Nervous SystemControl and Coordination

Intro to Nervous System Movie

I. FunctionsA. Send and receive informationB. Monitor and respond to stimuli

1. Stimuli – internal or external change that causes the body to respond (ex: heat, light, touch)

C. Sensory input – vision, hearing, balance, smell, taste, and touch

D. Motor output – muscle contraction and movement

E. Memory and integration of informationF. Maintain homeostasis

1. Homeostasis – maintaining constant conditions in the body despite changes in the internal/external environments

II. The Neuron (nerve cell)A. Neurons are specialized cells that carry

information in the form of an electrical signal called an impulse

3 Types of Neurons:1. Sensory – carry impulses from the

sense organs to the spinal cord and brain

2. Interneurons – Connect sensory and motor neurons and carry impulses between them

3. Motor – carry impulses from brain and spinal cord to muscles and glands

B. Anatomy of a Neuron1. Cell Body

a. Controls all activities of the cellb. Contains nucleus

CellBody

2. Dendritesa. Carry impulses from the environment or

from other neurons to the cell bodyDendrite

3. Axona. Long fiber that carries impulses away from

the cell bodyb. Ends in small swellings called axon

terminals Axon

Axon terminals

4. Myelin Sheatha. Insulates the axonb. Increases impulse speed

Impulse Movement is One-Directional

Dendrites Cell Body Axon Axon terminals

Nervous Tissue (Neurons)

C. The Synapse1. Gap between the axon

of one neuron and the dendrites of the next neuron.

2. Neurons do not touch!3. When the impulse

reaches the end of the axon, chemicals called neurotransmitters are released and carry the signal to the next neuron.

Vesicle

Axon

Axon terminal

Synaptic cleft

Neurotransmitter

Receptor

Dendrite of adjacent neuron

Direction of Impulse

Synaptic Transmission

III. Organization of the Nervous System

Divided into two parts:A. Central N.S. - Control center of the

body that relays messages, and processes and analyzes information1. Brain2. Spinal Cord

B. Peripheral N.S. - made of all the nerves that receive information from the environment and relays to and from CNS and sensory, motor and gland cells1. Somatic N.S.2. Autonomic N.S.

IV. The Brain The main

control center of the human body

A. Cerebrum1. Largest part of brain2. Controls learning, intelligence, and judgment3. Outer layer is cortex; many fold and wrinkles

Why?4. Left and right hemispheres are connected by

corpus collosumCerebrum

B.Cerebellum1. Coordinates the actions of muscles &

maintains balance

Cerebellum

C. Brain Stem1. Connects brain to spinal cord2. Comprised of midbrain, pons, and medulla

oblongata3. Medulla oblongata controls involuntary

activities like heartbeat, breathing, barfing, sneezing, etc.

Medulla oblongata

D. Spinal Cord1. Carries info between

brain & body2. Process simple

responses called reflexes

V. Reflexes Reflexes are an involuntary, automatic response

to stimuli Controlled by 5-part reflex arc:

1. Sensory receptors on finger reacts to stimulus (heat)

2. Impulse is carried to the spinal cord by a sensory neuron

3. In the spinal cord, the impulse is transferred by an interneuron to motor neuron

4. Motor neurons conducts the impulse to an effector (arm muscles)

5. Effector responds to the impulses by contracting (hand gets pulled away from the heat)

VI. Peripheral Nervous System

Receives information from the environment and relays to and from CNS and sensory, motor and gland cells

Two divisions:1. Somatic NS (voluntary) responds to

external stimuli.a. Made of nerves that go from the CNS to

skeletal musclesb. Regulates activities that are under

conscious control (e.g. picking your nose)

c. Some reflex control2. Autonomic (involuntary) NS respond to

internal stimulia. Controls heart rate, breathing,

digestion, and glandular function

Autonomic Nervous System

VII. The Senses5 General Sensory Receptors: pain,

thermo-, mechano-, chemo- and photoreceptors.

Where do you think these different types of receptors are found and what is their function?

A. VisionB. Hearing and BalanceC. Smell and TasteD. Temperature and pressure

VIII. Drugs and the Nervous SystemA. Stimulants

1. Accelerate HR, BP, and breathing rate2. Increases the release of

neurotransmitters; leads to release of energy and feeling of well-being

3. When effect wears off, brain’s supply is depleted leaving the user depressed and fatigueda. Caffeine – prevents binding of

adenosineb. Cocaine – sudden release of

dopaminec. Methamphetamines – same effect as

cocaine

B. Depressants1. Slow down HR, lower BP and breathing

rate, relax muscles and relieves anxietya. Alcohol – physical and mental

impairment, depression, brain and liver damage

b. Marijuana – more lung damage than cigarettes; memory loss, reduced levels of testosterone in males

c. Sleeping Pills