Behavioral Neuroscience Midterm #1

Anterior, Rostral

Forehead for the brain and upwards for the spinal cord (human), towards the beak /snout (rat)

Posterior, Caudal

Back side of the brain and downwards for the spinal cord (human), towards the tail (animal)

Dorsal, Superior

Top/upwards of the brain and back of the neck for the spinal cord (human), Back side facing the sky (animal),

Ventral, inferior

Downwards for the brain and throatside for the spinal cord (human), Belly side facing the ground (animal),

Central Nervous System Components

Brain (Cerebrum, cerebellum, brain stem) and spinal cord

Peripheral Nervous System Components

Nerves (Spinal and cranial except for the olfactory and optic nerve)

Brain (CNS)

Cerebrum: Sensation, cognition, and voluntary movement

Cerebellum: Movement control center — balance, posture, coordination, and motor learning

Brain stem: Vital functions (heart rate, respiration), reflexes and relay station

Spinal cord (CNS)

Carries information from the brain to skin, joints, muscles, and vice versa

Nerves (PNS)

Nerves: Receive sensory input and control motor output

Cranial nerces: Nerves of the head and neck

Spinal nerves: nerves of the extremities (neck, arms, torso, legs)

Peripheral nerves system: Function

Somatic nervous system: carries sensory information from the skin and muscles; innervates the skin, joints, and skeletal muscles; voluntary control (walking, moving, etc.)

Autonomic (visceral) nervous system: Innervates the organs, blood vessels, and glands; involuntary control; regulates homeostasis

Autonomic nervous system (PNS)

Sympathetic: Fight or flight (energy mobilization)

Parasympathetic: Rest and digest (maintaining energy balance)

Unilateral

One side (e.g. one limb)

Bilateral

Two sides (e.g. two legs or two arms)

Ipsilateral

Same side of the body (e.g. left arm and left leg)

Contralateral

Opposite Side of Body (e.g right arm and left leg)

Medial

Closer to the middle of the body

Lateral

Moving away from the middle of the body

Coronal plane

A slice that separates the front from the back (of the brain)

Horizontal, axial, transverse

A slice that takes off the top (of the brain; i.e. a birds eye view)

Sagittal/Midsagittal

A slice that separates left and right, or cuts right in half

Afferent

Receives (sensory information)

Efferent

Sends out (motor information)

Meninges

Layers of protection around the brain

1. Dura mater: Tough outer layer

2. Arachnoid Mater: Middle layer

a. Subarachnoid space: between the arachnoid mater and pia mater ( filled with cerebrospinal fluid

3. Pia mater: Innermost layer that closely adheres to the brain (follows the gyri and sulci)

Gyri and Sulci (gyrus and sulcus)

Gyri: Bumps or ridges on the brain

Sulci: Grooves or folds in the brain

Lobes of the Cerebrum

Frontal lobe: decision-making, problem-solving, planning, reasoning, speech production, voluntary motor control

Parietal lobe: multimodal sensory integration, especially combining sensory information with spatial information

Temporal lobe: auditory processing, long-term memory, speech comprehension, emotional regulation

Occipital lobe: Vision

Insula (not an official lobe): emotion, sensory processing, pain perception, empathy

Parts of the non-cerebrum

Cerebellum: Movement control center (balance, coordination, posture, motor learning

Brainstem: Midbrain, pons, medulla

1. Midbrain: Motor control, arousal, attention, visual, and auditory processing

2. Pons: breathing, sleep cycles, facial sensation, and movement

3. Medulla: Autonomic functions (heart rate, respiration, blood pressure); reflexes (coughing, swallowing, vomiting)

Brain landmarks

Central sulcus: separates the frontal and parietal lobes

Precentral gyrus: Primary motor cortex (frontal lobe)

Postcentral gyrus: Somatosensory cortex (parietal cortex)

Lateral (Sylvian) fissure: Separates the temporal lobe from the frontal and parietal lobes

Longitudinal fissure: Fissure that separates the left and right hemispheres

Superior temporal gyrus: Auditory processing and speech comprehension (temporal lobe)

Korbinian Brodmann

Came up with the idea that different regions of the brain have a distinct cellular structure that performs different functions

Thalamus

Major sensory relay station (taste, touch, sight, sound — everything but smell); motor output relay; involved in sleep, consciousness, and alertness

Hypothalamus

Maintains homeostasis (hunger, thirst, body temperature, sleep-wake cycles); involved in emotional regulation

Pineal body

Produces melatonin to regulate sleep-wake cycles

Basal forebrain (ventral & medial)

Cholinergic neuromodulatory inputs to the hippocampus and cortex; involved in attention, learning, memory, and arousal

Basal ganglia (dorsal & lateral)

Group of nuclei involved in motor control and action selection; includes the dorsal striatum (caudate nucleus and putamen), globus pallidus, subthalamic nucleus

Cortical white matter

Myelinated axons that facilitate communication within the same hemisphere and between hemispheres

Corpus Callosum (white matter)

A commissural fiber (bundle of axons) that connects the left and right hemispheres

Internal Capsule (white matter)

A bundle of axon that connects the cortex to subcortical structures including the thalamus, brainstem, spinal cord, and basal ganglia

Neurons

Sense environmental changes; process information; communicate changes to other neurons; command body’s response (~85 billion in the brain)

Glia

Insulate, support, and nourish neurons (~85 billion in the brain)

Nissl stain

Stains charged molecules like the rough ER, ribosomes, and nucleolus to view the cytoarchitecture

Golgi stain

Stains a small percentage of neurons, but you can see the neuron in its entirety

Reticular theory (Golgi)

Neurons were all connected via their neurites, forming a continuous network

Electron microscope (1950s)

Uses electron beam to visualize the tissue sample; allowed the neuron doctrine to be confirmed via the synaptic cleft which proves space between neurons

Neuron doctrine (Ramón y Cajal)

Neurons communicate with each other by contact, not continuity

Components of a neuron

Soma, axons, dendrites

Soma

Cell body of the neuron

1. Cytoplasm: contents within the cell membrane, not including the nucleus

a. Cytosol: Watery fluid inside the cell

b. Organelles: Membrane-enclosed structures within the soma

2. Nucleus

Nucleus (in neuron)

Contains chromosomes, and within those chromosomes are genes that are specific segments of DNA. Neurons differ from other cells because of specific genes.

Cytoplasm

Contains ribosomes which can be free-floating or bound to the rough ER. Used in translation.

Translation

Translation:

1. Cytosolic proteins

• Synthesized on free-floating ribosomes

2. Membrane-bound proteins

• Synthesized on ribosomes in the rough ER

Smooth ER

Protein folding; regulate balance of chemicals like calcium; continuous with rough ER, no ribosomes

Golgi Apparatus

Protein modification; protein packaging (e.g. shaped for where the protein will go)

Mitochondria

Krebs cycle; inhales pyruvic acid + oxygen; exhales ATP + CO2

Neuronal membrane

Encloses the cytoplasm; proteins in the membrane vary by location; proteins in the membrane are directly responsible for neuronal function

Neuron cytoskeleton

Microtubules, microfilaments, neurofilaments

Microtubules

• The largest cytoskeletal element

• Important for intracellular transport

• Run longitudinally down neurites (axon, dendrites)

• Straight, thick-walled, hollow

• Strands of tubulin (small, globular)

• MAPs (microtubule-associated proteins) regulate the polymerization of microtubules

• Tau (famously the source of neurofibrillary tangles in Alzheimer’s Disease) is a MAP

Axoplasmic transport

Transport of proteins and other materials along the microtubules via motor proteins

1. Anterograde (soma to axon terminal): kinesin

2. Retrograde (axon terminal to soma): Dynein

Microfilaments

• The smallest cytoskeletal element

• Found throughout the neuron and especially present in neurites

• Braids of two thin strands of actin

• Run longitudinally down neurites and closely associated with the

neuronal membrane

• Involved in changing neuron shape, especially at the synapse

Neurofilaments

• Intermediate size

• Three protein strands woven together

• Each strand is one long protein, not a polymer of small proteins —> this makes them quite strong

• Found in all cells

• Structural support in axons

Axon

1. Axon hillock (beginning)

2. Axon proper (middle)

3. Axon terminal (end)

Can have collateral (branches)

Axon vs Soma

1. no rough ER or free-floating ribosomes in the axon

2. different proteins in the membrane

Synapse

Point of communication between two neurons

1. Presynaptic: Axon terminal (synaptic vesicles —> neurotransmitters)

2. Synaptic cleft

3. Postsynaptic: Neuronal membrane (postsynaptic density —> neurotransmitter receptors

Synapse classification

Axodendritic: Axon to spine head, spine neck, or dendrite)

Axosomatic: Axon connections to cell body

Axoaxonic: Axon to axon

Axon terminal vs axon

1. no microtubules in terminal

2. synaptic vesicles only in terminal

3. many mitochondria in the terminal

4. many membrane proteins at the terminal

Bouton en passant/terminal in passing

Axon terminal is in the middle of the axon

Actin

Serves as a scaffold, anchoring proteins at the synapse.

Dendrites

• Branches off the soma, receives inputs from other neurons

• Apical vs basal dendrites

1. Apical dendrites receive inputs from thalamic neurons (basic sensory info)

2. Basal dendrites receive information from cortical neurons (higher-order informaiton that brings together multiple sensory modalities)

Straight mitochondria

Healthy mitochondria

Donut mitochondria

A sign of cellular stress and dysfunction (impaired ATP production)

More donut mitochondria = less surface area of the active zone and fewer docked synaptic vesicles = decreased release of neurotransmitters = decreased cognitive flexibility

Dendritic spines

Thin spines: Highly dynamic; give plasticity to the network; involved in cognitive function where flexibility is needed like working memory or error-processing

Mushroom spines: stable, long-lasting; involved in stable networks like long-term memory and sensory signaling

(Fewer thin spines = worse cognitive flexibility)

Primary sensory neurons

Receive information from the outside world via sensory receptors; synapse on other neurons

Interneurons

Receive information from other neurons; synapse on other neurons

Motor neurons

Receive information from other neurons; synapse on muscles to control movement

Unipolar neurons

One neurite (sensory neurons form skin, muscles, joints, and organs)

Bipolar neurons

Two neurites (sensory neurons of special senses like vision, hearing, balance, smell, etc.)

Multipolar neurons

Many neurites (most neurons)

Pyramidal neuron

Pyramid shaped neurons (are always spiny)

Stellate neuron

Star-shaped neurons (can be spiny or aspinous)

Spiny neurons

Neurons with a lot of dendritic spines

Aspinous neurons

Neurons with no dendritic spines

Cholinergic neurons

Motor neurons that release acetylcholine at the synapse onto muscles

Astrocytes

Most numerous glia in the brain; fill spaces between neurons; influence neurite growth; regulate chemical content of extracellular space; part of the tri-partite synapse

Myelinating glia

Insulate axons to help electrical signal down the axon

Golgi Type I

Projection neurons that have long axons that connect one region to another

Ex) pyramidal neurons

Golgi Type II

Local circuit neurons that have short axons that do not extend beyond the vicinity of the cell body

Oligodendrocytes (CNS)

Found in the brain and spinal cord, one oligodendrocyte produces many sections of myelin (e.g. one cell creates and is connected to 8 sections of myelin)

Schwann cells (PNS)

Found around all other nerves, one Schwann cell only creates one section of myelin

Nodes of Ranvier

Space between myelin; this space is essential for axonal transmission; even with myelin, the action potential decays over distance, the nodes reset the signal strength which helps the AP continue down the axon; myelin helps AP skip chunks of the axon, only ion channels at the Nodes are needed = less energy needed

Microglia

Serves as phagocytes to remove cellular debris, involved in synaptic pruning during development; involved in immune function; involved in repair and regeneration after injury

Membrane potential (voltage)

Voltage across the neuronal membrane at any moment;

Resting membrane potential (voltage)

Voltage maintained across the membrane at rest; it is always negative at -65 mV; determined by K+/Na+ pump and K+ leak channels

Action potential (voltage)

A brief fluctuation in membrane voltage when the neuron is active

Cytosol and extracellular fluid

1. Water

2. Ions

a. sodium (outside cell)

b. chloride ( outside cell)

c. potassium (inside cell)

d. misc. anions (inside cell)

Hydrophilic

Water-loving molecules, ions, and other polar molecules can dissolve in water

Hydrophobic

Water-fearing molecules, non-polar molecules that can’t dissolve in water

Sphere of hydration

Cloud of water molecules that surround each ion and bonds with them

Lipid bi-layer

Creates the neuronal membrane; head is hydrophilic, tail is hydrophilic; ions/polar molecules can’t pass through

Phospholipid membrane

Proteins are embedded in the membrane; control the resting membrane potential and action potential through ion channels and ion pumps

Ion channels

Form pores in the membrane that allow ions to flow through; selective to specific ions; allow ions to move from high to low concentration gradient

Ion pumps

Forms pores that also allows ions to pass through; allow ions to move from areas of low to high concentration; requires energy

Sodium-potassium pump

Always functioning whether at rest or when neuron is active; maintains a difference in ion concentration; maintains resting membrane potential; sodium goes out, potassium comes in

Diffusion Force

Movement of ions driven by differences in ion concentration across the membrane (determines direction that ions move)