The Nervous System 35-2 & 35-3. What do YOU see here?

The Nervous System

35-2 & 35-3

What do YOU see here?

By the end of this lesson you should be able to:

1) Identify the parts and functions of the nervous system

2) Identify and label the parts of the brain and a neuron

3) Describe how a nerve impulse is transmitted

Function of the Nervous System:

Body communication

Controls and coordinated body functions

Responds to internal and external stimuli

Carries messages (electrical impulses) along nerve cell called neurons

Two Main Parts of the Nervous System

1) Central Nervous System (CNS) - the control center of the body; consists of the brain and spinal cord

1) Relays messages2) Processes information3) Analyzes information

2) Peripheral Nervous System (PNS) - receives information from the environment and sends commands from the CNS to the organs and glands

Protection for the CNS

Skull and vertebraeMeninges - three layers of connective tissue that wrap the brain and spinal cordCerebral spinal fluid - fluid surrounding the brain and spinal cord that acts as a shock absorber; also allows for nutrients and wastes to be exchanges

The Brain

Parts of the Brain

Cerebrum - Largest part composed of folds and grooves that make up the four major lobes

Responsible for voluntary activites

Site of learning, intelligence, and judgement

Left side (hemisphere) controls that right hand side of your body and the reverse

Consists of two layers (1) outer cerebral cortex made of only grey material and (2) inner white matter

Parts of the Brain

Cerebellum - Second largest brain region

Found at the back of the skull

Coordinates and balances muscle movement

Brain Stem - Connects the brain to the spinal cord

Contains the pons and medulla oblongata

Responsible for blood pressure, heart rate, breathing…

Parts of the Brain

The HypothalamusRecognizes hunger, thirst, fatigue, anger, and body temperature

Coordinates the nervous and endocrine system

The thalamus - Receives sensory messages and sends them to the cerebrum

Spinal Cord

Contains 31 nerves that connect the brain to the rest of the body

Processes certain reflexes - quick automatic response to a stimulus like blinking

Peripheral Nervous System

1) Sensory Division - transmits impulses from the sense organs to the CNS

2) Motor Division - transmits impulses from the CNS to muscles or glands composed of:

1) Somatic Nervous System

2) Autonomic Nervous System

The Somatic Nervous System

Deals with activities that are under your conscious control

Ex: Moving your pen, poking your neighbor, and reflexes

Reflexes

Rapid responsesFollow a modified path so they do not need to go all the way to the brain before a response is producedReflex arc - includes a sensory neuron, a motor neuron, and an effector (muscle)

The Autonomic Nervous System

Responsible for involuntary, automatic movements

The Autonomic Nervous System

1) Sympathetic division – responsible for “fight or flight response”; speeds things up like heart rate & increases blood pressure

2) Parasympathetic division – opposes the sympathetic to slow things down and return to normal

Sensory ReceptorsBonus Material

1) Pain receptors - respond to chemicals released by damaged cells so the body can recognize danger

2) Thermoreceptors - detect variations in temperature

3) Mechanoreceptors - sensitive to touch, pressure, sounds, motion and muscle stretching

4) Chemoreceptors - sensitive to chemical in the external environment

5) Photoreceptors - sensitive to light

Homework

Complete filling in your Nervous System Chart in your topic packetWorksheets pages BONUS STUDY WEBSITES:

Drugs and the BrainThe Brain

Back to the impulse…

Types of Neurons:

1) Sensory neurons - carry impulses from the sense organs to the brain and spinal cord

2) Motor neurons - carry impulses from the brain and spinal cord to the muscles and glands

3) Interneurons - connect sensor and motor neurons

Structure of Neurons

Label these parts and make sure they are defined in your vocabulary section

What do neurons do?

Transmit nerve impulses

Relies on electrical charges

Uses Sodium (Na+) and Potassium (K+) to create a charge difference between the nerve cell and its outer environment

The Neuron in Action

Check out what is happening here!

1) Resting State of a Neuron

Resting Potentail

The Sodium (Na+) - Potassium (K+) pump maintains a net negative charge on the inside of the neuron

The Pump

Sodium Potassium Pump- Resting State

3 Na+ Out

2 K+ In

___________

Net Charge = ?

2-3) Action Potential/Nerve Impulse

An outside stimulus creates a nerve impulse that travels down the axon away from the cell body

The inside of the nerve cell is temporarily more positive - Sodium (Na+) flow into the nerve cell

4-5) Action Potential

Behind the impulse, K+ flows out restoring the negative

The impulse leaves through the terminal and transmits to neighboring dendrites

How does a neuron “know” to send an impulse?

A nerve will only transmit an impulse if the initial stimulus that is picked up at the dendrites is larger than the thresholdThreshold - the lowest level of stimulus that will create an impulse; all-or-none responseIf the stimulus is weaker than threshold NO IMPULSE will be produced

The Nerve Impulse

What does it look like?

The Synapse

Occurs between one axon and its neighboring dendrite

Relies on chemical called neurotransmitters