Biology Lesson8.1

Lesson 8.1 Outline of Nervous System

Functions:CommunicationCoordinationControlGathering information

Differences between human and animal NS:1. Language2. Judgment3. Problem solving4. Creativeness5. Passing along

heritage

Neurobiologist – biologist who studies the nervous system.

Neurologist – physician who specializes in disorders of the NS.

Two Divisions of NS:

1. Central nervous system (CNS) – brain and spinal cord/nerves

Central Nervous System

Two Divisions of NS:1. Central nervous system (CNS) – brain and spinal cord/nerves

2. Peripheral nervous system (PNS)

nerves that branch from the CNS.

Peripheral Nervous System

CNS Composed of:1. Brain •protected by cranium•has high levels thought•major organ of NS•Message center•Uses info to formulate ideas•Makes decisions•Communicates to body

CNS Composed of:1. Brain

2. Spinal CordThick bundle nerve fibers within spinal cavityHow brain communicates with most of bodyEnds at first lumbar

PNS Composed of:

1. Cranial nervesNerves that come from brain12 pairsBranch from brain stemTransmits messages from/to eyes, ears, mouth, face and scalp

PNS Composed of:

1. Cranial nerves

2. Spinal NervesNerves that come from spinal cord31 pairsTransmit signals to and from the rest of the body

Brain and spinal cord covered by a triple layer

of protective tissue called Meninges.

Cerebrospinal fluid – bathes the brain and runs through fibers of middle meninge to cushion brain.

Nerves are made of bundles of nerve cells called neurons.

Three parts of neurons

1. cell body • contains the nucleus, found only

in spinal cord and brain.

Three parts of neurons

1. cell body

A mass of cell bodies is called a ganglion.Large mass of ganglion called a plexus.Nerve center – plexus that has a certain function.

Three parts of neurons

1. cell body

2. dendrites – short, branched extensions of cell body that receive nerve impulses and conduct them toward the cell body.

Three parts of neurons1. cell body2. dendrites

3. axon – one long extension which carries impulses to other neurons or cells

Axon branches at terminal end.

Nerve impulses travel from the dendrite to cell body to axon.

GLIAL CELLS – also found in the nervous system are cells that SUPPORT AND INSULATE not functional.

Gray Matter vs. White Matter

Gray matter – within spinal cord and brain composed of cell bodies not wrapped by myelin

White matter – made up of dendrites and axons wrapped in myelin.

Myelin •An insulating material that forms a layer, the myelin sheath, usually around only the axon of a neuron.•It is essential for the proper functioning of the NS.•Myelin is an outgrowth of a glial cell.

3 Types of neurons:1. Sensory neurons – transmit

from sense organs to CNS

2. Motor neurons – transmit from CNS to other part of body

3. Interneurons – neurons withinthe CNS that connect sensory andmotor neurons with each other.

Sciatic Nerve – one of the longest nerves of the body.

Branches from spinal cord of lower back and goes to the leg.

PNS Types of Nerve fibers:1. Mixed – both sensory and

motor neurons. Go from sense organ to spinal cord and send message back.

2. Sensory 3. Motor

Divisions of the PNS1. Somatic – skeletal muscle control

2. Autonomic – responsiblefor all routine body activitiesfreeing the mind toconcentrate on biology

class.

Two divisions ANS:Sympathetic –stimulates when danger, stress, or activeex. Increases heart rate when scaredParasympathetic – stimulates when at rest, or brings things back to normal. Ex. Decreases heart rate after scare is over.