The Nervous System. Functions of the Nervous System Control center for all body activitiesControl center for all body activities Responds and adapts to

The Nervous SystemThe Nervous System

Functions of the Nervous Functions of the Nervous SystemSystem

• Control center for all Control center for all body activitiesbody activities

• Responds and adapts Responds and adapts to changes that occur to changes that occur both inside and both inside and outside the bodyoutside the body

(Ex: pain, temperature, (Ex: pain, temperature, pregnancy)pregnancy)

Neurons

NeuronsNeurons :microscop:microscopic nerve cells that ic nerve cells that make up the brain, make up the brain, spinal cord, and spinal cord, and nerves (30,000 nerves (30,000 neurons can fit on a neurons can fit on a pinhead)pinhead)

Anatomy of a NeuronAnatomy of a Neuron

Each neuron Each neuron contains:contains:

• Cell bodyCell body with with nucleusnucleus

• DendritesDendrites : fibers : fibers that receive that receive messages from messages from other neuronsother neurons

• AxonsAxons : fibers that : fibers that send messages to send messages to other neuronsother neurons

Anatomy of a Neuron

• Neurons do NOT touch; Neurons do NOT touch; there is a gap between there is a gap between them called a them called a synapsesynapse

• Messages are sent Messages are sent across the synapses by across the synapses by special chemicals special chemicals called called neurotransmittersneurotransmitters

Communication Between Communication Between NeuronsNeurons

• The use of The use of neurotransmitters neurotransmitters causes an causes an electrical currentelectrical current

• There is enough There is enough electrical current electrical current in the brain to in the brain to power a flashlightpower a flashlight

Two Major Two Major Divisions of the Divisions of the Nervous SystemNervous System

Central Nervous SystemCentral Nervous System

•Consists of the brain and Consists of the brain and spinal cord.spinal cord.•Largest part of the Largest part of the nervous systemnervous system•Integrates & coordinates Integrates & coordinates all of the information that all of the information that it receives from all of the it receives from all of the parts of the body parts of the body

Central Nervous SystemCentral Nervous System The BRAIN The BRAIN • A mass of 100 billion neurons A mass of 100 billion neurons

located inside the skulllocated inside the skull• The mass of an adult human brain is The mass of an adult human brain is

approximately 2.87 to 3.1 poundsapproximately 2.87 to 3.1 pounds• A newborn human brain is about A newborn human brain is about

0.77 to 0.88 pounds0.77 to 0.88 pounds

• The average Male's brain weighs 3 The average Male's brain weighs 3 poundspounds

• The average Female's brain weighs The average Female's brain weighs 2.8 pounds2.8 pounds

• Learning occurs as more and Learning occurs as more and stronger connections are made stronger connections are made between neuronsbetween neurons

Anatomy of the BrainAnatomy of the Brain

CerebrumCerebrum • largest part of human largest part of human

brainbrain• responsible for:responsible for:

- Thought- Thought

- Language- Language

- Senses- Senses

- Memory- Memory

- Voluntary movement- Voluntary movement


CerebrumCerebrum • divided in to two hemispheres; the divided in to two hemispheres; the

right and left right and left • the dividing point is a deep grove the dividing point is a deep grove

called the longitudal cerebral fissurecalled the longitudal cerebral fissure• the different sides of the cerebrum the different sides of the cerebrum

do different things for the opposite do different things for the opposite sides of the body. The right side of sides of the body. The right side of the cerebrum controls things such as the cerebrum controls things such as imagination and 3-D forms. The left imagination and 3-D forms. The left side, controls numbering skills, side, controls numbering skills, posture, and reasoning. posture, and reasoning.

• the hemispheres also consist of the hemispheres also consist of many other parts such as the lobes.many other parts such as the lobes.

Retrieval of a MemoryRetrieval of a Memory

A memory is not a A memory is not a snapshot stored snapshot stored in the brain – it in the brain – it must be put must be put together from together from information information stored in various stored in various parts of the brainparts of the brain


Cerebellum • located at base of

brain• responsible for: - Muscle coordination - Balance - Posture


Cerebellum • accounts for only 10% of

the brain's total weight• maintains muscle tone• about the size of an

orange in size and consists of two hemispherical lobes

• injury to the cerebellum usually results in disruption of eye movements, balance, or muscle tone.


Brain Stem Brain Stem • connects brain to connects brain to

spinal cordspinal cord• responsible for:responsible for:

- Breathing- Breathing

- Swallowing- Swallowing

- Heartbeat- Heartbeat

- Blood pressure- Blood pressure


Brain Stem Brain Stem • upper segment of upper segment of

the brain stem, the brain stem, the pons, contains the pons, contains nerve fibers that nerve fibers that connect the two connect the two halves of the halves of the cerebellumcerebellum


Brain Stem Brain Stem • below the pons and below the pons and

continuous with the continuous with the spinal cord is the spinal cord is the medulla, which medulla, which controls many controls many involuntary muscular involuntary muscular and glandular and glandular activities, including activities, including breathing, heart breathing, heart contraction, artery contraction, artery dilation, salivation, dilation, salivation, vomiting, and vomiting, and probably laughingprobably laughing

Central Nervous SystemCentral Nervous System Spinal Cord Spinal Cord • column of nerves column of nerves

from brain to coccyx from brain to coccyx – protected by the – protected by the vertebrae of spinevertebrae of spine

• responsible for responsible for conducting impulses conducting impulses between the brain between the brain and the rest of the and the rest of the bodybody

**Impulses may Impulses may travel as fast at travel as fast at 268 miles/hr268 miles/hr

Peripheral Nervous Peripheral Nervous SystemSystem

Nerves Nerves (Neurons)(Neurons)

visible bundles of visible bundles of axons and axons and dendrites that dendrites that extend from the extend from the brain and spinal brain and spinal cord to all other cord to all other parts of the body parts of the body


Sensory neuronsSensory neurons

carry messages from carry messages from the body and its the body and its environment to the environment to the brain… including brain… including pain, pressure, and pain, pressure, and temperature temperature (stimuli)(stimuli)


Motor neurons Motor neurons

carry messages from carry messages from the brain to body. the brain to body. The muscles respond The muscles respond to these messagesto these messages

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The Nervous System. Functions of the Nervous System Control center for all body activitiesControl center for all body activities Responds and adapts to