the nervous system -...

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The Nervous System

Lecture 3

Lecture 3

1. Introduction

2. Functions of Nervous System

3. Parts of the Nervous System

– Neurons

– Brain

– Spinal Cord

4. Nervous System Health Concerns

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The Nervous System

• Control center for all body activities:

– Communicating, Coordinating, Controlling,

Regulating

The Nervous System

Responds and adapts to changes that occur

both inside and outside the body

(Ex: pain, temperature, pregnancy)

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Homeostasis

Maintenance of a relatively constant internal

state under a much wider range of

environmental conditions.

Functions

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• Sensory - gathers info about changes occurring within and around the body;

Functions of the Nervous System

• Integrative - information is “brought together,” interpreted, to create sensations, create thoughts, add to memory, make decisions, etc.


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• Motor - sending of signals to muscles and/or glands to elicit a response


Bottom Line = Maintenance of Homeostasis


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Parts of the

Nervous System

Main Divisions of the Nervous System

1. Central Nervous System (CNS)

– Brain and Spinal Cord

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2. Peripheral Nervous System (PNS)

– Nerves and Ganglia (bundles of nerve cells)

located outside of the brain and spinal cord

Main Divisions of the Nervous System

Common to both systems:

Neurons (Nerve Cells) -

microscopic cells that

make up the brain, spinal

cord, and nerves

- 30,000 neurons can fit on a

pinhead

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Neurons

Cell Body with nucleus

Dendrites - fibers that

receive messages

from other neurons

Axons - fibers that send

messages to other neurons

Neuron

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Neuron

Action Potential – electrical signal

Signal Propagation in Neurons

Saltatory (jumping) Conduction Speed- 100 meters/second!

Myelin Sheath

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Neuron

• Neurons do NOT

touch each other; there

is a gap between them

called a synapse

• Messages are sent across

the synapses by special

chemicals called

neurotransmitters

Neuron - Synapse

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Multiple Sclerosis

Communication Between

Neurons

• The use of

neurotransmitters

causes an electrical

current

• There is enough

electrical current in the

brain to power a

flashlight

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CNS - The Brain

The Brain • weighs 1300 - 1400 g

• made up of about 100

billion neurons

• “the most complex living

structure on the

universe” Society for Neuroscience

• makes us who we are

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Cerebrum -The largest division of the brain. It

is divided into two hemispheres, each of which is

divided into four lobes.

Cerebrum Cerebrum

Anatomy of the Brain

Cerebrum - Responsible

for:

- Thought

- Language

- Senses

- Memory

- Voluntary movement

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Brain Surface Features

• Gyri – Elevated ridges “winding” around the

brain.


• Sulci – Small grooves dividing the gyri

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• Fissures – Deep grooves, generally dividing

large regions/lobes of the brain

Gyri (ridge)

Fissure

(deep groove)

Sulci

(groove)

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Wilder Penfield 1891 - 1976

Cortical Homunculus


Cerebellum : at base of

brain

Does not initiate

movement, but is..

Responsible for:

- Muscle coordination

- Balance

- Posture

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Cerebellar Agenesis Born without a cerebellum


Brain Stem : connects

brain to spinal cord

Responsible for:

- Breathing

- Swallowing

- Heartbeat

- Blood pressure

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CNS – Spinal Cord

Spinal Cord - Column of nerves from brain to tailbone – protected by vertebral column

Responsible for:

- Conducting impulses between the brain and the rest of the body

CNS – Spinal Cord

Coccygeal region

Cervical region

Thoracic region

Lumbar region

Sacral region

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The part of the

nervous system

comprising the nerves

and ganglia outside of

the brain and spinal

cord.

Peripheral Nervous System (PNS)

The main function of the PNS:

− connects the central nervous system (CNS) to

the limbs and organs

− Serves as a communication relay between the

brain and the extremities

Peripheral Nervous System (PNS)

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Peripheral Nervous System (PNS) Nerves - visible bundles of nerve cells

that extend from the brain and

spinal cord to all other parts of the

body

Types of Nerves

Sensory nerves - carry

messages from body to

brain (pain, pressure,

temperature)

Motor nerves – carry

messages from brain to

body to respond

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Reflex Action

• If you were cooking and you accidentally

touched a hot pot on your stove, you would

involuntarily (and nearly instantaneously)

snatch your hand away from the pot. This

response is called a ‘reflex action'.

Reflex Arc Bypasses the brain…

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Nervous System Health Concerns


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Concussion A temporary

disturbance of the

brain’s ability to

function due to a hard

blow to the head

Chronic Traumatic Encephalopathy (CTE) is a

progressive degenerative disease of the brain found in

athletes (and others) with a history of repetitive brain

trauma.

Paralysis

A loss of sensation and movement of part of the body

due to an injury of the spinal cord or brain

Nervous System Health

Concerns

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Parkinson’s Disease

The brain does not produce enough of the neurotransmitter that

transmits messages from the brain to the muscles

Symptoms: tremors, rigid muscles, shuffling walk, and loss of

facial expression

Alzheimer’s Disease A gradual shrinking of the neurons in the cerebrum

and a build up of tangles and plaques that disrupt

nerve function.

Symptoms: memory loss, emotional disturbances,

inability to function on own, death

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