- Largest part of the brain

- made up of two cerebral hemispheres separated by the longitudinal fissure

- The cortex covers the cerebral hemispheres and is "convoluted", increasing the amount of corext

- Contains the thalamus and hypothalamus

1) Cortex has more convolutions

2) the cerebral hemispheres (forebrain) are larger in proportion to the lower areas of the brain

--Illustrates a hierarchy of increasing complexity from spinal cord, to hindbrain, to midbrain, and finally forebrain.

Directional language in the brain:

Anterior             Dorsal          Lateral 

Superior            Ventral         Medial

Inferior

Posterior

Anterior: Towards the front

Posterior: Towards the rear

Superior: Location above another structure

Inferior: Location below another structure

Lateral: Toward the side

Medial: Towards the middle

Dorsal: Towards the back

Ventral means towards the stomach

Main function: Movement and complex human capabilities

Major Structures:

Primary Motor Cortex

Prefrontal Cortex

Subcortical Structures:

Secondary Motor cortex

Basal Ganglia

Broca's area

Located in the Precentral Gyrus

Contains a sensory map of the human body called a homunculus with larger areas devoted to parts of the body that make more precise movements--works with secondary motor cortex and subcortical structures

Coronal Plane

Lateral Plane

Horizontal Plane

Coronal - divides the brain vertically from side to side

Lateral - divides the brain vertically from anterior-posterior direction

Horizontal - divides the brain between top and bottom

Largest part of the human brain, located at the anterior portion of the brain.Development of these processes is NOT the same in everybody. (Think adolescence and pruning)

• Organizing and planning
• invovled in some types of decision making
• important for impulse control
• adjust behavior in rsponse to rewards and punishments
• Some forms of decision making
  

• Impairs the ability to learn from consequences
• Decreases the ability to control impulses
• Is often found in depression and schizophrenia

Located posterior to the central sulcus - important for body sensations and spatial localization

Contains the Primary Somatosensory Cortex and parietal associtaion areas

Located on the postcentral gyrus, which is anterior to the central sulcus. It recieves information about the skin senses, body position, and movement. Contains a sensory homunculus with map size corresponding to sensitivity in that part of the body. (i.e. finger tips, face, tongue are larger because more sensitive)

Combine information from body senses and vision--used to identify objects by touch, determine the location of the limbs, and locate objects in space.

Involved in mathematics skills and some language (Particuarlly, the spatial recognition of these--i.e. 52 and 25 are diff. because of the location of the 5 and 2. Same w/ language. Depends upon location of the letters and order of words)

Neglect of objects, people, and activity on the opposite side.

- Usually caused by damange on the right side

- Patient may deny there is anything wrong, even when a limb is paralyzed.

Lobes are separated from the frontal and parietal lobes by the lateral fissure

Contain the auditory cortex and the inferotemporal cortex

-Also, the hippocampus and amygdala

Temporal Lobe's main function is hearing and vision

-Located w/in the temporal lobe; inferior to the Precentral Gyrus and lateral fissure.

-Function: Recives information from the ears.

-Includes language, auditory, and visual association areas. + Wernicke's area.

Located Inferior to the postcentral gyrus (somotosensory cortex)

-Function: involved with language comprehension and production

-Damage: results in meaningless speech and poor comprehnsion of written and spoken communication

Located in the temporal lobes

Function:

Hippocampus is involved in long-term memory, consolidation of input

Amygdala adds emotional tone to sensory in put and memories

Located in the posterior part of the brain

Function: Processes visual stimuli

Structures: Visual Cortex and Secondary Visual Areas

Subcortical structure located in the forebrain, inferior to the lateral ventricles

-Recieves information from all the senses except olfaction

-Relays this sensory information to the cortex

-Some portions of the thalamus project more diffusely and play a role in arousal

Subcortical structure in the forebrain inferor to the thalamus

- Controls emotions and motivated behaviors such as eating, drinking, and sexual activity

-Exerts major control over the autonomic nervous system and endocrine system by way of the pituitary.

**Note, there are two thalamus and hypothalmus structures in the brain - one for each hemisphere**

Posterior to the thalamus

- Secretes melatonin, a hormone that induces sleep

- Participates with other structures in controlling daily rhythms in humans

Dense band of fibers at the bottom of the longitudinal fissure (actually a subcortical structure)

Purpose: Shares information between the hemispheres.

Function: Ventricles filled with cerebralspinal fluid that carries material from the blood vessels to the CNS and transport waste materials in the other direction

Names and Locations:

Lateral Ventricle: in the frontal lobes, into the occipital lobes, and curve around into the temporal lobes.

Third Ventricle: Connected to the lateral one, and goes between the two thalami and the two halves of the hypothalmus

Location of Midbrain: At the top of the stem

Function: secondary roles in vision, audition, and movement

Superior Colliculi: Help Guide eye movements and fixation of gaze

Inferior Colliculi: Help locate the direction of sounds

Substantia Nigra: Porojects to the basal ganglia to integrate movements

Ventral tegmental area: plays a role in the rewarding effects of food, sex, drugs, etc.

Medulla: Involved in control of essential life processes (cardiovascular activity and respiration)

Pons: Centers related to sleep and arousal, which are part of the reticular formation

Reticular formation: Attention, reflexes, and muscle tone (This structure is a bunch of nuclei that run from hindbrain to midbrain)

Cerebellum: Located on back of the brain stem--wrinkled and divided down the middle like the cerebral hemispheres (little brain)--refines movements initiated by the motor cortex by controlling their speed, intensity, and direction--helps maintain body's equilibrium by recieving impulses from the vestibular system--also plays a role in motor learning, as wellas in other cognitive processes and in emotion.

--Damage to cerebellum causes disruption in patterns, like walking--more refined movements, not in gross motor like the motor cortex

Reuptake

-Takes the transmiter back into the terminals to be used again

- Glial cells can reabsorb transmitters at some synapses

1) Sensory Neuron transmit signals through the dorsal root of each spinal nerve

2) The axons of the motor neurons pass out through the ventral root

3) In some cases, sensory neurons connect through interneurons, with motor neurons; this pathway produces a simple, automatic movement in response to a sensory stimulus, called a reflex

1) A protective, three-layered membrane called meninges. The space between the meninges and the CNS is filled with cerebrospinal fluid, which cushions the neuroal tisse from blows and sudden movement.

2) The blood brain barrier limits passage into the brain of toxic substances and neurotransmiters circulating in the blood.

Cell Body or Soma

Dendrites

Axon + Axon Hillock

Myelin Sheath

Terminals

Chemical substances found inside the axon terminals

They communicate with other neurons, muscles, and organs.

Dentrites: Number varies from neuron to neuron, as well as length--can grow new ones through life span by "learning" --Senality and Dementia are associated w/ shorter dentrites 

Axons: Can be more than a meter long and can grow new terminals--they can only send one message, but to multple poitns simeltaneously.

Cell Membrane: Composed of lipid molecules and proteins

-Cell membrane holds the cell together and controls the environment in and around the cell

-Properties of the membrane and the proteins allow the importing and exporting of substances and the changing of electrical charge

-Membrane varies in permeability (Water, oxygen, and Carbon dixide pass freely, others pass through protein channels if circumstances are right)

Results from selective permeability of the membrane

Polarization is the difference in electrical charge between the inside and outside of the cell

This difference in electrical charge is referred to as voltage.

Polarization = Voltage (Usually negative)

Difference in charge between the inside and outside of the membrane when the neuron is at rest. (i.e. the inside is Neg. charged, the outside is Pos. charged)

- Usually between -40 and-80 millivolts, with avg. of -70 for most neurons.

- The charges are caused by unequal distributions of ions on either side of the membrane

     *Outside: Mostly Sodium (Na+) and Chloride (Cl-) ions

     *Inside: Mostly potassium (K+) ions and organic anions (A-).

Force of diffusion: Ions move from area of high to low concentration ions (Ions want space--will want to move when crowded)

Electrostatic Pressure: Ions are repelled from the side of the membrane with the same charge and attracted to the side with the opposite charge (This means outside ions want in, and inside ions want out.

Organic Anions (A-) are too large to leave the cell (They are on the inside of the membrane), and Chloride ions (Cl-) (which are on the outside) are repelled by organic anions. 

Sodium and potassium channels are closed, so only a few pass through the membrane, and the ones that do leak are returned by the sodium-potassium pump.

Neuron recieves excitatory signals which causes potassium and sodium channels to open and allow passage of ions through small portion of the membrane. As this spreads, the entire neural cell becomes depolarized; however, it deminishes over distance, so it is referred to as a local potential.

Action Potential is an abrupt change in membrane polarization that allows the neuron to communicate over large distances.

It occurs when the depolarization of a single cell membrane reaches a threshold of -60Mv. This causes sodium channels to open becuase of force of diffusion or electrostatic pressure

Rate of sodium entry into the membrane becomes 500 times greater than normal. Results in complete depolarization and often overshoots, changing the voltage of the cell membrane to +30 or +40 mV

No further depolarization is possible at this point. Sodium channels close.

At maxium depolarization, potassium channels open.

--due to diffusion and because the inside of the cell is now temporarily positive, potassium ions move out of the membrane. This returns the membrane to resting potential voltage.

The entire event from resting - action - resting potential again takes about 1 millisecond

Sodium pumps will also help put sodium ions back to the outside where they go.

At rest, potassium can cross the membrane easily

All or None law

Local potentials exhibt graded potential, because they loose steam over time.

Action potentials, are all or none--means that the action potential always occurs at full strength and does nto vary with stimulus intensity--it is nondecremental and does not decrease over distance.

Absolute Refractory Period

WHen the sodium channels close during the action potential, that part of the axon cannot fire again.

This limits how frequently the neuron can fire

This also prevents backward spread of depolarizaiton, so action potentials move only towards the terminals.

Relative Refractory Period

Potassium channels remain open; continued K+ outflow polarizes the membrane beyond the resting potential

A stronger stimulus is required to trigger an action potential

Rate Law

Glial Cells

1) Produce Myelin, a fatty tissue that surrounds axons, providing insulation and support

2) During development, provide scaffolds for neurons to migrate to their final destinations

3) respond to injury and disease by removing cellular debris

4) Provide energy to neurons

5) When glial cells are present, neurons make seven times as many connections with other cells

6) As behavioral complexity increases, the ration of astrocytes, a type of glial cell, to neurons also increases.

Myelin and Myelin Shealth

Myelin increases the conduction speed in axons.

-Myelinated axons have gaps called nodes of Ranvier

     - Transmission between the nodes (under the myelin) is by local potential, which moves faster than action potentials and uses less energy, but also burns out over distance.

     -Action potentials "jump" from node to node in a process called Saltatory conduction

Synapse

The connector between the presynaptic neuron and postsynaptic neuron

This is where the neurotransmitters are released and neurochemical communication between neurons takes place.

Vessicles

Membrane enclosed containers that holds the neurotransmitters--they are down in the terminals of the axon

When the action potential arrives at the terminals, calcium channels open and calcium enters the cell

This causes the vesicles to fuse with the membrane, which results in the release of transmitter into the synapse

Seven steps of synaptic function

Synthesis - Make neurotransmitters

Storage - Store Neurotransmitters

Release - NT into synapse

Receptor Interaction - Recieving NT

Inactivation - Return to rest happens in synapse

Reuptake - suck the chemicals back into the neuron

Degradation - Dissolving of NT

Ionotropic Receptors (In postsynaptic cell)

Metabotropic Receptors (In Post-Synaptic Cell)

Activation of receptions on postsynaptic cell has two possible effects on the membrane potential

HyPOpolarization: Creates an excitatory postsynaptic potential (EPSP) -- Same as depolarization

HypERpolarization: creates an inhibitory postsynaptic potential (IPSP)

     -An IPSP opens potassium and chloride channels or both

     -This makes it less likely an action potential will occur.

Neuorgenesis

Neuronal Stem Cells: They can divide and differentiate to become neurons or glial cells--> ones that do not "specialize" continue to divide and reproduce exact replicas without any signs of aging. This process is called Neurogenesis.

Neurogenesis is usd to strengthen mental capacity in two ways:

1) Make new cells: When we know everything about the environment we live in, no need for neurogenesis. Novel environments trigger neurogenesis

2) Make existing cells live longer: Exercising existing nuerons through learning makes them live longer in hippocampus

The process and big players that moved field from localization to neuroplasticity

Localization - 1850's

Penfield (1930's) - Brain mapping/Motor map/Topographical--didn't change localization

Micromapping (1960's) - Hubel and Weizel and the kittens - discovery of critical period, brain plastic only in infancy

Edward Taub (1950's) and Silver Spring Monkeys and Constrained Induced Movement Therapy

Michael Merzenich - Monkeys/Cortical real estate and Competitive plasticity

What is Hebbian Plasticity?

"Neurons that fire together, wire together"

Relates neuroplasticity to synaptic activity. (Example of the hand and goes back to the homunuculus organization of motor and sensory cortexes).

Timing is key, as is paying attentions

Advantages of Neuroplasticity?

Disadvatages?

-Can teach an old dog new tricks

-Maintaing mental activity throughout the life span

-successful treatment for stroke viticims, kids with learing disabilities, people with OCD, sensory problems (Cochlear implants, vestibular problems)

Disadvantages?

-Use it or loose it -- part of why old habits are hard to break.

- Know the limits: Each person still has limits

Repoening window of critical period plasticity?

-Made up cranial nerves that connect to the underside of the brain

- AND spinal nerves that connect to the spinal cord at each vertebra

Subsections:

Somatic

Autonomic

Sympathetic

Parasympathetic

- Motor and sensory neurons (from the skeletal muscles)

- Controls smooth muscles--stomach, blod vessles, glands, heart, and other organs

Subsections:

Sympathetic Nervous System

Parasympathetic Nervous System

Activates the body in ways that help it cope with demands (Emotional stress, physical emergencies)

--Has most of its ganglia in the sympathetic ganglion chain

- Slows the activity of most organs to conserve energy

- Activates digestion to renew energy

- Has its ganlia near hte muscles and glands they control

Proliferation

Migration

Circuit Formation

Circut Pruning

During Proliferation - Cells that will become neurons divide and multiple in the ventricular zone (250,000 new cells every minute)

During migration - These cells move from ventricular zone to final desitnation with the help of radial glial cells

--Function is determind by the time and location that it develops

During formation, axons grow towards their target cells and form functional connections

--Movement is guided by growth cones at axons tips: These detect chemical and molecular signposts that attract or repel the advancing axon

During Pruning, excess neurons and synapses are elminated.

--Neurons and synapses are strengthened or weakened depending upon presynaptic and postsynaptic neurons firing together

--Postsynaptic neurons releast neurotrophins that enhance development in the presynaptic neuron

--Plasticity of these neurons decreases later.

- Caused by mother drinking during critical period of brain development

- Often produces mental disability

- FAS brains are small and malformed and neurons are dislocated

- During migration many cortical neurons fail to line up in columns because radial glial cells revert to typical glial form prematurely.

- Other neurons continue migrating beyond the usual boundary of the cortex

Stroke: caused by artery blockage (ischemic) or rupture (hemorrhagic) -- the damange is caused by oxygen and glucose deprivation, excitotosis, and edema (swelling) -- it is the leading cause of death and disability in the US

Traumatic Brain Injury: caused by a blow to the head, penetration, or sudden acceleration or deceleration--trauma that does not produce concussion can result in brain changes typically seen in Alzheimer's Patients.

is the regrowth of severed axons

- Myelin provides a guide tube for the neuron to grow through, and the axon is guided to its destination much as in development

- Occurs in the amphibian brain and in the mammalian PNS

- In the mammalian CNS, glia produce scar tissue and growth inhibitors, and imune cells may also interfere.

Ideal means of neural repair

- Undifferentiated cells that can develop into specialized cells such as neurons, muscle, or blood

- Embryonic stem cells placed in an adult NS differentiate into neurons appropriate to that area

-Stem cells usually lose most of their flexibility, but those found in olfactory mucosa show promise for reparing neural damage

A cell, often a specialized Neuron, suited by it's structure and function to respond to a particular form of energy

--Function is to convert energy into a neural response

The energy from which the receptor is specialized

-For hearing, it is vibration in a conducting medium

Refers to the number of cycles or waves of compressions or decompressions

- Frequency, provides the perception of pitch

- A pure tone, has only one frequency (tuning fork)

- Complex sounds, are produced by multiple frequences (clarinet)

Intensity of a sound is percieved as loudness

Refers to the amplitude or size of the wave. Represents the physical energy of a sound.

Loudness is influenced by frequency of the sound

-we are most sensitive from 2000-4000hz (most conversations)

Intensity of sound also influences the perception of pitch.

Outer ear

Captures the sound and amplifies it by funneling it into the smaller auditory cannal

selects the sound in front and to the side, blocking those from behind.

Tympanic Membrane (eardrum) - collects vibrations and transmits them to ossicles

Ossicles - three tiny bones (Malleus, Incus, and Stapes--Hammer, Anvil, and Stirrup) that transfer vibrations to the cochlea

Cochlea - Divided into three parts

-Vestibular Canal: Fluid filled, plays roles in balance

-Tympanic Canal:

-Chochlear Canal:

Organ of Corti - Sound analizer

-Rests on the Basilar membrane

-Consists of four rows of hair cells and the tectorial membrane above the hair cells

-Inner hair cells, provide the majority of information about auditory stimulus

-Lengthening and shortening of outer hair cells against the tectorial membrane adjusts the Organ of Corti's rigidity --This amplifies weak signals and provides adjustable frequency selectivity

-formed by neurons from the auditory (8th) cranial nerves

-auditory cortex is topographically organized

The auditory "where" system

From Auditory cortex (Sound) to parietal lobes (Spatial) and to frontal lobes (Movement of eyes)

Auditory "what" system

From temporal (sound) to frontal lobes (organization) - ID's sounds

Sorting out meaningful sounds embedded in confusing background sounds.

- Voices are ID'd in Superior Temporal Area

- Environmental sounds are ID'd in Posterier Temporal Area (and some Frontal Lobe)

Difference in Intensity

Difference in Time of Arrival - Is the most studied circut, contains coincidence detectors (fires most when input from both ears at the same time; thus, each detector is specialized for sounds arriving at a particular angle)

Difference in Phase of Wave

 - The Skin senses (Conditions at the surface of the body)

- Proprioception (Limb and body position and movement)

- Introceptive system (Sensations in our internal organs

The Skin Senses - What are they and what structures contribute to them?

Touch, Warmth, Cold, and Pain

Two Types of Receptors

-Free Nerve Endings: Processes at the end of neurons, detect warm, cold, and pain

-encapsulated receptors: Complex structures enclosed in a membrane and responsbile for touch

The Vestibular Organs are found in the: Inner ear, are the semicircular canals, utricle, and saccule

Sends projections to the cerebellum and Brain Stem

Parieto-insular-Vestibular-cortex: pathway to cortical area probably the site for dizziness and nausea.