The Brain

Neurons: The basic building block of the nervous system— a nerve cell.
- Neurons perform three basic tasks: receiving, carrying, and passing on electrochemical information.
- Neurons “fire”- send an impulse down their length- or they don’t.
- Reflex arc- how reflexes work- to the spinal cord and back
- Types:
  - Sensory Neurons — Carry messages to the spinal cord
  - Motor Neurons — Carry messages from the spinal cord
  - Interneurons — Over 90%, connect nerves, make up the brain and the spinal cord
- Parts of a Neuron:
  - Dendrites: Receive messages from other cells
  - Soma/Nucleus: The cell body, which maintains the health of the neuron
  - Axon: Passes messages away from the cell body to other neurons, muscles, or glands
  - Neural impulse: Electrical signal travelling down the axon
  - Myelin sheath: Covers the axon of some neurons and helps speed neural impulses (Important. If damaged, messages won’t go fast enough)
  - Terminal branches of axon: Form junctions with other cells
  - Terminal button: The end point that contains neurotransmitters
- The phases of communication within a neuron:
  - Action potential: The neural impulse created when a neuron fires. The impulse travels from the dendrites down to the axon to the terminal branches. This is considered the “on” condition.
  - Refractory period: The brief instant when a new action potential cannot be generated because the neuron is “recharging” after the previous action potential.
  - Resting potential: The state of a neuron when it’s “charged” but waiting for the next action potential to be generated
  - -70mV is the resting potential; -55 mV is the absolute threshold when the neuron is kicked off.
- All or None Principle:
  - The Principle that if a neuron fires, it will always fire at the same intensity
  - All action potentials are of the same strength
- Locks and Keys:
  - Neurotransmitter molecules have specific shapes
    - Receptor molecules have binding sites
    - When NT binds to receptor, ions enter
Neurotransmitters:
- A chemical messenger that travels across the synapse from one neuron to the next
- Can influence whether the second neuron will generate an action potential or not
- Kinds:
  - Agonist: Mimics the action of a NT
  - Antagonist: Opposes the action of a NT
  - Endorphins: Reduce pain and elevate pleasure/mood; act by either increasing or decreasing specific NT activity; mimic effects of opium based drugs like morphine (note, this is different from adrenaline)
  - Curare: Paralyzing poison. The prey is killed by arrows or blowgun darts that are dipped in curare, which leads to asphyxiation as the respiratory muscles of the hunted animal are unable to contract
  - Acetylcholine (ACh): Involved in memory and muscle movement— low in Alzheimers
  - Serotonin: Involved in mood and sleep— Depression
  - Dopamine: Involved in reward systems, movement, and motivation— too much = schizophrenia, too little = Parkinson’s
  - GABA (Gamma-aminobutyric acid): Inhibitory NT (like brakes on a car)— slows blood pressure and calms
  - Epinephrine NT (Adrenaline = hormone) and Norepinephrine: Involved in arousal, mood, and sympathetic nervous system activation; fight-or-flight response- Bipolar
  - Glutamate: An excitatory neurotransmitter that plays a crucial role in memory, learning, and cognition.
  - Substance P: A neurotransmitter that primarily functions as a transmitter of pain messaging in the nervous system
How we study the brain
- Stimulation: Electrically stimulating parts of the brain
- Accidents: That guy with the pole through his head
- Lesions: Destruction or growth in the brain affects particular functions within the brain
- EEG/ Electroencephalograph: Electrical activity (brain waves)
- CT or CAT Scan: X-Ray of the brain, either composite, axial, or tomographic
- MRI/ Magnetic resonance imaging: Uses a magnetic field to generate a picture
- PET / Positron Emission Tomography Scan: Shows brain activity— glucose levels in the brain— uses a slight amount of radiation
- fMRI/Functional Magnetic Resonance Imaging: Shows brain activity— MRI and PET scan together, no radiation
Main structures of the (old) brain:
- Hind: Blue. Mid: Red. Fore: Yellow.
  - Cerebrum: Voluntary movements, sensations, learning, remembering, thinking, emotion, consciousness
  - Hypothalamus: Control of hunger, thirst, temperature, and other visceral and bodily functions— instinctual drives
  - Amygdala: Emotional processing and memory
  - Hippocampus: Forming new memories
  - Pituitary Gland: The master gland of the endocrine system
  - Limbic system: Controls emotions and memory
  - Medulla (brainstem): Centers for control over breathing, swallowing, digestion, and heartbeat
  - Pons (brainstem): Sleep and wakefulness (circadian rhythm), dreams, facial expressions
  - Corpus Callosum: Band of fibers connecting the two hemispheres
  - Thalamus: Relay station to cortex for sensory information
  - Midbrain: Conduction and switching center
    - Reticular formation: Arousal, attention, movement, and reflexes
  - Cerebellum: Muscle tone, body balance, and coordination of skilled movement
  - Spinal cord: Conduction paths for motor and sensory impulses, and local reflexes (reflex arc)
- Cerebral Cortex:
  - Frontal Lobe: Planning, emotion and temperament, complex problem solving, personality, voluntary motor movement, and thought
  - Parietal lobes: Sensory perception, visual, and spatial relations
  - Occipital lobes: Receive and process visual information
  - Temporal lobes: Critical for hearing and balance, important in memory, smell, motivation, and emotion
  - Goal setting: Short-term objectives to maintain motivation and sustain focus
  - Arousal control: Taking deep, slow breaths to calm
  - Self-talk: Positive affirmations to boost confidence and reinforce goals
  - Mental rehearsal/visualization: Imagining successful performance scenarios to enhance preparedness and reduce anxiety
- Motor cortex:
  - The size of the body part indicates the amount of area on the motor cortex and the degree to which complex movements can be performed
- Somatosensory cortex:
  - The size of the body part indicates the amount of area on the somatosensory cortex and the degree of sensitivity to external stimulation
Language and the Brain:
- Aphasia: Partial or complete inability to articulate ideas or understand language because of brain injury or damage
- Broca’s area (left frontal): Speech production
- Wernicke’s area (Left temporal): Plays a role in understanding speech
Nervous system hierarchy:
- Nervous system
  - Central nervous system
    - Brain
    - Spinal Cord
  - Peripheral nervous system
    - Somatic system
    - Autonomic system
      - Sympathetic system (arousing)
      - Parasympathetic system (calming)
The Sympathetic and Parasympathetic divisions of the autonomic nervous system
- Sympathetic:
  - Dilates Pupil
  - Accelerates heartbeat
  - Inhibits digestion
  - Stimulates glucose release by the liver
  - Stimulates secretion of epinephrine and norepinephrine (fight-or-flight hormones)
  - Relaxes bladder
- Parasympathetic nervous system:
  - Contracts pupil
  - Slows heartbeat
  - Stimulates digestion
  - Stimulates gallbladder
  - Contracts bladder
Endocrine System:
- A second type of communication system in the body made up of a network of glands
  - Regulates hormones through glands
  - Adrenaline— Fight or Flight
  - Pineal Gland— Sleep and wake cycles
  - Pituitary gland— Many functions, including regulating growth, testosterone, estrogen, and stress responses
  - Thyroid Gland— Metabolism
  - Pancreas— Blood Sugar
  - Hormones: Adrenaline, Leptin, Ghrelin, Melatonin, Oxytocin
    - Adrenaline: Involved in the fight-or-flight response, increasing heart rate and energy availability.
    - Leptin: Regulates energy balance by inhibiting hunger, thus promoting satiety.
    - Ghrelin: Known as the "hunger hormone," it stimulates appetite and increases food intake.
    - Melatonin: Regulates sleep-wake cycles and circadian rhythms.
    - Oxytocin: Plays a key role in social bonding, reproduction, and childbirth.
Hemisphere Specialization:
- Left: Logic, analysis, sequencing, linear, mathematics, language, facts, think in words, words of songs, computation
- Right: Creativity, imagination, holistic thinking, intuition, arts (motor skills), rhythm, non-verbal, feelings, visualization, tune of songs, daydreaming
- Neuroplasticity: The ability of the brain to adapt, reorganize, and form new neural connections