Chapter 35 The Nervous System

Nervous System Functions 1. Receive & relay information throughout body 2. Monitor & respond to internal and external changes

 Brain  Spinal Cord  Nerves Cells are unique – called neurons Consists of:

 Central Nervous System (CNS) – brain & spinal cord  Peripheral Nervous System (PNS) – sensory & motor neurons that carry information to & from CNS. Two Major Divisions:

Nerve /Brain Facts  We can’t make new neurons  The brain is made up of 100 billion neurons  We make new nerve connections when we learn

Nerve/Brain Facts (cont.)  We use 100% of our brain  Nerve impulses can travel 395 feet per second

Bundles of nerve fibers

What are neurons?  Cells that carry electrical nerve impulses throughout body  3 parts

Anatomy of a Neuron  Dendrite: receives nerve impulse from other neurons & conducts them to cell body

Anatomy of a Neuron (cont.)  Axon: sends nerve impulse from cell body to other neurons & muscles.

Anatomy of a Neuron (cont.)  Myelin Sheath: membrane surrounding axon faster nerve conduction faster nerve conduction

Anatomy of a Neuron (cont.)  Cell Body: contains organelles mitochondria, nucleus, etc.mitochondria, nucleus, etc.

Neuron Dendrite Cell Body

1.Nerve Impulse occurs 2.Neurotransmitters are released in synapse 3.Muscle contracts or response to stimuli occurs How Neurons Work

 Nerve impulse (a.k.a. action potential) – is an electrical charge traveling the length of a neuron Touch, loud noise, smell, etc.Touch, loud noise, smell, etc. Steps of How Neurons Work:

 Impulse reaches end of axon, vesicles (small sacs) release Neurotransmitters: chemicals that carry impulses between neurons How Neurons Work

 Neurotransmitters cross the synapse and cause a response (ex. muscle to contract) How Neurons Work

Neurotransmitters  Serotonin & Dopamine “feel good” type of chemicals “feel good” type of chemicals

How Neurons Work  Neurons have a gap between them: synapse Gap between axon of 1 neuron & dendrite of another neuronGap between axon of 1 neuron & dendrite of another neuron

Types of Neurons 1.Sensory neurons 2.Motor neurons 3.Interneurons

1. Sensory Neurons  Carry impulses from skin and sensory organs to brain and spinal cord

2. Motor Neurons  Carry impulses from the brain and spinal cord to muscles or glands causing a response

 Receives impulse from sensory neurons & carries impulse to motor neurons 3. Interneurons

Problems due to Neurotransmitters Parkinson's Disease: dopamine producing neurons destroyed (lack of movement)Parkinson's Disease: dopamine producing neurons destroyed (lack of movement) Depression: deficit in serotonin &/or dopamineDepression: deficit in serotonin &/or dopamine Schizophrenia: high level of dopamineSchizophrenia: high level of dopamine

Epilepsy Seizures due to large numbers of impulses sent simultaneously Affects 1 out of every 200 people in U.S. & 50 million people worldwide

Multiple Sclerosis  Body attacks myelin sheath  Causes nerve impulses to short circuit

Studying The Brain  CAT Scan: used to locate tumors, damaged regions & blood clots  AKA CT Scan – computed axial tomography

Studying The Brain (cont.)  PET Scan: used to look at brain activity Positron emissions tomography

Studying The Brain (cont.)  MRI: used to look at brain tissue MRI of an individual with MS Magnetic resonance imaging

Central Nervous System:  Consists of brain and spinal cord

 Brain has 4 main parts: CerebrumCerebrum CerebellumCerebellum Brain stemBrain stem HypothalmusHypothalmus CNS continued:

 Cerebrum named by region: Frontal Lobe – judgment, impulsesFrontal Lobe – judgment, impulses Parietal Lobe – understand & process informationParietal Lobe – understand & process information Cerebrum:

Occipital Lobe – visually processOccipital Lobe – visually process Temporal Lobe – controls hearing & recognitionTemporal Lobe – controls hearing & recognition Cerebrum continued:

 Coordination & movement  Body movements, posture, muscle tone, & equilibrium Cerebellum:

 Controls vital life processes such as: RespirationRespiration SwallowingSwallowing DigestionDigestion Heart rateHeart rate Blood pressureBlood pressure Brain Stem:

 Emotions & instincts  Controls body temperature, thirst, hunger, hostility, & pain Hypothalamus: