PSYC 100 - Biological Basis

Central Nervous System

• Primary processing center

• Brain and spinal cord

• Information comes into these places for processing

• Reflexes (think spinal tap)

Peripheral (Nervous) System

• Includes somatic and autonomic nervous system

• All sensing and nerves that bring information to your spinal cord and brain for processing

• All muscle control

Somatic Nervous System

• Channel used to pass sensory input and outgoing commands from brain to skeletal muscles

• Manages voluntary muscle movement

• Sensory system “afferent”

• Motor system “efferent”

Autonomic Nervous System

• Manages involuntary actions

• Regulates internal states (function of heart and stomach)

• Includes sympathetic and parasympathetic systems

Sympathetic Nervous System

• Fight or flight

• Heart rate increases

• Liver releases glucose

• Dry mouth

Parasympathetic Nervous System

• Rest and digest

• Normal state

• Slower breathing

• Constricts bladder

Endocrine System

Glands and organs that produce hormones (chemical messengers)

Sensory System (pathway)

• Afferent information

• Periphery to brain

• Touch → somatic sensory pathway → nerve→ spinal cord → CNS pathway → medulla oblongata → sensory cortex (brain)

Motor System (pathway)

• Efferent

• Brain to periphery

• Upper motor neurons (from motor cortex in brain) → medulla → lower motor neurons (if above neck) or → spinal cord (to below neck muscles)

Glial Cell

• Non-neuronal cells that support and nourish neurons in CNS and PNS

• Neuro-glial signaling and glia-glial signaling

• Types include oligodendrocytes and astrocytes

Microglia

Immune surveillance and eating dead tissue

Oligodendrocytes

Myelin sheath production

Astroglia (astrocytes)

Connect neurons to blood vessels

B

Soma (cell body)

A

Dendrite: receive chemical signals and move impulses towards cell body (soma)

C

Axon hillock: currents received from the dendrites build up and accumulate here, if enough builds up, the neuron fires an action potential (electrical)

D

Myelin sheath: fatty protective coating that wraps around the axon and allows impulses to travel faster down the axon and jump from gap to gap

D

Nodes of Ranvier: allow electrical signals to move rapidly down the axon, and build up electrical charges

F

Axon terminal (button): converts electrical impulses taken from the dendrites, through the axon and turns them into chemical impulses that send messages to other muscles, neurons, or glands.

Pre-synaptic cell

• Ligands (neurotransmitters) are released from the axon terminals

• Are received by dendrites of other neuron

Post-synaptic cell

• Ligands (neurotransmitters) bind to chemical receptors on the dendrites of this cell

Neuron at rest

• ~-70mV difference in charge inside and outside neuron

• more negative charge inside than outside (membrane is polarized)

• There is Na(+), Cl(-) outside the membrane (strange because diffusion would normally allow cell to reach equilibrium with environment and not be polarized.

• Occurs because of sodium potassium pump

Sodium potassium pump

• Pushes sodium out of cell and pumps potassium in

• Most brain power goes to fueling pumps like this

Ion channels

Special channels that allow only certain types of proteins through

Action potential

Rapid reversal of electrical movement across a cell.

Action potential propagation

• Movement of of axon potential down the axon terminal

• Plasma membrane between axon and exterior

• Moves in one direction away from start of axon potential because during the refractory period, the previous segment closes its sodium channels (Na) and opens its potassium channels (K) to repolarize, this forces singular direction of action potential movement

Synaptic cleft

tiny gap between neurons between axon terminal of one cell and dendrite of next cell

Synaptic vesicle

sacs of neurotransmitters stored and released from the presynaptic cell during neurotransmission across synaptic cleft

Inhibitory neurotransmitter

decrease the likelihood that a post-synaptic neuron will fire an action potential

cause hyperpolarization, allowing positive ions out (K) and negative ions (chloride) to rush in

Excitatory neurotransmitter

increase the likelihood that a receiving neuron will fire an action potential

they do this by encouraging depolarization opening channels to allow positive ions to rush in and make it closer to its firing threshold

Presynaptic membrane

• area on the end of axon terminal, synapses

• where neurotransmitters are released

Postsynaptic membrane

• membrane on the dendrites of the cell receiving the neurotransmitters

• has receptors

Hemsiphere

half of the brain, each has different functions

Sulcus

the bottom part of the brain folds (latin for fissure)

Gyrus

the top part of the brain folds (latin for circle)

Lobe

area of the brain

Fissure

gap between the two hemispheres

Corpus callosum

thick bundle of nerve fibers connecting the two hemispheres deep in the center of the brain allowing communication between the two

Contralateral hemispheric organization

the opposite half of the brain controls the other half of the brain

Neocortex

outermost layer of the brain “thinking cap”

Frontal lobe (and functions)

• largest lobe

• located at front of brain

• manages higher level thinking, voluntary actions, and social interactions

• executive functioning, personality, speech and language, reward and motivation

Parietal lobe (and functions)

• located underneath crown of your head

• proprioception, sensory integration, locational awareness, learned movements

Occipital lobe (and functions)

• located at back of your head

• smallest lobe

• most visual signals are received here, spatial/depth perception, facial recognition, color processing

Temporal lobe (and functions)

• paired set of areas on right and left sides of the brain near temples and ears

• auditory processing, language comprehension, memory formation, and emotional regulation

Somatosensory and motor homunculus

map that shows the human body for which parts of the brain control that part of movement or sensation. The size of each body part reflects the amount of brain tissue dedicated to it

Medulla

• bottommost part of the brain, connecting spinal cord and brain

• controls involuntary life processes like heart rate blood pressure and breathing, reflexive actions like sneezing, swallowing, and vomiting

• transmits signals between spinal cord and rest of brain

Pons

• brain structure located above the medulla

• controls breathing with medulla, sleep cycle, pain signals

• messenger for sensory and motor messages

• controls facial expressions

Reticular activating system

• network of neurons in brainstem

• filters sensory input and controls wakefulness, attention, and arousal

Cerebellum

• area of hindbrain, holds half of all your neurons

• coordination and walking, cognition and emotional regulation

• small brain

Thalamus

• in middle of brain

• main relay station

• processes movement and sensory info before sending it elsewhere for interpretation

• plays role in sleep, wakefulness, learning, and memory, prioritizing attention, thinking and memory

Basal ganglia

• group of brain structures linked together

• control body's ability to move, learning, emotional processing, decision making, reward and addiction

• center of brain

Limbic system

• emotional nervous system

• regulates emotions, behavior, motivation, and memory

• group of brain structures work together to process memories, thoughts, and memories and tell your body how to respond

• manages pain and pleasure

• contains hypothalamus, amygdala, thalamus, hippocampus

Prefrontal cortex

• located behind forehead at front of brain

• helps with attention, emotions, self-control, and decision making

Hippocampus

• small part of brain

• helps with learning and memory

• stores long term memories

• part of limbic system

Amygdala

• small part of brain

• major emotional processing center

• links emotions to memories, learning, and senses

• detects danger and sends stress signals

Hypothalamus

• keeps your body in homeostasis

• influences autonomic nervous system by managing hormones

• manages blood pressure, temperature, hunger and thirst, fullness, mood

Cingulate gyrus

• major part of limbic system

• arch-shaped fold of brain tissue

• directly above corpus callosum

Split brain patients

• studies looking at patients with damage corpus callosum so no communication between hemispheres

• show left hemisphere is dominant for verbal language processing

neurotransmission (process)

1. Axon potential arrives at axon terminal

2. Voltage-gated calcium channels open

3. Calcium enters the presynaptic neuron

4. Ca signals to neurotransmitter vesicles

5. Vesicles move to membrane and dock

6. Neurotransmitters released via exocytosis

7. Neurotransmitters bind to receptors

8. Signal initiated in post-synaptic cell

ionotropic receptors

• fast neurotransmitters

• have their own channels

• Glutamate (excitatory)

• GABA (inhibatory)

• 95% of your synapses are GABA and Glutamate

metabotropic receptors

• neuromodulator

• slow neurotransmitters

• serotonin, acetylcholine, adrenaline

• don't have their own channels so take longer to be absorbed, but also tend to last longer

re-uptake vs. degradation

neurotransmitters are recycled into new vesicles

enzymes floating around break down the neurotransmitters