CH. 2: Neuroscience Flashcards
What we will learn about the nervous system
- The organization of the human nervous system
- The components of the nervous system
- The functioning of the nervous system
- The role of hormones and neurotransmitters in behavior
- How the brain is studied
Phineas Gage
Phineas Gage’s traumatic accident allowed researchers to investigate the functions of the frontal lobe and its connections with emotion centers in the subcortical structures.
How Many Neurons Are in the Brain?
86 Billion! (Previous estimates were around 100 million)
Components of the Neuron
Cell body: Coordinates information-processing tasks and keeps the cell alive
Dendrite: Receives information from other neurons and relays it to the cell body
Axon: Transmits information to other neurons, muscles, or glands
Myelin sheath: Provides insulating layer of fatty material
Glial cells: Support cells found in the nervous system (makes up myelin sheath)
Synapse: Junction or region between the axon of one neuron and the dendrites or cell body of another
Axon> Synapse> Dendrite> Axon
Psychologist Donald Hebb’s “assembly theory”
Theory of how the brain achieves the feat of keeping neurons together, best summarized by the idea that “neurons that fire together wire together.” The idea is that neurons responding to the same stimulus connect preferentially to form “neuronal ensembles.”
The glial cells of Myelin also help keep the neurons physically together
Myelin and Nodes of Ranvier
Myelin is formed by a type of glial cell, and it wraps around a neuron’s axon to speed the movement of the action potential along the length of the axon. Breaks in the myelin sheath are called the nodes of Ranvier. The electric impulse jumps from node to node, thereby speeding the conduction of information down the axon. Myelin is white while grey matter is unmyelinated
Myelin
- Made up of Glial cells
- The glial cells help hold neurons in place
- Surface of brain is cell bodies and hence gray matter
- Inside is pinkish or white and myelinated axons
3 types of Neurons Specialized by Function
Sensory neurons, motor neurons, and interneurons
Sensory Neurons
- Receive information from the external world; convey this information to the brain via the spinal cord
- Receive signals for light, sound, touch, taste, and smell
Motor Neurons
- Carry signals from the spinal cord to the muscles to produce movement
- Often have long axons that reach to muscles at our extremities
Interneurons
- Connect sensory neurons, motor neurons, or other interneurons
Electrochemical Action
Communication of information within and between neurons proceeds in two stages: conduction and transmission
Conduction
Movement of electronic signal within neurons
Transmission
Movement of electrochemical signal from one neuron to another due to signaling across the synapse involving (chemical) neurotransmitters to the dendrites.
The action potential direction
a. In response to a signal, the soma end of the axon becomes depolarized.
b. The depolarization spreads down the axon. Meanwhile, the first part of the membrane repolarizes. Because Na* channels are inactivated and additional K* channels have opened, the membrane cannot depolarize again.
c. The action potential continues to travel down the axon.
Resting Potential
Balance of positively charged and negatively charged ions
Action Potential
All or none strength electrical impulse along axon to synapse
Refractory Period
Period of time until the nerve cell can fire again
Chemical Signaling: Transmission Between Neurons
Information is passed between neurons through chemicals called neurotransmitters.
Terminal buttons: Knoblike structures that branch out from an axon
Neurotransmitters: Chemicals that transmit information across the synapse to a receiving neuron’s dendrites
Receptors: Parts of the cell membrane that receive the neurotransmitter and initiate or prevent a new electric signal
Synaptic Transmission
(1) The action potential travels down the axon and (2) stimulates the release of neurotransmitters from vesicles.
(3) The neurotransmitters are released into the synapse, where they float to bind with receptor sites on a dendrite of a postsynaptic neuron, initiating a new action potential.
The neurotransmitters are cleared out of the synapse by (4) reuptake into the sending neuron, (5) being broken down by enzymes in the synapse, or (6) binding to autoreceptors on the sending neuron.
Acetylcholine (ACh)
- Enables muscle action, learning, and memory
- With Alzheimer’s disease, ACh-producing neurons deteriorate.
Dopamine
- Influences movement, learning, attention, and emotion
- Oversupply linked to schizophrenia. Undersupply linked to tremors and decreased mobility in Parkinson’s disease.
Serotonin
- Affects mood, hunger, sleep, and arousal
- Undersupply linked to depression. Some drugs that raise serotonin levels are used to treat depression.
Norepinephrine
- Helps control alertness and arousal
- Undersupply can depress mood.
GABA (gamma-aminobutyric acid)
- A major inhibitory neurotransmitter
- Undersupply linked to seizures, tremors, and insomnia.
Glutamate
- A major excitatory neurotransmitter; involved in memory
- Oversupply can overstimulate the brain, producing migraines or seizures (which is why some people avoid MSG, monosodium glutamate, in food).
Endorphins
- Neurotransmitters that influence the perception of pain or pleasure
- Oversupply with opiate drugs can suppress the body’s natural endorphin supply.
How Drugs Mimic Neurotransmitters
Drugs that affect the nervous system operate by increasing, interfering with, or mimicking neurotransmitters.
Agonists
Drugs that increase the action of a neurotransmitter
- Examples of full agonists are heroin, oxycodone, methadone, hydrocodone, morphine, opium and others.
Antagonists
Drugs that block the function of a neurotransmitter
- An antagonist is a drug that blocks opioids by attaching to the opioid receptors without activating them. Antagonists cause no opioid effect and block full agonist opioids. Examples are naltrexone and naloxone.
Nervous System
Nervous system –> Peripheral and Central (brain and spinal cord)
Peripheral –>
- Autonomic (conveys commands that control internal organs and glands)
- Somatic (conveys information into and out of the central nervous system; controls voluntary movements of skeletal muscles)
Autonomic –> Sympathetic (arousing) and Parasympathetic (calming)
Sympathetic Nervous System
- Dilates pupil
- Relaxes bronchi
- Accelerates heartbeat
- Inhibits digestive activity
- Stimulates glucose release
- Stimulates secretion of epinephrine/norepinephrine
- Relaxes bladder
- Stimulates ejaculation in male
Parasympathetic Nervous System
- Contracts pupil
- Constricts bronchi
- Slows heartbeat
- Stimulates digestive activity
- Stimulates gallbladder
- Contracts bladder
- Allows blood flow to sex organs
Vagus Nerve
- Connects brain to parasympathetic nervous system
- Main nerves of the parasympathetic system
160,000 nerve fibers
80,000 on each side of your neck - Involuntary but can be classically conditioned
- Also controls the immune system
Spinal Reflex: The Pain Withdrawal Reflex
Many actions of the central nervous system don’t require the brain’s input. For example, withdrawing from pain is a reflexive activity controlled by the spinal cord.
Painful sensations (such as the heat of fire) travel directly to the spinal cord via sensory neurons, which then issue an immediate command to motor neurons to retract the hand.
Four Main Regions of the Spinal Cord
- Cervical nerves
- Thoracic nerves
- Lumbar nerves
- Sacral nerves
Endocrine System
Glands that secrete hormones into the bloodstream.
Thyroid - Body temperature, heart rate
Pancreas - Digestion and regulates pineal gland controlling sleep and wake
Adrenal - Stress related responses
Sexual reproductive - ovaries and testes
Pituitary gland - Overall control
Hypothalamus - a region of brain releasing hormones to control the pituitary gland
Mass action vs Specialized function: Generally the brain is not specialized by hemisphere
Exceptions include:
Broca’s Area - Left hemisphere if right handed - Speech Production
Wernicke’s Area - Left hemisphere if right handed - Speech Comprehension
Brain Lateralization
Two hemispheres connected by the Corpus Callosum
Typically acts as a whole as long as the corpus callosum is operational as shown by split brain procedures (to resolve intractable epilepsy).
Split Brain experiments
SLIDE 32: https://docs.google.com/presentation/d/1fhsMFUUhqQevBDYPvizY36e6ibyphKXxVj9UKxpXEZw/edit#slide=id.geba474a15d_80_18
Structure of the Brain
There are three major divisions of the brain:
Hindbrain: Coordinates information coming into and out of the spinal cord; also controls the basic functions of life
Medulla, reticular formation, cerebellum, pons
Midbrain: Important for orientation and movement
Tectum, tegmentum
Forebrain: Highest level of brain; critical for complex cognitive, emotional, sensory, and motor functions
Cerebral cortex, subcortical structures
The Hindbrain
Brainstem: lower base which connects the spinal cord to the brain; is the oldest part of the brain responsible for automatic survival functions.
Medulla: controls heartbeat and breathing
Functions of the Cerebellum
SLIDE 36: https://docs.google.com/presentation/d/1fhsMFUUhqQevBDYPvizY36e6ibyphKXxVj9UKxpXEZw/edit#slide=id.ga02a28d162_0_6
The Midbrain and Forebrain
SLIDE 37: https://docs.google.com/presentation/d/1fhsMFUUhqQevBDYPvizY36e6ibyphKXxVj9UKxpXEZw/edit#slide=id.g5bd0554773_0_62
The Limbic System
Hypothalamus
Links brain and endocrine system; regulates hunger, thirst, sleep, and sexual behavior
Thalamus
Processes and integrates sensory information; relays sensory information to cerebral cortex
Amygdala
Involved in memory and emotion, especially fear and anger
Hippocampus
Involved in forming new memories
The Cerebral Cortex
The cortex has four lobes (in each hemisphere).
The cortex is the highest level of the brain.
Three functionally distinct areas
Association Areas of the Brain
Provides sense and meaning to inputs - Most developed areas of the brain
Mirror Neurons
Imitation, observation
Feature detectors
Shapes, movement detectors, auditory interpretation
Default Mode Network
Relaxed, daydreaming
Visual Imagery Network
The mind’s eye
Semantic Network
Language meaning
Visual Perception Network
Perception of visual stimuli
Brain Plasticity
The brain is plastic: Functions that were assigned to certain areas of the brain may be capable of being reassigned to other areas of the brain to accommodate changing input from the environment.
Greater use of a function may command greater space in the cortical map.
Physical exercise can benefit the strength and connections of synapses in the brain.
Forms: Synaptic, functional adaptation, neuronal creation and loss
Neuroplasticity: What is it?
Increased or changed synaptic connections
New neuron creation (neurogenesis) and /or loss (pruning)
Change in the function of brain structures
Gut Brain Communication
After the brain the gut contains the most neurons
The gut consists of the intestines, the esophagus, the pancreas, the liver, the gallbladder
Postnatal Neurogenesis
New neurons?
Hippocampus
Glial Cells - make up 1/2 of the brain mass
Studying the Brain’s Electrical Activity
- Study the link between brain structures and behavior through the recording of electrical activity in neurons.
- Electroencephalograph (EEG): Device used to record electrical activity in the brain
- Hubel and Wiesel: Inserted electrodes into the brains of anesthetized cats; made discovery of feature detectors by mapping visual cortex
Using Brain Imaging to Study Structure and to Watch the Brain in Action
- Neuroimaging techniques use advanced technology to create images of the living, healthy brain.
- Structural brain imaging shows underlying brain structure.
- CT scan, MRI
Functional brain imaging shows brain activity while someone engages in a cognitive or motor task.
- PET - Observe radioactivity in areas of the brain
- fMRI - Observe blood flow to areas of the brain
Insights from Functional Imaging
- Insights into the types of information processing that take place in specific areas of the brain
- Confirmation of theories derived over last century is possible
- Need to be cautious about how evidence from fMRI obtained
Transcranial Magnetic Stimulation
Scientists have studied the effects of brain damage for centuries.
- Brain damage may be related to particular patterns of behavior in people with brain injuries, but the relationship may not be causal.
Transcranial magnetic stimulation (TMS) methods can (ethically) mimic brain damage.
- Temporarily deactivates neurons in the cerebral cortex
- Can be combined with fMRI techniques
- Manipulation can provide causal explanations
Optogenetics
Directed light to control neurons
Neuro Core Concepts
Communication
Emergence
Evolution
Gene-Environment Interactions
Information Processing
Nervous System Functions
Plasticity
