The Nervous System Neural Anatomy

Neurons: The Building Blocks of the Nervous System Module 7: Neural and Hormonal Systems

Nervous System The electrochemical communication system of the body Brings information to the brain from the senses Sends messages from the brain to the body to enact behavior

Neuron The basic building block of the nervous system -- a nerve cell Neurons perform three basic tasks –Receive information –Carry the information –Pass the information on to the next neuron

Types of Neurons Afferents, or “sensory neurons”, carry information from the body to the brain

Types of Neurons Interneurons, found in the spinal cord and the brain, interpret the incoming information and determine the next course of action

Types of Neurons Efferents, or “motor neurons”, carry information from the spinal cord or the brain to the rest of the body in order to initiate behavior

Parts of the Neuron

Parts of the Neuron - Dendrites

Parts of the Neuron - Soma

Parts of the Neuron - Axon

Parts of the Neuron – Myelin Sheath

Parts of the Neuron - Terminals

Neuron

The Neural Network How does the whole system fit together?

A neuron is considered at “resting potential” when there is no sensory input and it is awaiting stimulus.

A Neural Chain

Special receptors in each of the five senses detect stimuli from the outside world.

When a neuron receives enough information to pass on, it has reached its “action potential” and fires off the message to the next neuron in the link

Once a neuron fires, it must re-set momentarily in order to receive another message. This re-set period is called “refraction”. It cannot fire during this period.

A Neural Chain

Sensory neurons carry all of the input to the spinal cord.

A Neural Chain

Interneurons in the spinal cord and the brain process the information and decide the best course of behavior.

A Neural Chain

Motor neurons from the brain travel back down the spinal cord and out to the appropriate parts of the body with the appropriate behavior instructions.

A Neural Chain

Neural Communication: The Neural Impulse

A neuron firing is like a toilet flushing 1.Like a Neuron, a toilet has a resting potential. The toilet is “charged” when there is water in the tank and it is capable of being flushed.

Neuron firing like a Toilet 2. Like a Neuron, a toilet has an action potential. When you flush, an “impulse” is sent down the sewer pipe.

Neuron firing like a Toilet 1.Like a neuron, a toilet has a refractory period. There is a short delay after flushing when the toilet cannot be flushed again because the tank is being refilled 2.Like a Neuron, a toilet operates on the all-or-nothing principle – it always flushes with the same intensity, no matter how much force you apply to the handle

Communication Between Neurons Module 7: Neural and Hormonal Systems

Synapse The electrical message from the dendrite travels down the axon to the terminal buttons. Here, it changes into a chemical message to be transferred to the next neuron. The tiny, fluid filled gap between the axon terminal of one neuron and the dendrite of another neuron is called the synapse.

Neurotransmitters A chemical messenger that travels across the synapse from one neuron to the next

Neurotransmitters

Acetylcholine (ACh) Enables muscle action, learning, and memory Undersupply, as ACh- producing neurons deteriorate, marks Alzheimer’s disease

Dopamine Influences movement, learning, attention, and emotion Excessive dopamine receptor activity is linked to schizophrenia; a lack of dopamine produces the tremors and lack of mobility of Parkinson’s disease

Serotonin Affects mood, hunger, sleep, and arousal Undersupply is linked to depression; Prozac and other anti-depressants raise serotonin levels

Norepinephrine Helps to control alertness and arousal Undersupply can depress mood

Endorphins Natural opiates that are released in response to pain and vigorous exercise Endorphins

The Structure of the Nervous System

The Nervous System

Central Nervous System (CNS) The brain and spinal cord The brain is the location of most information processing. The spinal cord is the main pathway to and from the brain.

Spinal Cord

Divisions of the Nervous System

Peripheral Nervous System (PNS) The sensory and motor nerves that connect the central nervous system to the rest of the body Peripheral means “outer region” The system is subdivided into the somatic and autonomic nervous systems.

Divisions of the Nervous System

Somatic Nervous System The division of the peripheral nervous system that controls the body’s skeletal muscles Contains the motor nerves needed for the voluntary muscles

Divisions of the Nervous System

Autonomic Nervous System The division of the peripheral nervous system that controls the glands and muscles of the internal organs Monitors the autonomic functions Controls breathing, blood pressure, and digestive processes Divided into the sympathetic and parasympathetic nervous systems

Divisions of the Nervous System

Sympathetic Nervous System The part of the autonomic nervous system that arouses the body to deal with perceived threats and stress

Divisions of the Nervous System

Parasympathetic Nervous System The part of the autonomic nervous system that calms the body Brings the body back down to a relaxed state

Divisions of the Nervous System

The Sympathetic and Parasympathetic Divisions of the Autonomic Nervous System

The Sympathetic and Parasympathetic Nervous Systems Physical Responses