Anat_Week_3_Nervous System_Elisa_GBC_2

• Sensory input
• integration of the info
• Motor out put

The PNS nevers extend from the brain to the spine cord

Function - serve as communication lines among the sensory organs

•Sensory (afferent)(TOWARDS) division–Nerve fibers that carry information to the central nervous system

•Motor (Efferent) (exit) division–Nerve fibers that carry impulses away from the central nervous system organs

b. Somatic and Autonomic!!!

•Somatic nervous system = voluntary

•Autonomic nervous system = involuntary

• Astrocytes–
• Microglia
• Oligodendrocytes
• Ependymal cells

* Star shaped cell the count for nearly HALF neural tissue.

*they have swollen ends that cling to neurons that anchor them to the blood capillaries.

* they help to protect neurons from harmful substances in the blood

* help to control the chemical environment in the brain by mopping up leaked potassium ions

*

the shape is spider like

they are phagocytes that monitor neurons and dispose of debri

(For example - Dead brain cells and bacteria

* The Ependymal cells line the central cavity of the brain & spinal cord

* The beating of the cilia help circulate cerebrospinal fluid

they wrap their flat extentions around nerve fibers producing fatty insulin called myelin sheaths

DEndrites convey incoming electrical messages toward the cell body

Axons generate nerve impulses and conduct them AWAY from the cell body

Nerve cells

transmit messages from one part of the body to the other

Grey matter contains mostly un-myelinated fibers & cell bodies

White matter consists of thick myelinated fibers (tracks)

A.  Tracts

A.  Nerves

•detect stimuli such as light, heat, pressure; •transmit information about stimuli to CNS;

• Carry impulses from the central nervous system to viscera, muscles, or glands

•Irritability = –respond to a stimulus and convert it to a nerve impulse


•Conductivity = –transmit the impulse to other neurons, muscles, or glands

it means there are LESS positive ions sitting on the inner face of the neuron than there are on the outside

True!!!

The inside of the cell must always be more NEGATIVE

The action potential is an explosion of electrical activity that is created by a depolarizing current.  (A LONG DISTANCE SIGNAL)

Nerve impluse

Resting membrane of a neuron is about -70 mV.

This means that the inside of the neuron is -70 mV 

At rest, there are more sodium ions outside the neuron 

More potassium ions inside that neuron.

Na+ is the major positive ion outside the cell

–The plasma membrane at rest is polarized

–As long as inside is more negative than outside, the cell stays at rest

A. more negative inside

A stimulus depolarizes the neuron’s membrane

The membrane is now permeable to sodium as sodium channels open

A depolarized membrane allows sodium (Na+) to flow inside the membrane