Cells of the Nervous System

• Neurons

The basic building blocks of the nervous system. Made of a cell body, a nucleus and internal machinery similar to other living cells.

They communicate with each other through chemical messages that alter the electrical activity if other neuron’s

the glia cells are the cells in the nervous system that provide support function

• Dendrites

They are extensions of the membrane of the cell body and they receive chemical messages from many other neuron’s.

This is all accomplished by the neurotransmitters binding to proteins called receptors, that are embedded in the membranes of the dendrites

• The soma and axons

The soma (cell body) is the location of metabolic processing in the cell and contains the cells organelles. Protruding from the cell membrane, you will find the axon hillock, which is the beginning of the axons.

The terminal button houses vesicles, due to this sending signals into the space between neuron’s it is also called the presynaptic neuron, they release their contents into the synaptic cleft.

How Neuron’s Transmit Messages - Action Potential

-70 mV = polarized because the charge is far away from 0, which is natural. When the cell is polarized it is art rest and will NOT release neurotransmitters. The more positively charged the particles inside the cell are the more positive the inside of the cell.

If K concentration in the extracellular space are lowered, there will be trouble maintaining resting potential

Depolarization = Influx of sodium

How Neurotransmitters and Receptors Work

• Excitatory NTs - they increase the probability of a neuron becoming electrically active

• Inhibitory NTs - They decrease the probability that the neuron is activated

An excitatory NTs binding to a receptor would make the charge inside the. neuron more positive

Your Brain on Drugs

Different NTs have different effects depending on the location od the receptor'; drugs that alter our experiences work by acting like a NT or stopping a NT from finding the receptor site

• Agonists mimic the action of endogenous (naturally produced by the body) NT

• Antagonists prevent the action of the endogenous NTs

Main Neurotransmitters

• Glutamate - Excitatory

• GABA - Inhibitory

• Acetylcholine - Excitatory

• Serotonin - Both

• Norepinephrine - Both

• Enkephalins/ Endorphins - Both

Glial Cells

Support the Neurons and actually outnumber them ten to one. They perform vital roles in the nervous system like:

• providing structural support

• brining nutrietns

• removing waste and dead neurons

• speeding up electrical impulses

Myelin is made of a protein and fat, its wrapped around the axons of some neurons in the brain and spinal cord by glial cells called oligodendrocytes

By creating the myelin sheath, these cells speed up communication in the CNS. Schwann Cells do the same thing for nerves outside the brain and spinal cord.

Cells called astrocytes and microglia help form the immune system of the brain. They both fight infections and clean up debris that could lead to dangerous inflammation in the brain.

Neurodegenerative diseases - disorders in which neuron’s die over time and cause progressive loss of a particular ability.

Brain Anatomy: how to build a sophisticated network

Neural Network- Complex connections between the dendrites and axons of many neuron’s

• Efferents - carrying impulses away from the CNS trigger NT or hormones release in an organ or muscle

• Afferents - Carrying impulses back to the CNS from the organs and muscles

Neuroplasticity = The ability of neuron’s and their networks to change

Neocortex - Conscious thought/ decision making

Medulla - Basic Life functions

CNS vs PNS

• The Peripheral Nervous System: Bridge between Brain, Body, and World

Everything else…

The information in the brain is no good if it I not share with the body. Split into the somatic (voluntary) and Autonomic (Automatic) divisions.

• Somatic Nervous System: Voluntary Movement

Contains the neurons and nerves that control the muscles for voluntary movement and bring sensory information from the body to the brain

If the spinal cord is injured, any body parts being controlled by nerves form spinal cord segments below that point can no longer be controlled voluntarily. It will alas be unable to perceive sensory information from those body parts.

• Autonomic Nervous System: Automatic Movement

Responsible for all the systems that regulate all the atomic functions that keep you alive, functional, and healthy

It is even further divided into the sympathetic and parasympathetic connections to the organs and endocrine system structures

Parasympathetic = Lower brain and Spinal cords. Not fight or flight mode for example your turned on…

Sympathetic = Fight or Flight response, mainly made up of neurons and supporting cells in the spinal cord

Sections of the Brain: The Central Command Center

• Parietal Lobe - The association lobe, meaning it integrates sensory information from across the brain. It houses the primary sensory processing area for touch but receives information about what we are seeing from the visual cortex

• Frontal Lobe - The decision making portion and movement. The prefrontal cortex receives input from across the cerebral cortex and helps us decide when, why and how we do things

• Temporal Lobe - Assist with the task of forming memories and processing sound. It houses the primary auditory cortex, which is the primary sensory processing area foe hearing

• Occipital Lobe - The visual cortex which is the primary sensory processing area for visual information, or light. The region is also referred to as the striate cortex, because it has colours of neurons that are organized to process very specific visual information.

Life Functions and Basic Reflexes

The Medulla and Pons are critical for sustaining basic life functions. Part of their job is to regulate basic life functions in the background, but they have another job; connecting the PNS and CNS to regulate what we do and pay attention to

• The Medulla - the lowest anatomical potion of the Brian and the transition point between the brain and spinal cord. Without it we could not breathe, our hearts would. not beat, and we would be incapable of swallowing

• Pons - Information from the spinal cord enters the medulla and is then transferred to the pons and to high-order brain functions. They help to regulate arousal (excitement and energy), coordinate the senses with the cerebellum , and serves as a bridge for tracts from the upper brain to the lower brain and spinal cord.

• Reticular Activating System - A network of neuroms spanning the centre of the medulla and pons. It bridges the functions of the body and brain via connections to the spinal cord and thalamus. Its 2 functions are our level of arousal and the focus of our attention on tasks, people, or object

The Coordinators

The networks of neurons and glia (often called nuclei or ganglia) in the limbo system, basal ganglia, and cerebellum are designed to be modifiers of action and thought. They collect information encoded by impulse from other area od the CNS and help cortical circuits modify high-level commands. These areas help us adjust on the fly after areas like the prefrontal cortex make decisions.

The Limbic System

Includes circuits in the context and the midbrain. Helps regulate our endocrine system as well as our emotions and emotional memory. Containing the prefrontal cortex, the olfactory cortex, raw amygdala, the hippocampus, the cingulate gyrus, and the hypothalamus. Integrates more primitive functions with higher-order thought

• Amygdala - increases electrical activity in its neurons when we are under threat. Involved in aggression responses and romantic love (increased levels norepinephrine)

• Hippocampus - A circular structure medial to the temporal lobes, is set up as a loop of neurons that are activated when we are forming memories.

• Cingulate Gyrus -Ventral to the Neocortex, an interesting set of neuron’s. This help focus our attention and thoughts on things that are unpleasant to us

• Hypothalamus - Helps control several functions in the autonomic and endocrine systems. Responsible for regulating hunger responses, sexual behaviour, temperature, and aggression

Coordinating Movement

The basal ganglia are interconnected groups of neurons that serve to modulate movement commands in. the brain before they reach the spinal cord. They are many groups of neuronal circuits near the base of the brain that help to coordinate movement and assist in making movements more automatic, it consists of:

• Dorsal Striatum - Caudate nucleus and putamen

• Ventral Striatum - Nucleus accumbens

• Globus Pallidus

• Sunstantia Nigra *responsible for Parkinson’s disease

• Subthalamic nucleus

The Cerebellum

The rhythm and timing machine. The neuronal circuits in the layers of the cerebellum are strategically connected with other parts of the Brian to modify what they do, mainly for movement but also cognitive tasks.

3 Divisions of the cerebellum

• Spinoceerbellar - Helps match sensory input with motor plans in order to fine tune movement patterns

• Vestibulocerebellar - division processes information from the inner ear to help adjust you posture and balance

• Cerebrocerebellar - manages connections with the pons and thalamus to adjust the timing and planning of movements

Thalamus: The Relay Station

Each cluster of neurons in the thalamus corresponds to a particular set of functions and locations in some part of the brain, it is what the cortex uses to choose which thing we pay attention to. All senses (but smell) must pass through the thalamus before it is relayed to the neocortex for interpretation, organization, and action plans.

Neocortex (New Brian): Higher - Level Processing

4 Basic sections (lobes) of the neocortex that each performs a specific function, however they do all work together.

there are 3 distinct features of the neocortex that make it very clear to detect

• Gyri - ridges

• Sulci - Valleys

• Fissures - Space between lobes

These structures allow us to fit more brain into a sm all space like a human skull, it is composed of 6 layers,

Adjacent to every lobe of the neocortex is an area called association cortex that even further process the information to integrate it with other sensory information.

The Neocortex is responsible for the integration and making sense of all the information that enters our worlds

Frontal Lobes: Executive Decisions

The neurons in these areas are active during times we must make decisions about how to act or what to do. An intact frontal lobe seems to be necessary for mining our ability to regulate our behaviour and thought.

Outputs if the frontal lobes tend to be inhibitory

Regions of the Frontal Cortex

• Prefrontal Cortex - Frontal Association Area

• Frontal Eye Fields

• Premotor/ Supplementary Motor cortex

• Primary Motor Cortex

• Broca’s Area (Left Side)

The Prefrontal Cortex (PFC) - receives input from all parts of the cerebral cortex. Helps us decide when, why and how we do things. About 14-17% of the neurons of the brain can be found here.

There are also parts in the prefrontal cortex that are even further specialized to make decisions based on specific criteria or input, 2 examples include:

• Ventromedial Prefrontal Cortex (vmPFC) - Closer to the bottom inside of the cortex and is responsible for modulating behaviour based on fear

• Dorsolateral Prefrontal Cortex (DLPFC) - Closer to the top side of the head and is responsible for maintaining information in our working memory and change how we do things depending on what test we are trying to complete

It is the last region to undergo myelination

• Dorsolteral Prefrontal Cortex - Working Memory

• Motor Cortex - Sends commands for voluntary movements

• Corticobular Tract - Carries commands to facial muscles

• Ventromedial Prefrontal Cortex - Regulates fear based behaviour

Parietal Lobes: Space, Time, and Numbers

Heavily involved in functions like processing numbers and performing calculations.

The sensory cortex in the anterior portion (closer to the frontal lobe) of the parietal lobe receives input from the conterlateral (opposite) side of the body

Temporal Lobes: Listen to the Memories

Right above your ear. The neurons in this area assist with tasks like forming memories and processing sound input form the auditory nerves.

Temporal Lobe Lesions (area where cells have died) usually result in memory loss and especially the loss of ability to form new memories

Regions of the Temporal Lobe

• Auditory Cortex - Receiving and processing messages from the ears through the axons of vestibulocochlear nerve, the caudal part of the temporal nerve

• Olfactory Cortex - Smell, The only sensory information that does not pass through the thalamic relay synapses but instead goes straight to the temporal lobes

• Auditory Association Area - Houses Wernicks Area, important for processing language

Occipital Lobes: Vision of the Present

About a third of our brains is for processing and interpreting visual information

The optic nerves originate in the retina of the eye and decussate partially at the optic chiasma.

There are neurons so specialized in your occipital cortex that some of them only fire when they see an object or feature in a particular angle or position.

Brain Laterality

The idea that one hemisphere of the brain performs different function than the other

The Corpus Callosum

a thick bundle of fibres whose purpose is to connect the two hemispheres and allow them to share information.

Sometimes to treat people with epilepsy is to transect the corpus callosum.

The Endocrine System

A system of glands throughout the body that releases hormones. These hormones have profound influences on our behaviour. It serves as a secondary control system that assists and gives valuable feedback to the nervous system about what is happening in the body

The major endocrine control centres rest within the CNS:

• The Hypothalamus - secretes hormones and controls the pituitary gland via direct nerve stimulation/ chemicals

• The Pineal Gland - Secretes melatonin to regulate sleep cycles

• The Pituitary Gland - Secretes a host of hormones that affect sexual behaviour, reproduction, circulatory function, hunger, and responses to aggression

The HPA Axis and Stress

People with chronic stress, neurons in the hypothalamus can become active more often.

Driving the pituitary gland to tell the adrenal glands to produce more cortisol. When stress is temporary this is hormone is good.

Research Methods in Neuroscience

What do we want to know? We will look into epistemology of neuroscience by looking into the following:

• How scientists have discovered what we have learned so far about the nervous system

• How our measurement tools and findings have enhanced human life or experience

• What we will don’t really know

We currently study the nervous system by:

• Structural Imagining

• Recording

• Dissection

• Functional Imaging

Methods of Imaging

• CT scan

• MRI

• fMRI
  DTI

• PET scan