neurons and nervous system unit

psych 1 exam two

what are neurons

• cells in the central nervous system

  • receive info from our sensory system

    • vision, audition olfaction, gustation and somatosensation

  • ~1100 billion neurons

  • brain & nervous system cells that transmit electrical signals

  • role of neurons: send and receive electrical signals from one neuron to the next

what are the three types of neurons

• sensory, motor and interneuron

role of sensory neurons

•  (afferent neurons) throughout your body relay messages to the brain; Input signal

role of motor neurons

•  (efferent neurons) in brain carry movement information from brain to body; Output signal

role of interneurons

• send information from one neuron to another, process info

role of cell body (soma)

• contains the nucleus and genetic information and directs protein synthesis

  • nucleus is located in the soma

role of dendrites

• part of neuron that extend outward from the soma and is the main input of the neuron

  • receives thousands of other neurons 

role of the axon

• part of the neuron that extends off the soma, splitting several times to connect with other neurons

  • main output of the neuron

  • cell transmits signals down length of axon

role of myelin sheath

•  insulator, speeds up signals to transmit faster

role of axon terminal

•  end of the neuron, sends signals to other neurons

define action potential

• Cells communicate via the action potential

• action potential: all-or-none signal that travels along the length of the axon

  • brief change in electrical charge

  • all-or-none = no such thing as a “big action potential” or “small action potential”

how does intensity of the stimulus affect the action potential

• action potentials follow the all-or-none principle—once the threshold is reached, the action potential always has the same size

• a stronger stimulus does not create a "larger" action potential

• stronger stimuli = more frequent action potentials & more neurons activated

• stronger stimuli do NOT increase action potential size or speed

steps of neural communication

1. Action potential arrives in axon terminal of pre-synaptic neuron (the neuron sending a signal)

2. Neurotransmitters (NTs) released into the synapse

   • neurotransmitters: chemicals that serve as messengers

   • more than 100 different types

   • two important ones:

     • dopamine: movement, motivation, emotion

     • serotonin: mood regulation

3. neurotransmitters bind to receptors on postsynaptic neuron

4. if there’s enough neurotransmitter, post-synaptic neuron fires an action potential

5. Neurotransmitter action stopped by enzymes or re-uptake

   • Enzymes destroy NTs

   • re-uptake: Take NTs into presynaptic cell for later use

agonist drug

• INCREASE effect of neurotransmitter

antagonists

• DECREASE effect of neurotransmitter

mimicking a neurotransmitter

• agonists (+)

causing more NTs to be released

•  agonists (+)

interfering with enzymes that break down NTs

•  agonists (+)

preventing NT re-uptake

•  agonists (+)

preventing release of NTs

• antagonists (-)

blocking postsynaptic receptors

• antagonists (-)

destroying NTs in the synapse

• antagonists (-)

what is the central nervous system

• brain and spinal cord

  • The brain controls how we think, learn, move, and feel. 

  • The spinal cord carries messages back and forth between the brain and the nerves that run throughout the body

the peripheral nervous system

• everything else!

  • sensory

  • motor

    • somatic 

    • autonomic nervous system

• a network of nerves that runs throughout the head, neck, and body

basic role of brainstem

• basic life support (breathing, heart rate, blood pressure)

basic role of thalamus

•  relay station / switchboard (e.g., sensory information goes from eyes, skin, etc. to thalamus and then rest of brain)

basic role of spinal cord

• Transmits information to and from the brain, organizes rhythmic skeletal muscle activity, reflexes 

basic role of cerebellum

• Means “little brain”

• Helps control complex motor movements, muscle memory

• among many other things (we’re still learning more!)

basic role of limbic system

• “Limbic” = “border”

• Separates evolutionarily old part of brain (brainstem, thalamus) from newer part (cortex)

basic role of hippocampus

• part of limbic system

• memory and navigation

basic role of amydala

• part of limbic system

• emotions

  • especially fear

basic role of frontal lobe

• planning, personality, judgment decision making

basic role of parietal lobe

• attention, sense of touch, spatial sense

basic role of occipital lobe

• visual processing

basic role of temporal lobe

hearing memory

explain how the brain shows evolutionary organization

• Evolutionary organization: Structures for basic life function are most protected

• Differ less from other animals (human and rodent brainstem pretty similar)

• Brainstem (basic life support)

• Cerebral cortex: more complex abilities

• Newer evolutionarily

• Frontal lobe shows most difference with other species

• myelinated latest compared to other brain regions (reminder: myelination speeds up action potentials!)

  • finishes myelinating in early adulthood

  • Prioritizing essential functions

  • May explain improved decision making into adulthood

role of fusiform gyrus (FFG)

• Base of temporal lobe

• area of FFG particularly important for recognizing faces

• evidence

  • neuroimaging: shows particular activation for faces vs non-faces (e.g. houses, hands, objects, etc.)

  • damage to FFG associated with prosopagnosia

• main role: Facial recognition (FFA) & visual object recognition.

• also involved in: Reading, expertise recognition, and social processing

• damage can cause: Face blindness, object recognition issues, and reading difficulties

potential causes and symptoms of prosopagnosia

• Impaired face processing (sometimes called “face blindness”)

• can be acquired or congenital (present at birth)

• can lead to social anxiety (might not recognize friend)

• rely on other cues (gait, voice, posture)

cause and symptoms of capgras symptoms

• irrational belief that someone has been replaced by an impostor

  • refuse to talk with them

  • obsession with imposter

• intact FFG, intact amygdala...but impaired connection between FFG and amygdala

• connections between auditory cortex and amygdala are intact, so patients recognize people from their voices

which hemisphere is specialized for language production

• left hemisphere = Dominant for language production (Broca’s area) and comprehension (Wernicke’s area).

• right hemisphere = Supports emotional and contextual aspects of language.

• damage to the left hemisphere can cause speech and language impairments (aphasia)

split brain patients have damage to which area

• the corpus callosum

  • corpus callosum cut to treat epilepsy

• visual information on the left can reach right visual cortex (by crossing optic chasm)...but can’t cross corpus callosum to other hemisphere

claims and evidence to support them?

Claim 1: The brain shows evolutionary organization

• Brain organization reflects evolution, with older structures handling survival and newer ones enabling higher thought.

• Brainstem & limbic system (older) control basic life functions and emotions.

• Neocortex (newer) allows advanced reasoning, social behavior, and consciousness.

Claim 2: Specific functions are achieved in specific regions, but there is no one-to-one mapping!

• FFG: prosopagnosia and capgras

• The brain is specialized, but not rigidly mapped.

• Functions emerge from networks of brain regions working together.

• Plasticity allows for adaptation and redundancy.

Claim 3: Information can be encoded into the brain spatially

• The brain encodes information spatially, assigning specific areas to different types of data.

• The hippocampus encodes spatial navigation.

• The sensory and motor cortices use topographic maps.

• The visual cortex organizes information based on retinal input.

• The parietal lobe supports spatial working memory