Forms a communication and coordination network throughout an animal ’s body.
Are nerve cells specialized for carrying electrical signals from one part of the body to another.
Organization of Nervous Systems
The nervous systems of most animals have 2 main divisions:
The central nervous system (CNS)
Consists of the brain and, in vertebrates , the spinal cord .
The peripheral nervous system (PNS)
Is made up mostly of nerves that carry signals into and out of the CNS .
A nerve is a communication line made from cable-like bundles of neuron fibers .
Central Nervous System Brain Spinal Cord Peripheral Nervous System Peripheral Nerve
The 3 interconnected functions of the nervous system are carried out by 3 types of neurons:
Convey sensory input.
Perform integration, the interpretation of the sensory signals.
Carry out motor input.
You hit the ball
Why are athletes so good at what they are doing? Researchers found that the brain of athletes is “quieter” than non-athletes when asked to perform a task. This suggests that their brain would be more efficient , and need less neurons to perform a task. Some neurons strenghten their connections to other neurons and weakens connections to others. (ex: soccer players and screen) Practice also changes the brain Athletes can analyze a situation and make a decision in a split second.
NEURONS The Functional units of the Nervous System
Vary widely in shape but share some common features:
The cell body houses the nucleus and other organelles.
2 types of extensions project from the cell body:
DENTRITES receive incoming messages from other cells and convey the information toward the cell body.
The AXON conducts signals toward another neuron or an effector.
5 AXON : Transmits the action potential. 2 DENDRITES: Receive signals from other neurons. 4 Action potential starts here. 1 Synaptic terminals: Bring signals from other neurons. 3 CELL BODY Integrates signals; coordinates metabolic activities. 6 Myelin: Insulates axon, speeds conduction. 8 DENDRITES (of other neurons) 7 Synaptic terminals: Transmit signals to other neurons.
According to scientists: DOPAMINE . It is thought to be the master molecule of addiction.
what is the master molecule of addiction?
where is it produced?
It is made in the brain and affects primitive parts of the brain Based on Time , May 5, 1997
After being released into the synapse, dopamine binds to receptors on the next neuron
Dopamine is then reabsorbed by the Synapse
Dopamine is reabsorbed by the Synapse
It can be stored in the vesicle or broken down by an enzyme called M ono A mine O xidase ( MAO )
Cocaine blocks the normal absorption of dopamine.
Dopamine accumulates in the synapse
It keeps stimulating the receiver cell.
Amphetamines stimulate excess release of dopamine
Overwhelm the processes of reuptake and enzyme breakdown.
Nicotine stimulates the release of dopamine, while another substance in cigarette smoke blocks the action of MAO. How Drug Affect Dopamine Levels Based on Time , May 5, 1997
When a cell has been exposed to a chemical signal for a long time, it tends to get used to it and looses its sensibility to the stimulus. (ex: sitting on a chair). Drug Addiction: If a cell is exposed to high levels of neurotransmitter, it will adapt by having less receptors (homeostasis)
Physiology of Addiction
Drug amount of dopamine in the synapses
Increased dopamine results in feelings of pleasure
Nervous system responds by the number of dopamine receptor sites.
When a cell has been exposed to a chemical signal for a long time, it tends to get used to it and looses its sensibility to the stimulus (ex: sitting on a chair). Homeostasis
Addict must take more drug to produce the same “high”
“ So while addicts begin by taking drugs to feel high, they end up taking them in order not to feel low.”
Do you know a good addiction?
Exercise, such as cardiovascular exercise, releases a neurotransmitter called Endorphins (as well as serotonin, dopamine)
Endorphins function as the body natural pain killer.
Exercise correlates with good mental health as people age
The Human Nervous System
the central nervous system (CNS)
a peripheral nervous system (PNS).
The Central Nervous System: CNS is made up of the spinal cord and the brain
The spinal cord acts as the central communication conduit between the brain and the rest of the body.
The brain is the master control center of the nervous system.
Body temperature, water balance, hunger and thirst, sleep
manufactures hormones and controls the pituitary gland (Link between nervous and endocrine system)
sensory relay center
Receives incoming information and sends it to appropriate area
Memory, emotional responses
3. The cerebellum
Receives both sensory and motor input
Integrates information and sends impulses to skeletal muscle s by way of the brain stem
Can compare actual movements with intended movements
Functions to assure smooth, coordinated motor movements
4. The Brain Stem The most ancient, sometimes called the Reptilian Brain
The Brain Stem
Relay center for tracts passing between cerebrum and cerebellum
Control center for heartbeat, breathing, blood pressure, swallowing, coughing, vomiting
Contains bundles of axons traveling between the cerebellum and the rest of the CNS
DISORDERS OF THE BRAIN
a bit of history
New experiment on brain damaged patient
Mad Cow Disease
1. The case of Phineas Gage
Phineas Gage was the 1st patient from whom we learned about the link between personality and decision making and the function of the front parts of the brain (frontal lobes) . In 1848, a 3 foot steel rod was blown through his head by an explosion. He survived but his personality changed. He became rude, impatient, fitful. He died at 37 after experiencing severe seizures.
2. Recent findings More recently, doctors were able to communicate with a brain-injured patient. They could read is thoughts using a scanner.
3. Alzheimer Disease (AD)
Most common cause of dementia
Signs may appear before 50, usually seen in people past 65
Loss of memory (of recent events) is an early symptom
Abnormal neurons especially in the hippocampus and amygdala
Plaques : abnormal clusters of protein fragments, build up between nerve cells.
Neurofibrillary tangles found in dead or dying neurons
Several genes have been identified that predispose a person to AD
No prevention or cure
Alzheimer Disease Presence of plaques in different regions of the brain from an Alzheimer patient.
Gradual loss of motor control
Typically begins between 50 and 60 years of age
Later characteristics include tremors and
muscle rigidity, speaking may be difficult
Caused by a degeneration of dopamine producing neurons in basal nuclei
Dopamine (as a drug) cannot be administered because it cannot cross the blood-brain barrier
L-dopa is a drug that the body can convert to dopamine, at least for a while
Pesticide exposure found to increase risk of Parkinson's disease (UCLA research)
4. Parkinson Disease (PD)
Most common neurological disease that afflicts young adults
Affects the myelin sheath of white matter in the brain
5. Multiple Sclerosis (MS)
Symptoms include: Fatigue, limb weakness, vision problems, tingling or numbness
MS can take several forms (mild to severe)
No treatment is available, but the progression can be slowed
A disruption to the blood supply in the brain
Symptoms depend on the amount and area of the brain tissue that is affected
Factors such as age and race influence the likelihood of having a stroke
An infection of the meninges that surround the brain and spinal cord
Caused by bacteria or viruses
Infection may spread into the brain tissue
A diagnoses is usually confirmed by sampling cerebrospinal fluid
A vaccine is available for protection against some types of the disease
Caused by Prions (infectious proteins)
Replicate and accumulate in brain tissue
No treatment available
8. Mad Cow Disease
The Peripheral Nervous System The vertebrate peripheral nervous system is divided into 2 components:
1. The somatic nervous system
Carries signals to and from skeletal muscles , mainly in response to external stimuli. Serves skin
Voluntary as unvoluntary movements
2. The autonomic nervous system
Regulates the internal environment by controlling smooth and cardiac muscles and the organs and glands of the digestive, cardiovascular, excretory, and endocrine systems.
The parasympathetic division primes the body for digesting food and resting.
The sympathetic division prepares the body for intense, energy-consuming activities “Flight or fight”
Disorders of the Spinal Cord
Spinal cord injuries may stop impulses from traveling along neurons in the spinal cord.
This can result in paralysis of the areas located below the site of injury
Amyotrophic Lateral Sclerosis (ALS)
Also called Lou Gehrig ’s disease
Steven Hawking has ALS
Affects the motor nerves of the spinal cord
Incurable, people usually die within five years of diagnosis
There may be multiple causes of nerve cell death
Disorders of the Peripheral Nerves
Guillain-Barre Syndrome (GBS)
Demyelination of peripheral nerve axons
Hypothesized to result from abnormal immune reactions to one of several types of infections
Muscle weakness begins in the lower limbs then ascends to the upper limbs