Unit 2 Neurobiology Neurons Brain Body Systems Neuroscience

Unit 2: Neurobiology Neurons, Brain, Body Systems

Neuroscience n How does our brain organize and communicate with itself? n How does our brain allow us to remember the lyrics to dozens of our favorite songs? n How do we remember exactly where we were and what we were doing when we heard about 9/11?

Neural Communication n The basic building block of our body’s communication is the neuron n The human brain has approximately 100 Billion neurons that communicate with each other and allow us to learn, remember, feel pain and function as human beings.

Parts of a Neuron

Dendrites n. Bushy, root-like parts of a cell n. Receive messages (Neurotransmitters) from the sending neuron i. e. the receiver

Soma (Cell Body) and Nucleus n Contains nucleus and other life sustaining parts of the cell n In is resting state is -70 charged

Axon n. The extension of a neuron n“The sender” n. When the threshold is met an electrical charge travels down the axon

Myelin Sheath n Fatty covering of the axon – “the insulator” n Speeds up the neural impulses n Deterioration of the myelin sheath causes Multiple Sclerosis

Terminal Branches/Buttons n Branched end of the axon containing the neurotransmitters (the chemical messenger) When the neuron fires, the terminal buttons release the NT into the synapse

Synapse (Synaptic Gap/Cleft) n. Space between the terminal branches of one neuron and the dendrite of another n. The gap is less than one billionth of an inch wide

Neurotransmitter n The chemical messenger contained in terminal branches that enable neurons to communicate n Fit into receptor sites on dendrites like a key to a lock

How Neurons Fire – the process n Neural communication is an electrochemical process. n n n Electricity travels within the cell (down the axon) and the chemical (the neurotransmitter crosses the synapse to travel between cells). Electricity does not jump between neurons. 1. ) In its resting state – the neuron is just hanging out and is at a -70 charge 2. ) If enough + ions cross the cell membrane to change the charge to +50, the neuron has met its threshold and goes into action potential 3. ) electricity travels down the axon 4. ) terminal buttons release the NT 5. ) the NT crosses the synapse and binds to the dendrites of the receiving neuron 6. ) the leftover NT is taken back up by the terminal buttons – known as reuptake

Firing Neurons cont. . . n Once a neuron fires it is in a refractory state and cannot fire again until it pumps the + ions back out of the cell body and returns to a -70 resting state (i. e. it must re-load) n Firing is an “all or none" principle – if you meet the threshold, you fire completely. If you don’t, you don’t. Neural firing takes place in Fractions of a second

Neurotransmitters – the chemical messenger n Dozens of NT in your body – imbalances can cause problems n 1. ) Dopamine – controls movement, alertness, emotion – too much = schizophrenia, too little = Parkinson's n 2. ) Serotonin – affects mood, hunger, sleep, arousal – too little = depression n 3. ) Acetylcholine (Ach) – affects motor movement, learning, and memory – too little = Alzheimer's n 4. ) Endorphins – body’s natural pain killers

The Nervous System / / Central Nervous System / Brain Spinal Chord Peripheral Nervous System / Autonomic Somatic / Sympathetic Parasympathetic

Afferent/Efferent Neurons n Afferent = Sensory Neurons – run from body to brain n Efferent = Motor Neurons – run from brain to body n Ex: I put my left hand on a warm stove. Afferent neurons in my left hand carry the message to the sensory cortex in my right brain. Efferent neurons from the motor cortex in my right brain, sends a message to move my left hand.

Peripheral Nervous System n. Links the central nervous system with all other nerves in the body

Somatic Nervous System n. Controls voluntary muscle movement

Autonomic Nervous System n. Controls autonomic functions of our body (heart, lungs, organs, etc) n. Usually operates on its own Autonomic is Automatic!

Autonomic is divided into…. . n Sympathetic NS: n n Excitatory - arouses us for defensive action Alert system of the body Accelerates heart rate, blood pressure, breathing; slows digestion Makes you alert and ready for action n Parasympathetic NS n n n Calming system Returns body to normal after stress passes Lowers breathing, heart rate, constricts pupils

Reflexes – exception to the rule…. n Message doesn’t go all the way back to the brain n Sensory neurons carry the info to the spine and the spine makes a motor command without the message getting all the way to the brain first n Ex: knee; intense heat or cold

Brain Imaging…. . n 1. ) Accidents and Injuries: n If a part is damaged, we can deduce what it controlled. – Phineus Gage

Brain Imaging n 2. ) Legions: n n Removal or destruction of part of the brain (brain tumor). Deduces functions

Brain Imaging n 3. ) EEG - Detects brain waves

Brain Imaging n 4. ) CAT – Computerized Axial Tomography 3 -D x-ray of brain Shows Structure, not function n

Brain Imaging n 5. ) Magnetic Resonance Imaging – MRI n Uses magnetic fields to measure the density and location of brain material n Structure, not function

Brain Imaging n 6. ) Positron Emission Topography - PET n Lets researchers see what areas of the brain are most active during certain tasks – shows function n Measures how much of a certain chemical are used in different parts of the brain. Uses radioactive glucose

Brain Imaging n 7. ) Functional MRI n Combines the MRI and the PET scan n Shows structure and function

Cerebral Cortex (CC) n It’s what you think of when you picture the brain: the gray, wrinkled surface of the brain n It’s a thin layer of densely packed neurons

Cerebral Cortex n Left Hemisphere n n n Gets messages from and controls the right side of the body Logic Language Verbal Analytical n Right Hemisphere n n Gets messages from and controls the left side of the body Spatial Creative Emotionally intuitive

The Cerebral Cortex n The left and right hemispheres look symmetrical – but they are biologically the “odd couple” serving complementary functions n Complex tasks involve both hemispheres Corpus Callosum - band of fibers Connecting left and right hemispheres Split Brain Surgery – severe corpus callosum – rare treatment for epilepsy

Dateline NBC – Growing Hope – Is Medical Marijuana a Viable Treatment for Epilepsy? n http: //www. nbc. com/dateline/video/dateline- june-72015/2870103? onid=209511#vc 209511=1

4 Lobes of the Brain

Frontal Lobe n Behind the eyes/forehead n Involved in abstract thought, emotional control, rational judgment (Phineus Gage) n Contains The Motor Cortex – sends out motor messages via efferent neurons n Broca’s Area (left frontal) – speech center n

Parietal Lobe n Crown of the head n Contains the Sensory cortex – where afferent/sensory neurons carry information n The more sensitive the body area, the greater surface area assigned on the sensory cortex

Occipital and Temporal Lobes n Occipital – Back of the head Processes vision Temporal – sides of head over ears Processes hearing Wernicke’s Area – left temporal – language comprehension

Other Important Brain Parts…

Three subsections of the brain

Hindbrain

Within the hindbrain… n Hindbrain – consists of the top of the spine and base of brain – critical life functions n Medulla: blood pressure, heart rate, breathing n Pons: just above medulla – critical in facial expressions n Cerebellum: located on the bottom, back side of the brain. Literally means “little brain. ” Critical for balance and fine motor movements.

Midbrain n Just above spine. Very small in humans. n Reticular Formation: n Finger shaped network of neurons – extends throughout hindbrain to midbrain. Controls arousal and ability to focus attention. n Coma when malfunctions

Forebrain n Controls thought and reason n Most studied by psychologists n Much bigger than the midbrain & hindbrain n What makes us humans

Within the forebrain…. . n Thalamus: sensory switchboard – relays all incoming sensory info except smell n Hypothalamus: “pleasure center” – regulates hunger, thirst, and sexual arousal. Also regulates the entire endocrine system via the pituitary gland

Within the forebrain…. n Amygdala: aggression and fear center. (Legion the amygdala in a monkey and he will be passive and docile) n Hippocampus: critical in forming episodic memories. Not fully formed until age 3. Smell is routed through the hippocampus. n Limbic System: the thalamus, hypothalamus, amygdala, and hippocampus all form the limbic system. Deals with aspects of emotion and memory.

Brain Plasticity n The brains ability to re-organize its neural connections after some type of damage, such that one part of the brain can develop the capacity to carry out a function it normally wouldn’t in a healthy brain. n Brain plasticity is inversely correlated with the age. The older you are the less plastic your brain is and the more difficult it is to overcome brain injury.

Genetics n Every human cell has 46 chromosomes in 23 pairs. Genetic material that makes up chromosomes is DNA.

Genetics n Dominant traits over-ride recessive n Genotype – every gene you are a carrier of n Phenotype – what actually manifests in your physical characteristics n Homozygous – having identical alleles for a single trait (BB, bb) n Heterozygous – having two different alleles for a single trait (Bb)

Dominant V. Recessive

Punnett Square

Twins…. n Identical twins come from one fertilized egg that splits and share DNA. n Fraternal twins come two separate eggs fertilized by two separate sperm and are no more genetically similar than normal siblings.

Gender and X linked Disorders n Gender is determined by the 23 rd pair of chromosomes. XX = girl, XY = boy n Female eggs always carry X. Male sperm carry X or Y and determine the gender of the baby. n X-linked disorders are carried on the X chromosome. Women are often the carriers and the disease manifests in their sons. n Muscular Dystrophy, color blindness, hemophilia

X Linked Disorders

Chromosomal Abnormalities n Turner’s Syndrome - Only one single X (girls). Cannot reproduce, short stature, webbed necks, abnormal sexual development n Klinefelters Syndrome – males, extra X (XXY), varied effects – minimal sexual development, extreme introversion, cannot reproduce n Down’s – extra chromosome on 21 st pair. Causes mental retardation.