The Neuron

Pathways to the Nervous System

The Neuron

• before birth

• Approximately upon birth

• 90% of your cells are glia cells (in CNS) and Schwann cells (in PNS)

• (fun fact: prenatal neurons develop at the rate of 250,000/minute!!)

Nerve fibers are long dendrites and axons bundled together. They are called nerves in the PNS and tracts in the CNS

Nerves that lead to the brain are also known as:

Nerves going from the brain are:

NeuronParts:

dendrites soma nucleus, nissl substance axon myelin sheath nodes of Ranvier

terminal feet terminal buttons

Chemicals contained in the terminal buttons are called neurotransmitters, which will leave:

The area between neurons is known as:

All-or-none law

• The all-or-none law states that when a neuron is stimulated, it must stimulated to:

Ways of Measuring the BrainElectroencephalograph

-EEG-Measures:

Used in sleep research, detects dreams and sleep disorders

Ways of Measuring the Brain

Lesioning

Intentional damage to brain cells:

Lesioning has taught us a lot about the functions of the brain

Ways to Measure the BrainCT-Computerized

Tomography

Horizontal slices:

Least expensive – widely used

Ways to Measure the BrainPositron Emission

Tomography (PET)

Radioactive tracer

Color coded map

Ways to Measure the BrainMagnetic Resonance

Imaging (MRI)

What it is:

Very expensive

Ways of Measuring the Brain

Electrical Stimulation of the Brain (ESB)

Sends a weak:

Stimulates areas of the brain to determine what effect the stimulation has

Discovered by Penfield, done:

Neurotransmitters

Acetylcholine-Ach

Involved in voluntary movements

Contributes to:

Lack of Ach –

Low levels of Ach – cells die

Acetylcholine

Hippocampus of the brain

Overabundance of Ach-

Curare-a poison that blocks the transmission of Ach, which will lead to intense spasms of the muscles, including heart –

Dopamine-DAControls voluntary musclesA monoamineLack of –

Too much –

Dopamine

Tardive Dyskenesia-a disease which can cause Parkinson’s-like tremors. This occurs when a person takes meds for:

Plays a major role in addiction as it is similar to adrenaline and controls:

Serotonin-SEHighly implicated in

, hence your SSRI’s (antidepressants)

Low levels of SE seemed to be linked to:

Involved in wakefulness and:

A Monoamine

Norepinephrine-NE

Low levels of NE have been associated with:

Cocaine and amphetamines may stimulate the activity of this neurotransmitter (may cause hallucinations)

A monoamine

Epinephrine

• Synthesized by the:

• Activates the sympathetic nervous system and puts the body:

Endorphins

Resemble opiates

Pain blockers

Gate control theory:

GABA

Low levels:

Antianxiety drugs:

Central and Peripheral Nervous Systems

• Central Nervous System –

– Consists of the:

Peripheral Nervous System

• Contains:

– Somatic Nervous System:

– Autonomic Nervous System:

• Sympathetic NS

Peripheral Nervous System

• Parasympathetic

– Rest and digest response

– Brings the system back to:

The Brain

• Did you know that the brain weighs only about 1 pound at birth?

• By one year of age, the brain will double in size and be almost 90% of its adult size

Lobes of the Brain• FRONTAL LOBE

• Located in front of the central sulcus.

• Concerned with:

•

         

                                           

Lobes of the Brain

• Frontal Lobe-

• On the left side is Broca’s area –

Motor Strip

Phineas Gage• After Gage had an

accident in which a metal pipe went through his brain, it was thought that he would not survive.

• However, he did – with interesting consequences

•

Lobes of the brain

• PARIETAL LOBE • Located behind the

central sulcus.

• Concerned with:

The Primary Somatosensory Cortex

  Neurons in the primary somatosensory are activated when the skin is touched. However, the body is NOT represented in the cortex in proportion to the amount of skin.

• A map of the human somatosensory cortex was drawn by Dr. Wilder Penfield in the 1950's.

• By observing the location on the brain that caused patients to feel sensations on different parts of their bodies, Dr. Penfield was able to draw a map of the brain

Lobes of the Brain

• TEMPORAL LOBE • Located below the

lateral fissure. • Concerned with:

Lobes of the Brain• Temporal Lobe –

• Behind the temporal lobe is the uncus –

• Left side of temporal lobe is Wernicke’s area -

Lobes of the Brain• OCCIPITAL LOBE

• Located at the back of the brain, behind the parietal lobe and temporal lobe.

• Concerned with:

The Lobes of the Brain

                              

.                                              

Medial View Sensory & Motor

Areas

The Brain

Brain Weight(gm) Species

6,000Elephant

            1,300-1,400 Adult Human     

97 Rhesus Monkey     

72 Dog     

30 Cat          

10 Rabbit     

2.2 Owl     

How does the human brain compare?

Parts of the Brain

• Cerebral cortex functions:

• Thought • Voluntary movement • Language • Reasoning • Perception

•

The Hindbrain

• Cerebellum

• Functions:

• Looks like a mini-brain

•

Cerebellum• Two peach-size mounds

of folded tissue at the base of the brain form the cerebellum.

• Damage to this area leads to:

• Some scientists have discovered:

The Hindbrain

• Medulla

• Control of:

– a.k.a. the medulla oblongata

The Hindbrain

• Pons– Located above the medulla– Connects midbrain with the:

– Controls:

– Contains sensory and motor tracts between the cortex and the medulla

– Involved in:

The Midbrain• The midbrain is

very small in humans

• Coordinates simple movements with sensory information

The Midbrain• Reticular formation (a.k.a.

Reticular activating system)

• Attention and arousal-

• If damaged, the person may:

• Involved in pain perception

The Forebrain• Thalamus

– Functions as a relay station – sends sensory information to:

– The only sensory information that does not travel through the thalamus is:

The Forebrain• Hypothalamus

Known for four F’s-

Although the pituitary gland is given credit for regulating the endocrine system, it is the hypothalamus that sends the message to:

The Forebrain• Hypothalamus

– Regulates:

– Controls your biological rhythms, so it is also involved with whether you are a morning person or an afternoon person

The Forebrain• Limbic system:

– Regulation of emotions-

– Also known for being involved with:

– Hippocampus, amygdala, septum, part of the thalamus and hypothalamus

The Forebrain

• HippocampusInvolved in memory and how we:

Removal of temporal lobe can result in:

The Forebrain• Hippocampus-

• Many memories are not stored there, however, the hippocampus sends information to different areas of the cerebral cortex for processing

The ForebrainAmygdala• Plays a role in aggression

and defensiveness

• When damaged:

• When stimulated:

The Forebrain• Septum

• Important pleasure center of the brain – mild stimulation of this area may result in intense pleasurable feelings, including intense sexual arousal

• Lesions to the septal area may result in:

• Stimulation results in:

Corpus Callosum• The brain has

identical parts in each hemisphere

• The corpus callosum connects:

• Often cut in patients with:

Cerebrum• Largest part of the brain

– Divided into two hemispheres – each hemisphere has identical parts:

– Separate by the-

– Divided into four lobes

Hemispheres of the Brain

• Are you right-handed or left-handed?

• About 90% of the population are right-handed - they prefer to use their right hand to write, eat and throw a ball ("right hand dominant.“)

• Most of the other 10% of the population is left-handed or "left hand dominant."

• There are few people who use each hand equally; they are "ambidextrous.”

BrainHemispheres

Marion Diamond• Demonstrated that an

enriched environment will increase cell weight and add to the number of dendrites on the neuron

• An impoverished environment decreases cell weight:

Environmental impact on the brain..

• From the time a baby is born (and possibly before) they are beginning the formation of trillions of neuronal connections via the environment

• Neurons will constantly grow, die, become stronger or weaker depending on the environment

Emotions and learning

• Positive emotions, however, can enhance learning

• When students laugh or have positive feelings towards learning they are more likely to learn

The Adolescent Brain

• “What were you thinking?”

• “Don’t you ever think before you act?”

• “When are you going to make better decisions?”

• “How many times do I have to say the same thing over and over again?” • Any of this sound familiar?

The Adolescent Brain

• The prefrontal cortex has not fully developed and the thinking, judging, planning portion of their brain is not functioning to its fullest capacity

The Adolescent Brain• New research indicates

that the adolescent brain has new cell growth and new neural connections

• This new growth and the pruning of neurons not in use help the brain develop emotional maturity

Diseases of the brain• Alzheimer’s Disease

– have gradual memory loss and difficulty with language and emotion

– while the disease starts out slowly, it progresses to the point that the person needs help eating, bathing and using the bathroom

Diseases of the brain

• Scans may help in the diagnosis

– CAT scans tend to help visualize brain shrinkage and enlarged ventricles

Diseases of the brain• Research has demonstrated that the more

neuronal connections one has, the more likely they are to lessen the effects of AD

• Therefore, one should keep active physically and mentally