Lecture 2.12 - SNB II; Lobes, AMPA/NDMDA, Long term potentiation.,Thalamus

• A = No fluid should be in A

• B = Blood, not CSF, since veins

• C = CORRECT

  • Includes granulosa

3 Fundamnetal dividison of the vertebrate brain

1. Hindbrain

   1. Reflexes, non conscious movements (heartbeat)

2. Midbrain

   1. Coordination

3. Forebrain

   1. Cerebrum

      1. Decision making, senses

   2. Hypothalamus, thalamus, diencephalon

• Brain development starts early

Same major brain structures found in most vertebrates

• Same structures, but could have different shapes, sizes, etc

Brain chart - Parts and Functions summary slide

• Different parts of the brain have specific functions

Hindbrain

• Supports basic functions

• Contains:

  • Medulla oblongata

    • Breathing, heart rate, blood pressure

    • Autonomic homeostasis

  • Pons

    • Communicator between medulla, cererellum, and cerebrum

    • Sleepy cycles

  • Cerebellum

    • Muscle movement coordination

      • Damage - loss of balance, coordination, language control, attention, sometimes emotion

Forebrain

• Frontal lobe

  • Anything in front of Central Sulcus

  • Voluntary control of movement

    • Thinking, memory, reasoning, self control

• Parietal lobe

  • Directly behind frontal lobe / central sulcus

  • Knowing where you are in space (proprioception), receiving and understanding senses

• Occipital lobe

  • At the very back

  • Vision

• Temporal lobe

  • Both sides

  • Language, hearing, memory encoding

Cerebrum cross section

• Split in half - 2 hemispheres, right and left

• White matter in middle = Corpus Callosum

  • Contralateral senses - lots of crossover at corpus callosum

Functional Map of Brain

• Lesioning - touch/destroy/electrical impulse/brain surgery - parts of brain

Motor areas of cerebrum - Primary motor cortex

• Primary motor cortex

  • Controls voluntary movements of skeletal muscle

    • Stimulation of different regions of PMC leads to movement

    • Damage to PMC leads to paralysis or loss of voluntary movements but reflex remain

    • Damage to PMC usually results in permanent loss of these movements

  • In Frontal Lobe

Motor areas of cerebrum - Premotor Cortex

• Coordinates movements of groups muscles

  • PMC causes movements, PC controls them

• Damage

  • Loss of skill

  • Can be relearned

• In Frontal Lobe

Sensory areas of cerebrum - Somatosensory cortex

• Behind central sulcus

• Primary input from sensory receptors in skin and muscle

  • Touch information from skin and muscles

    • Pain, temperature, vibration, proprioception

      • Not eyes, ears, taste

• Damage leads to loss of sensation

• In Parietal Lobe

Sensory areas of cerebrum - Somatosensory association area

• Adjacent to primary somatosensory cortex

• Interpretation of sensations

  • Integrating sensations with memory

• Damage:

  • Loss of ID of sensations

• In Parietal Lobe

Visual areas of the cerebrum - Occipital lobe

• Primary visual cortex

  • Receives input

    • Primary input from optic tracts

• Visual association area

  • Makes sense of what is seen

Temporal lobe parts

• Wernicke’s area - speech comprehension

• Broca’s area - speech production

• Olfactory cortex - sense of smell

• Auditory cortex

• Limbic association areas - emotions, memory, motivation

Motor and Sensory Homunculus - on both sides of brain

• Distribution of amount of brain dedicated to certain movements/senses

  • Vary based on importance - more area on brain = more important

    • Ex: lots dedicated to face and fingers, little to arms and hips

• Motor homunculus

• Sensory homunculus

Limbic system (lizard brain)

• Inside the brain

  • Cingulate gyrus

    • Regulating emotions and pain

  • Fornix

    • Connector between portions of limbic system

    • Might have relation to episodic/short-term memory

  • Thalamus

    • Relay station - area that connects sensory organs to somatosensory organs

    • Receives senses, filters it, sends it out to area in brain for interpretation

    • All motor and sensory signals (except smell) pass through this structure

  • Hippocampus

    • Memory

  • Amygdala

    • Fear, aggression, emotions

  • Hypothalamus

    • Hormones

  • Olfactory bulb

    • Sense of smells

Diecephalon structures - Hypo/thalamus

• Thalamus

  • Filters/sorts inputs, routes information

• Hypothalamus

  • Homeostatic functions (negative feedback)

  • Regulates Pituitary gland

  • Hypothalamus → Pituitary → Other glands → Body

    • Hypothalamus receives input - body states (temperature, blood glucose, …) or brain states (amygdala - fear, stress ; other emotional state…)

    • Hypothalamus sends output to pituitary gland

    • Based on particular input, pituitary gland releases hormones

Hippocampus - memory

• Not very big in humans

• Long term potentiation - long term changes in memory = Synaptic plasticity

  • Causes long-lasting increases in signal transmission between neurons

  • Occurs at dendritic spine synapses of hippocampal neurons

  • Mechanism for tracking repetitive activity (salient stimuli)

Long-term potentiation

• LTP = Repeated stimulus over and over

• GRADED potentials, not action potentials

• LTP vs Low-frequency stimulation

  • LTP = bigger graded potentials = more likely to have an action potential

• More receptors

LOW FREQUENCY - Activity-dependent changes in dendritic spine synapses

• Pre-synaptic cells NT = usually glutamate

  • NT for AMPA receptor and NMDA receptor

• AMPA

  • Ligand-gated sodium channel

    • Receives glutamate, opens, allows Na+ in, Depolarization

    • AP more likely to occur

• NDMDA

  • Ligand-gated, Receives Glutamate

    • But Mg2+ clogs pores of receptor, doesn’t allow Ca2+ to pass through in LOW FREQUENCY

HIGH FREQUENCY - Activity-dependent changes in dendritic spine synapses

• AMPA

  • Still receives ligand (glutamate), opens, allows Na+ in, greater Depolarization

  • Greater depolarization ejects Mg2+ from the NMDA receptor

• NMDA

  • No more Mg2+ blocking

  • Ligand once again binds to receptor

  • No Mg2+ present this time, so Ca2+ can pass through

  • Ca2+ affects CAM-MK2 → phosphorylates AMPA receptor, opening it more (more Na+ in, more depolarization)

    • CAM-MK2 → leads to more active AMPA receptors and more AMPA insertion

  • PKC exhibits paracrine signaling, causing pre-synaptic neuron to release more glutamate = more +

• More Na+ enters which causes Ca2+ enters = more positive = POSITIVE FEEDBACK

• AMPA phosphorylated = More + = more AMPA receptors = More + = POSITIVE FEEDBACK

• Thought to be involved in memory production

Hypothalamus

• Helps maintain ion and water balance

• Regulates body temp

  • Thyroid - metabolism

• Regulates food intake

• Involved in the stress response

  • HPA (hypothalamus, pituitary, adrenal) axis

• Helps maintain ion and water balance

• Regulates circadian rhythms

Circadian rhythms

• Daily behavioral and physiological cycling and adaption to environmental cues

  • Environmental cue - usually Sun

  • Leads to input pathway

  • Behavioral rhythms

    • Persist in the absence of environmental cues

• What are controlled by circadian rhythm?

  • Cortisol levels

  • Blood pressure

  • Body temperature

  • Reaction time

  • Blod pressure