Neuroscience.ppt
Transcript of Neuroscience.ppt
Neurophysiology, Neuroanatomy
The brain is a combination of two types of cells, glial cells and neurons
The brain consists of 100 billion neurons and 1012 total cells
Cells in the brain that communicate with each other
Neurons are “born” early in life Limited regeneration
Provide support for neurons◦ Structure support◦ Metabolic and nutritional support
Can replace themselves Serve to clean up the brain, removes dead
tissue and foreign objects Play a large role in neural development May even be communicating with neurons Role is expanding with new research
Pyramidal neuron Purkinje neuron
Neurons communicate in two ways Electrical signal: within a neuron Chemical signal: between neurons Electrical signal is sent from one part of
the neuron to the other: The signal travels from the dendrite through the cell body to the axon◦ Dendrites receive the signal from another
neuron◦ Axons send the signal to other neurons
Chemical signal is sent from the axon of one neuron to the dendrite of another neuron
Neurons contain many ions and are charged
A- are large protein ions that always stay inside the cell
K+ is potassium. At rest it is mostly inside the cell
Cl- is chloride. It exists both inside and outside the cell
Na+ is sodium. It exists primarily outside the cell
When the cell is at rest (i.e., not doing anything), it has a charge of -70 mV. This is called the resting potential.
Because of the cell properties, many forces are acting on the cell.
1. Diffusion - substances tend to move from areas of high concentration to areas of low concentration.
2. Like charges repel each other and opposite charges attract
Charges stay the way they are because of the cell membrane. It is selectively permeable. It does this by ion channels.
Normally, membrane closes Na+ channels However, if the membrane is given an
electrical charge, it causes the membrane to lose some permeability
This opens the sodium channels If this electrical charge is large enough, the
flood gates will open Change in charge is potentiated down the
length of the neuron This wave of charge is called the action
potential
Once sodium has rushed in, the cell quickly regains its composure
Active process in which sodium is removed from the cell
Sodium is exchanged for potassium Requires metabolic activity Returns charge inside cell to -70 mV Refractory period
When the action potential reaches the terminal button, it causes a release of chemicals called neurotransmitters
These neurotransmitters are dumped into the synapse, the space between the axon of one neuron and the dendrite of another
Neurotransmitters come into contact with membrane of the other neuron
Receptors on the dendrite detect the neurotransmitter
NT binds to the receptor This causes a temporary change in the
membrane, allowing a little sodium inside the cell
This small charge is called the graded potential
This is passed on to the axon and it summates
When the sum of the potentials reaches the base of the axon, a sufficient charge may be present to cause an action potential.
Myelin – a layer of proteins that are wrapped around the axon.
Two functions: to protect the axon, and to speed up transmission
Without myelin, neural transmission is inefficient
Multiple Sclerosis – an autoimmune disorder in which the myelin is destroyed.◦ Fatigue, pain, motor disorders, cognitive
disorders, etc.
After the NT is initially released, the chemical must be removed
This is done in a couple of different ways◦ Biochemical breakdown of the NT◦ Reuptake: NT is pulled back into the presynaptic
button and packaged to be released again
Excitatory◦ Glutamate◦ Acetylcholine
Inhibitory – What does this mean?◦ GABA◦ Norepinephrine
Both◦ Dopamine◦ Serotonin
Psychopharmacology- the study of how drugs affect behavior
Nearly all drugs work by affecting neurotransmitter release
Prozac is an example of a SSRI – a selective serotonin reuptake inhibitor
Alcohol◦ Activates GABA receptors
Nicotine◦ Activates acetylcholine receptors◦ Changes overall number of ACH receptors
Cocaine / crack◦ Blocks reuptake of dopamine◦ Stimulates release of dopamine◦ Anesthetic effect on cells
Amphetamine / Methamphetamine◦ Similar to cocaine with no anesthetic effect
Heroin◦ Activates opiate receptors
Marijuana◦ Activates cannabinoid receptors (similar to opiate)
Ecstasy (MDMA)◦ Selectively destroys neurons that release
serotonin◦ Serotonin is dumped out when the cell dies
Central Nervous System: Includes Brain and Spinal Cord
Peripheral Nervous System: All other neural tissue. Specifically, the periphery. This includes muscles, the skin, and even the organs
PNS broken down into two parts1. Somatic nervous system: nerve fibers that
send sensory information to the central nervous system AND motor nerve fibers that project to skeletal muscle.
2. Autonomic nervous system – Controls the "insides" (the "viscera") of our body, like the heart, stomach and intestines - functions in an involuntary, reflexive manner - does things like constrict blood vessels, dilate pupils, and even makes our heart beat fast on a roller coaster, etc.-Has two components
- A. Sympathetic nervous system: - B. Parasympathetic nervous system
Sympathetic NS- Regulates “Fight or Flight”◦ Prepares the body during stressful situations ◦ Increases heart beat, blood pressure, speeds
breathing, slows digestive function Parasympathetic NS – Regulates "rest and
digest" ◦ Keeps the body running calmly◦ Shuts down the sympathetic NS when the
situation becomes less stressful
Spinal Cord: Two types of material, white matter (Axons) and grey matter (cell bodies)
Spinal cord relays sensory and motor information to and from the brain
Controls reflexes◦ Ex. Knee jerk reflex, pain reflex
Afferent neurons: neurons that send their signal TOWARDS the spinal cord
Efferent neurons: neurons that send their signal AWAY from the spinal cord
Reflex involves two neurons, one afferent and one efferent
Reflexive action takes place before it is sent to the brain
Allows for extremely efficient processing
3 major divisions1. Hindbrain:
Cerebellum; Pons; Medulla
2. Forebrain: Cortex, amygdala, hippocampus, thalamus, hypothalamus
3. Midbrain
Cerebellum: Extremely large area, millions of neurons◦ Responsible for coordination of movement◦ Plays a role in learning
Pons◦ Important for sleep and especially dreaming
Medulla◦ Controls all vital functions of the body including
breathing and heart rate
Thalamus◦ Primary relay station of the brain◦ Almost all sensory information passes through
before going elsewhere Hypothalamus
◦ Regulates autonomic nervous system◦ Regulates hormones, “4 F’s”; Feeding, Fighting,
Fleeing, and sexual behavior Amygdala
◦ Responsible for many aspects of emotion◦ Emotional learning
Hippocampus◦ Especially important for learning and memory◦ Resolving conflict
Cerebral Cortex◦ Does just about everything◦ Many think that the cortex is what makes
humans the way they are◦ Cortex is broken up into 4 lobes:
Frontal lobe: the front of the brain Temporal lobe: side, the temples Parietal lobe: kinda middle portion Occipital Lobe: very back
Frontal lobe◦ Important for planning◦ Thinking / decision making◦ Primary motor cortex: Generation of movement◦ Broca’s area: Production of Speech
Temporal lobe◦ Audition◦ Wernicke’s area: Language comprehension
Parietal lobe◦ Somatosensory function (touch, vibration, pain)◦ Combination of all senses with vision
Occipital lobe◦ Vision: Primary visual cortex
Brain is actually two different halves. It is split down the middle, with the right and left side being very similar to the other
The two hemispheres are connected by the corpus callosum: a bunch of axons
Each side of the brain controls the opposite side of the body. ◦ Ex. Moving right arm controlled by the left side of
the brain. Systematic differences in right vs. left. Most language and music on the left.
◦ Somewhat different for left-handed people The right hemisphere more involved with
visual imagery and creativity.
Sometimes the corpus callosum of a person is cut. It is often surgically cut in patients with severe epilepsy.
Allows for the study of the role of each hemisphere
Experiments have found crazy strange results
Many techniques can be used to study the brain of animals
Lesioning of the brain◦ Electrical lesions- electricity is passed through an
electrode until neurons die◦ Chemical lesions- inject chemicals like acid to kill
neurons Injection of drugs
In Vitro analysis: “In the Lab” – brain tissue is removed, isolated, and studied on its own. Individual neurons can be studied
In Vivo analysis: “In the Living” – the brain is studied in an intact animal
EEG: electroencephalogram – electrodes are placed on the scalp. ◦ It records the electrical activity of neurons.◦ Problem: It records from thousands of neurons at
a time; not very precise
“CAT” scan: Computerized tomography◦ Computer enhanced 3-D X-Rays◦ Not much resolution, still life
MRI: Magnetic resonance imaging – uses magnetic fields to get brain scans◦ Just get a picture
PET scan: Positron Emission Tomography– patients are injected with radioactive glucose.
The scanner tracks where the glucose moves to. This is used as an indicator of neural activity.
- Has problems: very expensive, resolution is fairly low.
Functional MRI (fMRI) – Registers changes in the metabolism of cells◦ Get 3-D picture of real time brain activity◦ Very expensive