Neurons & the Nervous System Chapter 2: The Brain and Behavior

Today’s Goal  You will be able to…. Identify the parts of a neuron and their functions in creating & sending neural messages.

Parts of the Neuron Neurons: nerve cells Dendrites: branch-like end of neuron which receives messages Cell body (soma): contains nucleus Axon: long tail-like end of neuron which transmits (sends) messages

Myelin: fatty substance that speeds up transmission of impulse Axon terminals/Terminal buttons: contain neurotransmitters, release them during neural impulse Terminal buttons (axon terminal): bulb-shaped structure at end of axon

Types of Neurons Sensory neurons: send messages from sensory receptors to the spinal cord & brain Motor neurons: relay messages from brain & spinal cord to muscles & glands Interneurons: transmits neural stimulus between sensory & motor neurons (found only in Central nervous system)

Simple Reflex Arc Communication goes directly from interneurons in spinal cord to motor neurons to move (reflexively) at the same time the info is going to the brain to be perceived

The Nervous System Central Peripheral Autonomic Sympathetic Parasympathetic Somatic

Central v. Peripheral Central contains brain & spinal cord Peripheral – sensory & motor neurons that transmit messages between brain and muscles & glands

Autonomic v. Somatic Somatic – voluntary - controls purposeful body movements Autonomic – involuntary – automatic activities heartbeat, respiration, digestion, dilation of pupils, etc.

Sympathetic v. Parasympathetic Sympathetic = “Fight-or-flight” response Uses energy reserves to cope with stress or emergency Adrenaline! Parasympathetic = “Rest and digest” Conserves & builds up stored energy reserves

Today’s Goal  You will be able to…. Describe how neurons communicate to send messages in the brain and body

The Synapse Synapse (synaptic cleft): gap between dendrites of one neuron and axon of another Receptor sites: parts of dendrite which receive neurotransmitters Neurotransmitters: chemical substances involved in sending neural impulses

Neural Impulse: electrochemical firing of a nerve cell Resting potential: electric potential when neuron not firing (-70 millivolts) Threshold: level of stimulation required to trigger a neural impulse (excitatory – inhibitory = threshold)

Neural Impulse: electrochemical firing of a nerve cell Action potential: when a neuron fires the impulse (sends the message) Refractory period: phase after firing an impulse, neuron will not fire All-or-none principle: neuron will fire or not fire, no in-between

Resting potential

Synapses Excitatory neurotransmission: increases the likelihood that postsynaptic neuron will fire Inhibitory neurotransmission: decreases likelihood that postsynaptic neuron will fire

Today’s Goal  You will be able to… Discuss how the major neurotransmitters affect the body and one’s behavior

Substances that Affect Neurotransmitters Agonist: similar to the NT, mimics its effects Antagonist: inhibits the release of NT by sending neuron, or blocks receptor site for NT on receiving neuron

Neurotransmitters Acetylcholine (ACh) EXCITATORY (sometimes inhibitory) Memory, muscle contractions, learning Malfunctions: Alzheimer’s Disease

Neurotransmitters Serotonin Dopamine (DA) Reward/pleasure, movement, attention Malfunctions: Too little  Parkinson’s, Too much  Schizophrenia Serotonin Mood regulation, sleep and appetite regulation, concentration, learning Imbalance  depression

Neurotransmitters Norepinephrine Involved in autonomic nervous system (sympathetic) arousal Imbalances: Depression, seizures GABA Function: Reduce anxiety, relax for sleep Imbalance: Anxiety disorders, tremors, insomnia Endorphins  pain control