The Nervous System 35-2 & 35-3

What do YOU see here?

By the end of this lesson you should be able to: Identify the parts and functions of the nervous system Identify and label the parts of the brain and a neuron 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 Central Nervous System (CNS) - the control center of the body; consists of the brain and spinal cord Relays messages Processes information Analyzes information 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 vertebrae Meninges - three layers of connective tissue that wrap the brain and spinal cord Cerebral 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 - Brain Stem - 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 Hypothalamus The thalamus - Recognizes 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 Sensory Division - transmits impulses from the sense organs to the CNS Motor Division - transmits impulses from the CNS to muscles or glands composed of: Somatic Nervous System 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 responses Follow a modified path so they do not need to go all the way to the brain before a response is produced Reflex 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 Sympathetic division – responsible for “fight or flight response”; speeds things up like heart rate & increases blood pressure Parasympathetic division – opposes the sympathetic to slow things down and return to normal

Sensory Receptors Bonus Material Pain receptors - respond to chemicals released by damaged cells so the body can recognize danger Thermoreceptors - detect variations in temperature Mechanoreceptors - sensitive to touch, pressure, sounds, motion and muscle stretching Chemoreceptors - sensitive to chemical in the external environment Photoreceptors - sensitive to light

Homework Complete filling in your Nervous System Chart in your topic packet Worksheets pages BONUS STUDY WEBSITES: Drugs and the Brain The Brain

Back to the impulse…

Types of Neurons: Sensory neurons - carry impulses from the sense organs to the brain and spinal cord Motor neurons - carry impulses from the brain and spinal cord to the muscles and glands 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 threshold Threshold - the lowest level of stimulus that will create an impulse; all-or-none response If 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